Bigfoot928

some of you internet engineers might be surprised if you talk to real motorsport engineers. I know a guy that has over 130 land speed records, and he does shave wheels, rotors and weld wheels.... so how does real world experience get trumped by the internets geeks..? food for thought

Dave928S

Modifying a road car and a track car are two totally different propositions, with different liability and insurance implications.

JWise

Porsche doesn't even approve of our use of 18" wheels. Imagine their response to the OP's question...

svpmx83

You also used the two magic words - motorsport and engineers. Anything is possible if done properly, but what is acceptable in motorsport generally cannot be translated to vehicles used on public roads.

And - some of us are real engineers with internet access
The fact that I feel compelled to weigh in on this wacky thread makes me hate myself a bit.

Dave928S

You removed about 2 mm from a hat which is about 6mm thick, and in so doing diminished the circumferential cross section by a significant percentage ... and didn't weaken them?

Can you provide us with some calculations to demonstrate what seems to me to be an engineering impossibility.

Am I correct in assuming you're an 'Internet Engineer'?

UpFixenDerPorsche

You have removed metal, therefore you have weakened the part !!!

Just as well the ultimate failure load is still above the load the wheel gets in everyday driving.

UpFixenDerPorsche

Shudder.

This is the sort of thing you'd expect to see done in Honest Ivan's car yard in the back streets of somewhere in Russia.

The metal around the bolt face is most highly stressed during cornering (particularly if a pothole is encountered). Visualise yourself trying pulling outwards at the base of the wheel while pushing in at the top. If you could exert enough force the bottom wheel nuts would pull through the alloy face.

You can't do that but cornering forces can.

The thickness of the face on my Design-90 wheels is 8mm.

Shave 2mm and you've lost A QUARTER of the maximum side load strength.

You're far better off getting a "cut and shunt" done at a reputable wheel works. This entails cutting and rejoining two wheels around the rim to make one wheel with the wanted offset.

If the rules there are anything like those here (in Oz) the weld will have to be x-rayed and ultrasonically checked for defects before it can be certified.

In answer to your question: DON'T DO IT.

UpFixenDerPorsche

www.ROHwheels.com.au

They export all over the world. Check places like TireRrack.

The 'Modena' would be among the lightest non-magnesium wheel around. And not bad looking.










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UpFixenDerPorsche

Well I suppose you could say I'm one of those 'internet engineers', but as it happens I have an engineering degree and I do talk to motorsport engineers.

I think you'll find LSR work involves very little cornering, hence only small side loads on the rim faces.

A far different side load scenario to that encountered under hard cornering on a bumpy country road.

9x8

Ironically, I have thought about doing the same to my set of Gemballa Le Mans, which have ET52 on fronts - but decided that it was too dangerous. So no, even in Russia we don't do that.

JET951

928SG , is that you Greg ?

FredR

Lightweight racing rims work well on the track - but the first time they hit a pothole in a street environment they fold.

I guess it's a bit like shaving **** hair- you can do it but would you really want to try?

Regards

Fred

rexpontius

Well, just to add my contribution to this discussion :-) I have actually had several sets of rims "shaved", even a brand new set of OZ superturismo GTs.

Some aftermarket wheels only come from the factory in standard ETs eg 30, 40, 50 etc.
If you need ET 35 you can either add a 5mm spacer to a ET40 wheel or shave 5mm of an ET30 wheel.

Now with the OZs the shaving can actually be done by the importer, and much more important the wheel is more or less 'built' for it. In contrast to for instance factory porsche wheels, the centers of OZ wheels are solid and the "meat" between the conical section of the bolts and hub face is much larger. Therefore it is possible to shave within sensible margins (not 15mm :-))

Also Azev wheels are highly customizable in this respect, you can even buy them without any bolt holes so you can have them drilled yourself.

Having said that I would NEVER shave an original porsche wheel simply because there is not enough material and I would be seriously worried about failure. Also shaving the brake rotors seems like a bad idea to me.

Cheers

Bigfoot928

so.. lets see.. you shave the hubs on a set of cast wheels in 1988.... set a 200+ mph land speed record on the salt flats, re use the wheels on your daily driver for 30 years and that isn't good enough for ya? good luck....let me know how your internet engineering works for you. I created a one of a kind 928 engine more than 15 years ago, and people called me a hoax... people that never met me or rode in my 928.... and you posers wonder why the real 928 owners never show up or post here...

Dave928S

Perhaps you are! ... The abusive rant PM you just sent would suggest that might be the case.

There's an old saying ... "If you throw dirt, all you lose is ground"

Have a nice day

BTW ... who are "the real 928 owners", you can't be one by your own definition, because you've "shown up here" ... us "posers" would like to know.