Mountain Bike Cassestte on Road Bike

[featuretile]

I bought an almost unused 2007 Specialized Ruby Compact with 50-34 in the front and 12-27 in the rear. My legs are getting a real workout on the hills in the Santa Cruz Mountains (CA) where we have great weather in the winter. Today was one of those magical days with full sun and 60 degrees! On flats and moderate hills this bike just flies.

Anyway, though I am doing fine on most rides, some could use lower gearing. So, I emailed Specialized and they said they did not know anything and that I should contact Shimano. So, I called Shimano and they said that they do not test or recommend any mountain bike cassettes on their road bikes. Yet, many people in the local bike club have mountain bike gearing on their road bikes. I'm just not sure what brand of bikes they have. I really don't need totally low spinning gears, just one or two more.

I looked up 10 speed cassettes and found a company that makes them called IRD. One shop said that you could install these, but that you would need a Shimano mountain bike XT rear derailleur regular. Or, I could change the front smaller ring to have fewer teeth. That sounds interesting. Would the jump be too much? Can you do that without changing the whole crank? The next LBS said they didn't think it would work and I should get a triple.

This is a lot of conflicting info. I don't want to buy a bunch of stuff and then not have the bike perform well or be out the money for the parts. Does anyone have any advice on the best way to do this? Or do I need to just keep what I have?

[HillSlugger]

To switch the cassette to anything larger than 27 or 28 you'll likely have to go to a mtb rear derrailleur. You could switch the cranks to a triple but you'd also likely need a new front derrailleur and/or shifter. Your LBS might be able to switch out your chain rings to smaller ones; that would be the easiest/cheapest fix.

[KnottedYet]

I solved a similar issue via chainring. Cost me a total of $19, and I've got happy gearing for Seattle's hills. (Salsa makes some fine chainrings at good prices that are compatible and available in black or silver so they even match whatever scheme you've got currently.)

ETA: oooh, I just realized I did the chainring switch with TWO of my bikes, not just the one I mentioned above. It really is a very easy and cheap way to get lower gearing, and later you can switch back if you decide you liked the bigger rings after all.

[ridebikeme]

Knot made a good suggestion with the chainring, although I think in your instance it would HURT shifting. If I have read your description of your bike accurately, you have a 50-34 compact crank.... which means that your front derailleur is at its limit with that setup. You can indeed put a mountain bike cassette on a road bike, but currently with some issues.(if you have a 10 speed drivetrain) Shimano does not make a 10 speed rear derailleur(mtn bike), so although someone can probably make something work, I don't believe without problems. People have mixed and matched Shimano and Sram together, but it does add a bit more noise to your drivetrain, and again, not without some issues. The thing that I would suggest(although costly) would be to add a triple crank. You would have to buy a front shifter, crank, bottom bracket, and front derailleur, but that if installed correctly would be your best bet. Down the road, I'm sure that Shimano will come out with a 10 speed mountain bike group, and then you'll be able to lower gearing even more and have something that actually works.

The compact cranks are indeed an issue for those of us that live in the mountains... they simply aren't low enough.(especially with 10 speed drivetrains) I'm hoping that Shimano and SRAM will realize this, but only with complaints from customers and many bike shops! :rolleyes:

[redrhodie]

I have a Shimano compact crank, and a 10 speed IRD 11-32 cassete, and it works perfectly. I happened to already have an Ultegra triple front derailleur, and that gave enough room that I didn't need a long cage rear derailleur. I remember when my lbs guy decided to try it out (without changing the rear derailleur), no one was sure it would work. That was over 2 years ago, and it's still working perfectly. No chain drop issues.

[ridebikeme]

Redrhodie, I wondered if you could answer a question for me. When you are in your small chainring and your 32T does your rear derailleur bump up against your cassette?

Obviously, you are someone that understands "how" to shift your bike, because otherwise there would be some issues. At any rate, hopefully over time Shimano will come up with a 10 speed mountain group and that will solve most of the problems.

