10 speed derailleur on 9 speed cassette

[Frana17]

Hi guys a friend of mine busted his rear derailleur(Alivio) on his his Silverback Spectra comp, he took the bike to a guy who then put a 10 speed deore derailleur on and it's not working right. He still has his original 9 Shimano Altus SL-M370 shifter and the 9 speed cassette on the bike. Is it even possible to run a 10 speed derailleur on a 9 speed cassette and shifter of should they be changed to 10 as well? Sorry for the noob questions, I'm quite new to this myself.

[Riaan373]

I'm sure if the lower and upper limits gets set proper it could work. That means that the derailleur can't move past 1 or 9 on the cassette. The shifter determines the amount that it moves. Many years back when I had 7 speed I had to replace and could only get a 8 speed derailleur and it worked perfect on the 7speed cassette.

[Beefy]

As far as I am aware it wont work. Cassette, shifter and derailleur need to match. For rear derailleurs the shifter has to be the same brand as well.

[DJR]

Won't work right because the derailleur geometry differs. Even if the (9 sp) shifter moves the cable the same distance, the 10 sp derailleur will move a slightly different distance compared to the 9 sp derailleur. If you try it, some parts of the cassette will shift OKish, others won't. If you dial it in on one place, then it will be wrong somewhere else. 

[Frana17]

Thanks for the reply guys. Apparently they have adjusted the upper and lower to no avail. The shifter needs to be shifted twice on two of the cogs to get them to shift. And then it doesn't reach the top two cogs.

[Frana17]

@DJR that's exactly what happens!

[Brawler]

Hmmm. I have the exact same setup on my girlfriends bike and it works 100%. Not sure how or why.

[Moriarty]

Spend some time playing around with the limits and cable tensioner, I am almost 100% sure you can achieve an acceptable operating solution.

[DJR]

Hmmm. I have the exact same setup on my girlfriends bike and it works 100%. Not sure how or why.

I know some guys make modifications that make it work, but I don't think it is ever simple and straight forward. I know "loose" cassettes can be made to work with different thickness spacers, but I don't know what they do to "fixed" cassettes.

[BenReaper]

Propper setting of the limits will fix youre problem.This is however still a modification and not the solution to the problem.

Either get a 9spd deraileur or upgrade the shifter,cassette and chain to 10spd aswell.

[Longbarn Killer]

It works on the road groupsets. To my knowledge, the mtb deraileurs use the same pull ratios as the road deraileurs. Theoretically it should work on a mtb.

[fanievb]

I run a 10 spd derailleur on my 9spd groupset (road) no problems. Indexing is determined by shifters and not the derailleur

[PedalGoat]

When I bought my Silverback, the original owner changed the front derailer to a 10 speed even though I had a 9 speed cassette. I struggled with the gears.after taking it to the lbs, I realised this. Luckily, he provided the original one.

[Frana17]

Thanks for all the reply's guys, he's taking the bike to the lbs today to see if they can't figure something out.

[Halfdoesyn]

9 speed and 10 speed derailleurs have different shift ratios. For the same amount of cable pull, each will move a different distance. See Sheldon Brown.

[DJR]

9 speed and 10 speed derailleurs have different shift ratios. For the same amount of cable pull, each will move a different distance. See Sheldon Brown.

That red bit there!