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Welding and machining aluminum wheels.

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  • Welding and machining aluminum wheels.

    OK as you may have guessed by my nickname I'm into Porsches except my income doesn't match my taste in cars Anyway I need to buy a set of track wheels for my car so that I can run DOT rubber at the track and not where it out on the street. The trouble is I'm tired of paying the "Porsche Tax" on everything Porsche related, kinda reminds me of when I built and raced Fords before the 5.0 craze dropped prices inline with Chevies. Anyway Porsche uses a 5x130mm bolt circle and an odd cup shaped taper for the lugs to seat into, I'd like to buy some cheaper wheels in a Chevy or Ford bolt pattern and weld up the holes then remachine. The question I have is will I significantly weaken the wheel? My brother has an industrial sized welder so I could get good penetration that I likely wouldn't get with my Lincoln SP 175 tig machine. The side benefit here is that I'm partial to American Racing Torq Thrust D's which are a modern version of the old Torq Thrusts from the 60's and 70's and where available in Porsche sizes back then. I'd like to run 17x8 and 17x9 to fit my big Brembo brakes and 13" rotors and just about every decent wheel with a Porsche bolt pattern is super expensive, the AM wheels are cheap by comparison. The machining part should be no problem, it's the welding that concerns me. Also I'd be stripping and powder coating the wheels to factory finish isn't an issue. I've got an Eastwood powder coat gun and an oven large enough for two wheels at a time.

  • #2
    Will the rules permit this?

    What if the welding caused some kind of embritlement to take place? Is there a possabilty the wheel might also be weakened because of the machining?

    Interesting question. Has anyone else with these cars ever done this?
    Gene

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    • #3
      Rules should be fine as there are guys running factory wheels modified from 16" to 17" by welding new rim pieces onto original centers.

      Machining should not weaken the wheel as the bolt circle is only 3mm different from a 5x5" (5x127mm).

      Embrittlement is my concern, I don't know what will happen which is why I'm asking. I only need to build the holes up enough to redrill 1.5mm off center and remachine the conical lugnut seat.

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      • #4
        i have welded up some bust out bolt holes and remachined them in al. wheels also fixed some of the old corvette knock offs. and never had any problems.

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        • #5
          Perhaps easier to find lug nuts with correct thread to fit the studs and wheels
          or just change the studs?
          Len

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          • #6
            I would go with a very experienced aluminum welder. Is this something you want to "think you got a pretty good job on" or know you did. Of course you may get the cost of the higher priced wheels wrapped up in the cheaper ones. The one I have used says he gets suprised all of the time. Had him simply weld a 3/4" dia. boss on a V6 Ford aluminum intake manifold for another water connection and he spent over an hour boiling up crud out of the puddle, grinding it off etc, etc.

            If it doesn't work, have the widow let us know.

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            • #7
              Is it possible to by the wheels undrilled?
              Jim H.

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              • #8
                911 Rims

                Chris, Jim's idea is pretty good, or why not to have the wheel done custom. I can see on the TV so many of those places that make custom rims for any car. That would be safe -perhaps a little more expensive. But I do not expect that it will be easy to get a very, very good Al welder for a little money, namely when he will realize what it is really for. Good luck. Vic

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                • #9
                  Originally posted by QSIMDO
                  Perhaps easier to find lug nuts with correct thread to fit the studs and wheels
                  or just change the studs?

                  It's the stud spacing that is the problem and I don't want to change that.

                  It's important to remember here that I'm only welding to build up the area to machine new holes off center from the original holes, off center by 1.5mm. My big concern is heat damage from welding and how it will effect strength. These are cast wheels


                  JC, I'm looking into buying unfinished wheels without the holes drilled but haven't had much luck yet.

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                  • #10
                    Originally posted by smagovic
                    Chris, Jim's idea is pretty good, or why not to have the wheel done custom. I can see on the TV so many of those places that make custom rims for any car. That would be safe -perhaps a little more expensive. But I do not expect that it will be easy to get a very, very good Al welder for a little money, namely when he will realize what it is really for. Good luck. Vic

                    Custom would be nice but would eliminate any possible savings which is my whole reason for this endeavor. I can buy all sorts of nice wheels both custom and stock but then theres that "Porsche Tax" and "Custom Tax"

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                    • #11
                      Are you certain what alloy the wheels are? Some are aluminum-magnesium alloy.
                      Free software for calculating bolt circles and similar: Click Here

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                      • #12
                        Once again, I have to say Evan's got a point. Exactly what metal do you have there?

