Bottom Bracket Spindle Question on old Stumpjumper

[kirke]

I am currently building up an early 90s Specialized Stumpjumper as a single speed commuter/around town bike. It has a 73mm bottom bracket shell, 135 rear spacing.

I have this old Ritchey Logic crankset I was going to put on there. It was originally a double chainring setup, 110bcd.

I installed Shimano cartridge bottom bracket I had with a 110mm spindle. Just placing the cranks on the spindle I immediately noticed chainstay clearance was going to be an issue.

Pics of all this attached.

The 110mm spindle only gives me a few mm's of clearance.
Does anyone have a suggestion for how long of a spindle I might need to get better clearance? 113, 115, 118, 122, and 127 are the lengths these cheap Shimano bottom brackets come in.

Or is my issue that these might have been road cranks originally and getting clearance from these bigger mtb chainstays will just prove to be too big of a problem?

Any insight would be much appreciated! Can't wait to get this thing on the road.

-k.

[Slow Eddie]

According to BikePro, the Ritchey BB that was available at the same time the cranks were measured 120mm:

http://www.bikepro.com/products/cranks/ritchey.shtml

http://www.bikepro.com/products/bottom_brackets/ritcheyp.shtml


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[cachagua]

What's the other side look like? If there's enough clearance on the non-drive side, you can put a washer behind the drive side "cup" of the BB and move the whole assembly over. Couple mm is probably enough. Actually had to do that myself, just this afternoon.

Failing that, 115mm spindle would add 2-1/2mm on each side, provided the BB allows you to split the difference. Phils of course will allow that, also there's a Miche with both sides adjustable -- think I paid $28 for mine on eBay and it's surprisingly nice. Need a Campy-style tool, though, Shimano tool won't fit it.

[ultraman6970]

115 mm is still too short if the op wants to use the small chainring as well. IMO he needs to go with the two longest ones.

[oldpotatoe]

122mm is what is called for.

[kirke]

Awesome, thanks everyone.

If the original spec on this crank was a 120mm spindle then I'm sure the 122 should do the job.

According to Sheldon Brown, chainline for single speed mtb should be anywhere from 47.5-52mm. I'll measure my chainline with this 110spindle and see how much farther I need to go out.

I'll post pics in the 'Show us your old MTB' thread when this is done!

-k.

[ultraman6970]

IMO, Is not about the chainline it is about clearing the small chainring. I was you I would install the chainrings and then measure by eye the BB length that clears the chain stay.

[cachagua]

I am currently building up an early 90s Specialized Stumpjumper as a single speed...

Of course *if* in the future one wants to switch to 2 chainrings (or 3), buying the appropriate BB now saves buying another later on. But for the immediate purpose, as the original post describes, an inner chainring isn't a worry.

[ultraman6970]

Big difference :) did not catch that, my bad.

[kirke]

Yeah I am banking on using the outer chainring position to get a good chainline.

But I would like the ability to make this a 1x9 setup in the future!

[oldpotatoe]

Yeah I am banking on using the outer chainring position to get a good chainline.

But I would like the ability to make this a 1x9 setup in the future!

I think for most rear hubs, using the middle position will yield better chainline.

[gregj]

The Ritchey triples (110bcd) were spec'ed with 120mm bbs.

I think the Ritchey doubles (110bcd) were spec'ed with 113mm bbs. But they were for road bikes, so perhaps 113mm doesn't work quite as well on an MTB.

If you end up going with a 120 or 122mm bb, then the conventional wisdom says that you want to use the inner position, because that approximates the middle ring position, which aligns (in theory at least) with the middle of the rear cluster. If you use the inner position, you want to make sure that your ring is not too big to clear the chainstay.

But since you're going single speed, the chainline will depend on how you set up the rear. If you're just converting a freewheel or cassette hub, then you know where the SS cog will be in relation to a full cluster, and you can choose your front ring position based on that.

**The Ritchey compact cranks (94bcd) i think used different bb lengths, but you're using standard bcd so no need to worry there.