Hi Guys,
I'm after some tips on what pressures to run on the track, and how to know whether they need to be higher or lower...
I run in supersprints on Toyo Proxes RA1's - 205/50/15's
I used to run them at around 40psi hot (when I did the Peter Finaly course, we were told to inflate our tyres to 40psi, which I then assumed was the norm for the track...), but with some experimenting I found that they were grippier a bit lower.
Down at wakefield earlier in the month I ran them at 36psi hot - & I got tyre squeel, which I had never experienced before on these tyres...? (hear for yourself) Wakefield lap
At Eastern creek last weekend I ran them at 34psi hot, but noticed when I took the tyres off that there was a lot of rubber build up on the tyres around the tread edges (rubber worms)... not sure if this was caused by the tyre pressure, or the drive home from the circuit (car is usually trailered)
So how do you read a tyre? what are the signs of too high & too low?
PS. I usually start the tyres anywhere between 28-32psi and then test them after the first run (as soon as I get out of the car, and the tyres are hot) to get them balanced, and then again after the next few runs
Tyre Pressures
Started by
_jklumpp_
, Aug 27 2009 09:01 AM
23 replies to this topic
#2
_rorym_
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Posted 27 August 2009 - 05:32 PM
Interesting question...
82911/Greg used to run very low pressures to start on his old NC LJ XU1 for the circuit stuff ..22 off mermory then lets them heat up...on bikes the optimum was 36 front and 42 rear hot..we used..and I still do..nitrogen to get them close straight away...it expands less...
I ran 30f and 28 rear cold N on the LC V8...it worked fine...still spun them up but that was the power..
With the slicks on the LH I was using same then last meeting dropped them to 26 cold N all round...it hooked up better and steered better so no definative answer.maybe Greg is right for slicks/cars...lower is better...its trial and error.The squeal could be anything...late turn in, your driving style, camber settings...they like heaps those LC things..even rim width....
R
82911/Greg used to run very low pressures to start on his old NC LJ XU1 for the circuit stuff ..22 off mermory then lets them heat up...on bikes the optimum was 36 front and 42 rear hot..we used..and I still do..nitrogen to get them close straight away...it expands less...
I ran 30f and 28 rear cold N on the LC V8...it worked fine...still spun them up but that was the power..
With the slicks on the LH I was using same then last meeting dropped them to 26 cold N all round...it hooked up better and steered better so no definative answer.maybe Greg is right for slicks/cars...lower is better...its trial and error.The squeal could be anything...late turn in, your driving style, camber settings...they like heaps those LC things..even rim width....
R
Edited by rorym, 27 August 2009 - 05:34 PM.
#3
dattoman
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Posted 27 August 2009 - 05:39 PM
Depending on the track I used to run my datto anywhere from 20-24 cold
Rear slightly lower than fronts since they did more work/slide and heated up OK
But I wanted some steering early in the sprint so the fronts were usually 2 lb more than the rears on startup
Depends on the weight of the car , track , grip and driving style... weather... everything has an effect
I'd go low... start experimenting... find where your comfy
40 is too high even on a radial (my opinion)
A rag slick though... usually lower than a radial
Rear slightly lower than fronts since they did more work/slide and heated up OK
But I wanted some steering early in the sprint so the fronts were usually 2 lb more than the rears on startup
Depends on the weight of the car , track , grip and driving style... weather... everything has an effect
I'd go low... start experimenting... find where your comfy
40 is too high even on a radial (my opinion)
A rag slick though... usually lower than a radial
#4
_rorym_
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Posted 27 August 2009 - 05:47 PM
Bruce Dummett runs 4 deg neg...and is one of the fastest around.ex Qld Rally Champion...with no tyre squeal...same tyres on 7" rims.
R
R
Edited by rorym, 27 August 2009 - 05:48 PM.
#5
_Baronvonrort_
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Posted 27 August 2009 - 07:13 PM
Take some photos of your tyres and post them here so we can see the texture of the tyre where it is wearing and since you drove it home it wont help as much we need to know what they look like when you come off the track.
Need to see all 4.
The tyre is also a air spring so tyre pressure can also be used to slightly trim balance of car.
Lots of other variables softer slicks are constructed different and use lower pressures as they heat up different to harder slicks with different construction that need slightly more pressure to get the heat.Generally i have found the softer the tyre the lower the cold pressure.
