VegasJen

OK, I get that title may be a little more vague than I would like, but not really sure how else to phrase it. What my question really is, is can I put a 10-speed cassette on a hub that originally had an 8-speed cassette?

I have a spare set of rims and I'm thinking of setting up that wheel set for my TT bike. The TT bike is 2x10 and the spare rear wheel I have originally had an 8-speed cassette. What I want to do is have one set of wheels for my TT bike that are mostly for flat ground and then a second set with gears that are more for hills. So if I get a Shimano or SRAM 10-speed cassette, will it fit on the same hub as the 8-speed? Or is there a difference in the length or depth of the hubs between 8-speed and 10-speed?

KCT1986

In most cases the freehub body of 8 & 10 speed are the same. There are possibly some exceptions since many wheels have hubs that are 'Shimano compatible' but may not be 100% the same.

Cassettes may also have minor differences, and small tweaks may be needed to indexing. Cassettes also differ in how the innermost cog is designed, some are designed to slightly overhang the freehub body rear, towards the spokes.

Chain length and rear derailleur capacity are also considerations if the cassettes' tooth count differ by a large amount.

VegasJen

Ya, this may be more complicated than I'm up for. The TT bike I'm using has all SRAM gear on it, but the extra wheel set is Shimano. I have heard the two are *largely* compatible, but maybe not everything. Not sure how I would know, except maybe to take the cassette off the current SRAM wheel and compare it to the Shimano hub?

maddog34

SRAM/Shimano 8-9-10 cassette spacing is the same.... shimano derailleurs and shifters'pull ratios are different that SRAM, but move the same amount, gear to gear, within their designated count's range..

you'll be fine setting up a spare set of wheels... 8- 9-10 use the same width freehub., Sram or Shimano.. there are a few Shimano road 10sp. Cassettes that are narrower than normal, but they come with a spacer to make them fit an 8- 9- 10 freehub.

KCT1986

Shimano & SRAM both state the same dimension for right side locknut placement relative to the freehub body shoulder, (where the back of the cassette butts). See the 40.75mm measurement. This means that the cassette should be in 'about' the same place in relation to the dropout and RD.

Swapping the cassette to the other wheel will confirm that they are same or close enough. This would be a good place to start testing. A minor adjustment may still be needed for indexing.

If this checks out OK we have a good start.



Other information that would be helpful to other assisting you would be model of RD and cassette size (current & proposed). Others on here may be familiar with your shift system and what it can handle. Expect a few questions as we progress.

KCT1986

Forgot to ask for your current chainring size.

Kontact 

Shimano or SRAM - there aren't any Shimano or SRAM 10 speed cassettes that won't fit on an 8 speed Shimano or SRAM compatible freehub.

SoSmellyAir

Yes, most likely this should work. Does not hurt to install existing cassette onto spare wheel to try.

VegasJen

Cool. I'm going to start looking for a 10-speed cassette this weekend. I may take this bike with me to the Santa Barbara tri in August. I did it last year on one of my road bikes that has 3x9 gears. There were a few hills where I don't think I needed the absolute lowest gear, but pretty sure I was using lower gears than what's on this Ridley.
Not sure about the model of RD. All I know for sure is it is SRAM and the bike is a Ridley. I'll see if I can find any markings on it tomorrow.
Honestly, I'm not even sure. I haven't counted it yet. I will do that tomorrow. I just know climbing steep grades out here, I don't have enough low gear.
Awesome! Maybe I'm in business after all.
You know, I never even thought to take my existing cassette and try it on the other wheel.

t2p

many 10 speed cassette options - do you have a preference (brand / max cog) ?

not famil with SRAM 10 spd cassettes - but famil with Shimano 10 spd

I believe the Tiagra cassette (CS-4700) is avail in sizes you might be interested in - including 12-28, 11-32, 11-34

XT (CS-771) cassettes will be a little better quality / lighter - in 11-32 and 11-34 (11-36 prob not going to work on your bike)

HG-500-10 cassettes also another Shimano option - 12-28, 11-32, 11-34

again - not famil with SRAM 10 spd ... could be more / better options ... ???

CliffordK

In general that is all true.

SRAM came out with the XD freehubs which are very different from Shimano. However, those may all be 11 and 12 speed.

Black wallnut 

IME, if your current cassette is Sram and indexes correctly then you should use a Sram cassette on your other wheel. Yes it will fit and yes it will be spaced the same. I have had issues mixing wheelsets with both brands of cassette.

icemilkcoffee 

I am surprised nobody mentioned the caveat, that the older 8 speed freehubs are incompatible with 11T small cogs. If the splines go all the way to the outer end of the freehub, it will not take an 11T small cog. If the splines stop short of the end of the freehub, then it can take 11T.

SoSmellyAir

With respect to indexed shifting, I suspect that the difference between one rear wheel and another rear wheel to have a greater effect than the difference between a 10-speed Shimano cassette and a 10-speed SRAM cassette.

VegasJen

So I spent a little time playing with the bike today. I was able to pull the SRAM cassette off the original wheel and it fit right on the hub of the other wheel, so I think I'm good to go there.

