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Old 12-30-2010, 11:12 AM   #1
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18" wheels on a '97?

I have been looking for a Boxster and reading this forum for months now, I finally found one that has everything I have been looking for except it's a '97. I really want to lower the car 1" and add 18" aftermarket wheels.

I have read about the '97's not having enough bracing for 18" wheels. Is there any mod like aftermarket bracing that wont break the bank I can do to add them?

TIA
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Old 12-30-2010, 12:27 PM   #2
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You should check out this recent thread .
Rim Size for 1997 Boxster
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Old 12-30-2010, 12:39 PM   #3
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Bad idea. The 97 should not run 18" as several key suspension mounting points and the engine bulhead area are not strong enough to handle it, and modifying the car to prevent metal structure failure is very expensive. Cheaper to buy a later car...........
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Old 12-30-2010, 03:26 PM   #4
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Quote:
Originally Posted by JFP in PA
Bad idea. The 97 should not run 18" as several key suspension mounting points and the engine bulhead area are not strong enough to handle it, and modifying the car to prevent metal structure failure is very expensive. Cheaper to buy a later car...........
JFP,
As one of the most astute members of this forum, I value your opinion. However, it seems that the caveat for the 2.5 platform is that its suspension lay-out and structure is not designed to withstand the additional weight and load bearing that a larger diameter wheel would presumably create. What do you think of the concept of using a light weight after market wheel to reduce unsprung weight and rotational mass in order to mitigate this concern ?[/QUOTE]

Won't work on the 97 car as it is not a weight issue, but one of mechanical leverage; the body structure is not designed to deal with the mechanical leverage the large diameter wheels put on the chassis at the suspension mounting points (think of a larger diameter wheel acting like a longer breaker bar). The bigger diameter wheels also cause the car to twist more, cracking the welds in the forward bulkhead ahead of the engine. Excellence magazine did a good article on this problem not long ago if you’d like to learn more about it.[/QUOTE]

Now that makes sense to me. Thanks for the clarification. Do you mind if I post our discussion so others may understand this issue as well ?[/QUOTE]

I have no issue with you posting it, just be prepared to get into a full blown discussion of vehicle dynamics. While the weight of a wheel/tire combo does matter, even if you found an 18 inch setup that was actually lighter than the smaller wheel/tire, say the 18” Carrera ultra light five spokes and some tire, and this combination that retained a constant contact patch area (the area of the tire actually on the road), the car will still see increased torsional and leverage mechanical loads. Then you need to factor in the wheels “measured diameter” against its “effective diameter” (larger diameter tires have stiffer sidewalls, make the small increase in the measured wheel diameter seem even larger to the vehicle), and so on. Increase the measured contact patch, or use a stickier tire, and the effective diameter increases even more, increasing the loading of the chassis.

Ain’t chassis dynamics fun?[/QUOTE]

I agree that posting this discussion will likely trigger some armchair experts to espouse their view points . Still, I think that it would informative for a lot of 2.5 owners contemplating changing their wheel size .
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Last edited by Johnny Danger; 12-30-2010 at 03:29 PM.
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Old 12-30-2010, 05:20 PM   #5
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Well, I have a 97, I'm running aftermarket 18 inch Carrera lights (not nearly as light as Porsche wheels either) and my car is lowered 1.5 in the rear and 1 in the front.

I even drove the piss out of the car on a track with these rims on it and had no frame damage.

If you ask me, this was Porsche doing some serious CYA. Slauson, on the Porsche web site Q & A section, commented that he did not see it being a problem as long as the car was being flogged on a track with 18's on it.

Ooops.

I wouldn't let the fact that the car is a 97 keep you from buying it. I would, however, caution you not to buy a 97 that has not had just about every freakin' part on it replaced already with receipts to prove this fact.

The motor should not be original, nor should the coolant overflow tank, and the list goes on and on and on.

Save up and buy a newer S model. What you spend in repairs on a 97 in the first two years will be more than enough to buy a 2000 S in two years.

Seriously. Don't do what I did unless you have found a meticulously cared for 97 with a very fat folder full of receipts and the 2.5 scares the crap out of you and you would never want more HP.
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Last edited by RandallNeighbour; 12-30-2010 at 05:22 PM.
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Old 12-30-2010, 06:31 PM   #6
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Well, perhaps you were lucky. Over the years, I've had two 97's pass thru the shop, one on 18's, one on 19's, and both with the exact chassis problems mentioned in the Excellence article, neither had ever been on a track to my knowledge. Neither was easily repairable (one I believe was eventually parted out). I would also note that there is a lot of chatter amongst the Spec Boxster crowd against buying the 97 chassis for the same reasons. Can't all be a myth................
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Old 12-30-2010, 07:35 PM   #7
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JFP, how did you know you had subframe issues on your 97's?
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Old 12-31-2010, 05:37 AM   #8
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From our records, “Metal fatigue type cracks or splits in the metal, some around the suspension mount areas", on the worst one "there are significant cracks in the driver’s side forward bulkhead area, near with the rear chassis meets it.”

