Author Topic: There's Something Wrong With My Brompton...  (Read 13670 times)

There's Something Wrong With My Brompton...
« on: 11 July, 2010, 07:20:00 pm »
...and I think I know what it is.



It's in a right state and needs to be pimped ahead of the Brompton World Champs. It was more rusty than Mars when I pulled it out of the shed...

It will ride again. Hopefully ;)

Re: There's Something Wrong With My Brompton...
« Reply #1 on: 11 July, 2010, 07:27:52 pm »
Chains a bit..errr.. missing ;D







( and why is everyone pimping their Brommies for the BWC?, mines staying bog standard)

rogerzilla

  • When n+1 gets out of hand
Re: There's Something Wrong With My Brompton...
« Reply #2 on: 11 July, 2010, 07:28:13 pm »
What's your highest gear?  More than 80" is useful.  The 2-speeds spin out well before the 3-speeds because the 12T sprocket doesn't beat the 13T sprocket AND the 33% (or 15.5% in my case) increase available from the hub internals.  All Bromptons are well undergeared for racing.

A 54T ring is very useful in all cases.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: There's Something Wrong With My Brompton...
« Reply #3 on: 11 July, 2010, 07:29:25 pm »
I think the main problem is that it appears that several major components aren't actually attached to the bike!  :P
Those wonderful norks are never far from my thoughts, oh yeah!

Zipperhead

  • The cyclist formerly known as Big Helga
Re: There's Something Wrong With My Brompton...
« Reply #4 on: 11 July, 2010, 08:32:01 pm »
And somebody's built the rear wheel with the hub the wrong way around.
Won't somebody think of the hamsters!

Majorbloodnok

  • its no good, we'll have to drink our way out of it
Re: There's Something Wrong With My Brompton...
« Reply #5 on: 13 July, 2010, 04:13:57 pm »
Ah, I've finally got it!  The seat, you have no seat!  Phew, been studying that picture for days now.


Re: There's Something Wrong With My Brompton...
« Reply #6 on: 13 July, 2010, 11:02:11 pm »
Ah, I've finally got it!  The seat, you have no seat!  Phew, been studying that picture for days now.



Silly boy.  It's the gear cable that's missing.

Re: There's Something Wrong With My Brompton...
« Reply #7 on: 14 July, 2010, 03:03:38 pm »
All cables need replacing, the seat post needs going over with metal polish, the hinges need oiling and the wheels need cleaning! I'm hoping I won't need to touch the bottom bracket or headset or 3 speed hub gear.

The saddle is indeed missing - it had a Brooks which I swiped a couple of years ago for my Raleigh Randonneur. I'll put something a bit sporty on it for the World Champs. Mudguards are out, tyres will be exchanged for something fast like Schawalbe Kojaks, and I might even try a larger chain ring for MORE POWER!

Once it's going again I'll then need to perfect a racing position - something like this might work ;)


citoyen

  • Occasionally rides a bike
Re: There's Something Wrong With My Brompton...
« Reply #8 on: 14 July, 2010, 03:15:03 pm »
It's the gear cable that's missing.

The gear cable is there - the real problem is that it isn't attached to the hub.

Aidan - I'm not "pimping" my Brommie per se, but it does require some vital maintenance/repair work doing to it before the BWC. Though perhaps not quite as much as Tokamak's.

d.
"The future's all yours, you lousy bicycles."

Re: There's Something Wrong With My Brompton...
« Reply #9 on: 14 July, 2010, 03:45:27 pm »
Clearly mine needs some attention! It's not been in a rideable state for some time, and so whilst I'm seeing to it I thought may as well pimp the thing and give it a more racey spec. 

If it was good to go, I probably wouldn't bother doing anything with it.

citoyen

  • Occasionally rides a bike
Re: There's Something Wrong With My Brompton...
« Reply #10 on: 14 July, 2010, 04:21:09 pm »
Actually, I tell a lie - I am doing some pimping: replacing the decidely non-sporty M+ tyres with slicks for the event, and probably swapping the "M" bars for flat bars - though I don't intend to change the stem, so I could end up with a very sporty riding position.  :o

There are several other improvements I'd like to make if I had the money (eg could do with some better brake levers), but mostly I'll make do with it as it is. The bike is a workhorse, after all, not a show pony. ;)

d.
"The future's all yours, you lousy bicycles."

Re: There's Something Wrong With My Brompton...
« Reply #11 on: 14 July, 2010, 06:42:55 pm »
It's the gear cable that's missing.


Aidan - I'm not "pimping" my Brommie per se, but it does require some vital maintenance/repair work doing to it before the BWC. Though perhaps not quite as much as Tokamak's.

d.


Ok, let you off ;D   I might wash mine :thumbsup:

Re: There's Something Wrong With My Brompton...
« Reply #12 on: 27 July, 2010, 01:11:33 pm »
So I'm slowly making some progress. Wheels cleaned up good - and I can assure you that they took some serious cleaning! Probably something like three years worth of grime dried on solid after a year in the shed.



