Pelican Parts Forums - Early offset 944 max width 17" wheels on the front with stock fenders

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Early offset 944 max width 17" wheels on the front with stock fenders

I'm looking at getting some 17s for my 944 so I've got some better tire choices. I thought I'd seen people were running 17x9 with 245 or 255 rubber up front, but now I can't find any threads or info. The wheels I'm looking at are 15mm offset on 9" widths and 10.6mm on 8".

Who's got input?

Neither of those will work for 255/40r17 tires because they put all the extra width on the outside for those wanting the hellaflush stance with cheap 205 or 225mm tyres. The stock 951 already rubs its 16x7" wheels with 205mm tyres on fenders.

You want to put the extra width on the inside where there's A LOT more room. So to fit a 255/40r17 tyre on 17x9" rim, offset needs to be 35-40mm for early-offset cars. Or 60-65mm for late-offset cars, like what Porsche did with TurboS. Optimum grip for that tyre size is a 17x10" rim.

a stock 951 rubs its 16x7s with 205s on the fenders? really?

yeah nope. stock they do not rub.

even when you run square with 8s in front, and 225s they don't rub. in fact, we even ran the 8s with 225s on haroldinas car without rubbing.

Also, a 15mm offset on a 9" wheel gives me about 3/4" more wheel inboard and about 1 1/4" more outboard compared to a 7" wheel with 23.3mm offset. That can hardly be considered putting all of it towards the fender.

with turbo S offset car, MY02 rear 18x10s fit all around. youll have to find the numbers and do the math. I have 285s on them. also, turbo S fenders are rolled, and I have ground controls in front which leave more room

I' have been running 245/45-17 on 9" rim in front and 275/40-17 on 10" rim in rear, for many years with good luck.

The sizes do slow the car slightly in straight ahead acceleration in the 1/4 mile, but add .75 G. before break out on the curves.

Have done this with NA's and Turbo's for long time.

Would never recommend any larger rims than 17" for total geometry of suspension.

Quote:

Originally Posted by cockerpunk (Post 8854295)

haven't push hard enough I guess. Try hitting bumps with the steering turned all the way. Bumps combined with more than 90-degrees of steering will rub the tyre on the fender at speed. Sure grandma can take any car to get groceries and not rub the fenders.

On early-offset 951, I was able to run 17x10.5" wheels with 255/40-17 tyres by increasing offset to 35mm. Rear 17x11.5" with 275/40-17 tyres, same 35mm offset.

Remember, the OP is asking about 245 or 255mm tires, not 205 or 225.

So I have an 1986 944 turbo and can get a very nice set of 3 piece BBS 17 in wheels.

2x8x17 et24
2x10x17 et11

Tires 225/45R17 and 255/40R17

I’m wondering if with these offsets the wheels will rub or I’ll need spacers. The lip on these wheels seams to look deep which I like but I don’t want rubbing and will be lowering the car slightly with coil overs.

Any advice?

Quote:

Originally Posted by MoeMonney (Post 12383405)

You should really just calculate this yourself. Consider your current wheels as your baseline.

You will need to calculate how much additional front and back spacing the new wheel/tire combo will change based on your current wheels/baseline. Then determine if you will have enough space to fit the new wheels/tires by measuring how much additional space to fender/rear strut you have from current wheel setup.

Offset and wheel width are the two critical numbers here. Offset is the distance the wheel sits/mounts from the centerline of the wheel and is relative to the width of the wheel. If wheels widths are the same, its very easy to just add/subtract the offset to get the difference, but if wheel widths are different, its a bit more complicated and width needs to also be factored into the calculation.

So as an example to calculate front wheel fitment. If you have a 7" wheel at a 23et offset (stock 86 turbo wheel), and then moving to an 8" wheel with a 24et offset. The 8" wheel is 25.4mm (1") wider than the 7" wheel. Half of that is 13mm, and then add the offset difference (-1mm) which means the 8" et24 wheel is going to sit ~12mm further out. On the backside, it will be ~14mm further out than the 7" wheel.

So the equation for front spacing change is:
(Baseline wheel offset mm - New wheel offset mm) + ((New wheel width mm - Baseline wheel width mm)/2)

Back spacing change is:
(New wheel offset mm-Baseline wheel offset mm) + ((New wheel width mm - Baseline wheel width mm)/2)

Now go measure the distance from tire to fender on your current 7" et23 wheel... is there 17mm of clearance? (give yourself at least 5mm of buffer, so 17mm or so). Repeat this for the backside of the wheels distance to spring perch/strut, is there 19mm of clearance? (14mm + 5mm buffer = 19mm). Now repeat these calculations and measurements again for the rear wheels

That is how you calculate wheel fitment, so you can eliminate any guesswork or reliance on others. Keep in mind you can squeeze/fine tune more fitment by running more negative camber as well or raising the car so the fender doesnt contact the tire over bumps/turns...

If I had to guess, I would say the wheels will probably fit, but again, you should do these calculations and measurements yourself as it is also highly dependent on your alignment (camber), tire size/width and ride height settings. Tire sidewall especially can factor into rubbing if you go to an overall wider/skinnier tire/wheel width ratio than current. Be sure to calculate the new wheel to tire width ratio, if the tires are going to be a higher ratio than current, give yourself more buffer. Based on your tire sizes listed this "sidewall factor" likely wont be drastically different from stock.

Here is another good guide
https://www.drivingline.com/articles/idiots-guide-to-wheel-fitment/#:~:text=Put%20simply%2C%20to%20find%20if,to%20see %20if%20it%20fits.

offsets and width greatly simplified

https://www.willtheyfit.com/

your front should just fit

your rear might be at the max