kt22mike

I currently have a Shimano 105 RD 5701 GS with an 11/32 cassette (10 speed). Wondering if I could install an 11/34 cassette and have the derailleur accommodate the larger gear. The specs for the RD says largest gear is 32T with up to 37T chain wrap. As I have a a 48/34 compact front I will be right at the max chain wrap.

Can I install the larger 11/34 cassette without running into issues given the "max" gear per the Shimano spec is 32T (I don't want to use a Wolftooth roadlink)?

aggiegrads

Two extra teeth is generally OK. I have not tried your specific derailleur, but most people find that it is OK to go two or four teeth over spec. You may need to run the B screw in much farther to clear the largest cog, and make sure to check the chain length in the new big chainring - largest cog combination to make sure the chain is long enough.

exceeding the max chain wrap is not a big deal. The worst thing that will happen is that you will have slack and rub the jockey and idler pulleys together on the RD when you accidentally shift into the small-small gear combination, which requires the longest chain wrap. You shouldn’t be in that gear anyway.

dsbrantjr

Do make sure that the chain is long enough to go into the big-big combination without strain. Even better, install a new- properly-sized chain to go with your new cassette, and keep the old ones together as a set.. New and worn parts do not always play well together.

Elvo

I think it would work with some b-screw adjustment. I've fitted a RD 5600 SS with roadlink on a 11-40 rear cassette.

Bill Kapaun

Shimano spec's their RDER's to work in a worst case scenario re: hangar geometry etc. (not all bikes are exactly the same in this regard)
You're "probably" good, but one simply cannot guarantee that. Maybe a slightly longer B screw will be needed??

tomtomtom123

What is the BCD of your crank? Going from 11-32 to 11-34 means wider stepping. How many speed is the cassette? You would get more functional gearing and a wider range if you lowered your small chainring to a smaller one instead. Typically doubles have up to 16t jump, but I use 20t jump.
Lowering your small chainring to 32t would actually give you 32/32 instead of 34/34, which are identical at 1.0 gear ratio but you get closer stepping between gears. But you could think about a 30t small chainring or lower.

shelbyfv

You should be able to tell if your 32T is close to max. Agree the 34T will probably work and certainly worth a try.

kt22mike

thanks for the advice on the smaller chain ring (32 versus current 34). I have not been able to find this size chain ring as I have a Specialize PF Oversize Bottom Bracket with a S-works 5 bolt crankset. A replacement 32t chain ring, 10/11 speed 110 BCD does not appear to exist.

I was able to replace the 50 with a 48t. but the 32t is allusive.

Only option I have been able to find is to replace the complete chainset using the Praxis 48/32 set but this requires me to also change the bottom bracket with a Praxis BB - which maybe getting rid of the PF BB might not be a bad thing. An expensive upgrade for 6% lower gear.

shelbyfv

No, you won't find smaller than 34T, though there may be some boutique kludges. Did you try the 34T cassette? If you really want to change the crank, I'd suggest the Shimano GRX. You can get as small as a 30T chainring. You would need a bottom bracket and possibly FD.

kt22mike

going to try the 11/34 cassette - though the only one available i can find is Tiagra grade

tomtomtom123

Smallest chainring for 110bcd is 33t. To go lower you need smaller BCD. The grx with the 46/30 actually could probably go down to 26 or 28 but Shimano doesn't make them. It uses uncommon BCD and asymmetric bolt pattern. Wolf components said they were thinking of making compatible rings when I asked but I don't know if they really will. The chain line is also further out but maybe you could shim it.
i was thinking to laser cut a 3mm aluminum plate to turn the uncommon BCD into a 74mm 5 bolt. Then shim the outer chainring by 3mm.