Track forum general chit chat.

[kyippee]

Originally Posted by gmx

^ At the risk of repeating myself here.
@kpewpew How's the balance with your JRZs? Did you add the aero (lip/wing) later or at the same time?
And what NT01 size & wheel offset do you run on your EC7s?

Balance is great with JRZs. My friend who is a far better driver than me has driven my car many times and gives feedback on setup. (Reference: Podium on his first USTCC entry, HPDE coach, and ran a 1:42.xx at laguna with his stock power FRS/BRZ/86 on Nankang AR-1)

I did the JRZ RS One first at 550/800 spring rates (+helper springs in front and the rear weight jacks), then added the aero bits later. His feedback with the JRZ suspension, both pre and post (small) aero of the GTS rep lip and wing has continued to be that it's very well balanced and at 15-17 clicks on the RS 1-way, it is good but could be just a little bit stiffer. With the wing on, he just noticed it is a bit more understeer prone than before.

NT01 size is 275/35/18 and EC7 is 18x10 ET25 square - pretty standard fitment. I've tested 18x10.5 ET22 all around with 265 width R888R and it fit, no rubbing even with lots of compression. Curious about 285 with now...

[rhyary]

Originally Posted by kpewpew

How many track days or heat cycles are Toyo RR lasting for you? Asking for a friend.. 🤔🤔🤨

i can do with the front RR
14 x 20min session (2 days for sure)
a third day (7 x 20) I may skip a session, not finish, or drive slow and try different things but not going fast

The rear go twice as much (4 days for sure) and 5 or 6 days depends

[rhyary]

Originally Posted by ThunderMoose

I have never driven the RR's so I can't offer a comparison myself. I do remember though when I first drove on Hoosiers I didn't see a lot of improvement over NT01's at the time. However, the first time I use c51's which are equivalentish I saw a 3 second improvement over my previous time without a lot of effort. My fastest lap at my home track was on 5HC C51's but I still primarily drive Hoosiers because of NASA contingency.

Were you able to break 1:00 at LRP? You were awfully close last time.

I did many 1:02 learning new lines the pro driver coach was showing me.

It was 85 degrees. I did 1:01 with the RR on a 64 degree days

[rhyary]

Originally Posted by dparm

I don't know if the 265 would necessarily be faster, but it will last longer and probably be more consistent over the course of the session. One of the biggest reasons to run a larger tire is because it can dissipate heat better (same reasoning as using a larger brake rotor), but it is diminishing returns -- you are now adding rolling resistance, more unsprung weight, etc.

The Aim data do not support this information. But yes, on paper you are correct

The one thing a 235 can do, perhaps, is get more rubber on the road because it is narrower. In a perfectly flat track, a 265 will have more rubber than 235. But there is something about the narrow 235 that make the car turns at an 18 turns tight track like NYST. Perhaps in real life the wider tire can't get all the rubber on the road.

At LRP you can tell the 265 Hoosier is better but not faster counting other factors like ambient temperature.

Also, the data does not support the theory that the 265 dissipate heat better than the 235. The drop off between the cooler morning sessions and the afternoon hot sessions is about 2 seconds on both the 256 and 235

[OG Shark]

Originally Posted by kpewpew

Balance is great with JRZs. My friend who is a far better driver than me has driven my car many times and gives feedback on setup. (Reference: Podium on his first USTCC entry, HPDE coach, and ran a 1:42.xx at laguna with his stock power FRS/BRZ/86 on Nankang AR-1)

I did the JRZ RS One first at 550/800 spring rates (+helper springs in front and the rear weight jacks), then added the aero bits later. His feedback with the JRZ suspension, both pre and post (small) aero of the GTS rep lip and wing has continued to be that it's very well balanced and at 15-17 clicks on the RS 1-way, it is good but could be just a little bit stiffer. With the wing on, he just noticed it is a bit more understeer prone than before.

NT01 size is 275/35/18 and EC7 is 18x10 ET25 square - pretty standard fitment. I've tested 18x10.5 ET22 all around with 265 width R888R and it fit, no rubbing even with lots of compression. Curious about 285 with now...

Have you gone to a 5" spring in the front to get the spring perch up? 295/30/18 R7 & 285/30/18 R1 S can both fit nicely up front on 18x10.5 ET22. Might help if you haven't already done it to get the 285 R88Rs to fit.

[macdude357]

Originally Posted by kpewpew

There's still hope... I think the pump is just dead and maybe the massive windshield splatter I got was the pump just giving up on life.

Any update on the this? Were you able to tell where the fluid came from?

