Kumho dissapointment

[marcus_GTS]

Well, I just got a set of Kumhos put on my GT-S. They're brand new, so the grip is dissapointing, but I expect it to get a lot better as the tires wear a bit. What I do find very dissapointing is that the car doesn't seem to respond as well as it did with the stock yokos. I'm guessing this is a sidewall stiffness issue, and so it will not get better as the tire ages. Anyone else notice this? Has anyone played with tire pressures to get better handling?

[TRD Liquid Silver]

yes there is a difference when the 712's are new vs when you have a few miles on them. i've got 6k miles on mine and it's a lot stickier @6k compared to when i first put them on. it responds better in the slaloms than the yoko's. the yoko's were great going straight but the sidewall's were very weak. my first solo2 in the celica with the yoko's the sidewalls got chewed. the kuhmo's never got chewed the first time and i've autox it 3 times since and they're still the same.

the 712 will get better the more you use them. i was like you when i first got them on and now i'm more than happy. where else can you find this kind of tire for $80.

[marcus_GTS]

That's good news to me. What pressures are you running? Do you run different pressures for solo2?

[TRD Liquid Silver]

Originally posted by marcus_GTS
That's good news to me. What pressures are you running? Do you run different pressures for solo2?

well i've got the stock 16" rims and whenever i go autox i'll run 45-48 psi front and 38-40 psi rear. if you decrease pressure at the back it'll reduce understeer and it'll rotate the rear end a "bit" in turns. also fwd cars with more pressure in the front and less in the back will give it more of neutral feel in a solo2 course.

[NoCones]

Originally posted by TRD Liquid Silver
well i've got the stock 16" rims and whenever i go autox i'll run 45-48 psi front and 38-40 psi rear. if you decrease pressure at the back it'll reduce understeer and it'll rotate the rear end a "bit" in turns.

At those pressures, I doubt that decreasing the rears reduces understeer. At 38-40 psi, I can't imagine you're rolling the rears onto the sidewall, so decreasing pressure is going to increase rear grip...aka more understeer.

[TRD Liquid Silver]

Originally posted by NoCones


At those pressures, I doubt that decreasing the rears reduces understeer. At 38-40 psi, I can't imagine you're rolling the rears onto the sidewall, so decreasing pressure is going to increase rear grip...aka more understeer.

my bad, i always get confused with the two. celica's have a nasty habit of oversteering. by reducing the pressure at the rear and increasing pressure at the front it should induce a little more understeer.

i've ran lower pressure than 38-40psi at the rear before but i don't like the feeling of the rear breaking out more than it should. i think running 38-40 rear pressure gives the celica a more neutral feel.

[NoCones]

Originally posted by TRD Liquid Silver
i've ran lower pressure than 38-40psi at the rear before but i don't like the feeling of the rear breaking out more than it should. i think running 38-40 rear pressure gives the celica a more neutral feel.
again, the lower pressures should be keeping the rear end more stable...

Bryan

[TRD Liquid Silver]

Originally posted by NoCones

again, the lower pressures should be keeping the rear end more stable...

Bryan

yes it will and that's what you want from fwd car.

[NoCones]

Just doesn't make sense to me that you say you've run lower than 38-40 psi, but you don't like how it makes the rear "break out more than it should"...I read that to mean you get more oversteer with the lower pressure...that's contradictory to what I said (and you agreed to) about rear tire pressures (isn't it?)

[TRD Liquid Silver]

the point i was making was and i'll try and make it simple. if you don't want your car to plow into the cones while turning, increase front tire pressure and decrease rear tire pressure.

what i meant before was i've ran lower pressure's in the rear than 38-40psi and i didn't like it. i don't like it when the rear break's out too much..

