A Question about 1x10 Gearing and Shimano SGS

[veggieburger]

Please help me understand. I always thought Shimano “SGS” meant long cage. I have a 1x10 MTB (30 teeth on the front, largest cog on the back is 42). My SLX RD is trashed. Thanks rocks.

So here I find a great price on this XT RD:
https://www.mec.ca/en/product/5034-2...r?colour=Black

It says the maximum sprocket is 36T. But being a long cage, it should be able to handle more than 36 teeth in the rear, no? Or am I missing something?

Thanks!

[KonaSS]

This rear derailleur was designed for a 2x10 system, so the specs reflect that. Will it fit a 42 if you are running 1x, that I can't answer.

[litcrazy]

SGS reflects the length of the cage (between the pulleys) and thus the total ammount of chain range it can absorb, front and rear.

The max cog size depends on the angles of parallelogram and other technologies that determine the angle the derailleur moves at as it travels from outside in. With 11 speed and later, derailleurs came to handle 42, 46, 51 max cog cassette.

I believe that with some playing around, some folks get that cassette to handle 40 tooth cassettes with some rear derailleur hangers.

You can also add a wolf tooth road link. I found this resulted in sloppiness in the small cogs.

Rumor has it the pull ratios on 10, 11 and 12 speed derailleurs are so close as to make them interchangable, despite what Shimano says.

I recently joined a 10 speed Shimano Deore shifter to an 11 speed XT rear derailleur with success. Those 11 speed rear derailleurs are pretty affordable, so that may be worth a try. Also, there's the new Deore rear derailleur with 51 tooth capacity.

[raisinberry777]

The easier answer here would be to buy a Deore M5120 rear derailleur - this is Shimano's current recommendation for 1x10 usage.

[veggieburger]

Originally Posted by raisinberry777

The easier answer here would be to buy a Deore M5120 rear derailleur - this is Shimano's current recommendation for 1x10 usage.

Well yes, but an XT for $49 CAD is a steal. Hence the question.

[tellyho]

I have tried a larger cassette with this derailleur - it's doesn't clear. I think it was 11-42. The 10 speed era was before Shimano got onboard the 1x train. Only retroactively made Deore derailleurs are made for big cassettes.

[veggieburger]

Originally Posted by tellyho

I have tried a larger cassette with this derailleur - it's doesn't clear. I think it was 11-42. The 10 speed era was before Shimano got onboard the 1x train. Only retroactively made Deore derailleurs are made for big cassettes.

Thanks for the info. The angle of the parallelogram makes sense to me...as I understand it, the RD has to travel down the angle of the cassette, so even though it's technically a long cage, it's not made for such a big pizza. All good.

Thanks again.