Tirelief - anyone use these?
02-03-2005, 10:17 PM
#16
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Well I personally use them, and have been for five years in late model stock car racing, and several Porsche race cars and DE cars. To put it simply, they work very well.
The obvious benefit is that you inflate your tires to your target hot pressure before hitting the track, and they never go over that setting. They are very simple devices that consist of a housing containing a seat that is held in place with a spring that is adjusted via a threaded cap and lock ring, within a range, in infinite setting. The kits stipulate a range of 2-38 psi I think, but I have found that a setting of 44 psi is possible, and that there is more preload available.
There are two ways to mount them. They have adapters that mount in the existing valve holes, into which the tirereliefs are mounted, or you can drill and tap a hole in a different location. I personally have drill mounted them on Kinesis wheel halves, Fuchs wheels and untold other steel stock car wheels.
They do take some time to set up, a set and test cycle where you screw the cap down to a certain point, inflate the tire until you hear the air bleeding, let them bleed off for a few hours, and check the tire pressure. If you want higher pressure, you tighten the cap a little and re-inflate the tire again, or loosen it for less pressure and so on. Once they are set, they are very accurate, in my experience to within 1/2 psi. Once set, they don't need adjustment, unless you want a different pressure.
A major side benefit to the consistent handling that I noticed was that my tire life virtually doubled at least. I attribute this to the fact that the contact patch is always nearly optimal. Rather than running with the contact patch in a compromised state 2/3rds of the time, as when underinflated on out laps, to overinflated towards the end of the run, and close to correct in the middle, the contact patch is always optimized because the pressure is consistent. I have backed this up with diligent probe type tire pyrometer data collection.
Having a tire at your target pressure is particularly important in oval racing with tube frame cars running bias construction tires. Because of the stiffness of the chassis, and the way that bias tires grow in circumference with pressure and heat, the handling can and will vary dramatically.
As an example, when setting up your typical roundy-round car, a person is looking for a specific cross weight percentage to determine the chassis balance. This crossweight percentage is highly dependant upon tire size and pressure. A change of .5, or 1/2% makes a noticable difference in the handling. If while on scales I was to change the tire pressure in one tire by one psi, the crossweight will change 1%. This is why stock car tires are mounted dry, and everyone uses nitrogen. Even then, the tires will grow and average of 10-12 psi, which wreaks havoc on the balance as you may imagine, unless the chassis setup is perfectly balanced so that all the tires grow consistently. This usually doesn't happen of course, and you chase the handling all over the place.
Now, in cars that have tires with very short sidewalls, like all our Porsches, the tire guys have to use plenty of spooge to get the thing on the wheel. This leaves plenty of moisture inside the tire, making nitrogen use not terribly effective. On my 930, the rear 315's used to grow by 15 psi at least in 30 minutes. On the track here in Seattle, the surface is so bad, that I could kill a right rear tire in four heat cycles. After mounting the tire reliefs, I started getting 12-15 heat cycles.
Anyway, my experience has been that these bleeders are very effective and simple devices that are not subject to sudden catastophic failure, any more so than any other mechanical device on a track driven car. It's easy enough to put your fingers on them when checking your pressure to make sure the caps are tight, other than that there's not much to them.
The only drawback that has been previously mentioned, is that in a setting where you're going out and coming in, maybe letting the car sit like at a DE, you need to top off the pressure before heading out again. Lastly, you need a flat spot on the wheel to mount them wide enough to seal the o-ring, that does not put them directly over the bead of the tire. On some high offset wheels, this can be a challenge.
The obvious benefit is that you inflate your tires to your target hot pressure before hitting the track, and they never go over that setting. They are very simple devices that consist of a housing containing a seat that is held in place with a spring that is adjusted via a threaded cap and lock ring, within a range, in infinite setting. The kits stipulate a range of 2-38 psi I think, but I have found that a setting of 44 psi is possible, and that there is more preload available.
There are two ways to mount them. They have adapters that mount in the existing valve holes, into which the tirereliefs are mounted, or you can drill and tap a hole in a different location. I personally have drill mounted them on Kinesis wheel halves, Fuchs wheels and untold other steel stock car wheels.
They do take some time to set up, a set and test cycle where you screw the cap down to a certain point, inflate the tire until you hear the air bleeding, let them bleed off for a few hours, and check the tire pressure. If you want higher pressure, you tighten the cap a little and re-inflate the tire again, or loosen it for less pressure and so on. Once they are set, they are very accurate, in my experience to within 1/2 psi. Once set, they don't need adjustment, unless you want a different pressure.
