GTS Wing's Aerodynamics

[tsk94]

Rear toe 100% contributes to the rear end stability under braking, thus running 0 toe is less stable under hard braking then a car with toe-in. End of discussion.

[rhyary]

Originally Posted by tsk94

Rear toe 100% contributes to the rear end stability under braking, thus running 0 toe is less stable under hard braking then a car with toe-in. End of discussion.

This is not the issue.
The issue is that 0 toe helps on the turns.

So if the car steers better thru the turn and is faster on the turn, and it does not chew the inside of the tires and the rear moves a bit on the brakes then so what?

In my opinion, adding a more effective wing and reducing rebound is a faster and better setup than changing the toe. But the lap time will tell soon enough.

[Bartledoo]

Originally Posted by rhyary

Not at all. I am simply sharing my thoughts and what I am doing. I enjoy comments, suggestions and advise. But, I am definitely not looking for people to agree with me.

I do try to explain why I do certain things. This can misinterpreted as defensiveness. Which is understandable.

While I am not shy of trying things, I report back what my findings are. In this instance, if the wing will make slower, I will report on that. It it makes me faster, I will report on that as well.

Originally Posted by rhyary

It is not. I have been on 0 toe for awhile and it is more due to my experimenting with the JRZ rebounds.

I dialed the rebound back from 15-16 to 8 and at least on road tests it worked as expected.

And since someone is going to comment, I went up the rebound tree to see the effect on roll.

This is the reason you get snide remarks, after we try to help you for a while. A few pages back the same GT-250 wing and a real splitter couldn't possibly have made my car faster according to you. Now, you are throwing the same wing on without a splitter and expecting results.

Then you're suggesting (no stating adamantly) that rear toe doesn't affect stability of the rear end during braking, and not finding it odd that you are the only person actively pursuing zero toe in the rear (i've run with it for a bit and it was fine, but not purposefully). You have brake psi values though so your data proves that it doesn't?

Then you list random numbers with no idea how to actually interpret them, and discover very basic stuff extremely late...that you could've focused on waaaay before looking at shit like potentiometer data... You're approach is just way too f'd my man.

[rhyary]

Originally Posted by Bartledoo

This is the reason you get snide remarks, after we try to help you for a while. A few pages back the same GT-250 wing and a real splitter couldn't possibly have made my car faster according to you. Now, you are throwing the same wing on without a splitter and expecting results.

Then you're suggesting (no stating adamantly) that rear toe doesn't affect stability of the rear end during braking, and not finding it odd that you are the only person actively pursuing zero toe in the rear (i've run with it for a bit and it was fine, but not purposefully). You have brake psi values though so your data proves that it doesn't?

Then you list random numbers with no idea how to actually interpret them, and discover very basic stuff extremely late, that you could've focused on waaaay before looking at shit like potentiometer data...

I can see your point.
I'll dial back my participation.
I acknowledge consuming too much bandwidth.

The comment about your video was my honest mistake. I did not know you driving at the speeds you reported and made an inappropriate comment. I apology for that comment.

Putting an appropriate splitter is not in the plan at the moment. Not to say I will never do it or it should not ne there. I first want to try using the wing without it.

[Bartledoo]

As a constructive comment, I think you should absolutely not get the wing (for the time being). I think it's pretty clear that you are afraid of oversteer at the moment (and I don't mean that in a negative way), but making the car handle worse to make you more comfortable isn't going to aid your learning in the long run. People do this a lot and it is a well known detriment to progression.

[tsk94]

Originally Posted by rhyary

This is not the issue.
The issue is that 0 toe helps on the turns.

So if the car steers better thru the turn and is faster on the turn, and it does not chew the inside of the tires and the rear moves a bit on the brakes then so what?

In my opinion, adding a more effective wing and reducing rebound is a faster and better setup than changing the toe. But the lap time will tell soon enough.

DRLane said, 'That wiggle or movement in the rear can also be attributable to your rear toe alignment.'. Twice you replied to him saying it is not. My point was IT IS. DRLane was correct but twice you tell him it's not related to your problem.

The 'so what' is you're complaining about rear end instability, stating it as the primary reason to get a roof height wing, yet you have a simple solution to that in rear toe, but then you state '..the rear moves a bit on the brakes then so what.' I can't comprehend the logic.