What cold pressure range do Toyo give for these tyres min/max and max might only be for putting tyre on rim?
Need to see all 4.
The tyre is also a air spring so tyre pressure can also be used to slightly trim balance of car.
Lots of other variables softer slicks are constructed different and use lower pressures as they heat up different to harder slicks with different construction that need slightly more pressure to get the heat.Generally i have found the softer the tyre the lower the cold pressure.
What cold pressure range do Toyo give for these tyres min/max and max might only be for putting tyre on rim?
#6
_jklumpp_
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Posted 27 August 2009 - 07:37 PM
Yeah, I'm currently running 4deg +ve castor & 2 deg -ve Camber - settings suggested by Greg/82911.
Tyre squeel was a funny one - as I said, never had it before - only at wakefield... mind you, I wasn't the only one so maybe the track/weather/temp of the day....
Tyre squeel was a funny one - as I said, never had it before - only at wakefield... mind you, I wasn't the only one so maybe the track/weather/temp of the day....
#7
_rorym_
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Posted 27 August 2009 - 07:52 PM
Talk to Greg...I am running 3 castor...At Speed I am going down to 26f/24r as Baron says...I reckon I will pick up a minimum of 1 sec a lap. My softs need heat quickly...
R
R
#8
_Baronvonrort_
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Posted 27 August 2009 - 08:49 PM
Had a look at your wakefield lap and tyre squeal at T1 was caused by you overdoing it slightly and the back has come around.
Cost you a few tenths as well so tidy up mid and corner exit apart from that not a bad lap.
Cost you a few tenths as well so tidy up mid and corner exit apart from that not a bad lap.
#9
_jklumpp_
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Posted 28 August 2009 - 08:04 AM
Thanks Baron,
Yeah, Wakefield was also where I first noticed the LSD slipping... hence the engine rev's at T1 - that was actually the inside rear lifting!
Was only my second run at wakefield, and managed to knock almost 4 sec off my PB... so I am getting better... but I think I'm still about 4sec off the NC guys... There's more to come from the driver and car!
Is Greg still around on here?
Also, I noticed you are all only talking cold pressures - does no-one else measure them hot? I would have thought that as different tyres work harder than others, pressures that are equal cold will be unequal when hot?... that's been my rational why I always measure them hot (& I do find a difference tyre to tyre after they start equal cold)
Yeah, Wakefield was also where I first noticed the LSD slipping... hence the engine rev's at T1 - that was actually the inside rear lifting!
Was only my second run at wakefield, and managed to knock almost 4 sec off my PB... so I am getting better... but I think I'm still about 4sec off the NC guys... There's more to come from the driver and car!
Is Greg still around on here?
Also, I noticed you are all only talking cold pressures - does no-one else measure them hot? I would have thought that as different tyres work harder than others, pressures that are equal cold will be unequal when hot?... that's been my rational why I always measure them hot (& I do find a difference tyre to tyre after they start equal cold)
Edited by jklumpp, 28 August 2009 - 08:11 AM.
#10
_rorym_
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Posted 28 August 2009 - 05:22 PM
I quote cold with Nitrogen because it moves bugger all...if normal air look for 4-6 psi depending on the abuse to heat up...
I havent used my pyrometer on the Torana as it not really ..well..useful....I will on the open wheeler though..I have seen 3 secs a lap come from pyrometer reading on F5000 cars when you know what you are looking for/doing...and I had good teachers..
R
I havent used my pyrometer on the Torana as it not really ..well..useful....I will on the open wheeler though..I have seen 3 secs a lap come from pyrometer reading on F5000 cars when you know what you are looking for/doing...and I had good teachers..
R
#11
_rorym_
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Posted 28 August 2009 - 05:30 PM
A perfect example..The ex Alan Jones Lola at Speed in 2007.
Whom ever set up this car needs a bat shoved up their arse..check the front tyres..it tore them to pieces over the weekend...There is a better front on shot I can't find but you get the picture.
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Whom ever set up this car needs a bat shoved up their arse..check the front tyres..it tore them to pieces over the weekend...There is a better front on shot I can't find but you get the picture.
R
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#12
_Baronvonrort_
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Posted 29 August 2009 - 03:35 PM
Measure them cold and hot.
Cold is what they are before going onto track so when you check them before you go out they are cold,keep them shaded as sun warms them up.
