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With my RWD F-type S I yet to experience any kind of understeer. I'd characterize it as tail-happy for throttle-happy people. Because of that, I don't ever drive it with traction control completely turned off. I just don't trust myself not to get carried away.
We did a figure 8 as part of the HPDE and it was pretty noticeable. Also, keep in mind that you can have understeer at the front AND oversteer at the back, so the presence of one does not mean you don't have the other!!!
I bet the RWD is a helluva lot of fun! Wish I could try one some day to see the difference...
Great write up. Can you tell me where you ordered the meatball from? Is it reusable?
Originally Posted by Matttheboatman
Update: So, I outfitted the car with the Continental ContiForce Contact tires as the stickiest available street tires in OEM sizes. Took the Jag out to my home track of NOLA this weekend. I was soooo looking forward to getting back out on the track. The tires performed very well. No rollover to report, no chucking / and only the front left tire had uneven wear. They delivered a high level of confidence. And, the Jag performed equally as well - no overheating / no transmission issues / no warnings.
My plan this weekend was to compare the Jag to my last car, which was the Porsche Cayman GT4. And, decided if the Jag will run as good as she looks. The Jag performed admirably despite its 900# weight disadvantage. That is like having 4 friends riding in the car - so definately a handicap. Of course, the GT4 is lauded as the best track car of modern times and perhaps rightly so. Nevertheless, the Jag brings 550hp to the game - which is more than most all others.
In summary I would say that Jag is 180 degrees different than the Porsche. I had a bit of a learning curve, and to retrain my brain on braking, turn in, acceleration, and top speed.
Here is what I discovered...
1. Turn-in. The Jag turns in WAYYYY better than the Porsche. Perhaps the extra weight on the front end, or the larger 265s vs 245s tires, or perhaps because of the advanced double wishbone suspension. Or a combination of all. I don't think I ever truly found the limit. The Jag points like no other car I've ever driven. At one point, it felt the computer memorized the course as it seem to go into "auto point" and with very little effort the car was going from cone to cone. I'm smiling.
2. Acceleration. What can you say about 550hp instantaneous. Truly, the fastest car on the straight all weekend. Wow, if I did not have to stop at the end it would continue to build speed all the way.
3. Braking. Not bad, but not good either. It's' not so much the stopping distance, more of the Jag's tendency to bob and weave when coming down from 135+ mph. In close quarters, it can be unnerving. As a I driver I compensated by lifting early, which robs the car of some of its high speed advantage. Perhaps the car would benefit first from stiffer springs.
4. AWD. I found the AWD to be a super-nanny, but in a good way. It does not pull through a corner like a Front Wheel Drive. Instead, it simply keeps the car going straight when you feel like it is about to let go. Kudos to the software engines who designed this system. It works. Flawlessly.
5. Unwinding and High Speed turns. Surprisingly good. Once the car stabilizes past the apex of the turn, I was able to add power smoothly without any wiggle or push. This cat likes to run as long as you don't stomp on its tail. Steady on the power, the car grips very well.
Of course, the Porsche Cayman GT4 has several advantages on the track. The mid engine allows you to maintain higher speeds through the turns, and there is "less going on". Whereas the Jag requires much more abrupt changes in driving styles. Higher speed on the straights, more time braking, aggressive turn in, followed by patience getting back on the power, followed by "lets catch back up" massive power on the straight.
Bottom Line: My best track time with the Jag was 2:09. My best track time with the 385hp GT4 2:01. The Porsche's stickier Cup 2 tires account for maybe 2 seconds of the gap.
The Jag performed flawlessly and the AWD drive delivers confidence. I received a lot of compliments on the car as she was the only Jag out there. Like I say in the mirror each morning, it is great to be so good looking!!!
I have my local sign shop make 'em up. Anyone can make them in ready-to-apply vinyl. They are not reusable. Others do make magnetic ones but they don't stick to aluminum body panels. They should cost you no more than $50 ea.
I'll be running PBIR this Tuesday. From my experience, hot tire pressures provide limited meaningful data. Set your ref cold pressures for balance; check hot for temp spread across tire. Lacking a temp gauge, go with edge rollover. Adjust cold pressures in small increments to get the balance you desire combined with the most uniform temp distributionas you can get. I'm going to start Tues with cold 33 front, 35 rear basd on the posts I've seen. I'll adjust from there. Hopefully I'll get some good gopro data.
Last edited by inmanlanier; 05-13-2017 at 08:51 PM.
