Jonneh

I am looking to use an 11-speed mountain bike cassette with the 11T cog removed on my 10-speed road bike to get the gear spacing and range I'm after. From what I can see from charts, sprocket width is the same and MTB 11-speed centre-to-centre spacing is 3.90 mm while road 10-speed centre-to-centre spacing is 3.95 mm --- if ideal alignment is centred on the middle two cogs, the outer cogs would be 0.25mm off correct alignment, which I'm guessing wouldn't be a problem for precise shifting.

The lockring seats just fine in the penultimate cog in other Shimano cassettes I've tried with, so I don't think that'll be a problem. As far as I can tell, then, this should work. Am I missing something?

Crankycrank

Not likely to work as even such minimal differences in spacing make a difference in shifting accuracy. If you had one in hand already I would just say give it a try but doesn't sound like you have one yet. Also, if the cogs are loose (or riveted or bolted together you can remove those to free up the cogs) you can just replace the spacers with 10 speed but cogs like that for entire cassettes are rare these days.

Jonneh

Ah, that's too bad. I don't have a good handle on how much of a difference a fraction of a mm here or there will make, but I'm sure you're right.

Indeed I don't have a MTB 11-speed to hand to play with, which would put the question to bed, but I thought one of the tinkerers here might have tried it. It's a shame, because some of the 11-speed cassettes have a nice progressive percentage-gap ramping towards the lower gears where equivalent 10-speeds have big jumps in the higher gears. I'd happily do away with the 11T cog on many of these and start at 12 or 13.

I'll keep in mind the spacer option, but it sounds like a long shot.

tFUnK

I would just look for a 10 speed MTB cassette and replace individual cogs as desired. For example if it's 11-13-15... You can just get a 12t to go 12-13-15... I've gone the route of cannibalizing extra cassettes or buying individual cogs to get the gearing I want. I believe the cogs are the same for 10 and 11 speed - that just the spacers between cogs differ, so you may even be able to cannibalize an 11 speed cassette to get what you want (assuming cogs can be separated - the last 3 big cogs usually cannot).

maddog34

if you don't use the 11t cog, the LOCKRING will Not Be Locked into place... among the many other issues mentioned ... that 11t cog has serrations that interact with the serrations on the Lockring to LOCK it in place.

just use a 10sp. cassette that you'll like, Enjoy Riding, and quit over-thinking gear ratios.

icemilkcoffee 

Just install that 11s MTB cassette onto the 10 speed road hub. There is no need to leave out the small cog. The 11 speed cassettes with >=34T large cog, have a dished in back side such that it would fit over the 10 speed cassette.

tFUnK

The cassette will work but I think OP plans to keep the 10 speed shifters.

Jonneh

Indeed, that was the plan, but I'm sure crankycrank is right that even 0.25mm out on either side is too much if I want to maintain precise shifting.

I don't think I'm overthinking ratios (I ride a singlespeed most days after all); I just want lower gearing for extremely steep alpine passes with luggage and would be happy to do without the 11T (and probably 12T) in exchange for tighter spacing, if it could be had. Slapping on an 11-speed MTB cassette minus the bottom cog with a 12T lockring against the 13T cog with its integrated spacer (locks just fine IME, even sans knurling) would have been a quick and easy solution, but if it won't work because of poor shifting, then it won't work.

I'm going to go with a wideish range 10-speed cassette, take the 11T cog off so it'll start with the 13T, and add an third-party cog onto the back with a spacer. Should do the trick.

Crankycrank

SRAM and SUNRACE make Shimano compatible 10 speed cassettes in 12-32 & 12-36 sizes if that's what you're looking for. I couldn't find any that start with a 13-30+t which are getting harder to find.

Iride01 

Make sure you are basing the range and spacing of the gearing by what you feel in your legs. On paper what we see isn't really what we are feeling. Not certain what you are after, but you want close spacing for the gears you will be in most of the time. The other gears you only need for climbing can have larger steps between them.

Unless of course all your rides are in groups where speed is dictated by others and the ride is also entirely climbing.

Russ Roth

Not certain what gear range you're looking for but check out Miche cassettes, they're liable to have something in the range that you're looking for and have several that start with 12t. Reliable brand at affordable pricing.

You'll find that lots of 12t cogs share those serrations and just require a 12t lockring to make it work. When I built my 10yo's bike this year the 10sp hub wouldn't fit the 12sp cassette I want to use, for obvious reasons, but I just left off the 11t and found a 12t lockring, the 12t cog had the needed interface. Seen the same with shimano and sram in the past.

tFUnK

I second the Miche suggestion. Almost went that route (I think for 10sp the road cassettes go up to 30t) but ended up piecing together a cassette with a couple replaced single cogs.

Also agree that sometimes the 12t second tooth on an 11-xx cassette is also a terminal cog. Was somewhat surprised actually, thought I had mixed up my different cassettes in my quest to put together a custom cassette, but have read that it's commonplace.

cpach

Take note of your realistic derailleur maximum cog size and capacity. You can use 9 speed Shimano mountain derailleurs with 10 speed road shifters okay, but they tend to max out around 36t. Searching apparently the Sunrace M900 is rated for up to a 51t and is 9 speed Shimano MTB compatible, so should theoretically work with 10 speed Shimano shifters (also has a clutch). You can stretch official recommendations a bit but I'd be wary of going way off spec--I might try a 40t max on a derailleur rated for 36, possibly with an extended b tension bolt. You can extend maxium cog size a little using a wolf link or similar but they affect shifting a fair amount because the distance from the guide pulley to the cassette is thrown off for the rest of the cassette.

I know you're looking for an easy hack, but for indexed shifting using matched cassette cogs really improves shifting. It's more to spend, but you'll get significantly better shifting if you pick a cassette with reasonable gear spacing (say, an 11-34) and pair it with a subcompact crank (assuming you're running 2x chainrings)with 46x30 rings or lower. If you're already using a triple, you can use as low as a 22t small ring on a pretty standard trekking triple crankset.