The Ariel rocks! Thanks for that link. Btw, I saw one a month or two ago at a car meet in Crystal Cove, but I didn't know what it was.
Quote:
Originally Posted by Lscman
You are wildly extrapolating data from different cars and different drivers and different track tests and different magazine tests and different weather etc in a determined effort to prove your hypothesis (S2 is equal).
1) Yes, I am using data from all over the place. It's the only data available to me, so it's the only data I CAN use. That doesn't mean it's useless or even innacurate. It simply means that it is should not be used to conclusively establish a winner. Which brings me to:
2) READ what I type before you argue with it. If you look at my posts, at no time did I say or even imply that the M5-S2 is equal in overall performance to a C5 Z06. I said it was comperable, meaning not exactly the same as, but close to, that to which it is being compared. And it IS very close to the performance of a Z06, based on all available data. As I've said several times now, and for the last time on this thread, the two vehicles are close enough in overall performance that the driver would be of much greater significance than the performace edge one car might have over the other.
Now, on to details:
Quote:
Originally Posted by Lscman
Heavy cars with marginally-sized tires will fade (read S2), compared to cars weighing 800# less with similar tires.
You are totally correct, in theory, about how weight effects tire performance over time. But to what extent must the cars be driven for the lighter one to have an advantage? 5 minutes? 10? 20? a year and a half? (no, not that last one.) In this case I don't know. What I DO know is that there was no appreciable tire fade during many 1/2 hour driving stints, even on a hot track.
Quote:
Originally Posted by Lscman
In addition, the S2 suspension is much softer than Corvette.
As for the S2 suspension being softer, I doubt it. I've driven both cars (abeit briefly in the case of the Z06) and they seem to have similar ride quality and body roll. Which would mean that the heavier M5-S2 would have stiffer suspension. Obviously this is a subjective comparison on my part, but some internet surfing would certainly turn up the spring and bar rates.
Quote:
Originally Posted by Lscman
Your Elise to Corvette comparison is similarly skewed. For the record, I'm not recommending Corvette over Elise. The 1.6 ton Corvette tire & brake sizing has been proportionally increased over Elise values to manage increased mass and engine torque. Was this done in the S2? NO. The same argument does not hold true for the two ton M5-S2 unless it comes equipped with 15" brakes, 13" wide wheels and 355 tires.
Obviously you are correct, but that has nothing at all to do with what I said. I was making a philisophical point about the irrationality of the human mind. We arbitrarily assign subjective values to objective measurements based on momentary societal norms. We also tend to place higher meaning or definition on round numbers. Why 0-60? Why not 0-71mph as a standard? Because 60 correlates to our delliniation of time? Right now, a 4000lb performance car is heavy, right? Well, who here thinks of the Ferrari Superamerica as a fat boat? It weighs more than an M5! The current trend is bigger, more powerful, and heavier cars - on all fronts. So someday we may look back at an M5 and say, remember when sports cars were as light as that 2 ton sedan? My point: The human mind is as funny as it is fascinating.
One last thought on handling: Weight/tire is not any more important to handling than power/weight is to acceleration. Meaning it is VERY important, but there are other significant factors. The suspension geometry and weight balance come immediately to mind, and they are probably just as important to a car's handling as proper gearing and aerodynamics are to acceleration. This might explain why cars keep getting heavier but often handle better than their predacessors (IE: old Ford GT40 vs. new Ford GT). Anyway, just some food for thought.
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you know what i enjoyed must about the atom's video was the guys face driving it !!!
i think if the pro driver wouldn't have took the one corner wide, that car is as fast as an Enzo !! what a blast to drive for the money .....
i want one !
I can't imgaine going down a highway in that thing though. Great track car. But I would not want to be next to a semi truck in it. He'd never see you and you'd have no chance.
..........As for the S2 suspension being softer, I doubt it. I've driven both cars (abeit briefly in the case of the Z06) and they seem to have similar ride quality and body roll. Which would mean that the heavier M5-S2 would have stiffer suspension. Obviously this is a subjective comparison on my part, but some internet surfing would certainly turn up the spring and bar rates.......
The S2 suspension rates are in the neighborhood of 400f-300r, about 20% more than OEM 540i sport and way lower than Z06 (if wheel rates are compared). Most performance option Vettes produced since 1984 have spring rates about double that & this includes Z51, Z07 and Z06. These S2 cars will see bumpstops on rough triple digit tracks, just like the early C5 non-Z06 Vettes with similarly compliant rates. If bumpstops are not being contacted, it's due to owners dialing in excessive damper settings that will adversely impact tossability. The Dinan S2 rear spring rate is limited by a fundamental requirement for a 12" or longer free spring length. This serious limitation is a result of E39 OEM-spec damper travel & perch design. Dinan front wheel rate is limited by the rear rate (f/r balance). Dinan chose to retain factory perches and the extremely long factory damper travel found in a 520i or similar 5er car, so the ~300#/in rear spring rate barrier was retained. The Dinan S2 spring is designed to fit a Koni with OEM travel spec that bolts to 520i. A stiffer spring allowing proper ride height will simply not remain seated in the OEM spring perches. The factory spring perches require some spring preload & be aware that a 540i sport spring is already so short that it can be installed without a spring compressor. This is why Ground Control and other non-Dinan track solutions for M5 have: 1) special perches that allow zero spring preload at full droop or 2) they shorten damper travel or 3) they raise the upper strut mount to effectively shorten useable travel. To bring M5 wheel spring rates into the same league as Z06, you'd need to exceed M3 track junkie spring rates that are 500+. These cars knock your teeth loose. The 550f/425r Ground Control kits for M5 are somewhat of a compromise (considering the 2 Ton chassis), intended to allow the car to still function as a 4dr sedan with rear occupants. The E36 M3 track junkies run higher rates than that on cars weighing 800# less. The swaybars used on M5 are fairly beefy, but these bars do not manage transient loads (weight transfer) under heavy throttle or brakes. This causes the car to heave about under aggressive maneuvers. Beefy bars are a poor substitute for high rate springs when optimal handling is desired. They work best on a factory skidpad where throttle is held constant.
