Autocross tire pressure thread
06-08-2014, 04:00 AM
#1
Autocross tire pressure thread
starting this AX tire pressure thread so people have a place to post without running other AX threads off topic ...
Mod Edit:
Copied another post of yours to retain the leading post, and copied the OP text of the thread to this copied post
-RIWWP
Mod Edit:
Copied another post of yours to retain the leading post, and copied the OP text of the thread to this copied post
-RIWWP
Last edited by RIWWP; 06-17-2014 at 10:28 AM.
06-09-2014, 08:15 AM
#2
Autocross tire pressure thread
Gents, since we are on the topic of tires, I do have a question that I could use some assistance on. So now that I am getting more confident in my operating on the track, I have found myself really pushing the limits of the tires.
Yes I am still on the OEM RE050A's
Just trying to get their life's worth before I replace them, but just to be sure that its the tires holding me back and not something else:
Yesterday I had a great day at Thompson raceway. their autocross pad is freshly repaved, and the warm weather made the track nice and sticky. I typically run these tires @ 40psi cold after reading some reviews online. Anyway, after a few confidence building runs, I found myself with some rear chatter as I tried to push out of some turns. I suspected it was the tires rolling over a bit. Bumped up the pressure to 45psi. Reduced chatter, but still couldnt get rid of it.
Am i simply just at the limit for the OEM tires or could I compensate with other means (i.e. alignment?). I am running about -2.75 in the front and a little above -2 in the rear in regards to camber.
Yes I am still on the OEM RE050A's
Just trying to get their life's worth before I replace them, but just to be sure that its the tires holding me back and not something else:Yesterday I had a great day at Thompson raceway. their autocross pad is freshly repaved, and the warm weather made the track nice and sticky. I typically run these tires @ 40psi cold after reading some reviews online. Anyway, after a few confidence building runs, I found myself with some rear chatter as I tried to push out of some turns. I suspected it was the tires rolling over a bit. Bumped up the pressure to 45psi. Reduced chatter, but still couldnt get rid of it.
Am i simply just at the limit for the OEM tires or could I compensate with other means (i.e. alignment?). I am running about -2.75 in the front and a little above -2 in the rear in regards to camber.
06-09-2014, 11:45 AM
#5
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A probe style thermometer is best for tires since the outer layer cools down very quickly. I am a complete ignorant about AutoX setups but, for track duty, 40 psi cold is too high.
06-17-2014, 01:52 PM
#9
34/32 on 255/40/17 Rivals on 17x9. This is is on a low prep STX heavy grand touring. I typically maintain a 2psi split, but bump it up or down depending on the surface or the day. Usually drop rear 1 psi or two for asphalt. I did about the same thing for RS3 as well.
06-18-2014, 02:36 PM
#10
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Howdy,
Just for posterity:
17x8, 245/40-17 Hankook RS3's (version 2 / 2014 builds), 34 psi hot all around.
18x8, 255/35-18 Dunlop z2's, also 34 psi hot all around.
Mark
Just for posterity:
17x8, 245/40-17 Hankook RS3's (version 2 / 2014 builds), 34 psi hot all around.
18x8, 255/35-18 Dunlop z2's, also 34 psi hot all around.
Mark
06-19-2014, 12:24 PM
#11
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To add to the thread:
Not sure on the tire. Inherited with the used car, so just wearing them out. If anyone wants to donate 17X9's and some Rivals, go for it.
Stock car on MS3 rims (18X7.5)
225/45 Sumitomo HTR P01 or Z series @ 40/39
Seems to be the magic pressure for my wear line on the surface/ conditions etc I run in.
*Described painfully for potential new AutoXer's. I don't mean to insult anyone's intelligence*
Best?/ easiest/ cheapest way to track AutoX tire pressure is with chalk or visual inspection of the sidewall. The pressure (esp on an all-season/summer tire) needs to be high enough that the tire wont roll onto the sidewall (sidewall has no grip). The wear line of the tire should stay on the edge of the tread, before the tread meets the sidewall. Some tires have little triangles marking the recommended wear line, others don't.
To track this, simply mark the tires with chalk starting on the top of the tire and onto the sidewall. When you get done with the run, check where the chalk has worn off. I normally start high (42/41 ish) and bleed down to optimal as the tires warm up. Really should only have to do this once anytime you change up tire model to get an idea of what's going on.
I assume your region uses chalk/drywall to mark the cones; just ask someone if you can borrow a chunk to mark your tires.
Even using Michelin HydroEdge tires (800 Treadwear and presumably accordingly soft sidewall) on my fatass mustang my first few AutoXs, I didn't need the pressure any higher than 42/41. Not to say it can't happen, I just think at 45 the tires are bloated and your contact patch will be severely affected for no reason.
