heavy85 Posted August 11, 2009 Share Posted August 11, 2009 I have been running Hoosier FA slicks most recently in R35. I was seeing ~120 degF in the fronts and ~130 rears, always 10-15 degrees hotter than the fronts. With Potenza RE01 ~140 in the front and again 10-15 hotter rears. Both are really sticky when I come in and feel to have good grip. I just switched to Avon slicks to try something different. They are obviously built and shaped very differently than the Hoosiers and even feel different to the touch. This weekend was my first event with them and I was seeing 160s fronts and 180+ rears. Obviously based on my previous experience this seems very high but I'm really not sure. Since it was a HPDE I didn't get laptimes for comparison but they felt good with 1.24 peak lateral g. What's 'normal' temps for slicks and I know different brands vary but in general what should be expected. These were taken in ~85 deg weather and in the pits after cool-down laps so obviously were hotter on track. Another quandary. From temps the rear tires are working harder than the fronts. Given it's rear wheel drive this somewhat seems reasonable but at the same time this track is very hard on brakes and the fronts do most of the braking so I'm thinking something is off in the balance and I need to get the fronts to work harder. The car is very balanced but the front end will slide before the rear in long steady skidpad type of turns but I can also easily throttle steer with a big input. I am very careful not to spin the rears so I dont abuse them. Weight is 51% front so it's not a weight distribution issue. Any thoughts on what to expect front to rear temp wise and ways to even it out to get better lap times? Thanks Cameron Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 11, 2009 Share Posted August 11, 2009 Operating temps for the Yokohama slicks I was running were 190-220 degrees. That was part of my problem, I could never get them to operating temp. Stiffer springs will put more heat in the tires. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 11, 2009 Share Posted August 11, 2009 Any thoughts on what to expect front to rear temp wise and ways to even it out to get better lap times? IMHO... Braking and the steering/grip slip angle tend to put more heat into the front tires, at least in my experience given the power levels of the cars I've raced and helped develop. But, because the front tires get a lot more cooling air then the rears its sometimes hard to actually see this when taking tire temps in the pits. Its normal to see either balanced or slightly higher rear temps on a 240Z when measuring in the hot pits, especially if you're using a surface IR pyrometer. A probe pyrometer will tend to show more temp in the fronts but you have to take the temps on the track right after the last corner after some easy braking to a complete stop. Also, the type of diff you're using will greatly affect front and rear tire temps. A welded rear diff will increase the tire temps on the outside front and rear tires. A Quaiffe diff will increase the tire temps on the ouside rear tire. Quote Link to comment Share on other sites More sharing options...
tube80z Posted August 11, 2009 Share Posted August 11, 2009 Cameron, it's kind of hard to tell from what you've written how much the cool down lap lowered your temps. Do you have a hot pit you can come into when you're running? That would be a little better. But generally I'd expect to see temps near 200s for those tires. From my experience you're barely getting them to work, which is why the LA number is so low, unless the track just doesn't have that much grip. If the tires are working I'd expect to see numbers in the 1.4 to 1.5 range. It also seems you're working the rears a little too much. What is the pressure rise? A friends very fast EP car has very similar temps front to rear. At least at this point it sounds like the rear is being worked pretty hard. And as Jon mentions you need to up the springs to build temp in the tires. Talk to the trackside tire engineers and they will tell you the same thing. And if you have dead spots in shocks (from your other thread) that may not help get temp into the tires. Only trick I know is to try and raise the instant centers in your suspension. That should build more heat. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted August 11, 2009 Author Share Posted August 11, 2009 I'm using a probe pyrometer and a stock '88 clutch type LSD. I could use the hot pit but I'm a one man show so it's more difficult to get measurements in pit lane without leaving the gauges there and hope they dont walk or beg for help which I may just have to do. I thought 1.2 was good LA without aero but 1.4-1.5 is where I should really be? Seems I have a ways to go then. I was seeing ~8 PSI rise. I'm also still not sure if the shock is dead or not - obviously there is a little play but the resistance is good if held vertical. If held horizontal the struts skip the first couple cycles which from the other thread there is a bit of debate if that's normal or not. I keep seeing a common theme in my threads that I need more spring ..... Cameron Quote Link to comment Share on other sites More sharing options...
