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Truing an aluminum wheel

Ryan Slaback

Aluminum
Joined
Mar 13, 2007
Location
Menomonie WI
I have a 17" aftermarket aluminum wheel with a flat spot in it from hitting a pothole. The wheels are no longer made and I can not seem to find a singleton anywhere. Before I toss the entire set in the scrap heap I want to at least try to take the flat spot out to see if it can be balanced again. Does anyone have any experience/suggestions? I was thinking of warming it with the torch and making some type of rolling wheel that can be set on the inside of the wheel. I have a South Bend 16/24 or a rim clamp tire machine that I can chuck the wheel on if necessary.

Also, I can not seem to find anyone locally that does this work routinely and to ship it somewhere, pay for it to be retrued and shipped back I may as well by a different used set.
 
Here we go

I have been repairing Alum rims for 5 years now.

Do you want to learn to do this long distance or would you rather UPS the thing here? Shipping is around $35-$40. That's one way I might add. Minimum cost to do the work is $55. I can give you a better labor cost if you could put a decent pic of the effected area.

Memo
 
more to consider

1---They are showing 2 industrial rims. Not the rims people bring in for repair. Any Idiot who would weld some no pattern HD rim like that needs to go back and play in the sandbox......Learn the laws of gross tonnage again.

2---The rim that has been "filled" had %100 of surface weld removed. Alum does not "nugget" or "finger" or "blend" like steel. It relies heavily on the surface weld for much of it's strength. Big Rule If it doesn't have to seal there, don't grind there.

I could go on about all I have learned about rims the past 5 years, but it would take too long to type with this messed up keyboard and a sticky spacebar.

Memo
 
yep,look around

Me bud repairs bent wheels,all alum. i think.
He is a welder forman by trade,so maybe look at local welding/fab. houses.
I need a new key board too!!!
gw
 
I've been to one of the wheel repair stations here who does this work. The event I attended was one initiated by the Boston chapter of the BMW Car Club of America, and it was very enlightening.

The machine/method they use is rather simple. A vertical spindle rotating table (not powered) is setup in a heavy fabricated steel frame. Attached to the frame are two 1" travel dial indicators. One indicator checks radial runout, the other checks lateral runout. They have a variety of interchangeable spindle bolt pattern and "hubcentric" diameter arbors for the rotating table, they just bolt the right one to the bad wheel and put it on the rotating table.

Adjustments are made by heating up the affected sections with a torch from the inner bead side (never on the paint/finish side), then pressed and/or hammered back into "true" by attachments on the frame. The attachments are just little hydraulic piston jacks, and have interchangeable steel pads with big radii surfaces @ the contact point with the wheel. One pair of jacks slide on a heavy steel crossmember from above to correct lateral runout. A second one is mounted from the upright side rails to correct radial runout, and another (the most-often-used one) presses outward from inside the wheel to correct the common "flat spots".

They get the indicators to to read less than .015", usually better, and it's done. Simple, but effective. I was not allowed to take photos, but I think you can figure out how the process works from my description. You're an inventive bunch, I'm sure you could create your own system.
 
Mobile Alloy Wheel Repair

Since I live in Pittsburgh, aka the Pothole Capital of the World, I have some relevant experience with this topic. There is another company that franchises mobile wheel repair, www.mobilewheelrepair.com. Our local guy is excellent, and I noticed on that website that they have a few locations in Wisconsin. Of course, it's going to depend on the skill of the operator, so check them out first. They also do cosmetic repair - basically grinding and painting. Basically the shop is in a trailer and they come to you.

One caution if you attempt to roll your own. PixMan's description of the process is very good, but he suggests using heat when straightening, and in my experience while that is true for severe damage, most minor repairs, where you just have a vibration due to a not very severe out-of-round condition, can be more safely done without heat. Heat is needed for severe problems but you risk doing further damage and most repairs don't need it. To visualize the machine, imagine a tire changer with the center post extending about 18 inches both above and below the rim. You use a hydraulic porta-power pushing off the center post, and on the end you use a rounded die so as not to damage the wheel (nothing fancy needed).

I have also seen a local Tig magician fix short cracks in alloy wheels by stop-drilling, fine grinding, and then welding.
 
Here is a picture of the bent wheel. I remember it being much worse than this. That may be that after seeing the magic some guys have done this looks like a walk in the park. While I do not have the correct equipment that you guys have explained is there any reason that I could not fashion a curved base for a jack to fit on the good side of the wheel and then a curved die to push out the bend?
 

