Yet Another Cycling Forum

General Category => Freewheeling => Folders => Topic started by: whosatthewheel on 05 November, 2018, 11:21:06 am

Title: Brompton builder
Post by: whosatthewheel on 05 November, 2018, 11:21:06 am
I'm lucky enough to be able to wait 12 weeks for one to be built... and I am about to place the order, just waiting for the C2W voucher to be issued

I'm thinking S2E  S type bars, 2 speed, no guards. I could also go 3 speed and guards, like my wife's, but having ridden hers, I find I never use the 3rd gear (and her 2 gear is bigger than the second gear on a 2 speed, 62 inch Vs 56 or so). Mudguards are nice, but me thinks the handful of times I really need them, I can just use her bike  ;D
Given the plan is to get a Brompton so I can carry it on the bus when the weather is foul, it seems a bit pointless to fit mudguards.

Colour wise, I'm thinking full white... I like white, it's classy and it goes well with any future upgrade I might want to do.
Title: Re: Brompton builder
Post by: Kim on 05 November, 2018, 11:56:29 am
White bike with no mudguards.  That's courageous, as they say on Yes Minister.   :D
Title: Re: Brompton builder
Post by: Samuel D on 05 November, 2018, 12:08:39 pm
Three-speeds, like other bicycles, are usually geared too high. I’d set up a 3-speed so that top gear is a comfortable cruising gear on the flat, but they’re usually set up so that 2nd is like that, 3rd is not nearly used enough, and 1st is too high for ideal climbing.

With a Brompton I’d be tempted to go single-speed for lighter weight, better reliability (I’ve heard bad things about some 2-speed hubs), and because I’d hardly ever care about climbing speed while riding it. If you go slow enough you can climb anything with a single-speed. It’s trying to climb quickly at the wrong cadence that is the problem.

I’m not giving you advice on this because I know you’re an experienced cyclist with a good technical understanding. Actually, I’d like to hear why you want a 2-speed.
Title: Re: Brompton builder
Post by: Samuel D on 05 November, 2018, 12:12:23 pm
As for colours, this is what Frank J Urry had to say in 1956 in Salute to Cycling:

“Some time ago I stood on the gallery of Earls Court and saw the colourful display of hundreds of bicycles, and on closer inspection came to the conclusion the trade had done a fine and very attractive job in the decoration of their wares. No wonder the young folk fall for the bright coatings and think little or nothing of the possible appearance of their property after a year of wear and tear – and weather. Colour and plating do not make a bicycle run easily or smoothly, it merely adds attraction to an attractive article and undoubtedly assists in the selling of it. Any maker or dealer will confirm that statement. But, and again I am giving my own opinion, the proof of any make of machine is in the riding, and the colour of its skin adds nothing to its running values. If the tinted bicycle with its attractive panels of paint and plate is to retain its smart appearance, it will involve you, or someone, in frequent cleaning and polishing. By this you will realise that while I admire some of the colour combinations, I prefer all black, preferably rubberised enamel, for the finish of my own machines.

“It lasts in respectability; a simple wipe over restores the major portion of its neatness after a period of winter neglect, and as most bicycles are more neglected than preserved, including mine, and if you prefer simplicity to fashion, then the all black finish is to be recommended.

“I don’t suppose that suggestion will be followed by the younger generation as proven by the insistent desires of my grandchildren.”
Title: Re: Brompton builder
Post by: Kim on 05 November, 2018, 12:14:23 pm
Three-speeds, like other bicycles, are usually geared too high. I’d set up a 3-speed so that top gear is a comfortable cruising gear on the flat, but they’re usually set up so that 2nd is like that, 3rd is not nearly used enough, and 1st is too high for ideal climbing.

I think Bromptons in particular are deliberately geared for muggle cadences.  They do offer smaller chainring options.


Quote
With a Brompton I’d be tempted to go single-speed for lighter weight, better reliability (I’ve heard bad things about some 2-speed hubs), and because I’d hardly ever care about climbing speed while riding it. If you go slow enough you can climb anything with a single-speed. It’s trying to climb quickly at the wrong cadence that is the problem.

I’m not giving you advice on this because I know you’re an experienced cyclist with a good technical understanding. Actually, I’d like to hear why you want a 2-speed.

Hang on, isn't the Brompton 2-speed the same single speed hub with an extra sprocket?  The main argument for two speed is that since you need all the chain tensioner gubbins anyway to facilitate the fold, the weight penalty of the wiggly version, extra cable, sprocket and shifter is negligible.

