[ZR1] New ZR1 Corvette Wheel Hop Solution
01-02-2008, 06:17 PM
#1
Drifting
Thread Starter
New ZR1 Corvette Wheel Hop Solution
Did anybody read about the new ZR1 and how the left half shaft is slightly larger than the right side to prevent wheel hop. They made mention that this was done to offset the isollations from each side in that this would help control wheel hop....I guess so the wheels on each side don't hop in sync??? and prevent wheel hop???
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
01-02-2008, 07:57 PM
#2
Race Director
Did anybody read about the new ZR1 and how the left half shaft is slightly larger than the right side to prevent wheel hop. They made mention that this was done to offset the isollations from each side in that this would help control wheel hop....I guess so the wheels on each side don't hop in sync??? and prevent wheel hop???
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
Is the shaft bigger in diameter or slightly longer. Don't know why the diameter would make a difference. Can you post a link to the article.
01-02-2008, 10:27 PM
#5
Drifting
Thread Starter
And to minimize rear-wheel hop, the left-side halfshaft is larger in diameter than the right. Thus if an oscillation starts, it does so at different frequencies. Why the left side? Because it offsets the right rear-mounted battery.
about mid-way down in this article....was curious if anybody else ever heard of this?
http://www.roadandtrack.com/article....&page_number=3
01-02-2008, 11:43 PM
#6
Threadkiller
Member Since: Jan 2002
Location: Long Island, NY
Posts: 15,306
Likes: 0
Received 0 Likes
on
0 Posts
Cruise-In 9-10 Veteran
St. Jude Donor '05-'06-'07-'08-'09
I believe I read in another thread that they are something like 33mm and 40mm.
Here you go:
Here you go:
Traction Limited
Even with the gigantic meats bolted to the backside, the ZR1 will be what is euphemistically called "traction limited." In other words, all that power just goes up into expensive smoke when you try to lay the power down.
And since launching a car with so much horsepower can become a violent, axle-hopping mess, Chevrolet has come up with two novel countermeasures.
First are the rear shocks. When you're stopped and the clutch pedal is depressed and you pile on some revs, the car assumes you want to launch it hard. It automatically softens the compression damping of the rear shocks, and this allows the rear end to squat and effectively shift more weight to the rear of the car for added traction. At the same time, the rebound damping of the rear shocks goes up to 99 percent of full stiffness. This means that the rear cannot spring back up under power in the up-and-down monkey motion of axle hop.
All this is perhaps the cleverest use of adjustable shocks that we've ever heard of. Also, according to Juechter, the standard magnetic shocks allow the ZR1 chassis team to use softer springs than the Z06 for a more compliant ride. To further mitigate power hop, Chevy has also fitted the ZR1 with axle half-shafts of different diameters (33mm on the right and 40mm on the left).
We'll see how all of this works next year when we finally get to drive the thing. We might just try a hard launch or, you know, several.
Even with the gigantic meats bolted to the backside, the ZR1 will be what is euphemistically called "traction limited." In other words, all that power just goes up into expensive smoke when you try to lay the power down.
And since launching a car with so much horsepower can become a violent, axle-hopping mess, Chevrolet has come up with two novel countermeasures.
First are the rear shocks. When you're stopped and the clutch pedal is depressed and you pile on some revs, the car assumes you want to launch it hard. It automatically softens the compression damping of the rear shocks, and this allows the rear end to squat and effectively shift more weight to the rear of the car for added traction. At the same time, the rebound damping of the rear shocks goes up to 99 percent of full stiffness. This means that the rear cannot spring back up under power in the up-and-down monkey motion of axle hop.
All this is perhaps the cleverest use of adjustable shocks that we've ever heard of. Also, according to Juechter, the standard magnetic shocks allow the ZR1 chassis team to use softer springs than the Z06 for a more compliant ride. To further mitigate power hop, Chevy has also fitted the ZR1 with axle half-shafts of different diameters (33mm on the right and 40mm on the left).
We'll see how all of this works next year when we finally get to drive the thing. We might just try a hard launch or, you know, several.
Last edited by vizkiz; 01-02-2008 at 11:48 PM.
