Mountain Biking - What BB to get?

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA

View Full Version : What BB to get?

The LT
04-04-07, 08:58 PM
Hi, I'm kinda new to the MTB section of Bikeforums(typically over in SS/FG) I've posted a few times but figured I would say hi before I started asking a bunch of questions. What I want to know is what bottom bracket to get for my azonic steelhead that I am building up. I am running a truvativ crank(isoflow i think) with a bash guard on the outside(using the 32 middle ring) and a surly SS rear wheel with a shimano freewheel.

I had a 113mm BB installed but when I put the chain on it was rubbing the bashguard and making a bunch of noise. I figure I have to get a longer BB and I was wondering if a 115mm BB will push the drive side out 1mm, 2mm, or 0mm. The crank is square taper so I will be using a Shimano UN series BB and I know some of the lengths are asymmetric so I want to get some more opinions/answers before I spend the money to buy a new BB

Thanks in advance

FreeRidin'
04-04-07, 09:35 PM
If you switch from a 113mm to a 115mm spindle you will move the drive side crank out 1mm.

Why don't you run a spacer on the right side of the BB?
The LT
04-04-07, 09:45 PM
ok so the 115mm BBs are symmetrical. good to know.....I already have a spacer there and it isn't enough but a 115mm with a spacer should do the trick i think

metabike
04-05-07, 05:26 AM
I know that ISIS BB's are symmetric but I am not sure about square taper cartridges. Better check out Sheldon Brown's website & BB sizing chart before you buy.
scrublover
04-05-07, 06:05 AM
Assuming your chainline is decent the way it is now, no need to mess with a new BB, and still have issues.

Get a few chainring bolt spacers (yes, such do exist) and space the bash guard out a little more. Should quiet things down, and unless you get too crazy with it, shouldn't cause any issues at all.

Plus, it's cheap and easy.