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18" on ´97 Boxster 986

Hi

I have been offered a set of 18 "Boxster SII wheels for my 97 986

Current wheels

Front 205/50-17X8 ET 49
Rear 255/40-17 x 9,5 ET 52

New Wheels

Front 235/40-18 x 8 ET 57
Rear 265/40/18 x 9 ET 43

Question is will the new ones fit without rubbing
One concern is that the calculated difference in Circumference on the New front/ rear tyres is app 3,8 %, will that influence ESP and ABS??

BR
Barthol

Porsche specifically warns against 18's on the '97 Boxster, they weigh too much for the suspension.

http://986forum.com/forums/performance-technical-chat/4536-will-18-wheels-work-1997-boxster.html

Quote:

Originally Posted by rick3000 (Post 586783)

Porsche specifically warns against 18's on the '97 Boxster, they weigh too much for the suspension.

http://986forum.com/forums/performance-technical-chat/4536-will-18-wheels-work-1997-boxster.html

That's like saying "moms weigh too much". Some (many) 18's are lighter than the 17's currently on the car. I'm not familiar with the wheels the OP is talking about, but until he's looked at weight comparisons, you can't just whip out a "no".

Regardless; i'd contend that in regular usage, a little extra weight is not a problem. The harder you work that suspension, the more the weight difference means.

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Quote:

Question is will the new ones fit without rubbing
One concern is that the calculated difference in Circumference on the New front/ rear tyres is app 3,8 %, will that influence ESP and ABS??

I think that barthol is looking for info specifically about fitment of that size and offset, and I know we have people here who can answer that.

Sadly, I am not one of them.

I will offer more unsolicited advice though...

The issue with the early Boxsters and wheels larger than 17" mostly has to do with the rear sub-frame brace. On the 1997 and early 1998 cars it was weaker and prone to cracking.

Quote:

Originally Posted by itsnotanova (Post 576473)

Breaking those is very common on 97-mid 98 boxsters. Starting somewhere in 98 Porsche upgraded to a beefier rear subframe. That's also why it's not recommended to install large wheels of the early cars. I highly recommend replacing both if you ever break one. Like it was said earlier, you'll have to get it realigned after you replace it. Might as well upgrade both while you're at it. I sell them for $50 each plus shipping. The beefier rear subframes break easily, just not as easy as the early ones. The front subframe is slightly different on the early cars too, but I've never seen anyone break those easily.

For wheels I like to check here for info: 944racing
But the information is incomplete for those specific wheels (Boxster S II).

Hopefully someone who knows the offsets and fitment better will come up with a useful answer soon.

Will 18s fit, yes. No idea if these specific ones will.

Here are the specific changes they made in 1998 to safely use 18" wheels on the 986.

"18” wheel option with rear chassis reinforced to accept new wheels. Rear body structural change included redesigned wheel wells and coil spring mounts, lower engine compartment bulkhead, rear wall crossmember and rear axle mount reinforcements."

For tooling around town and local drives, they will probably work. Don't go onto the track or try any autocross or similar stressing maneuvers.