1992 Ritchey Ultra MTB: 68mm bottom bracket shell?

[mhespenheide]

I'm looking at changing out the cranks on my vintage/ancient 1992 Ritchey "Ultra" mountain bike. I double-checked the bottom bracket shell width and it looks like it's 68mm wide.

eh?

I though mountain bike bottom brackets were 73mm from pretty much the beginning, or was that a later change? (Or am I mismeasuring it somehow?)


Follow-up question: If the shell is indeed 68mm, I've got a set of XTR M950 cranks I'd like to use with it. I think those are Octalink V1-compatible? What length spindle should I look for?

Thank you!

[Pegoready]

Lots of MTBs have been 68 mm, that's not unusual. It's the reason virtually all MTB BB's come with spacers and are often labeled '68/73'. Use spacers with the 68 mm shell, no spacers with a 73 mm shell.

[Pegoready]

Also, you will want the 112.5 mm BB with 2.5 mm spacers on each side to achieve the 47.5 mm MTB chainline. Shimano offers an alternate 50 mm chainline spec for oversized seat tubes but I don't think you will need it. Yes, this era is 'V1' Octalink.

https://cdn10.bigcommerce.com/s-1rmgckn/products/2023/images/14976/img_6003_1280x853__28866.1411479998.700.950.jpg?c= 2

[oldpotatoe]

I'm looking at changing out the cranks on my vintage/ancient 1992 Ritchey "Ultra" mountain bike. I double-checked the bottom bracket shell width and it looks like it's 68mm wide.

eh?

I though mountain bike bottom brackets were 73mm from pretty much the beginning, or was that a later change? (Or am I mismeasuring it somehow?)


Follow-up question: If the shell is indeed 68mm, I've got a set of XTR M950 cranks I'd like to use with it. I think those are Octalink V1-compatible? What length spindle should I look for?

Thank you!

Many, many were 68mm..73mm started to happen with shimano's 'e-clamp' front der and also needing wider spacing for the crank because of wider chainstays, suspension, etc..

68mm, XTR were V1 octalink but not really compatible with road V1 octalink..length wise. I think they came in 114 and 116mm??

Ahh, lotsa pictures and such right above..:)

[Mark McM]

I'd bet the vast majority of MTBs in 1992 used 68mm BB shells. 73mm BB shells didn't become common until a few years later - and even then, it first became common on DH bikes, while XC bikes (like your Ritchey) stayed 68mm for longer.

[pdonk]

73 was also a Fisher standard for his aluminum bikes.

Need pics of bike.

[mhespenheide]

Thanks, guys!

[YoKev]

73 was also a Fisher standard for his aluminum bikes.

Need pics of bike.

I know this is in reference to Ritchey, but you mentioned Fisher so I thought I'd add to the convo of earlyish mtn bike standards.

Fisher had a "six part evolution" and one of those parts was a bottom bracket shell 88mm wide. It had press fit bearings held in by rings.

My 1991 AL-1 made from 7005 aluminum has this setup.

Those were interesting times!