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Interesting inconsistencies on the Hoosier info page:

(more accurate link here)
http://www.hoosiertire.com/Tctips.htm#T ... mendations



Not more than 2 paragraphs later they write:


I'm very skeptical about this magical disconnect between the front and rear tires. Somehow, reduced pressure in the rear is good, but not in the front.

One thing to note... There is no place in this article that says increasing pressure from the optimal point increases performance. We've hashed this out before. For a certain car, surface, temperature, etc, there is ONE tire pressure that will give the maximum grip. Going above or below that pressure will reduce the amount of grip. The hard part is setting the baseline (something the Hoosier article might help with).

Scott

This is what gave me the biggest clue that I'm way off. The fronts were working some but not fully, showing a light texture but not looking like they were fully up to temperature. The rears had the texture of a plastic countertop, not working at all.


I figured chalking would be useless. I did walk around and note that everyone else on Hoosiers seemed to be working more of the tread width to the outside of the tire than I was. But the contact probe mention is a level above my knowledge -- I know what it is, I know to measure three places across the tire, I know to get the measurements as soon as possible after the run. But what do I do with those numbers? I have no idea. (I also don't have a pyrometer, but I figure they can't be too expensive these days, though. At least, not compared with a new Optispark )


This is almost what I need, but it's still assuming I know a more than I actually do. I'm still trying to get the real basic assumptions.

Let me try and state how I read this, please correct me because I'm probably still way off:
At the start of the day, you set the pressures cold to what you want to be running. As soon as you come off each run, you bleed the tyres down to what you set originally. Eventually the pressures are such that the tyres show the correct hot pressure after the run. (Did you then at some point let them cool to determine your baseline cold setting?)

So by "hot" pressure, you mean immediately after you come off the course, and your goal is to set the pressures so they show a predetermined correct hot pressure?

Does that mean you start out setting the cold pressures a little high in case you don't see as much increase in a particular set of conditions/course?


That would be my ideal, yes. Sorry to repeat myself, but how exactly should I determine my base pressure?


With my car, in Stock, I run the most camber and caster I can get. I know the tyres could use it more negative, but I can't get any more in there. The fronts are at the limit of adjustment, which is a little less than a degree of negative camber. The rears ain't moving without bending the live rear axle. Only thing I can really play with is toe, and my baseline setting is 1/8" out.


I especially appreciate the Hoosier-specific information.

I'm still somewhat at a loss.

Edit: Dayyyy-am! It does alter the correct spelling of tire. /sigh As long as it doesn't "correct" the spelling of my name... (Yes, I did run across a program that would not let me enter my name as it is actually spelled.)

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Martyn Wheeler
AXing Kit's '05 Mazda 3, #29 HStock
(when The Gonzo Symphonic allows)

Laurinburg has tremendous grip with R compounds. If it was your first time on them there, it's likely IMHO that you didn't drive them hard enough. We didn't build any even noticable heat in the tires with two drivers until our second afternoon runs, and then we only gained about 2 # of pressure. If you didn't push them hard it's unlikely you built any heat at all. There are markers on the sidewall where you want to see wear down to but not beyond.
You can buy a good single reading probe for ~ 100.00 but you need someone to record the temps as you take them so you can analize the readings, or buy the ~300.00 recording unit. Temps even across tread = perfect. Outsides warmer than center = too little pressure. Center warmer than outsides = too much pressure. Progressively warmer outside to inside = too much camber or toe out. Progressively cooler outside to inside = too little camber, overdriving (especially with strong edge rollover), too much toe in. You need to check several runs on a day with warm temps and minimal wind so the driving can be averaged out.
That's the price of stock class you have to comprimise and balance for what the factory gives you.
No, we set the same base pressure no matter what the temp and bleed down after each run back to that pressure. It's unusal to have conditions such that you'd adjust the base pressure in anticipation of heat build. Maybe if you stored your tires in your AC'd room all night at a hot summer event? See above for determining base pressures with temp probe. Next best option is ask someone familiar with running the same R's on a similar car (like Sammy).