The disadvantage is that the derailleur is quite good at gunking up, compared to a purely hub-based transmission.  Equally applicable to the 6-speed, and presumably a non-problem if you're the sort of person who cleans their bike.
Title: Re: Brompton builder
Post by: Samuel D on 05 November, 2018, 12:32:12 pm
Hang on, isn't the Brompton 2-speed the same single speed hub with an extra sprocket?

Don’t know. I suppose you do. I tried to find the “S2E” on the Brompton site but only found a tedious bike-builder so gave up. I guessed it had a 2-speed IGH with kick-back shifting, like my mother’s Sachs-hubbed Monark a long time ago. That was a good arrangement because it eliminated the shift cable and its associated problems, but the modern Sturmey-Archer Duomatic doesn’t seem to have a good reputation for reliability.

The main argument for two speed is that since you need all the chain tensioner gubbins anyway to facilitate the fold, the weight penalty of the wiggly version, extra cable, sprocket and shifter is negligible.

I see. Still wonder if it’s worth the minor weight penalty and increased maintenance. On the other hand, adding another gear to a single-speed is worth more than adding a third gear, which is worth more than adding an 11th gear, etc. What’s the opposite of diminishing returns?
Title: Re: Brompton builder
Post by: whosatthewheel on 05 November, 2018, 12:34:12 pm
Maintenance is not an issue. I keep my bikes in good nick

The third gear is something I might need once a year if I take the bicycle to Yorkshire for holiday with my wife... but I am unlikely to miss it for the remaining 364 days. It implies the Sturmy Archer, which is heavy and I will have to carry it two flights of stairs all the time. On balance, easier to push the bike up that steep 15% bend once a year. Besides, my wife will push hers even with the 3rd gear, so I might as well join in.  :thumbsup:

Single speed is too restrictive... it means in essence anything beyond my normal commute becomes problematic. I reckon I can do a long 6% climb on the 56 inch gear, probably not on the 74 inch one.

I see two speed as the best compromise between single and 6 speed.

Gear ratios are

2 speed standard    56.0” 4.47m    74.7” 5.96m
3 speed standard    47.9” 3.82m    63.8” 5.09m    84.9” 6.78m    
3 speed -12%            42.1” 3.36m    56.2” 4.48m    74.7” 5.96m

Title: Re: Brompton builder
Post by: grams on 05 November, 2018, 12:47:03 pm
Maintenance is not an issue. I keep my bikes in good nick

It's a nylon bushing pointing downwards at best 6 inches from the road. It takes very little to gunk it up enough that the return spring can no longer move it far enough to shift, leaving you stuck in low gear.

Of course an occasional single speed is still more useful than a full-time single speed.
Title: Re: Brompton builder
Post by: Kim on 05 November, 2018, 01:01:05 pm
Hang on, isn't the Brompton 2-speed the same single speed hub with an extra sprocket?

Don’t know. I suppose you do. I tried to find the “S2E” on the Brompton site but only found a tedious bike-builder so gave up. I guessed it had a 2-speed IGH with kick-back shifting, like my mother’s Sachs-hubbed Monark a long time ago. That was a good arrangement because it eliminated the shift cable and its associated problems, but the modern Sturmey-Archer Duomatic doesn’t seem to have a good reputation for reliability.

I've seen Kinetics doing custom builds with such a hub:

http://www.kinetics-online.co.uk/folding-bikes/brompton/cableless-brompton/
Title: Re: Brompton builder
Post by: rogerzilla on 05 November, 2018, 03:43:20 pm
If you buy an S2L, converting it to an S2E only requires two parts (cable disc fender to keep the front brake cable off the tyre, and a standalone hook for the LH front axle nut).
Title: Re: Brompton builder
Post by: whosatthewheel on 05 November, 2018, 06:23:44 pm
If you buy an S2L, converting it to an S2E only requires two parts (cable disc fender to keep the front brake cable off the tyre, and a standalone hook for the LH front axle nut).

good point
Title: Re: Brompton builder
Post by: citoyen on 05 November, 2018, 06:59:32 pm
Single speed is too restrictive...

I commuted for years on a singlespeed on a route with a Proper Hill and it was fine but YMMV. I’m not convinced that 2spd is a massive advantage over singlespeed if you’re worried about hills though.

S2L would be my preferred configuration if I were buying a Brompton now. The mudguards are worth having IMO.

Standard gearing is plenty low enough for most uses. The reduced gearing is only required if you have very hilly routes and/or regularly carry lots of luggage.
Title: Re: Brompton builder
Post by: Jurek on 05 November, 2018, 07:07:36 pm
Single speed is too restrictive...

