Tourney 8 speed sprocket on a Rm40 7 speed freehub

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Dr pepper
Posts: 59
Joined: 29 Jul 2020, 11:41pm

Tourney 8 speed sprocket on a Rm40 7 speed freehub

Post by Dr pepper »

I have a tourney 12-32 8 speed hyperglide sprocket which I got by accident.
If I remove the last gear (12 tooth) which is a seperate item the thing seems to fit on my shimano Rm40 7 speed hub, the lockring nips up tight.
I know this is probably a franken type setup, however is this a dodgy thing to do or just a kludge.
Tompsk
Posts: 195
Joined: 6 Nov 2014, 9:35am

Re: Tourney 8 speed sprocket on a Rm40 7 speed freehub

Post by Tompsk »

Dr pepper wrote: 13 Oct 2021, 8:38pm I have a tourney 12-32 8 speed hyperglide sprocket which I got by accident.
If I remove the last gear (12 tooth) which is a seperate item the thing seems to fit on my shimano Rm40 7 speed hub, the lockring nips up tight.
I know this is probably a franken type setup, however is this a dodgy thing to do or just a kludge.
This a fairly standard thing to do, see Sheldon Brown's pages and I've done similar on several bikes. 9 sprockets of 10 speed cassette on a 7 speed freehub usually works too. As long as the lock ring screws on tight with at least 2 turns you should be ok but check tightness every so often if the smallest sprocket has no serrations. 8 speed spacing is very close to 7 speed so in your case a 7 speed gear shifter should be ok - worked fine for me.

Edit: Typos
Dr pepper
Posts: 59
Joined: 29 Jul 2020, 11:41pm

Re: Tourney 8 speed sprocket on a Rm40 7 speed freehub

Post by Dr pepper »

Thankyou,
Yep seems to fit fine, theres a 1/4" of thread engagement, I'll use some loctite blue threadlock as theres no locking profiles on the smallest gear, I might have a thin locktab for a disc brake adaptor that could be made to fit.
Sheldon's page states all shimano of this era has 5mm spacing.
I got a new freehub off ebay and found its used, no wear but definately been fitted, I cleaned it up & put it on didnt fancy trying to find another.
An interesting thing I gleaned from sheldons page is I could probably use an 8 speed freehub with a spacer.
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