Chainline Question

[false_Aest]

So I have a chance at a SS CX bike. 73mm BB and 135 rear spacing. (The last time I had anything with a 73mm BB was 1999).

I'd like to use a Praxis Zayante crank and Paul SS hubs.

The problem that I see is this:
The Praxis crank has a 43.5mm chainline
The Paul hubs have a 52mm chainline.

Back in the day I could just buy a BB with a longer spindle to move the crank out a bit. I'm not sure what to do with outboard bearings.

If I want to use outboard bearings do I need to go over to a mountain crank? (Bummer because the chainring is tiny).

I know 1 solution would be to get a square taper crank and buy a Phil Wood BB but I'd like to avoid doing that.

Thoughts?
Suggestions?

[kingpin75s]

Originally Posted by false_Aest

So I have a chance at a SS CX bike. 73mm BB and 135 rear spacing. (The last time I had anything with a 73mm BB was 1999).

I'd like to use a Praxis Zayante crank and Paul SS hubs.

The problem that I see is this:
The Praxis crank has a 43.5mm chainline
The Paul hubs have a 52mm chainline.

Back in the day I could just buy a BB with a longer spindle to move the crank out a bit. I'm not sure what to do with outboard bearings.

If I want to use outboard bearings do I need to go over to a mountain crank? (Bummer because the chainring is tiny).

I know 1 solution would be to get a square taper crank and buy a Phil Wood BB but I'd like to avoid doing that.

Thoughts?
Suggestions?

Admittedly I use SqT on everything but I think you can make this work as this is a road double crank that you are converting to single correct?

- Chainline should be closer to ~46mm with a single ring mounted on the outside.
- Add chainring spacers to move out to 52mm.

Not sure if standard single ring bolts will accommodate that much of a push out to 52mm so may be able to get close with single ring bolts or could try bolts for a double with the spacers. I think you can get this close if not spot.

[11.4]

A 43.5 mm chainline on the front is your basic track or single-speed chainline (the track standard is actually 42.5 mm (and the centerline of a double-chainring front crankset is 46.5 by comparison) but that millimeter just gets lost in alignment error).

On the rear, the same shell is typically used for all axle dimensions, with a different axle substituted to get 120 mm, 135 mm, or whatever. The hub shell is centered so the relative position of the cog or freewheel to the crankset doesn't change. If you add more axle length outboard to the hub, it wouldn't normally affect the chainline itself. What Paul has done with just the one hub, however, has been to spread the flanges farther apart and push the cog out the extra 8 mm or so.

Trying to move the bottom bracket axle that far just won't do it, for a number of reasons. There may not be enough threads to handle that safely. The pedals will be significantly off-center so you'll have fitting issues. And so on.

Now depending on the length of the chain stays and subtle geometry issues, you can get away with 2-4 mm of chainline offset. However, the chain rapidly gets noisy, everything wears faster, and you can even have the chain come off the chainring, depending on how you manage your chain tension. So don't figure on sneaking much offset into the chainline itself.

This all means you have to fix any problem at the rear, unless you go to an atypical nonstandard crankset and even then you may not be able to make it work, or may not like the side effects of the result.

So frankly, I think you have to use a different hub/crankset combination. If this is a steel frame, you can respace the rear to 120 or 130 mm and have many more options available, but you can use many different approaches to making it work. I suspect that hub is intended for a much wider mountain or downhill crankset, not for a typical road-derived cross frame. Call Paul and get them to explain it to you, and see what they can come up with. That particular hub, I don't believe, will ever work for you.

[false_Aest]

Originally Posted by 11.4

That particular hub, I don't believe, will ever work for you.

That's what I wanted to hear. Back to the drawing board.

[false_Aest]

Annnnnnnd the solution is White Industries.

47.5 chainline for the hubs.
46.5 chainline for the 1x crankset.

Win.

[11.4]

Originally Posted by false_Aest

Annnnnnnd the solution is White Industries.

47.5 chainline for the hubs.
46.5 chainline for the 1x crankset.

Win.

That one's predictable. Just get away from funky non-standard designs. A lot of manufacturers have them and they're always a pain to work with. On track, fixed, or single speed, sticking to a standard usually works out better.

Are you getting their VBC ring configuration? If so, just note that I've had a couple problems with the inside ring not always fitting perfectly concentrically. You don't notice it on the road, but with a single-speed or fixed drivetrain, it becomes apparent with a looser or tighter chain at certain points in the crank rotation. The idea is simple but the precision and stiffness required to make it work properly are a challenge.

Note that you are getting equipment here that's designed around a road crank chainline. That's something that came about because hipster fixie riders always wanted to convert road cranks, so rear hubs that worked the 46.5 chainline became available. For SSCX it isn't a bad solution but it's also something that has limited compatibility outside of SSCX. Just by way of comparison, I've built up steel SSCX bikes where I respaced the rear to accommodate regular track hubs (or Phil Wood track hubs with ISO disc fittings on the left) and kept the 42.5 mm track standard. It works well, and especially if you're still using cantis or mini-V's, there's a huge aftermarket in used track hubs. And a huge aftermarket in used track cranks as well. You can get pairs of nice SSCX hubs for a hundred bucks a pair, or less, in superb condition -- mostly university students who wanted to be hip for about two weeks and then decided they preferred either a ten-speed or, more likely, a Vespa.

[seanile]

all city 130 rear has a 45mm chain line. and you can press phil wood bearings into it.