changing 36t chainring to 34t

rob39

just decided to book a cycling trip to the pyrenees, currently use a fsa slk 50-36 crank/chain ring with 105-ultegra mix group 12-27 cassette. So to make things a little easier I'm looking to put on a 34t inner ring.
Is it a straight forward swap? and can you get a 29t sprocket on a shimano cassette.

itisaboutthebike

Hi,
nope can't get a 29 sprocket on a normal road Shimano casette - biggest they do is 12-27 (you could use a mtn bike cassette say 11-32 but a Shimano short cage rear mech won;t cope with that).

A normal Shimano short cage rear mech will cope with 34x50 and 12-27 cassette.

Monty Dog

34T chainring should be no problem, as would fitting an MTB cassette with bigger large sprocket - swapping individual sprockets on Shimano cassettes is difficult as they are either screwed or rivetted together, so swapping cassette would be easiest and you may need to lengthen your chain by a couple of links too. I'm assuming your rear mech is a GS, long-arm model also.

maddog 2

11-32 needs a mtb mech, not just a long cage road mech.

dennisn

You may experience a bit more chain "dink" with a 34 tooth than a 36 if you use the 34
on the smaller rear cogs(12-13-14). This is because the 34 is a smaller diameter than
a 36 and runs closer to the big(50) chainring often just slightly touching it producing
the so-called "dink" noise.

Dennis Noward

andy_wrx

Snap ! Exactly same as you Rob, I'm running FSA SLK 50/36 with 12-27 and 10sp full Ultegra including short-cage rear mech
(Spesh Roubaix by any chance ?)

Except I've actually bought a 34t FS inner ring (from PBK last month when they had a this-weekend-only extra discount (again !))
I've not fitted it but offered it up to the chainring and it looks fine.
I was hoping I could leave the chain the same length (I don't run 36 x 12 or 13 now as it rubs/tings against the 50t ring I think, so I wouldn't be running it with the 34 x 12 either)

The 30/36 12-27 gets me up all the hills that they like to run UK sportives on, but I went to the Alps for a week last year and found I wanted a lower gear.
UK hills are short-and-steep, or if they're longer at least they have steep bits then shallower bits and so you can recovert, or they're steep for a bit so that you're out of the saddle and then shallower so you climb seated.
The Alpine climbs however were e.g. 7% for 15 miles and that meant steady-graded 7% for 15 miles without the steeper bits, shallower bits and no flat at all. I could climb them on 36 x 27 but in order to go at a comfortable cadence I had to go up at about 8mph. I was knackered at the end of the week and a bit envious of those running triples who'd twiddled-up in lower gears, a bit slower perhaps but enjoyed it more.

willbevan

SRAM do a 28T rear cassette that will work with a shimano road rear mech not that it inceases it much really.....

Someone did link me earlier

http://store.interlocracing.com/10elcas.html

which is a 11-32T 10speed block, more expensive than i like but if its what you want, you would need a mtb mech though as someone mentioned.....

I have run a 8speed 11-32T on a sora rear mech, which was far from ideal... so got an XT rear mech...

pneumatic

double snap! Spesh Roubaix. FSA set up. I put on a 34t before going to the Ventoux last year. The supplier said they couldn't guarantee that it would not be a bit clunky but I took the risk. In the event, it is as smooth as the 36 both ways.

Dead easy to change the rings, go for it.

I am nearly 16 stone, 45 and not a fitness fanatic. The 50/34 x 12/27 set up was fine for the Ventoux. I've also used in on a nice little 20% (1in 5) near here and I can keep the pedals turning no bother.

hope that helps.