I commuted for years on a singlespeed on a route with a Proper Hill and it was fine but YMMV. I’m not convinced that 2spd is a massive advantage over singlespeed if you’re worried about hills though.

S2L would be my preferred configuration if I were buying a Brompton now. The mudguards are worth having IMO.

Standard gearing is plenty low enough for most uses. The reduced gearing is only required if you have very hilly routes and/or regularly carry lots of luggage.
I cannot argue with any of that.
But my Brompton's most regular usage is getting the Sainos shopping trip up the incline to my house.
Hence the 50T chainring.
It works.
Title: Re: Brompton builder
Post by: citoyen on 05 November, 2018, 07:39:21 pm
There’s the thing - you have to choose your configuration to suit your dominant usage mode.

Let the occasional uses be where you compromise.
Title: Re: Brompton builder
Post by: rogerzilla on 05 November, 2018, 09:49:04 pm
Mine has AM hub internals so it has three usable gears - 52", 60" and 69".  It climbs well as it's 21lb with bar ends and an almost locked-out rear suspension, so it can be hustled up steep hills ok.
Title: Re: Brompton builder
Post by: quixoticgeek on 05 November, 2018, 11:34:29 pm
There are primarily two problems with the Brompton, both problems are lumps of squishy stuff. One is the lump of squishy rubber that forms the suspension block, and other is the squishy bit between pedals and handlebars.

The former, even with the most firm of the offerings from Brompton is not firm enough, unless you are either a) bloody light, b) not carrying much. Stick 100kg of dyke on a brompton, add 10kg of luggage, and even with 16 gears, it wallows about like a pig... You could argue that this use case is actually more a flaw in the 100kg of dyke, rather than the 50g of rubber... but it's something many don't realise. My Brompton has a 1.85m lowest gear, and a 8.18m upper gear. I have had cause to use all of these (65kph down hill on IoM was fun, 5kph up hill, less so...) My preferred gear for pootling around town is the 4.83 (38t front, 20t rear, 5th gear of the 8 on the SA hub), I have no idea what that converts to in archaic measures.

As for the mud guards yes or no. YES! Then you can fit an easy wheel to it, so you can wheel the bloody thing down the train platform, or round the supermarket. Better yet, stick a rack on so it's more stable to push round the shop. Rack + easy wheels is the best upgrade you can make on a Brompton for usability as a town bike.

J
Title: Re: Brompton builder
Post by: Kim on 05 November, 2018, 11:45:26 pm
It's like citoyen said:  If you want a bike that can fold, add all the toys to make it decently usable.  But if you want something that you can pick up and carry, the minimalist weight-weenie approach (and occasional use of either the 24" gear or Rule 5) makes more sense.

(The rack's something of a special case, as although it adds a fair amount of weight, it makes the folded bike a *lot* more manageable if you aren't just going to pick it up and carry it.)
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 06:37:26 am
There’s the thing - you have to choose your configuration to suit your dominant usage mode.

Let the occasional uses be where you compromise.

Indeed... hence 2 gears. I might compromise on mudguards... they might end up being more useful than not and as per above... a couple of cheap upgrades can rid of them altogether if necessary
Title: Re: Brompton builder
Post by: Samuel D on 06 November, 2018, 08:28:46 am
Standard gearing is plenty low enough for most uses. The reduced gearing is only required if you have very hilly routes and/or regularly carry lots of luggage.

But an 85" cruising gear (according to whosatthewheel’s gear table above) is pretty high for a slow bicycle. Does anyone find that more useful than a lower gear for climbing steep hills? I wouldn’t.

The 56" and 75" gears on the 2-speed sound reasonable although I’d probably still prefer a slightly lower cruising gear on a Brompton. When I rode one of these things the rolling resistance felt extreme.
Title: Re: Brompton builder
Post by: Jakob W on 06 November, 2018, 08:30:11 am
IIRC it's quite a bit cheaper to get the mudguards and/or rack as part of the initial build than as aftermarket parts. My use case would be as an all-weather utility bike; obviously the silly-light (<8 kg) modded Bromptons are going to be easier to carry, but once you've committed to guards and a rack I'm not convinced the difference between say 11 and 13 kg makes all that much difference, especially as you only have to carry it up stairs or when folded.
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 09:03:36 am
Standard gearing is plenty low enough for most uses. The reduced gearing is only required if you have very hilly routes and/or regularly carry lots of luggage.

But an 85" cruising gear (according to whosatthewheel’s gear table above) is pretty high for a slow bicycle. Does anyone find that more useful than a lower gear for climbing steep hills? I wouldn’t.