The S2 suspension rates are in the neighborhood of 400f-300r, about 20% more than OEM 540i sport and way lower than Z06 (if wheel rates are compared). Most performance option Vettes produced since 1984 have spring rates about double that & this includes Z51, Z07 and Z06. These S2 cars will see bumpstops on rough triple digit tracks, just like the early C5 non-Z06 Vettes with similarly compliant rates. If bumpstops are not being contacted, it's due to owners dialing in excessive damper settings that will adversely impact tossability. The Dinan S2 rear spring rate is limited by a fundamental requirement for a 12" or longer free spring length. This serious limitation is a result of E39 OEM-spec damper travel & perch design. Dinan front wheel rate is limited by the rear rate (f/r balance). Dinan chose to retain factory perches and the extremely long factory damper travel found in a 520i or similar 5er car, so the ~300#/in rear spring rate barrier was retained. The Dinan S2 spring is designed to fit a Koni with OEM travel spec that bolts to 520i. A stiffer spring allowing proper ride height will simply not remain seated in the OEM spring perches. The factory spring perches require some spring preload & be aware that a 540i sport spring is already so short that it can be installed without a spring compressor. This is why Ground Control and other non-Dinan track solutions for M5 have: 1) special perches that allow zero spring preload at full droop or 2) they shorten damper travel or 3) they raise the upper strut mount to effectively shorten useable travel. To bring M5 wheel spring rates into the same league as Z06, you'd need to exceed M3 track junkie spring rates that are 500+. These cars knock your teeth loose. The 550f/425r Ground Control kits for M5 are somewhat of a compromise (considering the 2 Ton chassis), intended to allow the car to still function as a 4dr sedan with rear occupants. The E36 M3 track junkies run higher rates than that on cars weighing 800# less. The swaybars used on M5 are fairly beefy, but these bars do not manage transient loads (weight transfer) under heavy throttle or brakes. This causes the car to heave about under aggressive maneuvers. Beefy bars are a poor substitute for high rate springs when optimal handling is desired. They work best on a factory skidpad where throttle is held constant.
This is all very interesting. I have some questions though:
1) Where did you obtain the rate of Dinan's S3 springs? I didn't see them on their website. Note I said S3 with regard to the springs, that's what the S2 package includes: S3 suspension.
2) If the Vette has spring rates double the M5-S2, why doesn't it ride like a stagecoach? With less weight it should have a harsher ride than the M5-S2 even if they ran the same spring rates.
3) With regard to bumpstops, I've driven in excess of 150mph on a fairly bumpy coastal freeway with enough road undulation that the suspension was getting more of a vertical workout than it ever has on a track. Which track(s) are you referring to?
Interesting perspective on the spring rate vs. sway bar size methods.
The S2 suspension rates are in the neighborhood of 400f-300r, about 20% more than OEM 540i sport and way lower than Z06 (if wheel rates are compared). Most performance option Vettes produced since 1984 have spring rates about double that & this includes Z51, Z07 and Z06. These S2 cars will see bumpstops on rough triple digit tracks, just like the early C5 non-Z06 Vettes with similarly compliant rates. If bumpstops are not being contacted, it's due to owners dialing in excessive damper settings that will adversely impact tossability. The Dinan S2 rear spring rate is limited by a fundamental requirement for a 12" or longer free spring length. This serious limitation is a result of E39 OEM-spec damper travel & perch design. Dinan front wheel rate is limited by the rear rate (f/r balance). Dinan chose to retain factory perches and the extremely long factory damper travel found in a 520i or similar 5er car, so the ~300#/in rear spring rate barrier was retained. The Dinan S2 spring is designed to fit a Koni with OEM travel spec that bolts to 520i. A stiffer spring allowing proper ride height will simply not remain seated in the OEM spring perches. The factory spring perches require some spring preload & be aware that a 540i sport spring is already so short that it can be installed without a spring compressor. This is why Ground Control and other non-Dinan track solutions for M5 have: 1) special perches that allow zero spring preload at full droop or 2) they shorten damper travel or 3) they raise the upper strut mount to effectively shorten useable travel. To bring M5 wheel spring rates into the same league as Z06, you'd need to exceed M3 track junkie spring rates that are 500+. These cars knock your teeth loose. The 550f/425r Ground Control kits for M5 are somewhat of a compromise (considering the 2 Ton chassis), intended to allow the car to still function as a 4dr sedan with rear occupants. The E36 M3 track junkies run higher rates than that on cars weighing 800# less. The swaybars used on M5 are fairly beefy, but these bars do not manage transient loads (weight transfer) under heavy throttle or brakes. This causes the car to heave about under aggressive maneuvers. Beefy bars are a poor substitute for high rate springs when optimal handling is desired. They work best on a factory skidpad where throttle is held constant.
This is all very interesting. I have some questions though:
1) Where did you obtain the rate of Dinan's S3 springs? I didn't see them on their website. Note I said S3 with regard to the springs, that's what the S2 package includes: S3 suspension.
2) If the Vette has spring rates double the M5-S2, why doesn't it ride like a stagecoach? With less weight it should have a harsher ride than the M5-S2 even if they ran the same spring rates.
3) With regard to bumpstops, I've driven in excess of 150mph on a fairly bumpy coastal freeway with enough road undulation that the suspension was getting more of a vertical workout than it ever has on a track. Which track(s) are you referring to?
Interesting perspective on the spring rate vs. sway bar size methods.
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