Rim Size for 1997 Boxster
 

New Member ! Hello to Everybody ! What is the largest Rim size I can put on my Bosxter. I love the new Sport Classic but only see in a 19 in. Will they fit ? Thanks,

A commonly shared opinion amongst boxster owners, is that the 2.5 variant cannot sustain the additional weight and load bearing that is imposed by a heavier, larger diameter wheel . Perhaps, some 2.5 owners can chime in .

Well actually
 

Porsche found that the '97 Boxster would have problems with 18" wheels under certain situations and in '98 did a major strengthening of the body, mounts and suspension in the rear.

So I'm not so sure you want 19s. I've heard of people using 18s for daily drivers.

1G Turn
 

I had heard that there were not only fitment issues but technicial ones as your describing. I'm really trying to find Rims that look like the New Sport Classic by Fuchs in a 17 in or 18 in are they out there somewhere ?

My 97 runs fine on 19's :) nice to drive, not as agile but seems smoother somehow, and all I do is drive on twisty country roads. I could do with lowering mine an inch though.

If Porsche's reasoning for discouraging the use of larger diameter wheels on the 2.5 platform is largely in part because they feel that the additional weight and increased load bearing can compromise the vehicle's suspension; then regardless of size, this concern can be mitigated by simply utilizing a wheel set that reduces unsprung weight and rotational mass . That would be my thought .

only pics I can find at the min my hard drive went down a while back and lost most of them

97 to 98 changes
 

Rear body structural change included redesigned wheel wells and coil spring mounts, lower engine compartment bulkhead, rear wall cross-member and rear axle mount reinforcements.

Doesn't sound to me like Porsche thought just lighter wheels was the solution as this was to allow 18" wheels, not 19" or 20".

Other downsides of larger diameter wheels are the cost of tires and the increased risk of something penetrating through the tire and destroying the wheel.

Mike,

With all due respect, your logic is erroneous. If indeed the prevailing concern is that the 2.5's suspension was not designed to support the increase in weight and additional load bearing that a heavier, larger diameter wheel would presumably impose, then its logical to think that by substantially decreasing unsprung weight and rotational mass one could not only rule out this concern, but, perhaps improve the performance of the vehicle. The misconception here is, that larger diameter wheels weight more. While this can be true of most oem wheels, and this would explain why Porsche discouraged the use of larger wheels on this model, it's clearly not the case with many of the high quality after market wheels that are available. Indeed, depending upon the the wheel application, boxster enthusiasts can reduce unsprung rotational weight considerably on their vehicle. Take it from some one who has done this. By upgrading to a light weight one piece forged wheel, I eliminated nearly 100 lbs. of unsprung weight/rotational mass from my vehicle. And, the effect it had on handling, braking and overall performance was nothing short of transforming !!!

Just a thought but would front and rear strut braces help relieve any stresses that might occur with larger diameter wheels? obviously porsche cannot do this as it limits access to both luggage compartments but I would say this would be a good upgrade for anyone that may be a little worried by this phenomenon. Personally I still think you would be pretty unlucky if your rim size induced damage to your car.

Negative. The only real benefit to strut braces is that they tend to solidify "cowl shake" that's often associated with convertibles .

40+ lb. wheels on a Boxster WOW good thing you got those off your car

+1 on reducing weight and unsprung mass to mitigate the loading from a 18" setup.

Key would be to ensure that the 18" tire/wheel combo had the same or less weight, along with same diameter/circumference, as the 17" setup.

If these conditions are met, the suspension should be loaded similarly between the 17" and 18" setups.

"By upgrading to a light weight one piece forged wheel, I eliminated nearly 100 lbs. of unsprung weight/rotational mass from my vehicle."

+1 :)
Would really like to see the math on that. My stock OEM 17" fronts weigh 19.5 lbs, rears weigh 21.5 for a total wheel weight of 82lbs. In order to lose 100lbs with lightweight new aftermarket wheels they would have to be made of pure hydrogen.

Were the bulkhead mods ect.. made by porsche in early to mid 98's or late 97's?
The boxster has been around since late 96 so I just wondered if there are a few early 98's to be aware of that may have this problem or that ALL 98's are ok and also a few late 97's could have had the upgrades?

I believe the main concern was increased torsion load from the reduced sidewall height & presumably higher performance tires.

I've just checked my VIN number as i knew it was a late 1997, I think mines ok for larger rims as the number is

WPO ZZZ 98 Z W S 6 ****

Am I right in saying that my car is a 1998 model? I have the original bill of sale for 28/11/97
The bill also states that the order was placed on the 26/09/1997 so there was only a 2 month wait for a new boxster in the UK back in 1997.

What off set are you running, I need a set of track tires and want to get something without spacers,,,,I have 25mm spacers on the rear to get my turbo twists to work

The factory recommendation against using 18" or larger dia wheels was for the '97 model year only (North American market model year 1997) and it was due not only to wheel tire weight but as mentioned earlier the additional stress caused by larger dia wheels and shorter profile tires.

Simply running larger wheels with equal weights to 16" or 17" wheels will not prevent the possibility of damaging the suspension / body mounting areas that were strengthened on '98 and later years.

That said I use 18" MY02 wheels that I use in the summer for street use. I've read that the PCA Boxster tech adviser said that there is "probably" little risk in running the 18" wheels on '97s when used on the street. The suspension will see greater forces on the track regardless of what wheels sizes are used, especially when R compound tires are used, which is also not recommended by Porsche.

I’d be interested in seeing photos of the affected areas and the damaged caused by running larger wheels, so that I could monitor the condition of my car and possibly catch a potential problem early on.

Aron

I agree with the PCA adviser's theory. I would get some quality time underneath my car
to study the firewall & wheelwell areas so you can recognize any bending,cracking, movement of the underbody struture.