changing sprockets on 7 speed Freehub

[buzzy-beans]

The rear Mavic wheel on my delicious bike is fitted with a 7 speed Freehub, however the 13 to 19 tooth allied to a 52/42 chain ring gearing is utterly stupid for my 68 year old legs and try as I have, I simply can't get on with it.

The problem appears to be the age of the splined Freehub which I must point out is in superb condition and has the quietest ratchet I have ever heard and even on the bench it spins forever.

There is no lock ring, all the cassette is held on with is simply the smallest threaded sprocket, so do any of your very helpful and knowledgeable people know where I can obtain either a full cassette or individual sprockets from? Plus also, from my description what is the definitive name of such a cassette?

Many thanks for any light any of you can shine.

 

[DCLane]

It sounds like it's a freewheel. Not sure what you have but a 14-28 is easily obtainable. You can also get a 'Megarange' one which is 13-34 but in reality the 28 is swapped for a 34 so it's a very big jump.

Others are available (i.e. 13-28, 11-28) but are pricier.

 

[iluvmybike]

It'll not be a freewheel but a shimano uniglide cassette where the smallest sprocket is used as the lock-ring. The pre-dated the type of cassettes we are now used to. You need two chain whips to remove it. I don't believe u can buy uniglide cassettes nowadays - so you might be looking at re-building the wheel with a different hub unless you can find some new sprockets on a vintage website

 

[Tim Hall]

It'll not be a freewheel but a shimano uniglide cassette where the smallest sprocket is used as the lock-ring. The pre-dated the type of cassettes we are now used to. You need two chain whips to remove it. I don't believe u can buy uniglide cassettes nowadays - so you might be looking at re-building the wheel with a different hub unless you can find some new sprockets on a vintage website

Can't the OP fit a Hyperglide freehub body in place of the Uniglide one and then a 7 speed cassette to suit that?

 

[lazybloke]

My 7 speed hub will take uniglide or hyperglide cassettes.
I think this page covers the differences.

EDIT: If it doesn't have 'dual compatibility', do what @Tim Hall says.

 

[buzzy-beans]

Thanks for all of your thoughts.

I have been pondering this problem for quite some time and actually bought a cassette which I had hoped was the correct type, however of course it isn't as it needs to be fitted with a locking ring and furthermore the new sprockets have one locating lug which is different, however the diameter is perfect.

Knowing this I started doing a search on Youtube and came across this easy modification that I most certainly have all the tools to undertake
View: https://www.youtube.com/watch?v=on1qxTCf2dE


The only problem being that I will have to use the existing (and perfect condition) 13 tooth screw on socket in place of the 12 tooth one from the new cassette, mind you if it did work, I can always buy a replacement 12 tooth sprocket of which there are quite a lot to be found on eBay.

Many thanks once again.

 

[Ajax Bay]

I think the OP might find this article - Uniglide-and-hyperglide-compatibility - worth reading.
OP is both pleased with and proud of his current freehub (Uniglide).

An oblique approach to this maybe to replace the crankset with a 110mm BCD and a smaller pair of rings or a compact (50-34).
Still doesn't solve the need for some reasonable low gears: a 50/34 and 13-19 corncob setup gives them a 48" low gear.

Hyperglide cassettes will slide onto Uniglide freehubs (the main difference is that one of the HG splines is narrower) [edit] but a bit of grinding is required. To secure the cassette, a screw-on outer sprocket is still needed to screw onto the Uniglide hub (see the article I linked above for images). After buying a 7 speed HG cassette eg this 13-26 one (or even a cassette starting with a 12t), the OP can take their current 13t sprocket (with its thread) and replace the 13t on the cassette with it, [grinding complete] slide 6 sprockets on and secure the cassette with the 13t.
Climbing a hill using a 26t sprocket will be a darn sight easier than with a 19t!
I have not done this but believe it would work. What do others think?
OP has just posted effectively preempting this (latter) advice - Ha Ha!

 

[buzzy-beans]

Success, I decided not to use my dremel and instead used a new small diameter chainsaw file followed by a small square file to file away the excess metal of the larger locating lug, of course making absolutely certain that I was filing the lug from the correct side.
It only took me approx 15 mins. of very careful filing to get the offending lug down to exactly the same size as the others and bingo, it slipped perfectly into position.

Now with everything back in place, all I need to do now is to work out what length chain I need.................... any ideas?

 

[raleighnut]

Success, I decided not to use my dremel and instead used a new small diameter chainsaw file followed by a small square file to file away the excess metal of the larger locating lug, of course making absolutely certain that I was filing the lug from the correct side.
It only took me approx 15 mins. of very careful filing to get the offending lug down to exactly the same size as the others and bingo, it slipped perfectly into position.

Now with everything back in place, all I need to do now is to work out what length chain I need.................... any ideas?

Dead easy, wrap the new chain around the big-big combination (without going through the rear mech) and allow 2 pairs of links to 'overlap' then break to that length.

 

[andrew_s]

Replacement uniglide cassettes are now very rare, and those you may find are likely to be both expensive, and narrow range (like your 13-19).
When your original Uniglide sprockets get worn, you can break up the cassette by removing the rivets or bolts that hold it together, and reverse the sprockets so that chain runs on the other side of the teeth. Either use loose, with the threaded sprocket properly tight, or refit the bolts/rivets.
Hyperglide sprockets can't be turned in the same way, and also wear quite a lot faster than uniglide (twice as fast, by my memory).

If you end up using several hyperglide sprockets loose, take care to align the filed down splines with each other.

Can't the OP fit a Hyperglide freehub body in place of the Uniglide one and then a 7 speed cassette to suit that?

Shimano 7 speed freehub bodies are available, but I wouldn't expect them to fit a Mavic wheel. Shimano freehub bodies fit using a hollow bolt (10 mm allen) that the axle passes through. Compare the SJSC pictures with your hub to decide if it looks like it will fit.

 

[GuyBoden]

I'd change the hub body to Hyperglide if you can, makes things easier...........

I've got a few old used Uniglide cassettes in the garage.

 

[andrew_s]

eBay asking prices seem to be starting at about £40-50, for corncobs.
Anything larger than 24T seems to have been broken down and is up for sale as individual sprockets at up to £20 a go, presumably depending on size.