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When searching, most are running higher pressures in the front... why is this?
I've read that higher pressure has more grip... ie to adjust over/under steer, but this is counter intuitive to me. So I take it higher front psi is for balance on a C5 reducing understeer?
Also I'd think the front will heat up more so you'd want a lower cold psi to meet hot target.
I will be running square NT01 for the first time next event and planning on 30psi frt/rr to start (90ish deg) maybe targeting 35psi hot with cool down lap. I will chalk the tire and try a BBQ temp probe... but I really don't know what I'm doing yet.
The car sees tires as springs, more air pressure equals more spring rate, more spring rate is generally less grip. So...balance oversteer with more pressure in the front or less in the rear. Do the opposite for understeer.
With all that said, I shoot for a 9-11 psi difference between hot and cold pressures, keeping in mind the balance objectives when I add or subtract pressure. I run Nitto 555RII's and it's really a combination of watching tire wear and trying to find the optimum pressures without upsetting the balance. Helps to be able to tune with bars and alignment as well so you don't get too far in one direction with tire pressures. .
The car see tires as springs, more air pressure equals more spring rate, more spring rate is generally less grip. So...balance oversteer with more pressure in the front or less in the rear. Do the opposite for understeer.
Ok, this was more what I was thinking. So many of the track guys want to add understeer bias I take it. Stock suspension, staggered tires you would NOT want more pressure in front then right?
In my new square setup a little bias (higher front pressure) would prob be good for me... safer?
IMO, safest is a properly balanced car. Understeer can give confidence, but it's at the expense of turning ability.
Your best bet is to take pressures before (cold) and immediately after (hot) while making note of your car's behavior, then adjusting accordingly. Keep in mind that optimal pressures vary wildly due to a number of factors, including driving style, alignment, chassis setup, tire manufacturer/compound, track layout, temperature, and even time of day.
Though it's tempting to get recommendations, IMO you should play around with it and find what's best for your particular situation.
Wish I could adjust based on feel, but afraid I'm not there yet... first to really know what I'm "feeling" and second translating feel into an adjustment. Chalk, temps, psi are quantitative and something I hope to get a handle on quickly.
I read NT01s like lower pressures than other tires, so knowing this initially will help a lot.
Wish I could adjust based on feel, but afraid I'm not there yet... first to really know what I'm "feeling" and second translating feel into an adjustment. Chalk, temps, psi are quantitative and something I hope to get a handle on quickly.
I read NT01s like lower pressures than other tires, so knowing this initially will help a lot.
thanks for all the input!
I would start with a base tire pressure cold and then run some normal fast laps, enough to get full tire temp (not slipping and sliding TRYING to get them hot). Pit and check your hot pressures.
The NT01 use the same compound as the 555RII's I'm told, so a similar pressure rise to what I wrote about above should be your initial target. Probably easier to start high and bleed them down.
I run a square setup on my C5Z and end up around 35-36 hot. This changes for each track and ambient temps and other factors as Furious noted above. After a few years of running the same tracks, the same months of the year, I have a database of starting COLD pressures that end up with HOT pressures in the ball park. I'm **** enough about this not to push the car to the limits until I'm comfortable with my hot tire pressues
Once you get some seat time and push the car, and start to understand exactly when the tires have reached their maximum grip, you can start to play with tire pressures to balance the car. Good luck
I run 285 / 305 combo on my C5 Z with Continental GTI slicks. I run 22 psi in the front and 21 psi in the rear cold. It handles great. I tried other pressures before and this is what I ended up liking.
When I ran 555RII's I also ran a staggered PSI setup. More in the front, less in the rear. Too much of a difference though definitely effects handling.
Depends on the track and your driving style. My rear tires will gain 1-2psi more than my fronts during a session/race, therefore I start with the rears lower to get the balance I want.
I run 285 / 305 combo on my C5 Z with Continental GTI slicks. I run 22 psi in the front and 21 psi in the rear cold. It handles great. I tried other pressures before and this is what I ended up liking.
When I ran 555RII's I also ran a staggered PSI setup. More in the front, less in the rear. Too much of a difference though definitely effects handling.
Are you buying Conti scrubs? Slightly OT, how many heat cycles are you getting and I assume you're not driving to the track on these? thanks
As was stated, you need to check your temps and pressures immediately after coming off track, after knowing what they were cold. My first season on track I put enough heat into my tires to make about 5-6 psi difference from cold to hot, now i put more like 10-11psi into them from cold to hot. If its misting or even just damp on the track in the morning that can change a lot as well. As I am just an hpde guy and plenty of the guys in here are race guys, I am happy to give up grip for tire longevity, which specially in the front, means running too much pressure over too little.
On the street i run the pressure i want, cold vs hot is of minimal difference. I get to the track lower it 4-5psi for the first session, as i live in wisconsin its always coldish in the morning session and takes a little time to get to temp, ground is usually damp, so session one isn't 10/10ths. When i get off track i check pressure and adjust it to about 2 under my goal, knowing that the cooldown and time to get to my stall in paddock has dropped some temp and that next session will be hotter faster. After second session i check and adjust again and call it good.
rcomps will likely want 34-38 psi hot. I would aim for the top of the range first and work down. If you are use your available grip you will put 10-12psi in your tires from ambient to track temp. If you are not that hard on the tires 5-6 is more realistic. Only way to sort that out is measure asap after you come off track, or tpms i guess if you can get it and its actually accurate.
You really need something to read tire temperature across tread then adjust. OEM pressure is a compromise of wear and ride quality. Maximum grip normally happens when heating is present and equal across tire. It is possible to have a poor setup and cause a tire to be cold .... just along for the ride.3 wheeled cars do well in corners. If
After some experience on the track I have found that I need higher hot pressure in the rear after primarily observing chalk wear... likely due to rear camber of about 0.9deg.
I run about +2psi rear vs front. BUT seems majority run more psi in the front. Do most just have more rear camber than me or could this be driving style? Curious
-Square 275
-rear also gain about +2psi in heat compared to fronts.
-had very even wear for the life of NT01s... I just mounted NT05 and so far seems higher rear psi is even more critical for these based on chalk.
As was stated, you need to check your temps and pressures immediately after coming off track, after knowing what they were cold. My first season on track I put enough heat into my tires to make about 5-6 psi difference from cold to hot, now i put more like 10-11psi into them from cold to hot.
The one thing when working with your psi increases is to strive to get your air with a consistent moisture content.
If you take an air tank to the track and fill it from home, you can control this a bit by draining your compressor and your air tank, then fill it.
If you switch to the track's air compressor , they may not have drained it in 6 months and you'll get inconsistent readings.
I've seen a lot of water come out of the compressor at the track.
You really need to start taking temps. The other thing is make sure that you only use one tire gauge. Tire gauges are pretty inaccurate. If you stick to a single gauge you eliminate a lot of the errors.
I'd love to take temps, but I'm basically solo at the track and asking peeps to help with hot pit is tough ask. So I'm prob going to stick with chalk and wear.
I take it my hotter rear is due to slow turn in, which I will try working on next event seeing if I can get closer to even cold/hot differential.
04-09-2015, 02:20 PM
Front vs Rear Tire Pressure