The 56" and 75" gears on the 2-speed sound reasonable although I’d probably still prefer a slightly lower cruising gear on a Brompton. When I rode one of these things the rolling resistance felt extreme.

I wouldn't want to go any lower than 75" as biggest gear... agree on 85", I also find it a bit big, although I managed to keep it for almost all of the commute on my wife's bike, as a bit of a challenge  ;D

https://www.strava.com/activities/1938901881
Title: Re: Brompton builder
Post by: grams on 06 November, 2018, 09:09:01 am
The 56" and 75" gears on the 2-speed sound reasonable although I’d probably still prefer a slightly lower cruising gear on a Brompton. When I rode one of these things the rolling resistance felt extreme.

An unencumbered Brompton is not a slow bike. The Marathons they usually come with aren’t the smoothest, but if you keep them near max pressure (which a lot of people don’t) they roll well enough.

(The highest gear on mine is 106 inches and it gets regular use)
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 09:16:28 am

An unencumbered Brompton is not a slow bike.

Agree... I worked out it's about 1 mph slower than my carbon road bike on a rolling terrain, even less difference on a completely flat terrain
Title: Re: Brompton builder
Post by: rogerzilla on 06 November, 2018, 09:28:12 am
A jubilee clip (or two) around the firm suspension block makes it usefully firmer.
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 09:33:15 am
A jubilee clip (or two) around the firm suspension block makes it usefully firmer.

I find the firm suspension firm enough... I have noticed they no longer offer the soft one
Title: Re: Brompton builder
Post by: rogerzilla on 06 November, 2018, 12:11:02 pm
IIRC it's quite a bit cheaper to get the mudguards and/or rack as part of the initial build than as aftermarket parts.
Agreed, hence my recommendation to get an L-spec which can be converted to an E-spec at minimal cost.  They are nice with no guards but very impractical; you really don't want gritty water between the seatpost and its sleeve (it may not even fold when mucky, without a lot of persuasion and damage) and the rear hinge won't like it much either.  Brompton headsets are not well sealed against spray from below.
Title: Re: Brompton builder
Post by: citoyen on 06 November, 2018, 12:15:30 pm
But an 85" cruising gear (according to whosatthewheel’s gear table above) is pretty high for a slow bicycle. Does anyone find that more useful than a lower gear for climbing steep hills? I wouldn’t.

My response to that is the same as grams - the Brompton is not a slow bike. (Certainly not compared to the Santander hire bikes, which I am forced to use daily at the moment due to my Brompton being dead.  :'( )

In my years of using the Brompton for commuting, I found the 85" top gear useful on many occasions. Again, it comes back to how you use the bike and of course that will vary between individuals so I wouldn't presume to tell anyone else that what suited me would necessarily suit them, but most of my commuting was through flat central London where you have plenty of opportunities to get up quite a head of steam, even on a Brompton. The one regular hill I tackled on the station-home leg of my commute was doable on the standard low gear. The standard middle gear is good for general-purpose use, especially weaving through traffic.

If anything, I tended to find it slightly undergeared, until I fitted a larger chainring.
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 12:25:27 pm


If anything, I tended to find it slightly undergeared, until I fitted a larger chainring.

Did you need a longer chain?
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 12:28:56 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got, and that's including the Reasonably Priced Mountain Bicycle with knobblies, and the ICE trike (which with sturdy touring tyres has very poor rolling, but wins aerodynamically once you get some speed up).  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home.

What the Brompton is good at is climbing (because with the right gearing that's just power vs weight, and the various factors that make Bromptons slow don't have as much effect) and acceleration (which makes it my favourite bike for nipping about in city traffic).  What it's hopeless at is rolling along on the flat for long periods without sapping unreasonable amounts of energy.  But that's fine, because it's a utility bike; either it'll be over in 20 minutes, or you slow down and take it easy.


[1] Is this a brick vs feather thing, maybe?
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 12:47:11 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got, and that's including the Reasonably Priced Mountain Bicycle with knobblies, and the ICE trike (which with sturdy touring tyres has very poor rolling, but wins aerodynamically once you get some speed up).  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home.

I think you've got the wrong position on the bike... as I said, this is no slow commute and probably only one minute off my best time (out of 500 or so attempts)

https://www.strava.com/activities/1938901881
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 12:48:50 pm
Wrong position on the bike goes without saying; it's an upwrong.  But it's significantly harder work than my 700c touringy-hybrid with stodgy 40mm Marathon Duremes.

I suppose I should do some proper roll-down tests.
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 12:51:38 pm
Wrong position on the bike goes without saying; it's an upwrong.