[ridebikeme]

As I was heading out to take the dogs for a walk; I came up with another idea.;) IF you make sure that you have a Shimano "GS" rear derailluer, it definitely will work with a mountain cassette. If I remember correctly, the IRD cassette jumps from a 28T to a 32T which for some people is too big of a jump. The other option is to use a SRAM 10 speed mountain cassette which is a bit more even in the spacing on the cassette, but very expensive. ($300)

I love thinking about all of this sort of thing, thanks for sharing:D

[redrhodie]

Redrhodie, I wondered if you could answer a question for me. When you are in your small chainring and your 32T does your rear derailleur bump up against your cassette?

Obviously, you are someone that understands "how" to shift your bike, because otherwise there would be some issues. At any rate, hopefully over time Shimano will come up with a 10 speed mountain group and that will solve most of the problems.

I've actually (consciously) never used that gear combo, but I'm sure there'd be some rub, and maybe even stress on the rear derailleur??? I use my 28T as my lowest gear. I do go through a lot of chains, so that may be an issue (like 3 this past year). Granted, one rusted, so it wasn't a stretch issue, but I have had chains stretch.

ETA:

I just checked, and it does indeed rub (the front derailleur/chain) when in the 32T. The rear derailleur seems fine, but I'm guessing the big ring/lowest 32T gear wouldn't be a happy place.

[ridebikeme]

The rub that I was talking about is the rear derailleur when you are in your 32t and your small chainring up front. You may indeed have a Shimano "gs" road derailleur, so you wouldn't have any rub where the derailleur hits the 32t. In terms of your front derailleur rubbing on your chain, that is simply because the derailleur limit screw is abit too tight. Whether you had a 32t on anything else as your low end on your cassette, that won't have any affect on chain rub unless the limit screw isn't set up correctly. The other factor here can also be the chainline of your bike. You might have your LBS check this the next time that you have a new chain replaced.

At any rate, thanks for the answers!:p

[redrhodie]

The rub that I was talking about is the rear derailleur when you are in your 32t and your small chainring up front. You may indeed have a Shimano "gs" road derailleur, so you wouldn't have any rub where the derailleur hits the 32t. In terms of your front derailleur rubbing on your chain, that is simply because the derailleur limit screw is abit too tight. Whether you had a 32t on anything else as your low end on your cassette, that won't have any affect on chain rub unless the limit screw isn't set up correctly. The other factor here can also be the chainline of your bike. You might have your LBS check this the next time that you have a new chain replaced.

At any rate, thanks for the answers!:p

Ah, you're right, it is the back derailleur that's rubbing. The front is actually not, there's bit of space there.

[featuretile]

So, I appreciate all these answers, but I still don't know what to do. The IRD 11-32 works for Red Rhodie, but she has a triple and I have a double. I looked up the Salsa cranks, and they are for 5-9 speeds, not 10 speeds. I don't think I want all the expense of changing to a triple. It would kind of negate the fact that I got a good deal on this bike. The SRAM cassettes are over $300, I found an IRD cassette online for $119. I emailed the online seller, and he said an IRD 11-30 would probably work with my short cage derailleur and new chain. That would give me one gear lower. Is that enough? Would I still have problems shifting?

The bike shifts so nicely now, but today I hit a big hill and had to walk.... My DH tried getting up in a similiar gear (not his lowest) and he also had to walk... However, I notice my thigh muscles are getting stronger, and I even passed my teacher because she has lower gears and I could not ride that slow.

[ridebikeme]

Before I go too far, I want to tell you that a crank is not compatible with a five through nine speed drivetrain! Obviously as you put more gears on the rear wheel, you need a narrower chain along with different derailleurs that are compatible.

Secondly, if indeed you have a short cage derailleur it is NOT compatible with a 11-30 cassette. The rear derailleur cage is not long enough for that size of cassette, and will hit the bottom of the 30t or 32 t cog. It is made for a 27T cog.

To answer whether this is a low enough gear for you, only you can answer that question. Only you know the ability that you have, and the terrain that you ride. ...

