roth rothar

I bought a pair of 26 inch wheels and tires at the local flea market for $10. The front wheel and tire are fine as is and just need the bearings greased. The rear wheel is also in good shape except it has a 7 speed cassette and does not have quick release skewers. My bike is 8 speed. The flea market wheel Hub is a Shimano FH-CT30 36 spoke.

In my spare parts box I have a brand new FH-RM30 hub for 32 spoke wheels, this hub is compatible with an 8 speed cassette and has quick release skewers.

My plan is to take the cassette body, axle etc from the old FH-CT30 hub and leave just the hub shell on the wheel. I am hoping I can then transfer the new FH-RM30 cassette body axle and skewers to the old hub shell.

If successful I will have a quick release wheel with 8 speed compatibility.

Comment’s please

70sSanO

I have not done that particular swap. Basically Shimano freehubs have a deep or shallow recess and freehub bodies to match. Most seem to have a deep recess. If they match things are pretty easy, if not creativity is a plus but not a guarantee.

Firsr step is to make sure the axle diameter and threads are the same.

If the swapped freehub body fits the 7 speed freehub, you just have to transfer the axle, DS cone and seal.

What I do when mix-n-match with different speed freehub bodies is to set the DS locknut to freehub body to get the chain clearance to the dropout. When going from 126mm to 130mm to 135mm, or vice versa, this can be a balancing act. If they are both the same OLD it is pretty much just moving the DS over and letting the NDS fall where it may. So you may need to change the NDS spacers/washers.

There is a good chance you will need to re-dish the wheel.

John

Bill Kapaun

Most likely NOT-
The FH bodies from that era have a different spline arrangement in regards to hub attachment.
Look at the 2 pdf's I've attached (couldn't find your specific model) and see if your CT has the same type.

Retro Grouch 

What do you have to lose? My general philosophy is, if I already own parts, I'll try to bolt most anything up and see if I can get it to work.

I won't argue with Bill Kapaun, but I've mixed and matched several 7 and 8 speed freehubs and never encountered the freehub spline issue he mentioned. If that's the case, it will be pretty obvious.

I would make an effort to keep all of the axle set items, cones, locknuts and spacers together on the axle they came on.
I'd plan on redishing the wheel too. I'd start by loosening all of the non-drive spokes 1/2 turn. That will make it easier to tighten the drive side spokes 1/2 turn. Repeat as necessary.

70sSanO

I have to agree with Bill that the RM-30 FH body will not work. It is an odd duck with the external splines. Not a snowball’s chance.

You can probably take your CT-90 and use the QR axle from the RM-30 if the threads match. If you decide to swap freehub bodies one day, take your 7 speed off and re-lube it, take pics and at least you’ll know which type to look for. Also, be aware that Shimano changed the seal diameters over the years, so a complete freehub is preferred to just getting a freehub body, plus you’ll need the DS cone.

John

Bill Kapaun

Both FH bodies should be removable with a 10mm hex wrench.
As mentioned, you want to keep the cone, seal etc. with its specific FH body.

BTW- I built 3 wheels with the RM-30 hub. It's crap!
The cones have an "oxide" finish instead of being polished.
All 3 eat DS cones.
You'll want to add grease & adjust the bearings if your RM-30's are like mine.

roth rothar

Thanks for all the replies. I found that what I thought was a FH-CT30 was actually a FH-CT90 , thanks for the pdf files. It looks like I will need to buy a new Freehub body to be compatible with the shell on the wheel and be 8 speed. I will give it a shot.

70sSanO

Just to give you an idea of the shallow and deep shoulder freehub bodies. Left are shallow and right are deep. Top are 7 speed, bottom are 8 & 9 speed (technically will fit 8-10 speed cassettes).




Good luck!

John

Bill Kapaun

I found a 6 AND 7 speed version of the CT-90 with docs attached.
I'll let you ponder the different part numbers

roth rothar

Thanks
It looks like 3 of the 4 pics have a threaded portion and the last one does not, I am puzzled

70sSanO

The first Shimano cassettes were called Uniglide. They were similar to most older freewheel systems in that the first position cog threaded onto the freehub body. The cog teeth were twisted and not ramped (with varying teeth shape to assist shifting) like Hyperglide cassettes.

When Hyperglide cassettes were released in the early 90’s, they needed to be specifically oriented to each other for the best shifting and one of the splines was wider so everything was aligned. To do this the first position cog was no longer threaded, but slid on the freehub body and everything was held in place with a lockring.

For a few years, Shimano manufactured Uniglide/Hyperglide (UG/HG) freehub bodies that had both the external thread, the wider slot, and inside threading for a lockring so both a UG/HG cassette could be used.

In the mid-90’s, or so, Shimano eliminated the external thread and added a slight section at the end of the freehub body as relief to allow smaller 1st position cogs down to 11t.

They also hollowed out the spline section and used two ribs, probably to reduce weight.

John