| 4x4 All Terrain Tire SHOOTOUT |
Skid Pad Test - Asphalt, Big Bear Airport
A skid pad is a circle course of a given radius, usually a radius of 100 feet. For our test, with limited
space, we set up a 75 foot radius circle. The skid pad test is used to determine two important vehicle
characteristics. The first is overall traction. This is measured as lateral acceleration and is determined
by timing one full lap of the circle, one in each direction, The lap times can then be converted to a
lateral “G” force, which is a measure of total average traction. The second measure is both visual and
subjective from the driver and determines the realative traction of the front vs. the rear tires, or the
handling balance of the vehicle. If the front tires loose traction firsat, it is called understeer or the more
common term of push. When the rear looses traction first, it is oversteer or loose.
In the case of modern SUVs, and virtually every car manufatured in the world, the design calls for light to
moderate understeer, since it more stable, easier to control and requires a reduction in speed to control,
which is the more intuitive response from the driver. Oversteer requires applying more power, which nis
counter-intuitive for most drivers. The Land Rover Discovery used in the test is completely stock. Each
of the three tires were run at identical manufacturer-recommended tire pressures. Since thre tires were
oversized for the stock Rover (which was not lifted like our off road test version), we had some tire rub
issues which damges the tire tread edges on all of the tires, but in varying amounts. This was minor and
not really a concern from a safety or durability issue. Other damge was caused to the treads of the tires
in vaying degrees due to the abuse of driving at the limits of traction.
Tires have a significant effect on handling balance. In this case, all three tires exhibited understeer, but
in widely varying amounts. It is obvious in the video clip. Watch the amount the front wheels are turned
to stay on the circle path. More front wheel steering lock means more understeer and more tire scrub
(which relates to increased wear). Also watch the ability of the tire to hold a line close to the traffic cones.
Closer to the cones means less understeer, better grip and less tire scrub. Also listen to the level of tire
squeal. More noise usually means less traction and larger degrees of steering lock at the front. Also
listen for a chattering noise. Tire chatter while cornering at the traction limit is usually a function of
sidewall design where the tire tread flexes the sidewall until some grip is lost for an instant, then flexes
back, regaining grip. This process reoccurs very rapidly until either speed is reduced or steering lock is
reduced, or both. This characteristic causes a reduction in overall grip and can cause damage to the
edge of the tread at the sidewall interface. To be fair to the BFGs, often a tire pressure adjustment can
reduce or eliminate tire chatter. Since we were on a very tight testing schedule, it was not possible to
make adjustment to any of the tires for the testing.
SKID PAD TIMES & "G" FORCE
The lap times for each tire indicate the total amount of grip or traction, which includes handling balance,
which functions as a factor in the total grip available.
BFG run one clockwise: 12.73 counterclockwise: 12.43 two way average lateral "G": 0.581
Toyo clockwise: 12.57 counterclockwise: 12.30 two way average lateral "G": 0.590
Hankook clockwise: 12.50 counterclockwise: 12.10 two way average lateral "G": 0.608
BFG run two clockwise: 12.63 counterclockwise: 12.40 two way average lateral "G": 0.587
The low lateral "G"s are due to cold asphalt temperatures, a very tight radius circle and the Land Rover
Discovery handling characteristics.
The Hankooks were faster, meaning more grip, but at the lowest slip angles, meaning more control and
better wear characteristics.
Hankooks were much easier to drive.
TIRE TREAD IMAGES ON VIDEO
The cuts in the tread blocks on all three tires were caused by rubbing of the fender against the the tire.
The BFGs showed the most damage, the Hankoks the least. This not a flaw in the tires but due to fit. The
BFGs have a more square shoulder than the Toyo or Hankook, so they interfered with the tfender well
edge more, resulting more damage. The damgae to the tread blocks in the second set of close-ups was
caused by the tire tread scrub on the skid pad and slalom. The BFGs show some damge, mostly due to
excessive understeer and tire chatter. The Toyos sohow some damage and the Hankooks virtually no
damage.
SKID PAD TIRE TRACK IMAGES ON VIDEO
These images show the rubber laid down on the skid pad. The darest marks are from the BFG. Also not
the path of the dark marks, farther away from the circle radius than the others. Also note the chatter
marks on these tracks. The Hankooks had the lightest marks, meaning less tire scrub.
space, we set up a 75 foot radius circle. The skid pad test is used to determine two important vehicle
characteristics. The first is overall traction. This is measured as lateral acceleration and is determined
by timing one full lap of the circle, one in each direction, The lap times can then be converted to a
lateral “G” force, which is a measure of total average traction. The second measure is both visual and
subjective from the driver and determines the realative traction of the front vs. the rear tires, or the
handling balance of the vehicle. If the front tires loose traction firsat, it is called understeer or the more
common term of push. When the rear looses traction first, it is oversteer or loose.