Not sure on the tire. Inherited with the used car, so just wearing them out. If anyone wants to donate 17X9's and some Rivals, go for it.
Stock car on MS3 rims (18X7.5)
225/45 Sumitomo HTR P01 or Z series @ 40/39
Seems to be the magic pressure for my wear line on the surface/ conditions etc I run in.
Yesterday I had a great day at Thompson raceway. their autocross pad is freshly repaved, and the warm weather made the track nice and sticky. I typically run these tires @ 40psi cold after reading some reviews online. Anyway, after a few confidence building runs, I found myself with some rear chatter as I tried to push out of some turns. I suspected it was the tires rolling over a bit. Bumped up the pressure to 45psi. Reduced chatter, but still couldnt get rid of it.
Am i simply just at the limit for the OEM tires or could I compensate with other means (i.e. alignment?). I am running about -2.75 in the front and a little above -2 in the rear in regards to camber.
Am i simply just at the limit for the OEM tires or could I compensate with other means (i.e. alignment?). I am running about -2.75 in the front and a little above -2 in the rear in regards to camber.
Best?/ easiest/ cheapest way to track AutoX tire pressure is with chalk or visual inspection of the sidewall. The pressure (esp on an all-season/summer tire) needs to be high enough that the tire wont roll onto the sidewall (sidewall has no grip). The wear line of the tire should stay on the edge of the tread, before the tread meets the sidewall. Some tires have little triangles marking the recommended wear line, others don't.
To track this, simply mark the tires with chalk starting on the top of the tire and onto the sidewall. When you get done with the run, check where the chalk has worn off. I normally start high (42/41 ish) and bleed down to optimal as the tires warm up. Really should only have to do this once anytime you change up tire model to get an idea of what's going on.
I assume your region uses chalk/drywall to mark the cones; just ask someone if you can borrow a chunk to mark your tires.
Even using Michelin HydroEdge tires (800 Treadwear and presumably accordingly soft sidewall) on my fatass mustang my first few AutoXs, I didn't need the pressure any higher than 42/41. Not to say it can't happen, I just think at 45 the tires are bloated and your contact patch will be severely affected for no reason.
Last edited by Mordae; 06-19-2014 at 12:33 PM. Reason: Wording
06-23-2014, 11:43 PM
#12
I think tire pressures are directly related with alignment and setup. I have been attempting to follow the recommendations of the tiger (teamrx8). Sadly these mechanics out here only know how to do alignments on John Deere tractors.
I had weak rear springs forever it and had only -1* Front Camber and -1.8* Rear seems so couldn't get the rear camber less than the front. I was running 36F-34R on my stock rims COLD and they would go to 40F-37R HOT on R1R's and RS-3's both. Hey I was still winning local events.
So here's the deal now. Determined Rear Springs had to be weak as couldn't get less than -2* Camber with new rims +car squatted in *** and couldn't get my jack under the muffler.
I put on 17x9 rims with 245 Dunlops with what appeared to be a decent alignment (NOT) and they went to 44F-39R Hot from 36F-33R Cold. Handled decent. Everyone who counts said I was fast. My fastest run was my first one and then I stayed consistent for 3 more.
I just replaced the rear springs with Factory originals and it pushed up the rear by about 1.5". Which means I now have a level car and can run less camber in the rear than the front for the first time ever. In theory I have -1.6* Front and -1.4* rear camber. Now have 1/4" (.6*) toe out in front and 1/16" (.1*) toe in in the rear. I have koni yellows 1.5 turns (55%) hard in rear and run 1.75 hard in front while racing. Stock everything else so far.
So far the car loves it's 1/2 used Dunlops on 17x9 - 48mm offset Miata STR wheels. I will take it to extensive test and tune this Saturday and have 6 of the best drivers all take one run in it to see what the concenus is?
Something tells me I can hold lower tire pressures with the new camber and toe on the concrete runway. We'll see.
9 drivers over the span of 4 hours. Warm 38F-34R the first five guys raw times were within 1/2 second as temps rose to 39F-35R. Lowered back to 38F-34R but even wetting tires in 100F concrete car slowed by 1/2 second more. Leaving fronts at 39 and Lowering rear psi to 34.5 stabilized the rearend and dropped time back down to the morning times.
I'll report back. Then I'll put the stock 18" rims and Rival's on and do it again on another event and see what it's like.