01-03-2008, 01:03 AM
#7
Drifting
Member Since: Aug 2006
Location: Irving TX
Posts: 1,773
Likes: 0
Received 0 Likes
on
0 Posts
Anyone with engineering experience care to set the record straight?
01-03-2008, 07:24 AM
#8
Race Director
Although GM doesn't mention this in the article, I am betting the mag shocks with the lower rate springs allow for more wheel-hop control than the axle shafts. I am inclined to beleive that 2KZ28CAM in correct in the shafts are designed more for power changes left to right as the diff works to control tire spin. The mag shocks should give GM a great advantage in reducing/eliminating wheel hop on launch.
01-03-2008, 11:38 AM
#9
Premium Supporting Vendor
From MT
http://www.motortrend.com/roadtests/...e_details.html
6. Asymmetric shaft diameters (33mm left /40mm right) keep half-shafts from establishing a resonance in wind-up, thereby reducing propensity for axle hop.
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
7. MR shocks allow spring rates to be softened slightly
8. Anti-roll bars stiffened
http://www.motortrend.com/roadtests/...e_details.html
6. Asymmetric shaft diameters (33mm left /40mm right) keep half-shafts from establishing a resonance in wind-up, thereby reducing propensity for axle hop.
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
7. MR shocks allow spring rates to be softened slightly
8. Anti-roll bars stiffened
01-03-2008, 01:48 PM
#10
Safety Car
Did anybody read about the new ZR1 and how the left half shaft is slightly larger than the right side to prevent wheel hop. They made mention that this was done to offset the isollations from each side in that this would help control wheel hop....I guess so the wheels on each side don't hop in sync??? and prevent wheel hop???
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
Maybe I should have tried a 3" & 2.5" half shaft combo for my wheel hop problem that I had before using a Dragvette kit. I can only imagine the look on others faces (mechanics) when the would see a 2.5" & 3" half shaft installed at the same time
Last edited by ZL-1; 01-03-2008 at 01:51 PM.
01-05-2008, 02:52 AM
#11
Pro
Member Since: Aug 2004
Location: Ann Arbor MI
Posts: 534
Likes: 0
Received 0 Likes
on
0 Posts
In a system as complex as a rear axle and suspension, there's a lot of modelling and analysis involved, but here's the simple explanation:
Wheel hop is similar to any other noise or vibration problem in a car . . . some mass (the rear wheels and other unsprung mass) is excited at a frequecy very close to it's natural frequency by some outside force (stick/slip of the tires and engine torque/windup in this case).
The natural frequency of a system is directly proportional to its mass and spring rate (the total vertical and rotational stiffness, including contributions of the springs, shocks, bars, and rubber bushings), so to resolve the issue, you either change the mass, change the stiffnesses, or you change the input force. Changing the stiffnesses often has other severe consequences either for cost or performance, and changing the input force is often difficult , so in this case, as in many, they added mass to the system to lower the wheel hop frequency of the one side.
Wheel hop is similar to any other noise or vibration problem in a car . . . some mass (the rear wheels and other unsprung mass) is excited at a frequecy very close to it's natural frequency by some outside force (stick/slip of the tires and engine torque/windup in this case).
The natural frequency of a system is directly proportional to its mass and spring rate (the total vertical and rotational stiffness, including contributions of the springs, shocks, bars, and rubber bushings), so to resolve the issue, you either change the mass, change the stiffnesses, or you change the input force. Changing the stiffnesses often has other severe consequences either for cost or performance, and changing the input force is often difficult , so in this case, as in many, they added mass to the system to lower the wheel hop frequency of the one side.
01-05-2008, 02:32 PM
#12
Burning Brakes
Member Since: Jun 2005
Location: MD
Posts: 1,114
Likes: 0
Received 0 Likes
on
0 Posts
The different twist rates should help, but there is one additional factor that GM hasn't mentioned: The vast majority of all of the half-shaft failures in the C6Z occurred on the right side.
There are several reasons why this happens, but it is no coincidence that GM saw this and put the 40mm shaft on the right side and the 33mm on the left.
