How do I get the BB spindle length right for my fixie?

[swee'pea99]

I was told the spindle length by the guy who sold me the frame: 110mm. When I fitted it, I found that when it was fitted tight, the drive side crank just rubbed up against the frame. Damn! Being a resourceful muppet, I figured 'if I move that crank out a couple of mm, it won't rub'. So I got a 2mm washer, just the right diameter, and it worked a dream. Clever me!

When the left crank started shifting slightly (only a fraction...it would 'give' just a bit when I reverse-braked) it never occurred to me (being an idiot) that the problem could actually be on the opposite end - the drive end - of the spindle. But I think that is where it is. The washer is preventing the drive side crank properly 'wedging' itself onto the spindle, so the 'shifting left crank' is actually not shifting at all. What's happening is that the left crank, firmly fixed, is moving the spindle inside the drive-side crank, which is not properly engaged because of the washer. Not clever me.

Bottom line, I think, is I was misinformed, and the 110mm spindle I was told to get is not actually long enough.

The question now being, how much longer to go?

The 2mm washer moved the drive side crank out enough so it didn't rub the frame. So does that mean that if I go up to, say, a 115mm, I should be ok (110mm + 2x2 + 1 to spare)? Or should I 'play it safe' and go up to, say, 118mm (which is only 4mm a side, when you think about it, which really doesn't seem a lot)? Or even a 122.5? Is there a downside to having a 'too long' spindle? (I can redish the wheel if necessary to ensure a straight chainline, so I'm not that bothered about that.

Any thoughts and advice appreciated. (Oh, and please don't just point me to Sheldon Brown's database...his table, as far as I can see, suggests that for a Sugino single crankset with a 70mm shell I need a 103mm - 7mm less than the 'too short' one I have already!)

 

[Howard]

Put a 2mm headset spacer behind your driveside BB cartridge.

Like this:

Tighten the crank arm down fully. Pray you didn't bust the taper interface with the washer experiment.

(assuming it's the crank spider that's fouling the chainstay)

 

[swee'pea99]

Ah! Schplendid! Something like this? http://www.ebay.co.uk/itm/Alloy-1-1...cycling_bikeparts_SR&var=&hash=item27b12ba70c

 

[Howard]

Yep that will do - it will move your NDS crank IN by 2mm, but you probably have the clearance for that and won't notice that it's slightly out of center beneath you. You could correct for that just be moving your cleats.

Or just buy a new longer BB as you suggested

Or buy the adjustable Phil Wood BB

 

[swee'pea99]

Fantastic! Many thanks.

 

[swee'pea99]

Got the spacer, but it won't fit on the BB - too small. It won't even go over the central barrel, let alone the (slightly wider) threaded section at the end. This shows it 'resting' on top of that central section:

Am I missing something? Did I get the wrong bit? As best I can see using a perspex ruler, the internal hole of the spacer is 28mm diameter; the central barrel of the BB is 32mm; the BB's threaded section (which I'm guessing any spacer would have to just slide over) is about 34mm.

If the spacer isn't the right bit I need, is there another 'bit' I should try?

 

[swee'pea99]

Bit of lateral thinking: is there anything writ in stone says I can't simply install the BB 'the wrong way round'? I've noticed the shaft coming out of the non-driver side extends a couple of mm longer than the shaft on the drive side - why can't I just turn it round? NB importantly that this is an Italian fit BB, so it has the same 'regular' thread on both ends. Can't see any reason why it shouldn't work just as well going the 'wrong' way, eh?

 

[RecordAceFromNew]

Got the spacer, but it won't fit on the BB - too small. It won't even go over the central barrel, let alone the (slightly wider) threaded section at the end. This shows it 'resting' on top of that central section:

Am I missing something? Did I get the wrong bit? As best I can see using a perspex ruler, the internal hole of the spacer is 28mm diameter; the central barrel of the BB is 32mm; the BB's threaded section (which I'm guessing any spacer would have to just slide over) is about 34mm.

If the spacer isn't the right bit I need, is there another 'bit' I should try?

Bit of lateral thinking: is there anything writ in stone says I can't simply install the BB 'the wrong way round'? I've noticed the shaft coming out of the non-driver side extends a couple of mm longer than the shaft on the drive side - why can't I just turn it round? NB importantly that this is an Italian fit BB, so it has the same 'regular' thread on both ends. Can't see any reason why it shouldn't work just as well going the 'wrong' way, eh?

There is no way a typical 1 1/8" (28.6mm) headset spacer can go between a typical cartridge bb and the bb shell, given the typical bb shell thread is 1.37" (British/ISO) and 36mm (Italian). Not even OS 1 1/4" headset spacers. While track/freewheel hub lockrings and traditional BB lockrings can be interchangeable, that is of no relevance here. Furthermore while bottom bracket spacers are available (e.g. from Velosolo or ebay), but since you are getting clash without, I am pretty sure a 2mm spacer is not going to be good enough (because it will not give you 2mm of clearance, and even 2mm of clearance is not enough in my view). Those spacers are for managing chainline, not avoiding clash. Additionally, I would have thought your chainline, given it appears we are talking about a fixie, would still be out if you simply add 2mm.

Regarding your 110mm bb problem, is it possible that your Sugino chainset requires a 110mm JIS bb while you bought an ISO one (given you indicated that the spindle is asymmetric - I am pretty sure JIS 110mm is practically symmetric)? An ISO bb will give rise to a JIS chainset close to c4.5mm further inboard than you need. Perhaps adding to the confusion, and in case you didn't know, is that Sugino while a Japanese company don't just make JIS specific square tapered chainsets like Shimano does, some of their chainsets require ISO tapers. What are the model codes of the chainset and bb?

I have no idea what swapping side might do for you. The temporary kludge that I know works is a layer or two of kitchen tin foil on the bb's square taper as shim before installing the chainset normally. I would not however recommend it for long term use, especially for a fixie.

Hope it helps.

 

[swee'pea99]

Thanks a lot for that. I did wonder about the JIS/ISO thing, but I was pretty sure it was a JIS, and when I tried a Campagnolo crank just on the off-chance, it was way worse than the Shimano/SRAM. So it is definitely JIS.

For the moment, I decided to take myself up on my lateral idea, and installed it wrong way round. And without wishing to hex anything, so far so good! I went out for half an hour, including some fairly serious uppy-downy bits, and no movement at all. The clearance for the left hand crank is close to nothing, but close to nothing is of course fine. So, like I say, for the moment, flipping the thing round seems to have sorted it. If it all goes tits up, I'll be back!

Thanks again.