I had to do a few tweaks to get it right...

Extended seatpost to get more leverage, then I flipped the seatpost clamp to give me a more backward position... and it can be improved still as my wife's bike has M bars, which are too high and force me into an "Obree" position if I want to go fast... with S bars it will be easier.
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 01:02:51 pm
S-type with standard seatpost.  Saddle's all the way back without rotating the clamp, which seems about right.  160mm cranks like my other bikes for knee-friendly pedalling efficiency.  Raised the bars by 50mm to take some pressure of the wrists and make the C-bag fit properly, because it's a utility bike and if I wanted to be aero I'd use a recumbent.

I never liked the handling of the M-type.  Too vague.

But I don't think it's a biomechancial problem.  It climbs just fine, it just doesn't roll very well.
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 01:11:14 pm


But I don't think it's a biomechancial problem.  It climbs just fine, it just doesn't roll very well.

I feel the exact opposite... I have no problem pushing 20-22 mph on the flat, but come an incline I can't quite keep the momentum going in the same way I can with the road bike.
Part of the problem is that standing on the pedals is more awkward and I still need to get used to it
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 01:20:48 pm
I'm a sit and spin climber, which probably helps.
Title: Re: Brompton builder
Post by: quixoticgeek on 06 November, 2018, 02:38:54 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got, and that's including the Reasonably Priced Mountain Bicycle with knobblies, and the ICE trike (which with sturdy touring tyres has very poor rolling, but wins aerodynamically once you get some speed up).  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home.

I run 6bar front and back. I did try 8bar on my Schwalbe winter spikes, it was faster, and quieter, but it was like riding on wood.

Quote

What the Brompton is good at is climbing (because with the right gearing that's just power vs weight, and the various factors that make Bromptons slow don't have as much effect) and acceleration (which makes it my favourite bike for nipping about in city traffic).  What it's hopeless at is rolling along on the flat for long periods without sapping unreasonable amounts of energy.  But that's fine, because it's a utility bike; either it'll be over in 20 minutes, or you slow down and take it easy.

Really? Are we riding the same bike? When climbing the suspension block makes the whole bike wallow about, you get up out the saddle and push the pedals, but you're losing loads of energy in making the bike go up and down. Perhaps it's better if you're not 100kg...

To me, where the Brompton really shines is as a city bike. Weaving in and out of traffic, sharp turns, tiny turning circle, and pissing off hipsters by trackstanding next to them. My Brompton isn't as fast for my commute as my main bike, but I can make up time on being able to ride it like I'm in London...

J
Title: Re: Brompton builder
Post by: Phil W on 06 November, 2018, 03:34:46 pm
I took my Brompton up long Alpine passes a year ago.  It did simplify things as I was in the lowest gear fairly early on and then stayed out of the saddle for long periods. So I just had to ride rather than fiddle with gears or other stuff.   
Title: Re: Brompton builder
Post by: whosatthewheel on 06 November, 2018, 04:33:43 pm
I took my Brompton up long Alpine passes a year ago.  It did simplify things as I was in the lowest gear fairly early on and then stayed out of the saddle for long periods. So I just had to ride rather than fiddle with gears or other stuff.

Make sense, what's your small gear?
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 05:17:06 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got, and that's including the Reasonably Priced Mountain Bicycle with knobblies, and the ICE trike (which with sturdy touring tyres has very poor rolling, but wins aerodynamically once you get some speed up).  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home.

I run 6bar front and back. I did try 8bar on my Schwalbe winter spikes, it was faster, and quieter, but it was like riding on wood.

Quote

What the Brompton is good at is climbing (because with the right gearing that's just power vs weight, and the various factors that make Bromptons slow don't have as much effect) and acceleration (which makes it my favourite bike for nipping about in city traffic).  What it's hopeless at is rolling along on the flat for long periods without sapping unreasonable amounts of energy.  But that's fine, because it's a utility bike; either it'll be over in 20 minutes, or you slow down and take it easy.

Really? Are we riding the same bike? When climbing the suspension block makes the whole bike wallow about, you get up out the saddle and push the pedals, but you're losing loads of energy in making the bike go up and down. Perhaps it's better if you're not 100kg...

