Brompton Transmission Problem

[StuartG]

I was riding up to Colchester today on my M3L. Up the hill into Brentwood something nasty happened. It felt as if the chain was slipping but it wasn't. I assume the issue was inside the hub. It didn't matter which gear it was in - just if it was under pressure.

I walked the hill and got on at the top. There is then a long downhill and only a small slope. I pressed gingerly on. When I did get to the next decent incline I got up ok. The problem seems to have resolved itself and the next 40 miles were ok.

I plan to ride back to London tomorrow but should I panic, worry a bit or just forget it? What do you think went wrong and is there a cure?

 

[srw]

Could be the gears being slightly out of alignment - try adjusting the timing chain a smidge.

 

[StuartG]

Could be the gears being slightly out of alignment - try adjusting the timing chain a smidge.

The timing chain? I am only aware of the gear change chain - which I did tighten and slack to no effect.

 

[Lacypaperdevil]

The timing chain? I am only aware of the gear change chain - which I did tighten and slack to no effect.

No matter what you call it is sounds like the hub is slightly out of alignment (happened on mine too as you described when the hub was under pressure).

On the end of the chain their is a rod that goes into the hub. On this rod there will be a marker (one mine it's blue) this needs to be in the centre of the hole of the hub nut.

 

[annedonnelly]

Not sure there's a marker - maybe that's on older/different models. The online instructions I saw was that the end of the rod should be visible by (I think) 1 mm. It's onn the brompton website.

 

[srw]

@StuartG - yes, a timing chain is something different, isn't it?

 

[Blue Hills]

If it was in all gears, the last time that happened to my brompton was when I changed the chain but kept the old cog - so the chain slipped. Cured by changing the cog. But you say it isn't that.

Next, as folks say (though you probably know this) check the gear adjuster chain - "timing chain" sounds like something you'd have if the bike had spark plugs.

I must say I like Bromptons a lot for not having a policy of continuous improvement/fiddling but I do wish they'd improve the system for checking when you have proper adjustment - that thing with the coloured line (just showing or half-in/half out according to who you listen to) is a right old bodge. I know they don't make the gearing but they could surely fashion something to make better use of that coloured mark.

If all fails/gets you nowhere I'd take it to Bicycle Workshop in Notting Hill.

They can have a long waiting list (Saturdays a different system I think) but they are very good.

 

[srw]

A timing chain is something a tandem has. Don't ask me why it's called that.

 

[StuartG]

The good news is that the next 90 odd miles there and back went without a hitch including a severe test on the gears, hub, chain and me on that extremely stiff climb back into Maldon - I passed a sporty guy walking it - maybe he had gear issues

Hence the problem appears to have cured itself. I was thinking that the cog (or whatever its called) that locks the freewheel when pedalling wasn't quite clicking into place causing a slip and the long downhill freewheel after the issue sort of freed it up. Old SA hubs had an oil cap and bunging in a load of Castrol cured all known problems in the works. Do I presume it is all sealed now?

I will check out that marker thing which I was unaware of. I have a 2006 model so what's true now might not have been true then.

 

[Beemer]

Correct adjustment is in the manual.
"1 mm (of the solid rod) sticking out when you look through the view hole in middle gear"
It should NOT be in the middle of the hole!
Ian

 

[Blue Hills]

I don't have any hole beemer - mine is a 5 speed circa about 2000.

Your description does though support my view that the adjustment is a dark art/right pig's ear.

How long have you had the bike Stuart if you were unaware of the adjustment rod marking?

 

[StuartG]

How long have you had the bike Stuart if you were unaware of the adjustment rod marking?

Only 8 years ... but the incident evidence would appear to point to a transient fault rather than an adjustment issue.

 

[Brommyboy]

The 5-speed SA gear is set with the coloured marker just exposed from the AXLE END, while in 2nd gear. It pays to rotate the wheel backwards after putting in gear, to ensure that the internals have also selected the proper gear. The hole is merely for viewing!

 

[Blue Hills]

Thanks for the reply brommyboy.

Yes, I know that it's the axle end that is the key thing with this 5-speed gear.

In your view is "just exposed" synonymous with "half in-half-out"?

As you maybe remember I was having big slippage issues with this a while ago - Bicycle Workshop sorted it but now and again I do still get slippages in third gear. I am making every effort to do the back-pedalling thing and am also keeping a close eye on the adjustment. All generally good and am enjoying becoming acquainted with the bike again after its fairly extensive lay-up.

I do still feel that a better adjustment system should have been sorted by now.

many thanks again.

 

[Brommyboy]

I used to have the full colour showing outside of the axle end, maybe half a millimetre out. The 5-speed needs to be exactly set and kept like that as there is little latitude in its setting. Three speed gears do not have to be so exactly set.