7spd to 8spd conv. Question
 

I currently have a 7spd rear derail (along with 7speed set) and I bought a used 8speed cassette, is there anyway I can run this new cassette?

Use my 7 speed spacers and run only the first 7 cogs of the 8 cog set I have? (Both Shman)

Thanks,

-Robby

The spacers between the cogs are a different thickness. Your 7 spd shifters will not work on an 8 spd cassette.

ok, what if I use my 7spd spacers with only 7 out of 8 cogs of the new cassette?

If you want to do that, just buy a 7 speed cassette. They are readily available. Running 7 of 8 cogs from an 8 speed cassette wouldn't work anyway because the first two cogs have built-in spacers.

As for buying a used cassette, I hope you didn't pay too much for it. Depending on how many miles it has, it will either slip when used with your existing chain or slip with a new chain. 7/8 speed cassettes can be had for less than $30. Buying used is false economy.

Ah thanks!

It wasn't much at all, no loss

It won't fit on your 7 speed hub

take the 8 speed cassett apart and slide 7 into your 7 speed hub. you will need to use the 2 smallest ones but the other you can still use in combination. if the cassett is held together you will need to unscrew or grind off the pins holding them.

you can only use 7 of them.

My friend uses 8 speed shifters with a 7 speed block. It works. When he has more money he'll have a better setup.

^^

That's more what I was thinking was possible

thanks for the info guys!

I'm sure my post count will get large with time!

i have 5,000 and 2,000 on my car forums :notamused:

It's true that you can make it "work", but it will never shift great. You'll have to set the rear derailler adjustment to be centered on the middle cog of the stack and then deal with small errors as you shift up and down. If you can live with that to save $20 on a new 7 speed cassette, go for it.

okay here is another option, change out your 7 speed freehub body to to a 8/9 speed freehub body. (you will need a new axle also). now you can use the full 8 speed cassette.

cheapest way to do this is get yourself a donor rear hub. after that all you need is a new set of 8 speed shifters.

And redish your rear wheel.... :rolleyes:

Redishing isn't that hard, though it's likely outside of the skill level of the OP. Finding a compatible freehub would be the biggest problem unless it's a Shimano hub.

you are right the OP never mention if it was a shimano hub. Unless is shimano, it might not be cost effective to do this type of hub transplant.

you might not need to redish, I was able to get the rim centered by adjusting the washer positions.