Wheel Size

[Mitsu]

Hi all, I want to install a set of wheels, Schonheit M7R Front 8.5J／19in／54mm offset（8.8 ㎏） Rear12J／19in／52mm offset （11.3 ㎏）

can anyone tell me if they fit on my '92 928 GTS with correct size spacers ?

Thanks in advance ! [img]

[Rodriguezes]

I don't know what the real topic is all about but it seems to be some building that you can see here and maybe would like to know this now as read more info will help you in knowing about stuff that was always there for us to go for a better enough reason later. tellthebell

[Shifted]

I take it that you've seen and used the wheel fitment calculator?

https://members.rennlist.com/andrewmolson/Wheel_Fittment_Calculator_01-24-2008.xls

The furtherst afield from the correct offsets that I've gone are the Hollow Spoke Turbo Twist wheels:

Front: 18x8 ET50
Rear: 18x11 ET45

The fronts stuck out enough that the 225 tires would occasionally rub the fender on a really hard turn. The rears, 275 tires, nicely filled my rolled fenders (1987 S4).

I sold those wheels bought custom wheels for my summer tires.

For my winter tires, I use Carrera 3 wheels. The fronts are ET57 with 235 tires. They still aren't an ideal fit, but good enough and no rubbing. The rears are ET58 with 285's and are a bit too far inboard for my tastes, but my rolled fenders exacerbate that appearance.

Your 1992 GTS came with ET65 front wheels, same as my '87 S4, so I would expect that your planned ET54 would be ok. Not ideal, but if you're using stock 225 width tires, they should fit ok. Especially if your car is at the stock ride height.

Your rear wheels were ET55 with 35mm spacers. If you still have the same stock spacers, your planned ET52 will probably be ok with the stock tire width of 255, but with 12" wide wheels I bet you plan on gong a lot bigger than that. You may end up having to remove the stock wheel spacers and getting thinner spacers. At least that's an option in the rear, unlike in the front.

Of course, different tires have different true widths, so there may be some tires that fit better than others for you.

The biggest issue you may run into is finding tires that fit on a 19" rim but maintain the stock 25" overall diameter. It will require a very low profile, which will make the ride fairly harsh. You can fit larger diameter tires, but I wouldn't go over 26" or you may run into clearance issues with the fenders and with turning the front wheels left/right.

You can sort this all out pretty easily by comparing the fender/suspension clearance with your currently mounted wheels/tires and adding/subtracting the ET and tire cross section differences with your planned setup. Some careful measuring and a little math will give you a really good idea of fitment. Or, you can use the above calculator.

Good luck, and let us know what you end up doing.

[Mitsu]

Happy New Year ! and Thanks a lot for sharing your knowledge once again! The off-set calculator does not exactly give me my ideal fitment, and that's why I raised this question. There are many wheel variations for 911s, Boxters, Panameras, etc., but I feel I rather not use them because 928s should look independent. I am really looking for wheels that give great looks and performance, in terms of light weight and rigidity. I was wondering if I should go for 19" rims because I can use 380mm rotors in front along with bigger calipers. But you have clearly pointed out about the tire diameter issue, that has made me decide to go with 18" rims. I really appreciate your comment on this. I attached the wheels of my choice here. These are forged aluminum wheels and look rather distinctive.

[Shifted]

There was no attachment on your post, but I would love to see what you're considering. Can you provide the brand and model? I can look them up online.

The nice thing about the spreadsheet is you can change all of the numbers (wheel diameter, ET, width, etc) and compare the dimensions and fit.

Anyway, I understand what you're saying about getting a different wheel design. The winter wheels aren't important to me. They just let me drive the car when it's too cold for my summer tires.

For my summer wheels, I went with Fikse FM10's, fully polished.

Front: 18x9 ET63 (21 lbs each)
Rear: 18x10.5 ET57 (21.5 lbs each)

My summer tires are Yokohama Advan A052's.

Front: 255/35R18 (27.5 lbs each)
Rear: 295/30R18 (31.5 lbs each)

Those give me identical 25.1" diameters in the front and rear. I do wish that I had gotten the rear wheels with an ET of 54, but there was a mix-up with the ordering so I just stuck with what they sent and use 3mm spacers. Since you already have extended studs, you are in a much better position than me. You can order any reasonable offset and use spacers to get the fit just right.

