wider wheels but same tire width . why?

wimbrow

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hey guys, why on the non HP are the wheels wider 9.5/10 but with same tires ?





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Good question. I was wondering the same. Regular GT with the performance pack have, as you said, narrower wheels but the same size tires (255 and 275). Following - perhaps someone will have some insight.
 

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GT PP1 wheels are 9 front 9.5 rear.

In a general sense, using a wider wheel with the same width tire creates preload on the sidewall and increases steering responsiveness and feel.
 

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Good question. I was wondering the same. Regular GT with the performance pack have, as you said, narrower wheels but the same size tires (255 and 275). Following - perhaps someone will have some insight.
Perhaps this Article from the Mustang Test Driver will give you an inside:

https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/

Overall having 0.5" wider wheels than tires help with sidewall flex which help with lap times.

Ford is notorious for doing the opposite putting wider tires on smaller wheels. Like with the PP1. And even the GT350/Mach 1 because of the 315 on 11" which again is explained by Billy Johnson in this article:

https://motoiq.com/not-all-michelin-cup-2-tires-are-created-the-same/

The 315's on the back of GT350/Mach 1 Handling Pack Cup2's are different compound than the 305's Cup2's front. So for convenience Ford decided to make the rear 315 so the owners buy the correct rear compound.

Seeing how many people buy both GT350 or Mach 1 Handling pack and then remove the Cup2's I think Ford didn't have to spend so much time selecting tire compounds.
 
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wimbrow

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Perhaps this Article from the Mustang Test Driver will give you an inside:

https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/

Overall having 0.5" wider wheels than tires help with sidewall flex which help with lap times.

Ford is notorious for doing the opposite putting wider tires on smaller wheels. Like with the PP1. And even the GT350/Mach 1 because of the 315 on 11" which again is explained by Billy Johnson in this article:

https://motoiq.com/not-all-michelin-cup-2-tires-are-created-the-same/

The 315's on the back of GT350/Mach 1 Handling Pack Cup2's are different compound than the 305's Cup2's front. So for connivance Ford decided to make the rear 315 so the owners buy the correct rear compound.

Seeing how many people buy both GT350 or Mach 1 Handling pack and then remove the Cup2's I think Ford didn't have to spend so much time selecting tire compounds.
[/QUOTE
wow. a lot of info for my uneducated brain. i'll just stick to letting the ford engineers do their thing and not mess around with changing the tires or wheels. cheers, tom
 

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Seeing how many people buy both GT350 or Mach 1 Handling pack and then remove the Cup2's I think Ford didn't have to spend so much time selecting tire compounds.
Many people chose HP just for the looks or completeness factor and they won't visit track very often. HP really is intended for those who track the car. Unless one goes out only on short trips on sunny days, I wouldn't want Cup 2's. But there's nothing better for the track for sure so it's good Ford engineers gave it serious thought.
 

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I actually avoided the HP, because of the real world cost and lifespan of those Cup 2s.

I thought I would get smart and downgrade to Pilot Super Sport 4S tires, but they are not available in 315 width according to tire rack last I checked.
 

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P4s will be available in 315/30 R19 in a few weeks, it's a new dimension for this year. And there's P4s 325/30 R19 so that's not an issue.

I'm still checking with Ford CZ if I can run legally these wider wheels with P4s but I admit it's mostly for the cool factor :sunglasses:
 

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I actually avoided the HP, because of the real world cost and lifespan of those Cup 2s.

I thought I would get smart and downgrade to Pilot Super Sport 4S tires, but they are not available in 315 width according to tire rack last I checked.
You can only just trow 305 on the back as well. If you read the article will see that Ford actually planned to do that but put 315 just because otherwise people will not buy the 2 different compounds front/rear. I assume the rear's are actually softer compound than the fronts.
 

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Does that mean the load index 98Y vs 102Y difference? Those are the only two versions of 305/30 R19 Cup2s I see in shops. Damn, these are 50% more expensive than P4s.
 
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wimbrow

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P4s will be available in 315/30 R19 in a few weeks, it's a new dimension for this year. And there's P4s 325/30 R19 so that's not an issue.

I'm still checking with Ford CZ if I can run legally these wider wheels with P4s but I admit it's mostly for the cool factor :sunglasses:
what do you mean run legally?
 

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We can only drive with wheels and tyre dimensions that are written in car's technical certificate. While they're OEM wheels, I'm still checking if local Ford distributor will give a confirmation that they can be written to papers. The tyre size is checked on regular technical inspection and there could be insurance issues if tyre differed in case of an accident. I believe it's the same in the whole EU/UK. Aftermarket wheels need ABE/ECE certificate etc. More here. It's just the usual bureocratic regulatory bullshit.
 

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Does that mean the load index 98Y vs 102Y difference? Those are the only two versions of 305/30 R19 Cup2s I see in shops. Damn, these are 50% more expensive than P4s.
As I understand it there is a bespoke Ford version think the marking is MO (I know confusing) So they have two MO tires with different compound (this is how hard or soft the tire is). In order to avoid this confusion they just created 2 sizes.
Here is an example from TireRack:

https://www.tirerack.com/tires/tire...&frontTire=935YR9PSC2XL&rearTire=035YR9PSC2XL

Looks like the load index is 104Y actually.
 

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Very interesting links here. Glad I found this before buying my all season tires and wheels.
 

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Does that mean the load index 98Y vs 102Y difference? Those are the only two versions of 305/30 R19 Cup2s I see in shops. Damn, these are 50% more expensive than P4s.
I was looking for 10-11" wheels locally available with TÜV certificate for Europe. So far I found only HRE (Flow Form) which have 1 option in 285/35 R19 and 305/35 R19 (sadly no PS4s in this size, only old Super Sport) and more options in same sizes but R20 (available PS4s). Price should be similar to imported PP2 wheels. And these sizes also have less than 2% diameter difference to oem 255-275/40.

And funny thing, specifically HRE FF10 looks pretty similar to HP bird's nest wheels imo.
https://www.mustang6g.com/forums/th...s-vibe-motorsports.126685/page-8#post-3196752


The sidewall difference between 305-315/30 R19 and 305/30 R20 is negligable, just a few milimeters (94 vs 91 mm) which is quite a bit different to 109 mm of 275/40 R19. So they're lower profile than oem but when they're this similar to HP/PP2 sizes, the ride should still be pretty comfortable with 20" wheels. Any thoughs?

(guess these thoughts appear very often, I like some answers about 20" here a lot)
 
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