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View Full Version : Welding and machining aluminum wheels.



rsr911
11-09-2006, 02:13 AM
OK as you may have guessed by my nickname I'm into Porsches except my income doesn't match my taste in cars :D 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.

topct
11-09-2006, 07:45 AM
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?

rsr911
11-09-2006, 08:12 AM
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.

bob308
11-09-2006, 08:50 AM
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.

QSIMDO
11-09-2006, 09:01 AM
Perhaps easier to find lug nuts with correct thread to fit the studs and wheels
or just change the studs?

GKman
11-09-2006, 09:02 AM
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.

JCHannum
11-09-2006, 10:32 AM
Is it possible to by the wheels undrilled?

smagovic
11-09-2006, 10:45 AM
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

rsr911
11-09-2006, 10:48 AM
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.

rsr911
11-09-2006, 10:50 AM
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" ;)

Evan
11-09-2006, 11:35 AM
Are you certain what alloy the wheels are? Some are aluminum-magnesium alloy.

Wirecutter
11-09-2006, 02:31 PM
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. :D

-Mark

Wirecutter
11-09-2006, 02:42 PM
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



:eek:

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

BobWarfield
11-09-2006, 02:43 PM
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

pcarpenter
11-09-2006, 03:09 PM
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) :rolleyes:

Paul

smagovic
11-09-2006, 03:33 PM
Mark, I absolutly agree with you that the custom rims would be expensive. In a way I am trying to talk him out of a short cut for something so important. But, it seems that other guys are comming out with some other alternatives like the one from BobW. I just feel that the wheels, namely on a powerful car as Porche is, is not a place to save. Also, as Evan said, what type of an alloy is it? This is another area where one can go wrong. Take care. Vic

QSIMDO
11-09-2006, 03:47 PM
It's the stud spacing that is the problem and I don't want to change that.

I thought about that after I posted but the boss was in so...any way, how about something like this?
http://www.skulte.com/index.php/cPath/21

Be a nice project, eh?
Especially at those prices!

HTRN
11-09-2006, 04:23 PM
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.)

Actually, it's a Vertical turning center, a VTC-48... Which isn't listed on the website, making me suspect it isn't made anymore..

HTRN

Magic9r
11-09-2006, 04:47 PM
For a change that small in PCD why not machine at the new PCD to accept a set of stepped inserts pressed in from the outside to accept the fastners of your choice?
Regards,
Nick

BobWarfield
11-09-2006, 05:07 PM
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) :rolleyes:

Paul

I would wonder depending on the brand, but Fuchs are what Porsche shipped out and they're good strong wheels that last, and BBS are also a great brand. I would inspect them carefully, of course.

In the end, lots of places to save on a car, just not clear doing so on the wheels is the right idea.

Best,

BW

rsr911
11-09-2006, 05:46 PM
Thanks for the replies.

Evan, I have no idea what alloy.

Wirecutter, I figured out the density of aluminum and calculated the cost of a blank at some ridiculous price figuring about $2.00/lb. I've seen forged blanks for motorcycles where you only need to machine the centers so that is a possibility. The wheels I like are all of the five spoke design for better brake cooling so there is no room for separate holes, good idea though.

Bob, Fuchs are good wheels but they aren't large enough diameter to clear my brakes. I'm running Brembo monoblocks from a 996 (newer 911) with 13" Wilwood front rotors. Fuchs only go up to 16" unless you get a custom set from Lindsey for big dollars. BBS rim halves is a great suggestion but I've priced the halves new at over $100 each so I'd have to find a set of used with the right offsets.

QSIMDO, As far as I know those adapters are not permitted by most sanctioning bodies. There is also no easy way to change the cars existing bolt pattern and even if I did it would mean I could no longer use my street wheels. One consideration I've had is to go ahead and change the car to 5x5" bolt circle and run steelies on the track, like Nascar does. They'd likely be too heavy but would be durable if I had an off track excursion as well as cheap to replace. If I did this I could run the wheels I like on the street.

I'm going to call some manufacturers about non-drilled and unfinished wheels. I'm sure somebody would be willing to sell them unless there is a liability or production issue. If I could source unfinished wheels I could do them on my CNC and offer the wheels to other enthusiasts allowing them to either leave them plain or they could clear coat or powder coat them.

I'm trying to keep costs low for many reasons including the fact that ideally I'd have street tires, full slicks, and DOT tires, the DOT tires could be used on the street for that occasional back road "tuning session" :D

I get what you guys are saying, welding is probably a bad idea. Road racing is VERY hard on wheels as the lateral and braking forces are much, much higher than driving on street tires. Lateral acceleration can be as high as 3 G's from what I've heard and it's not uncommon for wheels to crack.

If I where to get crazy and machine an entire wheel what alloy would you guys recommend? Remember the brakes on a race car put out a lot of heat as do the tires which gets soaked up by the wheels to some degree. The wheels are in fact heat exchangers in most cases unless you've got serious ductwork cooling those brakes. After all it's brakes not HP that wins road races.

madman
11-09-2006, 06:00 PM
Christian i pioneered the cheapo ass wheel bolt pattern change. I just set it up on my mill and bored out the wheel for inserts that i slid into place. Worked awesome was thrashed and never had a problem. I did NOT WELD IT. Dont weld it. Just bore out the new bolt pattern make lathe turned inserts to fill in the big hole assemble torque insert with jb weld epoxy let er sit a while and giddeup. I never had a problem. Hope it helps. Later Mike

RLD
11-09-2006, 06:09 PM
I would wonder depending on the brand, but Fuchs are what Porsche shipped out and they're good strong wheels that last, and BBS are also a great brand. I would inspect them carefully, of course.