There are several reasons why this happens, but it is no coincidence that GM saw this and put the 40mm shaft on the right side and the 33mm on the left.
01-05-2008, 02:58 PM
#13
Burning Brakes
Member Since: Feb 2005
Posts: 1,014
Likes: 0
Received 0 Likes
on
0 Posts
From MT
http://www.motortrend.com/roadtests/...e_details.html
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
http://www.motortrend.com/roadtests/...e_details.html
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
I'm not a dragracer, so could you educate me on this? I thought for maximum traction the key is zero rebound (extension) stiffness on the Front shocks and 100-percent jounce (compression) stiffness on the Rear shocks. Is that correct? That would be contradictory to the ZR1 introduction description. Perhaps GM is trying to address wheel hop at the expense of traction?
01-05-2008, 03:31 PM
#14
Instructor
Member Since: Nov 2007
Location: Rockville, Maryland
Posts: 180
Likes: 0
Received 0 Likes
on
0 Posts
Van Steel,
I'm not a dragracer, so could you educate me on this? I thought for maximum traction the key is zero rebound (extension) stiffness on the Front shocks and 100-percent jounce (compression) stiffness on the Rear shocks. Is that correct? That would be contradictory to the ZR1 introduction description. Perhaps GM is trying to address wheel hop at the expense of traction?
I'm not a dragracer, so could you educate me on this? I thought for maximum traction the key is zero rebound (extension) stiffness on the Front shocks and 100-percent jounce (compression) stiffness on the Rear shocks. Is that correct? That would be contradictory to the ZR1 introduction description. Perhaps GM is trying to address wheel hop at the expense of traction?
01-05-2008, 03:32 PM
#15
Burning Brakes
Van Steel,
I'm not a dragracer, so could you educate me on this? I thought for maximum traction the key is zero rebound (extension) stiffness on the Front shocks and 100-percent jounce (compression) stiffness on the Rear shocks. Is that correct? That would be contradictory to the ZR1 introduction description. Perhaps GM is trying to address wheel hop at the expense of traction?
I'm not a dragracer, so could you educate me on this? I thought for maximum traction the key is zero rebound (extension) stiffness on the Front shocks and 100-percent jounce (compression) stiffness on the Rear shocks. Is that correct? That would be contradictory to the ZR1 introduction description. Perhaps GM is trying to address wheel hop at the expense of traction?
01-05-2008, 04:20 PM
#16
Pro
Member Since: Aug 2004
Location: Ann Arbor MI
Posts: 534
Likes: 0
Received 0 Likes
on
0 Posts
A drag launch is a very complex phenomenon . . . it’s not as simple as maximizing the weight transfer of the tires, especially when wheel-hop is involved.
Besides the front to rear weight transfer of the sprung mass, the torque of the engine is trying to rotate the axle like a propeller in the back of your car. This plants ONE tire, but also tries to lift the other tire off the ground. This phenomenon is a major contributor to wheel hop. I work at another OEM on RWD V8 cars and trucks. We’ve been able to eliminate wheel hop on some cars by using solid mounts for some of the drivetrain mounts to eliminate any wind-up that might be allowed by soft rubber bushings. NVH is significantly degraded which is why OEM’s don’t use them in production.
Back to rearward weight transfer . . . Generally, you want as much as you can get in a drag car. However, after the initial hit, once the rear suspension is fully compressed, the energy stored in the rear springs is released and the weight transfers back to the front, which UNLOADS the rear tires beyond what they are just sitting at curb.
The job of rebound damping in a rear shock (in the case of a drag launch) is to slow down this second phase of weight transfer which happens just milliseconds after the initial launch.
For compression, strictly from a weight transfer standpoint, you don’t want it either full stiff OR full soft. There needs to be SOME compliance in the rear suspension, otherwise the tire becomes the main spring in the system and bounces off the ground. There’s too possible scenarios here . . . too much compression or too little.
If you have too much, you are effectively locking the suspension, which then causes the tires to bounce as I explain above.
Too little can have two possible outcomes . . . If the weight transfer causes too much suspension travel, you’ll end up storing most of the energy in the rear springs instead of using it to plant the tires. Stored energy then gets released, which transfers the weight back to the front.
