Author Topic: Brompton fold - chain touching front brake  (Read 7686 times)

woollypigs

  • Mr Peli
    • woollypigs
Brompton fold - chain touching front brake
« on: 23 February, 2015, 07:11:28 pm »
When un/folding Peli's wee Brompton, the front brake and cables are getting tangled up with the chain.  The Brompton does have the 8sp Kinetics update installed. The chain and the tension spring looks like it is folding just fine and in a straight line.

Couple of questions :

- Is normal for the spokes on the front wheel to touch the bolt on the rear wheel axle, when folded?

- Is it normal that the front brake cable outer, where the outer hits the front brake calliper barrel adjuster, touch and leans on the chain when folded?
Current mood: AARRRGGGGHHHHH !!! #bollockstobrexit

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #1 on: 23 February, 2015, 08:02:22 pm »
On mine (2014 S-type with Kinetics 8-speed kit):

- Is normal for the spokes on the front wheel to touch the bolt on the rear wheel axle, when folded?

Yes.  The Sturmey axle nuts stick out quite a way, and the right side one nestles between the front spokes when folded.  If it ends up wedged against one during the fold, you need to notice and give the wheel a nudge, rather than forcing it and bending the spoke.

If this is a problem, then a conventional nut might allow it to clear the spokes?


Quote
- Is it normal that the front brake cable outer, where the outer hits the front brake caliper barrel adjuster, touch and leans on the chain when folded?

No, the chain's about 15mm from the cable in the 39T chainring[1], and a couple of inches away in the 28T chainring.  The barrel adjuster is at the lever, so nowhere near.

Evidently your brakes are an older version, which may make a difference.  Your chain tensioner may be an older design, too (mine is based on the dérailleur Brompton tensioner, with spacers to adjust for the new chainline, but I've seen photos where the tensioner looked like the single-speed one hacked with a bit of aluminium angle).  Theoretically if my chain were shorter, it would contact the brake cable when folded, but the bike wouldn't then be able to unfold.

I've also modified the cable lengths on mine to allow for a handlebar mod, though the front cable outer downstream of the cable-gatherer is original, so this loop ought to be standard.

Perhaps quixoticgeek or velovoice could provide further enlightenment...



[1] On the standard Sturmey Archer 33T chainset I'd expect the tension to be similar to this, but with the chain resting fractionally lower, on account of the smaller diameter ring.

woollypigs

  • Mr Peli
    • woollypigs
Re: Brompton fold - chain touching front brake
« Reply #2 on: 23 February, 2015, 09:22:07 pm »
Thanks Kim.

Good to know that the spokes do hit the nut.

You are right that they cable is long, I came to that conclusion myself. Peli talks about a zip tie being there once upon a time. This I'm not sure about myself, but I'm not the user. Though it would make sense to have one to pull and hold the cables. So that they don't get tangled up in the fold and chain.

It does look like the calliper and outer cable has rested on the chain for awhile. Because the outer is bent, dirty and worn. Now need to count the cogs, though the chain does look like it is the correct length. How you describe the dérailleur Brompton tensioner, it sounds the one fitted is like yours.
Current mood: AARRRGGGGHHHHH !!! #bollockstobrexit

Re: Brompton fold - chain touching front brake
« Reply #3 on: 24 February, 2015, 10:32:08 am »
With the Kinetics "upgrade", everything touches when you fold the bike. I particularly hate the way the uppermost run of chain rests on the run below it, when the bike is folded.

The Kinetics kit is fraught with problems... and not always the same ones! Here's my story:
http://velovoice.blogspot.co.uk/2014/01/lucy-grows-more-gears.html
My story contains links to several posts on the Pedalistic blog describing the problems he had with his.

In hindsight I wish I'd gone with the kit from Tiller Cycles instead. But hey ho. The way things are going with my work, I may well remove the entire Kinetics kit and revert to singlespeed - we kept the original wheel and all the doodaws.
Rebecca

2013 custom Enigma Etape
2010 Surly Cross Check
1978 Puch Princess mixte
2012 bespoke Brompton S8L

velovoice.blogspot.co.uk/
@velovoice

woollypigs

  • Mr Peli
    • woollypigs
Re: Brompton fold - chain touching front brake
« Reply #4 on: 24 February, 2015, 10:57:07 am »
Thanks velovoice I had a read of yours and Pedalistic blogs and it sounds like it is a Kinetics problem. I need to find a way to shorten/zip-tie the cables out of the way.

