Am I being thick?

[cherrybomb]

) :?

I've got an XT rear hub with an 8 speed free hub that I want to fit a 7 speed cassette to.

I've got a modern Shimano 7 speed cassette (cheap! ) and a couple of spacers, one alloy and one plastic.
One spacer isn't enough and two are too much??? :?

Any ideas as to what I'm doing wrong?? are new 7 speed cassettes 9 speed spacing or summat??

Confused of Shropshire.

 

[The Ken]

I have a modern Hope hub (8 speed) with a shimano hg70 cassette 7 speed , fits ok with one hope brand alu spacer but seems really close to my frame (I had 6 speed before that).

Took ages to get the derailer to shift properly though.

Can't think what you are doing wrong....but just in case the spacer goes on the inside of the cassette with the slots lining up with the little bolt heads on the cassette side.

 

[cherrybomb]

Hummmm.

Cheers for that.

How wide are the Hope spacers? The ones I've got are about 2mm.

I reckon I need about 3mm. I'm considering sanding the plastic one down if I can't work out what's going on.

 

[Stick Legs]

The profile on the inside of the bottom sproket has changed recently. (3 ways I have tried to get around this below).

This means that you are tightening the bottom cog onto the free hub, but it will only go so far and not allow the bottom cog on far enough to tighten the whole cassette.

I used a wibbly metal spacer from an old cassette which was just thick enough to allow it to tighten up. You could also substitute the bottom cog for an old worn out 12 and then build the cassette up as a 12 12-28 but the bottom 12 is just a spacer and the 12-28 becomes the 'block'. This would of course mean building a custom cassette, which if you have lots of spares is easy.

The other option, if your bottom cog from the old cassette is not too worn is to put that at the bottom of your new cassette and use it that way.

Of course you could just buy a new freehub body, which will make life much more easy going forward.

 

[Stick Legs]

Sheldon has the answers:

Read the bit about Hyperdrive C and you will see why it doesn't fit...

http://www.sheldonbrown.com/k7.html

 

[cherrybomb]

Thanks for that.

I don't have an old cassette unfortunately, so no access to wobbly washers or old 'bits' to cobble something together.

I'd like to avoid having to buy a new freehub if I can, but if it comes to that; I'll have to I suppose. :cry:

 

[Stick Legs]

I'll try and root out a pre hyperdrive C 12t bottom cog for you. It should work then.

Can you re profile the freehub as sheldon suggests?

 

[cherrybomb]

That would be great if you can.

I can have a bash at re profiling the freehub, seems I need to take the ends off the splines, or I can try to reduce this plastic spacer a bit.

i'll have a bash when I get back to the bike on Sunday. :roll:

 

[Stick Legs]

I would leave the plastic spacer alone, you will only confuse yourself later and put it between 2 cogs, then wonder why your indexing has gone to the dogs.

I have not got a spare pre Hyperdrive C 12t (or a wibbly washer). The depth of the plain end on the later cassettes is 1.8mm, I would measure this, put some tape around the cassette at the 2mm point and carefully shave back the lugs.

Cheers.

 

[jonnyboy666]

hey guys, ken has the best solution, the hope spacer is available for about 2 or 3 quid, any shop who does alot of hope bits will have their tackle boxes and they are in them. i keep them in stock and they work perfectly, they sit behind the cassette and line up with the cassettes bolt heads or the rivets depending on the model of cassette, i'd recommend the hg70 models but they should work on any model. fyi, the spacing on 7 and 8 speed cassettes is the same but the 8sp freehub body is longer than the 7sp version, then if you want 9sp you can use the 8sp freehubs aswel coz the 9sp cassette has narrower sprockets and spacers giving the same overall width as 8sp cassettes so you can mix 7 and 8speed shift levers and cassettes but not 9sp shifters on 8sp cassettes etc. hope that all makes sense.

god, i love this site, makes me feel like all the crap that's built up in my head could be worth something after all! i'm all excited, my first post!