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245 R-S4s on 10" wide wheels...


Alex3000
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So, I just pulled the trigger on some 15"x10" wheels and 245 wide r-s4's (back ordered, as we all know)

 

Anyway, can I just confirm 245s on 10" wheels won't be super stance-nation? The tirerack specs for the 245s puts the wheel width limit at 9.5".

 

I have read several accounts of people running this setup so I assume it's fine, but part of me is a bit apprehensive still.

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1 hour ago, Alex3000 said:

So, I just pulled the trigger on some 15"x10" wheels and 245 wide r-s4's (back ordered, as we all know)

 

Anyway, can I just confirm 245s on 10" wheels won't be super stance-nation? The tirerack specs for the 245s puts the wheel width limit at 9.5".

 

I have read several accounts of people running this setup so I assume it's fine, but part of me is a bit apprehensive still.

 

image.jpg

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21 minutes ago, KoneKillah said:

PB seems to have trouble getting heat into 245s. Though there car is really light.

 

Hmm, last time I weighed my car is was 2,200# and will be a little lighter in it's new trim. I'm sure playing with pressures can get it to proper temp.

 

Now I just have to pray the tires actually arrive.  Tirerack says 3/31 and I am planning on running NASA track day at Summit Point 4/18 for a first shake down.

 

 

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Yep.  When I was talking about the wheel bearing caps and you turned around I was like oh....   he probably knows what he's talking about....  haha.

 

I appreciate the knowledge and help you have given Tyler over the years.  Much respect.  

 

I should have introduced myself....  next race.

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On 2/14/2020 at 9:09 PM, Indysupra said:

Tyler did you do any back to back on your old wheels to the 10” wheels and 245’s. We did a short teat at  ncm two years ago. We were faster but I feel it was never a real test of before and after due to some condition that were out of our control. 

 

I did not but ever since we have switched to the wider wheels, we have been faster on the track. 

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6 hours ago, EngEtan said:

Why do you guys run such a wide wheel?

There have been a few tire tests that have been backed up by various WRL and champcar teams that show a 205 works best on an 8 inch wheel, 225 on a 9 and 245 on a 10.

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10 hours ago, EngEtan said:

Why do you guys run such a wide wheel?

 

It's all about corning stiffness, which is the slope of the linear portion of the lateral force vs slip angle response of the tire.

Stretching the tire over a wider wheel (up to a point) will improve the cornering stiffness of the tire.

It may also increase the peak grip of the tire, but it will most noticeably improve the transient response.

This is why the driver may comment on better steering response and turn-in characteristics with the same tire on a wider wheel.

 

Image result for lateral force tire plot

 

Here is some real world tire data from my college years comparing the cornering stiffness of two tire compounds on two different wheel widths.

 

image.png.edd76988a9b5710bb58c6506c748acb7.png

 

 

Edited by Scribe
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3 minutes ago, Scribe said:

 

It's all about corning stiffness, which is the slope of the linear portion of the lateral force vs slip angle response of the tire.

Stretching the tire over a wider wheel (up to a point) will improve the cornering stiffness of the tire.

It may also increase the peak grip of the tire, but it will most noticeably improve the transient response.

This why the driver may comment on better steering response and turn-in characteristics with the same tire on a wider wheel.

 

Image result for lateral force tire plot

 

Here is some real world tire data from my college years comparing the cornering stiffness of two tire compounds on two different wheel widths.

 

image.png.edd76988a9b5710bb58c6506c748acb7.png

 

 

 

 

 

NIce! LC0 or R25B?

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23 minutes ago, KoneKillah said:

NIce! LC0 or R25B?

 

Classified 😉

 

Interestingly, compound 1's peak lateral coefficient of friction increased on the +1" wheel, but compound 2's peak lateral coefficient of friction decreased on the +1" wheel.

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8 hours ago, wvumtnbkr said:

There have been a few tire tests that have been backed up by various WRL and champcar teams that show a 205 works best on an 8 inch wheel, 225 on a 9 and 245 on a 10.

 

4 hours ago, Scribe said:

 

It's all about corning stiffness, which is the slope of the linear portion of the lateral force vs slip angle response of the tire.

Stretching the tire over a wider wheel (up to a point) will improve the cornering stiffness of the tire.

It may also increase the peak grip of the tire, but it will most noticeably improve the transient response.

This is why the driver may comment on better steering response and turn-in characteristics with the same tire on a wider wheel.

 

Image result for lateral force tire plot

 

Here is some real world tire data from my college years comparing the cornering stiffness of two tire compounds on two different wheel widths.

 

image.png.edd76988a9b5710bb58c6506c748acb7.png

 

 

 

Interesting. I wasn't aware that some sidewall stretch would make any significant differnence... although, your second graph is missing cornering stiffness units, but I suspect that wasn't by mistake haha

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On average Compound 1 saw a 13% increase in cornering stiffness and Compound 2 saw a 11% increase in cornering stiffness from the wider wheel.

The graph is at 4 different pressures (separated at the dotted lines). 

The optimal pressure appeared to be between the first and second pressure depending on how much downforce/how heavy the vehicle is.

At the two lowest pressures, Compound 1 and 2 both saw a 19% increase in cornering stiffness from the wider wheel.

 

One thing to note is that these are slick tires and may behave a bit differently than the 200TW tires we use.

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