Peak lateral G's....

[Chiketkd]

I lent my G-Tech to AmazonParrot for a few weeks, and decided to get it back this morning to do a little testing with my current suspension set-up:

1) stock springs and struts
2) polyurethane bushings f&r
3) 16x8" RX-7 wheels shod with sticky summer-only 225/50 Dunlop SP Sport 8000 tires (200 treadwear)
4) -0.5 camber front, -0.2 camber rear

Followed the directions in the g-tech booklet, and turned it perfectly sideways across my dashboard and levelled it out to 0.00 g's. I selected the mode for the g-tech to measure peak lateral g's...

http://www.subaru-svx.net/photos/files/Chiketkd/27602.jpg

For the course, I took my car down a tight twisty road (Afton Mtn Road) with a 40mph speed limit and several caution signs advising driver's to navigate turns at 5-20mph... :eek: :rolleyes: :D

Afton Mountain Rd:
http://maps.yahoo.com/maps_result?csz=Afton%2C+VA+22920&state=VA&uzip=22920&ds=n&name=&desc=&lat=38.0237&lon=-78.8465&mlt=38.02842972973&mln=-78.8465&zoomin=yes&BFKey=&mag=2

I decided to go down Afton Mtn rd twice, the first time keeping the car under control, w/o breaking the tires loose (came close a few times). At the end of the first run, the g-tech had recorded a peak lateral g reading of 0.89.

I then repeated the course a second time with the goal of breaking my tires loose. I suceeded three times. Afton Mtn rd is truly an amazing road to drive, and has a good mix of tight off-camber turns as well as a few banked on-camber turns - the peak lateral g-force my g-tech recorded this time around (probably the time I broke all four loose on a banked turn) was 1.01.

http://www.subaru-svx.net/photos/files/Chiketkd/27603.jpg

-Chike

P.S. The error reading on my g-tech pro when recording g forces is + or - 0.1g's. However, I've been able to test its accuracy in measuring acceleration at the dragstrip. On a run where I recorded a 15.21 @ 89.5mph, my g-tech recorded 15.20 @ 91mph. Also, from reading several articles in Road & Track and MotorTrend when they measured instantaneous peak g's when driving along a road course or track, it is very possible for a car (e.g. Honda S2000) to record a peak lateral g reading of 1.0 (or higher) especially if there are a few on-camber banked turns along the course (when the car would record .90g in steady state lateral cornering).

[ensteele]

Wow, the information is interesting, but I would have liked to be there and watch you drive that stretch of raod! :) :)

[SVXRide]

Chike,
For the readings to be 100% accurate you have to stay on level ground (due to the use of accelerometers to make the measurements). I'm guessing you had some "vector addition" going on unless the road had no incline/decline at all.
-Bill
p.s. now, find yourself a big flat parking lot that you can turn into your own personal skid pad....now we're talking!! :D

[Chiketkd]

I decided to use my wife's '02 Lancer ES as the 'control' in my little experiment. It still has the factory Dunlop SP 20 FE M+S tires (treadwear 320) in the 185/65/14 size, comes with only a front sway bar, and is a cute little grocery getter! :D

http://www.subaru-svx.net/photos/files/Chiketkd/27605.jpg

A few magazines (Car & Driver, MotorTrend) have tested her car over the years and recorded lateral g readings of around 0.75-0.78.

I went back to the same Afton Mtn Rd to see what readings I would get...

http://www.subaru-svx.net/photos/files/Chiketkd/27604.jpg

I was able to break her car loose very easily in the turns, and noticed very heavy understeer at the limit. All in all, this car doesn't like to be hustled down a mtn road! :p

The peak lateral g's my g-tech pro recorded with her car (with the front tires understeering heavily at the limit) was 0.72.

http://www.subaru-svx.net/photos/files/Chiketkd/27606.jpg

-Chike

P.S. Bill, it would be nice to find a level parking lot but there aren't too many around here. I'll try to scout a place out and report back! ;) :D

P.P.S. Btw, the highest lateral g's a magazine recorded for an SVX in skidpad testing, was by Motortrend who got 0.92g's in their 9/91 test of a '92 LS-L.

http://www.geocities.com/jamsvx/motortrend2.jpg

[Amazonparrot]

Chike, use the lot up at piedmont college or over at Sams club, both are fairly massive.

-Andrew

[Chiketkd]

Chike, use the lot up at piedmont college or over at Sams club, both are fairly massive.

