Bigger cassette and mech on my Madone

fishyweb

My 2013 Madone 4.5 has 10 speed Ultegra drivetrain, with a 11-28 cassette. I want to fit a 32T cassette next year for a trip to the Ventoux, and have found a Tiagra 10 speed 11-32 Tiagra cassette at Wiggle. I believe this will require a long cage rear mech, and the Tiagra RD4700 GS is meant to be compatible with a 32T sprocket, but will it be compatible with my Ultegra 10 speed shifters? Any other ideas on how to fit the bike up with 32T?

dj58

Probably not as the RD-4700 GS and ST-4700 10sp have a different pull ratio than your Ultegra 6700 10sp. Your RD 6700-A SS has a max capacity of 30T for the low sprocket, however you could try a longer B-Tension screw in the RD-6700 mech.

I have read on another post here that a bike shop mechanic used a longer B Tension screw on a customers bike to achieve clearance for a larger sprocket than was quoted for his particular RD.

Here it is viewtopic.php?f=40004&t=12952412

You could try this, though some may say it is a bodge, the standard B-Tension Adjusting Screw is (M4 x 13.5mm)

Do try it with the bike in a workstand so you can see if anything is going to foul the transmission up before road testing it.

The Rookie

I know it's MTB but I've found Shimano capacity and Max sprocket size are usually very conservative, my XTR rear mech has a nominal max sprocket size of 34t and is running on a 40t with nothing but a tweak of the b-screw.

fishyweb

Interesting, thanks for the ideas. Will follow up on them.

svetty

Another vote for 'just fit the 11-32 cassette - the odds are it'll work fine'

fishyweb

I had assumed that I'd definitely need a new mech as even the GS Ultegra is listed as max 30T on Wiggle.

dj58

Yes that is correct, both the RD 6700-A SS and GS derailleurs are 30T max low sprocket, the SS is for use with a double crankset, the GS is for use with a triple crankset.

fishyweb

DJ58 wrote:

Yes that is correct, both the RD 6700-A SS and GS derailleurs are 30T max low sprocket, the SS is for use with a double crankset, the GS is for use with a triple crankset.

Goodness, I'd no idea that having a double or triple up front would make any difference to the rear mech requirement. Is there an easy to understand explanation of why that is?

dj58

Have a read of this article http://www.sheldonbrown.com/deakins/lowgears.html

fishyweb

Thank you! That's an interesting read.

Da_Reverend

Just in case either
- your rear wheel is an older Shimano one or
- your Ultegra 10SPD cassette is NOT fitted to the rotor with a spacer
you might want to research if you own one of these 10SPD only wheels which are not compatible with some 10SPD cassettes.

Otherwise I as well would encourage you to just try with your existing RD as also the RD hanger is a factor (so Shimano's specs need to be conserative).

tsarouxaz

dont even think about buying ANY 4700 series tiagra components with any other 10sp shimano road stuff!! they are completely incompatible! you can use ANY shimano 10sp cassette but for more than 28t ring you have to go with a 9SP (YES 9SP) MOUNTAIN BIKE DERAILLEUR. shift ratio of all road and mtb rear mechs up to 10sp (road) and 9sp (mtb) are the same. I use 105 10sp shifters (5700) with an lx 9sp medium cage RD and I have a 11-34 cassette! so just buy a 9sp xt rear derailleur and the tiagra 11-32 or the slx 11-32 or 11-34(10sp) and you are done. forget ANY 4700 series part mix and match with others.(except the cassette which is the same as the mtb and road 10sp cog pitch)

The Rookie

Da_Reverend wrote:

Just in case either
- your rear wheel is an older Shimano one or
- your Ultegra 10SPD cassette is NOT fitted to the rotor with a spacer
you might want to research if you own one of these 10SPD only wheels which are not compatible with some 10SPD cassettes.

Otherwise I as well would encourage you to just try with your existing RD as also the RD hanger is a factor (so Shimano's specs need to be conserative).

Why would the cassette be fitted to a brake disc?

ugo.santalucia

9 SPMTBike derailleur is what you need for 10 speed road, but you also need an inline barrel adjuster to index the gears...

That's the setup I use

The Rookie

Ironically I used a Tiagra (flat bar) shifter on my MTB to go 10 speed without having to buy a new rear mech (and my XTR is a bit too nice to lose).

Bergwerk

Bought my 2013 Madone 4.5 with a 32 tooth cassette fitted. I myself never rode it like that, mounted a 28 tooth immediately due to personal preference. But seems the previous owner rode the 32 and had no problems.

fishyweb

Bergwerk wrote:

Bought my 2013 Madone 4.5 with a 32 tooth cassette fitted. I myself never rode it like that, mounted a 28 tooth immediately due to personal preference. But seems the previous owner rode the 32 and had no problems.

Interesting, thanks. Do you have the original Ultegra rear mech fitted?

Fingerling

Plenty of video's on youtube on this subject. Most seem to be by an aussie

I'm just about yo do this on my trek madone 5.2. I went with sram pg1050 as it was a bit lighter than shimano.

Another option I'm looking at it merging a long mech into my current deraileur. Ie buy a long mech derailleur take the cage off and got yo current deraileur

Bergwerk

fishyweb wrote:

Bergwerk wrote:

Bought my 2013 Madone 4.5 with a 32 tooth cassette fitted. I myself never rode it like that, mounted a 28 tooth immediately due to personal preference. But seems the previous owner rode the 32 and had no problems.

Interesting, thanks. Do you have the original Ultegra rear mech fitted?

Yep, original rear mech.

Nick Payne

If the mech doesn't cope, any 9-speed Shimano MTB RD will do the job. You need 9-speed, not 10-speed, as the cable pull was changed for MTB components between 9- and 10-speed, whereas it stayed the same for road components.