Need Help: Koni Spec Hoosier Tire Pressure
06-05-2008, 11:22 PM
#1
Need Help: Koni Spec Hoosier Tire Pressure
I got a set of 225/45/17 Hoosiers Koni Spec. The tires are used but still have about 50% left. I am going to Mosport for two days.
I was wondering what tire pressures people would recommend. I have RB sways on. The alignment is going to be set at -1.4 front and rear camber. I was told to start with about 28psi all around but wanted to get some advice from the crowd here. I ran in the intermediate group. Thanks in advance.
P.S:
TeamRX8:
Yes I did search.
I was wondering what tire pressures people would recommend. I have RB sways on. The alignment is going to be set at -1.4 front and rear camber. I was told to start with about 28psi all around but wanted to get some advice from the crowd here. I ran in the intermediate group. Thanks in advance.
P.S:
TeamRX8:
Yes I did search.
06-06-2008, 12:10 AM
#3
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Honestly, those air pressures sound way too low, even starting cold. I'd shoot for 40 front, and 38 rear, once hot. So maybe 5 psi less cold.
And don't over drive the tires
And don't over drive the tires
06-06-2008, 02:35 PM
#6
i run those tires on an 8 " rim. i start out at 32 front and 32 rear and adjust. For me ( I guess my driving style,) starting with higher pressures did not work well. I usually come off the track with pressures(as soon as i can check them) at a target of 40. Anything over that and the tires get greasy a little
My front tires will slip a little during that last 5 minutes of track time(after approx 20 mins on track) on corner exit but it is controllable understeer. I never had any problems with the rears. i am running only a slightly different camber.
You have to trust the grip a little more with these tires than say the RA 1's. And you can inadvertingly scrub a lot of speed off if you dont concentrate.
olddragger
My front tires will slip a little during that last 5 minutes of track time(after approx 20 mins on track) on corner exit but it is controllable understeer. I never had any problems with the rears. i am running only a slightly different camber.
You have to trust the grip a little more with these tires than say the RA 1's. And you can inadvertingly scrub a lot of speed off if you dont concentrate.
olddragger
06-06-2008, 04:19 PM
#7
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Does anyone have a good way to obtain these used tires? I have had no search luck.
Oh, do you have a wheel suggestion in 17x8 that is reasonable price, I'm thinking about going that way instead of a set of used stock rims.
Oh, do you have a wheel suggestion in 17x8 that is reasonable price, I'm thinking about going that way instead of a set of used stock rims.
06-06-2008, 05:26 PM
#8
Registered
I have 8 zillion of these tires. Start them BELOW 30 psi and see where you end up. There are not like a Toyo that you can start at 32 or 33 for a similar car. We start at 27 +/- shooting for a 39 psi target all the way around (this is for our two Koni Challenge cars).
OK guys---here is the real scoop on these tires. It is possible to buy them when they have little to no grip. If you're new to race tires, you won't know this. Race tires have a life to them and it's often (but not always) measured in "heat cycles". We've got less than 10 heat cycles on these tire and then they are no good to us. They might appear fine to someone else, but they are slower and have less grip. Let's define this "heat cycle" thing so everyone knows what I'm talking about. If you're a fast racer and/or you frequently perform a lot of tire data collection, you'll know what I'm talking about. If you don't own a tire pressure gauge then please don't comment on this thread---your just wasting everyone's time and misleading those who need to hear experience talkin'.
One heat cycle is obtained/earned/acheived when you take your car out on a track and raise the tires temperatures to operating range. This is much easier to do on a warm or hot day. Have you ever driven on a road course in winter with little to no grip? That's because you can't get enough heat in your tires to reach their operating range. A tire has a temperature (not pressure) where it works best. A race tire (some people call it an "R" compound) has a higher operating temp that a street or a performance tire. Each time you take your car out on the track, you put a heat cycle on your set of tires. Then your session might be over and you pull into your garage space or parking space or grass or whatever, raise your hood, take a whiz and wait for your next session. Congrats---you just put ONE heat cycle on your tires. Meanwhile your tires, engine and brakes have been cooling off and you're waiting to hit the track again. The next time you roll out, you'll be adding a SECOND heat cycle.
