Will my Campag front mech work with a 28 tooth ring?

[Baggy]

My Campag equipped bike has a triple with 30/40/50 and I'd ideally like to fit a smaller inner ring on the front. Does anyone have any idea whether the front mech would cope - or will any front mech work with Campag ergo shifters?

 

[RecordAceFromNew]

The 28T ring's radius will be 4mm smaller than the 30T one, and since one normally doesn't run small front and small back at the same time (which MIGHT cause the chain to drag on the mech's tail), I would expect no issue with the front mech.

Similarly you MIGHT run out of rear mech wrap range dependent on what cassette range and rear mech you have (and assuming you use, for no obvious reason, small front and smallish backs at the same time).

With the above exceptions, imho it will work just fine.

 

[Tim Bennet.]

I run 26/40/50 with a Campag front changer. Works fine.

 

[Baggy]

Thanks both, that sounds promising, hadn't contemplated a 26 tooth, but now I am!

Similarly you MIGHT run out of rear mech wrap range dependent on what cassette range and rear mech you have (and assuming you use, for no obvious reason, small front and smallish backs at the same time).

With the above exceptions, imho it will work just fine.

I avoid running small/small and run 13-29 at the rear with a long cage so it will hopefully cope.

 

[P.H]

I run 26/40/50 with a Campag front changer. Works fine.

I have the same and not surprisingly it works fine as well.


I fitted a Jump Stop at the same time, so it's not possible for the chain to come off onto the BB shell. Something I was a bit paranoid about after seeing the damage a friend had on a shiny new frame with a smaller than normal granny ring.

http://www.jdcycles....rs-_Accessories

 

[Baggy]

Interesting - that looks as if it would stop your chain falling off at all? My bike throws its chain when the chain starts to wear so I have a Dog Fang fitted but the fang just works as a catcher, it doesn't keep the chain on the ring.

 

[P.H]

Interesting - that looks as if it would stop your chain falling off at all? My bike throws its chain when the chain starts to wear so I have a Dog Fang fitted but the fang just works as a catcher, it doesn't keep the chain on the ring.

Yes, I've gone a step further and adjusted the stop to allow it to overshift slightly, worst case scenario is the chain hits the plate and slides onto the ring. It shifts better now than when it had the 30T, though as I fitted the new ring and the jump stop at the same time I don't know which to attribute the improvement to. I keep meaning to fit one to my other derailleur bike, best tenner I've spent in a long time.

 

[TheDoctor]

Put the bike into bottom gear, then measure the vertical gap between the mech and the chain.
Easiest way to measure this is by slotting allen keys under the chain and above the tail end of the mech, like feeler gauges.
Each 2 mm of gap means you can drop the size of the ring by 1T.
I've used a triple with 48/38/24 and that worked OK, but that's Shimano.

 

[Baggy]

A jump stop is now on my shopping list, whether I go for a smaller inner or not!

...and thanks to TheDoctor for the science bit

 

[TheDoctor]

No worries.
The science bit is easy - 1T occupies 12mm of circumference, which is (12/pi) mm of diameter, and hence (6/pi) mm of radius or as near 2mm as makes no difference.
Simples!!!

 

[Baggy]

Just bumping this up as my bike finally now has a shiny new 28T inner. Everything seems to work ok-ish after swapping the ring and not touching anything else, but it's sometimes a bit sticky changing from both middle to small and middle to big, even with levers clicked to their full capacity.

It might wear in a bit (also had a new chain), but is there anything obvious I might be missing?

 

[Baggy]

Gave everything a good workout today, it shifted from small to medium fine each time so that's a problem that didn't need any solving, but was still a bit of a pain from middle to big. I expect I'll learn to live with it, it's less of a pain than it overshifting.

 

[RecordAceFromNew]

Gave everything a good workout today, it shifted from small to medium fine each time so that's a problem that didn't need any solving, but was still a bit of a pain from middle to big. I expect I'll learn to live with it, it's less of a pain than it overshifting.

The small to middle is actually the most challenging shift mechanically. If middle to big is hesitant, there are two things you can check. First is the outer cage clearing the large ring by no more than 2mm looking at it from the drive side? If it is more moving the whole front mech down (without upsetting its parallel alignment with the rings viewed from the top) will help that shift. Secondly is the H limit screw too far in? Generally the outer cage should clear the chain by 1mm when the chain is on large front small back, which is determined by the H screw if there is sufficient cable tension (I would set cable tension based on the mech lined up centred viewed from above on the middle ring).

 

[Baggy]

Thanks, the outer cage looks as if it's set in the right place so I'll have a fiddle with the H screw.

 

[PpPete]

I changed my Campag Race Triple from 30/39/53 to 28/39/53 without any changing issues. Would have tried 26T inner but the chain would have rubbed the bottom of the cage in most gears, and I can be forgetful about which chain ring I'm in...
Changing to 50 outer to permit lowering the mech is a possibility but the cassette is a 13-29 so I'm not keen to lose the 53 front.