Curb Weight
11-05-2002, 11:31 AM
#22
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As for reducing the understeer, the best solution would be to raise the tire psi of the rears a tad...
11-05-2002, 11:43 AM
#23
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Originally posted by steve c
Actually, that will make it worse. Incrased pressure in the front and decreased pressurein the rear will reduce understeer and induce more oversteer.
Actually, that will make it worse. Incrased pressure in the front and decreased pressurein the rear will reduce understeer and induce more oversteer.
11-05-2002, 12:51 PM
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Hedonist is indeed correct. More tire pressure reduces grip unless the tire is so under inflated that it was overheating.
Competition tires have an optimum working temperature so you want to keep the tire in the optimum with the minimum of pressure (unless of course you want to deliberately induce under or oversteer).
Road tires are similar in nature.
Competition tires have an optimum working temperature so you want to keep the tire in the optimum with the minimum of pressure (unless of course you want to deliberately induce under or oversteer).
Road tires are similar in nature.
11-06-2002, 09:52 AM
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Actually no, you got it the wrong way around. If you increased pressure in the front and dropped pressure in the rear it would make the rear tires flex and grip more causing your understeer to get a whole lot worse, expecially if you add air to the front tires. Best idea would be to ad air to rears alone.
Hedonist is indeed correct. More tire pressure reduces grip unless the tire is so under inflated that it was overheating.
More proof?
http://rogerkrausracing.com/overundr.html
11-10-2002, 05:09 AM
#29
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I'm afraid we are all grossly over simplifing the tire pressure Phenomena so I found an excellent source of information for everyone who is truly interested in maximizing the Z's potential on track. Note: I think the article in the link is for those of us who
a) are very ****
b) have access to lots of track time
c) are very ****
d) are interested in the science of driving fast
Here's a snippet for the rest of us:
On the track, you're going to work the tires much more than is possible on the street. Repetitive, high cornering forces and aggressive braking are going to generate much more heat and therefore higher tire pressures. Because of this, the typical pressures you run on the street are going to be too high for the race track. During normal street driving, tire pressures will increase over the recommended factory "cold" settings about 2-4 psig. During racing, a cold tire pressure setting will increase anywhere from 6 to 10 psig. Tire pressures must be lowered from their usual street settings before going onto the track. So, if you're using street tires on the track, the generic, "start somewhere" point is 5 psig lower than the car manufacturer's recommended tire pressures. (Note: use the car manufacturer's recommended tire pressure as the baseline.
If the tires felt very slippery, especially if they got worse on every lap, then the tire pressure is too high. Take each tire pressure and write it down. If only the front or rear tires felt slippery (the front was slippery if the car understeered and wouldn't respond to more steering input, the back was slippery if the car wanted to oversteer and spin), then lower the pressure of just that pair by 4 psig while they're still hot. Try this setting for the next session.
If the tires felt spongy, then the tire pressures are too low.When the pressures are too low, they will have low grip and still tend to slide like a tire that is too hard, but the feeling will be different. Instead of a smooth slippery slide, the tire will scrub and have more vibration in the slide. The difference is subtle, but you'll have feel for it in the steering wheel, and from the seat in your legs and back. In this case, increase the pressure while the tires are hot by 2 psig. Try this setting for the next session.
Here is a link to the full article as well as a wealth of other information on car tuning.
http://www.turnfast.com/tech_handlin...pressure.lasso
a) are very ****
b) have access to lots of track time
c) are very ****
d) are interested in the science of driving fast
Here's a snippet for the rest of us:
On the track, you're going to work the tires much more than is possible on the street. Repetitive, high cornering forces and aggressive braking are going to generate much more heat and therefore higher tire pressures. Because of this, the typical pressures you run on the street are going to be too high for the race track. During normal street driving, tire pressures will increase over the recommended factory "cold" settings about 2-4 psig. During racing, a cold tire pressure setting will increase anywhere from 6 to 10 psig. Tire pressures must be lowered from their usual street settings before going onto the track. So, if you're using street tires on the track, the generic, "start somewhere" point is 5 psig lower than the car manufacturer's recommended tire pressures. (Note: use the car manufacturer's recommended tire pressure as the baseline.
If the tires felt very slippery, especially if they got worse on every lap, then the tire pressure is too high. Take each tire pressure and write it down. If only the front or rear tires felt slippery (the front was slippery if the car understeered and wouldn't respond to more steering input, the back was slippery if the car wanted to oversteer and spin), then lower the pressure of just that pair by 4 psig while they're still hot. Try this setting for the next session.
If the tires felt spongy, then the tire pressures are too low.When the pressures are too low, they will have low grip and still tend to slide like a tire that is too hard, but the feeling will be different. Instead of a smooth slippery slide, the tire will scrub and have more vibration in the slide. The difference is subtle, but you'll have feel for it in the steering wheel, and from the seat in your legs and back. In this case, increase the pressure while the tires are hot by 2 psig. Try this setting for the next session.
Here is a link to the full article as well as a wealth of other information on car tuning.
http://www.turnfast.com/tech_handlin...pressure.lasso
11-10-2002, 06:42 AM
#30
steve c, I like Flyingscot's explanation above. 
