Mixing SRAM with Shimano....(short term)

[JonF]

Over time (as funds allow) I'm looking at changing my current 5600 105 groupset to SRAM Force, now I'm starting with the chainset as that's where I'm going to get the biggest weight saving initially.

Will the SRAM crank run ok in the short term with the 105 shifters/chain? Would I need a new BB to suit or could the existing one remain?

Cheers

 

[CopperCyclist]

The problem with mixing SRAM and Shimano is with the gears. I forget which way round, but the pull ratio on the shifters isn't the same. One of them works on a 1:1 ratio, the other is a 1:1.3 (if I remember correctly). 1:1 means that the amount of wire the shifter pulls at the shifter end is exactly the same as the amount that pulls at the derailleur end, the 1:1.3 pulls more. This means you can't mix SRAM shifters with Shimano gear changers, or vice versa.

Cranks, chains and cassettes I can't see a problem with, though I stand ready to be corrected. Obviously the chain would have to be the correct length to fit the crank/cassette combo, but that's a given.

 

[Will1985]

I *think* you would need new BB cups as well. AFAIK, Hollowtech cups are interchangeable with MegaExo (FSA), but not SRAM's GXP type.

 

[JonF]

Thanks guys,

I'm a bit of a newbie when it comes to messing with bikes, I noticed there is a GXP and BB30 type SRAM Force cranks. I have a TCR advanced with a dura-ace press fit BB, which one would be more suitable?

 

[TheDoctor]

SRAM and Shimano cassettes are interchangeable.
You'll need to replace gear lever and (rear) gear mech simultaneously, due to the cable pull issues above. SRAM is 1:1, nothing else is.
Is Force really all that much lighter than 105?
Seems an expensive way of saving a few hundred grams...

 

[JonF]

Thanks for your input TheDoctor, it's about 600g lighter which personally I think is good value £ per gram.

 

[subaqua]

dunno if its any help but i have a deore crankset and hollowtech BB running a SRAM chain over a SRAM cassete with SRAM shifters on the MTB and have had no propblems. fitted as standard by Btwin

 

[adscrim]

I bought a Sram crankset a couple of months ago and it came with the required GXP bottom bracket. I was swapping GXP for GXP though and don't know for sure that the BB will fit your frame. I am however pretty sure that a BB30 won't fit.

 

[VamP]

Thanks for your input TheDoctor, it's about 600g lighter which personally I think is good value £ per gram.

Really?

105 as far as I can tell comes in at 936g. Is the Force really as light as 336g? Not according to weight weenies, they think it's about the same weight as Dura Ace.

Surely it would make more sense, bang for buck wise, to upgrade just the crankset, perhaps to Dura-Ace which should give you a similar weight saving but with no need to change any other componentry. Just the SRAM shifters will cost you £250.

 

[TheDoctor]

I think JonF is talking about saving 600g over the whole groupset, not just the chainset.

 

[VamP]

Yeah, he might be, but the principle still holds, it's easier from compatibility perspective to upgrade within the Shimano family.

One of the most expensive pieces in any groupset are the shifters, yet the weight differences between them are minimal. He could keep 105 shifters, upgrade mechs to Ultegra and chainset to Dura Ace or one of the FSA carbon jobbies, if that is what his heart is set on, and get the same or better weight saving for significantly less, and not have to do it all at once.