[NoCones]

Originally posted by TRD Liquid Silver
the point i was making was and i'll try and make it simple. if you don't want your car to plow into the cones while turning, increase front tire pressure and decrease rear tire pressure.

what i meant before was i've ran lower pressure's in the rear than 38-40psi and i didn't like it. i don't like it when the rear break's out too much..
Thank's for making it so simple. Now it's abundantly clear that you don't know what you're talking about. :fawk:

Bryan

[NSX_GTR_LM]

Originally posted by NoCones

Thank's for making it so simple. Now it's abundantly clear that you don't know what you're talking about. :fawk:

Bryan


:rofl: :rofl:


Since no cones doesn't feel like explaining it to you, i will try. Please correct me if i am wrong mister cones :)

By decreasing the pressure in the rear, you create a larger contact patch with the ground, creating more understeer. It would be actually better if you increased the rear pressure to get more oversteer, but those pressures are astronomical anyways, so you may want to check your whole setup.

[soceur]

Originally posted by NoCones

Thank's for making it so simple. Now it's abundantly clear that you don't know what you're talking about. :fawk:

Bryan
ROFLMBO!! iT was like a build up..no cones was trying to be patient until there was no point to any longer. Good thread:)

[NoCones]

ok, let's lay it out nice and slow...

Understeer = front loses traction before rear
Oversteer = rear loses traction before front

There's a tire pressure that's optimum for front grip and a tire pressure that's optimum for rear. I have little doubt that the pressures you quoted are above the optimium for a Kumho 712 (esp in the rear).

Therefore:
Decreasing the rear pressure will increase the grip in the rear = less oversteer = more understeer = the rear end "breaks out" less

Additionally:
If you don't want to "plow (= understeer) into the cones while turning," you need to reduce understeer by decreasing the front pressure (moving toward optimum grip) or you could increase rear pressures (moving even further from optimum in the rear).

Of course, a great deal of cone plowing is due to driving too hard into a corner, which air pressure is never going to make up for...

I tried to make it simple for you ;)

[TRD Liquid Silver]

Originally posted by NoCones
ok, let's lay it out nice and slow...

Understeer = front loses traction before rear
Oversteer = rear loses traction before front

There's a tire pressure that's optimum for front grip and a tire pressure that's optimum for rear. I have little doubt that the pressures you quoted are above the optimium for a Kumho 712 (esp in the rear).

Therefore:
Decreasing the rear pressure will increase the grip in the rear = less oversteer = more understeer = the rear end "breaks out" less

Additionally:
If you don't want to "plow (= understeer) into the cones while turning," you need to reduce understeer by decreasing the front pressure (moving toward optimum grip) or you could increase rear pressures (moving even further from optimum in the rear).

Of course, a great deal of cone plowing is due to driving too hard into a corner, which air pressure is never going to make up for...

I tried to make it simple for you ;)

www.wtrscca.org/tech.htm#problems (http://www.wtrscca.org/tech.htm#problems)

well it seems that you guys have a different set-up when it comes to autox. from "my" understanding if your plowing or understeering you should increase tire pressure in the front and if you want to promote a little understeer for a FWD car you should run lower pressure in the rear. this is from talking to a few guys on the solo2 circuit.

i love the maturity of this thread. what i meant by making it simple was explaining the X's and O's it was in no way pointing fingers..

[NSX_GTR_LM]

well, physics is physics man, seriously, its the opposite. It should make more sense to you that decreasing pressure puts more of the tire in contact with the road. I will read that article and get back to you.

[NSX_GTR_LM]

I just read the article. maybe no senor cones can verify it better than me.

[autxr]

From the perspective of maximum frictoin (grip) most folks don't understand how a tire works (me included), but from a lot of trial and error (tuning), ive decided the MAXIMUM grip is achieved at the LOWEST pressure that keeps the tread on the ground.

Let's consider the simple case (straight line). In drag racing, you go with big fat tires on the drive wheels (for traction) and skinny little tires for the non-drive wheels. In our cars, we put the fornt pressures to about 20 psi and the rears up at 50 psi, this give the best grip up front and the lowest friction (grip) in the rear.

Well, guess what, that applies to cornering as well.

Now, add lateral forces into the equation.

If the pressure is too low, you begin to roll over onto the sidewall. There isn't any grip there, the farther you go, the less tread is on the road, the less grip you have.

Now, you have exceeded the limits of the TIRE.