tube80z Posted August 11, 2009 Share Posted August 11, 2009 (edited) If your pressure rise is equal front to rear then your setup is probably ok. Generally if the temps are out of whack the pressure rise will be too. But like John said sometimes one end will cool quicker so you need more data. Don't get too hung up on LA numbers. Your track may not have the same level of grip and you'll see it vary throughout the day/weekend. But if everythings working those numbers are what I've seen on an EP car, which isn't too far from where you can take your car. Edited August 11, 2009 by tube80z can't type Quote Link to comment Share on other sites More sharing options...
johnc Posted August 12, 2009 Share Posted August 12, 2009 I keep seeing a common theme in my threads that I need more spring ..... That's a common theme for pretty much everyone - me included. More spring, less bar. But more spring and more shock go hand-in-hand so things can get expensive. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted August 18, 2009 Author Share Posted August 18, 2009 In case anyone is still listening I'll add the the tire temp discussion a bit. I've now run an event with the Avons and took over 2 seconds off my previous best time with the Hoosiers. Needless to say I was VERY happy with this but I noticed they are feathering. It's all across the tires and is not real severe but little peaks and valleys instead of a consistent and smooth surface. I didn't notice this as much in the NASA HPDE I ran with them but when I pushed the Avons really hard during a HSAX on track they ended up feathered ... and flat spotted but that's a different story. HSAX is a timed lap from a standing start on a racetrack so obviously they spend most of the lap a relatively low temps and never really fully get up to temp. What can I do to help with this to get the best life and performance out of these tires? Is it a temperature issue where softer or harder compound would work better? PS - I was getting over 1.3 g's peak when I really pushed them. Cameron Quote Link to comment Share on other sites More sharing options...
jt1 Posted August 18, 2009 Share Posted August 18, 2009 My experience is that the feathering shows up when you're really working the tire hard, at the upper limit of it's temp range. It seems to show up more on a hot track with an abrasive surface. With a good set of R6's, I usually see about 1.35-1.38 g's on the datalogger if you disregard the spikes and try to take an average. jt Quote Link to comment Share on other sites More sharing options...
heavy85 Posted August 19, 2009 Author Share Posted August 19, 2009 Interesting. I'm running more in the 1.1 to 1.2 range steady and peak at 1.3 for a couple tenths so maybe there is some more to the A6/R6's. So should I go harder compound on the next set of these Avon tires to help with the feathering or would that just slow me down and I should just live with the wear? Cameron Quote Link to comment Share on other sites More sharing options...
tube80z Posted August 19, 2009 Share Posted August 19, 2009 It's hard to say for sure what you'll need to do for the Avons. You'll need to find someone with first hand knowledge of their care and feeding or do a lot of testing. On a friends EP car it took more spring to turn the GYs on and once that was done the car decimated the track record. Tire temps had been in the 105 to 115 range. Now they are about 180, which is still low according to the GY engineer. All I can say is your LA numbers still look low but that may be track related. On slicks I'd expect to see low 1.4s when everything is sorted and working well. I know you're no longer using the FA tires but your setup wasn't correct for them to work properly. FA tires are designed to be used as half your suspension travel. Until you do that they don't seem to work very well. And I know they are designed for a light car (1380 lbs) but you have to remember those can make 3000 lbs of downforce. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 19, 2009 Share Posted August 19, 2009 Yep. If anything I wish the FA was lighter. If it was 950 lbs and pulled 4 g's under braking that would be closer to the neighborhood of a 2500 lb car pulling 1.5g. As it is the tire is really designed for something that puts more stress on it than our cars can manage. I had that conversation with an engineer when I first started running them. He was worried that the FA only weighed 1300 lbs and thought the tire might debead or something, and I noted that it pulled 4 g's braking and 3+ lateral, and that was good enough for him. Quote Link to comment Share on other sites More sharing options...
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