Should crank be centered?
 

Hello all,
I am trying to build a 1985 Fuji Sagres with a Sugino Maxy crank (which is not original, I'm replacing the original crank). I currently have a 118mm UN55 bottom bracket installed.

The drive side crank is 40.5mm from the seat tube, the non-drive side is 47.5mm from the seat tube, and the inner 40t chain ring clears the chain stay by less than a millimeter.

What's going on? How should the crank be positioned, why is it so off center, and what do I need to do to fix it?

I know the nds is so far out because the crank is meant for an asymmetrical shaft. Should I just get the chainline right and call it good?

Can you not find the correct bb for that crank or are you stuck with guessing? Have you Googled the crank?

If it doesn't bother your feet/knees/ankles/whatever? Sure, you're done.

There are expensive options (phil, etc...) that offer offset spindles. Some other brands of bottom bracket may allow the use of spacers on the right hand side, with a left retaining cup that lacks a shoulder. 3mm is quite a bit of spacer for a bottom bracket, but as long as you have adequate thread engagement, you should be fine. I've personally done this to space a bottom bracket for use with an odd freewheel, but is not something that I would undertake for a customer without express understanding that there are better (but much more expensive) solutions.

...I can't remember if it was the Sugino Maxy cranks, or the Mighty cranks (or both), but I dimly recall that the square taper sockets on those were not JIS taper ( I think)...I'd have to research it to be certain without looking at your parts.

Try searching for that information, and look at the actual fit of the cranks on your cartridge spindle. If the fit is OK (not bottoming out or in danger of doing so), I would personally just get next step up (longer...or whatever you need for chainline on the drive side) and call it good.

Q factor doesn't seem to bother me much, even though I hear people go on and on about it.

If you put 3 mm or so of spacers on the drive side flange of the bottom bracket, that'll even out the crank arms. And it should work so long as you have enough thread engagement and the NDS cup doesn't have a flange. Where would it put your chainline?

<EDIT> If your current bottom bracket's NDS cup does have a flange, you can replace it with a flangeless model like a Tange LN-3922 or pick up a flangeless cup like a UN54 cup or a Problem Solvers UP-CUP to work with your UN55.

As far as I'm aware, there is no "correct" cartridge bottom bracket manufactured for it. The Maxy used an asymmetric bottom bracket spindle in a size that isn't made in cartridge form. I've got a bike with a Sugino Maxy crankset, fitted to a 3S spindle. It's 121.5 mm long: 32 mm on the non-drive side, 52 between the races, and 37.5 on the drive side.

The Sugino Maxi Spindle is a 3-S.
32-52-37.5mm
The DS is noticeably longer.

A "symmetrical equivalent" BB would be 127MM

Bummer!

So should I get a symmetrical equivalent? That seems like it would be too long, since an unspaced 118 just clears.

Have you measured your chainline? That would tell us how much more length you need on the drive side. With that knowledge, we can estimate how to position things by choosing spindle length and spacers.

...or you could go old school and pick up a set of English threaded cups, 1/4" balls, and a 3S spindle. It may be the most common spindle length ever, so they're still available.

Just put a 2-3 mm spacer on the drive side. I do it all the time. Freewheel spacers work fine. It will give you the clearance at the chain stay and make the spacing symmetrical.

That will only work if there are 2-3mm extra threads on the adjustable cup.

I just discovered that I have a 3S spindle in my parts bin! I guess I just need a pair of cups.
Thanks!

A Crank Made to Use a equidistant Spindle BB will be symmetrical in pedal width from Center line of Bike .

OP says he is using a UN55 cartridge BB so lots of threads.

Well, I measured the 3s bottom bracket spindle. It's 124.5mm, not 121.5 like Sheldon Brown's database says it should be. What's up with that?

My UN55 BB has a lip on the NDS cup, preventing it from threading in far enough. I got one without a lip. After taking some measurements of chainline, I found that the crank will be centered and the chainline correct with 3mm of spacers.

UN55 all have that lip not just yours .. adding the 3mm of spacers you should have the Left sleeve,
perhaps for the 73 wide BB shell so the left side is well supported..

Re chain-line alignment? is it centered at the mid point of the rear gear cluster?

parts in 85 for cranks, were not symmetrical.

Yes, I measured 19.8mm to the center of the gear cluster from the inside of the dropout. 126/2= 63, 63-20= 43.
I measured 39mm from the center of the frame to between the chain rings, so 3mm of spacers would get it close.

.
...3mm (as someone else stated already) is a lot of spacers. But Phil BB's have 5 mm sideways adjustment, using cups on both sides that are held in place with Loctite threadlocker, so you ought to be able to get it to work that way.

It's worth reading up on their website, just for the information, even if yoiu don't want to drop a hunnert bucks on a BB.

https://www.philwood.com/philpdfs/cr...ationguide.pdf

+ the new ones use the press fit of the axle in the Bearings.
You can shift the axle sideways within the Bearing Cartridge.


BTW chain Line is lining up with the middle cog on the rear cluster

3 of 5, 5 of 9 etc, or the space between the 2 centre cogs with even numbers .

with the middle chainring of one or 3 or the space Between 2



.//.

That's a little weird. Sheldon and Yellow Jersey both have a 3S spindle listed as 121.5, but Sutherland's 6th edition shows 124.5 (35-52-37.5).

:thumb:

Unfortunately the non-ridged cup does not fit the UN55 cartridge. I'll have to find a different square taper spindle or grind away the ridge.

The 3mm is probably on the NDS, so it wouldn't matter to the chain line.

In the end I used a 3N spindle in a cup and cone bb with no spacers. This gave the correct chain line and the NDS crank is only 2mm further out than the DS. 3mm of spacers on the 118mm UN-55 would have been perfect but I don't have a cup with no ridges, and my friend had a nice 3N spindle in good condition.