Most race tires have a usable life of XXX heat cycles before they begin to lose their grip and get slower. If you're a serious racer you would know this and could FEEL when the tires no longer have maximum grip. IF YOU ARE NEW TO RACE TIRES OR HAVE NEVER RUN THEM, IT IS POSSIBLE THAT WHEN YOU OBTAIN THESE TIRES THEY HAVE SEVERAL HEAT CYCLES (POSSIBLY TOO MANY HEAT CYCLES) AND/OR HAVE LOST THEIR GRIP. Often people don't know this when you're playing around in the NASA HPDE or similar venues. The difference from these too many heat cycled tires to a fast set can be 2 seconds a lap or more. Often, beginning drivers can't tell this and they think that just because they have "Hoosiers" they are going fast. I see it all the time. A stop watch, lap-timer or data acquistion is the only way to tell if you're going faster---not the type of tire you're using.
So how do you know if the really cool slicks you just bought have any life on them left? First off, the GAm hoosiers have less than 10 heat cycles use out of them (we've found). If you push them hard, they have less that 6. 6 Heat cycles is using the tires 3 times a day for 2 days. Some people get more life out of them, others less. It is possible to get more life out of the tires by running shorter sessions. Heavier cars put more demand on the same size tires than a lighter car does. We typically race for 2.5 hours in Grand Am and after the race we can use the tires for about 2 or 3 practice sessions and they are shot (both in heat cycles and remaining rubber left). Tires wear down. Softer tires (as a general rule) with more grip wear down faster. Often a tire manufacturer will mold in some "wear marks" on the tires that are excellent to use as reference to compare tread wear and determine tire life. Toyo and Hoosier wear marks are little holes about the size of a bb (as in bb gun). Look closely and you'll find them. If a tire is very worn, it's possible that the wear marks are worn out! Gone!
Why am I writing this long email? Because you don't know this stuff until you buy several sets of used tires only to later buy your first set of NEW tires and realize that they are much faster and tons more grip.
For excellent tire wear and very good grip, may I suggest the Toyo RA1 (now called the R888 I believe). When you start it out as a full tread depth rain tire, you'll get 30 plus heat cycles out of them. This is about the most you'll see out of an "R" compound. Faster tires will always offer LESS heat cycles. Think about F1 and NASCAR---a few laps, pit, tire change and the TV closeups show them blistered and shot. These are some really fast tires with a ton of grip----but they don't last long at all. When you have The Toyo's shaved down to 4/32" (this is a common shave for the Toyo), you'll get about 20 heat cycles out of them. 20 FAST heat cycles. This is 3 weekends of really assertive driving. Want to go faster? Shave it to 3/32". Faster yet? 2/32". 2/32" is the fastest but will last about 4-6 cycles before it wears out. I've found the 3/32" to be the fastest at the 3 to 5 heat cycle range. They will last for an entire weekend of Club Racing and be very, very fast.
Summary: Fast rubber cost money. To race with the big boys, plan on spending a grand for a set of tires PER weekend (the GAm Hoosiers as an example). For the upcoming Mosport Grand Am event we will go through 2 sets of tires and also use a partially used set (from the last race at Lime Rock) early in practice where you're learning the track and don't really need maximum grip. Good grip but not maximum grip. Tire budget per RX8 per Koni race = $2K
Last but not least: A 17" X 9" wheel fits perfect under a lowered RX8. There is GAm rubber that fits this tire. The Koni Challenge rules require the RX8 to run a 225 tire and it fits wonderfully on a 17 x 9.
