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Installed RS Wheels on my 991.2 GT3, also Porterfield R4-S Pads, Steering Wheel Trim

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Installed RS Wheels on my 991.2 GT3, also Porterfield R4-S Pads, Steering Wheel Trim

 
Old 12-21-2018, 01:53 PM
  #31  
Brosef
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how come the picture in the diagram shows 12.5" of width but the data beneath it shows 12.8"?
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Old 12-21-2018, 01:55 PM
  #32  
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Originally Posted by Brosef View Post
how come the picture in the diagram shows 12.5" of width but the data beneath it shows 12.8"?
I think 12.5" is the wheel and 12.8" is the tire.

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Old 12-21-2018, 02:15 PM
  #33  
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Originally Posted by GrantG View Post
I think 12.5" is the wheel and 12.8" is the tire.
Yup
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Old 12-22-2018, 12:58 PM
  #34  
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Originally Posted by dieselino View Post
Rake does not change, please read the post. Rolling diameter is the same as stock GT3, not RS . I didn't use RS tire sizes. 21s don't change anything since I went down an aspect ratio with the tire .
That would be incorrect, there is a +3mm overall change in the height of the tire from the 20" (305/30/20) to the 21" (325/25/21) in the rear - this would be evident by many things including revolutions per mile, tire height, overall circumference. Therefor, the rake has changed in the positive from the 20" wheel to the 21" wheel setup - thus you've increased rake. When talking rake, mm's are decent size changes.

The solution to keep that size wheel on the car would be to drop the ride height in the rear to compensate for the bigger tire height (reduce your rake back down), and now you are running a wider tire in the non-RS wheel well which I suspect if pushed hard (track day, DE) you would start to see rubbing once its truly setup to OEM spec with the bigger wheel set installed. But as you said, you've got the OEM (non-RS) wheels for the track, so probably not a huge need to adjust that given the RS wheels are being used on the street only.
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Old 12-22-2018, 02:18 PM
  #35  
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Originally Posted by redmonkey928 View Post
That would be incorrect, there is a +3mm overall change in the height of the tire from the 20" (305/30/20) to the 21" (325/25/21) in the rear - this would be evident by many things including revolutions per mile, tire height, overall circumference. Therefor, the rake has changed in the positive from the 20" wheel to the 21" wheel setup - thus you've increased rake. When talking rake, mm's are decent size changes.

The solution to keep that size wheel on the car would be to drop the ride height in the rear to compensate for the bigger tire height (reduce your rake back down), and now you are running a wider tire in the non-RS wheel well which I suspect if pushed hard (track day, DE) you would start to see rubbing once its truly setup to OEM spec with the bigger wheel set installed. But as you said, you've got the OEM (non-RS) wheels for the track, so probably not a huge need to adjust that given the RS wheels are being used on the street only.
The very slight increase in rolling diameter on the rear from going to 325 vs 305 still doesn't change the rake because the front increased the same amount from going to a 255 vs 245. The change is so minimal it wouldn't change things much. Also remember that a 325mm tire from one brand will measure different from a 325mm from another. When calculated actual tire width and actual tire rolling OD, there is also a margin for error . It is never an exact measurement.
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Old 12-22-2018, 02:29 PM
  #36  
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So... what are you actually gaining here if all you've done is changed the size of the wheel, but you've gone with tire sizes that maintain the same rolling diameter? Just a 1/2" wider tire? The contact patch hasn't actually changed. You've increased tire width by 1/2" but the weight of the car is now spread over more surface area, so you've decreased the contact patch's length while increasing it's width = no change in surface area (unless you've gone with lower tire pressures). You're also using lower performance tires and you've said you didn't do this for any performance gains. And since the rolling diameter hasn't changed, you haven't actually filled out the wheel well any more. You've just increased the size of the wheel inside the tire. So the wheel gap is the same unless you lower the car.

So the only real reason to do this is to get the look of a bigger wheel inside the circumference of the same rolling diameter tire? But you're still left with the same wheel gap.

I'm not ****ting on your decision here. Just trying to understand what the net effect/benefit is. Especially since these wheels are about $3K each = $12,000 for a set.

