Fixed gear chainline

[iRide]

Just wondering about BB spindle sizes, would a 102mm spindle BB work with a sugino crank and 120 spacing on the rear?

[bicycletricycle]

You left out some info, hub type, sugino cranks model

[Admiral Ackbar]

this has always been an exercise in trial and error from my experience.

but yes some more info would be nice

[markie]

Two correct answers. The third is google Sheldon Brown...

[11.4]

You simply can't determine it that easily. It's driven by your frame, your crankset, the chain line on the rear (some hubs support a 42.5 mm offset, others do 46.5, etc.). And a bottom bracket axle length doesn't mean anything. On a standard English bottom bracket I can install a 111 or 113 mm Phil Wood JIS taper, a 109.5 mm Shimano Octalink, a 107 mm GXP, and on and on -- all for correct chain line with one standard track crank or another. And if you are using a converted road crank, it's completely different again. The most significant is when you try to use a Dura Ace 7703 crankset on a fixie. That particular triple mounted the inside ring onto the middle ring, not to the crankset, and the middle ring didn't have a flange on the inside to rest the chainring against. The resulting crank looked exactly like a 7710 track crank, except that the space for the outer chainring (or where a track chainring should go) is spaced out something like 48.5 mm (because the crank is designed around a centerline for a triple ring combo).

It's mostly an experimental thing. If you get a Phil bottom bracket of the right general taper and size, you should be within a millimeter or two of being able to adjust it left and right to make it fit. If you're getting a cartridge or loose-axle bottom bracket, you are either putting spacers inside the bottom bracket cup on one side or having to buy another bottom bracket.

[ultraman6970]

You can live with the chain a little bit off of the ideal chain line just in case. 1 or 2 mm around the ideal is ok because chains arent stiff and they can give you some play.

As for the 102 and the sugino crankset, well I would say no. You will bottom that thing out big time, you need like a 110 for those cranksets. Put the cog in the back and if its grinding too much put a BB spacer between the hub and the cog, that should do the trick w/o having to play re-arranging cones and stuff.

[markie]

Put the cog in the back and if its grinding too much put a BB spacer between the hub and the cog, that should do the trick w/o having to play re-arranging cones and stuff.

I am not entirely sure what you are saying, but I am fairly certain it does not sound like a good idea.

[ultraman6970]

Unless you have something really off like 1 or 2 cm of difference in the chainline, in other words the chain is crossed badly, you can adjust the pushing the cog out adding a BB spacer behind the cog. Seen those in 1, 2 ,3 and 5 mm. That will move the cog out enough to get to the anal tolerances some guys likes to work with.

If the difference is just something stupidly big like 1 cm or more, the best is to fix the hub, respace it and redish the wheel, you can't fix that with spacers behind the cog.

The 1st thing the OP has to figure it out is to find the right BB axle. Once that is set pretty much the chain line is easy to fix because you have like 2 or 3 solutions depending of the wheels the dude is using and how far off he is from an acceptable chainline, my best guess is that he will use track hubs, in any case be off 1 or 2 mm between the cog and the chainring won't affect the ride, chains flex more than 2 mm anyways.

[benitosan1972]

You can live with the chain a little bit off of the ideal chain line just in case. 1 or 2 mm around the ideal is ok because chains arent stiff and they can give you some play.

As for the 102 and the sugino crankset, well I would say no. You will bottom that thing out big time, you need like a 110 for those cranksets. Put the cog in the back and if its grinding too much put a BB spacer between the hub and the cog, that should do the trick w/o having to play re-arranging cones and stuff.

False. If you use a track chain like the Izumi V or DID and chainline is off, the chain will prematurely wear out your cog.

False. The Sugino RD cranks can be mounted on a 103mm BB spindle. Unless you have narrow/fat chainstays, then you'll need a wider spindle to clear. Sugino 75 cranks use a 109.5mm BB spindle.

[benitosan1972]

That will move the cog out enough to get to the anal tolerances some guys likes to work with.

haha, W T F??? :eek:

[11.4]

I might just add that these days, cogs are pretty precisely the width of the hub threading, if not wider. Put a spacer in there and they really hang off the end of the threads. That's not the end of the world if you don't mind not being able to fit a lockring, but a spacer basically reduces the friction fit of the cog on the hub and allows it to spin loose more easily. If you can't fit a locking, that's a problem. In other posts here I've explained why lock rings aren't the preferred approach on the track, but on the road, with pedal strikes and people with no brakes, a lock ring is needed more. This approach doesn't help someone get there.

And one can tolerate a millimeter or two of chain misalignment with track chains -- it happens all the time -- but it'll be noisier and it'll wear the chainring and the cog a little faster. Still, if we held out for the last millimeter, we'd all be riding derailleur-equipped bikes. I'm neither anal nor sloppy ... I hope. But I do like to do it properly and I like a quiet chain. If someone gets a cheapie cog and expects low chain noise, chain line isn't going to solve the problem.

[oldpotatoe]

Just wondering about BB spindle sizes, would a 102mm spindle BB work with a sugino crank and 120 spacing on the rear?

Pretty sure most Sugino cranks, with 120mm spacing is 'spec-ed' for a 107mm BB..110 is the spacing is 130mm. JIS as well. Even a Sugino 75 is mated to a ISO 109....