Reason: Typos
I'll be running PBIR this Tuesday. From my experience, hot tire pressures provide limited meaningful data. Set your ref cold pressures for balance; check hot for temp spread across tire. Lacking a temp gauge, go with edge rollover. Adjust cold pressures in small increments to get the balance you desire combined with the most uniform temp distributionas you can get. I'm going to start Tues with cold 33 front, 35 rear basd on the posts I've seen. I'll adjust from there. Hopefully I'll get some good gopro data.
33/35 COLD is way to HOT!
You will be in the low 40s when you pit in. Tires will be get super greasy before you are mid way thru your session. Be careful.
I can agree with Matt on tire temps. The sun came out for us for part of the afternoon, and tire temps bumped from 38 to 41, and it was a noticeable drop in grip and braking. Keep em cool if you are on those P Zeros!
It is very subjective to set a number cold that is right. Each track, humidity, outside temperature will have an effect on the proper pressure of the tire. This can be used as a baseline, but I found that a bit more pressure helps with turn-in and elimination of understeer. Could use more track time to try different things, but I think the Zeros will be gone before I get more info.
As you gents likely know, to get the right numbers you need a temp gun to read as you go. What I meant by limited meaningful data was regarding balance of the car. I disagree on your "subjective" observation. We learned the bias front to rear is what sets the balance. We also learned that once you got your cold tire pressures right for a given track, don't deviate - setting the same cold at each track was a very consistent practice. Different tracks were ever so slightly different depending on turns and the like. Hot was too hard to use as reference because it changes so quickly when you come in. Yes, too high in general you'll load up a more narrow piece of the cross-section (and overheat it). I'll take your feedback, however and drop a couple of pounds. Thanks. When we road raced our Mustangs, we were in the high 30s psi. It worked. Other cars, we had lower numbers (my Cobra much lower since the load rating of the tires is far greater than the weight). If I do this again - I'll likely take a gun with me and get some temp data to tweak.
Here are some conditions where you may want to deviate from your standard cold and hot pressure:
rain - better to adjust tires a bit lower on pressure to expand the contact patch and generate more grip
cold ambient temperature - again tires will lilely not get up to desired hot temp, so may consider adding psi to get to ideal hot preasure
abnormally high heat - probably best to reduce cold pressure, as tires will likely end up with more pressure due to expansion from additional heat
humidity - the reason tires change psi is due to the water in the air in your tires. This could change depending on how much humidity is actually in your tires.
tire wear - if you find yourself having uneven wear on the inside or outside, you may want to add pressure to focus contact patch more on the middle of the tire.
Also some tracks will put additional stress on one or more specific tires causing them to heat faster than others. In that case you may want to start with slightly lower pressure in those tires, as the heat will generally cause them to heat to a temp beyond ideal.
These are all subjective, and having the ideal hot pressure is far more important than finding the ideal cold temperature as the tires are running a small percentage at cold temps when on track.
Good points raised. The only one that mattered to us was rain here in the southeast. As stated, we had specifics for different tracks when we road raced. Those differences were small enough that for my track days I never worried from track to track.
I keep hearing an implication about pressures increasing being bad. We learned from the manufacturers that pressure is not of concern. The tires can handle a lot. You simply don't want to overheat them. Temperature distribution is the issue for traction. Don't let it build up in too small a section of the tire.
UPDATE - ran the car yesterday at PBIR. I'm impressed. Porsche makes cars and some of the BMW models can go to a track, be run hard, and do so with aplomb. Not many others have cooling systems or brakes to handle track use running hard. This car did great - no issues at all. I have a 2016 F type R. It was well balanced, the brakes did well (good brake torque), no fade (although some reduction in torque at temps). As I expected, initial tire bite and turn-in strong, but came up to temp quickly and they were not as grippy. I had to adjust line and speeds slightly to accommodate. Only 1 car was keeping with me - a well tricked out Rousch Mustang - I meant to visit him and see what he was running. Are the g-meters accurate on these things? My showed <- 1.06 G and -> 1.114 G peak. I was quite happy. I may tweak the tire pressures up a little next time since there was reasonable rollover. Likely I'll find a gun to shoot temps instead if I can. Overall, very pleased. The beast is quick. I had full traction control on. As I was on occasion pivoting the car (if my entry was a little off), the traction control would step in and bug me. I may start to phase it out with more time behind the wheel at speed. In general, however, the engineers programmed the AWD torque balance well. I just need to soften the nanny a bit.
On the P Zeros I achieved very similar readings on my 16 R AWD. Unfortunately Peak is relatively useless as it usually isn't that close to the sustained number, and for all intensive purposes that is what actually matters... Still, not too shabby! I would guess the sustained would be just over the 1.0 mark.
05-09-2017, 02:09 PM
