track tire pressures
05-07-2012, 10:41 AM
#92
Race Director
05-07-2012, 12:54 PM
#93
Rennlist Member
Hi Guys, I participated in the call yesterday, I would summarize as this...
- wheel(rim) width to tire width is very significant, for best handling, put a particular tire on its associated maximum rim width. Running a narrower tire on a wide rim, or a wide tire on a narrow rim will result in sub-optimal handling
- ambient air temp is significant, and contributes to overall tire pressure during the day
- typically start with manufacturers recommended cold TPs to start with
- overdriving the tires will result in additional wear, overheating, and slower laps
- camber is probably the most significant adjustment affecting wear, especially shoulder
- shoulder rollover should be minimal (look for the small waving michelin man logo on the shoulder, this is about as far as rollover should go)
- consider using nitrogen for the track, it is less susceptible to PVT than "air"
- while pressure monitoring is primary, using a probe style pyrometer to measure tread temperature across the contact patch is the only way to effectively analyse performance
- temp and pressure reading *must* be taken with haste upon exiting the track to be of any value, track characteristics will effect values accordingly
- heat cycling *can* benefit tire performance and lifetime
- shaving produces only minor handling/performance benefits and of course can significantly reduce the lifetime of the tire.
- always check for unusual tire wear, never track a corded or patched tire.
- "squirely" tires are usual overdriven not overinflated...
- RFT tires do not dissipate heat as quickly as non-RFT due to the thicker sidewalls...
- there is no universal 'target' hot pressure (there are too many variables) track temps should be between 160-200F (220F for MPSC+) inner-outer shoulder temps should differ by around +10F, center should be "in-between"
- lower center temp => underinflation, higher center => over inflation.
Last edited by Larry Cable; 05-09-2012 at 02:55 PM.
05-07-2012, 01:03 PM
#94
I emailed Ryan about that weekend for more details as it was a couple years back and my memory is failing rapidly 
This was his reply:
Oh ok. Unfortunately the throttle body failed before I could put down an all out lap, but during the practices I was taking sector times. The fastest complete lap I put down was a 2:13 in the 2nd practice. In the 3rd practice, I was going hard in a different section each lap to get my "ideal" laptime, sector times indicated a 2:09.4. Top speed on the straight was 180.0 with rev limit set to 9,250.
That little Evo is insane!
This was his reply:Oh ok. Unfortunately the throttle body failed before I could put down an all out lap, but during the practices I was taking sector times. The fastest complete lap I put down was a 2:13 in the 2nd practice. In the 3rd practice, I was going hard in a different section each lap to get my "ideal" laptime, sector times indicated a 2:09.4. Top speed on the straight was 180.0 with rev limit set to 9,250.
That little Evo is insane!
Yes.. It is.. and Ryan rings it out too... Fast combo..
05-07-2012, 01:24 PM
#95
Race Car
Thread Starter
Hi Guys, I participated in the call yesterday, I would summarize as this...
- wheel(rim) width to tire width is very significant, for best handling, put a particular tire on its associated maximum rim width. Running a narrower tire on a wide rim, or a wide tire on a narrow rim will result in sub-optimal handling
- ambient air temp is significant, and contributes to overall tire pressure
[*}typically start with manufacturers recommended cold TPs to start with - overdriving the tires will result in additional wear, overheating, and slower laps
- camber is probably the most significant adjustment affecting wear
- shoulder rollover should be minimal (look for the small waving michelin man logo on the shoulder, this is about as far as rollover should go
- consider using nitrogen for the track, it is less susceptible to PVT than "air"
- while pressure monitoring is primary, using a probe style pyrometer to measure tread temperature across the contact patch is the only way to effectively analyse performance
- heat cycling *can* benefit tire performance and lifetime
- shaving produces only minor handling/performance benefits and of course can significantly reduce the lifetime of the tire.
- always check for unusual tire wear, never track a corded or patched tire.
- "squirely" tires are usual overdriven not overinflated...
