I'm building my first fixie and have discovered that my chainline is not the ideal I had planned on while choosing my components. I assumed from the info I culled from the web and the places I purchased my components that this combination would give me the perfect 42mm chainline.

Here's what I've got:

Brassknuckle frame
Sugino RD2 cranks w/ TA Alize 48T 1/8" chainring
Sugino 103mm bottom bracket
IRO "Dark Matter" wheelset with Surly 17T 1/8" cog

The chainline at the cranks measure 49mm. This is without the crank bolt, but I doubt that it will suck it in that much. I also know that I can run the chainring on the inside of the crank spider but would rather not(I'm a bit of a perfectionist and that seems like a cop out). A friend of mine has a Surly Steamroller Complete with the same BB,cranks(chainring on the outside), and cog as I've got and his chainline is straight as hell. It was my understanding that the chainline was independent of the frame...

Any advise would be greatly appreciated

Thanks

Tighten the crank bolts down. I bet it get pretty close.

Tightening the bolt will change the chainline significantly, but make sure you grease your spindle well before doing so.

Grease, tighten, remeasure.

-Chry

How's the crankarm/chainstay clearance?

chainstay/crankarm clearance is about 19mm.

With this setup your chainline will be 45mm, which is what Sugino specs for it now, even though you have to read a lot of fine print to actually find that out (link below). If your bottom bracket shell has not been faced, that will probably add a mm or so. Good on you for using a straight edge to actually check chainline, but keep in mind that most frames don't come from the factory lazer straight so even if you're right on on paper you might get a little bit of deviance when you actually measure front to back. The correct technical term for this deviance is "unspecified f***ness."

I'm not sure why they've done this, it's a real PITA. If you can return the cranks, I would do so, as this is a jingus setup that is never going to be quite right. If you can't, get a 2mm BB spacer and move to the inside, or if you're daring put the spacer under the cog.

This whole thing has left a big gap in the crank market, as the options are either cheaper stuff (bulletproof, RPM, etc...), more expensive overkill, random stuff that may or may not be any better than the cheapies (Pake, IRO), or tracking down the old RD-5000's that apparently work on the 103 BB (Soma has them for $100 with a 46t ring). You can also get the XD singlespeed, which is happy on easy to find 107 BB's, but is tough to find in anything but black -- allegedly you can get silver ones from J&B, but dealers don't seem to know about it. People complain about the XD being 110 and therefore having chainring flex, but that's a pretty flimsy complaint being that 110 compact doubles are now virtually the standard in road racing. Of course there's always the uber-uncool run it on a 107 with the chainring on the inside option, but even though I have no problem with doing it it just kind of rubs me the wrong way on what's sold as a track/SS crank.

https://www.suginoltd.co.jp/singlespeeder_e.html

The crank bolt sucks it in a ton. Why would you post about a 2mm difference if you haven't put it all the way together?

Thanks Landgolier...Thats what I suspected. They're slapping the single speed label on a double product to fill a niche market(incorrectly) without having to create any additional tooling and subsequent cost.

I think I'll try to make these cranks work in the meantime, hopefully thecrank bolts will suck them in enough for a decent chainline untill I eventually happen upon(get a winter deal) a single speed specific crank.

Thanks again for all your help

I really don't mind that they just relabel cranks for singlespeed, but the chainline thing bugs me. I also don't get it, because as a proper double these things would only need a 107 BB, there's no need for the taper to be so far outboard. They could easily have made them use their 103 for 42cm singlespeed and then speced a wider but still totally normal BB as a double. Everybody's happy (except those of us with italian bottom brackets), and it would have been all the same to them. I wish they had US reps we could harass about this stuff.

Just tighten it down. Mine was at about 45 mm when I first installed it, but after tightening it down some more it's just about perfect.

At least according to Jobst Brandt, who is pretty much Jebus when it comes to this stuff, retightening is very bad for the cranks.

"Failure from "over-tightening" is caused by repeated re-tightening of properly installed cranks. In use, an aluminum crank squirms on its taper and, because the retaining bolt prevents it from moving off the taper, it elbows itself away from the bolt and up the taper ever so slightly. The resulting loss of preload, after hard riding, can be detected by how easily the bolt can be turned."

https://www.sheldonbrown.com/brandt/i...ng-cranks.html

Are these the same cranks that Harris cyclery sells, advertised as giving a 42mm chainline with the Sugino 103mm BB? I have a set with the bb that I haven't installed yet and am hoping that they'll give the right (42mm) chainline.

What are yours stamped on the back of the drive side arm? And what graphics are on them?

Marking on the back of the drive side crank is RD2R, with "TL" below it. Graphics are just the "Sugino" script.

Yeah, those are the same cranks I have...RD2R - TL with Sugino in black along the arm.

Hmmm, well, great, I guess I'll just have to try assembling it tomorrow and see how it turns out.

Move washers/spacers from the drive side of the hub axle to the left side and then re-dish the rear wheel.

If he does that he can't use the wheel as flip/flop

The ones stamped RD2R are going to come out to 45 almost guaranteed. The ones that come out to 42 are the RD-5000 (forget the exact stamping but it has a 5 in it somewhere) and then the old hidden bolt RD.

I think the Sugino BB may give like a 1mm further inboard chain line than a shimano, but it's definitely JIS and going to come out nearly the same. Also, don't try to put an ISO BB in these (people often try the miche track adjustable, but campy are also ISO), it will bottom out.

Fun fun.

does anyone know if AEbike is still carrying the RD's? also what Italian threaded BB can i use with these, or should i settle on a different budget crank? and if so which would be good? thanks ....bump

I don't recognize the RD2 nomenclature, but Sugino made the RD for double rings, with an inner and outer position.

My Pista, when I had an RD crank on it, had a perfect chainline with the chainring on the inner position.

Does the RD2 have two ring positions?

Did I miss something?

have not measured mine but I built an Iro with the same exact set up with a KOOL chain and it is SILENT!

yes please tighten the crankbolts. there is no way u can judge the chainline without doing that.

aebike is just the QBP catalog listed online, looks like they only have RD2's left.

You can use a 107 shimano (or IRD, but they're sold out of Italian thread for the next 1.5 decades or something) with the chainring in the middle position and 0-2mm of spacers depending on your cog and hub. Also keep in mind that you can't really buy italian diameter spacers so you just have to cut a slot in regular ones, though this works perfectly well. You could also get a sugino XD crank or the new ben's/soma budget 144 BCD crank. There are other random ones out there, the IRO crank is good.

Landgolier thanks for the info.
can you find the link to the rd2's. this is where i bought mine and i can only find the black messenger crank arms.