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By ChrisZ
#67879
Well I think it's not going to snow anymore in MD so I decided to switch out the tires on the 86.5 928S. Back in the fall I bought 4 new Blizzak tires and rims so I would not die in the snow. They're on 16 inch pie plate rims and are 225/60R16 tires.

Image

They make... noises. First, they *fill* the wheel wells, to the point that when I come into the driveway and go over the little hump while turning I can hear the rear tire rub slightly against the wheel fender. More importantly, the front tires will just barely rub against the plastic brake ducts when making a tight turn in a parking lot. This is not due to wheel turning stops as trying to steer without making the noise leads to wide turns that are far greater than any other car I have ever owned. Not a big deal, I lifted the front back up to the low end of factory settings and I can probably drop 10 pounds of pressure on the tires to make them a bit smaller.

However my car is weird: The Previous Owner did a lot of odd stuff with it (insane lowering, etc) and one of the odd things is it has Continentals 225/50ZR16 tires front and back. Also the rear two rims are different from the front rims, they are a bit wider but have the same size tires as the front.

Image The tires.

Difference between the rear tire rims and the normal 16 inch rear rims:
Image

When I got the car I just put on new tires of the same size and enjoyed it. Now the "summer" tires are shot, and I need to replace them.

Question: What do I replace them with? Do I go with the 50's all around? 60's? Should I be using a wider tire on the rear if I have the wider rims? It's an 86.5 so it has the 87 and up suspension and that might include different brake ducts (maybe they did them different in 86.5 due to the difference in brake discs and the like, I don't know.) The rear wheels do have spacers behind the tires, and they look to be factory.

Thanks!
Chris
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By ChrisZ
#67883
Edit: NTB.com says it's a 225/50VR16 tire. Tirerack says it's a 225/50ZR16 default but other sizes can be 225/50ZR16 front, 245/45ZR16 rear.

Checking NTB.com again for an 87 shows 225/50VR16 front, 245/45VR16 rear.
Would that be a better combo?
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By Rdon
#67887
Page 82 of the Porsche Technical Specifications booklet, 928S Models 85,86 and 928S4 Models 87,88,89.

Note the tire size vs. rim size. You can verify your wheels specs and go from there.


Image
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By Erik N
#67888
One advantage to running all-identical-size tires is the ability to put them on any corner of the car. Also, all things being equal, I will take a non-directional tire over a directional one every time, so they can run either direction. (Plus, my car seems super sensitive to "V" shaped tread patters. Some will literally "buzz" while driving.) Also, once you get to know the car you will be able to feel if one corner loses air. The 928 platform is that good.
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By MFranke
#67955
225/50 for the front should be available. There is not a lot of selection for 245/45 for the rear; however, 245/50 works fine for the rear and is available. The speedo will read slightly low, and the size is slightly larger. Though, you can get a good, modern tire in 245/50.

928's do not have a lot of room for upsizing in the front. The tires will rub when turning the wheel. I stick with 225/50s in the front (for 16 inch rims).
ChrisZ liked this
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By ChrisZ
#67964
Ok, then I got the wrong snow tires for the car. That would explain the rubbing.

I see Continental does not sell a 245/45 in 16 inch anymore, how are the Pirellis P0's these days?

Also where can one find the stamping on the rim to make sure I have the right ones. Is the 17mm "washer" the spacer that's on the back?
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By ChrisZ
#67968
MFranke wrote: Sun Mar 21, 2021 8:01 pm 225/50 for the front should be available. There is not a lot of selection for 245/45 for the rear; however, 245/50 works fine for the rear and is available. The speedo will read slightly low, and the size is slightly larger. Though, you can get a good, modern tire in 245/50.

928's do not have a lot of room for upsizing in the front. The tires will rub when turning the wheel. I stick with 225/50s in the front (for 16 inch rims).
That does cut the price in half, any experience with the BF Goodrich tires? Mostly fast driving and Autocross here these days.
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By worf
#67988
ChrisZ wrote: Sun Mar 21, 2021 8:51 pm Is the 17mm "washer" the spacer that's on the back?
Yes.
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By MFranke
#68015
That does cut the price in half, any experience with the BF Goodrich tires? Mostly fast driving and Autocross here these days.[/quote]

Yes, I've used the BF Goodrich and have been very happy with them. Conti DWS have also been good.
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By Geza-aka-Zombo
#68016
I have the Pirelli P0 Rosso - I'm happy with them other than the fact that they are very expensive. $1K/set

Another option would be to get another pair of 7 x 16 rims and go with 225s F&R as the factory specified.
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By ChrisZ
#69392
Well, I decided to "do the right thing" and got the Pirellis. Had the local NTW do the install and man they just screwed it up. Didn't seem to get there were front and rear tires, but we got it all sorted out and now I'm wondering if I should just get a tire mounting machine for my shed (if you want it done right, you need to do it yourself)

On the positive side they look great, fit properly, and the car no longer rubs the tires. Once the suspension settles (100 miles of driving) I'll take it in to check the alignment and I should be set till the winter!

Thanks everyone.

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