Again, I think the rear wing is a good choice. But your logic seems like it's a bandaid for otherwise poor setup concepts/choices.

[rhyary]

Originally Posted by tsk94

DRLane said, 'That wiggle or movement in the rear can also be attributable to your rear toe alignment.'. Twice you replied to him saying it is not. My point was IT IS. DRLane was correct but twice you tell him it's not related to your problem.

The 'so what' is you're complaining about rear end instability, stating it as the primary reason to get a roof height wing, yet you have a simple solution to that in rear toe, but then you state '..the rear moves a bit on the brakes then so what.' I can't comprehend the logic.

Again, I think the rear wing is a good choice. But your logic seems like it's a bandaid for otherwise poor setup concepts/choices.

Got it.
Thank you for your advice.

[rhyary]

Originally Posted by Bartledoo

As a constructive comment, I think you should absolutely not get the wing (for the time being). I think it's pretty clear that you are afraid of oversteer at the moment (and I don't mean that in a negative way), but making the car handle worse to make you more comfortable isn't going to aid your learning in the long run. People do this a lot and it is a well known detriment to progression.

Thank you Bartledoo .
We will know shortly if the wing is a bad idea.

[sc_tr0jan_m3]

Could it be... just maybe... that you have analysis paralysis?

We already know that the GTS wing is not very efficient. Go buy a BW or AJ wing, slap it on, go try to drive without a front splitter, then go install a front splitter to finally see the light...

[DRLane]

@rhyary

I don't think you should dial back your participation. You have demonstrated tremendous passion for tracking a really nicely built car. I hope to have as many hours on track as you! Clearly lots of time has been spent on and off the track and that passion is what makes the activity so great.

I'm just confused as all of the setup work for this chassis has been done, period. Apart from building a one off race car, the chassis upholds all the suspension tuning principles verbatim. Why not follow the systematic approach that would get you the desired outcome? Reliably faster laps within control?

I acknowledge it's fun to do your own experimenting, but having 10 variables in play at any point and then sharing "faster or not lap times" and then arguing about the validity of your findings is at odds with the rigor for which you ask about set up ideas.

I can't handle the continuation of "alternative facts". Its 2021

[kyippee]

It's ok to consider more viewpoints / information and change one's mind.

[Epoustouflant]

Originally Posted by kyippee

It's ok to consider more viewpoints / information and change one's mind.

Please, yes 🙏

[gmx]

What's wrong with wiggle ? :P
Moar rotation please! I'm about to dial back my rear toe closer to 0. Not 0, not yet at least.

My first remark is really down to the driver. If the driver requires more response and can handle it. I don't see an issue. Usually there is a setup for you, your mate, whatever. Then there is the fastest setup to adapt to.

How are potentiometers judging anything? Did you graph damper velocity over the lap or several laps to make that judgement?

[rhyary]

Originally Posted by gmx

What's wrong with wiggle ? :P
Moar rotation please! I'm about to dial back my rear toe closer to 0. Not 0, not yet at least.

My first remark is really down to the driver. If the driver requires more response and can handle it. I don't see an issue. Usually there is a setup for you, your mate, whatever. Then there is the fastest setup to adapt to.

How are potentiometers judging anything? Did you graph damper velocity over the lap or several laps to make that judgement?

Nothing wrong with a wiggle.
The ABS on the rear stays longer than I prefer.
0 toe worked well for me, so I am not trying to solve that problem.

We can finish every post with "it depends on the driver". It would be true even for the experts on this forum.

Since I am working with an experienced suspension guy, he advised less rebound and more HS dumping. So this is what I am pursuing.

My pots frequency was set on 50Hz because setting them higher messed up the GS display (froze the reading). They should be on 200Hz. So I expect to have a better data this year than last year.

Nevertheless, from data the I do have the histogram shows not enough rebound.

I hope to have a meaningful reading to show downforce. But pots are really tough to calibrate. The frequency (mm/sec) works well. But the distance (mm) changes for some reason and I have to reset (calibrate) it to 0 before I go to the session and at times it is too much trouble to do multiple times a day.

But as you know, it depends on the driver.

