Tire Advice

Guys,

Looking to buy some new tires for my 1986.5 225/50 - 16 . Only use in summer months. Any recommendations?

Hey Brian, this should be in the gen or tech section but oh well
I bought these the first time around but they were to soft



I bought these off of Malcolm and the Mich/pilots are a much better tire




be right back

Here is a good post from another forum

For the rears I start with what I have on my 17 by 9 inch wheels with 47 offset. They give me about a half inch clearance from the tire to the fender flange on my S87 S4. I use 255 40 17 tires on the rear.

With your new wheels you are going to 65 offset with a one inch wider wheel. That means that outside of the center line you have a half inch more width or about 12 mm. The wider offset of 65 puts the wheel about 3/4 inch (18mm) further inside the wheel well. About a half inch of that offset is taken up by the extra width, so without a spacer, your wheels/tires will be about 3/4 inch from the fender flange on an S4.

The next consideration is the outside diameter you are looking for. I think you need to stay in the range of 25 to 26 inches for the rear. Since 10 inches of width is 254 mm, when you add some for the flare of the tire, you should be looking for about a 275 width tire. Since you have 18 inches of wheel diameter, and you are looking for less than 26 inches, you need a percentage profile of the width that will give you that.

With a 265 width, a 40 percent profile will give you two times about 106 mm or 8.35 inches. When added to the wheel diameter you will end up with 26.35 overall diameter. I think that is a little too tall.

A 265 by 35 will give you 25.3 overall height. That is pretty good, but I think you really want a slightly wider tire. Lets look at a 275 by 35. That give you 25.58 overall diameter which I think is just about ideal. Also I think that will put the tire about 3/4 inches from the fender flange on an S4.

What you will need to do is move the wheel/tire assembly out closer to the fender flange. I think you will need a spacer of about 10 to 12 mm. Fifteen, as you anticipated will also probably work. Therefore, the answer is 275 35 18 rears. Good hunting.

Jerry Feather

There is a tire calculator but I think it is down so I didn't post the link.

Main thing is lets have the details on the car and someone will jump in to help. what size rims, whats on it now, year of car and anything else that may affect the size.

Brad

Sorry for posting in the wrong area. Still getting used to the site. Appreciate the insight on tires.

No problem Brian, ILL move it later.

I just found this Porsche 928 original Tire and Wheel sizes database listed by year

I googled 928 tire sizes

www.tiretips.net/tire-guides/porsche-928-tires.html

but for buying tires, I have good luck buying them here
www.tirerack.com/index.jsp
and
www.discounttire.com/dtcs/home.do

Michelin Pilot Sport S - I put those on when I bought it and had it nicely aligned by a shop that knows and has a pit (do not lift if possible). Don't want to lose 800.00 worth of rubber on a bad alignment....

They are great in dry and wet. Firm but not harsh. So far I really like them. Should have good mileage in them as well.

I have Hankooks on my 87. Great ride and handling. Watch the tire pressure you run. The recommended pressure from porsche are high. If you increase your rim size and use lower profile tires you must reduce tire pressures or the new rubber will wear prematurely.