Ride Height: How low possible on stock suspension?
05-04-2011, 10:51 AM
#61
Le Mans Master
-Matt
05-04-2011, 11:18 AM
#62
Drifting
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OK. I going to dive in with my settings for a C5. Bottom line I personally feel that as long as you are in the ball park most of the speed differences are mental. Almost all of us are weekend/non_professional racers. We do this for fun and I doubt many (not all) of us could run laps consistent enough to see if we got the .005 second per lap improvement some settings will provide.
Remember, setup should be based on:
The geometry of the cars suspension
Weight and down-force available
The tires you run
The type of track it is
This is why "Feel" is last for me.
The dimensions given by the factory are for a street car. They have to build in a certain amount of understreer required by the DOT. This is why they use a staggered wheel size and the ride heights specified.
The T1 setup is based on the requirements to run in class and the springs and shocks specified.
So, obviously when you are using different wheels sizes, tires, springs, shocks and sways the dimensions will change.
This is where I'm at for a race car, not a dual purpose car.
After testing I have ended up with:
1.5 - 2.5 degrees of camber in the front
1.5 - 2 in the rear depending on the tire I use and the track I'm at
The ride height measurement at the frame rails is equal front and rear with me in the car.
The body on a C5 has appropriate aerodynamic rake built into the body already.
For my car measuring at the lower control arm pivots to the ball joint this means about 20 - 25mm on the front and 55 - 65mm on the rear.
I have a splitter with a full under tray on the front (front breather)
Wheel lip canards
Ventilated hood and a wing on the back with up to 450lbs of down force. I'm set for about 300lbs at 120mph.
I use 18x10.5" wheels front and rear with identically sized tires front and rear.
Remember, setup should be based on:
The geometry of the cars suspension
Weight and down-force available
The tires you run
The type of track it is
Flat or Banked
Mainly left or right turns
Proof and Testing:Lap Times
How it "Feels" to the driver
I'm of the opinion you setup the car to obtain maximum mechanical grip and then it is the drivers job to take advantage of what they have. I see and understand both sides of the argument but MY PERSONAL feelings and the way I work with my car is, I need to learn how to drive the car setup for best mechanical grip.This is why "Feel" is last for me.
The dimensions given by the factory are for a street car. They have to build in a certain amount of understreer required by the DOT. This is why they use a staggered wheel size and the ride heights specified.
The T1 setup is based on the requirements to run in class and the springs and shocks specified.
So, obviously when you are using different wheels sizes, tires, springs, shocks and sways the dimensions will change.
This is where I'm at for a race car, not a dual purpose car.
After testing I have ended up with:
1.5 - 2.5 degrees of camber in the front
1.5 - 2 in the rear depending on the tire I use and the track I'm at
The ride height measurement at the frame rails is equal front and rear with me in the car.
The body on a C5 has appropriate aerodynamic rake built into the body already.
For my car measuring at the lower control arm pivots to the ball joint this means about 20 - 25mm on the front and 55 - 65mm on the rear.
I have a splitter with a full under tray on the front (front breather)
Wheel lip canards
Ventilated hood and a wing on the back with up to 450lbs of down force. I'm set for about 300lbs at 120mph.
I use 18x10.5" wheels front and rear with identically sized tires front and rear.
05-04-2011, 11:34 AM
#63
Racer
I went to CMP this weekend with some scrub A6's with 3 goals, win some new tires with old tires, get qualy points for nats, and play around/test with the car. Specifically, I played around with rear ride height. I started out with the car lower in the rear than I've ever run it, and through the course of the weekend raised it. Despite not adjusting the cross (did not bring my scales) after raising the ride height, the car got faster (and felt better) through the weekend.
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
05-04-2011, 11:40 AM
#64
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I have searched the GM manual and it doesn't specify any difference in ride height for the Z06, only a difference in alignment specs.
05-04-2011, 11:48 AM
#65
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I went to CMP this weekend with some scrub A6's with 3 goals, win some new tires with old tires, get qualy points for nats, and play around/test with the car. Specifically, I played around with rear ride height. I started out with the car lower in the rear than I've ever run it, and through the course of the weekend raised it. Despite not adjusting the cross (did not bring my scales) after raising the ride height, the car got faster (and felt better) through the weekend.
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
05-04-2011, 11:56 AM
#66
Racer
05-04-2011, 12:17 PM
#67
Drifting
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Just a hint, I found if you lengthen the toe link mount at the spindle upright by about an 1" or so you can slow down the toe out under compression and it becomes much more linear under droop. I tried relocating the mount on the cradle but it didn't have very positive affects in any direction or position that was realistic within mounting constraints.
05-04-2011, 12:26 PM
#68
Safety Car
Thread Starter
I went to CMP this weekend with some scrub A6's with 3 goals, win some new tires with old tires, get qualy points for nats, and play around/test with the car. Specifically, I played around with rear ride height. I started out with the car lower in the rear than I've ever run it, and through the course of the weekend raised it. Despite not adjusting the cross (did not bring my scales) after raising the ride height, the car got faster (and felt better) through the weekend.
)
)
Looking at a lot of C5s at a recent NASA event, the fender gaps front/rear on just about all the cars were low and the same front to rear.
05-04-2011, 12:36 PM
#69
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Curious how high you got it? Mine now measures about 5.06" to the frame rail at the rear jacking puck location. This is on the rail itself not in the recessed part where the puck actually goes. Front is 4.75" so there's 0.31" rake. You can see it in the fender gaps (although of course I never measured those).