[kyippee]

Originally Posted by OG Shark

Have you gone to a 5" spring in the front to get the spring perch up? 295/30/18 R7 & 285/30/18 R1 S can both fit nicely up front on 18x10.5 ET22. Might help if you haven't already done it to get the 285 R88Rs to fit.

My front springs are already 5" height

Originally Posted by macdude357

Any update on the this? Were you able to tell where the fluid came from?

I did another track day at laguna, there was a bit of spray but not as bad as before... not fully sure on how good the 3D part is at solving the problem. Might try the bimmerworld reservoir.

Originally Posted by rhyary

i can do with the front RR
14 x 20min session (2 days for sure)
a third day (7 x 20) I may skip a session, not finish, or drive slow and try different things but not going fast

The rear go twice as much (4 days for sure) and 5 or 6 days depends

Thanks! Seems like the really don't last long on our heavier cars. My friend gets more than that, I think he's done about 4-5 days on his Toyo RR so far on his ND Miata

[dparm]

Originally Posted by rhyary

The Aim data do not support this information. But yes, on paper you are correct

The one thing a 235 can do, perhaps, is get more rubber on the road because it is narrower. In a perfectly flat track, a 265 will have more rubber than 235. But there is something about the narrow 235 that make the car turns at an 18 turns tight track like NYST. Perhaps in real life the wider tire can't get all the rubber on the road.

At LRP you can tell the 265 Hoosier is better but not faster counting other factors like ambient temperature.

Also, the data does not support the theory that the 265 dissipate heat better than the 235. The drop off between the cooler morning sessions and the afternoon hot sessions is about 2 seconds on both the 256 and 235

Interesting. Do you have actual tire temperature data and real-time pressure data?

[roastbeef]

Nonsense. If you could fit a 315 up front on a proper width wheel, you'd undoubtedly be faster.
The only way to get more rubber contact is to get more rubber. Anything else is a pressure issue.

[Chris_PDX]

Originally Posted by roastbeef

Nonsense. If you could fit a 315 up front on a proper width wheel, you'd undoubtedly be faster.
The only way to get more rubber contact is to get more rubber. Anything else is a pressure issue.

I wish more people grasped this concept. The *only* thing that truly controls how fast you go, stop, or turn corners is the tire contact patch.

Always the first thing we talk about when we're covering vehicle dynamics at coaching days.

[ThunderMoose]

Originally Posted by Chris_PDX

I wish more people grasped this concept. The *only* thing that truly controls how fast you go, stop, or turn corners is the tire contact patch.

Always the first thing we talk about when we're covering vehicle dynamics at coaching days.

one thing I still don't understand is why wider tires are faster.

static contact patch is independent of tire width. That is, at 245 tire will have the same static contact patch as a 315 tire assuming they are at the same pressure.

Example: 3500 car with 30 psig tires will have a total contact patch of 3500/(30) = 117 sq inches or 29 sq inch per corner assuming equal weight distribution.

Edited: I don't think I should've tried to correct to psia

So the difference must be in dynamic contact patch and while I know that wider tires are better I have not yet seen the mathematical explanation of why.

Does anyone have some equations to help explain this? I am honestly curious to fill in this gap in my understanding.

[roastbeef]

It's wider... the width of the contact patch increases? I don't see how it's possible that a 265 and a 315 can have the same static contact patch aside from camber influence.

[tsk94]

Originally Posted by roastbeef

It's wider... the width of the contact patch increases? I don't see how it's possible that a 265 and a 315 can have the same static contact patch aside from camber influence.

Ya. The contact patch should be directly correlated to the width of the tire. As the width of the tire increases so does the width of the contact patch - so wider tires will give a larger contact patch in terms of area.

[ThunderMoose]

Originally Posted by roastbeef

It's wider... the width of the contact patch increases? I don't see how it's possible that a 265 and a 315 can have the same static contact patch aside from camber influence.

Interestingly enough, I found this article below, where they actually find that the patch pressure is different than the tire pressure at different loads due to deflection.

In their experiments, the did confirm that at a 550 lb load the contact patch for the tires tested was equal (67 sq. inches) for two tires of different widths - oddly enough 245 vs 315. In fact, the narrower tire had a LARGER contact patch at loads from 100 lbs to 500 lbs. However, as the loads increased beyond 500 lbs, the contact patch increased for the wider tire but not directly in proportion to width.

As an example, the contact patch at 992 lbs and 28 psi was 81.5 and 88.6 sq. in for the 245 and 315 tires, respectively. Thats an 8.7% increase in contact patch for 28.7% increase in tire width.

They also found that if you lowered the pressure too much the contact patch actually gets smaller!!!

I think this is why it is so important to follow the engineer's recommendations for cold and hot tire pressures. In some cases, lowering the pressures will actually reduce contact patch.

