myth001

I just bought myself a new cyclocross bike (yoohooo!) that came with a Tiagra 10-speed DT. The rear cassette is a 12-30 Tiagra. I want to put a cassette with a larger ratio, so my LBS told me that I can use a 9-speed MTB rear derailleur.

He told me that it has to be a 9-spd RD, as it will have the same pull ratio as the 10-spd road DT. And suggested that I can use a 9-spd Deore RD with no problems.

I want to confirm that this will be the solution to get access to larger cassettes. Will it work?

And a friend of mine has a 9-speed XTR RD with him, will that work on instead of the Deore that the LBS suggested?


Also, in this case, if I need a larger ratio cassette, will I need to get a road cassette or a MTB cassette? 9 speed or a 10 speed?

Tried to search many websites, (XT Rear derailleur and Ultegra road shifter compatibility.? - Pinkbike Forum) was the only site that gave some information. Too many keywords give too many irrelevant results. Any help will be greatly appreciated.

Cheers.

HillRider

Your LBS is correct and Shimano's 9-speed (and prior) MTB rear derailleurs will work fine with 10-speed road shifters. Shimano's 10-speed MTB rear derailleurs have a different cable pull requirement and won't work with road shifters.

The 9-speed Deore is fine. The 9-speed XTR is also fine but a lot more expensive. To get the wide ratio you will need a 10-speed MTB cassette since 10-speed road cassettes don't go beyond 30T.

bradtx

myth001, The Shimano 9S and older mountain bike RDs have the same cable pull as the Shimano 10S shifters and will work, whereas the 10S mountain bike RDs have a different pull ratio. The 9S XTR RD will work with your shifters. Either a mountain bike group's or a road bike's group cassette will work.

Brad

jmb72

Yes the 9 speed mech should be fine. However Shimano changed the MTB pull ratio on their 10 speed kit - which is why they are suggesting a 9 speed.

Cassette spacing will be the same for road or mtb ... though for a 30+ it will be a mtb cassette.

myth001

That's great. So getting my friend's XTR RD will be the way to go.

So, with XTR - 9 spd RD, it can be any MTB 10 speed cassette. Right? Doesn't have to be an XT/XTR but an SLX or so should be fine also?

And does the chain also stays 10-speed? Is there any difference between the road / MTB chain? Any advantage of one over the other?

HillRider

Yes, any 10-speed cassette from any Shimano (or SRAM for that matter) group will work fine. Also any 10-speed chain will work equally well, there is no difference between "road" and MTB" chains.

2manybikes

Your bike shop is correct. I am using that set up on one of my bikes. It has a 34 t big cog. It shifts great and has over 7,000 miles on it.
Keep using the 10 speed chain.

well biked 

Be aware there were a lot of "Rapid Rise" 9speed XTR rear derailleurs, and your friend's RD might be one of them. Rapid Rise would work with your shifters (will make the shifters work oppositely of normal), but more people hate Rapid Rise than love it, and the derailleurs generally were a little more problematic than conventional ones (probably debatable). And it might be that your friend's 9 speed XTR RD is not Rapid Rise. If the RD came off a bike that had the dreaded integrated mtb brake levers/shift levers, the RD is almost certainly Rapid Rise.

myth001

Hmm, rapid rise, I'll check with him. Thanks.

Actually he's got an XTR M960, but he also has a carbon XTR-M972 shadow that he'll have to charge me a bit.
Which one could work better of the two?

well biked 

I think the 960 is RR, the 972 is not. Double check to make sure. My advice is to just go with the LBS''s 9 speed Deore, they are steering you right.

myth001

Is Rapid Rise the same as Rapid Fire? Or are they totally different aspects?

well biked 

Rapid Fire is a Shimano trade name for their trigger shifters, has nothing to do with Rapid Rise. FWIW, and there is some irony in this: the most problematic Shimano RD's we see in our shop, RR or not, are XTR derailleurs. Again, my advice: just get the 9sp Deore RD, it will work beautifully with your 10 sp road shifters.

