Bicycle Mechanics - Why did this work?

I bought an 11-28 8 speed cassette for my Ultegra equipped road bike, the shop said it should work even though it's labelled as an mtb cassette. When I put it on, there was play so the cogs moved side to side. An idea struck me, so I put the 12 and 13 from the stock cassette (12-23) on and ditched the 11 and 12. Not only did it eliminate the play and tune up fine, but I wanted a 12-28 anyway. But why did that work so well?

? that worked, impressive

Your freehub is probably not Hyperdrive-C. The splines of a Hyperdrive-C freehub don't go all the way to the end which allows an 11T to fit on (the notches on an 11T don't go all the way).

If it's working, something must be broken. :D

Your 8 speed road freehub body is probably designed for a non-compact cassette. Basically meaning it won't accept the 11 tooth small cog. The splines on your freehub body extend further out along the length of it and an 11 tooth cog doesn't have the splines going all the way through, because this would weaken the cog and make it more prone to breaking, because it is so thin to begin with. The 12 tooth cog is slightly larger in diameter, which allows the manufacturer to cut the spline all the way through and allow the cog to press up against the next one up when the lockring is tightened. The splines on the 11 tooth cog bottom out on the splines of the freehub body so that when you tighten the lockring, the 11 doesn't contact the next one up, and the cassette isn't held in place.

A permanent fix for this, if you ever want to run an 11t cog is to file a little bit of the material off of the splines on the freehub body to allow the 11 to rest against the next cog up. I did this on an alloy chris king freehub body a little over a year ago and it's been fine ever since. I tried using a spacer as mentioned in the sheldon brown article (linked below) but the lockring wouldn't get enough purchase on the freehub body threads, and wound up pulling the first thread out, so filing was the only option for me, and since it was alloy, it didn't take very long to do it by hand.

More info here (http://sheldonbrown.com/k7.html#11).

Thanks, that explains it perfectly. I'm happy with the 12 since I actually wanted a 12-28 in the first place, but was wondering about the compatibility. If I ever become a fearless descender again, I'll try that trick with the 11.

Sheldon covers it here. Just page down under the 10 speed cassettes.
http://sheldonbrown.com/harris/k7.html

I bought an 11-28 8 speed cassette for my Ultegra equipped road bike, the shop said it should work even though it's labelled as an mtb cassette.

Everyone else has covered the technical issue with the hub interface, so I'll just add that the whole "mtb casette" vs "road casette" issue is bretty much just merchandaising. What they now call a "mountain bike" range used to be called a "touring" range, and was pretty common on road bikes that weren't strictly racing machines. When "mountain biking" became more popular than "bike touring" the nomenclature changed.

As long as the rear derailler cage is long enough to take up the slack, fit the cogset that matches your riding style and rear hub, and ride it.

Oh, wait a sec. I guess that's exactly what you did. Smart move... :D

Yeah, I knew it was just a marketing thing, which was why I didn't understand why the 11-28 didn't just go right on. It all worked out better anyway, because I don't care to go over 40 mph anyway, and the 11-28 lacked a 13 which I can use.

What they now call a "mountain bike" range used to be called a "touring" range, and was pretty common on road bikes that weren't strictly racing machines. When "mountain biking" became more popular than "bike touring" the nomenclature changed. :D

Well, sort of. Touring freewheels and cassettes never had an 11 or even 12T small cog. These are common on MTB cassettes because of the tiny "big" chainrings, typically 42 or 44T, so the 11 or 12t cogs are needed to get a reasonably high top gear.

Touring bikes in the past came with 14 or 13T small cogs and combined with a 52/42/granny triple crank gave a 100 or 108" high gear which is PLENTY for touring. Unfortunately current touring bikes usually come with MTB cassettes and road triple cranks. This gives a reasonably low low gear (30x32 or 30x34) but you also get an absurdly high high gear like 52x11.

52x11 rocks! :D

52x11 rocks! :D
lol I'm on a 50/34 compact. I bought the cassette for climbing, not descending. I stop pedalling at about 35 mph anyway.

Well, sort of. Touring freewheels and cassettes never had an 11 or even 12T small cog. These are common on MTB cassettes because of the tiny "big" chainrings, typically 42 or 44T, so the 11 or 12t cogs are needed to get a reasonably high top gear.

Touring bikes in the past came with 14 or 13T small cogs and combined with a 52/42/granny triple crank gave a 100 or 108" high gear which is PLENTY for touring. Unfortunately current touring bikes usually come with MTB cassettes and road triple cranks. This gives a reasonably low low gear (30x32 or 30x34) but you also get an absurdly high high gear like 52x11.

You're quite right. I was overgeneralizing a bit.

What's so absurd about a 52x11? :D

What's so absurd about a 52x11? :D

On a touring bike with 35 pounds or more of luggage are you really going to be able to use a 52x11 anywhere?

The problem is that to get the 11T small cog, you give up a far more useful cog in the middle of the stack.