In the case of modern SUVs, and virtually every car manufatured in the world, the design calls for light to
moderate understeer, since it more stable, easier to control and requires a reduction in speed to control,
which is the more intuitive response from the driver. Oversteer requires applying more power, which nis
counter-intuitive for most drivers. The Land Rover Discovery used in the test is completely stock. Each
of the three tires were run at identical manufacturer-recommended tire pressures. Since thre tires were
oversized for the stock Rover (which was not lifted like our off road test version), we had some tire rub
issues which damges the tire tread edges on all of the tires, but in varying amounts. This was minor and
not really a concern from a safety or durability issue. Other damge was caused to the treads of the tires
in vaying degrees due to the abuse of driving at the limits of traction.
Tires have a significant effect on handling balance. In this case, all three tires exhibited understeer, but
in widely varying amounts. It is obvious in the video clip. Watch the amount the front wheels are turned
to stay on the circle path. More front wheel steering lock means more understeer and more tire scrub
(which relates to increased wear). Also watch the ability of the tire to hold a line close to the traffic cones.
Closer to the cones means less understeer, better grip and less tire scrub. Also listen to the level of tire
squeal. More noise usually means less traction and larger degrees of steering lock at the front. Also
listen for a chattering noise. Tire chatter while cornering at the traction limit is usually a function of
sidewall design where the tire tread flexes the sidewall until some grip is lost for an instant, then flexes
back, regaining grip. This process reoccurs very rapidly until either speed is reduced or steering lock is
reduced, or both. This characteristic causes a reduction in overall grip and can cause damage to the
edge of the tread at the sidewall interface. To be fair to the BFGs, often a tire pressure adjustment can
reduce or eliminate tire chatter. Since we were on a very tight testing schedule, it was not possible to
make adjustment to any of the tires for the testing.
SKID PAD TIMES & "G" FORCE
The lap times for each tire indicate the total amount of grip or traction, which includes handling balance,
which functions as a factor in the total grip available.
BFG run one clockwise: 12.73 counterclockwise: 12.43 two way average lateral "G": 0.581
Toyo clockwise: 12.57 counterclockwise: 12.30 two way average lateral "G": 0.590
Hankook clockwise: 12.50 counterclockwise: 12.10 two way average lateral "G": 0.608
BFG run two clockwise: 12.63 counterclockwise: 12.40 two way average lateral "G": 0.587
The low lateral "G"s are due to cold asphalt temperatures, a very tight radius circle and the Land Rover
Discovery handling characteristics.
The Hankooks were faster, meaning more grip, but at the lowest slip angles, meaning more control and
better wear characteristics.
Hankooks were much easier to drive.
TIRE TREAD IMAGES ON VIDEO
The cuts in the tread blocks on all three tires were caused by rubbing of the fender against the the tire.
The BFGs showed the most damage, the Hankoks the least. This not a flaw in the tires but due to fit. The
BFGs have a more square shoulder than the Toyo or Hankook, so they interfered with the tfender well
edge more, resulting more damage. The damgae to the tread blocks in the second set of close-ups was
caused by the tire tread scrub on the skid pad and slalom. The BFGs show some damge, mostly due to
excessive understeer and tire chatter. The Toyos sohow some damage and the Hankooks virtually no
damage.
SKID PAD TIRE TRACK IMAGES ON VIDEO
These images show the rubber laid down on the skid pad. The darest marks are from the BFG. Also not
the path of the dark marks, farther away from the circle radius than the others. Also note the chatter
marks on these tracks. The Hankooks had the lightest marks, meaning less tire scrub.
TEST DRIVER EVALUATIONS
Asphalt Skid Pad Test, Big Bear Airport HANKOOK BFG TOYO
Traction Overall 8 4.5 6
Directional Stability 7.5 4 6
Steering Feel 7.5 5 6
Steering Input Responsiveness 7.5 4.5 6
Test importance 10 of 10 Average 7.63 4.5 6
TEST DRIVER COMMENTS:
Hankook: Excellent in all categories; feels like a UHP tire; no chatter;
minimal understeer
BFG: Feels sloppy; excessive tire chatter at tire traction limit; low grip level;
high slip angles at limit; much understeer
Toyo: A good, solid tire overall; some understeer and chatter at cornering
limit; good feel
Asphalt Skid Pad Test, Big Bear Airport HANKOOK BFG TOYO
Traction Overall 8 4.5 6
Directional Stability 7.5 4 6
Steering Feel 7.5 5 6
Steering Input Responsiveness 7.5 4.5 6
Test importance 10 of 10 Average 7.63 4.5 6
TEST DRIVER COMMENTS:
Hankook: Excellent in all categories; feels like a UHP tire; no chatter;
minimal understeer
BFG: Feels sloppy; excessive tire chatter at tire traction limit; low grip level;
high slip angles at limit; much understeer
Toyo: A good, solid tire overall; some understeer and chatter at cornering
limit; good feel
To view the tests on the Skid Pad of an individual tire, click
on the image of that tire below.
on the image of that tire below.
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Copyright 2009 Don Alexander
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