Yeah, it's as sproingy as a very sproingy thing, and the handling sometimes gets a bit interesting if there isn't some luggage on the front.  But that doesn't seem to affect my climbing speed, which is ultimately lungs vs hill.  I'm not really one for climbing out of the saddle (other than the odd railway bridge) - I spend too much time lying down on the job, where that sort of high-torque-low-cadence stuff lends itself to embarrassing slow-motion falls and/or owmeknee, so my instinct is to stay seated and find a cadence that avoids too much suspension bounce.
Title: Re: Brompton builder
Post by: SA_SA_SA_SA on 06 November, 2018, 05:27:26 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got,.....  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home....
Do you have an SA 8 speed? As it is a hub not renowned for efficiency, I wondered if you noticed a difference between it and the (presumably) 3 speed SA it replaced?

Also, A to B magazine reckon that the Brompton own Brand Kevlar tyres have gone from being almost the fastest  to one of the slowest  (AToB 119 page  11).

Title: Re: Brompton builder
Post by: rogerzilla on 06 November, 2018, 05:30:29 pm
Mine seems to roll along nice and fast, given fine-grained tarmac, but a rolldown test on said fine tarmac against a 700c tourer saw it lose quite badly.   Obviously air resistance is more significant than rolling resistance at cruising speed, and weight matters more than anything uphill.
Title: Re: Brompton builder
Post by: Kim on 06 November, 2018, 05:43:45 pm
All you people who don't think Bromptons are slow need to get some better n+1s or something[1].  Mine's the slowest bike I've got,.....  Brompton Green tyres at 90PSI front 100PSI rear, for those playing along at home....
Do you have an SA 8 speed? As it is a hub not renowned for efficiency, I wondered if you noticed a difference between it and the (presumably) 3 speed SA it replaced?

It replaced a single-speed, so it's hard to comment on its efficiency, other than it being 100% efficient in the bastard-hill-climbing gear.  The hub appears to be competent enough at freewheeling, though, (where the whole bike is distinctly underwhelming at it) so I don't think it's the drivetrain efficiency that's the problem.


Quote
Also, A to B magazine reckon that the Brompton own Brand Kevlar tyres have gone from being almost the fastest  to one of the slowest  (AToB 119 page  11).

Interesting.  IIRC they've stopped doing them entirely now, and are fitting Marathon Racers as the mid-range tyre.  I suppose I'll find out when they need replacing.

I'm also suspicious of the Capreo dynamo hub, but in the absence of another wheel, it's hard to tell how much drag that's actually responsible for.
Title: Re: Brompton builder
Post by: Phil W on 06 November, 2018, 05:47:38 pm
I took my Brompton up long Alpine passes a year ago.  It did simplify things as I was in the lowest gear fairly early on and then stayed out of the saddle for long periods. So I just had to ride rather than fiddle with gears or other stuff.

Make sense, what's your small gear?

Around 48" I think.
Title: Re: Brompton builder
Post by: SA_SA_SA_SA on 06 November, 2018, 08:18:18 pm
...I'm also suspicious of the Capreo dynamo hub, but in the absence of another wheel, it's hard to tell how much drag that's actually responsible for....
Brompton have abandoned the Capreo for the SP as their standard generator-hub, I wonder if thats why?
Title: Re: Brompton builder
Post by: LittleWheelsandBig on 06 November, 2018, 10:31:00 pm
I used an early SA8 in a Moulton for a 300 brevet back in 2005. It was a bit like stirring a porridge bowl, a little bit harder work than seemed necessary.

The SA8 hub steps up through two epicyclics most of the time and three of them in top gear. It isn't a particularly efficient hub gear for losses under power, unlike a three speed hub. How well it runs while coasting is much less important.

My Brommie is a little slower than my other bikes but not by too much. I tend to crouch and grip the barends when wanting to cover ground on a Brommie, so not too dissimilar to my normal riding position. The clamp is behind the seatpost with the saddle slammed back, which gives enough hip angle for the bum muscles to work properly.
Title: Re: Brompton builder
Post by: whosatthewheel on 07 November, 2018, 10:52:55 am
Ok,

so, I am convinced mudguards are a good thing, but I remain to be convinced that I need anything more (or anything less) than 2 gears...

I am inclined to go S2L
Title: Re: Brompton builder
Post by: citoyen on 07 November, 2018, 01:39:28 pm
Ok,

so, I am convinced mudguards are a good thing, but I remain to be convinced that I need anything more (or anything less) than 2 gears...

I am inclined to go S2L

 :thumbsup:

Have you had a test ride on one? I wasn't convinced about the 2-speed option until I actually went for a test ride...

I came *that* close to placing my order as soon as I got back to the shop, but luckily held off for a few days, and in the meantime my circumstances changed which meant I wasn't commuting regularly any more so couldn't justify the purchase... now I'm back to regular commuting, I'm seriously thinking I need to get one.