My suggestion here is to visit your LBS, and get answers that are accurate. The information that you are receiving online is very far from the truth and that can lead you into components not being compatible or not giving you what you want. Save yourself some money in the long run, get information that you can use, and go to a shop.

[redrhodie]

ridebikeme gives good advice. I just want to clarify that I have a compact double crankset, not a triple. But, it looks like I'm only getting one more gear with my setup than you currently have, since I use the 28T as my lowest gear.

If I were riding in the mountains, I'd get a triple. No doubt about it. My compact is fine for around here, but it's pretty flat.

[featuretile]

I went to 3 LBS and asked the same questions. The first one said no problem to change to an IRD casette with MTB derailleur. The second one talked about chain capacity and said that IRD did not shift as well as Shimano. He thought I might be able to get away with a 12-30 (not 11-30) with my short cage derailleur, but would need a long cage for the 12-32 or 11-32. The third one said that I would need a long cage derailleur for the 12-30 and a MTB derailleur for the 12-32, but that it would not shift as well as now. Apparently, the spacing is slightly different than Shimano to avoid patent infringement. He recommended learning to stand up while pedaling uphill instead (which I have not mastered yet). How do you start that? Eventually Shimano will make a 10 speed MTB cassette (2011). The SRAM one would work, but it costs $330 and is 11-34 (which I don't need). I just emailed IRD and will see what they say. It never occurred to me when I bought the bike that I could not just simply get a larger cassette.

[redrhodie]

Okay, I have a little more info for you, but it still won't help you know if the IRD cassette will work on your bike (and in fact will make it more confusing--sorry).

According to my shop guy, who has a similar set-up as me, but with even lower gears than I have (Shimano compact double crankset with an IRD 10 speed 11-34 MTB cassette, and long cage derailleur), he can even use the 34T cog with no rub. He then tried to run the exact same setup on another of his bikes, and it wouldn't work at all. He figured out that the problem was the position of the derailleur hanger on the frame (which probably has another name, but I can't remember it :confused:). So unfortunately, it's another factor which may make it not work.

But, after thinking about this thread, I decided to upgrade myself to an ultegra 11-28 ten speed cassette. :) I'll get all the same gears I currently can use with my IRD, for 100 grams less. Woo-hoo, I'm excited! My IRD has around 7,000 miles on it, and it's still going strong, but the thing's a tank.

Let us know what you end up doing. Standing on hills will make you stronger, as will just working at it, but you don't want every ride to be miserable. You should be able to get a better range. Good luck!

[featuretile]

So, after many emails and telephone calls, this is what I learned:

Specialized (the bike maker) does not have any information about conversions to wide range cassettes.

Shimano (the component maker) does not make any rear cassettes with more than 27 teeth in 10 speed, and does not recommend after market conversions.

IRD (maker of wide range cassettes) said the following: "As far as compatibility and shifting performance, the two biggest factors will be the derailleur cage itself and the person setting it up. With the 30t, a short cage will be fine. On the bigger ones, the mid-cage mountain or mid (longer) cage road will usually work, but we officially recommend a long cage mountain derailleur. Shimano lists limits and we have found them to be overly conservative, really most short cage derailleurs will perform the same as other short cage derailleurs.Second, your local mechanic will be your best resource for fit. See what your shop recommends and refer back to the general derailleur length guidelines above."

This was very vague to me - it did not specify which rear derailleur to buy as there are many of them. I did not want to buy all these parts and then have the bike not work right. The 2 LBS that I went to and asked about the conversion said they did not shift as well. They recommended that I should learn to stand up and pedal...... It seems that on every ride here in the Santa Cruz Mountains, there are a few places with really steep, long grades that are not fun and could use a lower gear.

