Going from 19" OEM wheels to 20" Champions. Good Idea?
07-28-2012, 04:49 PM
#16
Nordschleife Master
20" wheels significantly negatively effect a car's handling, acceleration, and braking. In my eyes that is the most important concern.
Even if you buy a top of the line forged 20" wheel that isn't particularly heavy, the Moment of Inertia still increases and needed tire flex decreases. Both are bad things.
The idea is to have equal tire sidewall distance front to back. There is a reason many very high performance automobiles run double staggered wheel set ups. Basically an 18" in the front and a 19" in the rear. As a bonus, the optical illusion where it appears the front rim is actualy larger than the rear rim (because of the smaller front sidewall) goes away and the wheels look completely equal.
And it's a Porsche so nothing but Forged wheels will do imo. I prefer BC Forged wheels personally because they are 100% custom, any offset, and width, any finish, etc...
Good Luck!
Even if you buy a top of the line forged 20" wheel that isn't particularly heavy, the Moment of Inertia still increases and needed tire flex decreases. Both are bad things.
The idea is to have equal tire sidewall distance front to back. There is a reason many very high performance automobiles run double staggered wheel set ups. Basically an 18" in the front and a 19" in the rear. As a bonus, the optical illusion where it appears the front rim is actualy larger than the rear rim (because of the smaller front sidewall) goes away and the wheels look completely equal.
And it's a Porsche so nothing but Forged wheels will do imo. I prefer BC Forged wheels personally because they are 100% custom, any offset, and width, any finish, etc...
Good Luck!
07-29-2012, 09:24 AM
#17
My only comment is with the 991, 20" wheels were used for the brakes and the whole car was designed the run on 20. 19's will of course improve ride somewhat. Just like 997's were designed to have the 19" wheels. 18's will improve the ride somewhat
07-29-2012, 09:41 AM
#18
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This is a very vague statement.
Did you compare your 20" wheels to the same brand, style, width rim, and the same model tire but in an 18" back to back? Because if you had, you would have been positively shocked at the improvement going to the 18s.
For all we know you swapped a 34# 19" wheel for an 18# 20" wheel making any comparisons completely invalid.
Obviously when one makes this comparison, one has to assume identical OD tires, same model tires, and the same rims. Altering any of those factors , combined w/ driver's that can't feel when they have a flat tire, much less 20 lost hp, make all of these factors important to conduct a direct comparison.
If you purchased a lightweight 18" rim, then you slapped on some lightweight tires (i.e. Conti DWs or MPSS) I promise you that even the most unaware driver would feel the difference compared to a 20".
What's funny however is that at this point we are just argueing about math. It's not negotiable that increasing the Moment of Inertia increases gyroscopic effect and therefore decreases performance. At least not in my facts driven world.
Did you compare your 20" wheels to the same brand, style, width rim, and the same model tire but in an 18" back to back? Because if you had, you would have been positively shocked at the improvement going to the 18s.
For all we know you swapped a 34# 19" wheel for an 18# 20" wheel making any comparisons completely invalid.
Obviously when one makes this comparison, one has to assume identical OD tires, same model tires, and the same rims. Altering any of those factors , combined w/ driver's that can't feel when they have a flat tire, much less 20 lost hp, make all of these factors important to conduct a direct comparison.
If you purchased a lightweight 18" rim, then you slapped on some lightweight tires (i.e. Conti DWs or MPSS) I promise you that even the most unaware driver would feel the difference compared to a 20".
What's funny however is that at this point we are just argueing about math. It's not negotiable that increasing the Moment of Inertia increases gyroscopic effect and therefore decreases performance. At least not in my facts driven world.
