Upgrading MTB BB, chainset and cassette

[syko89]

I'm looking to replace my bottom bracket and upgrade the chainset and cassette on my 2009 trek 6500 XC bike. As well as replacing the chain and. Any other bits that may need replacing at the same time.

I use the bike for general XC riding and trail centres with some smallish jumps, often muddy/wet.

There is some play in the BB so I need to replace this but I'm wondering whether to just replace all with original parts or upgrade?

What do I need to look out for? Is there different types/sizes of bottom brackets?

What would you consider a decent upgrade?

Cheers

[SkinnyBoy]

What do you have now?
What's your budget?

[syko89]

This is my original spec

Chainset: Shimano FCM521 Octalink
Chainrings:44/32/22 tooth chainrings
Cassette: SRAM PG950 11-34 tooth, 9 speed cassette

Budget wise say around £150 max for cassette, bb, chainset and chain. I may be able to stretch a little more if needs be.

The standard spec I have is ok but sometimes doesn't shift too well so something reliable would be ideal, what would you recommend?

Should I also be looking at replacing derailleurs at the same time? Or should these just be cleaned up if they seem ok?

[SkinnyBoy]

For me the first thing I would change is the shift cables. Pretty much most shifting woes are scabby cables. Some nice Jagwire ones will run you about 15 quid. Next get a cassette and new chain. The Sram PG950 and KMC X9 are a good combo. As for BB stick with the OEM Shimano replacement or if going with a Truvativ crank one of their GXP BB's. All that can be bought for your budget easily from online.

[syko89]

Cheers I will get some new cables!

Is a truvativ crank a one piece bottom bracket and crank arm? I've just tried taking it apart but the park tool puller sheared off I can see that it's hollow through the BB but still unsure which type it is... But it's not the usual bracket with square bits on the end I've seen before.

Do I need to measure the diameter of the internal BB or will any fit?

Thanks for the help

[SkinnyBoy]

Your old crank is octalink, a traditional three piece design where the cranks and BB are separate items. The newer cranks like Shimano hollowtech II and Truvative GXP are a 2 piece set up, where the crank, usually driveside is fixed to the bottom bracket spindle, and the bearings are external.

Octalink



GXP and H2



You will need to measure the width of your bottom bracket shell to get the right length BB. Usually its 68 or 73mm. Newer bikes like DH bikes are going with 83mm now.