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SPIN or WIN!
there's no glory for going slow.

Scott, you have to read carefully when comparing info because they are talking about two totally different tires in that article. Their P-metrics which are their full competition slicks and the DOT SO4s.
You are right, once you have found the optimal pressure, increasing or decreasing pressure will result in loss of grip. However when looking for more grip, increasing the pressure is the first direction to try. If it doesn't improve traction, you were likely above optimum to begin with. What they are emphasizing is that the optimum pressure might not feel as "comfortable" as lower pressure but will give more grip, but many THINK they are getting less grip according to their butt-o-meter. Since the rear tires are not involved in steering the car the optimal pressure is less critical in the rear on cars "with IRS suspension (having) adequate camber gain and roll control" and "a slightly lower pressure may improve CONTROL (not grip) at the limit".

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SPIN or WIN!
there's no glory for going slow.

Interesting interpretation. Maybe it works for your Celica, but this discussion is centered around an FS Camaro, which has neither optimal front suspension geometry or IRS/optimal rear suspension geometry.

Martyn - did the car slide anywhere on course, understeer or oversteer (other than wild throttle induced oversteer at the finish)?

If you never had understeer at turn in, then you never pushed the front tires (Chuck is right on that point!). After a little tire comparison, and soul searching, I determined my problem the first time out on Hoosiers was the driver.

I gained several seconds just by driving harder.

Scott

A slow response this time because I had to think about it carefully...

Considering I was about 10 seconds off Jim's pace, it's very likely I wasn't pushing hard enough. So if you weren't seeing much heat, then my issues could pretty much be blamed totally on the driver. (I like that. Driver problems are the cheapest to fix, and the most fun when I fix them.)

That actually makes me feel much better.


I am not even close to these, nowhere near it.


I'm definitely coming to the conclusion that the driver is the main source of my problems.

That said, there was a distinct difference in traction between the first few gates, the rest of the runway, and the taxiway and P. The earlier part of the course was dominated by understeer, going away later. Come to think of it, the main difference might well be the fast sweeper that I took hard enough finally to warm the tyres up a bit -- I think I took the section from the sweeper to the taxiway slalom section hard enough. But I knew I took the offset gates in the P fairly slowly, so that might have cooled it down then.

I was getting understeer at turn in, but not to the point of breaking free. I figure now that was mostly overdriving and not managing weight transfer correctly, but it felt like the tyres not warming up was a contributing factor. Come to think of it, I was having unusual difficulty coordinating weight transfer with turn-in, and I guess that means driver error really was the source of the understeer.

The last turn excursion was pure excessive speed, understeer actually. With the suspension set up to provide rear traction, and the weight transferred to the rear too, the front pushed wide. I adjusted to head towards the finish, but that induced the lateral slide, and when I was sure that my slide would clear the timing lights, and any further attempt to make it might threaten them, I let it slide off course. It wasn't so much of a spin as a severly overdone drift.

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Martyn Wheeler
AXing Kit's '05 Mazda 3, #29 HStock
(when The Gonzo Symphonic allows)

I think you are getting way too analytical! The car was understeering aka pushing. That is 99% driver. That is the "easy" part to correct. If the car was very loose, then I would think about shock and tire settings.

What kind of shocks do you have on that beast? By the way...someone mentioned it being a Camaro...it is a Firebird. There is a difference in our mullets.

As far as pressures...I guess the S05's have the same issues as the S04's and they need the high pressures. Otherwise, you will cord the outer edge. Keep an eye on that. With so little negative camber, it will be an issue. Don't forget Sammy drives an ESP F-body on V710's

Live rear axles rule

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Jim Pastorius
2008 Silverado VortecMax
1992 Camaro CMC#92
2002 BMW R1150R

2009 3rd Place CMC Mid-Atlantic Championship
2009 CMC Hyperfest Winner

Thanks for the tip on the oatmeal. It looks like I was getting some decent work out of the A3S05s (first time on any R for me).