I wasn't sure how I would like the wheels polished, but they really transformed the look of the car. If I were to order again, I would probably go with a different brand just to get a different look, but the Fikse wheels are extremely good quality and I'm very happy with them. If they come up with a new hub design, I would absolutely order from them again.

I'm running the "Big Red" brakes in the front with 322mm rotors, and 993 Turbo brakes in the rear with 322mm rotors. For pads the car has Hawk HPS 5.0, front and rear.

Personally, I think that it's important to look at things holistically, and with the above combination (wheels, tires, calipers, rotors, pads) and an alignment dialed in to my personal preferences, I'm extremely happy with how the car performs. I did some autocrossing in 2021 with that setup, and it was spectacular. On the street, it's comfortable on long trips on the highway, and responsive on the backroads. It's a good balance for my needs.

Another factor for me is that I've got 530hp/550ftlb to the wheels, so I really needed the right setup in the rear to get as much traction as possible. If I didn't have that much power, I doubt if I would have gone with such wide tires for the rear.

[Mitsu]

Hey shifted,

Thanks again for your info. Your wheels look great ! Please post your car to see how they look on your car. BBS wheels are nice but they are no longer unique. The magnesium forged wheels are way too expensive. So I've chosen Rays TE37 SL Front: 18" 9-45, Rear:18" 11-59. Maybe better off with 18" 8.5-50 for the front.





BTW, I am highly interested in your turbocharger set up. Can you build me what you have developed ? I can make an advance payment if it is possible. I am not in rush. If I can get it by coming April or so, I will be most pleased because the car will be out of body shop by then.

[Shifted]

The TE37 SL wheels are very nice looking! I like those and they'll look great on the 928.

Your rear offset looks ok to me, given that you can get different spacers to give you the exact fitment you want. Because I suspect that with 11" wide wheels and an ET of 59, you'll need a thicker spacer to make it fit and clear the suspension on the inside. But, that's a relatively easy adjustment to make once you have the wheels in hand, as long as you don't mind buying new spacers.

The front ET of 45 is definitely too low in my opinion, unless you really want the front wheel to stick out past the fender and risk rubbing on the fender lip under compression. Even 50 would probably be too low since you're going with 9" wide wheels. I would recommend an ET63 to ET67. But, that's just my guess

I'm sure that you have it in hand and it will come out great!

Thank you for the confidence in my ability to build you a turbo system, but I'm afraid that I can't do it. It's not my main job and I don't have the time to fabricate another system. However, I'm happy to share with you all of the details on the build, a list of all of the components, etc. Other than the time involved, I doubt if you would find it particularly challenging to build.

Below are some photos of my 928 with the Fikse wheels.

[Mitsu]

Your 928 looks great with Fikse wheels. Your car looks gorgeous in and out. Absolutely no one will recognize that your 928 produces 500+ rwhp ! GTS mirrors look nice too ! Rear ride height appears to be quite low. instead, front ride height seems a bit high compared to the rear. you set the height such a way to have more weight distribution for the rear to handle the big power of turbocharger?

Thanks for your suggestion on the ET for front wheels. I am not very sure if the front fenders on GTS are slightly flared or not. I will check it later. I don't want my wheels to stick out of fenders.

Regarding your turbocharger system, I am still highly interested, however, I am not really confident whether I can build a duplicate of your system. Maybe, I will purchase a supercharger kit available in the market. or opt for NA tuning with big cams etc. Anyhow, you just gave me an big inspiration to improve my 928, I can't thank you enough for sharing your 928 experience .

[Shifted]

My car's ride height is within factory specifications, front and rear. However, the front is actually a little bit lower than the rear to help reduce understeer and help the nose dive with trail braking. The appearance that the rear is lower is just an optical illusion, or maybe you're used to seeing 928's where they set the front too low. I promise you, the front is lower than the rear

With me in the driver's seat, the front is 51.4% and the rear is 48.6% of the weight and has a near perfect 50/50 corner balance.

The GTS front fenders are not flared, to the best of my knowledge. There was an option for front fender flares that I think was specific to Japanese cars. Let me know if you find something different.

The only currently available supercharger kit that I'm aware of is the one from 928 Motorsports. I recommend that you talk to a few people who have bought and installed the kit. My impression is that they have some strong opinions that may help guide your decision.

I look forward to hearing what you do with your car!

[Mitsu]

Thanks Shifted. I will be posting the photos once I have some progress on my 928 project.