What I have there is a 3 speed SRAM (Sachs) hub, with 13/15 sprocket combo. They feel quite heavy to me given the small size, but I guess they're pretty solid. Not exactly racing wheels, but they will do me. I have a set of Schwalbe Kojak's on order. The next item on the agenda is the chainring. If it isn't 54T, it will be soon...

Re: There's Something Wrong With My Brompton...
« Reply #13 on: 28 July, 2010, 10:59:07 am »
It's a 50T chainring. And looking at the price of Brompton parts I'm more reluctant now to change it (would require new chain also).

What's your highest gear?  More than 80" is useful.  The 2-speeds spin out well before the 3-speeds because the 12T sprocket doesn't beat the 13T sprocket AND the 33% (or 15.5% in my case) increase available from the hub internals.  All Bromptons are well undergeared for racing.

A 54T ring is very useful in all cases.


Using Sheldon's gear calculator, 50 x 13 on 35-349 wheels comes out with 61.8", which +33% = 83.19" if my logic is correct?

I think I'll stick that for the time being. I'll give the bike a thrash when it's all back together (been a while since I've ridden it) and then see if I feel like I need more top end for the BWC.

Re: There's Something Wrong With My Brompton...
« Reply #14 on: 28 July, 2010, 11:07:05 am »
I think I've got a 52T Brompton crank & chaining in the shed, if that's any help (It was aCycle-jumble purchase).
If it ain't broke, fix it 'til it is...

Re: There's Something Wrong With My Brompton...
« Reply #15 on: 28 July, 2010, 11:13:25 am »
If it's surplus to requirement WJ, then I could definitely use it, thanks (PM me a price if you like). Might require the 102 link chain though...

LittleWheelsandBig

  • Whimsy Rider
Re: There's Something Wrong With My Brompton...
« Reply #16 on: 28 July, 2010, 11:14:12 am »
Standard Brompton sizes nowadays are 44t, 50t and 54t.
Wheel meet again, don't know where, don't know when...

Re: There's Something Wrong With My Brompton...
« Reply #17 on: 28 July, 2010, 11:16:12 am »
Yup, and the manual says 100 link for 50t and 102 for 54. I suppose I could remove a link for a 52?

citoyen

  • Occasionally rides a bike
Re: There's Something Wrong With My Brompton...
« Reply #18 on: 28 July, 2010, 11:27:13 am »
Singlespeed + 54t chainring + 13t sprocket + Marathon Plus = 66.8" = slightly over-geared for general use.

But it's only a problem when trying to pull away from the lights quickly or honk up steep hills. It's fine for cruising. It'll probably be just right for the BWC - assuming the one small hill isn't all that steep.

I had to add an extra two links when I changed the chainring from the original 50t, so one link difference for a 52t sounds right to me.

d.
"The future's all yours, you lousy bicycles."

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: There's Something Wrong With My Brompton...
« Reply #19 on: 28 July, 2010, 11:30:23 am »
*resolves to get fettling soon*
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

Re: There's Something Wrong With My Brompton...
« Reply #20 on: 28 July, 2010, 11:32:36 am »
I need to give myself plenty of time, in the event that I fail to put it all back together in working order!

clarion

  • Tyke
Re: There's Something Wrong With My Brompton...
« Reply #21 on: 28 July, 2010, 11:39:19 am »
Singlespeed + 54t chainring + 13t sprocket + Marathon Plus = 66.8" = slightly over-geared for general use.

But it's only a problem when trying to pull away from the lights quickly or honk up steep hills. It's fine for cruising. It'll probably be just right for the BWC - assuming the one small hill isn't all that steep.

I had to add an extra two links when I changed the chainring from the original 50t, so one link difference for a 52t sounds right to me.

d.


Disagree.  I ride 66.6" fixed and I'm quite a spinner.  It's perfectly adequate for most duties (though the road up past Streatham Common is challenging).
Getting there...

citoyen

  • Occasionally rides a bike
Re: There's Something Wrong With My Brompton...
« Reply #22 on: 28 July, 2010, 12:19:13 pm »
Hmm. Is that on your Ridgeback? I wonder if the small wheels and upright riding position of the Brommie make a difference to how it feels, because you're right - 66.8" doesn't sound like a particularly high gear.

d.
"The future's all yours, you lousy bicycles."

LittleWheelsandBig

  • Whimsy Rider
Re: There's Something Wrong With My Brompton...
« Reply #23 on: 28 July, 2010, 01:15:58 pm »
Don't forget there is a difference between nominal and actual wheel size.  A Brompton wheel is comparatively a lot closer to 16" diameter than a narrow 700C wheel is close to 27" diameter.
Wheel meet again, don't know where, don't know when...

clarion

  • Tyke
Re: There's Something Wrong With My Brompton...
« Reply #24 on: 28 July, 2010, 02:46:49 pm »
How does that come into it?  I use Sheldon's calculator, which allows for different wheel/tyre sizes.

But I take Citoyen's point about the different position and feel of a Brommie.
Getting there...