-Andrew
Piedmont's lot was the one I was thinking of going to - however, I know it's a popular police hang-out. I wouldn't want to attract too much attention! ;)

-Chike

[SVXRide]

Piedmont's lot was the one I was thinking of going to - however, I know it's a popular police hang-out. I wouldn't want to attract too much attention! ;)

-Chike

Just tell them you're from Subaru and you're doing R&D on a 2007 model ;) :D
-Bill

[Chiketkd]

I took SVXRide's advice and went to a level parking lot at Piedmont VA Community College (recommended to me by AmazonParrot).

As it was the 4th of July weekend there was no one around, including the police, and I was able to utilize an entire level section of parking lot... :)

http://www.subaru-svx.net/photos/files/Chiketkd/27626.jpg

I levelled out my g-tech to 0.00g and put it in the mode to measure continuous lateral g's - where you have have to maintain the lateral g reading for a minimum of 3 seconds.

I started out in a clockwise direction (driver's weight on the outside - 170lbs) around the middle of the parking lot and navigated a path to give me a skipad diameter of ~200ft. As I approached the limit of adhesion, I noticed a slight benign understeer, which was easily to modulate. The result - 0.93g's. I then repeated the exercise and got the same result.

http://www.subaru-svx.net/photos/files/Chiketkd/27627.jpg

I then took my car around the skidpad in an anti-clockwise direction (driver's weight on the inside). Once again, I found my SVX very easy to modulate at the limit...and on my back-up run, was able to duplicate the result of 0.97g's.

(camera was at a weird angle when I took this pic)
http://www.subaru-svx.net/photos/files/Chiketkd/27628.jpg

This car is definitely a great handler and corners better than anything I've ever driven to date ('90 300zx TT included)!

-Chike

[SVXRide]

I took SVXRide's advice and went to a level parking lot at Piedmont VA Community College (recommended to me by AmazonParrot).

As it was the 4th of July weekend there was no one around, including the police, and I was able to utilize an entire level section of parking lot... :)

http://www.subaru-svx.net/photos/files/Chiketkd/27626.jpg

I levelled out my g-tech to 0.00g and put it in the mode to measure continuous lateral g's - where you have have to maintain the lateral g reading for a minimum of 3 seconds.

I started out in a clockwise direction (driver's weight on the outside - 170lbs) around the middle of the parking lot and navigated a path to give me a skipad diameter of ~200ft. As I approached the limit of adhesion, I noticed a slight benign understeer, which was easily to modulate. The result - 0.93g's. I then repeated the exercise and got the same result.

http://www.subaru-svx.net/photos/files/Chiketkd/27627.jpg

I then took my car around the skidpad in an anti-clockwise direction (driver's weight on the inside). Once again, I found my SVX very easy to modulate at the limit...and on my back-up run, was able to duplicate the result of 0.97g's.

(camera was at a weird angle when I took this pic)
http://www.subaru-svx.net/photos/files/Chiketkd/27628.jpg

This car is definitely a great handler and corners better than anything I've ever driven to date ('90 300zx TT included)!

-Chike

Chike,
Nice! I may have to take a drive out there to check out what my car will pull with the Hoosiers :cool:
-Bill (could 1.0Gs be in the offering?)

[Chiketkd]

Chike,
Nice! I may have to take a drive out there to check out what my car will pull with the Hoosiers :cool:
-Bill (could 1.0Gs be in the offering?)
Bill,

I'll bring my g-tech to the Subaru Challenge meet in September. I'm sure the parking lot area will be large enough for us to do a little testing on the side! ;)

Btw, I'm sure 1.0g is not out of the question for the mods you have done with your car! ;)

-Chike

P.S. I must say, after all this spirited driving over the last two days, I have a serious pain in my neck that won't go away. Ouch! :(

[Chiketkd]

http://www.subaru-svx.net/photos/files/Chiketkd/27626.jpg
Bill,

You might be able to see in this pic that the center caps from my RX-7 wheels are missing (similar to what you did). I finally got tired of people asking me if my car was some kinda weird Mazda and popped them out this weekend (as I had some free time on my hands). However, I painted the inner axle caps a nice silver color to make the absence of the caps less noticeable... :)

-Chike

[Matthewmongan]

i feel you on that. every other week since the meet i have had to drive a 96? olds 88. that car is so soft the first week i had the suspension checked out. i've goten used to the balls deep stiffness of the svx over the past few years that normal cars i drive feel impotent. i transed a ferrari 355 for an import dealor in baltimore county that was comparible in firmness to the svx, most of the high ends i got to drive were eather too hard or too soft.