[gmx]

Rebound adjustment purely based on the histogram or your feedback too?
Be careful using the histogram to achieve a perfect shape. It shouldn't define the setup, but only help find answers.

[rhyary]

Originally Posted by gmx

Rebound adjustment purely based on the histogram or your feedback too?
Be careful using the histogram to achieve a perfect shape. It shouldn't define the setup, but only help find answers.

Correct, not purely by histogram. Long history of studying effect of the rebound, compounded by rear spring changes (900-1100) and the need to rebuild JRZ mid 2020 season.

Should be good to go for 2021. Don't want to derail an aerodynamic thread.

[rhyary]

I had a conversation with APR about front splitter. They can attach their flat composite splitter underneath my RKP GTS style splitter.

According to APR, if I stick their splitter 2.5" infront of the GTS it will produce enough downforce to balance the rear wing. About 100Lbs.

This is all approximations. Aero is such a black art that it is very difficult, if not impassible to know exactly what will happen on a particular car at a particular track, at a particular speed.

Since not all tracks are equal, for example LRP and NYST are very different requirements, it is not clear what, on the average, will benefit all tracks.

While I do have professional help, it is not including changing setup at track side. So any setup that needs changes need to have a simple way to do it, for example changing AOA on a rear wing is doable.

I have watched many aero lectures on YouTube and read what ever I could, and I am ready to give up. Which I rarely do when I don't understand something.

I am not a guy that set it and forget it. Just not what I enjoy. I enjoy experimenting and learn to see what happens. Many here don't share my passion, but honestly this is ok. This is why there are many flavors of ice-cream.

While many advised to balance the wing with a splitter, and one opined that GTS style is not a splitter, I think I am better off trying the wing without a splitter, than adding it on later.

I view a splitter as complication for a car that is driven to the park to go running and to the track to go in circles. Even the GTS getting scraped here and there.

There is also the risk that the GTS is not mounted strong enough, although that is a remote risk and Autocouture did an excellent job on the mounting. I can stand on the GTS lip.

Now it is the game of wait and see. Waiting for the Hard mounts and the wing to be delivered to ACM and everything needs to be ready by March 20th

I am going to paint everything Jerez so nobody can tell I mounted 71" wing on the rear. it will be invisible.

[rhyary]

This post got me thinking:

https://www.bimmerpost.com/forums/sh...php?p=27282095

By putting effective wing to replace the GTS wing, one of the concerned expressed here on this thread is understeer. I suppose the logic is that the adding downforce would create more traction to the rear and prevent the rear of the car to "step out" and help the rotation.

But I think this is not that simple. Let's assume that if I do have understeer and it is not due to driver error.

At the extreme example that the wing will lift my front so that the front tires will be in the air. That will prevent the car from steering effectively and it will go straight. So yes, understeer.

But there can be another explanation. Let's assume that the understeering is due to the front weight biased the super charger introduced in addition to taking weight from the rear.

Let's assume that the GTS wing was only designed to balance the car at 120mph and faster.

Now, let's assume that the APR at 0 AOA just make the front a bit lighter. If you imagine the rear wheels axle as a pivot point, it would be possible to assume that the car will have easier time to rotate over the rear axle and in fact, will understeer less.

The front tires will have less weight on them, which will make them more effective steering per slip angle. Less weight as in making them less overwhelmed at the extreme.

I wish someone can explain this better. I would love to know if this anecdotal thinking is a remote possibility.

After all if a Porsche rear engine 40/60 does not understeer, why would I?

[b4hand]

Originally Posted by rhyary

After all if a Porsche rear engine 40/60 does not understeer, why would I?

Porsches do understeer, you just have to drive them differently because of that fact. A porsches main advantage is corner exit due to all the weight over the driving tires.

[rhyary]

Originally Posted by b4hand

Porsches do understeer, you just have to drive them differently because of that fact. A porsches main advantage is corner exit due to all the weight over the driving tires.

I don't see a big splitter

[b4hand]

Originally Posted by rhyary

I don't see a big splitter

With no engine in the front, gt3's have pretty good front aero. I don't think its as simple as "big splitter" with 911 gt3 based cars.

[Bartledoo]

So you're suggesting a bigger wing could make the car understeer less?