The Brompton aka Betty got the bigger chain ring, so the uppermost run of the chain, when folded is 1-2" above the lower chain run. So high that when folded the brake calliper rest on the chain.

Current mood: AARRRGGGGHHHHH !!! #bollockstobrexit

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #5 on: 24 February, 2015, 03:11:55 pm »
With the Kinetics "upgrade", everything touches when you fold the bike. I particularly hate the way the uppermost run of chain rests on the run below it, when the bike is folded.

Mine only does that in the smaller chainring.  I picked the chainring size difference specifically so that although it rests on itself, it's still under enough tension that it doesn't flap about and you can backpedal without anything derailing.  Don't see why it's a problem?

(Accepted that a single ring is going to be slightly smaller than my big ring, so it may still rest on itself due to the angles involved, even with the right chain length.)


ETA: Ah, just looked at your link.  You've got the older style tensioner based on the single-speed version.  There must be a difference in capacity...

(With apologies for the horrific amount of Middle Earth on my drivetrain...)
 
28T ring:


39T ring:

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #6 on: 24 February, 2015, 03:40:55 pm »
Actually, looking at this, and even allowing for the different tensioner design, I think your chain could be a bit shorter:



39T (this is the upper limit for chain tension):


28T (the lower limit for non-slackness when folded):

woollypigs

  • Mr Peli
    • woollypigs
Re: Brompton fold - chain touching front brake
« Reply #7 on: 24 February, 2015, 03:54:17 pm »
Yup Betty the Brompton looks like Kim 39T Brompton
Current mood: AARRRGGGGHHHHH !!! #bollockstobrexit

Kim

  • Timelord
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Re: Brompton fold - chain touching front brake
« Reply #8 on: 24 February, 2015, 04:01:12 pm »
Yup Betty the Brompton looks like Kim 39T Brompton

Except for the brake calipers, presumably.

(Wonder if making the chain slightly longer would help?)

woollypigs

  • Mr Peli
    • woollypigs
Re: Brompton fold - chain touching front brake
« Reply #9 on: 24 February, 2015, 04:11:23 pm »
I was thinking that too, need to dig around to see if I got a link or two laying about.
Current mood: AARRRGGGGHHHHH !!! #bollockstobrexit

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #10 on: 26 February, 2016, 03:23:27 pm »
28T ring:


What parts did you use on the front of the Brompton for this setup?

How many links are in your chain?

Think I'm going to drop to a 28t on the front to give me better hill climbing performance.

Cheers

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #11 on: 26 February, 2016, 03:39:20 pm »
28T ring:


What parts did you use on the front of the Brompton for this setup?

Spa Cycles 160mm XD-2 triple cranks.
Shimano UN55 118mm bottom bracket + 1mm spacer when it wasn't quite long enough to stop the chainring bolts scratching the paint (119mm would probably work without a spacer).
28T 74mm BCD stainless chainring of unknown origin from my spares box.
39T 110BCD alloy chainring from Torslanda OTP.
42T 110BCD Stronglight chainguard.
XD2-compatible chainring bolts from Spa.
Wellgo QRD-W01 quick-release pedals.
Scotchlite tape.


Quote
How many links are in your chain?

No idea.  I did trial and error on a worn out chain from another bike, then shortened the Brompton chain to match.

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #12 on: 28 February, 2016, 03:36:51 am »


Spa Cycles 160mm XD-2 triple cranks.
Shimano UN55 118mm bottom bracket + 1mm spacer when it wasn't quite long enough to stop the chainring bolts scratching the paint (119mm would probably work without a spacer).

What bottom bracket did you have on the Brompton before your upgrade? googling suggests that pre 2013 they used a FAG 119mm bottom bracket, and way back in the mists of time a 122mm one. My brompton dates from 2007 and the sturmey archer crankset that came with the kinetics set fit just fine. Any idea what bottttom bracket I have on my Brompton?

Cheers

J


--
Beer, bikes, and backpacking
http://b.42q.eu/

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #13 on: 28 February, 2016, 03:55:48 am »
Scratch that, think I've worked out what's going on. Pre 2013 Brompton used a bb with an ISO taper, now they use a JIS taper, which means I need to swap bottom brackets, and far more annoyingly, need one tool to remove the existing bb, and a different tool to fit the new one. Ah, gotta love standards, so many to choose from...