Nitrogen like rory says is the go because humidity levels in air mean a vairiable so nitorgen more consistant,tyre should also be initially inflated with nitrogen when installing tyre on rim as well.
With a soft tyre like rory is using 1/2 psi should be noticeable and since his sprint is only 2 laps intial pressure might be a little higher than if he was doing 10 laps.
Depending on how many runs he does rory could have slightly different pressures each run.
Stay on line and dont run over marbles on inlap because if you pick up rubber and too much sh#t you blindfold the people trying to read your tyres.
If your tyres are being chewed up rapidly something is not right-driver or car or both who knows.
It sounds like the inside rear was bouncing up and down rather than just lifting which isnt good exiting T1 so what shocks do you have?
Cold is what they are before going onto track so when you check them before you go out they are cold,keep them shaded as sun warms them up.
Nitrogen like rory says is the go because humidity levels in air mean a vairiable so nitorgen more consistant,tyre should also be initially inflated with nitrogen when installing tyre on rim as well.
With a soft tyre like rory is using 1/2 psi should be noticeable and since his sprint is only 2 laps intial pressure might be a little higher than if he was doing 10 laps.
Depending on how many runs he does rory could have slightly different pressures each run.
Stay on line and dont run over marbles on inlap because if you pick up rubber and too much sh#t you blindfold the people trying to read your tyres.
If your tyres are being chewed up rapidly something is not right-driver or car or both who knows.
It sounds like the inside rear was bouncing up and down rather than just lifting which isnt good exiting T1 so what shocks do you have?
#13
_jklumpp_
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Posted 29 August 2009 - 08:08 PM
Can't say I felt it bouncing.... Shocks are Koni Adjustables....
#14
_rorym_
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Posted 30 August 2009 - 10:02 PM
Adjusted at what Click?..towards hard or soft?
R
On the nitrogen...we inflate...bleed down twice..them do final inflate...just stuff I picked up watching F5000 guys years ago.
Barons nailed it..dropping from 30f/28r to 26 f&r I could feel the change instantly...more grip...better point etc..huge difference.
R
R
On the nitrogen...we inflate...bleed down twice..them do final inflate...just stuff I picked up watching F5000 guys years ago.
Barons nailed it..dropping from 30f/28r to 26 f&r I could feel the change instantly...more grip...better point etc..huge difference.
R
Edited by rorym, 30 August 2009 - 10:05 PM.
#15
_jklumpp_
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Posted 31 October 2009 - 12:15 PM
OK, here's the pics of the tyres after Wakefield park...
I was given a tip from Bruce Stewart that the tyres should increse by 4psi from Cold - more than that and they are too low, less than that they are too hot....
I tried to give that a go, but seemed to just be chasing my tail adding more pressure to the tyres....
I started on Sat with 28psi, but some tyres were up around 36psi hot... so I added more, but then they got up to around 40psi hot... so I ditched that idea....
Sunday I just started with 30psi cold, and then balanced them out at 36psi hot.... it was a busy day with Dad sharing the car with me, so I didn't play around too much....
(tyres are all viewed from Top front)
I was given a tip from Bruce Stewart that the tyres should increse by 4psi from Cold - more than that and they are too low, less than that they are too hot....
I tried to give that a go, but seemed to just be chasing my tail adding more pressure to the tyres....
I started on Sat with 28psi, but some tyres were up around 36psi hot... so I added more, but then they got up to around 40psi hot... so I ditched that idea....
Sunday I just started with 30psi cold, and then balanced them out at 36psi hot.... it was a busy day with Dad sharing the car with me, so I didn't play around too much....
(tyres are all viewed from Top front)
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#16
_rorym_
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Posted 31 October 2009 - 03:03 PM
The R/R looks to be cooking...the others seem to be shaving OK..Problem with RA1s is they are basically a wet weather tyre,(check the website) they are REALLY soft...you will cook them up after a few laps. Lap times or a pyrometer are the best way of IDing problems.
R
R
#17
_Baronvonrort_
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Posted 10 November 2009 - 06:27 PM
Be a bit easier if you dusted off the tyres as we can only see the black stuff on the edges.lol.
With the RR its cooking pretty bad on one edge is this the inside or outside of the tyre?
Was it still lifting the inside rear (RR) at T1?
