cadimaki

I have a 1996 peugeot road bike. It has rx 100 components on it, which are a double crank (42/52) and a 7 casette.

I wonder if I could use a ultegra 6603 triple crank (30/39/52) with this set up. The 6603 is said to be suitable for 10 speed. Does this mean that it can only be used with a 10 casette? Or is it ok to use it with my old 7 casette? And which kind of chain shall I use? One for a 10 casette or 7 casette?

droptop

you will probably need to use a 9 speed chain (as most 10 speed stuff is backward compatable with 9 speed- 9 speed uses a "narrow chain" and 10 speed uses a "super narrow" chain) , and im not entirely sure that the 9 speed chain will fit over a 7 speed cog. if it does not, you should be able to find some older gears that will retrofit onto that crank, as it is common spacing at a local co-op for cheap if you have one.

since that is a modern generation ultegra, it has the axle integrated into the ds crankarm with an external bb, so no need to get a new bb.

someone else should be able to chime in on the exact 7-10 speed compatability.

enjoi

french threaded outboard bb, this will be fun

Psimet2001 

+1 - therein your problem will reside.

Also....is your RX100 using integrated shift levers (STI levers) or using downtube? My wife has RSX with STI levers is why I ask.

If they are double sti then you will have issues front shifting a triple crank.

Apart from theat the crank will work with the drivetrain. +1 the recommendation to go with at least a 9spd chain to help avoid possible chain rub on the chainrings.

cadimaki

If the original bb of ultegra would fit to my bike, then it's cool cause the guy selling the crank second hand is giving the bb free.
My both levers front and back are downtube levers. The one for casette makes "clicks" on every gear and the one for the crank moves smooth (I don't know the exact terms). So if I would change the casette, I think I had to change its lever too.
To change the casette for a 8-9 speed one wouldn't be the big problem. I just wonder if one can find downtube levers for such higher gears or is the downtube lever conseidered as an ancient gadget today? I do not want to go sti on this bike...

Psimet2001 

You don't need to change your cassette. Leave it a 7.

The BB has to be changed in order to go to a 6603 crank. A 6603 crank uses outboard bearing cups style BB. Not the internal/square taper spindle that you currently have. The issue is that external cups don't usually come in the outdated French thread that enjoi implied your frame has.

I don't know for a fact that there are no French threaded external BB cups available. Someone may make an aftermarket one.

I don't know for a fact that your frame has a French threaded bottom bracket (BB).

....but if it is you may not be able to use the crank at all.

As for "speeds" of drivetrains....don't let it confuse you. cranks is cranks. You can almost always run thinner chains than what your current system was designed for. "higher speed" (8,9,10) chains are thinner as they go "up".

Your friction shift downtube lever will shift a triple just fine. No need to go STI at all. Your rear derail and cassette don't care if you run a thinner chain and they crank has absolutley no impact on how they function.

Hope that helps.

cadimaki

Yep, it helped a lot. Thank you for the detailed answer.

I guess the best thing to do now is to go to my LBS and ask the stuff about my bb situation. And if it's ok, I might get that ultegra crank and stop torturing my knees on those steep hills in my town

enjoi

you may want to consider a 39 or 38 for the small ring up front