Unintended consequences

[timdownieuk]

I recently ditched my two smaller rings on my front triple, changed my cassette for a wider range one, fitted a new bottom bracket to realign the chain, refitted my old TA crank arm and all was good.

https://www.dropbox.com/s/tjx56qe0qjoil ... 2.jpg?dl=0

Well, nearly all. What I hadn't appreciated was how much of a role the front changer plays in stopping the chain from jumping off the chainring. So, it was back into the parts box to dig out the Shimano front changer again and I duly re-fitted it as a "chain keeper". Of course, I'd forgotten that the TA crank arm doesn't have enough outward "sweep" or offset to miss a modern front changer so it was back to the parts box and I dug out the old Campag front changer as originally fitted many years ago. This cleared the crank arm nicely (as in "only just") but I then found that depending on which gear I was in on the back, the chain would rub on one side or the other of the cage.

Back to the parts box and this time I refitted the old friction downtube shifter so that I could tweak the adjustment as required. All this is getting a long way from my original intention of doing away with the front changer altogether for simplicity and aesthetics!

What I could really do with is a small, very short cage chain keeper of some sort fitted in place of the front changer that would not need any adjustment across the gear range. Most MTB stuff just wouldn't look right on the bike.

Has anyone got any suggestions (other that put the triple back on and forget about it)?

Tim

[Brucey]

Paul engineering do a chain keeper. It too might foul a TA crank though.

You may find that

-using an old style chainring (with full height teeth)
- being careful with chain selection
- running a different rear mech

may help stop the chain from unshipping.

If you go with different front mech you can respace the rear of the front mech cage to allow more angle to the chain run before it causes troubles.

Of course the other thing that will help is if you use a stiffer crank/chainring than that, but you don't want to hear that, obviously...

cheers

[barrym]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

[timdownieuk]

Paul engineering do a chain keeper. It too might foul a TA crank though.

You may find that

-using an old style chainring (with full height teeth)
- being careful with chain selection
- running a different rear mech

may help stop the chain from unshipping.

If you go with different front mech you can respace the rear of the front mech cage to allow more angle to the chain run before it causes troubles.

Of course the other thing that will help is if you use a stiffer crank/chainring than that, but you don't want to hear that, obviously...

cheers

The Paul Engineering chain keeper is the kind of thing I'm looking for but preferably in silver and not quite so "heavy duty". It's also darned expensive! What I might do is look for a second hand frond changer that I can discretely "butcher" but hopefully leave not looking butchered. Not sure that this will be possible.

As you surmise, the chain ring and crank are staying, whatever their shortcomings. I think they look pretty.

Tim

[Brucey]

actually an old suntour or campag mech might do the trick; you can fit a longer bolt and spacers in the back of the cage and this allows bigger angles.

cheers

[timdownieuk]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

Hmm, I wonder what's different? It may be that I could do with a longer arm changer but I'm loth to change it as it works very nicely and I'm wary of costs spiralling. I'm running a 1x8 but I don't think that's the problem. It seems to bounce of the top of the chainring in almost any gear, not just the extremes.

Tim

[timdownieuk]

actually an old suntour or campag mech might do the trick; you can fit a longer bolt and spacers in the back of the cage and this allows bigger angles.

cheers

Well that's an idea. Of course I didn't spot that I could have fitted it *without* splitting the chain until after I'd fitted it. I'm not sure it'll stretch wide enough for an 8 speed block but it's certainly worth a shot.

Cheers.

Tim

[barrym]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

Hmm, I wonder what's different? It may be that I could do with a longer arm changer but I'm loth to change it as it works very nicely and I'm wary of costs spiralling. I'm running a 1x8 but I don't think that's the problem. It seems to bounce of the top of the chainring in almost any gear, not just the extremes.

Tim

If you can take your eyes off the road, take a look at the chain as you shift gear. I have noticed that different chains do jump about more. I have as Shimano fitted at the moment and it leaps about alarmingly compared with KMC ones I've had before.

Barry

Edit: the rear cassette is quite wide, 11-34.

[timdownieuk]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

Hmm, I wonder what's different? It may be that I could do with a longer arm changer but I'm loth to change it as it works very nicely and I'm wary of costs spiralling. I'm running a 1x8 but I don't think that's the problem. It seems to bounce of the top of the chainring in almost any gear, not just the extremes.

Tim

If you can take your eyes off the road, take a look at the chain as you shift gear. I have noticed that different chains do jump about more. I have as Shimano fitted at the moment and it leaps about alarmingly compared with KMC ones I've had before.

Barry

Edit: the rear cassette is quite wide, 11-34.

It's a new KMC that's on it now. 11-34 8 speed cassette. I wonder if a 7 speed chain just "sits" better because of its weight?

Tim

[barrym]

I don't think there's any difference between 7 & 8. The ones I use are x8's.

[Brucey]

IIRC shimano IG 7s chains may be a slightly different internal width to HG7s or HG8s chains.

The camber on the sideplates makes a big difference to how well the chain stays on too, and chains vary a lot here. I'd suggest that a SRAM chain might stay on better than a KMC, but a KMC might shift better.

cheers

[CREPELLO]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

Hmm, I wonder what's different?

The teeth are taller.

[barrym]

IIRC shimano IG 7s chains may be a slightly different internal width to HG7s or HG8s chains.

The camber on the sideplates makes a big difference to how well the chain stays on too, and chains vary a lot here. I'd suggest that a SRAM chain might stay on better than a KMC, but a KMC might shift better.

cheers

Interesting. I've always used KMC X8s and got reasonable life from them. I didn't do any research just took what the LBS had, although I do take the blingy nickel plated ones .

However I did by a cheap Shimano off eBay for an experiment and it has worn out very quickly, in fact my bike is in the garage chainless at the moment. Popped up to the LBS today only to find they were shut .

Even though I get good results from the KMCs it makes me think Maybe I'll stick with what works. Sooner I get something hub geared with a bushed 1/8 chain the better, but that's a whole lot of new threads .

[barrym]

I run a 1 x 7 with a Stronglight single chain wheel that has proper teeth and no ramps and is fine. No unshipping.

Barry

Hmm, I wonder what's different?

The teeth are taller.

And I thought it was just me that was 'long in the tooth'

[recordacefromnew]

Long in the tooth or otherwise, techno-freaks (who don't mind using a 9 speed chain if on 5/6/7/8 speed) may want to consider using a narrow/wide ring.