Wheel purchase cautions: Like many of you, I was into buying the cool wheels. What they don't tell you is the available FAST rubber for those unique size wheels. Do yourself a favor if you plan to do a lot of tracking and look at the rubber availability BEFORE you buy your wheels. You might save yourself some dough. Also, race teams often purchase new wheels at the beginning of the season so contact your favorite GAm RX8 team in October and ask them what parts they have for sale.
Questions?: You can contact me at meyermotorsports@mac.com
Feel free to stop by and sit in our cars at any of the remaining Grand Am Koni Challenge events. I can point the GAm Hoosier tire issues referred to above. Ask any of our crew and they can hunt me down.
Cheers,
Eric
OK guys---here is the real scoop on these tires. It is possible to buy them when they have little to no grip. If you're new to race tires, you won't know this. Race tires have a life to them and it's often (but not always) measured in "heat cycles". We've got less than 10 heat cycles on these tire and then they are no good to us. They might appear fine to someone else, but they are slower and have less grip. Let's define this "heat cycle" thing so everyone knows what I'm talking about. If you're a fast racer and/or you frequently perform a lot of tire data collection, you'll know what I'm talking about. If you don't own a tire pressure gauge then please don't comment on this thread---your just wasting everyone's time and misleading those who need to hear experience talkin'.
One heat cycle is obtained/earned/acheived when you take your car out on a track and raise the tires temperatures to operating range. This is much easier to do on a warm or hot day. Have you ever driven on a road course in winter with little to no grip? That's because you can't get enough heat in your tires to reach their operating range. A tire has a temperature (not pressure) where it works best. A race tire (some people call it an "R" compound) has a higher operating temp that a street or a performance tire. Each time you take your car out on the track, you put a heat cycle on your set of tires. Then your session might be over and you pull into your garage space or parking space or grass or whatever, raise your hood, take a whiz and wait for your next session. Congrats---you just put ONE heat cycle on your tires. Meanwhile your tires, engine and brakes have been cooling off and you're waiting to hit the track again. The next time you roll out, you'll be adding a SECOND heat cycle.
Most race tires have a usable life of XXX heat cycles before they begin to lose their grip and get slower. If you're a serious racer you would know this and could FEEL when the tires no longer have maximum grip. IF YOU ARE NEW TO RACE TIRES OR HAVE NEVER RUN THEM, IT IS POSSIBLE THAT WHEN YOU OBTAIN THESE TIRES THEY HAVE SEVERAL HEAT CYCLES (POSSIBLY TOO MANY HEAT CYCLES) AND/OR HAVE LOST THEIR GRIP. Often people don't know this when you're playing around in the NASA HPDE or similar venues. The difference from these too many heat cycled tires to a fast set can be 2 seconds a lap or more. Often, beginning drivers can't tell this and they think that just because they have "Hoosiers" they are going fast. I see it all the time. A stop watch, lap-timer or data acquistion is the only way to tell if you're going faster---not the type of tire you're using.
So how do you know if the really cool slicks you just bought have any life on them left? First off, the GAm hoosiers have less than 10 heat cycles use out of them (we've found). If you push them hard, they have less that 6. 6 Heat cycles is using the tires 3 times a day for 2 days. Some people get more life out of them, others less. It is possible to get more life out of the tires by running shorter sessions. Heavier cars put more demand on the same size tires than a lighter car does. We typically race for 2.5 hours in Grand Am and after the race we can use the tires for about 2 or 3 practice sessions and they are shot (both in heat cycles and remaining rubber left). Tires wear down. Softer tires (as a general rule) with more grip wear down faster. Often a tire manufacturer will mold in some "wear marks" on the tires that are excellent to use as reference to compare tread wear and determine tire life. Toyo and Hoosier wear marks are little holes about the size of a bb (as in bb gun). Look closely and you'll find them. If a tire is very worn, it's possible that the wear marks are worn out! Gone!
Why am I writing this long email? Because you don't know this stuff until you buy several sets of used tires only to later buy your first set of NEW tires and realize that they are much faster and tons more grip.
