Author Topic: There's Something Wrong With My Brompton... (Read 13343 times)

токамак · « **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

Aidan · « **Reply #1 on:** 11 July, 2010, 07:27:52 pm »

Chains a bit..errr.. missing

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

rogerzilla · « **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.

bobb · « **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!

Zipperhead · « **Reply #4 on:** 11 July, 2010, 08:32:01 pm »

And somebody's built the rear wheel with the hub the wrong way around.

Majorbloodnok · « **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.

nuttycyclist · « **Reply #6 on:** 13 July, 2010, 11:02:11 pm »

Quote from: Majorbloodnok 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.

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

токамак · « **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 · « **Reply #8 on:** 14 July, 2010, 03:15:03 pm »

Quote from: nuttycyclist on 13 July, 2010, 11:02:11 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.

токамак · « **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 · « **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.

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.

Aidan · « **Reply #11 on:** 14 July, 2010, 06:42:55 pm »

Quote from: citizen smudge on 14 July, 2010, 03:15:03 pm

Quote from: nuttycyclist on 13 July, 2010, 11:02:11 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

I might wash mine

токамак · « **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...

токамак · « **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).

Quote from: rogerzilla 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.

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.

Wobbly John · « **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).

токамак · « **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 · « **Reply #16 on:** 28 July, 2010, 11:14:12 am »

Standard Brompton sizes nowadays are 44t, 50t and 54t.

токамак · « **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 · « **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.

Charlotte · « **Reply #19 on:** 28 July, 2010, 11:30:23 am »

*resolves to get fettling soon*

токамак · « **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 · « **Reply #21 on:** 28 July, 2010, 11:39:19 am »

Quote from: citoyen 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.

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).

citoyen · « **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.

LittleWheelsandBig · « **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.

clarion · « **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.