Can someone help me with tire pressures on R-Compounds please?
06-03-2005, 03:02 PM
#1
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Can someone help me with tire pressures on R-Compounds please?
I have a D.E. event this weekend and this is my first time out on my race tires (Yokohama A032R-H) and I would like to know what's a good starting point for air pressure. It's going to be in the 90's both days.
My car is a '99 C2
Tire size = (F) 245/45-17 (R) 275/40-17 Full tread depth tires.
TIA!
My car is a '99 C2
Tire size = (F) 245/45-17 (R) 275/40-17 Full tread depth tires.
TIA!
06-03-2005, 06:31 PM
#3
Race Car
Mark is much faster than me, so take this with a grain of salt. But I've always run the A032R's much lower than Hoosiers (which would start at about the pressures Mark mentions).
With AO32R's, I start at 23/25 cold and bleed off above 25/29 hot. Above 30, A032R's start getting greasy. Above 34 they get really lousy.
Caveats: I haven't run A032R's since they switched to a hard and a soft compound, and my car weighs 2400 pounds. In your case, I'd add maybe a pound of pressure for every 100-200 pounds your car is heavier than mine.
Better still, contact Tire Rack or a Yokohama rep to get their opinion, and post it here.
With AO32R's, I start at 23/25 cold and bleed off above 25/29 hot. Above 30, A032R's start getting greasy. Above 34 they get really lousy.
Caveats: I haven't run A032R's since they switched to a hard and a soft compound, and my car weighs 2400 pounds. In your case, I'd add maybe a pound of pressure for every 100-200 pounds your car is heavier than mine.
Better still, contact Tire Rack or a Yokohama rep to get their opinion, and post it here.
06-03-2005, 06:49 PM
#4
Rennlist Member
Jack is right, i was just starting at a pressure that was on the high side as to not russle anyones feathers (all the high pressure spinners out there!)
seriously, i once saw a bunch of NSX guys at a driving event and they were all spinning at every corner of the track. they all had one thing in common, (besides being new to the track thing) they all had set their pressures to 40psi!!
anyway, at the end of the day, they reluctantly reduced the pressures to about 29psi. i generally think that with most DOT race rubber, 28-30psi is a good range to run in .
If i remember the a032r correctly, it had a stiff sidewall so we did run some lower pressures with good luck.
MK
seriously, i once saw a bunch of NSX guys at a driving event and they were all spinning at every corner of the track. they all had one thing in common, (besides being new to the track thing) they all had set their pressures to 40psi!!
anyway, at the end of the day, they reluctantly reduced the pressures to about 29psi. i generally think that with most DOT race rubber, 28-30psi is a good range to run in .
If i remember the a032r correctly, it had a stiff sidewall so we did run some lower pressures with good luck.
MK
Originally Posted by JackOlsen
Mark is much faster than me, so take this with a grain of salt. But I've always run the A032R's much lower than Hoosiers (which would start at about the pressures Mark mentions).
With AO32R's, I start at 23/25 cold and bleed off above 25/29 hot. Above 30, A032R's start getting greasy. Above 34 they get really lousy.
Caveats: I haven't run A032R's since they switched to a hard and a soft compound, and my car weighs 2400 pounds. In your case, I'd add maybe a pound of pressure for every 100-200 pounds your car is heavier than mine.
Better still, contact Tire Rack or a Yokohama rep to get their opinion, and post it here.
With AO32R's, I start at 23/25 cold and bleed off above 25/29 hot. Above 30, A032R's start getting greasy. Above 34 they get really lousy.
Caveats: I haven't run A032R's since they switched to a hard and a soft compound, and my car weighs 2400 pounds. In your case, I'd add maybe a pound of pressure for every 100-200 pounds your car is heavier than mine.
Better still, contact Tire Rack or a Yokohama rep to get their opinion, and post it here.
06-06-2005, 09:12 AM
#5
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Thread Starter
Thanks guys. I didn't get the chance to read any replies before I left BUT after about 4 adjustments I ended up with 32(f) and (35)r hot. When I say hot I mean HOT. I would hot pit, check my pressures and go back out.
I guess I could have gone lower but the car handled well.
I guess I could have gone lower but the car handled well.
Last edited by NickS; 06-06-2005 at 09:56 AM.
06-06-2005, 09:53 AM
#6
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Nick... and everyone else.
PLEASE pay attention to what Mark said. Running R tires below 25-6lbs cold in a normal car is really pushing your luck with tire health. Jack, you do have a light car, and that is a big factor, but it is NOT a good idea with a regular sedan over 26-2700lbs.
Mark's advice was very sound. If you don't know, start out safe and work from there. You have to REALLY be aware of the need to divorce what feels good (comforting) to the driver from what is fastest, and safest for the tire. Oddly enough, fastest and safest are usually in the same range; 28-32 cold. You just have to have the chops to use it!