If the ideal pressure rise cold to hot is 4psi (assuming this is correct for this tyre) if it goes up by more than 4psi use less cold pressure,If it does not go up by more than 4 use higher cold pressure.
Track conditions also change during the day so cold track when shadows cover it late afternoon to hot when sun is above at midday just makes things a little more fiddly.
I dont know how many laps you do each run probably best to do the same amount each time as cold pressure could be different for a 5 lap run compared to a 10 lap run.
Did you improve with your laptimes?
With the RR its cooking pretty bad on one edge is this the inside or outside of the tyre?
Was it still lifting the inside rear (RR) at T1?
If the ideal pressure rise cold to hot is 4psi (assuming this is correct for this tyre) if it goes up by more than 4psi use less cold pressure,If it does not go up by more than 4 use higher cold pressure.
Track conditions also change during the day so cold track when shadows cover it late afternoon to hot when sun is above at midday just makes things a little more fiddly.
I dont know how many laps you do each run probably best to do the same amount each time as cold pressure could be different for a 5 lap run compared to a 10 lap run.
Did you improve with your laptimes?
#18
rodomo
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Posted 10 November 2009 - 07:48 PM
With the RR its cooking pretty bad on one edge is this the inside or outside of the tyre?
AS the tyres are directional, that would be the inside?
#19
_jklumpp_
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Posted 10 November 2009 - 08:23 PM
That wear on the edge is actually old... I rotate the tyres front to back from round to round to even out the wear... and I have had them rotated from left to right a while a go as well.... probabl;y makes it a bit hard to read - epseically from pictures - it's obvious when you're looking at the actual tyre...
As for the dirt - I think that was a result of some 'enthuastic' last laps, that included a little rally cross....
Here's the pics from after Oran Park... They are a little cleaner...
Arrow point to inside.
Quite a bit of buildup on the inside edges of the tread... is this a sign of too low pressures?
I was running 35psi hot.... but due to not being well, I didn't bother checking them too much - just the once early on in the day...
As for the dirt - I think that was a result of some 'enthuastic' last laps, that included a little rally cross....
Here's the pics from after Oran Park... They are a little cleaner...
Arrow point to inside.
Quite a bit of buildup on the inside edges of the tread... is this a sign of too low pressures?
I was running 35psi hot.... but due to not being well, I didn't bother checking them too much - just the once early on in the day...
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Edited by jklumpp, 10 November 2009 - 08:30 PM.
#20
_jklumpp_
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Posted 10 November 2009 - 08:41 PM
That makes a little more sense.... though still a bit confusing to think about! So let's say I start with 28 cold all round, you would say I'm aiming for 32 hot. If I measure hot, and it's say 34 - then my cold pressure was too high, right? So do I drop seom pressure with them hot, or wait for them to cool (they are never really going to 'cool' back to where I started)? If I drop say 1psi hot pressure (down to 33) is that likely to still be too high? & what pressure am I now aiming for (does dropping 1psi hot = 1psi cold, and therefore an equivelant of 27psi cold temp?)... man my head hurts!!If the ideal pressure rise cold to hot is 4psi (assuming this is correct for this tyre) if it goes up by more than 4psi use less cold pressure,If it does not go up by more than 4 use higher cold pressure.
Our sessions are 3 'hot' laps, plus warm up & cool down... so it is consistant with each run...
No, didn't beat my previous best... but others also commented that there wasn't the speed in the track... so not sure if it was me, the tyres, the track, or possibly all of the above!
#21
_Baronvonrort_
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Posted 10 November 2009 - 10:29 PM
So let's say I start with 28 cold all round, you would say I'm aiming for 32 hot. If I measure hot, and it's say 34 - then my cold pressure was too high, right?
Our sessions are 3 'hot' laps, plus warm up & cool down... so it is consistant with each run...
No, didn't beat my previous best... but others also commented that there wasn't the speed in the track... so not sure if it was me, the tyres, the track, or possibly all of the above!
Yes 28 cold +4 =32....if its 34 hot then try 26-27 cold.
Make sure you have a pretty good tyre pressure guage worth spending a little then dont drop it or lend it to anyone.
I like to be able to do fractions of a psi as well sometimes might only go in 1/2 a psi either way when close.
I have always had some type of shelter at the track so getting tyres back to ambient temp in the shade not really a problem if you have time between runs,sun heats anything thats black if not shaded.
