Older Brompton frame hinge clamp bendy, flexy or loose?

[philepo]

Hello
I have bought a fairly well used Brompton from Ebay: a 5 speeder (I really wanted the gears and don't like the 6 speed Heath Robinson setup). I know, £1100 for a new one probably is better value than £500 for a 18 year old one, but if you don;t have £1100 and think the new gears are daft then.... So, I thought that the headstock/stem neck area was flexing a little too much especially when pulling back on the bars, but actually (I filmed the bike side on and could see it) it is bendy at the main frame hinge clamp. Now, is this: hinge pin worn? alloy clamp worn? Not tightening? Tube either side bending? Corrosion or fatigue weakened tubing? Though I was worried that I'd bought one with a frame about to snap, it turns out that the hinge itself does not mate together well and there is a bit of play in the hinge pin. Now, is that hinge pin play important? Well the handlebar stem hinge also has a similar amount of play in it but that hinge clamps up solidly and there is no play once tightened. So I think the main issue is the clamping side of the hinge, not the pin; the face plates of the mating surface that the alloy clamp plate is supposed to compress together is not fully flat or parallel meaning that the hinge has a small gap (I can see a torch light through it). This is the source of the bendy flex when I pull on the handlebars. it is essentially clamped at one single point on the clamp side and retained by a hige with play in it on the other, hence feels bendy (actually I suppose this is just loose play but feels bendy).

Finally(!) my question is is this normal on an older model / has anyone else sorted this? I was thinking: Engineers blue, clamp up, see where high low spots are, file until a good clamping mating surface is achieved and try not to ruin frame in my cackhandedness. or is this something a bike shop could do / has it been seen on here before???? Any comments ideas welcome (apart from buy a new one )

Cheers all

 

[fossyant]

Bike shop. Thats a hell of a lot of cash for an 18 year old £1k bike.

It needs sorting out before it gets worse.

 

[philepo]

Yep, they keep their value unfortunately but not age related. £400 for a dog, £550 for a reasonable one, £700 for a minter is about right I'd say... nothing to do with age as the design hasn't changed much. I'm just unsure if a bike shop would have the skills to do the job, but I'll ask. So,have you got a Brompton and is the main clamp solid?

 

[steveindenmark]

Im wondering what the problem with the new 6 speed gears are. Because mine have been fine for hundreds of kms.

 

[philepo]

Haha, didn't want to get onto that, but: Nothing, they work perfectly, except I don't like the double shifting technique as I only ride the Brompton occasionally so its hard to remember which side and which way is what, eg especially at a busy roundabout!... so I prefer the 5 speed for neatness of design, but each to their own. How's your main frame hinge?

 

[fossyant]

The main hinge should not have play when done up. At best the pivot pin is worn, so start there. If replacing that doesnt work then there could be more serious hinge wear.

 

[philepo]

Like I say, the hinge pin of the stem and the main hinge have about the same amount of play so I don't think I'll start there as that's quite expensive. I've ordered some engineers blue and will see what the faces look like after they've been clamped (i.e. check the mating surfaces). I will report back in case this helps anyone else in x years to come

 

[rogerzilla]

There are oversize pivot pins available but it's a factory or engineering works job - the hinge needs drilling out to suit.

I always change the alu clamp plates on used Bromptons as a precaution.

 

[steveindenmark]

Haha, didn't want to get onto that, but: Nothing, they work perfectly, except I don't like the double shifting technique as I only ride the Brompton occasionally so its hard to remember which side and which way is what, eg especially at a busy roundabout!... so I prefer the 5 speed for neatness of design, but each to their own. How's your main frame hinge?

Its fine.

I got my 6 speed brompton last october and have ridden about 3000km on it. I read about the gear changing before I bought it and that was really confusing. The guy in the shop also explained it and that was even more confusing.

20 minutes of riding and it was a doddle.

Get in touch with SJS Cycles and tell them what you are looking for.

 

[chriscross1966]

The alumnium clamp pieces are a biannual service part on mine, they should be changed at about the same rate as the chain.

 

[graham bowers]

If you suspect wear in the aluminium hinge clamp plate is the cause, swap the ones on the stem and frame over as an experiment.

 

[philepo]

Hello All. Update: The aluminium clamps are original but fine. The problem was that either something has moved, or more likely the hinge wasn't aligned perfectly from new... see pics. I solved the poor clamping and movement of the hinge by: 1 buy engineers blue, 2 scrape or or lightly file paint on each hinge clamping surface, 3 apply engineers blue to one surface, 4 clamp lightly, 5 see where engineers blue has transferred (in my case only one edge was connecting (see pic) so the bottom clamp face wasn;t connected, hence movement in the hing... insistently, if i really tightened the hinge up it would stop moving but that seemed excessive force. So, 6, I gently filed the faces parallel until both faces of the clamps made contact under light clamping pressure (be sure not to overdo this or you'll damage it irreparably, 7, now when I gently tighten the hinge it is rock solid.

In answer to the 6 speed vs 5 speed issue. If you like your 6 speed then fine, but it is such a Heath Robinson solution I from an engineering pov don;t like it. Besides, even though I test rode one and could use the gears just fine, when I came to a busy roundabout I found that if I didn;t know whether I was in 4th or 5th gears, for example, it was very hard to shift then as you have to know exactly what gear you're already in in order to move to the one you want... annoying. So, I much prefer my 5 speed as the lever just goes up for up and down for down... in a logical fashion!