19" wheels on 944
03-26-2004, 12:44 AM
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Originally posted by IanM
First of all...Porsche never offered 17" wheels for the 944...at least not that I've ever heard of. Yes, they were offered with the 968.
The deal with the steering rack is two-fold. First off, 18" tires/wheels tend to be heavier than 17" or 16", even with the same overall diameter (okay...unless you ponied up the cash for some nice forged 18" Fikses...). That increased unsprung weight adds stress to the suspension and steering components. Secondly, many people running 18" wheels end up with a larger rolling diameter. If this is combined with a lowered ride height, the geometry of the control arms and tie rods can be altered - ie. they can actually be higher at the wheel end than at the chassis end. This can also cause increased stress on these components.
First of all...Porsche never offered 17" wheels for the 944...at least not that I've ever heard of. Yes, they were offered with the 968.
The deal with the steering rack is two-fold. First off, 18" tires/wheels tend to be heavier than 17" or 16", even with the same overall diameter (okay...unless you ponied up the cash for some nice forged 18" Fikses...). That increased unsprung weight adds stress to the suspension and steering components. Secondly, many people running 18" wheels end up with a larger rolling diameter. If this is combined with a lowered ride height, the geometry of the control arms and tie rods can be altered - ie. they can actually be higher at the wheel end than at the chassis end. This can also cause increased stress on these components.
If you are familiar with plus concept, the idea is to increase the wheel diameter and decrease the tire sidewall height to preserve the same rolling diameter...The weight differences are either neglible or actually there is a reduction in the wheel weight (wheel technology did advance over years...), plus the tire weight is reduced from that lower sidewall height...
Thus, the problems you have indicated are not applicable...
03-27-2004, 12:57 AM
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Yea, but even if they're the same weight, the rotational moment of inertia will be further out from the center with a bigger rim and essentially make the wheels harder to accelerate or decelerate (stress on drivetrain and / or brakes) and induce a larger gyroscopic precession in the rotating disc. Not to mention the obvious problems of getting them to fit correctly and not rub against fenders (although these problems are fixable enough).
03-27-2004, 01:05 AM
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Originally posted by Porsche-O-Phile
Yea, but even if they're the same weight, the rotational moment of inertia will be further out from the center with a bigger rim and essentially make the wheels harder to accelerate or decelerate (stress on drivetrain and / or brakes) and induce a larger gyroscopic precession in the rotating disc. Not to mention the obvious problems of getting them to fit correctly and not rub against fenders (although these problems are fixable enough).
Yea, but even if they're the same weight, the rotational moment of inertia will be further out from the center with a bigger rim and essentially make the wheels harder to accelerate or decelerate (stress on drivetrain and / or brakes) and induce a larger gyroscopic precession in the rotating disc. Not to mention the obvious problems of getting them to fit correctly and not rub against fenders (although these problems are fixable enough).
The benefits in handling gains far outweigh the negatives, and this is based on personal observations since I have actually done this...
