New 12sp drivetrain not working properly

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Gianni76

Posted: May 17, 2022 at 17:59

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Hi all,

I purchased and had this drivetrain installed on my bike. After installation my bike mechanic said that this type of set up will not shift 100% accurately. He said it has something to do with the hyperglide system and the Sunrace cassette. I'll post the link below with all the components.

I've ridden about 20km on the bike and so far it shifts accurately about 75% of the time. The other 25% it makes that in between shift sound on the chain or will just randomly shift on its own.

I was wondering if anyone else has ran into this problem and if theres a solution to fix it.

Any help would be great as this is very disappointing.

Thanks

https://bikecomponents.ca/collections/drivetrain/products/shimano-deore-xt-m8100-groupset-w-o-crank-hg

melanthius

Posted: May 17, 2022 at 23:09

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I’d try changing the chain to a SRAM or KMC 12-speed. The Shimano chain has features designed specifically to catch the ramps on their HG+ cassettes. Shimano 12-speed chains also chew up chainrings that were designed for them because the inner link plates extend past where they do on any other chain. There’s no reason for that kit for come with that chain.

I use a 10-speed SunRace cassette with a KMC chain and it’s more like 95% vs the 99% of a SRAM or Shimano system and I’d expect their 12-speed stuff to be similar.

Cpembo6

Posted: May 18, 2022 at 19:51

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I've got the same setup except with a Sunrace MZ903 (it's the same as yours but mine has 3 alloy rings to save weight). My setup works perfectly. I tried it with a chainring that was not Shimano 12 speed compatible, and it was horrible. I also tried that same chainring with a SRAM chain and it was also horrible. Very noisy at the front chainring. But when moving back to the Shimano chainring and chain, it works flawlessly.

I suspect there might be something else wrong with your setup. Bent derailleur hanger perhaps?? Because this groupset should be fine. Yes, the Sunrace cassette is not Hyperglide+, but that just means it wont have the magical shifting under load feature that the new Shimano 12 speed offers. My cassette shifts perfect with no noise.

The only downside I have noticed with the Sunrace cassette, is that the chain will drop off the large rear cog if I back pedal 2 full pedal rotations. But in reality, I am never doing that on a ride. Lots of half ratchets backwards, but never 2 full turns in the lowest gear.

If you change the chain to a SRAM or KMC, you will also need to change the chainring becuase those chains wont mesh with the shimano chainring and they will be noisy.

melanthius

Posted: May 18, 2022 at 19:56	Quote
The upgrade kit he bought didn’t include a chainring, so I’m assuming he’s using his old one that’s not intended for a Shimano 12s chain. But your experience is valuable that the Shimano chain should work with that cassette and he should look elsewhere for the issue. OP: probably a good idea to take it to another shop if you’re not doing the work yourself.

Cpembo6

Posted: May 18, 2022 at 23:26

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Good call melanthius. I didnt pickup that the OP's link did not include the crank/chainring.

You can sometimes get lucky with other chainrings working with the SHimano 12 speed chain, but generally they dont work. Unless they specifically state "Shimano 12 speed compatble".

However, the chainring issue shoudl not affect teh shifting along the cassette. It will just cause the front chainring to be noisy.

But yeah, in my experience, that sunrace cassette works fine with the Shimano 12sp chain.

Branmuffin

Posted: May 19, 2022 at 7:29

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Cpembo6 wrote:

Incorrect chainring with a sh12 speed chain will usually cause chain suck, which will impact the shifting performance.

Gigniotromicon

Posted: May 23, 2022 at 6:38	Quote
I have the Shimano M8100 kit on my Vitus Sommer. I bought this bike used yesterday and it's missing a tooth on the lowest gear. Should I replace with the same CS-M8100 12 10/51t or is there a better option?

Branmuffin

Posted: May 23, 2022 at 7:57

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Gigniotromicon wrote:

I have the Shimano M8100 kit on my Vitus Sommer. I bought this bike used yesterday and it's missing a tooth on the lowest gear. Should I replace with the same CS-M8100 12 10/51t or is there a better option?

They also have a 10/45t version if you don’t need the lowest gear. There is not really a better version unless you go up to XT, which is just lighter, not really any performance upgrade.

Gigniotromicon

Posted: May 23, 2022 at 11:21

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Branmuffin wrote:

They also have a 10/45t version if you don’t need the lowest gear. There is not really a better version unless you go up to XT, which is just lighter, not really any performance upgrade.

Should've mentioned that it is all XT stuff from the factory. (Vitus Sommet CRX model)

Branmuffin

Posted: May 23, 2022 at 18:27

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Gigniotromicon wrote:

Branmuffin wrote:

They also have a 10/45t version if you don’t need the lowest gear. There is not really a better version unless you go up to XT, which is just lighter, not really any performance upgrade.

Should've mentioned that it is all XT stuff from the factory. (Vitus Sommet CRX model)

What I meant to say was XT is about as good as you will get performance wise. XTR is lighter, but I don’t think you will see a performance increase.

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