Bottom Bracket Questions for a ProFlex 957 *THANKS*

[cincirider]

Last year I bought just a ProFlex 957 Frame with rear carbon swing arm and Noleen Shock. The frame also came with a head set and Shimano square taper bottom bracket. I'm not sure if the BB it came with is original equipment! I found some specs on BikePro.com that said the bike originally came with a Shimano XT cartridge 68 x 110. The BB that was in my frame measured about 110 but may have been 108/109. Here's my question.....I'm considering putting a pair of Shimano Hollowtech cranks on this bike, and of course they take the Octalink/Splined type BB. Will I need to get the same width BB as original (110) or not? Does a square taper crank engage a square taper BB spindle differently then a Octalink/Splined cranks on a Octalink/Splined BB. I don't know how to judge if the crank chain line will be greatly affected if I alter the distance from the frame by not having the right width BB! Any ideas or experience with the Hollowtech/Octalink set up on a ProFlex?

[kiwi]

68 x 110 a square was the original fitment..it was half way through 1996 remember!

[Sprucey]

Hi Cinci rider,

the Hollowtech 11 cranks DO NOT use splined bottom brackets at all. The crankset should come with a pair of bottom bracket cups and a number of spacers and you don't have to worry about the frame shell width or the axle length for a standard frame (some DH bikes use an 83mm frame width with 150mm wide rear dropouts so need a wider BB etc).

The axle is part of the crankset and not part of the BB. You simply follow the instructions about how many spacers to use on each side and the job's done! You will need a Hollowtech 11 specific tool to fit the cups - they're not expensive and useful to own if you are running Htech 11. Hollowtech 11 is a good syatem, very easy to use, light and stiff although there are varying qualities of BB shell bearings out there. Only worth wiorrying about if you have to replace the cups regularly.

As a general note, BB axle length is determined by the c./set you are running and not by the frame. Different c/sets use different sized spiders to position the rings and the recommended axle length ensures that the chainline is correct (keeping chain parrallel to centre of bike when in middle c/ring and cassette sprocket).

A lot of people on this site used shorter axles (ie 109mm against these days typically 113 or 118mml) to reduce the Q factor which is the distance bwteen the pedals, Q factor is a very roadie thing (to improive aerodymanics?) and not necessarilly relevent for MTB but if it's too narrow your heels may brush the chainstays/swing arm when you are pedalling. (Personally, I believe your feet should be at your natural stance width to avoid possible injury?)

So, just buy a Hollowtech 11 crankset and a tool - it will fit your 957 no problem.

I hope that helps?

Best regards,

Sprucey
www.ukbikestore.co.uk

[shovelon]

I think the original style Hollowtech cranks with spined BB used 113. Have to say I like mine pretty good, but had to use copious amounts of blue loctite to keep the bolts tight.

[Sprucey]

I stand semi corrected!

I should have said that there were two Holowtechs! The Hollwtech crankarms which are the arms with the void inside making them stiffer and lighter for which you will need a traditional BB in octolink splined and the newer Hollowtech 11 system (which uses the same construction for the arms but also the new BB cup system referred to above)

In my view, I wouldn't buy new with a traditional BB - The Htech 11 system offers too many advantages - weight, stiffness and ease of fitting/disassembly etc that it's ano brainer.

Have a good weekend everyone - it's a holiday weekend here in the UK.

Sprucey

[cincirider]

This may not help, but these are my cranks arms FC M751



Apparently, according to Sheldon Brown's website, this crankset took the Version 2 spline Octalink Bottom Bracket



I've since repainted them black!

Thanks again to those who review and reply!

CinciRider

[RhinoDave]

General guideline when switching from a square taper to a Octalink V2 crankset (M571, M751) is to go up one size. If you used a 110 sq. taper then go to a 113 Octalink. If you had a 113 sq taper then go to a 118 octalink. I am currently using a 68x113 octalink with a M751 XT crankset on my 856. I Switched my EVO 3 from a 73x113 square taper to a 73x118 LX M571 with no issues. I then switched the LX on my EVO to a M572 LX crankset and had to change the bottom bracket to a 73X126 because of the design change to the M572 model crankset even though they both use a V2 octalink bottom bracket.

[cincirider]

Thanks RD!
That's the answer I was needing!
CinciRider