HPDE experiments, results and observations

[rhyary]

I would like to get the understeer/oversteer function to work in AiM.

First I need to measure the E92 M3 wheel base.
From where to where do I measure?

Then I need help with what I am looking at

ACCGRAV*(((Steer*DEG2RAD)/(Lateralacc*ACCGRAV))-(WHEELBASE/((Speed#1*KMH2MS)^2)))

Understeer/Oversteer calculation
using the relationship between
steering angle and lateral
acceleration, and wheelbase and
speed

[rhyary]

never mind, I found if.
109 inches
2.76 Meter

[rhyary]

Here is the formula I am able to compile successfully:


ACCGRAV*(((STEER_ANGLE*DEG2RAD)/(LateralAcc*ACCGRAV))-(WHEELBASE/((GPS_Speed*MPH2FTS)^2)))

[rhyary]

Roger Caddell from AiM responded to my email and says he will run an AiM seminar on the formula. Yeh!

Watch this coming Tue for a session on 5 formulas. He is adding the AiM_Kuz to the session

[DRLane]

Originally Posted by rhyary

Roger Caddell from AiM responded to my email and says he will run an AiM seminar on the formula. Yeh!

Watch this coming Tue for a session on 5 formulas. He is adding the AiM_Kuz to the session

Very cool, thanks for sharing. I'm curious to try this out.

[dparm]

I thought I had posted the formula in this forum earlier this year. Did it not work for you?

[rhyary]

Stats
Date: Aug 31 2020
Organization: AZP
Track: NYST
Weather: Dry

Track Time: 5 x 15min, 1 x 40min

Tires Front: GY Async 3 2017
285/30/19 day 1

Tires Rear: V720 2017
275/35/19 day 3

Time: 1:38.87

Comments:
Main changes to the car were SPL front lower control arm and fixing rear alignment.
Added 10mm spacer to the rear because that particular rear wheel is 35 offset.

With 35 offset, 295 was rubbing on the inside. So I tried 275/35 which worked great, But I want to establish a tire baseline for 2021 and all three sets will be on 295/30/19.

So I replaced my studs with 90mm and run a 10mm spacer. Since currently that wheel has 275/35, I ran it with a 10mm anyway to check fitment, vibration etc. All worked out fine

Front:
I wanted try the GY 285/30 ($143 2017) but at the same time continue to use the V720 I had on the rear
This led to a 285 front, 275 rear combination.

I already done two trackdays on the V720 and with 35psi hot it had no oversteering issues. I was also on my home track.

The GY Async 3 was not gripping. It was soft and understeery and not happening. It should be good for Palmer and LRP I think, but not for NYST.

I gave it two sessions and replaced it with my other front set 265/35/19 RE-050A

Here is the session with the GY

[rhyary]

Stats
Date: Aug 31 2020
Organization: AZP
Track: NYST
Weather: Dry

Track Time: 5 x 15min, 1 x 40min

Tires Front: RE-050A 2019
265/35/19 day 3+

Tires Rear: V720 2017
275/35/19 day 3

Time: 1:38.1

Comments:
Many laps into 1:38s
I am surprised at the RE050. It is max perf 140 tire that is not rated very high. I got 4 of them for $113 at tire rack. So it was worth a try.

These tires were used for SCDA LRP car clinic control (CCC) and double duty on the big track, Then I took them to Palmer and ran them whole day in two groups

So I had low expectations mounting mid day at nyst with 275/35 rears as described above.

Yet, second lap I was on 1:38.1 and many 1:38 laps to follow. At the end of the day they were not on the cords, but they will be replaced anyway.

video

[rhyary]

Last video from the 8/31/20 day at nyst is me following a racer with a gutted 2400Lbs E36 M3. To equalize the power I use 5th gear a lot and I am not trying to pass him. It was fun to watch what a race driver do on NYST.

The pace was moderate at 1:41-1:42 so at that pace many lines are good at NYST.

After the session we had a conversation. He does 57sec at LRP and race Prototype at LRP with time of 47sec.

I hope to learn more from him in the future

video

[rhyary]

So I am constantly looking at tire rack 285/30/19 for bargains.

Today I saw the 2017 RE-050A for $190. The current one is $334

I have so far good experience with the 265/35/19 both in wear and performance.

I could not resist and ordered 2 for the front.

Knowing that the Kumho PS91 285/30/19 everyday price is $189 and also that I did the best time on any max performance tires (1:37.02) it requires deliberation.

At the end of the day, my curiosity got the best of me and I am intrigued.

