Rim Size for 1997 Boxster

[Johnny Danger]

Originally Posted by mikefocke

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 !!!

[jonnycool]

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.

[Johnny Danger]

Originally Posted by jonnycool

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 .

[BYprodriver]

Originally Posted by Johnny Danger

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 !!!

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

[thstone]

+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.

[BYprodriver]

Originally Posted by thstone

+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.

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

[jonnycool]

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.

[Topless]

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

Originally Posted by BYprodriver

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

+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.

[jonnycool]

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?