Put stock wheels back on with 245/40/18 Rivals. Will run again on July 12th same drivers and see what happens to pressures? Used to run 40F-36R hot (34F-32R stone cold) with bad alignment, springs and camber. Had 15 high speed runs with 10 different people with pretty decent cool down times between the runs. About 10 minutes thru out the day and was a sunny 90F FL day. Started runs with 36F-34R on factory rims and 245 Rivals. Tires ran all day at 39F-35R with koni's stiff 2 turns in front for concrete runway. No one off course 52-55 second 3rd gear finish course for the faster drivers. At the end co-driver dropped front 2psi = 37F-35R and he improved .1 second but car felt more neutral to him. The following morning the tires were 32F-31R stone cold. I think I can run even lower pressures in the rear next time as low as 32 hot with my current setup as they still have 1/8" to roll over to the diamonds. I only took two runs so all my observations were from other driver comments. But they were profession comments from winners. A few had issues getting used to the electric power steering is all. No surprise there. Car has more speed in it than I do anymore so it's perfect for me.
My car has never handled this well in the 3 years I've owned it and autocrossed it extensively. I continue to start the day stone cold in the garage 36F-33R no matter what the tire and they all seem to stabilize at 40-37R after a couple runs except Dunlops which run 43F-39R hot. We'll see what the new alignment does.
Hankook's like FL heat wear well. R1R's like a tad of water every 3-4 runs but have funky leading edge rolls. So far Rivals are nuts good and make even old fart look good with crappy alignment. Dunlops are great cold on your first run on a wide rim.
One day I'll try a different front bar? Pressures may change yet again.
My theory is to keep letting air out of the tires as they get higher after each run and they keep coming back up. When they stay the same hot beginning to end of run they are perfect. I let them cool off over night and measure them stone cold. That is where I keep them for the most part as "perfect". When I run a big SCCA event with only 3 runs I start out higher on my first run and keep it there!!
I had weak rear springs forever it and had only -1* Front Camber and -1.8* Rear seems so couldn't get the rear camber less than the front. I was running 36F-34R on my stock rims COLD and they would go to 40F-37R HOT on R1R's and RS-3's both. Hey I was still winning local events.
So here's the deal now. Determined Rear Springs had to be weak as couldn't get less than -2* Camber with new rims +car squatted in *** and couldn't get my jack under the muffler.
I put on 17x9 rims with 245 Dunlops with what appeared to be a decent alignment (NOT) and they went to 44F-39R Hot from 36F-33R Cold. Handled decent. Everyone who counts said I was fast. My fastest run was my first one and then I stayed consistent for 3 more.
I just replaced the rear springs with Factory originals and it pushed up the rear by about 1.5". Which means I now have a level car and can run less camber in the rear than the front for the first time ever. In theory I have -1.6* Front and -1.4* rear camber. Now have 1/4" (.6*) toe out in front and 1/16" (.1*) toe in in the rear. I have koni yellows 1.5 turns (55%) hard in rear and run 1.75 hard in front while racing. Stock everything else so far.
So far the car loves it's 1/2 used Dunlops on 17x9 - 48mm offset Miata STR wheels. I will take it to extensive test and tune this Saturday and have 6 of the best drivers all take one run in it to see what the concenus is?
Something tells me I can hold lower tire pressures with the new camber and toe on the concrete runway. We'll see.
9 drivers over the span of 4 hours. Warm 38F-34R the first five guys raw times were within 1/2 second as temps rose to 39F-35R. Lowered back to 38F-34R but even wetting tires in 100F concrete car slowed by 1/2 second more. Leaving fronts at 39 and Lowering rear psi to 34.5 stabilized the rearend and dropped time back down to the morning times.
I'll report back. Then I'll put the stock 18" rims and Rival's on and do it again on another event and see what it's like.
Put stock wheels back on with 245/40/18 Rivals. Will run again on July 12th same drivers and see what happens to pressures? Used to run 40F-36R hot (34F-32R stone cold) with bad alignment, springs and camber. Had 15 high speed runs with 10 different people with pretty decent cool down times between the runs. About 10 minutes thru out the day and was a sunny 90F FL day. Started runs with 36F-34R on factory rims and 245 Rivals. Tires ran all day at 39F-35R with koni's stiff 2 turns in front for concrete runway. No one off course 52-55 second 3rd gear finish course for the faster drivers. At the end co-driver dropped front 2psi = 37F-35R and he improved .1 second but car felt more neutral to him. The following morning the tires were 32F-31R stone cold. I think I can run even lower pressures in the rear next time as low as 32 hot with my current setup as they still have 1/8" to roll over to the diamonds. I only took two runs so all my observations were from other driver comments. But they were profession comments from winners. A few had issues getting used to the electric power steering is all. No surprise there. Car has more speed in it than I do anymore so it's perfect for me.
