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| TommyT-Bone | Autocross rant ...... | ||
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Chair-man of the bored
 
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I frequently work the grid at our local autocross venue. Generally we have about 60 participants. In the mix you have cars running bone stock and everything in between to the highly modified. If we are lucky enough to stay green for an extended period of time, it often ends up that the tweakers don't have enough time to dial in their air pressures or get their tires to the optimum temperature. They start falling behind on their runs. I tell them their running out of time. They tell me it's not their fault. My feeling is if you can only get two or three runs in when everybody else is getting four that it is your fault. I see drivers who are scrambling in, soaking their tires while the course workers patiently wait for them to complete their runs because the rest of the field is finished. Luckily, the timing crew will usually tell the starter to close the line and the driver has to finish their runs in the next run group. That's all well and good but usually means that driver can't fulfil his part in course work. In our autocross sessions you have to work if you want to drive. Fair is fair. Eventually, at the end of the day, guess who is holding up everybody from picking up and going home. You got it, Mr missing a little something.
This brought me to ask this question. I asked two National Champions about all these tire adjustments and cooling of their tires. They both told me it's the latest trend but they can't figure if all this is helping all that much. Sure tire pressure is important but where are they getting the imput for the tire temp. From the individual tire manufacturers? Neither of these guys cool their tires but they both will make air pressure adjustments as needed. That I understand. This led me to ask them a second question. Why in drag racing do you want to heat up your tires for grip but in autocross they are trying to cool their tires? Both of them gave me an I don't know look and answer. One even thought that wetting the tires may possibly reduce grip. Old school, new school .... What's your take? Wet or dry. hot or cold? Or maybe you just don't give a f... |
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Posted on: 2010/6/14 11:48
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| 383tpimachine | Re: Autocross rant ...... | ||
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Master Guru
 
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dry is always better
hot vs dry depends on the tires i believe sgtreet tires need to stay colder than say hoosier A6 or R6s |
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Posted on: 2010/6/14 13:09
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
 
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Kudos for working the grid.
Waiting for someone to pull off the grid because they were wetting tires is BS and letting them run in the next group shouldn't even happen. It takes one minute to adjust pressure in 4 tires and get back in the car. Anything else (soaking) should be done by someone besides the driver, crew, friend other driver. If they ain't ready, they don't go. In road racing, if you aren't on pre-grid when the 5 minute sign goes up, you loose your qualifying position and have to start in the back. Input for tire temps.- You can get a baseline from the Mfg's but the variables (chassis setup, track surface temp,etc) make a difference. The only good way to know the best temps is from experience and data. I have temp/pressure sheets that I made. I have them for different tracks and keep them in a logbook for reference (you can't go out at Laguna on a cold morning and remember what pressure you started at last year). Drag racing's a different deal, the tires are at ambient and need heat put in them to get to the optimum starting temp for grip (varies wildly depending on the specific tire). Time in between runs is way longer than in an autox and the tires return to ambient temp. Cooling the tires - depends on temps. Tires are severely abused in one run and the temps go up fast. It's really the temps and press that should determine if they need cooled or a press adjustment. I would imagine that your champs are doing their adjustments by the way the tires felt on the last run and by their experience from 1,000's of runs. The best way is to take tire temps looking for even temps across the tire (taking into account camber heatup of one edge of the tire). IR guns are better than nothing, probe temp gages are much better since the tire surface cools very fast. Cold tire starting press is iffy unless you use nitrogen. You can't be sure of the moisture content in compressed air. And moisture content is determines the pressure build up. Also, is you're sitting with one side of the car in the sun, the temp difference right to left can be a lot. Many guys use tire covers. |
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Posted on: 2010/6/14 13:42
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| bogus | Re: Autocross rant ...... | ||
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Grand Imperial Pooh-Bah
 
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Always had the same problem with RC Car racers...
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Posted on: 2010/6/14 14:15
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| BrianCunningham | Re: Autocross rant ...... | ||
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Senior Guru
 