If the shocks are so soft that the suspension bottoms out, the rear spring rate goes to infinity the instant metal to metal contact is made, which, again, instantaneously unloads the rear tires.
So, in the case of the ZR1, I would guess that quite a bit of development work went into this aspect of the suspension. The specs that GM settled on as mentioned above are probably NOT optimal strictly from a weight transfer point of view, but are most likely the best compromise that allow good weight transfer while effectively managing the drive-train wind-up and wheel hop frequency.
Besides the front to rear weight transfer of the sprung mass, the torque of the engine is trying to rotate the axle like a propeller in the back of your car. This plants ONE tire, but also tries to lift the other tire off the ground. This phenomenon is a major contributor to wheel hop. I work at another OEM on RWD V8 cars and trucks. We’ve been able to eliminate wheel hop on some cars by using solid mounts for some of the drivetrain mounts to eliminate any wind-up that might be allowed by soft rubber bushings. NVH is significantly degraded which is why OEM’s don’t use them in production.
Back to rearward weight transfer . . . Generally, you want as much as you can get in a drag car. However, after the initial hit, once the rear suspension is fully compressed, the energy stored in the rear springs is released and the weight transfers back to the front, which UNLOADS the rear tires beyond what they are just sitting at curb.
The job of rebound damping in a rear shock (in the case of a drag launch) is to slow down this second phase of weight transfer which happens just milliseconds after the initial launch.
For compression, strictly from a weight transfer standpoint, you don’t want it either full stiff OR full soft. There needs to be SOME compliance in the rear suspension, otherwise the tire becomes the main spring in the system and bounces off the ground. There’s too possible scenarios here . . . too much compression or too little.
If you have too much, you are effectively locking the suspension, which then causes the tires to bounce as I explain above.
Too little can have two possible outcomes . . . If the weight transfer causes too much suspension travel, you’ll end up storing most of the energy in the rear springs instead of using it to plant the tires. Stored energy then gets released, which transfers the weight back to the front.
If the shocks are so soft that the suspension bottoms out, the rear spring rate goes to infinity the instant metal to metal contact is made, which, again, instantaneously unloads the rear tires.
So, in the case of the ZR1, I would guess that quite a bit of development work went into this aspect of the suspension. The specs that GM settled on as mentioned above are probably NOT optimal strictly from a weight transfer point of view, but are most likely the best compromise that allow good weight transfer while effectively managing the drive-train wind-up and wheel hop frequency.
01-05-2008, 04:47 PM
#17
Burning Brakes
Member Since: Mar 2007
Location: Scottsdale Arizona
Posts: 824
Likes: 0
Received 0 Likes
on
0 Posts
I remember reading that if I get coilovers then that will takeaway all my wheelhop, I know its a little off topic to the zr1, but figured you guys would be able to tell me if thats true.....
01-05-2008, 05:28 PM
#18
Burning Brakes
Member Since: Feb 2005
Posts: 1,014
Likes: 0
Received 0 Likes
on
0 Posts
A drag launch is a very complex phenomenon . . . it’s not as simple as maximizing the weight transfer of the tires, especially when wheel-hop is involved.
Besides the front to rear weight transfer of the sprung mass, the torque of the engine is trying to rotate the axle like a propeller in the back of your car. This plants ONE tire, but also tries to lift the other tire off the ground. This phenomenon is a major contributor to wheel hop. I work at another OEM on RWD V8 cars and trucks. We’ve been able to eliminate wheel hop on some cars by using solid mounts for some of the drivetrain mounts to eliminate any wind-up that might be allowed by soft rubber bushings. NVH is significantly degraded which is why OEM’s don’t use them in production.
Back to rearward weight transfer . . . Generally, you want as much as you can get in a drag car. However, after the initial hit, once the rear suspension is fully compressed, the energy stored in the rear springs is released and the weight transfers back to the front, which UNLOADS the rear tires beyond what they are just sitting at curb.
The job of rebound damping in a rear shock (in the case of a drag launch) is to slow down this second phase of weight transfer which happens just milliseconds after the initial launch.