Of course, I'm still learning to not overdrive the car—very easy to do. And in doing that I'm sure I'm giving up time where I don't need to be.

I guess I'm simple. Since the car is so new to me, the tires are so new to me, I'm setting my fronts at 39-40 and the rears to 43-44. The only checking I'll do after that is make sure they haven't gone flat.

Once I can start getting a better feel for what I'm doing and that it's not wildly different from run to run, I'll start tweaking tire pressure.

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Not spectacular just decent.
I'm not sure what I'm driving.
Maybe an ITR in DS.
Or half-assed STX prepped 330.

?? you brought up the quote and asked why the discrepency between the front and rear pressure sensitivity. I never implied it had anything to do with the Camaro or even the Celica. My experience in all my racing endevors has always been that the product's manufacturer has the most knowlege and experience with their product and it's in their best interest that it performs to it's maximum potential, so I tend to ask them for their advice and listen to it over other end users anecdotal advice, but that's just me. If you find going the opposite direction works for you, then I'd say go with it, you were obviously very quick this past weekend. When are you going to bring it to a national event?

_________________
SPIN or WIN!
there's no glory for going slow.

I disagree with this assumption. Their first concern is safety and longevity. You might get awesome performance out of an S05 at 32 psi. But no one will spend the money for that performance over 4-6 runs. Or in NASCARS's case, 10 laps and smacking a wall.

Further more, the manufacture is probably taking a guess at the pressure you should be running. I highly doubt they test for all the cars that are available. They sure as heck don't publish those tests. And any numbers we hear are antidotal from these mysterious tests.

I will accept the fact the manufacture's suggestion is a good starting point. But is only one good place to start.

Martyn is kind of screwed, since you could probably count on one hand the number of f-bodies running Hoosiers.

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Jim Pastorius
2008 Silverado VortecMax
1992 Camaro CMC#92
2002 BMW R1150R

2009 3rd Place CMC Mid-Atlantic Championship
2009 CMC Hyperfest Winner

I agree with Jim on the manufacturer information. I run Hoosier GAC take-offs and spent a good half-an-hour at their truck getting tech info and they would only supply guidlines. It seemed every sentence ended in "but the best way to determine this is through test and recording data." They made it abundantly clear that their pressures were ballpark numbers.

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Rich
http://www.v8mongrel.com/

When I ran R-compounds on the GS Celica, we were consistently running a 10 psi difference than most of the other competitors on the same tire with the same car. That's what worked for our car. With alignments, driving style, shock settings, etc., it's too easy to say that 'this is the pressure to run'.

I remember back when Jim P had the MR2 and everyone in the class ran the exact same settings and pressures.... Then Salerno came to Nationals and messed everything up with a different front bar. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

Camaro owners got the rattail in the haircut draft after the Firebird owners got the first ball and chose the mullet. Subaru owners gleefully rocked the house and snatched up the Flock of Seagulls do.

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Has no responsibility whatsoever.

Martyn,

Did you buy the tires new? Based on Miles Beam's and my experience last year with various takeoff tires my opinion is that you really don't know what you have unless you personally have driven them since their very first runs. That way you know what they are like fresh and have some basis for knowing whether they have deteriorated at one or both ends of the car. Keep in mind also that "flipping" tires on the wheels car really screw up traction until the tires wear in to their new orientation. Also, the grit (tire and surface)and temperature (air, surface, and tire) variations are much more of an issue than minor changes in tire pressure. My RULE for 3 decades has been to determine an optimum "start of run" tire pressure in test sessions and then set the tires to that pressure for the start of each competition run. Most of the pressure change from heat, in my opinion, happens after the run ends and the heat from the rubber, and maybe even the wheels from braking, has time to heat the air in the tires.

Also, in my experience the time available from fine tuning tire pressures is minimal, especially if the car and driving are not already at the top of their game so to speak. I get huge time improvements from driver learning curve and, on colder days, tire heat with any temp sensitive tire. This assumes reasonably fresh R tires or slicks. My run to run improvements are NEVER from changing tire pressures or any car set up variable. It is all "nut behind the wheel" and/or tire heat.