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overheat a tire and they'll get greasy
all that should be done the second they park the car from the last run how much time between runs? |
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Posted on: 2010/6/14 14:58
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| SpectatorRacing | Re: Autocross rant ...... | ||
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Elite Guru
 
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Cooling the tires seems very strange. Each tire has a specific temperature range in which it performs best. For example, the A6 383tpi mentioned works best over 150* F. They come off of the track (open track, not Auto-x) around 180* if properly set up. They cool down so fast that if you're not probing them in the pits you're wasting your time - by the time you're back to your paddock you've lost 20*.
I can't see how they would get overheated in a 30 sec Auto-x run, but I have never done it so anyone with experience can tell me I'm wrong and I'll concede. Manufacturer recommendations for pressure, etc. are not that useful, they're usually for longevity and CYA rather than speed. The guys with big tire budgets run Hoosiers at 20 psi (hoosier recommends 40 psi hot), they stick great but are destroyed after a session. Like Bill says, there are probably a lot of guys taking temps with a laser. Not only is it useless they probably have no idea what to do with the information once they have it... Sounds like your experts don't bother, these are the guys I'd believe...the ones with trophies. |
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Posted on: 2010/6/14 15:06
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| SpectatorRacing | Re: Autocross rant ...... | ||
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Elite Guru
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I hope this catches on, I can't wait to see my opponent wetting his tires before my next race...
But again, Auto-x could be different. |
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Posted on: 2010/6/14 15:09
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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I see more guys spraying intercoolers than tires at our AutoX.
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Posted on: 2010/6/14 15:12
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Quote:
I don't wet mine but, I do roll it out from under the EasyUp a half hour before the race. Helps that it's an open wheel  to get sun on the tires. |
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Posted on: 2010/6/14 15:14
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| SpectatorRacing | Re: Autocross rant ...... | ||
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Elite Guru
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They probably read it on the internet from some dumbass like me or you
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Posted on: 2010/6/14 15:54
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| TommyT-Bone | Re: Autocross rant ...... | ||
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Chair-man of the bored
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Quote:
Average say 5 minutes. But when your behind on your runs you can end up going back to back. I posted up at grid in my run group yesterday before some of my group even had brought their cars up. I did 4 back to back runs but I'll admit by my fourth run the tires were pretty slippery. I run street high performance Falkans. I have street hp Sumis on my wifes car. I know we could pick up a few seconds easy running R compounds but I'm a lazy SOB and don't want to make a mission out of autocross. We just basically arrive and drive. |
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Posted on: 2010/6/14 16:18
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| TommyT-Bone | Re: Autocross rant ...... | ||
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Chair-man of the bored
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Bill, I usually work the grid or start. You have to have a knack for it and I like it. My wife usually works at timing or making sure everybody signs a waiver and has a wrist band and other front line stuff. Keeping the groups moving is important to a successful event. Yesterday was kind of rough. A Legend Car took out the start timer and there were several other timer/course delays during the day. Everybody still got in 8 runs. 4 in the morning and 4 in the afternoon. Top time was about 54 seconds. Our courses average 5 to 7 tenths of a mile. Lots of turns, a couple of slaloms and always lots of fun.
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Posted on: 2010/6/14 16:33
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Yea, the heat will build up because there's not a lot of cool down time between runs. Hopefully you have a good tire gauge and use it. |
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Posted on: 2010/6/14 16:51
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Yea, when I'm not racing, I'm working. 2 weekends ago, I left for the track at 6:15. At 7:15 I started tech inspections, had to do 30 myself. And trying to get them done fast especially for the first group that was on track at 9:00. At 9:30, I was incar for the first of 5, 30 minute instruction sessions. Got home at 7:00 p.m. exhausted. |
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Posted on: 2010/6/14 16:56
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| CentralCoaster | Re: Autocross rant ...... | ||
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Senior Guru
 