A first day PS91 285/30/19 was good for 1:37.02
A third day 265/35/19 RE-050A was good for 1:38.1

What would a first day RE-050A 285/30 can do?

I can't wait to find out

[dparm]

RE050A is a very old tire design (15+ years) and has been surpassed by several generations of tires. I'm surprised they still make it.

I guess if you just want something cheap to use, go for it, but you won't be setting any fast laps.

[rhyary]

Originally Posted by dparm

RE050A is a very old tire design (15+ years) and has been surpassed by several generations of tires. I'm surprised they still make it.

I guess if you just want something cheap to use, go for it, but you won't be setting any fast laps.

For $190 it meets my budget goal.
I find that I can go pretty fast on $200 tires.
I can definitely learn to be a better driver while spending $800 on a set of tires.

Once I experienced a new set of Hoosier R7 for over $1600 per set, I lost the desire to spend money on Cup2, Corsa, R888R, ADO8R for $1200-1400.

The rear 295/30/19 is a different calculation because it last longer. So the RR @ $255/tire is not bad. Still I am not convinced yet that a $202 PS91 is slower than the RR.

I also did not find that linking the front and rear tire purchasing decision has value to me, unless I decide to compete and needs to win by 2/10th.

Perhaps the RE-050A is a 15 years old tire, but so is the BMW M3 or the Porsche 911. I don't think these cars stayed the same, and probably neither the rubber compounds of the RE-050A. The 140 tread has narrow rain grooves, like the PS91, which allows it to have lots of rubber on the road.

With the 265/35/19 RE-050A, on the third day, I got multiple times into 1:38s. This is fast time on NYST. It bags the question what a 285/30 can do.

[Bartledoo]

Interesting speculation that the RE050A compound would be improving over the years...

What are your spring rates, and is the car understeering a ton?

Also, is your throttle in power mode? It looks like you're always pretty late on throttle, but with big stabs.

[rhyary]

Originally Posted by Bartledoo

Interesting speculation that the RE050A compound would be improving over the years...

What are your spring rates, and is the car understeering a ton?

Also, is your throttle in power mode? It looks like you're always pretty late on throttle, but with big stabs.

Not in power mode
750 front, 1000 rear spring

The car understeers in slow turns, mid corner to exit. I have to wait with the throttle. At NYST it is killing my lap time

@dparm describe the problem I have pretty accurately few days ago, but he was talking about his Corvette. Typically the Corvettes at NYST with their cheating 315 size on the front are pulling away from me mid corner to exit.

In my last video I posted chasing E36 M3 you can see how he pulls away in some corners. It is mostly because I can not add more throttle without getting more understeer.

The race driver I was following, later he followed me, wanted me to go slower in the corner.

At LRP, fast corners, I don't have understeering problem. I have a driver "i am scared" problem. I am working on it.

[rhyary]

An interesting observation.

I just realized that I can actually run true square with two sizes. 265/35/19 and 285/30/19.

Even if I don't want to run square, it means that I can squeeze another track day from the fronts, by moving them to the rear, once they are no longer fast up front. If I do that, the question would be what to out on the front.

This is not for a wet day, but for a dry day, with plenty of traction it can be interesting.

It is worth doing on NYST day since I have so much data from that track. And because any good time there is about front grip, it almost doesn't matter that much what I have in the rear.

I just got rid of both 285/30/19 PS91 and 265/35/19 RE050A both could have been fine being on the rear and I could have tested lap times with these. I was just not thinking....

[Bartledoo]

Hard to tell from video, but it just seems like the car is never rotating.

[dparm]

It is possible that Bridgestone has updated the compound in the RE050, but none of the marketing material indicates that this has happened nor that internal construction has changed. Tire companies love telling you how improved the tires are -- and relabeling them -- yet there's no RE050B/C/D/etc.

If you can't get the car to rotate, or are having lots of understeer under power, you need to adjust your technique to compensate...assuming you cannot change the car setup.

Some of my mid-corner understeer was actually being caused by turning in a bit too early and then trying to add more steering later to compensate. I do need a tad more front aero fr high speed grip at the front axle, but that's a minor change.

[rhyary]

Exciting day today at LRP.
Since I can only take with me six wheels all together, even just getting there is an adventure.

First, I have 4 very long sessions (40min) so I have to think about tire longevity. Second, I have rear Proxes RR that I want to use up until they are done.

I have "new" GY 285/30 (two sessions)
for the front and and sticker 265/35 MPSCup2.