Most novice-to-intermediate drivers will not like a tire starting at 28-32-ish because they will feel skatey. Normally this equates to about 34-5psi hot for the less aggressive driver, a point where the tire will be hard and stiff from higher pressure, but never really heat up and get sticky. The softer, less edgy feel of reduced pressures will seduce you into going there, but it is not optimum.
The novice to low intermediate (or those with VERY light cars) can get away with such low pressures to some extent because they will not overheat the tires. However, if you progress to higher intermediate status and are heating those tires up well, you REALLY have to think about getting more air in them for support so that they don't overheat.
As I have said a million times, the key is cold-to-hot pressure rise. Anything more than a 10lb increase from cold-to-hot would suggest you seriously consider adding a bit of air to better support the tire and keep it happy and healthy.
PLEASE pay attention to what Mark said. Running R tires below 25-6lbs cold in a normal car is really pushing your luck with tire health. Jack, you do have a light car, and that is a big factor, but it is NOT a good idea with a regular sedan over 26-2700lbs.
Mark's advice was very sound. If you don't know, start out safe and work from there. You have to REALLY be aware of the need to divorce what feels good (comforting) to the driver from what is fastest, and safest for the tire. Oddly enough, fastest and safest are usually in the same range; 28-32 cold. You just have to have the chops to use it!
Most novice-to-intermediate drivers will not like a tire starting at 28-32-ish because they will feel skatey. Normally this equates to about 34-5psi hot for the less aggressive driver, a point where the tire will be hard and stiff from higher pressure, but never really heat up and get sticky. The softer, less edgy feel of reduced pressures will seduce you into going there, but it is not optimum.
The novice to low intermediate (or those with VERY light cars) can get away with such low pressures to some extent because they will not overheat the tires. However, if you progress to higher intermediate status and are heating those tires up well, you REALLY have to think about getting more air in them for support so that they don't overheat.
As I have said a million times, the key is cold-to-hot pressure rise. Anything more than a 10lb increase from cold-to-hot would suggest you seriously consider adding a bit of air to better support the tire and keep it happy and healthy.
06-06-2005, 10:00 AM
#7
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Thread Starter
I don't have a pyrometer and all I can go by is feel (seat of the pants, handling, etc) and inspecting the tires after each run.
Upon inspection of my tires I was getting even wear and the sidewalls were never rolling over past the indicator (little triangle) on the tire.
At the settings I had (see above reply) the car was planted, the tires never felt greasy and the car was very predictable.
I'm not saying you're wrong by any means... I appreciate and believe what you're saying. I just want you to know how I was making the decisions that I did. Please tell me if what I did was right or wrong.
Upon inspection of my tires I was getting even wear and the sidewalls were never rolling over past the indicator (little triangle) on the tire.
At the settings I had (see above reply) the car was planted, the tires never felt greasy and the car was very predictable.
I'm not saying you're wrong by any means... I appreciate and believe what you're saying. I just want you to know how I was making the decisions that I did. Please tell me if what I did was right or wrong.
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06-06-2005, 07:46 PM
#8
Race Car
Tire Break in
Originally Posted by NickS
I have a D.E. event this weekend and this is my first time out on my race tires (Yokohama A032R-H)
For me, Heat Cycling new tires pays off in 2-3 weekends. My experience has been new tires feel Great, pretty much no matter what... but if you break them in right, they feel sticky for much longer.
my cars pretty light too, I run 26/28 cold, look for 33-35 hot.
I'm also hot on the inside fronts, but I like the camber, and learn to live with it...
06-06-2005, 08:40 PM
#9
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Nick;
Most R-tires like to be around 40 hot. This usually equates to a pyrometer reading that will show a tire in the right temp range to optimize the rubber compound for grip. Anything under 35 hot is obviously not putting the tire in that range.
This tells me that you are a novice-to-low-intermediate driver, and there is no personal judgement of you being made there.
As I offered previously, you can indeed run those types of numbers and not be in trouble. At the same time, this thread will plant in your mind that if you do get quicker, you should expect to make pressure changes like those discussed here to keep your tires healthy and yourself safe.
Again, I must stress the importance of the pressure increase from cold to hot. no matter where you are on the scale, this is of paramount concern. If you started at 26 to get your 32/35 hot, well, you are within a safe 10lb increase, but you also have some room left for improvement regarding getting to 40 hot where the tire works best. The only way you are going to hit the magic 40 is to get faster, but you will also have to keep pace of cold-to-hot pressure increases, and add air to maintain a healthy 10psi +/- margin.