Then I went for a club ride and one of the women had what appeared to be a bigger cassette on her 10 speed triple road bike with 105. Her bike was custom made, so I asked for the maker's email address. He gave me a simple answer to the question of which components to buy (which was the same one that Unrealcycles had given me in the first place). " Lilly Ann has an 32 tooth IRD cassette with a Shimano 105 long cage rear derailleur as I remember, I also remember that the shifting seemed fine to me... Any good bike shop should be able to help you with that... A double crank shouldn't be a problem... You should stick with a 105 10 speed long cage derailleur as most MTB stuff is still 9 speed... Hopefully someone can get you rolling, it shouldn't be a big deal..."

So, I ordered a 12-32 IRD cassette, 105 chain, and 105 long cage derailleur today. It seemed logical to me that the reason that some people have problems with IRD cassettes and some don't is that the components are not compatible. Why would IRD recommend a MTB rear derailleur that is 9 speed and not a long cage road 10 speed derailleur that would fit better? Perhaps it may have to do with the larger 11-34 cassettes, but I don't need that.

I'll let you know how it works when I get it installed.

[SadieKate]

I would recommend that you do a little research on chain wrap. Not all long cage dérailleurs have the same capacity. And it's not simply a function of the largest cog on the cassette. You also need to take into account the chain rings.

Here is an explanation with some Campy info, but the same concept holds true for all dérailleurs.

http://branfordbike.com/articles/rear-derailleurs-pg62.htm

[featuretile]

I did do a calculation of chain wrap for my bike before I ordered the parts. I went into the Shimano website and looked up the specs on the derailleurs for chain wrap capacity. The front is 50T-34T=16T, the new rear cassette will have 32T-12T=20T. 20T+16T=36T. The chain wrap capacity of the long cage 105 derailleur is 37T, so it should be ok. I could have gone for the 11-32, but didn't think I would need higher gears and wanted to play it safe. An 11-34 would not work.

What is ironic is that the original bike components are out of spec. With a 12-27 rear cassette, I get a chain wrap capacity of 31T, but the small cage rear 105 derailleur has a rating of 29T chain wrap on the website.

The problem with the MTB cassettes is that most seemed to have chain wrap numbers of 33T for the small and 45T for the large, and I don't know if they are attached to the bike differently. (I have learned all this in the last week.) Those seemed too small or too big. So, now I will cross my fingers and hope that it works or I am out $200+.

[featuretile]

So, I had my new components installed yesterday and went for my first big ride today (in between terrible rain storms - no power for 2 1/2 days, much debris in the road). The bike worked just great! It shifted as well as before. There is no rubbing and it is very smooth. I now have 2 new lower gears, and I could get up the big hills much better than before. Instead of 34/27, I have 34/32. Why is there so much lack of knowledge about how to do this from all the professionals? Why would they recommend a mountain bike cassette which is for a 9-speed bike, when a long cage 10 speed derailleur would obviously be more compatible? I think this mismatching of components is why other people have had problems with this conversion.

To summarize, this is what I learned. I installed an IRD 12-32 cassette, with a new chain and a long cage 105 10-speed rear derailleur on my Specialized Ruby Compact. To find out what size derailleur you need on your bike, you need to figure out the chain wrap capacity.

You take the number of teeth on the largest front ring and subtract the number of teeth on the smallest front chain ring. (ex. 50-34=16). It doesn't matter if it is a triple or a compact double. (In a compact double the small ring has the average number of teeth between the small and middle ring of a triple.)

Then you take the number of teeth on the largest ring in the rear cassette and subtract the number of teeth on the smallest ring in the rear cassette. (ex. 32-12=20).

You add these two numbers together to get the chain wrap capacity.
(ex. 16+20=36). The chain wrap capacity for my bike with the new cassette is 36. Then you look up on a website the chain wrap capacity for your derailleur in the bike specifications. My small cage rear derailleur that came with the bike had a capacity of 27 and would not work. The new long cage derailleur has a capacity of 37, so will work with the new larger cassette. An 11-34 rear cassette would probably not work or would need a (larger) mountain bike cassette, but would have the issues of 9 vs. 10 speed.

I hope this will help anyone else who needs to get lower gears on their road bikes. I am really happy with mine.