As for whether or not they're slow bikes, well, I won't be using one for time-trialling any time soon but my experience over years of regular commuting is that I was doing a lot of overtaking of other riders (more than I was being overtaken by). Perhaps the real answer is that there's no such thing as a slow bike, only a slow rider - after all, I even overtake a number of other riders on the Santander bikes and they handle like oil tankers, and have block and tackle gearing.

Currently, I'm riding my clunky old 7spd hybrid to the station at the home end of the commute, and I don't think that's any faster than the Brompton. The MTB is definitely slower than the Brompton.

I did a test of 'fast folders' last year and to be fair, the Brompton (S2L Superlight) was probably the slowest of the four I tried, but not by much. The Airnimal Joey (in drop-bar configuration) was easily the fastest - handles almost like a normal road bike - but it looks weird and folding it is a pretty convoluted process. The Tern Verge X18 (also with drops) is genuinely quick too but really unwieldy when folded. So the Brompton definitely wins out over those two when quick, compact folding is a priority.

My favourite of the four I tried was the Hummingbird. Astonishingly light and really zippy and nimble. Only real downside is that it doesn't have proper mudguard fittings so you have to use clip-ons. When folded, it has a longer, narrower profile than the folded Brompton, so you could squeeze it between seats on trains. If money were no object, I would have no hesitation buying a Hummingbird with the e-assist option - even with the motor, it's sub-10kg.
Title: Re: Brompton builder
Post by: Kim on 07 November, 2018, 03:09:57 pm
As for whether or not they're slow bikes, well, I won't be using one for time-trialling any time soon but my experience over years of regular commuting is that I was doing a lot of overtaking of other riders (more than I was being overtaken by).

In the evening of the second day of the WHPVA championships, I went back to the track and rode the 1-lap time trial route (about 2km) on my Brompton, for SCIENCEStrava shows me doing the relevant segment in 5:03, vs 5:11 for my official attempt on the Red Baron. (I'll ignore the official timings, as the start and stop points were different.)

I'm not sure whether that's down to confidence, acceleration or biomechanics, but suffice to say I didn't swap bikes for the other events...


ETA: Sanity is restored:  I examined the GPX logs more closely, and the start point of the segment was at the wrong end of the home straight for what I rode.  I made a new segment and it gives 3:18 (much closer to the 3:21 recorded by the timing system) on the Baron and 4:48 on the Brompton.  2.09km, 7m climbing.  That's a ~12km/h difference, and not in the Brompton's favour :)


Quote
Perhaps the real answer is that there's no such thing as a slow bike, only a slow rider

I think it's more of a case that riders climb and bikes descend.  Riding on the flat is a mixture of both.
Title: Re: Brompton builder
Post by: whosatthewheel on 08 November, 2018, 08:46:05 am
:thumbsup:

Have you had a test ride on one? I wasn't convinced about the 2-speed option until I actually went for a test ride...



No, but my wife's 84 inch biggest gear is a bit too big and my single speed Non folding bike has a 73 inch gear, so I think 74 will be perfect. The only question is whether I need the small 3rd gear or I can make do with the smallest 56 inch of a 2 speed.

Taking into account everything, including the fact that it's easier to fiw a puncture on a 2 speed than it is on a 3 speed, I cam to the conclusion that 2 speed is the best compromise for me.
There will be a couple of times per year when I will regret that choice, but I will probably regret more often having the 3 speeder
Title: Re: Brompton builder
Post by: Kim on 08 November, 2018, 01:00:55 pm
Taking into account everything, including the fact that it's easier to fiw a puncture on a 2 speed than it is on a 3 speed

That's a fair point.  Rear wheel punctures on Bromptons are always going to be a bit of a faff, but the indicator chain arrangement on the 3-speed hub raises the cold-finger fiddle factor by an order of magnitude.  I didn't appreciate how much simpler the Sturmy 8-speed was (a nipple screwed onto the cable unhooks from the rotating thinger on the hub, like with a Nexus) until I fitted it.

Not that it matters if your default Brompton puncture repair technique involves folding it up and catching a bus/train/taxi and sorting it out when you get home.
Title: Re: Brompton builder
Post by: rogerzilla on 08 November, 2018, 02:12:02 pm
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.
Title: Re: Brompton builder
Post by: whosatthewheel on 08 November, 2018, 02:14:39 pm
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.

Why they didn't use a hanger like "normal bikes"?
Title: Re: Brompton builder
Post by: grams on 08 November, 2018, 02:21:11 pm
The trick is to not put the tensioner arm into the chain until after you’ve bolted it on.