A major side benefit to the consistent handling that I noticed was that my tire life virtually doubled at least. I attribute this to the fact that the contact patch is always nearly optimal. Rather than running with the contact patch in a compromised state 2/3rds of the time, as when underinflated on out laps, to overinflated towards the end of the run, and close to correct in the middle, the contact patch is always optimized because the pressure is consistent. I have backed this up with diligent probe type tire pyrometer data collection.
Having a tire at your target pressure is particularly important in oval racing with tube frame cars running bias construction tires. Because of the stiffness of the chassis, and the way that bias tires grow in circumference with pressure and heat, the handling can and will vary dramatically.
As an example, when setting up your typical roundy-round car, a person is looking for a specific cross weight percentage to determine the chassis balance. This crossweight percentage is highly dependant upon tire size and pressure. A change of .5, or 1/2% makes a noticable difference in the handling. If while on scales I was to change the tire pressure in one tire by one psi, the crossweight will change 1%. This is why stock car tires are mounted dry, and everyone uses nitrogen. Even then, the tires will grow and average of 10-12 psi, which wreaks havoc on the balance as you may imagine, unless the chassis setup is perfectly balanced so that all the tires grow consistently. This usually doesn't happen of course, and you chase the handling all over the place.
Now, in cars that have tires with very short sidewalls, like all our Porsches, the tire guys have to use plenty of spooge to get the thing on the wheel. This leaves plenty of moisture inside the tire, making nitrogen use not terribly effective. On my 930, the rear 315's used to grow by 15 psi at least in 30 minutes. On the track here in Seattle, the surface is so bad, that I could kill a right rear tire in four heat cycles. After mounting the tire reliefs, I started getting 12-15 heat cycles.
Anyway, my experience has been that these bleeders are very effective and simple devices that are not subject to sudden catastophic failure, any more so than any other mechanical device on a track driven car. It's easy enough to put your fingers on them when checking your pressure to make sure the caps are tight, other than that there's not much to them.
The only drawback that has been previously mentioned, is that in a setting where you're going out and coming in, maybe letting the car sit like at a DE, you need to top off the pressure before heading out again. Lastly, you need a flat spot on the wheel to mount them wide enough to seal the o-ring, that does not put them directly over the bead of the tire. On some high offset wheels, this can be a challenge.
02-04-2005, 03:42 PM
#17
Rennlist Member
Thanks for the detailed testimonial Randy. I have wondered about these things ever since reading in "Tune to Win" where Carroll Smith says something to the effect that Circle track guys have used them for years and road racers should too... Every time I see them in a racing catalog, I pause, but never wanted to be the first guy I know to take a drill to a Fuchs or Kinesis wheel...
02-04-2005, 03:58 PM
#18
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As I mentioned, they make adapters that mount in the current valve stem holes. The tirerelief than can be screwed into the adapters. The compromise is that you have to remove the tirereliefs and screw in a valve stem adapter to inflate the tire. The valve hole adapter has a one-way valve so no air escapes. It seems like it would be a pain, but it's one way to avoid drilling a hole. FWIW, the Fuchs material thickness is just right to tap the hole and mount them using a 1/8 N.P.T. tap.
02-09-2005, 12:48 PM
#22
Drifting
I was talking to a friend of mine who tried them out on a couple 996 cup cars. He said they could never get them set up so they would work consistently. He thought the problem was caused by the wheels getting too hot during the session, heating up the spring in the valve, and changing the spring rate. That was his experience anyway. You probably wouldn't have this problem on an oval (where a lot of people run them) because you aren't on the brakes as much. It seems like people either love Tirelief or hate them..
02-10-2005, 10:44 AM
#24
A friend and I is building a NASA Honda Challenge Integra.
We bought a set of Kosei wheels with two bleed valves on each wheel. The design for the two valves system is to facilitate the use of nitrogen gas by filling the gas in one valve and extracting existing air from the other.
I wonder if the bleed valves would fit one of the valve in the wheel?
Kam
We bought a set of Kosei wheels with two bleed valves on each wheel. The design for the two valves system is to facilitate the use of nitrogen gas by filling the gas in one valve and extracting existing air from the other.
I wonder if the bleed valves would fit one of the valve in the wheel?
Kam
02-10-2005, 02:31 PM
#25
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To answer a couple of comments.
It's very true that the tirereliefs are very time consuming to set up properly. My experience has been that it takes 15-20 cycles of inflating the tire, adjusting the spring preload by tightening or loosening the cap, letting them bleed down for at least an hour so you get an accurate picture of where they're set, and repeat. It takes a few days. Perhaps the setup issues arise out of lack of patience.
