or at least I broke the part of the nut that holds the rear wheel on.

Ok, so I was replacing the tube, and was tightening down on the track nut on the drive side, and I heard a pinging noise. I undid the track nut and the inner half of the nut had cracked in half. I don't know what to call this, but if you know how you have the 15 mm nut, then a funny little attached washer thingy with ridges to grip the dropout... well, the thing that broke threads onto the spindle and has the ridges to grip the dropout on the inside.

Anyway, this just cracked in half and was wondering if anyone can tell me what it is, so I can get a new one (and probably some spacers, since I need them). I ended up turning it 90* so that the crack was running vertically and tightened it just enough to hold it all in place. It's held up for another 20 miles, but I don't want to push it.

I know... pictures! I'll get them tonight...

i suspect that you're talking about the locknut.

rocks, you need to know the threading on your axle. if you are running formula or iro hubs (which i think you are but can't remember) go to bicycle pro shop in georgetown and get a new set on the cheap. ask for a set of 15mm 10x1 threaded track nuts. i know they have them there and won't overcharge you.

i think he meant he broke the track nut itself and is trying to explain the attached washer. but if it is a locknut, they have those at bicycle pro shop as well.

yeah, they're IRO (or formula whatever) ok, thanks for the tip ryan, I'll be up that way tomorrow anyway.

Yes, locknut seems like the right term.

if it's the piece on the inside of the dropout, then it's the locknut. those things break all of the time.

it's called an outer locknut (like shants said) and quality bicycle products seems to be out at the moment (they're who a lot of bike shops order from). the guys at revolution in georgetown (or bicycle pro shop, i never remember which is which) gave me one the other day, but just cause they had it laying around. worth a shot.

if it's an IRO rear you'll need something that's 10mm diameter and 1mm thread pitch.

gotta agree with shants...my friend broke a locknut on his formulas too!

actually the nut istelf is fine, it's the part that goes directly on the other side of the dropout that's cracked.

I've broken three so far. If you are not having problems with the wheel slipping you can replace them with non-hardened ones that will be alot less prone to cracking but won't bite in as well.

oh yeah, in a pinch i've used a regular ole track nut screwed on inside out. much wider than the locknut it replaces, but you say you need spacers so it might just work out.

yeah, outer locknut. go to georgetown and get one from bicycle pro shop. they will only charge you a dollar or two usually. as john and i have said, the threading is 10x1, they make them in different sizes and widths. i use a 15mm(for a 15mm cone wrench use) and then you can pick the width to make it fit your spacing best. good luck rocks.

he means the locknut on the inside of the dropout, not the one attached to the tracknut on the outside. i broke one too, and my bike shop just gave me one. you can use them for spacers too. it's no big deal.

Make sure those the locknut is tightened when you put them back on. Not too tight because that may produce more pressure on your bearings. From the times I've broken them it occured because the locknut was not absolutely next to the stuff it was locking, so there were only the threads "pushing back." When everything is tight everything else on the inside is giving some strength to the locknut too. What I'm trying to say is it's breaking over the threads.

I suspect this to be the case here too, I think the locknut was a little loose, not right up next to the bearing race and that may have precipitated the cracking...

thanks for all the advice, I think I may actually try an outside locknut on the inside to space it correclty.

glad to hear this is a common problem and other more compotent people (dutret esp.) have had to deal with it as well.