xkrs vs mercedes sc63 amg evo track battle
#41
03-15-2014, 01:18 PM
Albert,
The video was from a track I hadn't driven in many years, and just the second time ever, and the first time in the XKR. Driving aggression is just an average around a track, and where I'd describe that video as driven at just 7/10ths, some more dangerous high speed sweepers were taken a notch or two down, and in safer corners I was able to push to the limits of adhesion and beyond. My home track I know like the back of my hand, and I've been able to track it on the limit with all nannies turned off. The car is completely predictable and controllable at the limit, at my skill level, with only a few days of track seat time in it. I have not whitewashed or denied any handling issues, I simply have not experienced them... even at the times and places where I could push to 10/10ths. I'm confident that if you were to track yours you would feel the same, but until then you're just limited to interpretting the limited feedback of others.
Please post the XKR track review that you feel indicates the traction problem you're trying to resolve. I feel the weak link in the stock suspension's ability to maximize tire grip is the damper's valving. A damper designed for, or more suitable for track use will greatly improvement its ability to keep the tire planted where a damper with different characteristics will make the car skittish, and create the same grip and handling issues as a suspension that is over-sprung or barred.
An example of this can be seen when comparing coilovers from a company like Tein, where they pair different quality of dampers with the same spring, and the resulting performance is dramatically different. On the Supra I used a double adjustable monotube race damper with custom valving and Eibach race springs. The big surprise was that even though I had gone to much higher spring rates (800f/500r) the ride quality was significantly improved on rougher roads, and similar to what someone might expect from a softer rear spring...not a firmer one. In Max's case he's already bought his coilovers, and damper dyno graphs and custom valving is likely not available, and they may not be adjustable either for rebound or compression. I don't believe that changes to springs or bars will be as effective at improving tire grip as an improvement or tuning of his dampers, and I'm not sure they will actually improve it at all based on my experience driving it on the three tracks.
I'm going to wait for his track feedback with his unique set-up, and it'll be interesting to see how he can improve on it. Hopefully this exchange will help him
Bruce
The video was from a track I hadn't driven in many years, and just the second time ever, and the first time in the XKR. Driving aggression is just an average around a track, and where I'd describe that video as driven at just 7/10ths, some more dangerous high speed sweepers were taken a notch or two down, and in safer corners I was able to push to the limits of adhesion and beyond. My home track I know like the back of my hand, and I've been able to track it on the limit with all nannies turned off. The car is completely predictable and controllable at the limit, at my skill level, with only a few days of track seat time in it. I have not whitewashed or denied any handling issues, I simply have not experienced them... even at the times and places where I could push to 10/10ths. I'm confident that if you were to track yours you would feel the same, but until then you're just limited to interpretting the limited feedback of others.
Please post the XKR track review that you feel indicates the traction problem you're trying to resolve. I feel the weak link in the stock suspension's ability to maximize tire grip is the damper's valving. A damper designed for, or more suitable for track use will greatly improvement its ability to keep the tire planted where a damper with different characteristics will make the car skittish, and create the same grip and handling issues as a suspension that is over-sprung or barred.
An example of this can be seen when comparing coilovers from a company like Tein, where they pair different quality of dampers with the same spring, and the resulting performance is dramatically different. On the Supra I used a double adjustable monotube race damper with custom valving and Eibach race springs. The big surprise was that even though I had gone to much higher spring rates (800f/500r) the ride quality was significantly improved on rougher roads, and similar to what someone might expect from a softer rear spring...not a firmer one. In Max's case he's already bought his coilovers, and damper dyno graphs and custom valving is likely not available, and they may not be adjustable either for rebound or compression. I don't believe that changes to springs or bars will be as effective at improving tire grip as an improvement or tuning of his dampers, and I'm not sure they will actually improve it at all based on my experience driving it on the three tracks.
I'm going to wait for his track feedback with his unique set-up, and it'll be interesting to see how he can improve on it. Hopefully this exchange will help him
Bruce
#42
03-15-2014, 02:43 PM
Veteran Member
.