Darth Lefty 

Careful, new Tiagra 4700 has the new RD geometry of the road 11-speeds and takes different pull and this trick no longer works!

Old Tiagra 4600 would work fine.

well biked 

Good point. The latest Tiagra (has both shift and brake cables running under the bar tape) is the only Shimano 10 speed road group that uses the new cable pull ratio. If it's 10 speed Tiagra with the shift cable coming out of the side of the shifter (externally), then it uses the old cable pull ratio.

myth001

Good point, I need to check for exact model in the bike. The cable comes from the side of the shifter - so it must be the older model.

I am also thinking of upgrading the shifters to 105 - 5700. Would that have the same pull-ratio as the 9-spd XT/XTR?

This is the bike I picked up.
Solo Cross | Rocky Mountain Bicycles

I got a great deal on it. Much better than if I spent extra to get a bike with 11-speed 105 already. I calculated that if I upgraded a few components myself on-by-one, it'll be a whole lot cheaper than having to dish our more $$$ on a bike that comes with those components standard.

I'm used to riding up the hills (no mountains in my area, sigh!). I'd like to get the 11-34T, and to get that I have to upgrade the RD for sure. And a few ppl have recommend that I upgrade the shifters from Tiagra to 105/Ultegra also.

well biked 

9 spd Shimano RD will work fine with 5700 10 speed shifters.

well biked 

The Rocky Mountain in the link has 4600 Tiagra, no problem with Shimano 9sp RD.

myth001

Awesome!

So, which one would be ideal, the XT-M960 or the XTR-M972?

HillRider

Which ever is NOT rapid rise. I don't think either one is but be sure. Also, be aware that neither of these appear to have a cable tension barrel adjuster as part of the derailleur (the MTB shifters have the adjuster in the shifter housing) so you will have to fit an in-line adjuster or have one on your frame's downtube cable housing stop.

The 9-speed Deore is not rapid rise and has the built in barrel adjuster so it's a better deal if your buddy want anything more than a nominal amount for the XTR's.

myth001

And in my case, do I still need to check for the "Rapid Rise" in the RD?

Oh, Hillrider just answered my question as I was typing it.... LOL


Cool, thanks a lot everyone. I'll check my LBS and have the stuff installed and tuned up for riding once the rain/snow in the next few days is done.

tsisak

Help please! This being a thread from 2016 I hope the info is still relevant.

I built a custom setup recently with the drivetrain as follows: 5700 STI levers, Deore M591 RD, SLX HG81 11-34 cassette, KMC 10.93 chain and a 38t narrow wide chainring. The bike was first built with 6600 levers and it was working OK (not flawlessly as I expected and read and was told ), but then I switched the levers from my regular road bike, and since then shifting in the back got pretty bad. The chain almost never sits nicely on a certain sprocket, even if after the lever's click it works, after a few turns of the pedals it starts jumping on the next sprocket, I never know higher or lower. I constantly have to guess and do trial&error whether does it need a click up or down. Of course it's worse when pushing it hard (high gearing on a short climb). I tried messing with the barrel adjuster and it got better on the low gears, but (as expected) worse on the highs.

So I started wondering whether the levers and RD are maybe uncompatible? According to what I read here, they should work fine. What am I doing wrong? Maybe the cable simply needs re-tensioning? Please help (

p.s. Next move is to put on a 34t chainring.

Kapusta

Did you change the chain when you did this swap? If so, that could be your issue.

If not....

Can I assume you have tried playing with the cable tension adjustment? And that you are using new cable and housing? And that you have checked the hangar alignment (or had a shop do so). If not, do so in that order.

tsisak

Of course the chain is the same! The whole setup is about 2 months old and has 600 km on it. Yes, I tried playing with the cable tension. Cable and housing are new enough. The hanger should be fine, the lever swap was done by a shop I should go back to them, most likely.

But on a different note, especially after I'll have the 34t on the chainset, would the chain being too long simply be the cause of jumping sprockets?

Kapusta

alias5000

This is good to know, thank you for asking this question!