AL7000

I have a 1989 Panasonic AL-7000 that I would like to run 28 mm tires on. The tires fit great on the back. However, the fork has excess material underneath the fork crown that rubs on the tire. The excess material is only on the right side leaving me to believe that it is a defect.

The fork is Tange CrMo.

Should I file off the extra lip on the fork? Replace it? Stick to 25mm tires?

(The attached photo is with 25mm tires. Notice how the right side curves much closer to the tire than the left)

cny-bikeman

I don't think there is a problem filing under the crown as long as you don't touch any portion of the actual fork blade.

ThermionicScott 

Might be worth taking the bike to a shop to make sure the fork (or the wheel) isn't misaligned.

But apart from that, I only have good things to say about filing underneath the crown for more clearance, Clarence.

Andrew R Stewart 

First call the side as the rider sits over the bike, the left side is closer to the left blade then the rt side sits the right blade.


fork alignment is not a binary issue. blade splay to one side, blade twist WTR the crown and blade length (which is what you spoke to) are the three common issues. But steerer straightness can be a contributing aspect too.


So the short answer is do you want the tire to look centered or do you want the fork to be really aligned? Simple solution is to file the long blade's drop out. Real one is to do a complete alignment, which might only turn out to be a drop out filing, but you don't know this yet. Andy.

Homebrew01

So, backup a step. What's off center ? Is the rim off center from the fork blades ?

FBinNY

While you can safely file upwards under the crown, you have to apply EXTREME judgement and caution before filing to the side. Fork blade tubing is very thin, and in most forks extends above the line where the tire is widest.

So, there's likely no amount of material that can safely be removed, and even a slight bit of removed material will leave a stress riser.

Keep in mind that, among all mechanical failures, a sudden fork failure is just about the most likely to lead to serious injury, and likely to lead to the most serious of possible injuries.

cny-bikeman

I don't think alignment or centering is the OP's concern. I thought so at first, but the appearance of the tire being off to the left side (right on pic) is probably a result of not being quite over the center of the tire. Instead the OP's focus is on the area underneath the fork crown, where the two roughly vertical scratches are. Note that the underside of the crown provides less clearance on the one side (left/bike right/pic).

p.s. I hate the apparent inability to post a pic from my computer. I would have preferred to circle the area and post the edited pic, but the new programming apparently only allows url's.

AnkleWork

Looks like a uni-crown fork (maybe).
First see if the wheel is true. Try reversing it left-right. Get it true if needed.
Then see what is the material you propose to file off. Brass or silver brazing -- proceed carefully.
Steel -- stop now.

AL7000

Yes that is what I was trying to focus on. I should have been more clear.

Andrew R Stewart 

If the uneven finishing of the underside of the fork "crown" (as there is no real crown here) is the question, don't sweat it. If the photo is actually straight on and shows a tire/wheel being off center then my earlier comments stand. Andy.

AL7000

It is a uni-crown fork. I realize now that part of the portion that would be filed off to stop it from rubbing is where the steerer tube is welded to the fork blade. It would take off part of the lower weld. So yeah I think I'll pass on this one.

CliffordK

The tire appears to be more or less right under the brake bolt, so alignment may not be an issue. More photos would help.

However, those imperfections in the crown appear to be at least 1/4" from the tire. Am I missing something? I can't see how the tire could be rubbing there. Is the wheel out of true? Hop? Picking up debris?

I might file a little bit on my own bike depending on where it is exactly, but you need to take the wheel off and take some high-res photos of the area, and perhaps the whole fork for people to really get a good idea of what you're filing.

CliffordK

Just go to the Advanced editing screen.
Click on the paper clip.

And upload photos. The system may resize them, but make sure they are about 100kb or less, not HUGE. JPG.

I like to hover over the links to get the image ID number, then add:

[attach] <image ID number> [/attach]

That allows specifying where the image goes into your message. But, it really isn't necessary.

cny-bikeman

Thanks, I looked but somehow missed the paper clip in Advanced.

dsbrantjr

The OP wishes to put wider tires than those shown in the photo 28mm vs 25mm shown.

Lazyass

Yes you can file it down, but the tubing is not thin in that area and will probably be a serious PIA. The fork on my Paramount was like your when I tried to fit 28's, except the whole steerer tube was jutting down a little, not just the side like yours. After about 2 minutes of trying to trim it with my dremel high speed cutter I said screw that. It was doing nothing but ruining the bit.

WizardOfBoz

The material there looks more forged than welded. If it's part of a forged gusset that holds the fork blades stable, you'd could be weakening the fork by filing.

lostarchitect 

Just a couple thoughts:

If you flip the wheel around, is it now closer to the other side?

Have you tried other wheels to see if it's the same?

I'm just wondering if it's a case of the wheel being build slightly off center.

CliffordK

If the fork is actually ground asymmetrical, then grinding it symmetrical is unlikely to significantly weaken it assuming good weld penetration for a welded joint.

Just pay attention to what you're grinding on.

But it all depends on the construction. If the parts began asymmetrical, and the the weld followed an incorrect line, then you could damage it a bit. Don't thin the fork blades.

There is often more material in a weld, cracks and stresses often form next to the weld, rather than in the weld.