Saturday night short track racers use their brakes moderately hard twice a lap, at anywhere from 5 second to 20 second intervals. The theory of heat buildup in a road racing car being more of an issue relative to stock cars doesn't pencil out to me.
The tirereliefs are very susceptible to debris getting under the seat and leaking, so it's important to ensure that the tires being mounted don't have any dirt or whatever inside them before mounting, since this debris will naturally vent out the tirerelief valve and muck things up. I have experienced this and the solution is to simply take the cap off and spring and seat and clean them out. Of course now you have to go through the set up again. Longacre sells caps that can be placed over the valve when washing things to help keep things out under these circumstances too.
It does on the face of it seem strange to use a device that has an accuracy range greater than the margin of pressure that teams are seeking. The deal is, the tirereliefs are a tool that eliminates a great deal of tire guesswork.
In stock car racing where chassis setups are incredibly sensitive to change, most local series use bias ply slicks. These tires, even with nitrogen will grow up to 20 psi, or more, in a 50 lap race on a 1/4 to 1/2 mile oval. This, in and of itself, isn't a big deal. The real issue is that these tires grow in circumference more than most road racers are aware of. Tire stagger is a tool used in oval racing where the outside tires are larger than the inside tires, to help eliminate scrub in the corner. Picture a pencil with two cucumber slices, one larger than the other. Give it a push and it will naturally roll in an arc. The radius of the arc is dependant upon the difference in the circumference of the cucumber slices.
When a guy goes out and buys tires for the weekend's race, there are measurements marked on the tire indicating what the circumference was when it came out of the mold. Our tires tend to run in a range from 82 inches to 88 inches circumference or rollout. This is for left side tires and right sides. Each side's tires can vary by as much as 5 inches, so picking a set of tires that has the stagger range you're looking for, and predicting how much they'll change with heat and load is a expertise in and of it's own. Once they're mounted, you will inflate them to your target hot pressure and measure. Sometimes it takes a dozen different tires in one position to achieve the stagger. This is even before they turn a wheel on the track. The tire's behavior on the race car, on the track, is influenced by many variables as you may imagine, obvious things being ambient air temperature, relative humidity, whether it's sunny or overcast, if your alignment settings are good, the line you'll be running most, and on and on. The other thing most road racers aren't aware of is how jacked up a roundy-round car chassis is to make it go left as well as possible. As an example, on a 3/8 mile low bank oval around here, on my car which weights 2900 lbs, I run a 375lb spring in the RF, a 350 in the LF, a 200 in the LR and a 175 in the RR. That's not a typo, that's a 175lb spring on the right rear of a 650 hp, 2900 lb car. The corner weights are also not what you would think. The diagonal from RF to LR carries 57% of the weight, and the left side weight is 58%. The rear end has approximately 1000 lbs on the LR and 450lbs on the RR.
The point of all this is that predicting how much a tire will grow is extremely difficult because of the vastly different loads. If your set up is "balanced" things will all be even, including tire temps. So if you start out at 8 psi cold on the left side tires and 12 psi on the right, you might hit your target of 20/30, or you might miss it by a lot. Meantime, as the tires are heating up, imagine how much the handling is changing. Not only that, but imagine going sailing off down the frontstretch on the green flag, into the first corner within inches of dozens of other cars at high speed with only 8 and 12 psi in your tires. It's a pucker.
As was mentioned earlier, the tirereliefs allow you to set your cold pressure at your target hot pressure and go. Sure, they may cycle around a little, and end up being from 1/2-2 psi off of your target, but that sure beats missing it by 10 psi. Especially when it's only one corner that's really off and your handling has gone completely out the window.
Personally I find them to be incredibly effective and as a bonus my tire life has increased measurably. They take some set up and maintenance of course, but what doesn't?
I have a pal getting some of those Kosei wheels with the two valve holes and we'll be mounting tirereliefs in one of those. The tirereliefs have a threaded nipple that's 1/8 N.P.T. thread, so you'll need a suitable drill bit and tap. In the case where the material thickness of the wheel is too thin to support mounting by tapping threads, like steel stock car wheels, they have a back up nuts that mount inside the wheel. The key is that it needs to be done with the tires dismounted.
It takes some committment to drill a hole in a wheel, but if done correctly it's not terribly technically demanding. I was concerned that the value of the wheel would be destroyed, but since I can get twice as much tire life, I could afford to buy a new set of wheels with the tire savings after a little while.
Anyway, that's what I have found, your experience may vary.....
