Troublesome triple.

[Vetus Ossa]

Regarding my previous post…Gearing...again
After reading all of your comments I have decided it’s probably not worth the hassle, but do appreciate your feedback, thank you.

Instead I have decided to sort out one of my triple bikes that has been irking me for a while.
Here are some details.
Two nearly identical bikes, both with Stronglight Impact triple chainsets, Campag medium cage rear mechs, and the Spa recommended 115mm square taper axles. They also both have Campag Racing T front mechs.
One works perfectly. The other is reluctant to shift from the middle chainring to the inner, sometimes it does, sometimes it doesn’t?
On both bikes when the chain is on the inner ring, the lower part of the front mech is VERY close to the seat tube, but not touching, you can just about slide a fag paper in.
So why am I having problems with it?
Am I right in thinking that if I fitted a longer axled bottom bracket, say 118mm or longer, it would make a difference? I appreciate it would only increase the clearance by 1 1\2mm minimum on the 118mm one.
I should mention the bike I am having problems with is a Colnago, and my surfing so far has indicated finding a suitable longer BB is not going to be easy.

Cheers again.

I'll figure out how to do the 'Quote' thing one day.

[Vetus Ossa]

Just found this on the bay "Stronglight JP400 Italian Threaded Bottom Bracket 70mm Sealed Unit" but don't really want to buy if it will not work is I want.
Its 119mm.

[tatanab]

Assuming you have Ergo levers, perhaps the one that does not work very well is very close but not quite over a click and just a tiny bit from the front mech limit screw. Slacken the cable a very small amount, maybe a 1/4 or 1/2 a turn, will allow the movement to complete. Try it, you can always tighten the adjuster again.

[andrew_s]

Re JP400 BB:
It will depend on whether your Colnago has an Italian threaded frame or not - some were, some weren't.
If the BB shell width is 70mm, it's probably Italian; if it's 68mm, it's probably English. You would have to unscrew the fixed cup (gear side) to be absolutely sure - Italian is a standard RH thread, English is left-hand thread.

[keithb]

You say "nearly identical frames" - are the seat tubes the same size on both? If one is, say, a 31.8 and one a 28.6, that could make the difference.

Otherwise, I'd be re-adjusting and inspecting for ring and chain wear very carefully...

[Vetus Ossa]

Both 28.6, both using ergo levers and adjusted properly. The other bike is 9 speed, my problematical one is 10.

[Mr_average]

Your subject heading summed up triples quite nicely! Shifting from middle to inner is always temperamental, so minor differences such as seat tube angle, chainstay angle, chainring sizes and brand, sprocket sizes and even which rear sprocket you’re in when you try to shift down at the front all make a difference. If any of these differ between your two similar setups then they may contribute to why one is better than another. You may need to swap components between the two in order to try and isolate the problem.

In terms of solutions I’d look into the following:
- Making sure the f.mech is freely moving all the way in. Is it sticky or any grit trapped in there?
- Can you move the chainset further out by adding a spacer to the right side of the BB? Even just to prove whether a longer BB might help.
- Perhaps in conjunction with above, add a ‘Dog fang’ chain catcher so that you can set the f.mech to slightly over shift, thereby helping the release from the middle ring but avoiding derailing the chain.

Unfortunately I wasn’t impressed with the 12 months use I got from a JP400 BB. To put it in context, it lasted as long as one chain.

[Vetus Ossa]

Points noted Mr-average, cheers. I have done most of the things you mention, except trying a spacer on the right hand side cup, that certainly sounds like it may be worth trying.
I always use dog fangs on my bikes, its just nasty when the chain jams there isn't it.
Looks like I will be giving the JP400 BB a miss too

[mercalia]

On both bikes when the chain is on the inner ring, the lower part of the front mech is VERY close to the seat tube, but not touching, you can just about slide a fag paper in.

I would have thought that indicates too short a BB? Dont mechs need a little bit of overshoot? seems like you dont have any space to experiment any way.

[pete75]

Points noted Mr-average, cheers. I have done most of the things you mention, except trying a spacer on the right hand side cup, that certainly sounds like it may be worth trying.
I always use dog fangs on my bikes, its just nasty when the chain jams there isn't it.
Looks like I will be giving the JP400 BB a miss too

Been using JP400 BBs for quite a while without problems as have several other people I know. They're actually made by Kinex a specialist bearing company who, amongst other things, make bearings for jet engines and railway rolling stock. http://www.kinex.sk/english/?page=zakladne-informacie

[Vetus Ossa]

Thanks for that Pete. I have just been rooting about in the garage and found some sturmey archer spacers. They appear to be about 1.5mm thick so will try them tomorrow before I do anything else.
I'm not sure that the JP400 BB comes in Italian thread, but will find out.

[fastpedaller]

I have a Spa triple on my Spa tourer, using a Shimano Claris front mech with a 110.5bb. Absolutely no problems. I know that doesn't solve or answer your dilemma (probably adds more confusion)
Just for info though! Hope you sort it out.

[pete75]

BTW Which Stronglight Impact chainsets are you using. There are two types either five armed or four armed with a hidden chainring bolt. I think a 115mm BB is recommended for the fiver and 110mm for the four.

[Vetus Ossa]

Its the five arm pete, as recommend.

[Valbrona]

The other bike is 9 speed, my problematical one is 10.

I have not found the Stronglight Impact Triple to be 10 speed compatible.