Now, on to the topic of gearing. The original is a 10-speed cassette with 11 on the small gear and 25 on the large gear (I didn't bother counting teeth on the gears in between). For the spare wheel, I think I probably want 30(?) on the large gear. I imagine this should get me noticeable improvement on my hill climbing ability. And then if I only go up to 12 teeth on the small gear, I don't imagine that would make a huge impact on the top end. But I haven't even started shopping yet, so not sure what's available to me.

As for the RD, the only thing I saw on it was "Red". I don't know if that's their model or what. I didn't see any model number, but not sure where to look either.

VegasJen

Just did a little shopping on Jensen and found a couple options. Shimano has a Tiagra that's 11/32 for $35. That seems very reasonable. I did look a little higher and SRAM has one that's 11/32 and Shimano has an Ultegra that's 12/30, both are right about $65.

My concern is just a matter of interference with the RD running a much bigger gear. I don't know how I would even check that. Also, something I thought about is, will swapping to a larger gear set also require a longer chain? If so, how do I determine that?

Black wallnut 

With multiple bikes, some with Shimano 105 some with Sram Apex, Most wheelsets were fitted with Shimano cassettes. The Shimano cassettes all worked without derailleur adjustment with all 105 bikes. They did not work with any Sram groupset bikes without poor shifting but the wheels with Sram cassettes worked fine with Sram. My experience. Yours may be different. If you train with Sram and want to race with Shimano make sure to properly adjust shifting before race.

Kontact 

This is likely because of the freehub location, not the cassette brand. You fix it with a spacer under one of the cassettes.

KCT1986

Yes, Red is name of the group. There are different model years that may have various options, (short or mid cage length).

Post a pic of the RD and hopefully someone here will ID and know the max tooth count and total chain take-up capacity.

Also provide chainring tooth count so we know how much chain take-up is needed.

Depending on the current chain length, a longer chain may be needed. Maybe post a pic of the RD while in the big ring and biggest sprocket.

At least the cassette fits on the freehub, that's a good start.

Black wallnut 

Real world experience Kontact. Shimano 105 hub, Shimano 105 10 speed cassette with the spacer does not shift correctly when placed in service on several Sram equipped bikes but from bike to bike with Shimano shifts just fine. Likewise Sram on Sram works fine.

My bikes were (are) 105, my son's bikes were Sram Apex and Rival. I had spare wheelsets he didn't Some of my spare wheelsets were whatever came on my Specialized bikes fitted with Shimano cassettes. Others were wheels with 105 shimano hubs and cassettes. None of my spares shifted correctly on his bikes that shifted fine with Sram cassettes. I never tried the reverse, didn't need to. Spacing is the same, placement likely is slightly different between brands, just enough to need adjustment for perfect shifting. Won't speculate about higher level cross compatibility.
.
Moral of the story for VegasJen, is $5-$10 savings worth the hassle of adjustment every time you change wheels? If you stick with one brand across all wheelsets for each bike your odds of everything lining up every time are greatly increased.

SoSmellyAir

There is also 12-28. For example:

Shimano CS-HG500 Cassette - 10-Speed, 12-28t, Silver Cassettes | Worldwide Cyclery
SRAM Pg-10500 Speed Cassette | Jenson USA

Rear derailleurs have two specifications: (1) largest cog; and (2) chain wrap. If you post a photo of your rear derailleur, preferably one showing the model number, someone here who runs SRAM Red would know how to look up those two specifications.

Yes, you will most likely need a longer chain to run a larger cassette. A chain is usually sized (i.e., cut down to correct length) so that it would allow the simultaneous use of the biggest chain ring and the biggest cog with very little slack, such that it would likely not work with a larger cassette.

SoSmellyAir

So many bikes sharing so many wheels, and with a mixture of Shimano and SRAM cassettes too; how promiscuous!

Kontact 

My real world experience as a professional mechanic is that there is no difference - as long as the cassettes are located laterally the same. Which I mentioned and you didn't address.

If the Shimano cassette mounts 1mm closer to the spokes than the SRAM, that will make all of your cogs off by 1mm. Put a 1mm spacer on the freehub, suddenly everything works perfectly.

30+ years of "real world".

VegasJen

As requested.



The front chain ring is 53/39.

And as long as we're on the subject, how do I identify this chain? I mean identify it for the correct replacement. Yes, it's dirty, but it's not in bad condition - yet. But I would like to have a spare on hand, and if I end up getting that larger cassette, I will likely need a longer chain anyway. All I have found on it is the "IF". Otherwise, nothing else that might tell me what size it is.

SoSmellyAir

Any 10-speed chain should work, but some believe that matching cassette and chain brands allow better shifting; since you are buying both a new (larger) cassette and a chain, you might as well buy a matching chain.

No SRAM experience here but both (a) your photos above -- which show a relatively short RD cage -- and (b) your prior mention of an existing 11-25 cassette suggest that (1) your current RD has a short cage and (2) you will need a new RD with a medium cage to run a cassette with a largest cog > 28T.

RED Rear Derailleur 10-Speed | RD-RED-B1 | SRAM

(An SRAM Red RD but may not be exact RD you have; included just for reference to 28T max cog size.)