Convert a 7 Spd STX free hub to 8spd
 

Picked up a 90's Giant CFR Three carbon fiber road bike. Came with the OE STX drivetrain. Original except Shimano 8 speed STI Flightdeck shifters have been substituted for the original 7 speed shifters. The rear wheel is still the 7 speed STX hub and cassette. The 8 spd Flightdeck setup shifts well with an 8 spd rear wheel from another road bike. I'd like to switch the STX OE freehub out for an 8 Spd freehub.I have a possible 8 Spd donor hub. It's a Shimano FH-RM30 made in China 8 speed hub. I'm wondering if that 8 speed freehub is compatible with the 90's STX rear hub.

NO!
The spline pattern between the FH Body & Hub is totally different.
The RM-30 in general is crap. I built a couple wheels using it and it tends to eat DS cones.
These cones have an "oxide" finish. Not polished like better quality hubs.
IF you provide the exact model# I may have that pdf.

I'm no expert on swapping freehub bodies, but I've done a few.

I know of 3 three late 80's and 90's freehub body attach styles (excluding Dura Ace). I've seen a flush, a shallow, and a deep shoulder recess. You need to remove your STX freehub body and take a look at the freehub shoulder and freehub body.

Here is a pic of the shallow and deep shoulder recess. The left is a shallow with a square shoulder edge. The right is a a deep with a beveled edge. I've swapped 7 to 8 and 9 to 7. You do need to find the correct DS cones for the freehub body.

https://cimg7.ibsrv.net/gimg/bikefor...f23d1364dd.jpg
Shallow (square) and deep (beveled) freehub bodies...

https://cimg1.ibsrv.net/gimg/bikefor...877eb5efd5.jpg

John

And note the RM-30 is very different from those shown above.

Don’t you mean RSX? That is the 7 speed road groupset. The STX is a mountain bike groupset.
Why don’t you replace the incompatible 8 speed brifters with 7 speed brifters?

I'm sure ur right on the group type. My garage lighting isn't the best. My only STI 7 speed shifters are 105. They are new almost new. A little too nice for this bike. Thanks for the comment.

Thanks Bill. That helps.

The 105 shifters are 8 speed shifters. They don't work well with the 7 speed cassette. You will need to look for RSX 7 speed shifters on Ebay. Alternatively, if you are wary of old parts, you can buy new Micronew 7 speed shifters or Shimano Tourney 7 speed shifters

The bike is solid but cosmetically a little rough. It originally had 7 dt shifters. The NOS 105 brifters have been sitting in my drawer since the 90's and are AFAIK 7 speed. Maybe I need to look at them again. My simplest is to use some 8 speed wheels. Don't want to spend on this project. Thx

I don't think those 105 brifters are 7-speed as I'm pretty sure the first 105 STIs were 8-speed. I built up a 1996 Litespeed Catalyst with a 105 triple STI group and they were 8-speed.

If you have NOS 90’s brifters, you need to know they are a highly sought after component. But how you use them is up to you.

John

https://cimg0.ibsrv.net/gimg/bikefor...6e7beae789.jpg
The cheap 8sp RM-30 is on the right; on left is a 7 eg LX or 105 etc.

The cheapest thing to do would be to take that 8 speed cassette, leave out one cog, and install it onto the existing 7 speed hub on that bike. Now you can proceed to use that 8 speed 105 shifter. You will only have 7 speeds but the spacing will be correct to use with that 8 speed shifter.

You can find an appropriate 8sp fh body but best price I see is $25-$30. I accidentally bought the new RM-30 on $10 price without looking closely.

Thanks for the tip. Yeah, I've seen them with a high asking price.

I should look at the cassette that came with that bike. It did seem to shift OK on my test ride around the block. Maybe that mod was already done. . Thx

Followup: I took your suggestion. I pulled out an 8 speed mountain cassette and removed the 32 tooth sprocket. Put the remaining 7 sprockets on the hub. Boy do those Flightdeck shifters do smooth job of shifting. Thanks to all