Finally, I suspect that when a particular driver is successful with pressures drastically different from what other Nationally competitive drivers in the same type of car use it is much more that the different pressure caters to their driving style. i.e. some drivers really do well with LOTS of slip angle and low pressures might favor that style. Other drivers may like a "crisper" feel, even at the expense of a little bit of grip.

Dick

_________________
Dick Rasmussen

FS 50 2018 Mustang GT

Martyn, are you running the WS6 Firebird? If so, I was working on course at the last worker station in the P for the morning session. I recall paying attention to the car (mainly b/c it's big, fast, and cool) and remember that it appeared that steering imput was being initiated way too late through the various features! IIRC, the car was being turned in abruptly at those features. I can't recall anything about braking points. So, the late turn-in definitely would explain the push. It also gets the car out of balance and makes it harder to control or keep at the limit.

Driving a big powerful car like that requires a lot of finesse to coax it around those featues. I guess the same is true for small cars as well. Remember, "turn early and turn less!" That way you're not asking the front tires to do too much work and it keeps the car in balance, hence making it easier to make mid-feature adjustments. And, it allows you to use the throttle as a tool to get yourself out of trouble. Just focusing on early and minimal turn-in *and* early braking actually makes it easier to drive fast than to drive a bit slower...if that makes sense. Some short guy from Richmond used to tell me that all the time

I strongly agree with Dick's comment that the time that can be gained from "fine tuning" pressures is minimal. Yes, tire pressure is very important and you should try to optimize it, but a few PSI either way in most situations isn't going to make a big difference in your time. *If* the driver is doing the right things in the car they are going to be fast even if the pressures and shocks settings are less than optimal. Now, if you're trying to win nationals you better have all that stuff pretty close to optimal and drive well.

I've also talked to Jeff Speer from Hooser, read their tech stuff, and talked to a bunch of other people about optimal settings for the Hooisers. Yes, higher pressures (up to a point) will give you more grip, but the car will feel more skatey. So, technically speaking Chuck is correct. That being said, running higher pressures is *not* the right choice for every car, driver, and situation! Without boring everyone with a bunch of stories about this...I've run into many instances involving myself (i.e., regular hack) as well as the best autocrossers in the country where one group of drivers runs low pressures and the other group runs high pressures and they are both equally fast. How can this be? As Dick mentioned different driving styles often require different setups. So, don't be scared to experiment and try something different! Lot's of people have been successful tyring "unconventional" setups with tires and other setup issues. The "textbook" or "factory" recommendations are the best starting point, but not always the right answer for you.

Just a thought on setting priorities for an autox. The average brain can only focus on a limited number of things at an event. In Martyn's case, he alluded to trying to cut down the 10 second gap between him and Jim Pastorius. FWIW, I was about 12 seconds behind ME Fisher (when we were both in 1990 Miatas) the first time I went to Laurinburg back in 1995. If you can figure out where most of your time is being left, put the majority of your mental energy units in pursuing that avenue (i.e., tire pressure, shocks, alignment, driving technique, course memorization, etc.) For example, if tire pressure is responsible for 10% of the time gap you don't want to spend 60% of your effort chasing pressures. Instead, you may want to spend a bigger chunk of time replaying the previous run through you head, identifying things to change, and to focus on. Consider doing a few course visualizations where you do everything right. Then, forgot about it, don't think about the course any more, and just let it happen! World class athletes use this approach for a reason - it works. If you must think about something before your run only focus on *one* thing, like look ahead, break early, etc. That will help keeping your learned curve steep. Once, you start to master the various techniques, you likely won't have any technical thoughts going through your head at all. Thinking technical just before and during a run makes you too deliberate and doesn't allow you to react naturally with the skills you've developed. That's my 8 cents worth, I hope that helps.

Changing topics, as far as Scott Johnson "brining it" to nationals...his performance on Sunday was pretty darn impressive. I'd say that his effort would have easily been a top-10 finish at Nationals or better. Nice job Scott!

Eric