I prefer to measure pressures when cold and its usually the very last adjustment i make before hitting track.
Not sure if you want a grooved tyre for road legal i would consider a separate set of wheels and tyres just for the track slick or similar to welby uses in targa hatch minimal grooves and probably use the road tyres if it rains.
Those rubber worms as you called them are normal happens with soft tyres yes it is harder to judge when they are rotated yet wise to do if limited budget.
Track conditions vary heat cycles harden rubber compound in tyres and sometimes its the driver so it can be a struggle to match your best at times.
#22
_jklumpp_
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Posted 11 November 2009 - 06:39 AM
Yeah I use a lonacre gauge..
"dont drop it or lend it to anyone".... hmm, well here's my pit crew in action
Thanks for the tips... yeah it's the time between runs that may be an issue with getting tyres back to ambient...especially now with 2 of us driving, it's pretty much off the track and back on the dummy grid.
These are a seperate set of wheels & tyres for track use... and they are competition tyres (Toyo proxes RA1)... though someone has said they are basically a 'wet'... but in a sprint you need something that comes on quick... my fastest runs have rarely been on my 3rd lap.
So is there anything I can read from the tyres which will tell me if they're too high or too low? or is the 4psi rule the best way?
"dont drop it or lend it to anyone".... hmm, well here's my pit crew in action
Thanks for the tips... yeah it's the time between runs that may be an issue with getting tyres back to ambient...especially now with 2 of us driving, it's pretty much off the track and back on the dummy grid.
These are a seperate set of wheels & tyres for track use... and they are competition tyres (Toyo proxes RA1)... though someone has said they are basically a 'wet'... but in a sprint you need something that comes on quick... my fastest runs have rarely been on my 3rd lap.
So is there anything I can read from the tyres which will tell me if they're too high or too low? or is the 4psi rule the best way?
#23
_Baronvonrort_
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Posted 10 December 2009 - 08:44 PM
These are a seperate set of wheels & tyres for track use... and they are competition tyres (Toyo proxes RA1)... though someone has said they are basically a 'wet'... but in a sprint you need something that comes on quick... my fastest runs have rarely been on my 3rd lap.
So is there anything I can read from the tyres which will tell me if they're too high or too low? or is the 4psi rule the best way?
I think the mission for your car might have changed and circuit vs sprint are different.
I think those tyres are ok for a short sprint yet not as suited to lapping in the dry.
If you had those tyres on in the wet video at OP then i would get another set for the wet days and look at something with next to no grooves for the dry like what they use in Targas so road legal.
It sounds like brakes are wearing so maybe the hq discs machined/drilled to fit would be next step as circuit work is harder on the car than a sprint and then when will it stop lol.
#24
WhiteA9XS
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Posted 10 December 2009 - 10:12 PM
you need to find out from your tyre supplier what the recommended hot psi is , if they dont know then they should speak to the manufacture or importer. we have done this and also backed it up with recommended tyre tempatures.
each brand and model of tyre has different operating tempatures ..
once you have this information as above set psi lower to cater for track heat up , check psi soon as possible after your run , take some air out or add if needed to bring to recommended hot pressure.
from this you have learn,t your cold starting point for future . you can then play with your cold psi by -1 or +1 psi for fine tuning , it may take a few meetings to find a happy result . i set my cold psi lower on a hot day than i would on a cold day , some tracks also work the tyre harder which creates more heat and psi . its a learning thing .
remember the pressure will drop as the tyre cools between sessions , dont worry too much about this , the important one is when you come in after your session check your hot psi and as long as you dont have a leak the psi will come back up when your on the track again that day .
anyway this works for me and i hope it helps .
each brand and model of tyre has different operating tempatures ..
once you have this information as above set psi lower to cater for track heat up , check psi soon as possible after your run , take some air out or add if needed to bring to recommended hot pressure.
from this you have learn,t your cold starting point for future . you can then play with your cold psi by -1 or +1 psi for fine tuning , it may take a few meetings to find a happy result . i set my cold psi lower on a hot day than i would on a cold day , some tracks also work the tyre harder which creates more heat and psi . its a learning thing .
remember the pressure will drop as the tyre cools between sessions , dont worry too much about this , the important one is when you come in after your session check your hot psi and as long as you dont have a leak the psi will come back up when your on the track again that day .
anyway this works for me and i hope it helps .
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