My car has never handled this well in the 3 years I've owned it and autocrossed it extensively. I continue to start the day stone cold in the garage 36F-33R no matter what the tire and they all seem to stabilize at 40-37R after a couple runs except Dunlops which run 43F-39R hot. We'll see what the new alignment does.
Hankook's like FL heat wear well. R1R's like a tad of water every 3-4 runs but have funky leading edge rolls. So far Rivals are nuts good and make even old fart look good with crappy alignment. Dunlops are great cold on your first run on a wide rim.
One day I'll try a different front bar? Pressures may change yet again.
My theory is to keep letting air out of the tires as they get higher after each run and they keep coming back up. When they stay the same hot beginning to end of run they are perfect. I let them cool off over night and measure them stone cold. That is where I keep them for the most part as "perfect". When I run a big SCCA event with only 3 runs I start out higher on my first run and keep it there!!
Last edited by twistedwankel; 07-14-2014 at 11:25 AM. Reason: Updated information in colors
07-01-2014, 10:43 AM
#13
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buddies, I used to buy motegi tires 225/45/17. I am constantly having a blown out tire almost every 2-3 months! Sorry. I am a complete noob when it comes to autox and I just learned to ride it like a beginner.
My friends suggested to have 44/45psi front/rear to have a nice control over the wheel. And yeah, I always had a nice control. We constantly check my tire pressure almost every single day during our spare time. We're using Milton analog gauge and Mountain Crest Premium digital tire gauge - this one is a newly established brand as far as I know and bought my gauge through here http://www.amazon.com/Mountain-Crest-Products-Pressure-Accurate/dp/B00GVHFCMW/ie=UTF8?m=ACZYNSNRU07RQ&keywords=Digital+Tire+Gaug e
BUT THEY BOTH HAD DIFFERENT READINGS!
milton measured 44.5 - 46.8psi
mountain crest measured 40 - 40.2psi
I took 3 tests in a row.
Could the pressure be the culprit? We have our own race track from my family and friends' and only a few tiny sharp pebbles. It's impossible they can sh*t a hole on my tube.
Or could there be something else? Is it the tire brand?
My friends suggested to have 44/45psi front/rear to have a nice control over the wheel. And yeah, I always had a nice control. We constantly check my tire pressure almost every single day during our spare time. We're using Milton analog gauge and Mountain Crest Premium digital tire gauge - this one is a newly established brand as far as I know and bought my gauge through here http://www.amazon.com/Mountain-Crest-Products-Pressure-Accurate/dp/B00GVHFCMW/ie=UTF8?m=ACZYNSNRU07RQ&keywords=Digital+Tire+Gaug e
BUT THEY BOTH HAD DIFFERENT READINGS!
milton measured 44.5 - 46.8psi
mountain crest measured 40 - 40.2psi
I took 3 tests in a row.
Could the pressure be the culprit? We have our own race track from my family and friends' and only a few tiny sharp pebbles. It's impossible they can sh*t a hole on my tube.
Or could there be something else? Is it the tire brand?
07-01-2014, 06:26 PM
#14
Not tried this at an AX, but 37 PSI hot front and rear seems to be the sweet spot for me on track. This is on 255/40/17 Direzza Z2, based on tire temp readings after coming off track, and with coilovers and balance adjustments via ride height, alignment and sway bars. I have not had a chance to try this at an AX though.
07-01-2014, 09:11 PM
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225/45/17 Dunlop ZII's on 17 x 8 inch wheels - 35 psi front and 34 psi rear. Chalk indicates that I'm as low as I can go, and temperature readings (measured with a less than ideal IR thermometer) seem to agree. Car is still stock since I'm still undecided on where to start with sway bars.
My fiance runs 41 psi, but her BMW is heavy and the sidewalls on her Continental ExtremeContact DW tires are incredibly soft.
My fiance runs 41 psi, but her BMW is heavy and the sidewalls on her Continental ExtremeContact DW tires are incredibly soft.
07-02-2014, 09:27 AM
#16
buddies, I used to buy motegi tires 225/45/17. I am constantly having a blown out tire almost every 2-3 months! Sorry. I am a complete noob when it comes to autox and I just learned to ride it like a beginner.
My friends suggested to have 44/45psi front/rear to have a nice control over the wheel. And yeah, I always had a nice control. We constantly check my tire pressure almost every single day during our spare time. We're using Milton analog gauge and Mountain Crest Premium digital tire gauge - this one is a newly established brand as far as I know and bought my gauge through here http://www.amazon.com/Mountain-Crest-Products-Pressure-Accurate/dp/B00GVHFCMW/ie=UTF8?m=ACZYNSNRU07RQ&keywords=Digital+Tire+Gaug e
BUT THEY BOTH HAD DIFFERENT READINGS!
milton measured 44.5 - 46.8psi
mountain crest measured 40 - 40.2psi
I took 3 tests in a row.