[Chiketkd]

i feel you on that. every other week since the meet i have had to drive a 96? olds 88. that car is so soft the first week i had the suspension checked out. i've goten used to the balls deep stiffness of the svx over the past few years that normal cars i drive feel impotent. i transed a ferrari 355 for an import dealor in baltimore county that was comparible in firmness to the svx, most of the high ends i got to drive were eather too hard or too soft.
Matt,

I can't say I've ever had the opportunity to drive a Ferrari 355 before - but it's pretty cool to hear that the ride quality is similar to an SVX. I'm pretty happy with the way my car is currently set-up in the handling department, but I would definitely like to add some custom springs from Mychailothat'll keep the stock ride height, but stiffen the ride some more. This'll help dial-out some slight body-roll I've noticed...and hopefully push my car closer to the 1.0g mark! :)

I must say, the sticky rubber and adjustment to camber have probably had the biggest effect in improving cornering. Popular tires like Pirelli P Zero Nero M+S are great all-season rubber, but with a tread wear of 400, wouldn't be the stickiest in the turns...

-Chike

[Matthewmongan]

whats a good wet dry tire. in salisbury i have no need for all season as it doesnt snow.

[Matthewmongan]

Matt,

I can't say I've ever had the opportunity to drive a Ferrari 355 before - but it's pretty cool to hear that the ride quality is similar to an SVX. I'm pretty happy with the way my car is currently set-up in the handling department, but I would definitely like to add some custom springs from Mychailothat'll keep the stock ride height, but stiffen the ride some more. This'll help dial-out some slight body-roll I've noticed...and hopefully push my car closer to the 1.0g mark! :)

-Chike

the bigest diference between the f355 and the svx was body roll. you can really feel that the svx wants to andle better but when the 3500lbs body starts to lean the tires follow suite. i think harder springs and some nice "low pro" tires with thick side walls will help out. personaly i wouldnt lower the car because it will f up the geometry of the suspension.

[SVXRide]

Chike,
Looked back at your original post and the fact that you're running tires with a treadwear rating of 200 explains a lot -- they are pretty "sticky" for street tires! Looks like SCCA is actually going to raise the treadwear requirement on their "street tire" class to 140 (or is it 160?) for next year. The Azenis that most folks are running this year have a treadwear rating of 120. If I remember right, the Yokohama ES100s I'm running on the street have a rating of 300 - not exactly as sticky as my race Hoosiers with their rating of 40 :eek:
-Bill

[benebob]

Actually, I think the original Azenis were 180 (which translates into about 10k). Granted I think Chike has single A traction and temp ratings rather than the double A that most race and ultra high performance tires have but it still is much more than the OEM tire by far.

[Chiketkd]

Actually, I think the original Azenis were 180 (which translates into about 10k). Granted I think Chike has single A traction and temp ratings rather than the double A that most race and ultra high performance tires have but it still is much more than the OEM tire by far.
Correct Ben - my Dunlop's have a single 'A' rating for traction and temperature. I actually think the 295/45 Goodyear F1 supercar tires on my former SVT Lightning had a double 'AA' rating for traction.

However, the treadwear rating of 200 does explain a good deal as to why my car sticks to the road like glue when the g-loads climb.

I really love the Dunlop SP Sport 8000's and I can get them for pretty cheap as they're the previous model from Dunlop in their line of max performance summer tires (current model is the SP Sport 9000). The tirerack actually rates the 8000's higher than the newer 9000's...

http://www.tirerack.com/tires/tests/sp9000_rd.jsp

-Chike

[Chiketkd]

the bigest diference between the f355 and the svx was body roll. you can really feel that the svx wants to andle better but when the 3500lbs body starts to lean the tires follow suite. i think harder springs and some nice "low pro" tires with thick side walls will help out. personaly i wouldnt lower the car because it will f up the geometry of the suspension.
I can see that. The SVX is definitely very hefty, and the chassis always seems to take a 'set' just a few ticks behind the suspension. That's why weight reduction is so important in these cars if you have intentions to race...

Mychailo can make custom springs which won't lower the ride height, and stiffen up the spring rates. I can wait to install them when I get the extra money this Xmas! :)

-Chike

P.S. To answer your other question - if money isn't a factor, the best wet/dry tire out there IMHO is the Bridgestone Potenza S-03 pole position. They cost just a hair over $200 each but grip like no other in the wet or dry! :cool:

[benebob]

P.S. To answer your other question - if money isn't a factor, the best wet/dry tire out there IMHO is the Bridgestone Potenza S-03 pole position. They cost just a hair over $200 each but grip like no other in the wet or dry! :cool:

We need to get you on a set of R compounds. Just wear a diaper! :eek: Actually I'd say your best bet now for non R compounds I'd go with the new Azenis. Should cost about $100 or so per tire. Granted you'll only get about 10k out of them but I'm guessing that's what will go on mine next.

