Hi there I own a Devinci Cactus Series 1000 21 speed and I need to replace the derailler, it is a Shimano Deore rd-m510. What would someone suggest that I replace it with?

The Deore is a decent rear-derailleur ... You can replace it with another Deore if you want, used are pretty inexpensive if you're on a budget.

If you can afford it, replace it with XT or XTR ... Even used they're amazing.

What makes you think that you need a new derailleur?

Heh.

If I get the deore xt derailuer, will it still work with my front derailur?

Alivio M410. Nothing fancy, but inline with the specs I saw for a 2000 Cactus. Go up the ladder if you want to spend more new or can find used.

Take a look at the classified listings on the main page. Also check for a MTB Marketplace in the Mountain Biking subforum here. Someone might have a good used or NOS rd for sale.

If you not only know that you could just replace with another of the same model, and especially that a rear derailleur has nothing to do with the front then I suggest you be very careful about changing derailleurs.

By that I mean have someone else determine if you really need a new derailleur or if there is a different problem, and if it's needed also do the work for you, OR spend a few hours on the Sheldon Brown and Park sites reading everything about drive trains, interspersed with a few more hours hands-on with your bike.

That's what I was wondering too. The rear derailleur might be the most reliable part on the whole bike.

Aside from the front derailleur!

Yeah - what is the problem with the rear derailleur that makes it need replacing? IS is broken or twisted in half, or just can't seem to shift accurately?

Anyhoo, any Shimano indexed mtb derailleur that is not Dyna-Sys compatible will work. Alivio and Deore are great quality for the money and will work perfectly.

Make sure the derailleur hanger is straight before you try to adjust or install any rear derailleur - if the hanger is bent even a couple of degrees it will be almost impossible to get the derailleur set up right.

CHanging rear derailleur has no impact on the front derailleur.

I have a friend who is a bike technician look at it and showed me that the metal arm bent bent badly, so we straightened that out, then he noticed that piece that was connecting the the arm to the derailuer was bent. He still said it would work but suggested that I get a new one. mine bike is 8 years old with all original parts so I thought looking around might not be a bad idea, I've looked at buying locally but the stores bike guy doesn't seem interested in calling me back if he can help or not, even after I've called him a couple times so I went to look on the internet.

K thanks.