tanguy frame

I am running a campy 10 speed drivetrain and I'm using SRAM Apex bottom bracket, crank and chainrings. I have some spare campy chorus 10 speed rings that I want to use. I am hoping for better compatibility with the chain and smoother pedaling. There is a slight rumble in the system now.

The campy chainrings are on the same BCD as the Apex spider, with the exception of a single bolt hole on the chain rings that is offset by a very small distance away from the center. I can get 4 chainring bolts assembled with a nice fit, only the remaining offset bolt hole is an issue.

The arc of the chainring that bears against the mating arc of the spider arm is also offset and there is a gap at that bolt hole only. The other 4 arcs fit perfectly.

Finally, The pin that prevents the chain from dropping between the crank and the chainring is not aligned with the crank arm.

Pix show bottom view, assembled spider and top view.

I have several alternatives:
1 - file the bolt hole in the spider to elongate it to accommodate the offset bolt hole on the chainring.

2 - file the campy chainring bolt holes to fit the spider (perish the thought!).

3 - find a smaller diameter bolt and fasten the chainring to the spider as is, using the largest diameter bolt that fits the hole.

4 - revert back to the Apex chainrings.

Is there any value in tapping a hole in the crank arm and adding a pin to prevent chain drop between crank and arm? How about tapping that hole in the chainring instead? Is the pin even necessary? I haven't dropped a chain to the outside in 2 years of riding this system.

Thanks in advance for your feedback!

mconlonx

Revert back to Apex chainrings or get a campy crank/bb.

tanguy frame

I was afraid you might say that. Why?

fietsbob

When Campag was trying to get a market segment out of the MTB trade,

they used the same 110 BCD as everyone else.

now, as you found , they chose to make the bolt circle Unique, so not interchangable.
.. common knowledge amongst the Trade, currently..

that you demonstrated .. thanks for the picture .

want premium 7075-T6 chainrings for the thin 11 speed chains, ? T.A..
they make them to the conventonal 5 bolt 110 BCD.

the chain catch pin should be behind the crank arm ,Note, its 180 off ..
since they used a hidden behind the arm 5th bolt design, for their crank..

Not all.. thats just, 4 of the 5.. as you Found Out. ..

You probably should buy the Whole Campag Crankset & BB ,
since now you will have a back-up set of chainrings..

cxwrench

Oh, I dunno...maybe because ​it doesn't fit properly?

leob1

If the BCD was the same, all of the holes would line up, with none being offset, even by a little, tiny bit.

tanguy frame

You guys are so discouraging - I should have waited until Monday!
I set it up with a M8 bolt in the 5th hole and rode around the block. Front derailleur shifting is way smoother, the bike seems to run well in all respects.

What risk do I face if I keep running with it like this?

Kimmo 

If you keep running it like that, chances are you'll damage the chainrings, particularly the small one, because they're not properly supported for 1/5 their circumference. The hole in the spider is also likely to get mashed.

They should be supported not just by a tight-fitting sleeved bolt but also by the ring lands on the spider. I've seen crappy cranksets that didn't do the latter, but you're asking for trouble if you don't at least have the former. Chainrings aren't just clamped in place.

Filing the hole in the crank is a bad idea for three (3) reasons:

1. You'd be elongating the hole in the wrong direction; the bolt applies load towards the BB and you propose leaving a gap under it.

2. It's the chainring that's the more consumable part, mythical Italian heritage or no.

3. And Campy is the oddball here, not SRAM. Modify the rings to fit the SRAM crank and they'll fit other cranks. Modify the crank, and you've butchered a part that could have been good for 50 years.

So if you insist on going ahead, this is how I'd perform this kludge: ditch the overshift pin, it only makes a bad situation slightly less worse, and it's no help now. And if you haven't thrown the chain in two years, your FD seems well-sorted enough for it not to be a concern. Elongate the holes in the chainrings (because it's the only sane way to do this - and look, they aren't even stepped like most chainring bolt holes!)... and if it was me, I'd glue some shims under the short chainring feet.

This worries me:

Have a browse of pardo.net and then get back to us about whether it'd be better to mess with a crank arm or a chainring.

tanguy frame

Thanks Kimmo! I knew I should have waited until Monday!
Elongate the holes in the chainrings to fit the holes in the spider and glue some shims on the spider to fill the gap and support the chainring. Ignore the pin.
I can do that.

tanguy frame

Here's what I did:
I elongated the holes in the spider, not the chain rings. I put a shim between the chainrings and the shoulder on the spider.
Took if for a ride and it is smoother than it has ever been. Really awesome! I think the Apex chainrings were junk, or at least incompatible with the campy chain.

Now after reading Kimmo's post again, I think i need to support the chainring bolts somehow.

Kimmo 

IthaDan 

Hey man, take it up with reality. We're just the messengers.

Gdogpdx

This whole discussion thread makes me cringe...

tanguy frame

Do you think my bike will asplode??? it has no carbon on it at all!!!

fietsbob

another fool separated from their money.

FBinNY 

It's the same old Cinderella story. If the rings fit, go ahead and use them.

OTOH- like the others I suspect they won't fit unless you have old Campy mtb rings. Current toad rings are 135mm, and compact drive is 110mm with one hole moved off the circle.

Fit is all that counts here, so stop reading and try for yourself.

Bob Pringle

FWIW - Campy Veloce compact arms don't have the offset 5th hole, so any 5-hole 110BCD rings will fit them.

Regards,
Bob P.

Kimmo 

I love how this reveals the Italian snobbishness...

You can only mingle with the tifosi in the cheap seats.

tanguy frame

Can someone please tell me what failure mode I can expect? The concern is that I elongated the hole in the spider to accomodate the one offset bolt hole in the chainrings. The chainrings are shimmed against the shoulder in the spider arm, but the chainring bolt is seated on the outside edge of the hole, not the inside edge. Everything is clamped down good and tight, and the ride quality has been outstanding during the initial test rides.

FBinNY 

There's no reason to expect a failure of any kind if you did a decent job modifying the hole to fit. Even if you did a lousy job it shouldn't be an issue.

If I produced after market 110mm rings, I'd make them with one hole ovalized so as to work on both Campy compact, and standard 110mm patterns.

mconlonx

If you are ever thinking of posting here with "There's some mystery squeak/creak I can't track down," the answer is: if you've checked everything else and especially tightened the chainring bolts and it's still making noise, try a different crank.

Translation: it will be fine.

tanguy frame

It took a while, but I finally got the answer I came here looking for.
Hopefully I haven't lost too much credibility on this forum during this discussion!

Thank you everybody, and if I get a mystery squeak, I'll replace the crank and rings before asking for help here!