Well Ive only had my mountain bike for 3 weeks and I bent the lowest gear outward so I cant shift into 1st or 2nd. Make sure you never buy a sunrace cassette! (I'm sure you all knew that). Anyway I think I'm going to get a XT cassette to replace it, unless someone has a better suggestion. I want to try and install it myself, will I need to get any special tools? Any tips you might have for me would be appreciated since this is going to be my first bike repair.

Diligum,
You only need a cassette lockring remover and a chain whip, also called a sprocket remover. Assuming the Sunrace is Shimano compatible, you need a Park FR5 lockring remover. The chain whip can be generic - Nashbar or Performance works fine.

Remove the wheel.

Remove the quick release skewer by unscrewing the locknut.

Insert the cassette lockring remover so it engages the splines of the lockring.

Reinstall the QR skewer and screw the locknut on until it just holds the lockring remover in place. Doesn't need to be tight.

Wrap the chain whip around a middle sprocket so that pushing the handle clockwise tightens the chain.

Use a large wrench to just loosen the lockring counterclockwise. Just loosen then stop.

Unscrew the QR skewer locknut a couple of turns. See if the lockring remover can be unscrewed by hand. If not use the wrench to unscrew it just a little more. When it moves by hand only, remove the QR skewer.

Finish unscrewing the lockring.

Remove the cassette.

Install the new cassette.

Reinstall the lockring, using the lockring remover. I use the wrench to tighten it a few clicks until it is good and snug, but it is not necessary to get it extremely tight

Done.

Others please correct or add as necessary.

Regards,
Raymond

If your gonna use a torque wrench, it's 40nm. Just an FYI. Nice little touch with the QR rainman... The third hand eh?

Many thanks Raymond...I'm feeling much more confident about doing this myself now, and after it's done I'll know it was done right, and I can do it again if I need to. Time to go order tools!!

Why are you replacing the entire cassette? Granted, Sunrace cassettes are pretty awful, but since it is the smallest cog that you bent (did I read your post correctly? ), then why not just replace the cog? Unless these Sunrace cassettes are different, usually the smallest cog is apart from the main cassette. This might be a good opportunity to switch from an 11 tooth to a 12, if that's what you have.

I think he bent the low-gear (largest) cog, Alex. I do not know whether SunRace and Shimano are compatible at the inside end of the cassette.

Shimano is the standard that everyone follows. Except of course Campy. So sunrace is compatible.