Author Topic: Brompton builder  (Read 3761 times)

Re: Brompton builder
« Reply #25 on: November 06, 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.
Never tell me the odds.

citoyen

  • Cat 6 Racer
Re: Brompton builder
« Reply #26 on: November 06, 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.

whosatthewheel

Re: Brompton builder
« Reply #27 on: November 06, 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?

Kim

  • Timelord
Re: Brompton builder
« Reply #28 on: November 06, 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?
To ride the Windcheetah, first, you must embrace the cantilever...

whosatthewheel

Re: Brompton builder
« Reply #29 on: November 06, 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

Kim

  • Timelord
Re: Brompton builder
« Reply #30 on: November 06, 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.
To ride the Windcheetah, first, you must embrace the cantilever...

whosatthewheel

Re: Brompton builder
« Reply #31 on: November 06, 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.

Kim

  • Timelord
Re: Brompton builder
« Reply #32 on: November 06, 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.
To ride the Windcheetah, first, you must embrace the cantilever...

whosatthewheel

Re: Brompton builder
« Reply #33 on: November 06, 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

Kim

  • Timelord
Re: Brompton builder
« Reply #34 on: November 06, 2018, 01:20:48 pm »
I'm a sit and spin climber, which probably helps.
To ride the Windcheetah, first, you must embrace the cantilever...

quixoticgeek

  • Mostly Harmless
Re: Brompton builder
« Reply #35 on: November 06, 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
--
Beer, bikes, and backpacking
http://b.42q.eu/

Phil W

Re: Brompton builder
« Reply #36 on: November 06, 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.   

whosatthewheel

Re: Brompton builder
« Reply #37 on: November 06, 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?

Kim

  • Timelord
Re: Brompton builder
« Reply #38 on: November 06, 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.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Brompton builder
« Reply #39 on: November 06, 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).


Re: Brompton builder
« Reply #40 on: November 06, 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.
Never tell me the odds.

Kim

  • Timelord
Re: Brompton builder
« Reply #41 on: November 06, 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.
To ride the Windcheetah, first, you must embrace the cantilever...

Phil W

Re: Brompton builder
« Reply #42 on: November 06, 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.

Re: Brompton builder
« Reply #43 on: November 06, 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?

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton builder
« Reply #44 on: November 06, 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.
Wheel meet again, don't know where, don't know when...

whosatthewheel

Re: Brompton builder
« Reply #45 on: November 07, 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

citoyen

  • Cat 6 Racer
Re: Brompton builder
« Reply #46 on: November 07, 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.

Kim

  • Timelord
Re: Brompton builder
« Reply #47 on: November 07, 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.
To ride the Windcheetah, first, you must embrace the cantilever...

whosatthewheel

Re: Brompton builder
« Reply #48 on: November 08, 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

Kim

  • Timelord
Re: Brompton builder
« Reply #49 on: November 08, 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.
To ride the Windcheetah, first, you must embrace the cantilever...