                        I don't know what the design of the wheel looks like, but here's my idea. If you have enough solid metal far away from the original holes, can you drill that? For example, if the wheels were like the old "slotted dish" wheels, I'd center one up on my Bridgeport, program a 5-hole bolt circle into my DRO, and instruct it to start the first hole halfway between 2 existing holes. If your new holes were far enough from the old ones, you wouldn't even have to fill the old ones up, would you? No welding heat, no mystery metal identification, etc.

                        Something tells me this won't work for you, since you're probably a reasonably smart guy and probably would have already thought of it. Maybe some part of the idea could work? Anyway, this advice is worth every penny you paid for it.

                        -Mark
                        The curse of having precise measuring tools is being able to actually see how imperfect everything is.

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                        • #13
                          Originally posted by smagovic
                          Chris, Jim's idea is pretty good, or why not to have the wheel done custom. I can see on the TV so many of those places that make custom rims for any car. That would be safe -perhaps a little more expensive. But I do not expect that it will be easy to get a very, very good Al welder for a little money, namely when he will realize what it is really for. Good luck. Vic




                          I always thought that looked horrifically expensive, but that depends on the "blank" you start with. I think it was either American HotRod or American Chopper that had some wonderful Haas CNC mill that they made (make?) custom wheels with. They started with a gigantic solid piece of aluminum, IIRC. Forgetting for a second what you'd get charged to run such a machine continuously for 2 days (the TV show ran it all weekend), do you have an idea what a piece of 17-18" solid aluminum bar might cost in 8-10" lengths? (I don't, offhand, but I'd bet it's a lot.)

                          Never mind the flames about the two TV shows. I envy the resources made available to those guys, and I wish they were less "entertaining". Be nice if they would actually do things safely, correctly, and sensibly more often, but I'm not an advertiser on any of those shows, either.

                          -Mark
                          The curse of having precise measuring tools is being able to actually see how imperfect everything is.

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                          • #14
                            Are you looking for an odd size?

                            Used Fuchs wheels for Porsche aren't that much money, but if you insist on a size that's not stock or not commonly stock, you'll have an issue. I'd look for a set of Fuchs for the Turbo, they're as big as you'd commonly see. Your fenders may not be flared for big tires anyway.

                            I wouldn't take the approach you are describing. This is such a critical part of your vehicle, you are planning to use it in race conditions, and what could be worse than having the center of the wheel break out due to some imperfection in your process? I have to guess you'll catch the edge, completely flip the car, and total the car and possibly yourself if that happens--much worse than a flat tire.

                            If you insist on doing something yourself, get some modular wheels and machine a center blank for your bolt pattern from a solid chunk of the appropriate aluminum. Once machined, have it professionally heat treated to the spec that an expert familiar with your application recommends. If you are machining the center, you probably don't care too much what car the wheels were intended for--make sure the offsets will work out okay.

                            I used to have a slant nosed factory Turbo S that had a set of BBS modulars. Something like the BBS would be perfect, and they are long out of fashion. They were common on everything from Porsches to Pontiac Firebirds in the day, so you should be able to find some used. And, they were true modular wheels, so you could machine a center and bolt it back together.

                            Best,

                            BW
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                            • #15
                              Bob-- you bring up something I had always wondered about: The wisdom of using older aluminum wheels. For that matter one tends to wonder what they will all be like after a few decades of use now that they are so common on daily drivers. In a racing environment, I would guess the life of a wheel is short for other reasons.

                              The reason I bring this up is the fairly recent discussion here of stress-hardening (and stress cracking) of aluminum subject to lots of shock and vibration. Aircraft have a stringent inspection cycle because their fuselages can develop stress cracking. What about something that gets beat and cycled in and out of stress like a wheel? If you want to torture something, roll it over a modern road suface (especially here in the midwest)

                              Paul
                              Paul Carpenter
                              Mapleton, IL

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