Could the pressure be the culprit? We have our own race track from my family and friends' and only a few tiny sharp pebbles. It's impossible they can sh*t a hole on my tube.
Or could there be something else? Is it the tire brand?
My friends suggested to have 44/45psi front/rear to have a nice control over the wheel. And yeah, I always had a nice control. We constantly check my tire pressure almost every single day during our spare time. We're using Milton analog gauge and Mountain Crest Premium digital tire gauge - this one is a newly established brand as far as I know and bought my gauge through here http://www.amazon.com/Mountain-Crest-Products-Pressure-Accurate/dp/B00GVHFCMW/ie=UTF8?m=ACZYNSNRU07RQ&keywords=Digital+Tire+Gaug e
BUT THEY BOTH HAD DIFFERENT READINGS!
milton measured 44.5 - 46.8psi
mountain crest measured 40 - 40.2psi
I took 3 tests in a row.
Could the pressure be the culprit? We have our own race track from my family and friends' and only a few tiny sharp pebbles. It's impossible they can sh*t a hole on my tube.
Or could there be something else? Is it the tire brand?
I wonder if there's any connection there?
07-02-2014, 11:41 AM
#18
Get a calibrated mechanical gage from any racing supply house reading up to 60psi.
Sounds like you are running all the time at 45psi hot? That would be a very bad thing. Wearing out the center of the tire. I run 34F-32R stone cold in morning. They heat up to 37F-34R after 20 miles in FL heat. You also said you have access to a racetrack all the time? Tires don't last very long if you track race them every weekend.
You probably also need an alignment really quick. Just go with factory specs until you learn more about your car.
Last edited by twistedwankel; 07-02-2014 at 11:45 AM.
07-07-2014, 02:44 PM
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I am running 245 kumho XS on my STX build. I ran 36 hot on all 4 corners and the car was working very well. I have been autoxing for 10 years, and PSI will very so much brand to brand. You have to do your own testing to know exactly where to run them.
09-08-2014, 08:51 AM
#21
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What Pressure Gauge To Use For This Tire?
Since I am still a little noob about cars and its tools because I only started driving car a few months back. I have encountered several problems in driving which several of my friend says that may be it is due to some pressure differences in my tires. However, I don't what pressure gauge to use. I've looked on amazon of some list of pressure gauges such as Michelin, Accutire, Longacre and Mountain Crest Products premium tire gauge, however, I don't know which one should I choose from them. As for the moment, my option goes to Mountain Crest Products Premium tire gauge since it has the most good reviews. However, I am still unsure whether to buy or not. Do you have something to recommend me?
09-08-2014, 06:36 PM
#22
I think it depends on what you want to spend. Longacre makes good products. I'm not familiar with the others, but I think pretty much any gauge will give accurate results. It's more a question of durability and ease of use. I bought $20 analog gauge from an auto parts store and it consistently matches high end gauges to within <1psi 10 years later.
09-09-2014, 07:09 AM
#23
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Howdy,
I use this gauge:
Joe's Racing Products Tire Guage, Glow in the dark, multiple chucks
Price is right, function is good, etc. Recommended.
Mark
I use this gauge:
Joe's Racing Products Tire Guage, Glow in the dark, multiple chucks
Price is right, function is good, etc. Recommended.
Mark
09-12-2014, 09:52 AM
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I'm no expert, just speaking from my experience. I have found that each tire brand requires different pressures. Years ago I ran the Falken RT615 Azenis, and found the sidewalls very stiff, so they liked 28-30 psi., when I switched to the Bridgestone RE11's the sidewall was so soft I had to run 36 to 38 psi.
09-12-2014, 10:03 AM
#25
we have run a few enduro races 24hrs and 14 hrs we use 215 40 18 dunlop 280 tread compound we always start out around 28 psi once hot you see 32 - 34 psi which i think is too much so after our first stint we lower them back to 28 psi and they usually stay around that for the rest of the event unless we have a stop longer than 15 min.
note when our drivers are on track and the tire pressure got past 30 psi the car lost some grip and would push a little.every car and tire is a bit different and of course weight of your car.but 30 psi seems to be the sweet spot
note when our drivers are on track and the tire pressure got past 30 psi the car lost some grip and would push a little.every car and tire is a bit different and of course weight of your car.but 30 psi seems to be the sweet spot