As for lowering. No messing up geometrics so long as you do it right. You can actually use it to your advantage with camber that Subies shouldn't have! :D

[SVXRide]

We need to get you on a set of R compounds. Just wear a diaper! :eek: Actually I'd say your best bet now for non R compounds I'd go with the new Azenis. Should cost about $100 or so per tire. Granted you'll only get about 10k out of them but I'm guessing that's what will go on mine next.

As for lowering. No messing up geometrics so long as you do it right. You can actually use it to your advantage with camber that Subies shouldn't have! :D

Ben,
You going to shave down (5/32) a set of 615s? :eek: :D
-Bill

[benebob]

Ben,
You going to shave down (5/32) a set of 615s? :eek: :D
-Bill

Naw, I was talking about my street car that is currently sitting on half rotten A540s with more than enough life left in 'em aside from the cracks. Might as well pay less per tire, get more out of 'em performance wise and actually get rid of tires that should be thrown out.

[ThetaReactor]

Correct Ben - my Dunlop's have a single 'A' rating for traction and temperature. I actually think the 295/45 Goodyear F1 supercar tires on my former SVT Lightning had a double 'AA' rating for traction.

However, the treadwear rating of 200 does explain a good deal as to why my car sticks to the road like glue when the g-loads climb.

I really love the Dunlop SP Sport 8000's and I can get them for pretty cheap as they're the previous model from Dunlop in their line of max performance summer tires (current model is the SP Sport 9000). The tirerack actually rates the 8000's higher than the newer 9000's...

http://www.tirerack.com/tires/tests/sp9000_rd.jsp

-Chike

How does that work? I'd imagine a lower treadwear rating [sticky] would generally indicate a better traction rating. My tires are AA rated for traction, but they're 280 treadwear.

[benebob]

How does that work? I'd imagine a lower treadwear rating [sticky] would generally indicate a better traction rating. My tires are AA rated for traction, but they're 280 treadwear.


Each manufacture rates their own BUT they must put a rating on it. Hence Bridgestone may say blank tire has a rating of 400 for a 40k tire where Dunlop might rate theirs at 380 for a 50k tire. In other words they don't mean much except for generalization. Of course SVXride's Hoosiers with a 40 rating aren't gonna live as long as a 400 rated tire from anybody. The traction and temp ratings though to my knowledge are universal.

[ThetaReactor]

So Kumho is just being very generous in estimating the life expectancy of my rubber...

[benebob]

So Kumho is just being very generous in estimating the life expectancy of my rubber...

Not necessarly, 280 IMO would be good for about 15-20k. The double AA is what I'd look for in both temp and traction. If just in traction you'll definately cook your tires at an autox in 90 degree weather after the 2nd hard run. Just fine for the street but not ideal on a track. I think the Potenza RE-92s I had on my Impreza from new had a rating of like 380 and I got 60k even out of them!

[ThetaReactor]

These tires were a compromise, anyhow. They're quieter, wear better, and handle the rain better than the super-sticky Yokohamas I did have. And they were about $100 cheaper [each] than the BF Goodrich KDW 2s that I'd been considering. I'm not racing anytime soon, so I'm quite happy to emphasize the "touring" bits of the car.

[Chiketkd]

Each manufacture rates their own BUT they must put a rating on it. Hence Bridgestone may say blank tire has a rating of 400 for a 40k tire where Dunlop might rate theirs at 380 for a 50k tire. In other words they don't mean much except for generalization. Of course SVXride's Hoosiers with a 40 rating aren't gonna live as long as a 400 rated tire from anybody. The traction and temp ratings though to my knowledge are universal.
Ben,

I'm wondering if the traction and temp ratings are relative as well??? :confused: In the Tirerack test I linked higher-up on this page:

http://www.tirerack.com/tires/tests/sp9000_rd.jsp

They compare the new Dunlop SP Sport 9000's to the previous SP Sport 8000's. The new 9000's have a treadwear of 280 and double 'AA' rating for traction - while the 8000's have a treadwear of 200 and a single 'A' rating for traction.

In their testing, the 8000's got better ratings in every handling/braking test they did, with the 9000's only shining in road comfort/noise level...

They also noted about the 8000's: "We have recommended the SP Sport 8000 for drivers who have the need of a dual purpose street and driver's school track tire. While it can't match the lap times of today's DOT-Legal competition tires, it provides a lot of performance and durability."