It's very true that the tirereliefs are very time consuming to set up properly. My experience has been that it takes 15-20 cycles of inflating the tire, adjusting the spring preload by tightening or loosening the cap, letting them bleed down for at least an hour so you get an accurate picture of where they're set, and repeat. It takes a few days. Perhaps the setup issues arise out of lack of patience.
Saturday night short track racers use their brakes moderately hard twice a lap, at anywhere from 5 second to 20 second intervals. The theory of heat buildup in a road racing car being more of an issue relative to stock cars doesn't pencil out to me.
The tirereliefs are very susceptible to debris getting under the seat and leaking, so it's important to ensure that the tires being mounted don't have any dirt or whatever inside them before mounting, since this debris will naturally vent out the tirerelief valve and muck things up. I have experienced this and the solution is to simply take the cap off and spring and seat and clean them out. Of course now you have to go through the set up again. Longacre sells caps that can be placed over the valve when washing things to help keep things out under these circumstances too.
It does on the face of it seem strange to use a device that has an accuracy range greater than the margin of pressure that teams are seeking. The deal is, the tirereliefs are a tool that eliminates a great deal of tire guesswork.
In stock car racing where chassis setups are incredibly sensitive to change, most local series use bias ply slicks. These tires, even with nitrogen will grow up to 20 psi, or more, in a 50 lap race on a 1/4 to 1/2 mile oval. This, in and of itself, isn't a big deal. The real issue is that these tires grow in circumference more than most road racers are aware of. Tire stagger is a tool used in oval racing where the outside tires are larger than the inside tires, to help eliminate scrub in the corner. Picture a pencil with two cucumber slices, one larger than the other. Give it a push and it will naturally roll in an arc. The radius of the arc is dependant upon the difference in the circumference of the cucumber slices.
When a guy goes out and buys tires for the weekend's race, there are measurements marked on the tire indicating what the circumference was when it came out of the mold. Our tires tend to run in a range from 82 inches to 88 inches circumference or rollout. This is for left side tires and right sides. Each side's tires can vary by as much as 5 inches, so picking a set of tires that has the stagger range you're looking for, and predicting how much they'll change with heat and load is a expertise in and of it's own. Once they're mounted, you will inflate them to your target hot pressure and measure. Sometimes it takes a dozen different tires in one position to achieve the stagger. This is even before they turn a wheel on the track. The tire's behavior on the race car, on the track, is influenced by many variables as you may imagine, obvious things being ambient air temperature, relative humidity, whether it's sunny or overcast, if your alignment settings are good, the line you'll be running most, and on and on. The other thing most road racers aren't aware of is how jacked up a roundy-round car chassis is to make it go left as well as possible. As an example, on a 3/8 mile low bank oval around here, on my car which weights 2900 lbs, I run a 375lb spring in the RF, a 350 in the LF, a 200 in the LR and a 175 in the RR. That's not a typo, that's a 175lb spring on the right rear of a 650 hp, 2900 lb car. The corner weights are also not what you would think. The diagonal from RF to LR carries 57% of the weight, and the left side weight is 58%. The rear end has approximately 1000 lbs on the LR and 450lbs on the RR.
The point of all this is that predicting how much a tire will grow is extremely difficult because of the vastly different loads. If your set up is "balanced" things will all be even, including tire temps. So if you start out at 8 psi cold on the left side tires and 12 psi on the right, you might hit your target of 20/30, or you might miss it by a lot. Meantime, as the tires are heating up, imagine how much the handling is changing. Not only that, but imagine going sailing off down the frontstretch on the green flag, into the first corner within inches of dozens of other cars at high speed with only 8 and 12 psi in your tires. It's a pucker.
As was mentioned earlier, the tirereliefs allow you to set your cold pressure at your target hot pressure and go. Sure, they may cycle around a little, and end up being from 1/2-2 psi off of your target, but that sure beats missing it by 10 psi. Especially when it's only one corner that's really off and your handling has gone completely out the window.
Personally I find them to be incredibly effective and as a bonus my tire life has increased measurably. They take some set up and maintenance of course, but what doesn't?
I have a pal getting some of those Kosei wheels with the two valve holes and we'll be mounting tirereliefs in one of those. The tirereliefs have a threaded nipple that's 1/8 N.P.T. thread, so you'll need a suitable drill bit and tap. In the case where the material thickness of the wheel is too thin to support mounting by tapping threads, like steel stock car wheels, they have a back up nuts that mount inside the wheel. The key is that it needs to be done with the tires dismounted.