For compression, strictly from a weight transfer standpoint, you don’t want it either full stiff OR full soft. There needs to be SOME compliance in the rear suspension, otherwise the tire becomes the main spring in the system and bounces off the ground. There’s too possible scenarios here . . . too much compression or too little.
If you have too much, you are effectively locking the suspension, which then causes the tires to bounce as I explain above.
Too little can have two possible outcomes . . . If the weight transfer causes too much suspension travel, you’ll end up storing most of the energy in the rear springs instead of using it to plant the tires. Stored energy then gets released, which transfers the weight back to the front.
If the shocks are so soft that the suspension bottoms out, the rear spring rate goes to infinity the instant metal to metal contact is made, which, again, instantaneously unloads the rear tires.
So, in the case of the ZR1, I would guess that quite a bit of development work went into this aspect of the suspension. The specs that GM settled on as mentioned above are probably NOT optimal strictly from a weight transfer point of view, but are most likely the best compromise that allow good weight transfer while effectively managing the drive-train wind-up and wheel hop frequency.
Besides the front to rear weight transfer of the sprung mass, the torque of the engine is trying to rotate the axle like a propeller in the back of your car. This plants ONE tire, but also tries to lift the other tire off the ground. This phenomenon is a major contributor to wheel hop. I work at another OEM on RWD V8 cars and trucks. We’ve been able to eliminate wheel hop on some cars by using solid mounts for some of the drivetrain mounts to eliminate any wind-up that might be allowed by soft rubber bushings. NVH is significantly degraded which is why OEM’s don’t use them in production.
Back to rearward weight transfer . . . Generally, you want as much as you can get in a drag car. However, after the initial hit, once the rear suspension is fully compressed, the energy stored in the rear springs is released and the weight transfers back to the front, which UNLOADS the rear tires beyond what they are just sitting at curb.
The job of rebound damping in a rear shock (in the case of a drag launch) is to slow down this second phase of weight transfer which happens just milliseconds after the initial launch.
For compression, strictly from a weight transfer standpoint, you don’t want it either full stiff OR full soft. There needs to be SOME compliance in the rear suspension, otherwise the tire becomes the main spring in the system and bounces off the ground. There’s too possible scenarios here . . . too much compression or too little.
If you have too much, you are effectively locking the suspension, which then causes the tires to bounce as I explain above.
Too little can have two possible outcomes . . . If the weight transfer causes too much suspension travel, you’ll end up storing most of the energy in the rear springs instead of using it to plant the tires. Stored energy then gets released, which transfers the weight back to the front.
If the shocks are so soft that the suspension bottoms out, the rear spring rate goes to infinity the instant metal to metal contact is made, which, again, instantaneously unloads the rear tires.
So, in the case of the ZR1, I would guess that quite a bit of development work went into this aspect of the suspension. The specs that GM settled on as mentioned above are probably NOT optimal strictly from a weight transfer point of view, but are most likely the best compromise that allow good weight transfer while effectively managing the drive-train wind-up and wheel hop frequency.
01-05-2008, 05:37 PM
#20
Melting Slicks
Member Since: Jan 2006
Posts: 2,713
Likes: 0
Received 0 Likes
on
0 Posts
Nice posts, Jahan! The key thing that the average poster might keep in mind is that the ZL1 axle is a spring -- it just happens to be in one linear piece, and the 'spring' action is rotational. Anyone of us who were fortunate enough to have a 70's era Mopar got a lesson on the unexpected with our front suspensions.
http://en.wikipedia.org/wiki/Torsion_beam_suspension
Having the axle rods (springs, but not suspension springs) to each rear wheel a different diameters can change the frequency of oscillation, and if they are therefore not synchronized, that could lessen the overall wheel hop effect greatly.
Older Jag using torsion rods for suspension springing:
http://en.wikipedia.org/wiki/Torsion_beam_suspension
Having the axle rods (springs, but not suspension springs) to each rear wheel a different diameters can change the frequency of oscillation, and if they are therefore not synchronized, that could lessen the overall wheel hop effect greatly.
Older Jag using torsion rods for suspension springing:
Last edited by TrackNoob; 01-05-2008 at 05:44 PM.