[quote author=whosatthewheel link=topic=110101.msg2340228#msg2340228 date=
Taking into account everything, including the fact that it's easier to fiw a puncture on a 2 speed than it is on a 3 speed, I cam to the conclusion that 2 speed is the best compromise for me.
There will be a couple of times per year when I will regret that choice, but I will probably regret more often having the 3 speeder
[/quote]

The upgrade path from two speed to six speed is fairly straightforward, so worst case scenario you can do that.
Title: Re: Brompton builder
Post by: Kim on 08 November, 2018, 04:40:39 pm
The trick is to not put the tensioner arm into the chain until after you’ve bolted it on.

Seconded.

The other gotcha is not trapping an extra half-link of chain between the sprocket and the jockey wheel, but I assume that's a Kinetics 8-speed specific issue.
Title: Re: Brompton builder
Post by: SoreTween on 11 November, 2018, 09:49:48 am
The SA8 hub steps up through two epicyclics most of the time and three of them in top gear. It isn't a particularly efficient hub gear for losses under power, unlike a three speed hub. How well it runs while coasting is much less important.
I bought a 2 speed always intending to go kinetics 8 in a second year cyclescheme. That's the least wasteful in discarded parts my legs can cope with. This is making me reconsider, having the direct gear at the bottom feels wrong, it would annoy me. SA5 (assuming it fits) or Alfine 8 are back on the table. No rush to decide, changing jobs in the new year which will rule cycle commuting out :-(
Title: Re: Brompton builder
Post by: LittleWheelsandBig on 11 November, 2018, 10:04:49 am
To be fair, the SA8 has a lot of positives. It is lighter and cheaper than every other complex gear hub and it is most efficient when you need every watt to be useful; climbing with no easier gear available. It just isn't a 'performance' hub. A Brompton isn't a performance bike either but it is eminently practical and useful, so they are a good match for some folk.

I'd still be happy enough to use a SA8 (or a Brommie) on a brevet again while understanding that there are easier ways to get round. I ride a trike, tandem or other machines on some brevets because it is more interesting/ fun than just bombing around for the least effort expended.

The Alfine 8 isn't a particularly efficient hub either; driving up and down through sequential epicyclics. It is closer to bombproof and shifts nicely, though heavier and more expensive.
Title: Re: Brompton builder
Post by: Kim on 11 November, 2018, 01:09:39 pm
To be fair, the SA8 has a lot of positives. It is lighter and cheaper than every other complex gear hub and it is most efficient when you need every watt to be useful; climbing with no easier gear available. It just isn't a 'performance' hub. A Brompton isn't a performance bike either but it is eminently practical and useful, so they are a good match for some folk.

+1

I reckon they're well suited to each other.  For me the Brompton is a workhorse for short urban journeys and occasional mobilty aid, which I sometimes do a Bike Ride on (mainly because the foldingness means I can have a bike with me when I otherwise wouldn't).  The SA8 was the most elegant way of giving it the required bottom gear to handle my knee flare-ups, and it does that well.

The unconventional only-gearing-up approach is designed to sidestep the issue of small-wheeled bikes needing awkwardly large chainrings.
Title: Re: Brompton builder
Post by: SoreTween on 11 November, 2018, 03:56:18 pm
The unconventional only-gearing-up approach is designed to sidestep the issue of small-wheeled bikes needing awkwardly large chainrings.
Ah yes, I see.  Thank you both for the education.
Title: Re: Brompton builder
Post by: whosatthewheel on 13 November, 2018, 03:57:15 pm
The Cyclescheme voucher arrived early, so Saturday I went to place my order... S2L  all white...  :thumbsup:

SHould take up to 12 weeks, apparently...  :o
Title: Re: Brompton builder
Post by: LittleWheelsandBig on 14 November, 2018, 09:41:19 am
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.

Why they didn't use a hanger like "normal bikes"?

Because it would make even harder to remove the rear wheel if the chain tensioner is still bolted to the frame. The Brompton has slightly rear-facing dropouts, so that the tyre clears the chainstay bridge as it drops out. The bridge is so close to the tyre because the bridge stabilises the front of the rear mudguard without using a bolt. That rearward movement as the wheel is removed is the wrong direction for the sprocket to clear the top pulley.

I don't understand why people find the chain tensioner to be difficult to deal with. I remove/ fit the chain tensioner from/ to the frame one-handed with the chain correctly running around the pulleys before the tensioner is fitted to the bike. No need to directly touch the chain at all.

All white Bromptons (with blue decals?) used to denote 'demonstrators'. I'm not sure if they were influenced by Moulton's 'works' specials being painted white.