Albert,
The video was from a track I hadn't driven in many years, and just the second time ever, and the first time in the XKR. Driving aggression is just an average around a track, and where I'd describe that video as driven at just 7/10ths, some more dangerous high speed sweepers were taken a notch or two down, and in safer corners I was able to push to the limits of adhesion and beyond. My home track I know like the back of my hand, and I've been able to track it on the limit with all nannies turned off. The car is completely predictable and controllable at the limit, at my skill level, with only a few days of track seat time in it. I have not whitewashed or denied any handling issues, I simply have not experienced them... even at the times and places where I could push to 10/10ths. I'm confident that if you were to track yours you would feel the same, but until then you're just limited to interpretting the limited feedback of others.
Yes, I am simply interpreting the feedback from the pros, as well as the poor lap times shown by the XKR family. I don't have a video on the plain XKR but, there are plenty for the XKR-S, which is basically suspended using the same philosophy. For the base XKR I have to be content to point to laptimes, such as at VIR where that '10 XKR was a full 5 seconds behind a Chevy Camaro and a number of other lesser brands.
Virginia International Raceway lap records - FastestLaps.com
As I mentioned already, I have no intentions forf tracking my XKR or even taking it near the limit on the streets, therefore, I am quite satisfied with its stock performance. Yet, from the available lap times, video evidence we it would be difficult to deny that the suspension is simply not hooking up on the track. It "could be" damper issues, of course, just that my experience throws up the red flag when I see overly stiff springs, particularly when the rear springs are higher rate than the fronts. I am not sure what Jaguar was thinking but, that goes entirely against everything I know about setting up a front engined car.
Please post the XKR track review that you feel indicates the traction problem you're trying to resolve. I feel the weak link in the stock suspension's ability to maximize tire grip is the damper's valving. A damper designed for, or more suitable for track use will greatly improvement its ability to keep the tire planted where a damper with different characteristics will make the car skittish, and create the same grip and handling issues as a suspension that is over-sprung or barred.
I had found in my experience that most damper issues are rebound issues and not compression problems. I raced cars with dampers that were dual adjustable as well as ones that were only rebound adjustable. Rebound is, by far, the most important of the two. Now, if you watch, Randy Pobst coming out of the Corkscrew at Laguna on the video posted on Page1 of this tread, he is in heavy compression mode, having dropped off from the top of the hill into a lower portion of the turn. At this point the weight of the car should be pressing down, pushing the tires into the pavement for traction. Yet, the rear-end is literally "skating" as if on ice. Is that a damper issue? In that particular instance I doubt it. There is not enough weight transfer onto the accelerating tires. Why? Again, I find it easiest to suspect the springs that are too high rate to allow for the needed weight transfer and compression to happen. An other possibility is that the driver was incompetent by applying too much power but, I think that we can toss that theory with Randy at the wheel. It was not a predictable power oversteer, of which Randy would be in charge of. It was pure, hair-rising, "skating", (it got to my stomach juices flowing, just from watching it) which is why he declared the XKR-S as: "the most likely car to be spun on the race track".
An example of this can be seen when comparing coilovers from a company like Tein, where they pair different quality of dampers with the same spring, and the resulting performance is dramatically different. On the Supra I used a double adjustable monotube race damper with custom valving and Eibach race springs. The big surprise was that even though I had gone to much higher spring rates (800f/500r) the ride quality was significantly improved on rougher roads, and similar to what someone might expect from a softer rear spring...not a firmer one. In Max's case he's already bought his coilovers, and damper dyno graphs and custom valving is likely not available, and they may not be adjustable either for rebound or compression. I don't believe that changes to springs or bars will be as effective at improving tire grip as an improvement or tuning of his dampers, and I'm not sure they will actually improve it at all based on my experience driving it on the three tracks.
I'm going to wait for his track feedback with his unique set-up, and it'll be interesting to see how he can improve on it. Hopefully this exchange will help him
Again, if Max, or any XKR owner, is smart he will not take his XKR to anywhere close to the limits on any race track and, instead, learn from the mistakes of people who have; like me, having crashed a Lamborghini at Laguna Seca (yeap, right at Corkscrew) and my first twin turbo RX-7 at Sears point (hairpin, turn 7), exactly because I was trying to set the fastest lap of the day in both instances. If someone REALLY wants to race, get a real, dedicated race car; it will be far cheaper, far faster and far easier to repair after a crash. You crash an XKR and the car will never recover from it, even if the driver may.