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I don't give a f____. If these asshats spent as much time improving their driving as they did trying to copy some idea they heard on the internet that would improve their lap times..... they might win every once in awhile. They shouldn't be accommodated if they're holding things up.
With that said, street tires can overheat in an autoX and affect you in subsequent rounds. I'm guessing they wet them to cool them off? |
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Posted on: 2010/6/15 2:08
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| shakedown067 | Re: Autocross rant ...... | ||
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Senior Guru
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If they don't get their runs in...then they don't get to run. Plain and simple. It also shouldn't take that much time in-between runs. I also agree with the comments above that you should only adjust air temp yourself. Anything else, you should have a friend or a driver that's not running or working do any other adjustments.
For me, street tires shouldn't really be adjusted much if you want to save your tires. I ran nitrogen in my street tires when I ran them. So I set them and forgot them as they where set for minimum tire wear vs max grip. My 710's I usually only have to adjust after my second run and there is normally enough time between runs that they stay a constant pressure. |
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Posted on: 2010/6/23 21:48
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| Steve40th | Re: Autocross rant ...... | ||
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Elite Guru
 
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Not to high jack, but if you filled your 710's tires with Nitrogen, you wouldnt need to readjust, correct. I didnt read this on the internet, btw ;) |
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Posted on: 2010/6/23 22:14
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| CentralCoaster | Re: Autocross rant ...... | ||
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Senior Guru
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Nitrogen increases pressure with temperature just like any other gas.
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Posted on: 2010/6/24 6:56
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Quote:
Yea. really. Nitrogen must be one of the top Internet myths (well at least the most misunderstood). What Kevin said- the pressure does increase. Moisture content in the air is the main reason for higher pressure increases. Nitrogen is dryer that the air everyone uses only because it comes out of a plant that controls this unlike the air guys use from a crappy home/garage/racetrack compressor that hasn't been drained in months and has no moisture filter. Nitrogen's used ONLY because the temp rise is predictable. |
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Posted on: 2010/6/24 13:43
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| Steve40th | Re: Autocross rant ...... | ||
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Elite Guru
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I saw this when I was watching a CART race years ago, and they were talking about how they used Nitrogen in their tires to keep the tires pressure stable, due to being inert gas. And this was before Al Gore invented the internet |
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Posted on: 2010/6/24 13:51
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Quote:
I've been using Nitrogen about that long. Using air in the slicks on an open wheel lower downforce car (compared to an indy car) can have a pressure increase of anywhere from 3 to 8 psi (going from ambient to about 180 degrees tire temp). That's a boatload on tires that start out at 15 psi. and can really screw up the race. With nitrogen the temp rise is in the 2-3 lb. range all the time. Al Gore is an inert gas.  |
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Posted on: 2010/6/24 14:09
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| CentralCoaster | Re: Autocross rant ...... | ||
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Senior Guru
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I use only Hydrogen gas in my tires, for weight reduction.
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Posted on: 2010/6/25 0:36
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| shakedown067 | Re: Autocross rant ...... | ||
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Quote:
I never saw any noticeable gain in pressure in my street tires, but the place that mounted my track tires doesn't currently run nitrogen. They did it so cheap, I didn't feel like pay the extra rip off $50 to have the slicks refilled with nitrogen else where, when I can just adjust once at the track and be happy. I use nitrogen in my street tires for the reliable pressures, not concerned with pressure increases or not. Since they are run flats, any major decrease means I've got issues (my sensors have gone out) and was the big factor for my DD tires. |
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Posted on: 2010/6/25 1:33
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| TommyT-Bone | Re: Autocross rant ...... | ||
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Chair-man of the bored
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I am currently running this formulation primarily due to it's easy access.
Nitrogen -- N2 -- 78.084% Oxygen -- O2 -- 20.9476% Argon -- Ar -- 0.934% Carbon Dioxide -- CO2 -- 0.0314% Neon -- Ne -- 0.001818% Methane -- CH4 -- 0.0002% Helium -- He -- 0.000524% That's an approximate breakdown of what my air pump is putting in my tires. So I guess I'm running almost 80% nitrogen. |
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Posted on: 2010/6/25 2:20
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| BillH | Re: Autocross rant ...... | ||
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The Stig Moderator
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Which means your tires have a bunch of H2O in them.  |
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Posted on: 2010/6/25 2:29
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