Cheers

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #14 on: 28 February, 2016, 01:52:29 pm »


Spa Cycles 160mm XD-2 triple cranks.
Shimano UN55 118mm bottom bracket + 1mm spacer when it wasn't quite long enough to stop the chainring bolts scratching the paint (119mm would probably work without a spacer).

What bottom bracket did you have on the Brompton before your upgrade?

The newer 119mm JIS one (it's a 2014 Brompton).  Except I replaced that with a 113mm UN55 in order to work with the XD2 compact double (which it did, for reference), and sold it off (along with the original crankset, tensioner and other spare parts) before I decided that 33T wasn't small enough and had to swap to the triple to get a smaller ring.  I expect the original 119mm bottom bracket would have worked fine if I'd still had it.

Fortunately, this all involved the one tool that I had already.


AIUI you can successfully mate JIS cranks with an ISO BB, but it does something weird to the chainline.

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #15 on: 28 February, 2016, 02:03:49 pm »
The newer 119mm JIS one (it's a 2014 Brompton).  Except I replaced that with a 113mm UN55 in order to work with the XD2 compact double (which it did, for reference), and sold it off (along with the original crankset, tensioner and other spare parts) before I decided that 33T wasn't small enough and had to swap to the triple to get a smaller ring.  I expect the original 119mm bottom bracket would have worked fine if I'd still had it.

Fortunately, this all involved the one tool that I had already.

I love the way that everything in cycling has been standardised, and for each part that has been standardised, there are so many standards to choose from...

Quote

AIUI you can successfully mate JIS cranks with an ISO BB, but it does something weird to the chainline.

According to Sheldon, it puts it 4.5mm out. I think for the sake of a bottom bracket, tub of anti seize, and 2 tools, I'll just replace it.

Cheers for your help.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Kim

  • Timelord
    • Fediverse
Re: Brompton fold - chain touching front brake
« Reply #16 on: 28 February, 2016, 02:39:15 pm »
I love the way that everything in cycling has been standardised, and for each part that has been standardised, there are so many standards to choose from...

Yup.  I've now got an exciting new Hollowtech BB (different tool again) on the mountain bike.  :facepalm:

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #17 on: 07 June, 2016, 07:18:56 pm »
Spa Cycles 160mm XD-2 triple cranks.

So having got the Brompton to bits so that I could do this upgrade, I tried the folding pedal on the spa cycle crank. Slight issue, the end of the crank is so thick it doesn't allow the pedal to fold... Arse.

Not a problem thought I, I can put the old Sturmey archer crank back on. Hah, no such luck. The hole for the bottom bracket spindle is 45° out compared to the spa cycle crank so it doesn't work. Nice try.

So I now either need to go with the spa cycles crank, and accept that I can't fold the pedal anymore, or, find an alternative crank. Bah.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Brompton fold - chain touching front brake
« Reply #18 on: 08 June, 2016, 12:37:31 am »
How much material would you have to file off the crank arm in order to allow the pedal to fold? Probably only a tiny amount.

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #19 on: 08 June, 2016, 12:26:07 pm »
How much material would you have to file off the crank arm in order to allow the pedal to fold? Probably only a tiny amount.
Actually quite a substantial amount, nearly 50% of it's thickness. It'll be easier to spend the 15 quid on a Brompton left crank...

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Brompton fold - chain touching front brake
« Reply #20 on: 08 June, 2016, 02:00:06 pm »
That seems excessive.. it's only the outer edge that the pedal has to clear. I've used Shimano cranks and found the brompton pedal just clears them.

Are you installing it with the washer?

quixoticgeek

  • Mostly Harmless
Re: Brompton fold - chain touching front brake
« Reply #21 on: 08 June, 2016, 02:27:37 pm »
That seems excessive.. it's only the outer edge that the pedal has to clear. I've used Shimano cranks and found the brompton pedal just clears them.

Are you installing it with the washer?

It's quite a thick crank, and yes the washer is needed other wise the pedal doesn't turn.

I've ordered a Brompton Left crank, should fix the problem.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

rogerzilla

  • When n+1 gets out of hand
Re: Brompton fold - chain touching front brake
« Reply #22 on: 08 June, 2016, 07:26:25 pm »
...is what I did on the M-type with a folding pedal.  Thankfully the square taper is the same way around on both the XD2 and the Brompton crank,

On the S-type, I use SPDs so it's not an issue.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.