Campy upgrade 8sp to 10sp ... chain keeps falling off

[EatsFats]

I had 8sp Campy Veloce. Decided (rather unwisely as it turns out) to upgrade brakes. Eventually ended up with new shifters, chain, derailleurs, wheels ....

Just for others reference:
- 10sp Veloce Ultrashift levers do not work with old 8sp Veloce rear mechanicals The spacing is such that every 4-5 shifts, you're off by an entire cog. Simple tricks such as winding the cable around the outside of the clamp helps, but not enough.
- The 10sp shifters do not work with new 10 speed cassette + old 8sp Veloce rear derailleur. It works over a portion of the range, but I guess they never anticipated having the 8sp move over the range of the 10sp cassette. You will need a new 10sp rear derailleur.

Now everything is in place (front + rear derailleur, new 10sp chain), on the workstand it works perfectly. First easy km on the road works fine. Here is the problem: Any time under sprint power, the chain slips from the big ring down to the small ring.
The facts:
- I'm outta shape right now, not that powerful, and this is the same bike I've ridden for years @ 8sp and it has never done this.
- The front rings are TA Horus 50/39, only several thousand km at most, and I believe meant originally for 9/10sp Campy. I did not install any spacers when I was running 8sp
- The crankset is still the old 8sp Veloce one
- Chain is 10sp KMC, brand new, of course
- Front derailleur is brand new Campy Veloce braze-on mount. Shifts fine, and yes, I'm fairly certain I've set the gaps to the chainrings correctly (the new derailleur comes with a sticker & measurements, dummy proof).

Any ideas what is going on? The only thing I might think of is when I was running 8sp chains on this thing, it sits a little loose or shifts a little funny since I didn't have the extra spacers so that now it is a bit worn out so the new chain doesn't "fit" right and slips off??? I dunno... I'm open to any crazy ideas.

 

[Fiemme]

Can't understand why you could not use the 8speed derailleur. I've been using an 8speed shimano 105 derailleur with a 10speed campag cassette and shifter for over 18months with no problem.

As for the chain dropping to the small ring under extreme (Sprinting) load, it could be an alignment issue. I'm guessing your frame is either steel or aluminium, I would also check for cracks/fatigue in the bottom bracket area. Also check to see if the bottom bracket is secured correctly.

 

[EatsFats]

The old 8sp was missing quite a few bits, so it was held together with odd screws & bolts. It was time to pay it some attention...

Anyway, more to the point, this was a perfectly functioning bike at 8sp, after the switch, not so hot. So I'm ruling out the suggestions such as cracks, fatigue, loose BB, etc. It was a daily ride for the longest time and I didn't mess with the BB. It's not like the bike was sitting in the garage for years and I pulled it out and dusted it off. The bike shouldn't have any alignment issues, never been crashed, squished, bent or otherwise abused.

I did get a suggestion that perhaps I now have an odd chainline due to the switch to 10sp. I will double check that, but it wasn't obviously the case when it was on the workstand. (Nor when I'm riding and looking down on my chain)

Another odd thing, I never noticed the chain rubbing my front derailleur prior to it dropping off.

 

[Fiemme]

Check the front derailleur hanger it may be cracked.

 

[Master50]

You say you got the front derrallieur height correct but over the years i have found most FD problems related to FD alignment to the rings although you say the FD never rubbed the chain. Even a few MM of the wrong tail in or out has caused FD troubles for me.

 

[Bustedknuckle]

I had 8sp Campy Veloce. Decided (rather unwisely as it turns out) to upgrade brakes. Eventually ended up with new shifters, chain, derailleurs, wheels ....

Just for others reference:
- 10sp Veloce Ultrashift levers do not work with old 8sp Veloce rear mechanicals The spacing is such that every 4-5 shifts, you're off by an entire cog. Simple tricks such as winding the cable around the outside of the clamp helps, but not enough.
- The 10sp shifters do not work with new 10 speed cassette + old 8sp Veloce rear derailleur. It works over a portion of the range, but I guess they never anticipated having the 8sp move over the range of the 10sp cassette. You will need a new 10sp rear derailleur.

Now everything is in place (front + rear derailleur, new 10sp chain), on the workstand it works perfectly. First easy km on the road works fine. Here is the problem: Any time under sprint power, the chain slips from the big ring down to the small ring.
The facts:
- I'm outta shape right now, not that powerful, and this is the same bike I've ridden for years @ 8sp and it has never done this.
- The front rings are TA Horus 50/39, only several thousand km at most, and I believe meant originally for 9/10sp Campy. I did not install any spacers when I was running 8sp
- The crankset is still the old 8sp Veloce one
- Chain is 10sp KMC, brand new, of course
- Front derailleur is brand new Campy Veloce braze-on mount. Shifts fine, and yes, I'm fairly certain I've set the gaps to the chainrings correctly (the new derailleur comes with a sticker & measurements, dummy proof).

Any ideas what is going on? The only thing I might think of is when I was running 8sp chains on this thing, it sits a little loose or shifts a little funny since I didn't have the extra spacers so that now it is a bit worn out so the new chain doesn't "fit" right and slips off??? I dunno... I'm open to any crazy ideas.

Chainline? Proper BB for that crank? Should be an ISO, 111, symmetric BB.