The ideal would be to start at 30-32 and hit 40 hot. This would give you very well supported tires, and good and sticky too. If you go over a 10lb increase, they will overheat and get greasy. The first part (well supported tires) is why Mark offered what he did; a safe set of tires. My sense is that you are at the "feels better at lower pressures" stage, and that is fine. Now, when you get quicker, you'll be armed with the right info to stay safe too!
Most R-tires like to be around 40 hot. This usually equates to a pyrometer reading that will show a tire in the right temp range to optimize the rubber compound for grip. Anything under 35 hot is obviously not putting the tire in that range.
This tells me that you are a novice-to-low-intermediate driver, and there is no personal judgement of you being made there.
As I offered previously, you can indeed run those types of numbers and not be in trouble. At the same time, this thread will plant in your mind that if you do get quicker, you should expect to make pressure changes like those discussed here to keep your tires healthy and yourself safe.Again, I must stress the importance of the pressure increase from cold to hot. no matter where you are on the scale, this is of paramount concern. If you started at 26 to get your 32/35 hot, well, you are within a safe 10lb increase, but you also have some room left for improvement regarding getting to 40 hot where the tire works best. The only way you are going to hit the magic 40 is to get faster, but you will also have to keep pace of cold-to-hot pressure increases, and add air to maintain a healthy 10psi +/- margin.
The ideal would be to start at 30-32 and hit 40 hot. This would give you very well supported tires, and good and sticky too. If you go over a 10lb increase, they will overheat and get greasy. The first part (well supported tires) is why Mark offered what he did; a safe set of tires. My sense is that you are at the "feels better at lower pressures" stage, and that is fine. Now, when you get quicker, you'll be armed with the right info to stay safe too!
06-06-2005, 09:03 PM
#11
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Hey;
Where does the heat in a tire come from? Not from surface scrub like most people think, but from mechanical flexure of the carcass. What supports a tire? Air. If a tire heats up too much, that means it is flexing too much. It must be undersupported. That means more air is needed.
More than a 10lb increase usually gives you a greasy tire. That also means a tire that is working very hard. I like to give my tires every break I can. They last longer that way.
It's all from experience.
Where does the heat in a tire come from? Not from surface scrub like most people think, but from mechanical flexure of the carcass. What supports a tire? Air. If a tire heats up too much, that means it is flexing too much. It must be undersupported. That means more air is needed.
More than a 10lb increase usually gives you a greasy tire. That also means a tire that is working very hard. I like to give my tires every break I can. They last longer that way.
It's all from experience.
06-06-2005, 10:30 PM
#12
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John - I defer to other's experience with Yokes but Pirelli suggests 36 hot for the Corsa and Michelin, 34 hot for the Cup. Both of those feel slidely at 40. Anyone tried the A048? They ae half the price of the Corsa/Cup up here.
06-06-2005, 11:22 PM
#13
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I agree with Bob, your rule may only apply to the tires you run. I run my Cups at 34 hot on a 3100lb car. I start out at around 25 cold. 40 would be way too high for them. I ran my old PZero C's at around 36 hot. I think each tire brand/make is unique in optimal pressure.
George
George
Last edited by George A; 06-06-2005 at 11:43 PM.
06-07-2005, 09:23 AM
#14
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Originally Posted by mrbillfll
These are shaved ? Right. were they heat cycled too?
06-07-2005, 09:35 AM
#15
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Gents;
Do not words like "most" and "usually" infer that I was not casting anything in stone here? OF COURSE it is down to each specific tire type and driver to come up with a pressure map that fits his equipment and driving style.
To say that an MPSC "gets greasy" at 40lbs tells us nothing. Was that because they don't like to be there, or that you overheated them? If you started at your 25 and hit 40, you DID overheat them! If you started at a more proper pressure that kept the increase to around 10psi, and they were greasy, then you may have proved a point. For the record, I started my MPSCs at 29/28/27/26 and hit the spec perfectly... which is 34-36 hot, by the by.
I have been trying for 10 years to explode the myth of underinflating performance tires because they "feel better." I have been trying in that time to give people a system whereby they can stay safe while they figure out how to PROPERLY fettle a set of track tires... and learn to drive.
Do not words like "most" and "usually" infer that I was not casting anything in stone here? OF COURSE it is down to each specific tire type and driver to come up with a pressure map that fits his equipment and driving style.To say that an MPSC "gets greasy" at 40lbs tells us nothing. Was that because they don't like to be there, or that you overheated them? If you started at your 25 and hit 40, you DID overheat them! If you started at a more proper pressure that kept the increase to around 10psi, and they were greasy, then you may have proved a point. For the record, I started my MPSCs at 29/28/27/26 and hit the spec perfectly... which is 34-36 hot, by the by.
I have been trying for 10 years to explode the myth of underinflating performance tires because they "feel better." I have been trying in that time to give people a system whereby they can stay safe while they figure out how to PROPERLY fettle a set of track tires... and learn to drive.