It takes some committment to drill a hole in a wheel, but if done correctly it's not terribly technically demanding. I was concerned that the value of the wheel would be destroyed, but since I can get twice as much tire life, I could afford to buy a new set of wheels with the tire savings after a little while.
Anyway, that's what I have found, your experience may vary.....
Last edited by Randy; 02-11-2005 at 02:37 AM.
02-10-2005, 05:32 PM
#27
Burning Brakes
There are many of us who use tire pressures, in combination with a pyrometer, as a 'tuning device'. Different tracks, and different conditions as temps rise and fall on those tracks, required diddling all weekend to achieve the results we want.
In those situations, tire pressure relief valves are a hindrance.
If you're missing hot pressures by 10 lbs, that's just negligence.
In those situations, tire pressure relief valves are a hindrance.
If you're missing hot pressures by 10 lbs, that's just negligence.
02-10-2005, 08:34 PM
#28
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First of all, I'm not suggesting that tirereliefs are a good substitute for proper chassis set up, or tire management. They do have other advantages though, that make them valuable as I have articulated previously.
It's obvious that using tire pressures for tuning the balance, if that's what you like to do, will require a range of pressures, something tirereliefs cannot accomodate.
Of course, using tire pressures is a shortcut, and a rather unsophisticated method to tune the balance, rather than more appropriately changing your alignment settings, spring rates, shock valving, sway bars settings etc....to get the balance you're seeking.
It is a valid strategy under limited circumstances, like pit stops where there is little time to make substantive chassis adjustments, but you just end up with a tire that has it's contact patch and performance compromised in the name of chassis balance.
Pyrometers are great for gathering data about the temperature of the contact patch, but what does it mean? The data isn't as simple to interpret as it seems. Is the ouside hot because there is too little camber or too much toe-in, or is the pressure low? Is the inside hot because there is too much camber or toe out, is the tire pressure too high or did you just come in from a long acceleration or braking event? Are the results skewed because I headed out with the tires low, and now they're too high?
Why not try to remove one of the variables from the equation? Trying to predict pressure build under varying track and environmental conditions is very difficult. Why accept the compromised performance of a tire while it's cold and under-inflated? Why not take advantage of the better handling and tire life benefits of having the contact patch optimized from track out?
If a person is an expert at predicting the pressure build of a given tire under whatever circumstances, my hat's off to them, but they still accept the compromise in performance until the tire is at the correct pressure. Tirereliefs make this expertise and guesswork largely unnecessary.
If you don't like them fine, don't use them. I'll be able to concentrate on chassis settings for balance, just walk away in the first few laps, and have a tire budget that's half as much.
Of course I'm no expert. This is all my experience and opinion, your results may vary.
It's obvious that using tire pressures for tuning the balance, if that's what you like to do, will require a range of pressures, something tirereliefs cannot accomodate.
Of course, using tire pressures is a shortcut, and a rather unsophisticated method to tune the balance, rather than more appropriately changing your alignment settings, spring rates, shock valving, sway bars settings etc....to get the balance you're seeking.
It is a valid strategy under limited circumstances, like pit stops where there is little time to make substantive chassis adjustments, but you just end up with a tire that has it's contact patch and performance compromised in the name of chassis balance.
Pyrometers are great for gathering data about the temperature of the contact patch, but what does it mean? The data isn't as simple to interpret as it seems. Is the ouside hot because there is too little camber or too much toe-in, or is the pressure low? Is the inside hot because there is too much camber or toe out, is the tire pressure too high or did you just come in from a long acceleration or braking event? Are the results skewed because I headed out with the tires low, and now they're too high?
Why not try to remove one of the variables from the equation? Trying to predict pressure build under varying track and environmental conditions is very difficult. Why accept the compromised performance of a tire while it's cold and under-inflated? Why not take advantage of the better handling and tire life benefits of having the contact patch optimized from track out?
If a person is an expert at predicting the pressure build of a given tire under whatever circumstances, my hat's off to them, but they still accept the compromise in performance until the tire is at the correct pressure. Tirereliefs make this expertise and guesswork largely unnecessary.
If you don't like them fine, don't use them. I'll be able to concentrate on chassis settings for balance, just walk away in the first few laps, and have a tire budget that's half as much.
Of course I'm no expert. This is all my experience and opinion, your results may vary.
Last edited by Randy; 02-11-2005 at 02:39 AM.
02-11-2005, 09:40 AM
#30
Burning Brakes
Originally Posted by Randy
Of course I'm no expert. This is all my experience and opinion, your results may vary.
Is it significant that they are virtually unseen on roadcourse wheels at pro and club races in the US ?