12 speed compatibility

[Captain Scarlet]

Hello, I’ve recently bought new a Giant TCR with 105 Di2 12 speed group set.

I’m looking to upgrade the wheelset to something a little nicer than the stock PR-2 wheels. I’ve seen a set for sale in new condition, running Hope RX4 hubs. Would anyone here have the knowledge to confirm whether they are 12 speed compatible. It may be a typo as the RS4 hubs say 9,10,11 compatibility.

Some post I’ve seen on the web say 12 speed Shimano is backwards compatible with 11 speed hubs.

Please help 😬

 

[13 rider]

I pretty certain I've read that 11 speed Shimano hubs are compatible with 12 speed cassettes .

 

[wafter]

I pretty certain I've read that 11 speed Shimano hubs are compatible with 12 speed cassettes .

I'm not sure this is the case - IIRC all 8-11sp Shimano hubs are HG-standard (perhaps one might retrospectively call it "fat-spline") while I think they brought in a new standard ("Microspline") for 12sp drivetrains; the two not being interchangeable as far as I know..

 

[13 rider]

I'm not sure this is the case - IIRC all 8-11sp Shimano hubs are HG-standard (perhaps one might retrospectively call it "fat-spline") while I think they brought in a new standard ("Microspline") for 12sp drivetrains; the two not being interchangeable as far as I know..

I upgraded from 11sp mechanical to 12 speed Di2 and didn't need a new hub or wheel so I pretty sure the cassette are designed to be interchangeable

 

[wafter]

I upgraded from 11sp mechanical to 12 speed Di2 and didn't need a new hub or wheel so I pretty sure the cassette are designed to be interchangeable

Cheers - I guess that's about as conclusive as you can get

 

[wafter]

Well, that isn't at all brain-meltingly confusing...

 

[13 rider]

To be fair to Shimano they are quite good at providing retro compatibility in there designs, it does say on the 12 speed hub that 12 speed cassettes fit 11 sp hubs but not the other way round

 

[chriswoody]

while I think they brought in a new standard ("Microspline") for 12sp drivetrains;

Micro spline is only for the Shimano 12 speed cassette's with a 10 tooth lower cog, not all 12 speed cassette's need this. It's Shimano's equivalent of SRAM's XD driver which serves the same function of facilitating a 10 tooth lower cog.

In order for the change to 12 speed, Shimano increased the length of the HG freehub body by 1,8mm when they moved to 12 speed. So from 35mm long to 36.8mm long. Lower speed cassette's will fit the newer 12 speed HG freehubs as long as you use a 1.8mm spacer, but 12 speed cassette's won't fit the older, shorter HG freehubs.

"HG35mm is commonly known as "Shimano 10 speed" or "Shimano 11 speed mountain" but it also fits Shimano-branded cassettes going back to the 7 speed days, and extending into 11 speed Shimano mountain bike and some (but not all) 11 speed Shimano road bike cassettes. Many Sram cassettes also use an HG35mm freehub body, including most 10 and 11 speed Sram road cassettes, and NX and SX model Sram mountain bike cassettes. Most (but not all) 11 speed Shimano road and gravel cassettes require an HG36.8mm freehub body. All Shimano 12 speed road (but not mountain bike) cassettes also need an HG36.8mm freehub body. If you're unsure which HG freehub you need, use our handy step-through guide."
https://www.wheelworks.co.nz/you-ne...DjZCuDr-puE6QsKpfFd0SilMuuUOrikajXgYi6SFGcyNH

 

[chriswoody]

Well, that isn't at all brain-meltingly confusing...

I've just been reading this page and it's no wonder it's confusing, because it's wrong, they've completely missed the fact that Shimano increased the length of the HG Freehub body.

On the charts they provide they say that SRAM NX cassette's will fit 9/10 speed HG freehub bodies. No they won't! I actually tried this the other day, I have an old 9 speed Shimano HG freehub body and as my link above attests, it's the older 35mm long one. The HG freehub body on my mountain bike is 36.8 mm long. So yes, my NX cassette slid on the old 9 speed body, but there was no way the last cog or the retaining ring was going on.

This whole thing of different standards is very confusing and there are many different sources of info out there, some conflicting with others.

 

[wafter]

Thanks @chriswoody - that makes a bit more sense and evidently that link isn't to be believed!

 

[13 rider]

I think we really cleared this up the the op 😁 , I was not confused now I am 😵‍💫
But I go back to my real life experience where my LBS fitted a 12 speed cassette to my existing 11 speed hub . So I believe that a modern Shimano 11 speed road hub will take a 12 speed road cassettes ( I've added to word road as not to confuse with 12 speed mountain)

 

[wonderloaf]

If it helps the OP the 12 speed 11-34t 105 cassette on my new bike also fits all the other 11 speed HG hubs on my other wheels, that being Mavic, Vel (actually a Nukeproof hub) and a Chinese make so I just assumed it was backwards compatible!

 

[chriswoody]

Thanks @chriswoody - that makes a bit more sense and evidently that link isn't to be believed!

Well to be fair, it is generally some good information on that page, but there are some problems with it. Even my link takes some careful reading, they mention that SRAM NX level cassete's will fit 35mm freehubs, but they fail to mention what speed cassette that is. I assume that means 11 speed, because 12 speed definitely won't, but it's easy to miss that small detail.

As you say, it is brain meltingly confusing.

Ooh and to add to the general level of head scratching on here, here's another link!

https://www.bike-components.de/blog...body-function-compatibilities-and-conversion/

 

[wafter]

Well to be fair, it is generally some good information on that page, but there are some problems with it. Even my link takes some careful reading, they mention that SRAM NX level cassete's will fit 35mm freehubs, but they fail to mention what speed cassette that is. I assume that means 11 speed, because 12 speed definitely won't, but it's easy to miss that small detail.

As you say, it is brain meltingly confusing.

Ooh and to add to the general level of head scratching on here, here's another link!

https://www.bike-components.de/blog...body-function-compatibilities-and-conversion/

Cheers - will take a look when I get a minute; thankfully just to satisfy curiousity as nothing important depends on my need to understand this

 

[Captain Scarlet]

Well many thanks for all the replies. I’ve read through, but will have to read again to make total sense of everything. Baffles me the infinite options on everything 🤯. I’m definitely a more ride them than than build them type….🤣

From the info I have it looks like the wheels in question will be good……failing that I’m sure they’d fit my sons bike, which he’d love I’m sure 🤣