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Looks like an easy fix with a hammer and a cardboard template. Trace a pattern from a good wheel and tap it with a ball pein hammer. My thought is always no heat put it there so no heat needed to take it back. Of course a car is a 2,000 lb hammer...Bob
 
If you want to do it yourself and don't want to build the hydraulic contraption, you're going to need a BIG hammer. Make up a buck with a shape to suit the rim and visualize getting it back to round in 3 whacks. Will take more to get it all the way there but that will give you an idea of the force needed.

The big Sicilian who took me under his wing when I was turning wrenches could work magic with a hammer. Rule number 1 was don't pussyfoot- hit it and make it count. He had some big hammers in his box.
 
fixing them

I repair bent wheels all the time. I use big hammers. You cannot legally drive on a weld-repaired wheel- at least according to USDOT. It says nothing about repair made with other than welding. I use a file for jagged spot and a big hammer inside and out. I would be easier if you had a fixture or jig that would hold the wheel stationary and allowed you to rotate it to check run out.

Good luck
 
"any reason that I could not fashion a curved base for a jack to fit on the good side of the wheel and then a curved die to push out the bend?"

Don't do it unless you want an egg-shaped wheel. The opposite side is no stronger than the bent side. It will give as much as the side you are trying to straighten.

thnx, jack vines
 
Don't do it unless you want an egg-shaped wheel. The opposite side is no stronger than the bent side. It will give as much as the side you are trying to straighten.

thnx, jack vines


Correct me on the physics of this one if I am incorrect. But with the die fitting perfectly on the correct side wouldn't it spread the load over more area than the dented side (which would initially apply the entire load to just a small section) and therefore push the dented side first and only then when both sides fit perfectly and spread the load evenly would it egg shape.
 
Yes, but that means you have to make a fixture that matches the original radius perfectly.
 
The egg question

Correct me on the physics of this one if I am incorrect. But with the die fitting perfectly on the correct side wouldn't it spread the load over more area than the dented side (which would initially apply the entire load to just a small section) and therefore push the dented side first and only then when both sides fit perfectly and spread the load evenly would it egg shape.

Incorrect, methinks

Your proposition would work if there was a huge difference between:

1) the stress in a beam arising from a point load, and

2) the stress in a similar beam arising from the same load, distributed uniformly over the beam

(The fact that your beams are curved is not crucial to my point: humb-backed bridges are beams, even though they're curved)

In reality the difference in stress is small (both in theory and in practice) for a short beam, although it can be large for a very long beam

In specific relation to your question, your beams are short.
A "long beam" would be a wheel which is large in relation to the rim section, like say an alloy mountainbike wheel, where your proposal might work, at least initially.

Another problem, which affects small and large wheels: as the damage starts to gets pushed out, the damaged side will elastically deform so as to touch the punch in other places, and your "point load" will progressively approach more and more closely towards a uniformly distributed load.

Thirdly (at least in theory) there is the problem of springback. This means you have to push past the 'perfect circle' in order for the finished result to be truly circular.
However this can be mitigated by the 'punch' deforming elastically, which of course it will. But it does mean putting a LOT of load on the other side, which you don't want to stress past the yield point.

The effect of all this will be (at least in theory) that with your proposed course of action, all bets will be off, and you will get yourself an egg.
 
To heat or not to heat

To the person who said "no heat put it there so no heat needed to take it back" - I think it follows from your reasoning that all processes are necessarily reversible: so that straightening can be viewed as bending, turned thru 180 degrees.

If you're faced with a tub of melted ice cream, you've got the end result of a process which can't be reversed, either by heating or cooling.

True, some engineering processes can be reversed, but not necessarily just by turning the workpiece around and doing the same thing to the other side.

If you had a wheel made of something really ductile, like copper or gold, sure.

If metal strain-hardens, it's no longer in the same condition after being damaged as it was before. (Even copper will strain harden to a degree).

If it's possible to anneal it locally, that's one option, but temporarily reducing the local 'yield point' by applying heat is another.

There are two aims in each case: to make sure the damaged part is ductile rather than brittle, and to make sure the adjacent parts can stand up to the bending load fed into it from the damaged portion.

This implies the heating needs to be quite localised, and because aluminium is so thermally conductive, that means a strong concentrated heat source.

My guess would be that anyone who mades a living straightening things would go fairly hungry - and ruin a lot of items unnecessarily - if they only ever heated pieces, to straighten them, which had been hot when they got bent.
 








 
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