[QUOTE]Originally posted by steve c
[B]Actually no, again, you both have that reveresed. To reduce understeer you want to inflate the fronts more and deflate the rears a bit.
We need to consider the 350Z and it's tire characteristics here. Another post noted that on a flat RE040 tire, the sidewall was so stiff that the wheel did not come down on the tread as he limped to a gas station. Makes sense for a low profile tire, so adding or decreasing tire pressure will have more effect (on our cars) of NOT changing the sidewall flex, but instead have more effect on the size of the tire patch in contact with the ground - hence, increasing tire pressure on the tires of the front of an understeering Z car will decrease the size of the tire patch of the front tires and lead to decreased grip which equates to INCREASED understeer!
[QUOTE]Originally posted by steve c
[B]Actually no, again, you both have that reveresed. To reduce understeer you want to inflate the fronts more and deflate the rears a bit.
We need to consider the 350Z and it's tire characteristics here. Another post noted that on a flat RE040 tire, the sidewall was so stiff that the wheel did not come down on the tread as he limped to a gas station. Makes sense for a low profile tire, so adding or decreasing tire pressure will have more effect (on our cars) of NOT changing the sidewall flex, but instead have more effect on the size of the tire patch in contact with the ground - hence, increasing tire pressure on the tires of the front of an understeering Z car will decrease the size of the tire patch of the front tires and lead to decreased grip which equates to INCREASED understeer!
11-10-2002, 10:15 AM
#31
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hence, increasing tire pressure on the tires of the front of an understeering Z car will decrease the size of the tire patch of the front tires and lead to decreased grip which equates to INCREASED understeer!
This is the same concept I use on my track cars when racing -- with much stiffer Hoosier RS303's.
11-10-2002, 03:27 PM
#32
Originally posted by steve c
No. The 350's tires are not magical and they adhere to the same principles as the rest of the tires in the world. Again, increase pressure in the front and decrease it in the rears to reduce understeer and induce oversteer.
This is the same concept I use on my track cars when racing -- with much stiffer Hoosier RS303's.
No. The 350's tires are not magical and they adhere to the same principles as the rest of the tires in the world. Again, increase pressure in the front and decrease it in the rears to reduce understeer and induce oversteer.
This is the same concept I use on my track cars when racing -- with much stiffer Hoosier RS303's.
Racing tires have much thinner sidewalls to radiate heat and they flex more than a street tire sidewall which will flex less or be less responsive to the change in tire pressure.
(I think we agree to disagree here!)
11-14-2002, 04:33 AM
#34
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Originally posted by ChinaClipper
Respectfully disagree again!
Racing tires have much thinner sidewalls to radiate heat and they flex more than a street tire sidewall which will flex less or be less responsive to the change in tire pressure.
(I think we agree to disagree here!)
Respectfully disagree again!
Racing tires have much thinner sidewalls to radiate heat and they flex more than a street tire sidewall which will flex less or be less responsive to the change in tire pressure.
(I think we agree to disagree here!)
Huh? This is NOT my experience with Hoosiers, to Toyos, to Kumhos. Can you cite a reference that explains these characteristics?
The Pirelli racing slicks I was looking at the other day have brutally stiff sidewalls; enough so that the shop broke the bead on one of the tires trying to get it on the rim; turned the tire into a $400 paperweight.
11-14-2002, 07:29 AM
#35
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True, racing tires are MUCH stiffer than the stiffest street tire -- and the principle of changing pressures to increase / decrease oversteer and understeer still apply.
The local shop usually charges me an extra 5 bucks per tire because they are such a PITA to get on.
The local shop usually charges me an extra 5 bucks per tire because they are such a PITA to get on.
11-14-2002, 08:10 AM
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Steve C, agreed.
I've spent a bunch of time at the track, on street tires, on various R comps, and have worked as pit crew for some bmw cca club racers. I've driven R comps on the street as well.
As a general rule, all the R comps I've been on are far stiffer than streets. And, the tire guys generally frown when I roll in with R comps to get mounted up. They usually hand them off the biggest gorilla at the shop to handle them.
True racing slicks are even worse than R comps.
I've spent a bunch of time at the track, on street tires, on various R comps, and have worked as pit crew for some bmw cca club racers. I've driven R comps on the street as well.
As a general rule, all the R comps I've been on are far stiffer than streets. And, the tire guys generally frown when I roll in with R comps to get mounted up. They usually hand them off the biggest gorilla at the shop to handle them.
True racing slicks are even worse than R comps.
11-14-2002, 10:23 AM
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Registrations usually list the maximum weight for the price of that registration category. example: my registration is $72.00 for vehicles less than 3500 lb GVW. This does not mean the Z weighs 3500 pounds, but is under 3500 pounds and the fee for that class of vehicles is $72.00.
11-14-2002, 11:15 AM
#38
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Originally posted by mydogscool
Registrations usually list the maximum weight for the price of that registration category. example: my registration is $72.00 for vehicles less than 3500 lb GVW. This does not mean the Z weighs 3500 pounds, but is under 3500 pounds and the fee for that class of vehicles is $72.00.
Registrations usually list the maximum weight for the price of that registration category. example: my registration is $72.00 for vehicles less than 3500 lb GVW. This does not mean the Z weighs 3500 pounds, but is under 3500 pounds and the fee for that class of vehicles is $72.00.
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