I'm starting to become real serious about dialing in my car at track days. Since I now have camber plates I want to find the ideal amount of camber to use. To determine this I'm assuming it's critical to use a pyrometer to measure the tire temps across the tread and adjust the camber until I get a consistent temperature across the face of the tire.

Question is the following: Which is more effective for gathering this data, a contact or infrared pyrometer?

 

Contact pyrometers are supposed to be more accurate for checking tire temps. All of the pros I have seen use contact systems. I already have an infarred pyrometer so that is what I use, it's quick, easy, and seems to be fairly accurate.
Keep in mind that several factors other than camber will affect the tire contact patch under load. Tire pressures and adjusting my driving style helped out a lot. I was able to get less than 30 degrees F across the outside front tire on the stock suspension, I thought that was pretty good. My lap times improved and outside edge tire wear/scrub went down dramatically.

 

Thanks silver surfer! So if I was to just buy one from scratch you would reccomend a contact unit? What type of adjustments did you make to your driving style?

 

Either type will work but the contact systems seem to be more accurate so I would go with that.

I am used to driving a more balanced high power RWD car. With that type of car I would trail brake into a corner to load up the front end and then gently turn in, as the car starts to rotate apply light throttle to get the car in a nice four-wheel drift. Then you can either lift or apply more power to adjust the attitude of the car.
With the EVO (my first front/AWD car) I found that once you load up the front and it begins to under steer, it is almost impossible to get the rear end to come around at that point. What seems to work best with this type of car is to essentially pitch it into the corner, intentionally getting it a little crossed up (if you know what I mean). It sort of went against my experience and instincts so it took me a while to make myself purposely upset the balance of the car going into a high speed corner. The car is just so predictable and cacheable its actually very easy and a lot of fun.
So with the EVO I turn in a bit later with little or no trail braking (you do not want to load up the front end to much) and then pitch into the corner, once it’s pointing in the right direction you just stomp on the gas and power right through the corner.
Pitching basically entails turning the wheel a little harder and faster than you really need to for a given corner and then backing off the wheel for the appropriate slip angle. This is something that I got a feel for with a little bit of practice.
What seems to happen is when you initially turn in the front of the car moves in and starts to drag the back end. If you then back off the steering angle in the front it reduces the front slip angle and allows the rear end to come around since it then has the greater slip angle. Also if you go into a corner way to fast it is hard to get around the cars natural tendency to under steer, so….

I also found when you start making more power you can get all four wheels to start spinning in a nice four wheel drift coming out of a corner, it’s a lot of fun. If you get a chance to drive in the rain do it, this car is untouchable in the rain. It reacts more like you would want it to do in the dry, I guess it is essentially a rally car designed more for low traction surfaces hmmm. I am dying to do some dirt/off road high speed driving, it’s just still a little to new, but soon.

I would still like to get the car to initially over steer more easily, at some point I will be going with a fully adjustable coil system. For know this is what works best for me on the stock suspension:

Front: -1.5 camber, 1/8 toe out (total) A046 32-33 PSI cold
Rear: -1.25 camber, 0 toe (planning to try 1/8 toe in) A046 37-38 PSI cold

IMO it probably could use -2 or -2.5 camber in front and maybe lowered 1 to 1.5", but of course that is not an option for me yet. I also drive it on the street a lot so...

I hope this makes sense and helps you.

Regards,

Eric

 

All our tire techs use the contact pyrometer. The infared is good for getting track temp. In fact there is a company that makes a pyrometer that attaches to your Palm pilot. It has a probe attachment and stores all your temp data. My boss has one and used in for the Factory BMW team he worked for.

 

What do you mean by 'track days'? Is it just straight-ahead drag racing like I hear most street races are? Is is it actually racing on a track. The latter would be more fun and something I would want to do, not just a drag-race, that sounds too boring.

 

We have found that a contact pyrometer is more accurate than the infrared ones. The infrared meters only read the temperature of the initial surface its hitting. Because the outer surface of the tire cools the fastest, this can be an inaccurate reading. With a contact meter, you can stick the tire slightly below its outer surface to where it hasn't fully cooled yet. This provides a more accurate reading of the tires temperature.

Competition tires work their best in the 180-200 degree range with 180 being optimal. If the tires are registering 200+, a change in air pressure, the cars setup, or driving style needs to be changed.

Also, its best to tune your tire pressures at hot temperatures. You want to do this because that is the pressure and the temperature the tires will experience while on the track. Then let the tires cool, check the pressure cold, and then fine tune from there.

I hope this has helped answer some questions

 

The only time I race in a straight line is in between turns.

 

So where do you race at? How much is it and what kind of races are they? And what are the types or prizes and such?

 

These are open track days. There's no competition, the goal is to improve your skills and get real seat time on a track. I'm shooting for competing in a years time, most likely in karting. There are many organisations that put on track days from NASA to SCCA and a lot of smaller private groups. Just pick a track you want to drive at and see their schedule for the year and there will be a group on there you can sign up with.

 

go-carts?

 

Yup, I tried SCCA Solo II and it was just too expensive for me.

 

how would test-driving in a real car help out a lot in go-carts? I know generally it would, but like with the different sizing and weight, etc. it would seem a somewhat different experience.

 

It's all about reading the proper line and pushing it and keeping it at the limit. Most people usually go from Karts to cars, I'm reverse engineering it.