I've heard of people running 20" wheels with a lower tire sidewall height (e.g. aspect ratio). This gives a "rubber band" look.

Has anyone tried something like 20" wheels with slightly higher tire sidewall height? For example 245/35 8.5" Front and 295/30 11" Rear?

 

20's would be bad enough. Why add more body roll with the higher sidewall?

 

What is your goal to running the higher sidewall?

 

Just curious... This is the size Porsche is using on the 991. People say that 20" wheels give a slightly harsher ride, but they always go *down* on aspect ratio to keep the overall tire diameter close to stock.

 

I saw a ferrari on 19"s yesterday with a 35 series all around.....I got to thinking why not increase the sidewall by one size....Less Road noise...

 

That's a good point.

Sometimes, when we move up a wheel size, we go with a lower profile tire that actually result is a DECREASE in overall tire diameter from the original specs. This lowers your car a few millimetres, but also decreases ride height, increases road noise (as you pointed out), and increases the wheel-well gap.

So the plus-side of higher tire side wall is reduced road noise, reduced wheel-well gap, and good ground clearance to avoid scraping in driveways. The down-side is slight increase in unsprung rotating mass. If you end up with a slightly larger diameter tire than stock, you will negligibly decrease the torque delivered to the road.

 

The 991 is a totally different car, so they have designed it to work with 20" wheels and tires.
Its not like putting 20s on a 996 or 997 which was designed to work with 19s.
Youll have to ask them what the reasoning is behind it.

 

OKB,

I think we can guess at a few reasons:
- increased tire contact patch for better cornering grip and braking grip
- visual gimmickry to make the larger car appear more compact

Assuming, for *street* driving only, our cars can handle the larger tires, couldn't we also benefit from the above two points? (Please note that I agree with others that light 18" wheels make sense for track/ performance).

What do you think?

 

I think I'm going to try the following sizes in a few weeks and let you guys know....Yes the diameter is going to increase thus slowing acceleration...But to me ride comfort, road noise and longevity of tires is key....My car has 20" rims on it so I'm going to go for a the following tire sizes....Just need to settle on a Brand that has a high tread wear rating....

245/35/20

305/30/20

I've seen a lot of Astons, Ferrari's and other exotic cars with sidewalls in the 30-35 range....So I'll give it a try...Let me know what you guys all think.....

 

Cool. I'd love to see this. Could you take before and after pictures?

Here are some calculations...

With 245/35-20" in the front, your tire diameter will increase to 679.50mm. (This is an increase of 31.90mm from stock 19" wheels/tires). This will increase the ride height by 15.95mm in the front.

With 305/30-20" in the rear, your tire diameter will increase to 691.00mm. (This is an increase of 31.40mm from stock 19" wheels/tires). This will increase the ride height by 15.70mm in the back.

Now, if your car is lowered, the ~1.5 cm ride height increase just wont be visually noticeable, and your wheel-well gap will be nicely reduced.

 

if youve ever had alot of different tires and wheels and measured them, youll find the factory spec measurements are inaccurate, as to height and width. They may say 25.6" OD but in may end up being 25.9 or any other dimension and dependent on wheel width, air pressure, etc

 

The contact patch area is a function of only tire pressure and vehicle weight. When you go to wider tread width, you end up with a different shaped patch but the area of contact has to stay the same. A bigger diameter tire would have less deformation at the contact patch so maybe it means less heat buildup?

That said, there is obviously a trend toward larger overall rolling diameters over the years. It sure looks better to my eyes -- more athletic and aggressive. However it must be increasing unsprung rotating mass, which is the absolute worst kind of weight to carry on a car for performance.

 

20s on a 911 IMO just isn't a good look, I mean to each his own but this is a sports car not a cruiser!

 

Hey all...I ordered these tires today and will let you know specifics once the tires are mounted on the car....


305/30ZR20 Bridgestone Potenza S001

245/35R20 Bridgestone Potenza S001

 

Azqureshi,

Please remember the before and after pictures! After they are mounted, let us also know if you feel a difference in acceleration, cornering, stopping, and ride comfort.