9 speed on a 7 speed frame

[Mr Pig]

I've got a full 9-speed transmission for sale and a guy at work is thinking about putting it onto his 7-speed MTB. Obviously the drop-outs will need widening a bit but are there any other things that will/might be a problem?

Thank you in advance :0)

 

[e-rider]

a lot of older frames that had 7 speed set-ups also had 135mm dropout spacings so there would be no need to widen it - you should check this out though and if it's less than 135 my advice would be not to bother.

the rear hub (and therefore wheel) will probably need changing - otherwise if you have the COMPLETE 9 speed system it should work OK

 

[e-rider]

oh yeah, you should check the front mech clamp diameter and whether it's top or bottom pull

 

[RedBike]

If the dropouts need to be widened then I would forget all about changing over. However, I doubt that they will. I would expect them to be the standard 135. Very few MTBs aren't.

Front mech/ bottom bracket might be the wrong sizes.
You'll need a new rear wheel.
You're probably going to have to use a new chain, and therefore possibly a new cassette.

 

[spence]

You're probably going to have to use a new chain, and therefore possibly a new cassette.

In that case possibly new rings...................... I don't understand buying 2nd hand drive train components. Mechs/shifters may be, but the (possible) wear on the cassette/chain/rings will always be an issue.

Not saying yours are worn

 

[Mr Pig]

I've bought a whole bike off my mate, because I want the Deore/Mavic wheels for my son's bike, so the rest of the bike is no use to me. The cassette/chain/rings will all be worn, I don't know how much yet as I've not checked them, but if the lot are kept together it'll work fine.

I didn't think of needing a new wheel, yeah of course he would because it'll be a different cassette mounting. Doh!

 

[NickM]

You can install a 9-speed freehub body on a 7-speed hub and it will work, but the various seals and grooves are unlikely to line up with each other, so the setup won't keep the crud out of the bearings terribly well. Probably better to buy an inexpensive 9-speed hub and hope that the rim and spokes can be re-used (especially given the price of replacement freehub bodies...).

 

[Mr Pig]

Nine and eight speed hubs are the same arn't they? I have an eight-speed hub that I could use.

 

[NickM]

Yes!

Mind you, the bike you bought from your mate sounds like a candidate for singlespeeding if ever there was one...

 

[Mr Pig]

the bike sounds like a candidate for singlespeeding if ever there was one...

Naa, I bought it for the wheels. It's a light bike though, it's a Carrera something-or-other. The frame is of no use to me. I'll stick it up for sale on here just in case anyone wants it, but I doubt it.

My son's bike, my old bike, is an older Hardrock, one with the round tubes, and it's a really light bike. It was great when you were going cross country with it as you could just hold it above your head with one arm when you were climbing fences.