Bicycle Mechanics - Is it bad if I dremel'd the head tube converting JIS to ISO?

I had a little dilemma buying a wrong headset. Being the newb I am, I didn't realize there were ISO and JIS versions of the Tange-Seiki headsets. Anyway, I grinded the head tube CAREFULLY counting the circles and finally finished it off with the sanding bit. I do know they make reamers, but I could of just bought a different headset. It's a cheap track frame (SE Premium Brew) so I'm not worried too much, however, I am worried if ~0.2mm off or so will cause premature wear. Also, for the fork, it was weird because the crown race was uber small - I ended up grinding the crown race since it was easier. Has anyone done this before, or is this highly not recommended?

Headsets require precise fits for a reason. All you can do now is ride it, because no one can determine what has changed. You'll find out if was okay or not, no one here can tell you.

Next time..... it would be better to ask --before-- you make permanent mods to the frame and fork !!

Go to an established shop, they should have a crown race cutter. Dremeling it is very imprecise and you'll probably end up with premature bearing wear.

if you are racing it on the track, you shouldn't be having to steer it a whole lot, so who cares? just get another headset if that one wears out. they are cheap.

I wouldn't be concerned about premature wear so much as not being able to adjust it properly. The head tube fittings and fork crown race seat need to be precisely concentric in order for the headset to adjust properly without binding or slop throughout the whole range of rotation. Without using properly piloted cutters to machine the race seats, this is a total crap-shoot.

The head tube fittings and fork crown race seat need to be precisely concentric in order for the headset to adjust properly without binding or slop throughout the whole range of rotation.

I'm glad you posted this. Now(!) I understand why a bike mechanic told me I, or rather he, had to reface my old Peugeot's head tube to fix my headset binding problem. He, of course, explained why, but it wasn't sinking in.

I had a little dilemma buying a wrong headset. Being the newb I am, I didn't realize there were ISO and JIS versions of the Tange-Seiki headsets. Anyway, I grinded the head tube CAREFULLY counting the circles and finally finished it off with the sanding bit. I do know they make reamers, but I could of just bought a different headset. It's a cheap track frame (SE Premium Brew) so I'm not worried too much, however, I am worried if ~0.2mm off or so will cause premature wear. Also, for the fork, it was weird because the crown race was uber small - I ended up grinding the crown race since it was easier. Has anyone done this before, or is this highly not recommended?

You really should've asked before doing this mod. It was totally ****ing unecessary - I doubt you're good enough with a grinder to have made it perfectly into the new size. Good thing you did it to a craptacular frame anyways so if the headtube is now too big for any headset to hold, you'd have lost nothing.

I knew I was going to get flamed on for this..lol :x

I know precision plays a big factor when trying to hone out the tubes, but it was very very minute. Coming from a backround of auto mechanics, there's no way I've would of done this to a block, but I guess it was just a quick fix so I could ride. I've pressed in cups before, and while pressing the Tange ones in, it went in normally. Anyway, the fork doesn't bind and there's no play what so ever. Luckily, this is on a doodoo frame - I definitely wouldn't have done it on a real frame.

Well, thanks for the input guys...you live and you learn.

..while pressing the Tange ones in, it went in normally. Anyway, the fork doesn't bind and there's no play what so ever. ...you live and you learn.

So you've learned that this works? If it works, why not do it on any other frame?

This goes along with the other thread and the BB...Ya gotta do it right with the right tools or you compromise good work.

if you are racing it on the track, you shouldn't be having to steer it a whole lot, so who cares? just get another headset if that one wears out. they are cheap.Actually, I've found from 6-years of track racing that due to the TIGHT quarters (rubbing both elbows isn't uncommon), that precision steering is of the utmost importance. Additionally, the extra 1-G of load in the corners (2G total) results in the magnification of any steering wobbles or headset stiction.