So, what do we do, we compromise, we put more air in. This stiffens the sidewalls, and keeps the tread on the ground for a longer period of time, thus we can corner faster.

Eventually, you will go to far, and the high pressure will start to take away grip. It is a balance.

The rear is no different than the front. If you are oversteering, the first thing you have to determine is if it is due to under inflation (thus rolling the tire over), or overinflation (not enough contact patch).

It just happens that after 400+ autocross runs in the Celica Yes, that DOES make me an expert), I have NEVER seen a case of underinflation, even with as little as 17 psi in the back tires.

If I am loose, I bleed air out, every time. Adding air would have never helped me, not even a little bit.

When I let another fellow drive my car, he decided it wasn't loose enough, what did we do, we put 10 psi IN the back tires, he was almost happy, he said he wanted another 5 or 10 psi to really loosen it up.

Real world results, backing up real world theory.

So, the most grip? The lowest pressure you can run without overloading the sidewalls of the tire.

Not enough theory?

The sidewall of a tire is a spring. In a car, a spring regulates weight transfer. The softer the spring the more the weight transfer, thus the higher the loading.

The higher the load on a tire, the more friction, basic physics.

Drag race: high pressure in the rear (stiffer spring), low pressure front (softer spring), more grip up front.

Cornering, high pressure rear (stiffer spring), low pressure front (softer spring), more grip up front (until you bend the spring - roll on the sidewalls).

Clear as mud?

Thought so.

Scott

[NoCones]

Originally posted by TRD Liquid Silver
from "my" understanding if your plowing or understeering you should increase tire pressure in the front and if you want to promote a little understeer for a FWD car you should run lower pressure in the rear. this is from talking to a few guys on the solo2 circuit.

i love the maturity of this thread. what i meant by making it simple was explaining the X's and O's it was in no way pointing fingers..
Well I interpreted you keeping it simple for me as an insult...I don't think that's a stretch.

Bottom line: if you're happy with what your adjustments do to your car, have a field day.

Throw my 200+ Celica runs in with Scott's 400, though, and I think you'd be silly not to listen.

Bryan

[TRD Liquid Silver]

Originally posted by NoCones

Well I interpreted you keeping it simple for me as an insult...I don't think that's a stretch.

Bottom line: if you're happy with what your adjustments do to your car, have a field day.

Throw my 200+ Celica runs in with Scott's 400, though, and I think you'd be silly not to listen.

Bryan

no it wasn't an insult but your smilie was defintely a stretch..

i don't think the number of times you and scott have ran your car is valid reason for me to run your respective setup. it's like you telling me you've eaten frosted flakes 300 times and it's good so i should like it too. every driver likes different set-ups. i think michael schumacher and juan montoya likes their cars setup a little different from each other.

i don't think running lower pressure in the front and higher pressures in the rear would reduce understeer. just think about it. in a drag race you run lower pressure in the front for maximum contact patch and traction while running higher rear pressure(scott). if you ran on a solo2 course with just kuhmo's 712 and ran lower psi(front tires) you'd roll the sidewalls and get your tires chewed which would cause the vehicle to understeer cause there's no traction from the sidewalls. if your going straight a'la drag race running lower pressure (front) would help because there's more contact patch with the surface.


that's my reasoning behind all this..
that's it for me i'm going to see SPIDERMAN...

[NSX_GTR_LM]

Originally posted by TRD Liquid Silver


no it wasn't an insult but your smilie was defintely a stretch..

i don't think the number of times you and scott have ran your car is valid reason for me to run your respective setup. it's like you telling me you've eaten frosted flakes 300 times and it's good so i should like it too. every driver likes different set-ups. i think michael schumacher and juan montoya likes their cars setup a little different from each other.

i don't think running lower pressure in the front and higher pressures in the rear would reduce understeer. just think about it. in a drag race you run lower pressure in the front for maximum contact patch and traction while running higher rear pressure(scott). if you ran on a solo2 course with just kuhmo's 712 and ran lower psi(front tires) you'd roll the sidewalls and get your tires chewed which would cause the vehicle to understeer cause there's no traction from the sidewalls. if your going straight a'la drag race running lower pressure (front) would help because there's more contact patch with the surface.


that's my reasoning behind all this..
that's it for me i'm going to see SPIDERMAN...