I guess you've also pushed the face of the wheel out a little bit as well without having to use a spacer, giving the look of a wider wheel base.
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Old 12-22-2018, 06:20 PM
  #37  
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Originally Posted by FourT6and2 View Post
So... what are you actually gaining here if all you've done is changed the size of the wheel, but you've gone with tire sizes that maintain the same rolling diameter? Just a 1/2" wider tire? The contact patch hasn't actually changed. You've increased tire width by 1/2" but the weight of the car is now spread over more surface area, so you've decreased the contact patch's length while increasing it's width = no change in surface area (unless you've gone with lower tire pressures). You're also using lower performance tires and you've said you didn't do this for any performance gains. And since the rolling diameter hasn't changed, you haven't actually filled out the wheel well any more. You've just increased the size of the wheel inside the tire. So the wheel gap is the same unless you lower the car.

So the only real reason to do this is to get the look of a bigger wheel inside the circumference of the same rolling diameter tire? But you're still left with the same wheel gap.

I'm not ****ting on your decision here. Just trying to understand what the net effect/benefit is. Especially since these wheels are about $3K each = $12,000 for a set.

I guess you've also pushed the face of the wheel out a little bit as well without having to use a spacer, giving the look of a wider wheel base.
You nailed it, I gained nothing but a bigger rear wheel and more flush offset . As I mentioned the stock wheels with Cup 2s will be used for the track. The Pilot 4s are overall a better daily street tire. So, the question is why did I do it? Because Im a designer, and i think it's looks cool strictly was done for aesthetics, same reason Porsche on the 992 did 21s rear and 20s front stock.
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Old 12-22-2018, 06:34 PM
  #38  
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Originally Posted by dieselino View Post
You nailed it, I gained nothing but a bigger rear wheel and more flush offset . As I mentioned the stock wheels with Cup 2s will be used for the track. The Pilot 4s are overall a better daily street tire. So, the question is why did I do it? Because Im a designer, and i think it's looks cool strictly was done for aesthetics, same reason Porsche on the 992 did 21s rear and 20s front stock.
and you nailed it with what you wanted to accomplish.....enjoy!
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Old 12-22-2018, 06:42 PM
  #39  
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Originally Posted by dieselino View Post
You nailed it, I gained nothing but a bigger rear wheel and more flush offset . As I mentioned the stock wheels with Cup 2s will be used for the track. The Pilot 4s are overall a better daily street tire. So, the question is why did I do it? Because Im a designer, and i think it's looks cool strictly was done for aesthetics, same reason Porsche on the 992 did 21s rear and 20s front stock.

Really, how do u know Porsche went 21 & 20 on the 992 for aesthetics?

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Old 12-22-2018, 06:44 PM
  #40  
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What provides more grip, a narrower(305) gripper tire or a wider(325) less grippier tire?? That's what I would want to know about this setup since tire choices are limited.
edit: just seen the intentions of OP's decision on this setup.
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Old 12-22-2018, 11:47 PM
  #41  
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Originally Posted by KINGSRULE View Post
Really, how do u know Porsche went 21 & 20 on the 992 for aesthetics?
Because I design cars for a living
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Old 12-22-2018, 11:48 PM
  #42  
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Originally Posted by mdrums View Post


and you nailed it with what you wanted to accomplish.....enjoy!
Haha thank you! Tough crowd
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Old 12-23-2018, 12:00 AM
  #43  
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Originally Posted by dieselino View Post
Haha thank you! Tough crowd
Good grief.... tough crowd.... LOL. Your car looks outstanding!

Wanted to do the same same to my GT3. Sold it and bought a GT3RS instead.

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Old 12-23-2018, 07:51 AM
  #44  
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Looks fantastic!
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Old 12-23-2018, 07:52 AM
  #45  
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Originally Posted by Apex Ace View Post


Good grief.... tough crowd.... LOL. Your car looks outstanding!

Wanted to do the same same to my GT3. Sold it and bought a GT3RS instead.

You did the opposite. lol.
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