For excellent tire wear and very good grip, may I suggest the Toyo RA1 (now called the R888 I believe). When you start it out as a full tread depth rain tire, you'll get 30 plus heat cycles out of them. This is about the most you'll see out of an "R" compound. Faster tires will always offer LESS heat cycles. Think about F1 and NASCAR---a few laps, pit, tire change and the TV closeups show them blistered and shot. These are some really fast tires with a ton of grip----but they don't last long at all. When you have The Toyo's shaved down to 4/32" (this is a common shave for the Toyo), you'll get about 20 heat cycles out of them. 20 FAST heat cycles. This is 3 weekends of really assertive driving. Want to go faster? Shave it to 3/32". Faster yet? 2/32". 2/32" is the fastest but will last about 4-6 cycles before it wears out. I've found the 3/32" to be the fastest at the 3 to 5 heat cycle range. They will last for an entire weekend of Club Racing and be very, very fast.
Summary: Fast rubber cost money. To race with the big boys, plan on spending a grand for a set of tires PER weekend (the GAm Hoosiers as an example). For the upcoming Mosport Grand Am event we will go through 2 sets of tires and also use a partially used set (from the last race at Lime Rock) early in practice where you're learning the track and don't really need maximum grip. Good grip but not maximum grip. Tire budget per RX8 per Koni race = $2K
Last but not least: A 17" X 9" wheel fits perfect under a lowered RX8. There is GAm rubber that fits this tire. The Koni Challenge rules require the RX8 to run a 225 tire and it fits wonderfully on a 17 x 9.
Wheel purchase cautions: Like many of you, I was into buying the cool wheels. What they don't tell you is the available FAST rubber for those unique size wheels. Do yourself a favor if you plan to do a lot of tracking and look at the rubber availability BEFORE you buy your wheels. You might save yourself some dough. Also, race teams often purchase new wheels at the beginning of the season so contact your favorite GAm RX8 team in October and ask them what parts they have for sale.
Questions?: You can contact me at meyermotorsports@mac.com
Feel free to stop by and sit in our cars at any of the remaining Grand Am Koni Challenge events. I can point the GAm Hoosier tire issues referred to above. Ask any of our crew and they can hunt me down.
Cheers,
Eric
06-07-2008, 01:18 PM
#9
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Thanks Eric, I had no idea that you guys were using the tires that long, but does make sense. I still have stock suspension and will finish this TT season stock. I have been going back and forth with getting a set of extra stock rims or some 17's so I may wait until I get the new springs next season, especially if I can't really take advantage if of the 17's with stock springs?
The TOYO's are something I also have not considered, so far looking at different street tires, Z1 star spec, RE01, RT-615 Azenis, and hankook RS2 for the stock rims.
The TOYO's are something I also have not considered, so far looking at different street tires, Z1 star spec, RE01, RT-615 Azenis, and hankook RS2 for the stock rims.
06-07-2008, 06:51 PM
#10
Had a fantastic day. Started with 32psi cold all around as OldDragger suggested, after adjustments the fronts were at about 39 hot and the rears about 37.
Too bad they are forecasting rain for tomorrow, although it will be better for learning
Too bad they are forecasting rain for tomorrow, although it will be better for learning
06-07-2008, 11:09 PM
#11
Sounds good dude. remember also as they wear they are non directional so you can rotate them anyway you like.
thanks Eric for all the info. You are right on. I have always like that work horse tire the ra 1--havent tried the 88 yet. The Hoosier feels faster by a little but the feedback from the ra --to me--is better. Does it sound funny when i say the ra drives heavy?
olddragger
OD
thanks Eric for all the info. You are right on. I have always like that work horse tire the ra 1--havent tried the 88 yet. The Hoosier feels faster by a little but the feedback from the ra --to me--is better. Does it sound funny when i say the ra drives heavy?
olddragger
OD
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