68mm to 73mmbb shell when?

[shovelon]

  I have searched the archvieves and found that all or most 98 and later proflex/Evo style frames use 73mm bb. With 96 and earlier using 68 bb shell.

 Did the forward pivot "x57" series move to 73mm? I am certain that they all are english thread. Right?

 This is all confusing. Japanese International Standard X English Thread X shell size X spindle length. Pardon my French, but sheeesh. And what is the deal about 68 to 73 shims?

 I am considering a Ti spindle to complete a special crankset build for my 957, and don't want to screw up.

Terry

 

 

[Sprucey]

Hi Terry,

I can't answer for when things changed but here are a few guidelines.

You could get a 73mm BB to fit a 68mm shell by using shims to space it out but you cannot do the reverse ie fit a 68mm BB to a 73mm shell.

I'm not sure where to purchase shims but most local bike shops with a workshop are likely to have a few spare shims kicking around.

The axle length is dependent on the crankset you are running / intending to run. Most crankset manufacturers will have details of the axle length in their technical literature on their websites.

As a guide only, 113mm fits most normal FS bikes with113 or 118mm fitting most hardtails.

You can often fit shorter or longer than that specified - trila and error is the only way to find out - the large chainring must have clearance on the chain stay.

Roadies like to fit as short an axle as possible to reduce what is known as the "Q" factor - the distance betwen the pedals. I am not a physio or a medic but I think this is wrong - I believe your feet shoud be a normal hip width apart to avoid RSI.

Of course the whole axle size / shell width issue is a thing of the past with the new Shimano Hollowtech 11 / FSA / Race Face X-type cransets where the bearings sit externally in individaul cups - a much better, lighter and stiffer system in my book.

I hope that helps?

Sprucey

[shovelon]

Sprucey,

You have helped. What I was not understanding was how to measure for 68 or 73. I think now it the length of the shell, not any diameters.

I can measure that without disassembly.

Thanks, Terry

[Simon]

To find if you need a 68mm or 73mm shell
just measure the B/B frame width (invert bike and measure across without dismantling).
Simon.

[kiwi]

i am petty sure the strut bikes were all 68 x110.Thats what the 756 is and i dont see they would change,the "evo" frame is 73 isnt it?

[shovelon]

Hi Kiwi,

 I am comming around. Now I get the basics. 68 or 73mm is the frame width at the bottom bracket shell. 110 or 113 is the spindle length. Shims are to adapt 68 width to 73mm frames(has nothing to do with bearing diameters).

 Octalink is rock solid but heavy, Isis is light but has a reputation to break. Jis has gone out of favor, but has a high degree of reliability and can be light.

 Can a titanium  JIS bottom bracket out perform ISIS titanium? I think bearing life is better with "Old school" JIS, as the spindle is narrower.

 I want to try a titanium BB on my 957 but need to weigh the benefits or drawbacks.

 Once I get a bead on my different frames I will post my findings.

Terry

[Simon]

Terry,
shims are to adapt 73mm shells to 68mm b/b
not the other way round,

Simon.

[Colin]

A useful link on BB terminology etc..
http://www.chainreactioncycles.com/Help.aspx?CategoryID=144

I've just bought a Shimano ES-71 73-113 Octalink to put on my 5500c to be able to fit my FSA Carbon cranks. - Hope it all fits together!

[Matno]

Hope it all fits together!

As long as your FSA cranks have grooves for 8 splines (the older Octalink compatible version that they don't make anymore) you should be fine. Sounds awesome. Make sure you grease your BB before installing it. I have an ES71 on my 5000, and it's creaked a couple of times - when it was new (I greased it), and now (I need to grease it again after 5 years).

[shovelon]

With great confidence I can say that my 957 has a 68mm BB. So I must conclude that all x57 series 1997 framesets are 68mm. All EVO frames are 73mm  BB. K2 3000 strut style frame has 73 mm BB.

Terry