Flash

Curious about shifting quality when pairing say a shimano FC-R700 34-50 crank with a seven speed RD and 7spd HG cassette and chain.

thanks

DMF 

FC-R700 is designed for a 10-speed chain. A 7-speed chain is much thicker.

Why don't you mention the FD? We'll have to assume it's a 7-speed FD since the 10-speed version is probably too narrow to work well with a 7-speed chain.

I'd say avoid the 10-speed stuff unless you use a 10-speed chain. A 7-speed FD will probably handle a 10-speed chain a lot better than vice versa, though shift quality likely won't be all that great.

More missing data: Indexed or friction shifting?

TallRider

it's worth noting that 7-speed chain is probably the same as current 8-speed chain.
chainrings designed for 10-speed chain are designed to sit slightly closer together than those designed for 7- or 8-speed, basically so the narrower 10-speed chain doesn't get caught in between the chainrings. But your combination will probably still work, if you're using a 7- or 8-speed era front derailer and a non-indexed front shifter.

AEO

it works, rubs a lot when you cross chain in the small ring however.

TallRider

If you want compact gearing, find an older crank with 110mm bolt-center and chainrings designed for 8-speed chains. I've got some such stuff sitting around, there was plenty of it back in the day.

ean10775

I considered adding a compact crank to my 7 speed road bike, however I decided it might not be such a good idea, at least for my application after reading this article: https://bikehugger.com/2008/05/the-ri...act-crank.html

Based on the premise that if you want to take advantage of compact gearing you need an 11-tooth sprocket, an 7spd 11-28 'ac' cassette is going to leave you with some relatively large jumps that may degrade shifting performance in the back, not to mention any degradation to shifting in the front unless you run a compact FD. With a 10 speed drivetrain you can get that same 11-28 sprocket range with smaller jumps in between and more gears to fill in the holes so that makes more sense in my opinion.

Garthr

Chains start with 6-8 speed compatibility. Then a 9sp, which is slightly narrower, then a 10sp., narrower yet. There is no "7 speed" specific chain.

It's getting f'd up for people who just need a new crank.

Everywhere I've read though, says a 9 speed chain can be used with a 10 speed crank. And, you CAN use a 9 speed chains on a 6,7,8 speed set up. The inside width is the same, only the outside of the chain is narrower, so it makes no difference to your freewheel or cassette.

If you need slightly more space between rings though, they make thin spacers you can put between the bolts. The .6mm are the ones. The you can use the 6-8sp chain. In theory that is,as I may be wrong.
https://wheelsmfg.com/content/view/518/54/

AEO

shimano does not make a compact specific FD and all of those 'regular' FDs work just fine with their cranks.
you can find 'compact specific' FDs from FSA because their chainrings suck.

HillRider

Not an FSA fan are you?

IIRC, Campy made "compact specific" front derailleurs for a while but has now said their standard fd's work fine with compact cranks.

AEO

they're priced similar to shimano stuff, except their BBs wear out faster and have poor dust caps
the cranks themselves are probably ok, but the chainrings, well they have a lot to be desired.

sunburst

I added a SRAM Rival compact crank to a mid-80s 6-speed 105-equipped Trek. Didn't have to change anything but the crank and bb. It works flawlessly.

Flash

Now this is a good idea!