You just explained it for yourself. Lower pressure in the front gives dragsters more grip right? It also gives you more grip as well. As scott said before, the best PSI is low enough not to roll the sidewalls, because then you are exceeding the limits of your tire. Therefore by reasonably lowering the front pressures, you increase the grip in the front. More grip in the front = more oversteer. You are almost there :)

And the analogy about frosted flakes was pretty poor btw. They were trying to tell you they are experienced in dealing with this sheeit. You really should listen to them.

[TRD Liquid Silver]

Originally posted by NSX_GTR_LM



You just explained it for yourself. Lower pressure in the front gives dragsters more grip right? It also gives you more grip as well. As scott said before, the best PSI is low enough not to roll the sidewalls, because then you are exceeding the limits of your tire. Therefore by reasonably lowering the front pressures, you increase the grip in the front. More grip in the front = more oversteer. You are almost there :)

And the analogy about frosted flakes was pretty poor btw. They were trying to tell you they are experienced in dealing with this sheeit. You really should listen to them.

did you just read what i said?

scott is saying that you should technically run lower pressures in the front and higher in the back. how can you run lower-front and higher-rear. by running lower psi-front on fwd car your promoting understeer which you don't want. what i'm trying to say it should be the other way around. with the celica you should run higher pressure-front and lower pressure-rear to promote understeer from a FWD car.

[NSX_GTR_LM]

Originally posted by TRD Liquid Silver


did you just read what i said?

scott is saying that you should technically run lower pressures in the front and higher in the back. how can you run lower-front and higher-rear. by running lower psi-front on fwd car your promoting understeer which you don't want. what i'm trying to say it should be the other way around. with the celica you should run higher pressure-front and lower pressure-rear to promote understeer from a FWD car.



AHHHHHHHHHHH. You just said dragsters get more traction by running lower PSI in the front. Scott just told you to run as low PSI that still allows your tire's sidewalls not to scrub. More traction in the front = oversteer, therefore as low as possible PSI in the front without the sidewalls caving in produces more grip in the front, more oversteer. If you dont get it after that, I am just gonna let you go. I highly reccommend you listen to scott and cones on this one.

[NoCones]

Wow. I'm almost afraid to comment. Aaah, what the heck.

I'm not sure how you're interpreting what we've said...I hope you don't think we've said that you should run a higher pressure in the rear than in the front...your last few posts make me wonder.

Let's see if I can pose 2 statements that can't be misconstrued, and maybe we'll leave it at that. For a given tire of concern:
1. If you're losing traction because the sidewall is failing...increase pressure to increase grip on that tire.
2. If you're losing traction because the contact patch loses grip, decrease pressure to increase grip on that tire.

why is it that you value the opinions of the "few guys you talked to on the solo2 circuit," but the experience of 2 guys with 600+ runs of Celica autox tuning is equivalent to a bowl of Frosted Flakes?
:closed:
Bryan

[TRD Liquid Silver]

Originally posted by NoCones
Wow. I'm almost afraid to comment. Aaah, what the heck.

I'm not sure how you're interpreting what we've said...I hope you don't think we've said that you should run a higher pressure in the rear than in the front...your last few posts make me wonder.

Let's see if I can pose 2 statements that can't be misconstrued, and maybe we'll leave it at that. For a given tire of concern:
1. If you're losing traction because the sidewall is failing...increase pressure to increase grip on that tire.
2. If you're losing traction because the contact patch loses grip, decrease pressure to increase grip on that tire.

why is it that you value the opinions of the "few guys you talked to on the solo2 circuit," but the experience of 2 guys with 600+ runs of Celica autox tuning is equivalent to a bowl of Frosted Flakes?
:closed:
Bryan

ok, let's take away your 600+ runs with scott and let's say it's your first time out with the celica. what would you do to prevent understeer? also i'll give you the scenario that you had 40psi at all 4 tires, but you were still understeering. what do you do? do you take out more pressure in the "front" or add more pressure? this question goes for the rear tires as well.

maybe this will end all the back and forth bickering. remember don't bring in your 600+ runs, this is your first time in the celica.

