# 10 Speed Derailleur, 8 Speed cassette



## Hallinator (Jun 26, 2010)

Would it work if I got a nice new slx or deore xt rear derailleur (dyna-sys) and put it on my 8 speed bike.

I was thinking it would work because it's the 8 speed shifters that control the indexing, and the derailleur is oblivious to how many gears it is working with.

Yes, no? Eventually i'll switch it all over to ten speed, i'm just brainstorming here.

My inspiration ---->SLX Rear Derailleur 46% off


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## Crash Test Dumby (May 3, 2011)

Edited this post because as pointed out by the next poster I missed a VERY critical exception in Sheldon Browns article pertaining to Dynasis components.

http://www.sheldonbrown.com/speeds.html


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## mtnbiker72 (Jan 22, 2007)

Crash Test Dumby said:


> Yes it would work fine. Some will try to say otherwise, but they are usually epople trying to sell parts. I have posted this link many times, its the late great Sheldon Browns commentary on drive train parts, mixing 7, 8, 9 and 1p speed parts and such.
> 
> http://www.sheldonbrown.com/speeds.html


This is incorrect, the new 10 speed Dyna-Sys is *NOT* compatible with previous 7, 8, and 9 speed shifters as well as 10 speed road shifters. The Sheldon Brown article clearly states this.


> _Shimano Dyna-Sys 10-speed shifters and derailers use a longer cable pull than other Shimano models, and must be used together._


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## Crash Test Dumby (May 3, 2011)

mtnbiker72 said:


> This is incorrect, the new 10 speed Dyna-Sys is *NOT* compatible with previous 7, 8, and 9 speed shifters as well as 10 speed road shifters. The Sheldon Brown article clearly states this.


My bad, I did miss that detail. Sorry to the OP for missing that VERY critical detail in my response.


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## Hallinator (Jun 26, 2010)

Gahh looks like I'll have to wait a bit then... thanks for your help


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## pfox90 (Aug 8, 2010)

Why would you buy a 10sp der for an 8sp bike? Just doesn't even make sense even if it did work. Shifters have more to do with the performance aspect than the rear der. does.


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## jh_on_the_cape (Jan 12, 2004)

Just finding this with the search... I also want to use the new stuff with my old 8 speed stuff. I want to use the new shadow clutch XT der. Is that also Dyna-sys?


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## shiggy (Dec 19, 1998)

jh_on_the_cape said:


> Just finding this with the search... I also want to use the new stuff with my old 8 speed stuff. I want to use the new shadow clutch XT der. Is that also Dyna-sys?


All Shimano mtb 10-sp is Dyna-Sys and not compatible with anything else.


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## jh_on_the_cape (Jan 12, 2004)

shiggy said:


> All Shimano mtb 10-sp is Dyna-Sys and not compatible with anything else.


Thanks! Keeps me from a potential upgrade... anything else to improve chain tension? Chain is as short as I can do it, but sometimes in less than ideal chain/cog when I ratchet up something the chain goes a little slack then I slam forward taking up the slack.
I should go with a shorter cage der if possible? B-screw?


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## zebrahum (Jun 29, 2005)

jh_on_the_cape said:


> Thanks! Keeps me from a potential upgrade... anything else to improve chain tension? Chain is as short as I can do it, but sometimes in less than ideal chain/cog when I ratchet up something the chain goes a little slack then I slam forward taking up the slack.
> I should go with a shorter cage der if possible? B-screw?


Work on your gearing choices. You can't buy your way out being in the wrong gear.


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## filred (Apr 18, 2013)

For compatibility, I also don't know...


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## shiggy (Dec 19, 1998)

jh_on_the_cape said:


> Thanks! Keeps me from a potential upgrade... anything else to improve chain tension? Chain is as short as I can do it, but sometimes in less than ideal chain/cog when I ratchet up something the chain goes a little slack then I slam forward taking up the slack.
> I should go with a shorter cage der if possible? B-screw?


That does not sound like a chain tension problem. Just abusive technique.


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