Bicycle Mechanics - Spinning crank backwards and chain

So if I have chain on the 53 in the front and 25 in the back and turn the crank backwards, the chain's not supposed to skip off, is it?

The gears seem to shift well enough and all that, but when I have the bike in a stand and put it in big/big and turn the crank backwards, the chain eventually upshifts itself before completely falling down the cassette. The crank and chain were newly installed, and I don't think I was having this problem before with my old setup. Could it be a derailleur position/tension adjustment? Stiff links? Chain too short?

Thanks.

Cross chaining is not recommended on the stand or while riding. I think the tension that the current length of chain on the derailleur is probably what causes the chain to shift off the cog.

So if I have chain on the 53 in the front and 25 in the back and turn the crank backwards, the chain's not supposed to skip off, is it?

The gears seem to shift well enough and all that, but when I have the bike in a stand and put it in big/big and turn the crank backwards, the chain eventually upshifts itself before completely falling down the cassette. The crank and chain were newly installed, and I don't think I was having this problem before with my old setup. Could it be a derailleur position/tension adjustment? Stiff links? Chain too short?

What are you using for a shifter? I'd think that as long as the shifter is able to maintain steady tension on the shift cable the derailleur wouldn't let the chain drift down to the smaller cogs. If you have down tube or barcon shifters you probably need to snug up the tension adjustment about 1/8 turn.

I doubt the chain's too short. When that happens the chain either won't shift up onto the big cog or it's so tight that it won't shift down off of the biggest cog.

Cross chaining is not recommended on the stand or while riding.
+1!
Crosschaining is a no-no!
Always wondered why shops don't point that out to customers.:rolleyes:

Volt....what you are describing might be common with 10 speed systems due to the much narrower tolerances. My 8 speed drivetrain will not do that when crosschaining and spun backwards.....the chain stays on the big cog without hesitation.

It will depend on your chainline. Some have a tendency to do what you are seeing and some are more tolerant. Do you have a triple crank so the crank is spaced further out from the centerline?

I have a Campy 10-speed triple and a Shimano 9-speed triple equipped bikes and neither will tolerate back pedaling in the big-big combination without spilling the chain off of the big cog.

On the other hand, I also have a Shimano 7-speed, double chainring bike and it will allow backpedalling in the big-big with no problem.

Thanks, all.

I've got an Ultegra 10-speed double. I tried the same thing with my 105 9-speed compact double and it would spin fine. I don't cross chain when riding, but I just happened upon my discovery while I was tuning the bike. On the plus side, everything shifted smoothly today while riding. I'll just remember not to pedal backwards for extended amounts of time while cross chained all the way. :lol:

Thanks, all.

I've got an Ultegra 10-speed double. I tried the same thing with my 105 9-speed compact double and it would spin fine. I don't cross chain when riding, but I just happened upon my discovery while I was tuning the bike. On the plus side, everything shifted smoothly today while riding. I'll just remember not to pedal backwards for extended amounts of time while cross chained all the way. :lol:

Like Hillrider mentioned, the difference between your two bikes is perhaps your chainline. Your Ultegra cranks might be a tad further out compared to the 105 to cause this difference.

And in case it matters, as soon as I start turning the crank in the proper direction, the chain pops back onto the correct gear and spins normally.

And in case it matters, as soon as I start turning the crank in the proper direction, the chain pops back onto the correct gear and spins normally.....thanks to your derailleur...

....thanks to your derailleur...

I should buy it something for Christmas.

I should buy it something for Christmas....how about a pretty purple pulley wheel?....:D