[NSX_GTR_LM]

Lower the pressure in the front to create a greater contact patch, allowing more grip in the front. More grip in the front = more oversteer. More oversteer = less understeer. Thats what I would do. I have autocrossed 0 times in a celica, only about 15 times in other cars.


The rear PSI will depend on the suspension setups, but thats too many variables that haven't been tossed in right now. If you are understeering, and you want to get rid of it, at some point you will have to lower the PSI in the front if you dont wanna mess with anything else.

[TRD Liquid Silver]

Originally posted by NSX_GTR_LM
Lower the pressure in the front to create a greater contact patch, allowing more grip in the front. More grip in the front = more oversteer. More oversteer = less understeer. Thats what I would do. I have autocrossed 0 times in a celica, only about 15 times in other cars.


The rear PSI will depend on the suspension setups, but thats too many variables that haven't been tossed in right now. If you are understeering, and you want to get rid of it, at some point you will have to lower the PSI in the front if you dont wanna mess with anything else.

why would you lower the tire pressure up front if your already understeering @40psi. by lowering the psi your giving the tire more flex so you'll be running the sidewalls more than before. there's no grip using the sidewall of the tire for cornering. you want to use as much of the contact patch and not the sidewalls while cornering. that's why people who under inflate their tires in solo2 events get's their sidewalls chewed out.

i put more air in the front tires to decrease understeer. that way i'm not riding the sidewalls when i'm hitting a turn or corner. running lower pressure in the back with higher pressure in front will give a fwd a car a little oversteer. which most fwd owners like.

that's where the debate started. i feel that you need to run higher pressure in the front and lower pressure in the back to decrease understeer on a fwd car.

lowering the front tire pressure will benefit a car that's going straight (1/4 mile) but running low pressure in the front in a solo2/autox course will result in tire wear (sidewalls). if you think about it. to get a fwd drive car to slide or breakout out the rear end (oversteer) in a corner people put less pressure in the rear tires. just imagine what that would do to the front tires if you lower the pressure. the only reason why the rear tires or end would slide out cause it lost traction due to the lower tire pressure.

[NSX_GTR_LM]

ok, do what you like. Its up to you, but good luck with whatever setup you use. Why not post this question on a different forum. One more thing. At 40 PSI, i hardly think you are using the sidewalls, i think you are simply breaking the tires loose. Thats why scott runs at like 17.

[TRD Liquid Silver]

Originally posted by NSX_GTR_LM
ok, do what you like. Its up to you, but good luck with whatever setup you use. Why not post this question on a different forum. One more thing. At 40 PSI, i hardly think you are using the sidewalls, i think you are simply breaking the tires loose. Thats why scott runs at like 17.

he's running 17 at the rear tires. ask him what he's running in the front.

40psi with the stock 16" wheels and tires is still not enough to prevent sidewall chews. i run 45-48psi front and 38-40psi rear. scott probably runs 17psi in the rear cause he likes more oversteer. every drivers different...

[Bling]

You are not gonna roll onto the sidewalls at 40psi.

[NSX_GTR_LM]

Originally posted by Bling
You are not gonna roll onto the sidewalls at 40psi. :werd:

[Karim]

agreedd at 40 psi your most likely not going to be losing grip cause your rolling over on the side wall it will because you need a greater contact path in front to have the grip to pull you through the corner, so you lower the psi in front increasing front grip to pull you through a corner

Karim

[autxr]

Man, this just isn't working...

The first time (and almost every tiome for 2 years

[mac340]

well after reading all that i just have one question and its for TRD Liquid Silver. Was SPIDERMAN any good? hehe

[autxr]

It was OK, but not as good as the hype or the record ticket $$$. Of course I was never a big comic book guy. I might claim to know most everything about tires, but I am NOT a movie critic.

I won't say all the things I didn't like, I don't want to spoil it. It was worth the matinee price of $5.25.

Scott