Re-dishing wheel on 700c conversion
 

Hello all,

I am building a bike from a late 70s 531 tourer, and have just converted from 27x1 1/4 to 700c wheels. I have also stretched out from 120 rear OLN to 126mm. Inevitably my rear wheel is a little out of line to the brake holes and the stays by about 4mm closer to the left.

Now I know the next step for this is to re-dish, however I have heard this compromises wheel strength, does anyone have any experience with this? I'm a bit worried about having a weak wheel

Should I re-dish, or can i get away with it? the track with the front will be out of line though?

On another note - the front wheel also is close on the left - anyone else experienced this, or just a wonky-dished wheel?

thanks for looking

Are you just using a wider hub and jamming it into the frame, or did you actually cold-set the rear triangle to 126mm? If the frame has been cold-set, I would investigate if it is in alignment first.

If you turn the wheel around in the fork, does the rim shift position? If yes, then the rim is not centered over the hub. If it does not, then the fork might be bent, or the dropouts are out of alignment.

It doesn't matter if the frame was cold set or the wheel just "jammed in".
The result is the same.

Of course it compromises wheel strength, since it makes the wheel even more asymmetrical,
It's just a fact of life.

I've found many front wheels that are off a mm or 2.

True enough.

My main point is, I would look into the frame and dropout alignment before tensioning the rim further to the right (assuming the wheel is centered to begin with).

The question isn't how did he spread the frame, but did he widen the hub, and if so how.

If the OP didn't modify the wheel, it's already correctly dished (or should be) so changing the dish is not the correct approach.

Step one, confirm that the rim is correctly dished, namely centered between the axle locknut faces. There's no need to buy a special tool, he can use the FB/Campbell's dishing tool he already owns.

set three of the same* soup cans up on a table to form a tripod, supporting the rim at three points (no precision needed, just make a roughly equilateral triangle. Place wheel (tire off is better) on the cans, then stack up quarters from table to locknut. Flip wheel and compare the clearance to the coin stack (should be the same).

If the wheel is correctly dished, then the error is in the frame, and the OP can search "frame alignment" and take it from there.

*soup can be different as long as the can is the same.

+1 to FB's post.

The question is - is the wheel correctly dished? If not, why not? Was it modified some how, if so, how?

OP - what did you do to your rear wheel to make it "undished"?

Hi, thanks for the replies, it really is a huge help.

techsensai: You were right, what a good test, the front wheel just needs a little truing.

Regarding the real wheel: The spacing was 123mm, so It really wasn't a hassle springing it in. I did in fact afterwards do the timber lever resetting trick a little, but realised I needed to be accurate, so have put it on hold till a caliper rule arrives in the post.

The rear wheel is out of line, but only a few mm - apparently this is the result of doing 120 to 126 (according to sheldon brown's site). The cure is apparently to re-dish the wheel though this weakens it.

My main question was really - as long as the brakes are alright with a little tilt, and the wheel tracking is inline though off centre, will this ride ok or will I have problems, and is it dangerous?

Or another question - if i did end up re-dishing the wheel, is the weakness at this level dangerous?

I just want a safe bike, had 2 bad accidents enough for 1 lifetime.

You still haven't explained well enough. Did you change the WHEEL from 120 to 126, or the FRAME? Changing the frame alone and putting a random 126 wheel in will not require dishing of the wheel, unless it was wrong to begin with.

IMO, dish isn't the biggest thing in the world. I've run wheels that were dished wrong and never noticed anything bad. Honestly I'm not even sure what the effects are.

Thanks fastjake - wheel and frame changed.

originally 27x1 wheel 120mm OLN, frame was 123mm
Now 700c 126mm oln.

might try re-dishing then, wheels need a bit of truing anyway.

Kills two birds with one stone - check both.

=8-)

On the other hand, more or less strong isn't the issue. The issue is "strong enough". Lots and lots of bikes have been ridden lots and lots of miles with wheels that were dished that much. If everything else is right and the wheel is evenly tensioned, I wouldn't worry about it.

Only point I'll add is that no ruler or caliper is ever needed when spreading a rear triangle. All that's needed to insure a centered result is the intended wheel (which serves as the drop out width measurement device AND no more then that) and any thing that is straight and stiff enough to act as a gage when held in one's hand to compare the two sides of the string test (I use a pen often for this) .

As you bend the rear stays/drop out apart bit by bit you both test the width with the wheel and the centering with the classic string test. Neither needs any rule with MMs or inches. The wheel's axle is a go/no go gage. The straight stiff device held in hand, one end touching the ST and marked where the string pass by with your fingers/thumb is simple brought to the other side to compare.

Of course using some measuring devices makes you feel like you're being "accurate and precise". And when i do this in front of paying customers (which i don't like to as most people don't have the understanding of bending frames and the lack of concerns if done well) I use my Mitutoyo calipers. Because it makes me look all professional. But really a go/no go gage and an comparative indicator are just as good. Maybe better in that you then work to a single result and not get caught up in numbers that have no real meaning. Andy.

Thank you for the responses - going to get the wheel re-dished and trued and go from there.

thanks again