So driving to LRP I mounted the 265/35 Cup2 on the rear (stock size) and fronts have the GY 285/30.

It is a dry day today, so not worries about wet traction getting to the track.

When I get there, I am going to mount the RR on the rear and start the day with 295 RR on the rear and 285 GY Async 3 on the front.

I didn't have a good experience with the GY at NYST despite the 285 size. The GY have huge circumferential grooves that puts very little rubber on the road for a 285 tire.

As a data point, the GY 285 has 221mm rubber on the road compare to a PS91's 250mm. Not counting lateral grooves.

As another reference the 265/35 RE-050A has 231mm and the 265 Cup2 has 236mm.

Of course during the rain/wet day this may change the equation, but I am only collecting data on dry days

Since I have the GY, might as well use it and see if it can do better at LRP (fast track with no tight corners) vs NYST.

At some point, I will switch the fronts to the 265 Cup2 and see if I can tell a difference.

If the RR are done before the end of the day, I will run the Cup2 on the rear. While running a wider tire on the front is not conventional, I believe that the Cup2 has more traction than the GY ( more actual rubber on the road, and better rubber compound) despite the sizes. In that case having more traction in the rear will prevent out of control oversteer.

It is surly be an interesting day....

[DRLane]

Originally Posted by rhyary

Exciting day today at LRP.
Since I can only take with me six wheels all together, even just getting there is an adventure.

First, I have 4 very long sessions (40min) so I have to think about tire longevity. Second, I have rear Proxes RR that I want to use up until they are done.

I have "new" GY 285/30 (two sessions)
for the front and and sticker 265/35 MPSCup2.

So driving to LRP I mounted the 265/35 Cup2 on the rear (stock size) and fronts have the GY 285/30.

It is a dry day today, so not worries about wet traction getting to the track.

When I get there, I am going to mount the RR on the rear and start the day with 295 RR on the rear and 285 GY Async 3 on the front.

I didn't have a good experience with the GY at NYST despite the 285 size. The GY have huge circumferential grooves that puts very little rubber on the road for a 285 tire.

As a data point, the GY 285 has 221mm rubber on the road compare to a PS91's 250mm. Not counting lateral grooves.

As another reference the 265/35 RE-050A has 231mm and the 265 Cup2 has 236mm.

Of course during the rain/wet day this may change the equation, but I am only collecting data on dry days

Since I have the GY, might as well use it and see if it can do better at LRP (fast track with no tight corners) vs NYST.

At some point, I will switch the fronts to the 265 Cup2 and see if I can tell a difference.

If the RR are done before the end of the day, I will run the Cup2 on the rear. While running a wider tire on the front is not conventional, I believe that the Cup2 has more traction than the GY ( more actual rubber on the road, and better rubber compound) despite the sizes. In that case having more traction in the rear will prevent out of control oversteer.

It is surly be an interesting day....

While I acknowledge the effort, I'm getting more and more confused by your summaries. You take such a serious approach to sharing your lap time results, but with multiple variables changing at once it's an anecdotal "how did I feel today" vs anything shareable.

I recognize you want maximum track time for dollars invested. I'm not going to go back and count all the different tires tests on the thread, but with the mounting, balancing, shipping, taxes, and tire costs themselves, why aren't you just buying a highly durable track tire and running it?

Lots of WRL teams do long endurance racing on the Hankook RS4 (easily 8 hours driving 7/10ths) on the original tires. I Would think those would last you a while and enable you to track/test variables with your driving vs equipment?

[dparm]

Originally Posted by DRLane

Lots of WRL teams do long endurance racing on the Hankook RS4 (easily 8 hours driving 7/10ths) on the original tires. I Would think those would last you a while and enable you to track/test variables with your driving vs equipment?

They use the RS4 due to contingency/sponsorship, much like a lot of us NASA TT/ST guy use Toyos. Your point is still valid though: pick a reasonably-priced tire, learn how to maximize the performance from it, and go drive.

[DRLane]

Originally Posted by dparm

They use the RS4 due to contingency/sponsorship, much like a lot of us NASA TT/ST guy use Toyos. Your point is still valid though.

Yeah, was just an example of a long lasting tire vs RR and all the other aforementioned tires.

[dparm]

Any tire can be made to last if you adjust your driving accordingly. The RS4 is certainly well-known for its slow wear under normal use, but if you drive like an asshole you can certainly run those down really fast.

I corded a set of R888Rs in two days because I was overdriving the car and not managing the understeer on the front axle. Bought another set, added sway bars, and changed my driving slightly and now they're only half-worn after 4 days.