Bruce
The video was from a track I hadn't driven in many years, and just the second time ever, and the first time in the XKR. Driving aggression is just an average around a track, and where I'd describe that video as driven at just 7/10ths, some more dangerous high speed sweepers were taken a notch or two down, and in safer corners I was able to push to the limits of adhesion and beyond. My home track I know like the back of my hand, and I've been able to track it on the limit with all nannies turned off. The car is completely predictable and controllable at the limit, at my skill level, with only a few days of track seat time in it. I have not whitewashed or denied any handling issues, I simply have not experienced them... even at the times and places where I could push to 10/10ths. I'm confident that if you were to track yours you would feel the same, but until then you're just limited to interpretting the limited feedback of others.
Yes, I am simply interpreting the feedback from the pros, as well as the poor lap times shown by the XKR family. I don't have a video on the plain XKR but, there are plenty for the XKR-S, which is basically suspended using the same philosophy. For the base XKR I have to be content to point to laptimes, such as at VIR where that '10 XKR was a full 5 seconds behind a Chevy Camaro and a number of other lesser brands.
Virginia International Raceway lap records - FastestLaps.com
As I mentioned already, I have no intentions forf tracking my XKR or even taking it near the limit on the streets, therefore, I am quite satisfied with its stock performance. Yet, from the available lap times, video evidence we it would be difficult to deny that the suspension is simply not hooking up on the track. It "could be" damper issues, of course, just that my experience throws up the red flag when I see overly stiff springs, particularly when the rear springs are higher rate than the fronts. I am not sure what Jaguar was thinking but, that goes entirely against everything I know about setting up a front engined car.
Please post the XKR track review that you feel indicates the traction problem you're trying to resolve. I feel the weak link in the stock suspension's ability to maximize tire grip is the damper's valving. A damper designed for, or more suitable for track use will greatly improvement its ability to keep the tire planted where a damper with different characteristics will make the car skittish, and create the same grip and handling issues as a suspension that is over-sprung or barred.
I had found in my experience that most damper issues are rebound issues and not compression problems. I raced cars with dampers that were dual adjustable as well as ones that were only rebound adjustable. Rebound is, by far, the most important of the two. Now, if you watch, Randy Pobst coming out of the Corkscrew at Laguna on the video posted on Page1 of this tread, he is in heavy compression mode, having dropped off from the top of the hill into a lower portion of the turn. At this point the weight of the car should be pressing down, pushing the tires into the pavement for traction. Yet, the rear-end is literally "skating" as if on ice. Is that a damper issue? In that particular instance I doubt it. There is not enough weight transfer onto the accelerating tires. Why? Again, I find it easiest to suspect the springs that are too high rate to allow for the needed weight transfer and compression to happen. An other possibility is that the driver was incompetent by applying too much power but, I think that we can toss that theory with Randy at the wheel. It was not a predictable power oversteer, of which Randy would be in charge of. It was pure, hair-rising, "skating", (it got to my stomach juices flowing, just from watching it) which is why he declared the XKR-S as: "the most likely car to be spun on the race track".
An example of this can be seen when comparing coilovers from a company like Tein, where they pair different quality of dampers with the same spring, and the resulting performance is dramatically different. On the Supra I used a double adjustable monotube race damper with custom valving and Eibach race springs. The big surprise was that even though I had gone to much higher spring rates (800f/500r) the ride quality was significantly improved on rougher roads, and similar to what someone might expect from a softer rear spring...not a firmer one. In Max's case he's already bought his coilovers, and damper dyno graphs and custom valving is likely not available, and they may not be adjustable either for rebound or compression. I don't believe that changes to springs or bars will be as effective at improving tire grip as an improvement or tuning of his dampers, and I'm not sure they will actually improve it at all based on my experience driving it on the three tracks.
I'm going to wait for his track feedback with his unique set-up, and it'll be interesting to see how he can improve on it. Hopefully this exchange will help him
Again, if Max, or any XKR owner, is smart he will not take his XKR to anywhere close to the limits on any race track and, instead, learn from the mistakes of people who have; like me, having crashed a Lamborghini at Laguna Seca (yeap, right at Corkscrew) and my first twin turbo RX-7 at Sears point (hairpin, turn 7), exactly because I was trying to set the fastest lap of the day in both instances. If someone REALLY wants to race, get a real, dedicated race car; it will be far cheaper, far faster and far easier to repair after a crash. You crash an XKR and the car will never recover from it, even if the driver may.
Bruce
Last edited by axr6; 03-15-2014 at 02:47 PM.
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