Wheel hop - what more can I do?

[Funkjaw]

On the topic of tire pressure - I lowered mine down to ~35psi. Less wheel hop. The computer wants me at 41psi. Sorry baby can't do it ?

Of course I still think it's a bit of a band-aid - I should be able to brake stance this thing into a barricade and catch the tires on fire without wheel hop. I've ran plenty of cars at 60+ PSI on drift courses with no wheel hop. Yeah its sketch and you have no traction and the tires over heat super fast but again, no wheel hop in those instances. ?‍

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[i3igpete]

 

[BMWAF]

On the topic of tire pressure - I lowered mine down to ~35psi. Less wheel hop. The computer wants me at 41psi. Sorry baby can't do it ?

Of course I still think it's a bit of a band-aid - I should be able to brake stance this thing into a barricade and catch the tires on fire without wheel hop. I've ran plenty of cars at 60+ PSI on drift courses with no wheel hop. Yeah its sketch and you have no traction and the tires over heat super fast but again, no wheel hop in those instances. ?‍

WTF. So my sticker recommends 32PSI, my iDrive recommends 34PSI and yours recommends 41?.

Is the car taking into account tyre temperature and or/weight? Surely it's not that clever?

 

[J29DB03]

WTF. So my sticker recommends 32PSI, my iDrive recommends 34PSI and yours recommends 41?.

Is the car taking into account tyre temperature and or/weight? Surely it's not that clever?

Think it might. In the summer I’ve seen the recommended pressure increase 1-2 psi as the tires heat up.

 

[Funkjaw]

Chiropractors watching this video with a hard on.

 

[FLtrackdays]

[/QUOTE]

I don't experience any wheel hop and run 32 PSI. I also have a very different sticker in my car.

Interesting sticker. I’m in the U.S. and it only lists the pressure for the wheels on the car, and only lists 38 PSI, not a range. I’ll try dropping tire pressure when I have some time to cruise back roads.

Better traction, lower gas mileage.

That’s really the key ain’t it (what Thrax said ?). Those high pressures must be an across the ocean thing to keep our gas mileage on the higher side. Is CAFE standards still a thang?

Doesn't surprise me one bit that you have wheel hop/traction issues when running your tires that high.

On track (turny track) I aim for 32-33psi hot and go out with 25-26psi.

True dat on those hot pressures. By habit, I’m used to pulling outside the garage, check the pressures, bleeding down to 32psi & add gas, all day long. And it’s funny you mention 26psi, cuz the next day/morning when I check em before going out, they’re roughly that every time ?. Guess I could switch it up every now & then & start checking cold pressures.

I’m not worried when it’s as hot as Hades out. But when we do get the occasional 40-50 degrees mornings, I tend to go out higher psi to start. Suppose it wouldn’t hurt to just leave em at 26psi?!?

On the topic of tire pressure - I lowered mine down to ~35psi. Less wheel hop. The computer wants me at 41psi. Sorry baby can't do it ?

Of course I still think it's a bit of a band-aid - I should be able to brake stance this thing into a barricade and catch the tires on fire without wheel hop. I've ran plenty of cars at 60+ PSI on drift courses with no wheel hop. Yeah its sketch and you have no traction and the tires over heat super fast but again, no wheel hop in those instances. ?‍

That’s f’ed up!! Of course I ditched my TPMs long ago so don’t know what my car thinks about it…

 

[MisterSkiz]

Here is what mine weighs with a full tank of gas.
3363lbs or ~1525kg - she's a big girl! ?

Well its light compared to an M2 and a Mustang I wonder how much different seats and battery can do

 

[razorlab]

Well its light compared to an M2 and a Mustang I wonder how much different seats and battery can do

Both seats + lightweight battery + removing rear diff weight saved me 103 lbs.

 

[MisterSkiz]

Both seats + lightweight battery + removing rear diff weight saved me 103 lbs.

I wanted to pull that diff weight off as well, but I was assuming it was for NVH and I would get some strange noises or something.

 

[FLtrackdays]

Well its light compared to an M2 and a Mustang I wonder how much different seats and battery can do

My weight with me in it (~190lbs) and before I switched out the OEM battery & seats. Like Bryan said, that battery and seat exchange makes a big difference!

 

[razorlab]

I wanted to pull that diff weight off as well, but I was assuming it was for NVH and I would get some strange noises or something.

