Peter F

I have been thinking of widening my front rims.
It is Carrera 18" Porsche original 8" and ET50.
My thought is to add 18-20mm on the inside of the hub and should result in an ET of 68-70mm instead.(and 8,8" rim after)
Also would mean that I can put 255 wide rubbers on them right?
Has anyone tried doing this?
Is it safe and is my ET calculation right?
Would that size and ET work on my 90GT without rubbing issues?
(I also have the 928SP front swaybar on the car)
The company that i plan to use has done this type of modifications many times before and says it should be good.(has been in the alloy wheel welding and refurbishing for more than 15 Years)

Any inputs appreciated here.

/Peter

hacker-pschorr

I have a set of phone dials that are widened. I'm not running them anymore since 16x9 is an odd wheel to find a good tire for these days vs. my other wheels.

John Veninger

A 9.5" wheel w/ a 73mm offset and 275 tires can be used on your GT without rubbing since the fender is factory crimped.

I'm not a fan of the modification your talking about.

RyanPerrella

yeah i second john, i wouldnt do it. Wheels are pretty damn critical and if you somehow fracture one then your screwed.

Did you know forumla 1 cars have a duty cycle for wheels, its approximately 500Km for the race team then they get sent to the test team and run for a further 1300Km at which point they are most likely melted down, made into another billet and thus recycled.

Its possible to widen them but its expensive and 1 for one tink widened wheels arent worth anything because of the potential hazards of using them.

hacker-pschorr

The custom wide wheels on my track car lasted for over 10 years of 100% track duty with race tires - no issues, wheels are still 100% true.

Todd made them so the quality is second to none. Took 8 wheels to make 4.

Vilhuer

As Hacker writes, you need two sets of wheels to make one pair of wides. Have seen 10.5" Cup II's made out of 7" and 9". Its impossible to say from outside they are not stock in any other way than non matching cast ET number.

Peter F

I know it is not ideal but there is very few alternatives available to fit the 928.
(except extremely expensive three pcs wheels that can be made to look the way you want)
If the structure can be trusted I will go ahead and do it.
Can anyone confirm that my reasoning about the ET is correct?
Just want to verify I got the ET thinking right.

/Peter

andreas_thunell

Peter; Et is measured from the center of the wheel to the hub. If your wheel is 8" et 2" you will have 2" outside and 6" inside. If you extend the wheel 1" you will have a wheel with 2" outside and 7" inside. The center of the wheel is now 4,5" (instead of 4" before). The ET is now 2,5".

If you extend the wheel 1" inwards ET rice by 0,5". This is what I think. Not 100% sure.

jon928se

Peter

Yes your thinking on ET is correct.

Can you trust the structure?

In the '70s in the UK Steel wheels were widened regularly by cutting the wheel in two and adding a circular strip of steel - no need for 8 wheels to make 4. But welding steel is more reliable and easier than Aluminium.

I think if it was me I would probably not do it without the reassurance of some form of integrity testing. Given the cost of welding alu etc I suspect that it would be nearly as cheap to buy the correct wheels?

cfc928gt

Hum, wouldn't it make the ET 59-60 vs 68-70? The center point of the wheel changes by half the added width.

hacker-pschorr

Peter,
Have you seen the 997 18" 911 wheels? 11x18 bolt on the rear with no mods.

rixter

talk to lindsey, they widen fuchs for the 911 guys all the time
http://www.lindseyracing.com/

Vilhuer

This should be clear enough what will happen when 20mm is added to inside:

If above is correct, ET will change from 50 to 60mm. I'll try to dig up pictures which show how those Cup II's I mentioned earlier were made.

Peter F

Thanks guys,

this makes sense, and if that is the case i will add 30mm.
Doing that will bring me back to the original ET of 65mm on my front wheel with current ET of 50mm.
And the width will increase from 8" to 9,18" and this will easily host a 265 wide tire.
Hacker, this is for my front wheels.
Rear I already have 10" rims with 285 wide tires and I'm looking for some more front grip.

/Peter

daveo90s4

Why not just get a set of 18" x 10" wheels with 65mm ET direct from the back of a 993. Better still, get 4 and have the same wheels all round. Easier, probably safer (?) and probably not much more expensive than widening and 8" wheel. If my rudimentary understanding is correct, an 18" wheel with 65mm ET will, when fitted in place of a standard 16" wheel with 65mm ET, give an 'effective, dynamic' ET of around 68mm on the front, due to what used to be called king pin inclination, coupled with increased radius. On my 1990 S4 I've got 18" with 60mm ET (effectively about 63mm I believe). Don't recall whether they're 9" or 10" though.

As always, happy to be corrected if I've got any of the above wrong.
Dave, 90 S4, Dubai