Xt 8100 or 8120 with 10-45 cassette?

[DMan]

Curious, should I be using an 8120 derailleur with my 10-45 cassette for best shifting or will the 8100 long cage still shift just as well?

 

[The Duckmeister]

From memory I think 8120 is the 2x version; the geometry is slightly different to handle the change in tension from front shifting (yes, the front derailleur is still alive!). For 1x use the 8100, just back the B-screw out a bit to run with the 45.

 

[Scotty675]

Both will shift fine. The 8100 will allow you to go to a larger cassette latter on though. The 8120 is limited to 45t max and can be used 1x or 2x. I'm running a 9120 with a 10-45 and it shifts perfectly (1x), I fitted a 8100 and it also shifted fine (On stand only) as an experiment.

 

[DMan]

Both will shift fine. The 8100 will allow you to go to a larger cassette latter on though. The 8120 is limited to 45t max and can be used 1x or 2x. I'm running a 9120 with a 10-45 and it shifts perfectly (1x), I fitted a 8100 and it also shifted fine (On stand only) as an experiment.

I'm presently running a 7100 with my 10-45 and find it a bit notchy when shifting. So was wondering if a 7120 or 8120 was better suited as they list 10-45 as the max. But it sounds like there's no gains then.

 

[Scotty675]

Ive only ran the 8100 on the stand to see if it would work. It shifted perfectly but I've only run the 9120 under proper load in the bush. I don't think there would be any difference though. I'm happy to try the 8100 over the weekend and let you know

 

[DMan]

Ive only ran the 8100 on the stand to see if it would work. It shifted perfectly but I've only run the 9120 under proper load in the bush. I don't think there would be any difference though. I'm happy to try the 8100 over the weekend and let you know

Thanks for the info. I think you've answered my question. Curiosity makes me want to say yes but it's probably not worth it.

 

[Scotty675]

Also check your B screw, make sure it is set with Mark on cage. When I first changed to 12 speed I didn't set this correctly and it was notchy

 

[DMan]

Also check your B screw, make sure it is set with Mark on cage. When I first changed to 12 speed I didn't set this correctly and it was notchy

Now, I was wondering about that. Do you set it up the same even though my derailleur has 10-51 on it and I'm running a 10-45 cassette?

 

[Scotty675]

Set to same mark as its taken off the largest sprocket.

 

[DMan]

Set to same mark as its taken off the largest sprocket.

I'll check that tomorrow then. So with the chain off click the shifter over to the largest sprocket and set the distance with the b limit? Like in the top photo?

 

[Scotty675]

Largest tooth to white line, not the 2 arrows.
I'll run the 8100 to see if I can notice any difference riding. You have me curious now. I know it shifts fine on the stand.

 

[DMan]

Largest tooth to white line, not the 2 arrows.
I'll run the 8100 to see if I can notice any difference riding. You have me curious now. I know it shifts fine on the stand.

Cool. I'm curious to hear what you find.

 

[komdotkom]

I'll check that tomorrow then. So with the chain off click the shifter over to the largest sprocket and set the distance with the b limit? Like in the top photo?

What?! Perhaps I shouldn't just throw the instructions in the bin. I've setup 7100,8100 and 9120 and never known about this.
Real men don't read instructions.....

 

[bear the bear]

Curious, should I be using an 8120 derailleur with my 10-45 cassette for best shifting or will the 8100 long cage still shift just as well?

Didn't we answer this question a couple of months ago?
M8120 is for 10-45 (with or without a front derailleur as per @The Duckmeister)

Both will shift fine. The 8100 will allow you to go to a larger cassette latter on though. The 8120 is limited to 45t max and can be used 1x or 2x. I'm running a 9120 with a 10-45 and it shifts perfectly (1x), I fitted a 8100 and it also shifted fine (On stand only) as an experiment.

No, they won't having played around with it. Stick to Shimano's recommendations for the best shifting!

 

[DMan]

What?! Perhaps I shouldn't just throw the instructions in the bin. I've setup 7100,8100 and 9120 and never known about this.
Real men don't read instructions.....

What?! Perhaps I shouldn't just throw the instructions in the bin. I've setup 7100,8100 and 9120 and never known about this.
Real men don't read instructions.....

I read it but didn't really understand it with my having 10-51 stamped on my derailleur and a 10-45 cassette...

 

[DMan]

Didn't we answer this question a couple of months ago?
M8120 is for 10-45 (with or without a front derailleur as per @The Duckmeister)


No, they won't having played around with it. Stick to Shimano's recommendations for the best shifting!

I don't think so, or I couldn't find it if we did... I think I might have to rethink about getting a 7120 or 8120 derailleur then. So if you put a 10-51 on and had a 10-45, you have to change the derailleur too? That sucks a bit

 

[The Duckmeister]

Didn't we answer this question a couple of months ago?
M8120 is for 10-45 (with or without a front derailleur as per @The Duckmeister)

That's not whatI said. The xx20 variant (which actually has a longer cage) is for use in a 2x system, with a max. sprocket size of 45T. I haven't seen one in the flesh, but the derailleur geometry is a bit different from the standard version so the B-gap is less affected by the change in tension from front shifting.

For a 1x, use the standard type, for either sprocket size, and adjust the B-gap accordingly. I'll have to go back & check, but I think the reference mark for setting up on 45T is a bit different to the line for 51..

 

[DMan]

That's not whatI said. The xx20 variant (which actually has a longer cage) is for use in a 2x system, with a max. sprocket size of 45T. I haven't seen one in the flesh, but the derailleur geometry is a bit different from the standard version so the B-gap is less affected by the change in tension from front shifting.

For a 1x, use the standard type, for either sprocket size, and adjust the B-gap accordingly. I'll have to go back & check, but I think the reference mark for setting up on 45T is a bit different to the line for 51..

Now we are getting somewhere. If you could find the setup for a 10-45 it would be muchly appreciated @The Duckmeister

 

[Scotty675]

I just went downstairs and fitted the 8100 to the 10-45 cassette. Set up to the line, largest tooth to line. Shifts perfectly? I will report back after riding. Yes the 8100 has a longer cage to the 9120 but set up this way works perfectly with the smaller cassette.

 

[DMan]

I just went downstairs and fitted the 8100 to the 10-45 cassette. Set up to the line, largest tooth to line. Shifts perfectly? I will report back after riding. Yes the 8100 has a longer cage to the 9120 but set up this way works perfectly with the smaller cassette.

I'll check it out tomorrow. Cheers fella