Of all the Boxster model years, 1997 is the one we see the fewest of, probably due to age and the fact there were not that many of them to begin with. Currently, our active customer base only contains a couple of them. To see two with metal fatigue failures out of such a small "sample" has to be considered unusual.
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Old 12-31-2010, 03:56 PM   #9
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18s are fine on a '99 right?
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Old 01-01-2011, 07:08 AM   #10
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As of the '98 model, Porsche strengthened the rear of the car by using thicker gauge metal in the problem areas, eliminating the issue.
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Old 01-03-2011, 07:55 AM   #11
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has anyone got pics of the mentioned failures?
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Old 01-03-2011, 11:04 AM   #12
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We didn't keep any as both the current and perspective owners where present during the PPI's.
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Old 01-04-2011, 09:26 PM   #13
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Hmmm, good job I fitted 19's instead of those pesky 18's you mentioned!!

I have visions of the start of the 6 million dollar man...."we have separation.....I got a blow out......engines out......I can't hold it, she's breaking up...she's breakin..." lol

You can put 19 inch + rims on very nearly every car on the planet and all your worry will be is "I hope this **************** don't rub" put them on a 97 Boxster and all you worry about is can you fit all the parts that drop off in the trunk? if there IS a trunk!

Porsche "quality" is kinda getting old!

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Old 01-06-2011, 08:58 PM   #14
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well I had a GOOD look round and I can't find anything on mine, although i've only done approx 3000 miles on my 19's, well in fact I've only done approx 5000 miles in the past 3 1/2 years!!! lol

Toys eh!
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Old 01-07-2011, 05:40 AM   #15
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Quote:
Originally Posted by jonnycool
Hmmm, good job I fitted 19's instead of those pesky 18's you mentioned!!

I have visions of the start of the 6 million dollar man...."we have separation.....I got a blow out......engines out......I can't hold it, she's breaking up...she's breakin..." lol

You can put 19 inch + rims on very nearly every car on the planet and all your worry will be is "I hope this **************** don't rub" put them on a 97 Boxster and all you worry about is can you fit all the parts that drop off in the trunk? if there IS a trunk!

Porsche "quality" is kinda getting old!
When Porsche designed the Boxster, they were very concerned about weight. Unfortunately, the market’s desire for bigger wheels exceeded the capabilities’ of the metal thickness they originally choose. And this is not that uncommon in the automotive world; Nissan currently is recalling several model year Altimas because the all aluminum rear sub frame and cross members are breaking up for the same reason. “Fecal matter occurs”……even when you have some of the best engineering on the planet working for you.
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Old 01-08-2011, 02:00 AM   #16
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Originally Posted by JFP in PA
When Porsche designed the Boxster, they were very concerned about weight. Unfortunately, the market’s desire for bigger wheels exceeded the capabilities’ of the metal thickness they originally choose. And this is not that uncommon in the automotive world; Nissan currently is recalling several model year Altimas because the all aluminum rear sub frame and cross members are breaking up for the same reason. “Fecal matter occurs”……even when you have some of the best engineering on the planet working for you.

Hmmm... so lots of 97 owners IN 1997 went out and bought 18" rims, lots of them reported the mentioned failure so within say a few months they chose thicker metal for the 98 model? This is an "over time issue" these fractures never appeared in the first year I bet.

They knew about it way in advance what would happen because they changed the design for 1998!

I'm not trying to get in a big argument but I just find it a real ball ache when these flash companies know that there is something wrong but still ship it out anyway! RMS anybody? IMS.......... all the other "quality" brands are just as bad, just mention multitronic to an out of warranty Audi owner!!!

A quality vehicle lasts the test of time, pre late 90 Mercs and Audi's are pretty good as were the older Saabs. Toyota landcruiser?

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Old 01-10-2011, 03:10 PM   #17
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Is this case really happening? Or is it just a few of all the 97's out there? So if I fit an 18 on my 97 then for sure 99% it will happen to me too?
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Old 01-11-2011, 11:16 AM   #18
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Your money, you car, your choice, your risk

In my list of model year differences I mention for the '98 "Rear body structural change included redesigned wheel wells and coil spring mounts, lower engine compartment bulkhead, rear wall crossmember and rear axle mount reinforcements." Probably that list came from an Excellence magazine discussion of the early MY Boxsters.

Why would Porsche do all that if they didn't discover in post-production testing of the '97s that there was a need for it? Recall Porsche was in financial trouble at the time and so spending extra to redesign something wasn't something they really wanted to do.

My guess is that around the time the '97 was designed the low profile tires and bigger wheels craze hadn't hit yet. And Porsche was offering a 17".
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