Peek the Geek

Excuse the very basic question, but... Checking out various cycloscross bike specs, I see quite a few with a road-type front der. and a mtb type rear der. Just wondering what the benefits are of using a mixed setup, and why do some choose to do all road components or all mountain components.

docbluedevil

Rear mtb derailleurs used for mtb/wide gear cassettes (e.g. 11/34)
Rear road derailleurs used for tighter gearing (e.g. 12/25)

Peek the Geek

So is either one much more common than the other? Does the decision come down mainly to the type of terrain a rider will be on most of the time?

dlbcx

Pretty much; the shifters will work with either type of derailleur. I run an Ultegra FD and an old XTR on the back. The only thing that might be problem if you try to use one of the newer XTR RD that is designed for the Rapid Rise shifters.

Sloth

I run a RR XTR rear derailleur with a road shifter, no problems. Everything is reversed, but it works just fine.

darkmother

The road FD's are shaped to work with larger big rings than the MTB equivalent. You can still use a MTB FD, but presumably it won't work quite as well. Rear deraileur is similar. MTB rears are designed for a wider gearing spread, but will still work on with a road cogset.

I'm using MTB front (old school 110mm BCD stuff) and MTB rear deraileurs on my cross bike. I run a triple with 28/42/52 gearing, and a rear road cluster of 12-25. It seems to work very well, shifting is great.

2WheelMotion

Can I use an Ultegra 9spd brake/shifter with an older (8spd) long cage XT rear derailleur? I guess I'll have to buy a newer 9spd mountain cluster

touringv

It seems like it is more intuitive. The big lever always means "faster" on either shifter, the smaller one ="slower." Do you have any problem with rear downshifting on your set up? My Dura Ace lever/ XTR Rapid Rise Rear D combo seems to want to jump a gear going down (but not up).

Anyway, MTB rear derailleurs "hold" more chain so you can run wide range (11-32, 11-34 in some cases) cassettes. Road deraillers with the same cassettes would either bottom out (contact the small cogs) or do the equivalent of knee hyperextension on the large ones,depending on the length of the chain.

ZenNMotion

Wow- can you bunnyhop backwards too?

ZenNMotion

You can use a 9 speed sti shifter with an 8 speed cluster, works OK, you just have a ghost click. Don't get a new cluster until the old one is trashed. In fact it might even work marginally better in wet mud than 9 speed as it's not quite so finicky about adjustment, and 8 speed chains are stronger. The older XT derailleur will work fine.

If you don't want anything larger than a 27t in the rear, a road rear derailleur will shift a little faster, be less prone to snagging the chain on something, and better prevent chain drop when you're sloppy with bouncing your bike around on remounts. But if you're not racing it's not a big deal.

Sloth

Nope, no problems. I'm using DA bar cons.