It also shows what our intuition tells us and which the simple formula that I offered up and have seen before is simplistic in that it does not take into account the effects of tire design and sidewall stiffness. That is wider tires do help but probably not as much as you might think and certainly less for lighter cars.

TLDR: Wider tires have a larger contact patch but not directly in proportion to the increased width and offer smaller gains as the car gets lighter and lighter. Also, follow the manufacturers recommended tire pressures.

https://www.enginebasics.com/Chassis...t%20Patch.html

[kyippee]

Yes I think it's more about the shape of contact patch than surface area.

[tsk94]

Originally Posted by ThunderMoose

Interestingly enough, I found this article below, where they actually find that the patch pressure is different than the tire pressure at different loads due to deflection.

In their experiments, the did confirm that at a 550 lb load the contact patch for the tires tested was equal (67 sq. inches) for two tires of different widths - oddly enough 245 vs 315. In fact, the narrower tire had a LARGER contact patch at loads from 100 lbs to 500 lbs. However, as the loads increased beyond 500 lbs, the contact patch increased for the wider tire but not directly in proportion to width.

As an example, the contact patch at 992 lbs and 28 psi was 81.5 and 88.6 sq. in for the 245 and 315 tires, respectively. Thats an 8.7% increase in contact patch for 28.7% increase in tire width.

They also found that if you lowered the pressure too much the contact patch actually gets smaller!!!

I think this is why it is so important to follow the engineer's recommendations for cold and hot tire pressures. In some cases, lowering the pressures will actually reduce contact patch.

It also shows what our intuition tells us and which the simple formula that I offered up and have seen before is simplistic in that it does not take into account the effects of tire design and sidewall stiffness. That is wider tires do help but probably not as much as you might think and certainly less for lighter cars.

TLDR: Wider tires have a larger contact patch but not directly in proportion to the increased width and offer smaller gains as the car gets lighter and lighter. Also, follow the manufacturers recommended tire pressures.

https://www.enginebasics.com/Chassis...t%20Patch.html

Interesting, I actually found this article as well shortly after reading your first post.

In your opinion then, what do you believe we should be doing with tire sizing for optimal performance?

[dparm]

Originally Posted by Chris_PDX

I wish more people grasped this concept. The *only* thing that truly controls how fast you go, stop, or turn corners is the tire contact patch.

Always the first thing we talk about when we're covering vehicle dynamics at coaching days.

Novice trick question that instructors ask:

"What stops the car?"
"The brakes"
"Wrong, the tires"


Also, highly recommend this book. It's pretty technical but he breaks things down. You'll need high school math to follow along:
https://smile.amazon.com/Fast-Car-Ph...gateway&sr=8-1

[dparm]

Originally Posted by ThunderMoose

one thing I still don't understand is why wider tires are faster.

static contact patch is independent of tire width. That is, at 245 tire will have the same static contact patch as a 315 tire assuming they are at the same pressure.

Example: 3500 car with 30 psig tires will have a total contact patch of 3500/(30) = 117 sq inches or 29 sq inch per corner assuming equal weight distribution.

Edited: I don't think I should've tried to correct to psia

So the difference must be in dynamic contact patch and while I know that wider tires are better I have not yet seen the mathematical explanation of why.

Does anyone have some equations to help explain this? I am honestly curious to fill in this gap in my understanding.

Friction is independent of surface area. But this is different when we talk about SLIDING friction. See the book I referenced above. :-)

[M3 Number 86]

Anyone know any good M dismantlers?

Found some decent choices on eBay but at this point don't have any trust in them. Would like a recommendation.

Need new transmission.

[XKxRome0ox]

total noob question -
am i going to lose control and kill myself on the roval at autoclub speedway because i don't have some sort of rear trunk spoiler?

[roastbeef]

Originally Posted by XKxRome0ox

total noob question -
am i going to lose control and kill myself on the roval at autoclub speedway because i don't have some sort of rear trunk spoiler?

i went to big willow with a naked trunk once and felt a difference. i had the carbon performance spoiler though.

[ThunderMoose]

Originally Posted by tsk94

Interesting, I actually found this article as well shortly after reading your first post.

In your opinion then, what do you believe we should be doing with tire sizing for optimal performance?

Certainly the conventional wisdom is wider is better.

I have 4 sets of 9.5 rims and a 3000 lb car. I have been able to set and hold 6 NASA TT3 track records on 245's Hoosiers (which are really 265). I am not sure I could go to anything wider than a 275 without buying more wheels and adding fender flares. I'd also have to detune or add weight.

I'd say if you have no limitations, go as wide as you can.