Tal
05-07-2012, 01:34 PM
#96
Rennlist Member
p.s
they mentioned that a lot of the info in the MPSC "care & feeding" document is also applicable (in general) to the MPSS...
seems like nitro might be the way to go for predictable/low maintenance on track along with wider rims+rubber.
05-08-2012, 11:31 AM
#97
Rennlist Member
Hi Guys, I participated in the call yesterday, I would summarize as this...
- wheel(rim) width to tire width is very significant, for best handling, put a particular tire on its associated maximum rim width. Running a narrower tire on a wide rim, or a wide tire on a narrow rim will result in sub-optimal handling
- ambient air temp is significant, and contributes to overall tire pressure during the day
- typically start with manufacturers recommended cold TPs to start with
- overdriving the tires will result in additional wear, overheating, and slower laps
- camber is probably the most significant adjustment affecting wear, especially shoulder
- shoulder rollover should be minimal (look for the small waving michelin man logo on the shoulder, this is about as far as rollover should go
- consider using nitrogen for the track, it is less susceptible to PVT than "air"
- while pressure monitoring is primary, using a probe style pyrometer to measure tread temperature across the contact patch is the only way to effectively analyse performance
- temp and pressure reading *must* be taken with haste upon exiting the track to be of any value, track characteristics will effect values accordingly
- heat cycling *can* benefit tire performance and lifetime
- shaving produces only minor handling/performance benefits and of course can significantly reduce the lifetime of the tire.
- always check for unusual tire wear, never track a corded or patched tire.
- "squirely" tires are usual overdriven not overinflated...
- RFT tires do not dissipate heat as quickly as non-RFT due to the thicker sidewalls...
Thanks for listening on that. Good info. Did they put out a hot target temp?
Yes it is. I wish he was closer. I could learn a thing or 20 from him
05-08-2012, 11:47 AM
#98
Rennlist Member
they recommend starting with manufacturers cold temps and working from there. While they did not state it, it appears as though the only way to tune tire temps correctly is by beginning with tire temp measurement the instant you come off of the
track ... this is of course complicated by the design of tires such as the MPSS which plays with compound and construction to manage the temp profile of the tire from the shoulder across the profile of the contact patch. You then have to interpret those
measurements in order to determine the "cause" associated with the observed "effect", i.e under inflated would indicate hot inner/outer shoulders and a colder 'center', over inflated would indicate the inverse. Of course corners will cause the outer shoulder
to be hotter than the center/inner ... bottom line its complex, so you need to reduce this to a simple rule, or rules, you can apply without an F1 pit crew!
extrapolating from this, what "you" are trying to do is to tune the suspension (camber) along with the pressure to maximize/optimize the application of the full contact patch of the tire around the circuit to get the tire to approximate a steady state pressure.
Last edited by Larry Cable; 05-08-2012 at 12:23 PM.
05-08-2012, 11:55 AM
#100
Rennlist Member
05-08-2012, 12:17 PM
#101
Rennlist Member
Agreed. But there has to be a temp/pressure where don't work properly anymore regardless of conditions. What about a target number of psi over cold temp? Anything?
05-08-2012, 12:35 PM
#102
Rennlist Member
nope, they mentioned conversationally that they had seen pressures in the 50's on MPSS on some cars and they were still functional... sorry.
05-08-2012, 04:32 PM
#103
Rennlist Member
tire temps should operate between 160-200F on track, up to 220 for cups and similar R compounds. Typically on a well setup tire with appropriate camber etc outside shoulder temp should be around +10degrees higher than inside shoulder (center should not be hotter than outside, or cooler than inside)
05-08-2012, 06:57 PM
#104
Rennlist Member
I have a pyrometer, but I'm guessing most don't. Sure would be easier if they just put out a recommended alignment with suggested hot temps.
I had good luck with 38-40 so I'll stick with that.
I had good luck with 38-40 so I'll stick with that.
05-08-2012, 07:16 PM
#105
Rennlist Member
Since the V(olume) is essentially 'constant' (ok I know its not, however...) the P(ressure) varies directly with the T(emperature). I would not be surprised if you checked your temps around 38-40 that you would find the tire is somewhere nicely in between 160-220F ...
note they recommend the probe style and not the infrared...