In the end, lots of places to save on a car, just not clear doing so on the wheels is the right idea.

Best,

BW
Bob,
You probably know this, but the Fuchs wheels are forged. There are cast copies around (or were), and some of the clubs would not allow their use on the track. The molds were taken directly from the forged Fuchs wheels and the cast alloy wasn't nearly as strong; they broke.
Thanks,

Tinkerer
11-09-2006, 06:12 PM
I don't know what your wheels look like... but could you enlarge the holes and fabricate oversized coned flange nuts to center the wheels on the hubs? This would eliminate the welding if you could do it.

bluegrass
11-09-2006, 07:19 PM
RSR,
We used American Racing "Vector" wheels on the 911 I campaigned a long time ago. The proper bolt pattern was available at that time, but nobody dreamed of 17" wheels (except maybe 17 wide!).
Personally I am partial to the Fuchs, and they come in a zillion sizes, although some are a little hard to come by.
One other option is Mahle, the company that made the forged "gas cooker" wheels for the 914-6 and 911E. The Mahle gas cookers were the lightest wheel offered by Porsche at the time. I don't know what sizes were/are available, but it might be worth looking into. Maybe even call the Mahle people.
I know you nixed the idea of changing the bolt pattern, but if you MUST fit a different wheel, I believe I would consider changing the location of the studs on the disc, or even tapping new holes and using lug bolts instead, like some of us did WAY back. You could weld up the old holes, or even leave them open to avoid heating the rotor. Hey, that extra steel was just dead weight anyway...
Bluegrass

wierdscience
11-09-2006, 10:31 PM
I've done what Madman suggested,bored the pattern and made up T bushings to press in the holes out of Nitronic stainless steel.

QSIMDO
11-09-2006, 11:39 PM
Aah HA! These guys should know what's what;

http://www.weldcraftwheels.com/

rsr911
11-09-2006, 11:48 PM
I've done what Madman suggested,bored the pattern and made up T bushings to press in the holes out of Nitronic stainless steel.

You guys are geniuses! That is a great solution to the problem! Since I only need to relocate the holes by about 1.5mm the bushings can be relatively small. I'm concerned about stainless though, Porsche lugnuts are magnesium (I throw them at unsuspecting friends for fun) and might gall against stainless. I suppose proper anti-seize or better yet self made stainless nuts would work. I could leave them open ended and use long studs like the NHRA guys use for extra strength and easier wheel changes.

One thing I've seriously considered is converting to center locks and replacing the studs with drive pins, then I could just lightly slot the bolt holes. I'd just have to be sure to find the right center hole size for the center lock nut to seat against. This wouldn't be to hard as some of the 911 based race cars had center locks and I've got pictures of them. I'd have to get a LOT better at threading on the lathe though. ;)

rsr911
11-09-2006, 11:54 PM
Bob,
You probably know this, but the Fuchs wheels are forged. There are cast copies around (or were), and some of the clubs would not allow their use on the track. The molds were taken directly from the forged Fuchs wheels and the cast alloy wasn't nearly as strong; they broke.
Thanks,

Yup I had a cracked one myself. Lot's of folks get fooled by the cast copies. they were sold to VW enthusiasts as well. Poor choice for track wheels. Real forged Fuchs are very strong but they are getting old and I've seen pictures of cracked ones from hard track use. These cars often lift the inside front tire when cornering hard on DOT or slicks so a lot of side loading is in play.

abn
11-10-2006, 02:47 AM
I may have missed something as I just did a cursory read...but there are many double drilled wheels out there. Like my Centerlines...drilled 5 on 4.5 and 5 on 4.75". If it works for them I don't see why it wouldn't work for you. They're not cast wheels though. Another existing tech is oval inserts from Cragar wheels that allow them to be used on multiple bolt circles.

There are also plenty of aftermarket axles out there with double drilled flanges...a custom flange could also integrate a hub pilot diameter to match your new wheels. Depending on whether you care about hub-centricity versus lug-centricity.

I think a well manufactured and properly fastened hub-centric adapter/spacer would not sacrifice strength.

I wouldn't weld on my wheels if not absolutely necessary...

I'm cleaning out the closets and throwing away stuff...do you want a year's worth of old Excellence mags? Must be from the mid 90's when I was thinking of buying a 912 or 911 project for resto...before I decided that I couldn't afford Porsches and bought a Mustang. PM me with an address and they're yours.

Forrest Addy
11-10-2006, 04:42 AM
Even a small amount of welding at a highly stressed point like the bolt circle of a wheel comprises a risk to the metallurgy. I wouldn't monkey with welding is all that's involved is a small change in pitch circle. Elongate the holes to make the reach and make some 1/8 thick hard steel washers to span the gap. It's a far simpler and lower risk operation than welding and re-machining.

torker
11-10-2006, 09:37 AM
Christian...there was thread about welding on alu wheels on the Chaski board awhile back.
These where taken to an experienced welding shop with all the right tools.
Right off they ran into porosity problems....dug out the weld, tried it again(and again). If I rememebr right they finally got it but it didn't sound safe to me.
If someone brought a project like that to me I'm afraid I'd turn it down.
I spent quite a few years behind a blown alky engine and wrecked a few $900 wheels. I wouldn't even consider welding on one. I've seen it done but the failures where many.
Russ