if my car is loosing traction late in the race, should i lower my tire pressure next time up or raise my tire pressure? and an explanation would be nice...

thanks

 

What kind of tires?
Are you inside the recommended camber for the tires?
What cold tire pressure are you starting with?
What are you tire pressures at the end of the session?
Are the tires done after they "loose traction". or can you use them again, once they've cooled?

 

hoosiers
yes, my camber is around 2.5 frt, 1.5 rr
cold pressure is around 34 frt and 37 rr
tire pressure when done i am not sure!
you can use them again

it just seems that i am loosing traction in the last few laps.

generally, do you lower tire pressure when this happens or raise it?

 

on a proper setup, tire temps should determine pressures.

pressures sound a little high, you need to check temps and pressures when you're done, or after 3-4 laps (this is called "testing" ).

Make sure you're running them even. I get the feeling you're over-pressuring the fronts, and the rears get hotter than normal too.

However, no amount of pressure drop is going to help you if you abuse the tires early in the run.

 

The big question is "What end is losing traction?"

And the answer then could be either. Essentially, at this point you don't have enough information to know what to do. You have an optimum hot pressure (ask the tire guys) and you should be there. However, keeping tires there for a race is hard, they are going to build up lots of heat, and chances are can become overheated. Each end of the air spectrum can cause the same behavior, too low a pressure might actually heat up faster.. too high and the contact patch may be to small, etc.

For some basic reference, FWD SCCA Imptoved Touring racers who fight massive understeer near the end of a race often go for one of two approaches.

1) Set the car up to handle perfect at the start, drive like hell and hope you get a big enough lead to stay in front as the car gets bad.

2) Set the car up "as loose as you can hold on to" at the start, and hope that it comes in for you to race at the end of the race when others are falling off.

Start trying different pressures, come in, take temps, pressures, make notes, make notes, make notes. Come race-day, hopefully you will be better prepared to make a winning decision.

 

Others have already said this, but you need to do proper testing to figure this out. Yes, if the car handles really well out of the box and gets worse and worse as the laps go on, you're probably running too high of pressure and are also probably overheating the tires.

Regardless, the pressures you are running are simply too high for any race tire I'm aware of. I start in the 20's for both Toyos and Hoosiers.

You really need to get the help of a real race shop here. They will take temps, take pressures, and will help you optimize spring rates, alignment, and pressures for racing.

 

As a nice base to start with, id go with 31 FL 32 FR 33RL and 34 RR pull in hot and have someone check temps/ pressures, IF like most people on here you dont have someone to do this for you this will atleast get you in the ballpark. Yes Temps are optimum but if you can only do pressures, I find that R6 grip best right at 39-40psi. I am also assuming you are running Hoosier Rs, if you are running As, Id go 2-3 psi lower. Dont forget that tire pressure that may be good for one track may not be good for another.

 

Your recommendation above assumes a clockwise track and also assumes a perfect balance in the suspension. How can you be so sure of both of those?

Also, ideal tire pressure for your car and suspension is ideal regardless of track or conditions. Only thing that may change is the cold starting pressure.

 

Yes, clockwise. Not too many counter clockwise tracks in roadracing. That is also on a stock suspension. Those are the cold tire pressures I use as a starting pressure and adjust from there, I thought that is what I said in my post, maybe I wasnt clear enough). I am just trying to give him a basic starting pressure to work with. Im not sure what you mean by ideal pressure. Yes I want the ideal pressure, who wouldnt? But that ideal pressure can be different based on the track. We T2 guys with limited adjustablility use tire pressure to help tune our handling characteristics more than people with fully adjustable suspensions
Marty.

 

Yes, clockwise. Not too many counter clockwise tracks in roadracing. That is also on a stock suspension. Those are the cold tire pressures I use as a starting pressure and adjust from there, I thought that is what I said in my post, maybe I wasnt clear enough). I am just trying to give him a basic starting pressure to work with. Im not sure what you mean by ideal pressure. Yes I want the ideal pressure, who wouldnt? But that ideal pressure can be different based on the track. We T2 guys with limited adjustablility use tire pressure to help tune our handling characteristics more than people with fully adjustable suspensions
Marty.

 

Ummmm.... I'd have to disagree on this one... In your very own post you comment on clockwise v. counter clockwise tracks... would you not want to adjust your suspension settings to take full benefit of this?

Tire pressure adjustments are made at the cold pressure but really only matter when at temp on the track. Each track, the track condition (green, heavy rubber etc.), weather, yada yada amounts to a need for suspension changes. In T2 trim where suspension adjustments are minimal, we use on-track pressure (of course taking in to consideration the temperatures across the entire surface) to adjust the handling. A little hint... 1psi = ~20lbs in spring rate change. Sometimes as little as a 1/4lb change in a single tire can make a difference (just ask the NASCAR boys)...that is once you've tested with the setup and tires enough to know the difference. Hint # 2 ... nitrogen is worth it from the start, if you record your data and keep it you'll at least have a starting point to work from... much like Marty was trying to give the guy in a much simplified form.

We all continue to learn and although we may disagree on indivudal points, we share the same passion for Evo Speed...love to compare notes offline on various tracks and tires etc. if you or anyone is interested.

 

No counter-clockwise tracks in road racing? What about Laguna Seca? Or two club tracks here, Buttonwillow and Thunderhill?

 

I wasn't clear here -- most race tires have a small range of hot pressures and temperatures where they are truly happy and offer maximum grip. The tire engineers will tell you this, and if you can adjust everything else in your suspension they'll tell you where you ultimately want to get the tires to. This is obviously affected by the tire size, wheel size, tread depth, and other factors. Adjusting your cold pressures to fit the direction of the track and the inherent balance of the car is still going to be required for each track and the track conditions.

That said, I agree with you that you can use pressure as an easy way to compensate for a chassis imbalance. This is just as valid a tuning device as any other part of the car. I made a bit of a leap in what I said to the person who started this thread, in that I doubt he'd be able to feel a 1lb difference.

 

Peter by the way you answered this as well as your other post, you are obviously trying to start something, go start it with someone else. How is saying "Not too many counter clockwise" confused as " No conter clock wise tracks in racing" ??? The runoff are held at HPT which I ran iin last year and it is counter clockwise!! MOST roadracing tracks and NEARLY all o them back east run clockwise AND I was stating where I start from when I go to a new track!! At HPT I used my brain and actually reversed the right to left numbers as a STARTING POINT!!!!
Marty

 

easy guys, everybody out to the garage to wrench on somethin.