I find it hard to believe that the SP Sport 8000 would get their recommendation as a good street/track tire, if the single 'A' rating for traction & temp caused the tires to be cooked after a few hot laps on a summer day???

-Chike

[benebob]

Ben,

I'm wondering if the traction and temp ratings are relative as well??? :confused: In the Tirerack test I linked higher-up on this page:

http://www.tirerack.com/tires/tests/sp9000_rd.jsp

They compare the new Dunlop SP Sport 9000's to the previous SP Sport 8000's. The new 9000's have a treadwear of 280 and double 'AA' rating for traction - while the 8000's have a treadwear of 200 and a single 'A' rating for traction.

In their testing, the 8000's got better ratings in every handling/braking test they did, with the 9000's only shining in road comfort/noise level...

They also noted about the 8000's: "We have recommended the SP Sport 8000 for drivers who have the need of a dual purpose street and driver's school track tire. While it can't match the lap times of today's DOT-Legal competition tires, it provides a lot of performance and durability."

I find it hard to believe that the SP Sport 8000 would get their recommendation as a good street/track tire, if the single 'A' rating for traction & temp caused the tires to be cooked after a few hot laps on a summer day???

-Chike


To my knowledge they are based on Gov't standards. What those standard are I don't know. Typically a AA tire will overheat heat up as fast but then each manufacture uses different compounds (like an autox and road racing compound for instance). As for the 8000 being a better tire. That may be. Look at the Yoko A540 vs the 550. The A540 is a much better tire then the 550 ever could be. It was also about a 1/3 pricier. Just because one is a replacement doesn't make it better. Just different and if it corner's a market or gets enough sales from the previous tire then the bean counters are happy. Personally, I don't see the need for a AA tire for the street in most cases but its like faulting someone from buying top of the line Michelin's for $200 when they could've put 3 Sumitomo's on for that price.
As for cooking tires. I'll cook anyone's tires in a lap or two on a warm day. Just give me the chance!!! :D

[ilsegretosvx]

I have the 8000s on stock rims and would buy them again. Flip side not much experience in the wet, I'm in California :p

[Chiketkd]

As for cooking tires. I'll cook anyone's tires in a lap or two on a warm day. Just give me the chance!!! :D
Ha ha! Looking at the way the racer takes the corners, I'm sure any tire will be cooked in no time! :eek:

-Chike

[Chiketkd]

I have the 8000s on stock rims and would buy them again. Flip side not much experience in the wet, I'm in California :p
I love the SP Sport 8000 tire and just bought some more. Tirerack now sells them for $118 which is a downright steal.

Dunlop SP Sport 8000
http://www.tirerack.com/images/tires/dunlop/du_sp_sport_8000.jpg


However, I really like the Potenza S-03 pole position tires and would love to pick-up a set someday.

-Chike

[benebob]

Ha ha! Looking at the way the racer takes the corners, I'm sure any tire will be cooked in no time! :eek:

-Chike

Oh that's MUCH better than my red 95 with the koni's on does on the track :D . First time I autoxed it I took a 1/4 inch off the outside corner of my A540s

[Chiketkd]

First time I autoxed it I took a 1/4 inch off the outside corner of my A540s
That's just insane! :eek: :eek: :eek:

-Chike

[SVXRide]

Oh that's MUCH better than my red 95 with the koni's on does on the track :D . First time I autoxed it I took a 1/4 inch off the outside corner of my A540s


Tire pressure, Ben, think tire pressure :D :D
-Bill

[Chiketkd]

Tire pressure, Ben, think tire pressure :D :D
-Bill
Amen. I currently run about 40 psi front, 36 rear - and my tires still look pretty good even after all the canyon carving and skidpad stuff I did last weekend! :) (which is another thing I like about the SP Sport 8000 - they have a reinforced sidewall to reduce flex in high g cornering)

-Chike

[benebob]

Tire pressure, Ben, think tire pressure :D :D
-Bill


50, 47? I could run the Dragon for weeks with what I'd take off in one autox on street tires. Buicks just aren't made for autoxing.

[Chiketkd]

Yeah Bill, what are your magic tire pressures when you autoX? :)

-Chike

[benebob]

Yeah Bill, what are your magic tire pressures when you autoX? :)

-Chike


There is no magic pressure. It'll change by temp, weather, humidity, track surface, course set up, course distance, the tires you are running plus about 100 other factors. Bill simply plugs 'em into his rocket computer and out comes what he should run :D