I noticed zero difference.

 

[jchadwell]

I noticed zero difference.

Ditto.

 

[Thraxbert]

OEM tire pressure is a major way to cheaply and easily improve gas mileage. This is why we have a bunch of different people, from a bunch of different countries, showing different sticker specs. If the government is telling you to improve the gas mileage of your fleet by 1-2mpg by x year, and you can solve that problem by printing a new sticker, you're gonna print a new sticker.

 

[Andyinater]

Hey Guys,

Just wanted to share some knowledge with respect to power hop. If you can access this paper, it is a pretty good breakdown of the fundamental dynamics at play without getting too wordy:

Stability Analysis of Solid Axle, Torque Arm Suspension Vehicles under Heavy Acceleration and Braking Events (https://doi.org/10.4271/2008-01-1144)


But to summarize:

If you look at a tire longitudinal mu vs slip curve, it starts rising to a peak where a given slip yields optimal traction, afterwards it starts sloping down and you get less traction with every additional unit of slip. This downward sloping part of the curve is effectively "negative damping", that is instead of dissipating energy of a system, it adds to it.


A ride damper is always positively damping, in that the force is always opposed to the velocity, dissipating the system energy. But on this downwards sloping mu portion of the curve, additional slip (+ve velocity), is associated with a decrease of traction, which is a net force in the same direction as velocity, hence negative damping.



So that ingredient is present on every car with a tire. The other ingredient is a reservoir with which this additional energy from negative damping can be stored into, and eventually pushed out of, like a spring.



This can be torsional stiffness of the drivetrain, or bushing stiffness + suspension geometry, or engine/diff mounts - pretty much anything springy that experiences a force when drive torque is applied is liable to be a culprit.


And the general answer is stiffer is better - while the dynamics are still at play, a stiffer system will cause any hop to fizzle out much faster and with much less energy (read: lower forces, stresses, damage). There are also other clever ideas like asymmetric left/right half shaft torsional stiffness, but it is still an application-by-application solution and requires some calculation to get it right.


For any given vehicle, the location to add stiffness for maximum effect can vary. I have no real indication of what it could be on our supras - my 2023 6MT hops like crazy (at ~38 sticker psi) - I don't power through at all and avoid it, but a diff bolt still fatigued out on me. Maybe the previous owner was more daring...



On that alone, maybe I would guess the diff mounts. These will come softer than optimal from a performance standpoint because they are an NVH concern, where generally softer is better (within reason).


Lowering psi is likely a good crutch fix as has been identified - it will give you more traction and make traversing the downward slope of the mu-slip curve a harder place to reach, but as also pointed out, ideally we should be able to light these tires up without having to deal with hop.



Most of this was already identified in the thread, but I thought bringing it all together with a good source reference might be nice. And also, who can resist when work and play start to cross over.



- Andy

 

[Funkjaw]

For any given vehicle, the location to add stiffness for maximum effect can vary. I have no real indication of what it could be on our supras - my 2023 6MT hops like crazy (at ~38 sticker psi) - I don't power through at all and avoid it, but a diff bolt still fatigued out on me. Maybe the previous owner was more daring...
- Andy

This is something I need to check on - make sure myself or the one previous owner didn't hop a bolt into oblivion. It's also interesting that you too have a 23' manual and you are experiencing exactly what I am going through - meanwhile the guys in automatics seem to not have this issue so much. Guess this is what we get for buying the cooler version of the car

On that alone, maybe I would guess the diff mounts. These will come softer than optimal from a performance standpoint because they are an NVH concern, where generally softer is better (within reason).

I have the twisted tuning diff mount brace/lockdown kit... so in theory my diff should be a lot more solid than factory but unfortunately that still doesn't seem to be the case... Or it just means the problem is outside of the diff.

Lowering psi is likely a good crutch fix as has been identified - it will give you more traction and make traversing the downward slope of the mu-slip curve a harder place to reach, but as also pointed out, ideally we should be able to light these tires up without having to deal with hop.

On this note - I have now lowered my tire pressures to 32psi and still have hop. I refuse to go any lower simple because I don't want to murder my fuel economy or wear my tires faster.

I think the next order of business is to get a camera under the car and see if I can pinpoint what exactly is allowing so much movement - Gives me an excuse to order a new gopro or something similar

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