Athens80

We have a ten year old hybrid permanently stationed on the direct drive trainer. It's an 8 speed with SRAM SX5 thumb shifters and SRAM SX5 rear derailleur.

The RD may be on its last legs. It's the metal; it's on the flimsy side. I've bodged a repair, but the next time, short of a machine shop, it may not be worth dealing with.

If I need a new RD, I'd rather get a 10 speed RD and replace the shifter as well. IIRC, the spacing, etc., would accomodate 10 speed. I have a 10 speed wheel I could use, but really don't need to do anything there other than replace the 8 speed cassette on the trainer with a 10 speed. It'd be a plus to have 10 cogs on the trainer, but this bike rarely goes outside.

But what would I buy today to get a 10 speed shifter to clamp on the hybrid handlebar, and what RD would go with that? Weight does not matter. Appearance does not matter much. Smooth shifting and reliability are good.

Or is the original FSA crankset on the bike only suited for an 8 speed chain? I don't picture wanting to go to the expense of getting a new crankset.

dvdslw

Depends on your budget, there's tons of options out there. Looks like mtb shifters and derailleurs are quite a bit less than the road stuff so maybe Shimano Deore, SLX, Saint, or Zee would work for you? If you want road components, there's some Tiagra flat bar shifters that'll work with any 10 speed "road" Shimano rear derailleur. Sram has several options too, really need to know what your budget is to help you.

Athens80

Budget - under $100

dvdslw

Over at Jenson, you could get a Shimano M670 SLX rear derailleur, M640 Zee right shifter, HG54 chain, and HG500 12-28 cassette for $85.96 delivered. I'm sure there's other combos out there but Zee and SLX have pretty crisp shift quality for the price.

Chain $15.00
Shifter $22.99
Rear D $19.99
Cassette $26.99

Athens80

Thanks!

Would I need to buy only the shifter and derailleur? I've got a 10 speed Shimano road cassette that came with the trainer, and I've got a Shimano 5701 10 speed road chain. Would those work with the Shimano M670 SLX rear derailleur, and would the 5701 chain work with the original FSA crankset (for 8 speed)?

dvdslw

I know the chain and cassette should work just fine but not sure about the chainrings on the crank? If you're only having to purchase the shifter and derailleur, your budget would certainly allow swapping out the 8spd rings on the crank to some budget 10 speed rings?

f4rrest

When I went from 9sp sora to 10sp ultegra, I only needed shifter, cassette, and chain.

The 9sp cranks, FD, and RD worked as-is.

I don't know if the same applies to 8sp vs 10sp, but you could try piece by piece.

Athens80

Thanks y'all. The RD held together today. I'm not in a hurry until it falls apart again, but now I've got a plan and a shopping list.

When I was thinking I might need to buy a replacement RD, I found the OEM SRAM SX5 is no longer a current model. And then I figured, if I need a new derailleur, why not spend the money on a higher capacity one.

Now I wonder why I didn't think of going 8 speed to 10 speed before. I've already got most of the parts. I'd have finer gear intervals with 10 cogs. And it'd be practical to swap my road bike onto the trainer from time to time, if I kept a 10 speed cassette on the trainer. The 8 speed on there now is suitable only for the hybrid (which works for both of us). We use the trainer a lot and it's very convenient to have minimal to no delay in getting ready to ride.

Racing Dan

That is not always true. Most 10 and 11sp cassettes start with a 11t cog that is seldom (if ever) used. An 8sp cassette can be had with a 13t small cog. IMO an 8sp 13-26 is every bit as good as an 11sp 11-28 bar the bottom and two top gears. The trick is to figure out if the extreme ends are needed or not. For 99% of my riding the 8sp would be every bit as good as the 11sp and much cheaper too.

Athens80

Good point. My current reality is that I have a SRAM PG850 11-28 on the trainer now, picked up from the LBS a few months ago. If I went to 10 speed I have a Shimano 12-27 in the home parts box.

On sram.com I see that the PG850 should be available 12-26 and 12-23, with smaller gear intervals than what I have now.

Shimano.com lists 12-21, 12-23, and 12-25 options for the CS-HG50-8 cassette. I didn't look for Shimano at the LBS when I bought the cassette some months ago because I didn't think that 8 speed Shimano was compatible with the rest of the SRAM drivetrain -- but I don't know much about mixing and matching components.

I do see 13-26 advertised at online retailers -- maybe that's an older option still in stock.

ThermionicScott 

Yep, 8-speed 13-26 is a good way to go, especially for trainer duty. Still being made, and cheap: https://www.universalcycles.com/shop...17&category=42

VegasTriker

Why not take the time to do some gear range calculations using either the Sheldon Brown gear range calculator or the one by Mike Sherman. If you plug in the values for your drive system and the proposed revisions you can get an idea of what difference the changes will make.

Mike Sherman's Bicycle Gear Calculator
https://www.sheldonbrown.com/gear-calc.html or