Looking at a lot of C5s at a recent NASA event, the fender gaps front/rear on just about all the cars were low and the same front to rear.
Looking at a lot of C5s at a recent NASA event, the fender gaps front/rear on just about all the cars were low and the same front to rear.
05-04-2011, 12:41 PM
#70
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Despite not adjusting the cross (did not bring my scales) after raising the ride height, the car got faster (and felt better) through the weekend.
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
There is no doubt in my mind about running the car low, especially in the rear. The front doesn't seem to be as bothered by it. (this is with OEM springs and C5Z OEM shocks with a 3118+ lb race weight)
The advantages of ST2
05-04-2011, 01:49 PM
#71
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comparing measurements at the fender or the frame isn't very accurate unless you have the exact same size wheels, tires and air pressures. Those measurments are only relevent for comparison and setup on your specific combination. That's why I use the numbers from the pivot point to the bottom of the ball joint.
Measuring from the ground to the frame rail is useless unless both cars have the same size wheels/tires/etc.
05-04-2011, 02:22 PM
#72
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Actually the distance from the center of the wheel to the fender is independent of all the variables you mentioned. The only variable you can't account for is a non-stock fender.
Measuring from the ground to the frame rail is useless unless both cars have the same size wheels/tires/etc.
Measuring from the ground to the frame rail is useless unless both cars have the same size wheels/tires/etc.
Once you have setup a car working from the pivot points and ball joints this would be a very easy way to make and verify future changes especially if you don't have a lift.
06-25-2011, 04:51 PM
#73
Safety Car
Just to confirm on this - trim measurements should be from the middle of the forward-most bolt on the front of each lca mount? This doesn't look like an issue on the front as the forward front bolt looks parallel, but rear forward bolts are angled.
Thanks.
Thanks.
06-26-2011, 10:28 AM
#74
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You will notice there is a big difference in the mm value for the front and rear measurement.
Typical T1 setup calls for about 72mm difference front to rear.
This is partly for geometry and partly to keep rake in the chassis.
I have started venturing away from such a huge difference since I found out the body has aero rake built into it and you get better balance front to rear when you don't add rake to the chassis.
The biggest thing is to not go the wrong way on the ride height/geometery and start causing your contact patch to become a moving target.
06-26-2011, 12:22 PM
#75
Drifting
The owner's manual in my C5Z indicated no more than 15mm which is a little over a half inch. On another now defunct forum a long time ago Ken Brown from GM Engineering posted that the early C5 Z51 cars shouldn't be dropped more than a half inch.
One well known T1 racer who is part of this forum told me he doesn't lower his cars at all. He didn't find any advantage to lowering them.
Bill
One well known T1 racer who is part of this forum told me he doesn't lower his cars at all. He didn't find any advantage to lowering them.
Bill
06-26-2011, 12:32 PM
#76
Team Owner
Yes it is the front of the front bolt in both cases. The idea being this is basically (closest) pivot point to being in the same plane as the ball joint.
You will notice there is a big difference in the mm value for the front and rear measurement.
Typical T1 setup calls for about 72mm difference front to rear.
This is partly for geometry and partly to keep rake in the chassis.
I have started venturing away from such a huge difference since I found out the body has aero rake built into it and you get better balance front to rear when you don't add rake to the chassis.
The biggest thing is to not go the wrong way on the ride height/geometery and start causing your contact patch to become a moving target.
You will notice there is a big difference in the mm value for the front and rear measurement.
Typical T1 setup calls for about 72mm difference front to rear.
This is partly for geometry and partly to keep rake in the chassis.
I have started venturing away from such a huge difference since I found out the body has aero rake built into it and you get better balance front to rear when you don't add rake to the chassis.
The biggest thing is to not go the wrong way on the ride height/geometery and start causing your contact patch to become a moving target.
06-26-2011, 03:14 PM
#77
Safety Car
Got the ride height into spec.
Stock rear bolts were not short enough so we added a spacer up top to get to 122mm.
For the front, Hardbar's delrin mounts come with a bolt that is too short to get into spec. About an inch too short. We machined a pad out of of plastic, similar to delrin, with a little cup for the delring ball to sit in which got us in the ballpark of spec. Because of this I ended up with some extra rake, which I'll address later once I can source the correct length bolt.
When lowered, the A arms start to point downwards, which will cause all kinds of geometry havoc, which gets worse as the suspension is loaded. Dropping 1/2" probably still keeps the arms parallel to the ground, but doesn't seem like a good place to start (maybe for Z51/Z06 cars, def not base).
Cornerweighting was by far the easiest and quickest part of the whole ordeal. Do the jounce and roll a few times and then measure. And then again to recheck until the weights are steady.
Stock rear bolts were not short enough so we added a spacer up top to get to 122mm.
For the front, Hardbar's delrin mounts come with a bolt that is too short to get into spec. About an inch too short. We machined a pad out of of plastic, similar to delrin, with a little cup for the delring ball to sit in which got us in the ballpark of spec. Because of this I ended up with some extra rake, which I'll address later once I can source the correct length bolt.
When lowered, the A arms start to point downwards, which will cause all kinds of geometry havoc, which gets worse as the suspension is loaded. Dropping 1/2" probably still keeps the arms parallel to the ground, but doesn't seem like a good place to start (maybe for Z51/Z06 cars, def not base).
Cornerweighting was by far the easiest and quickest part of the whole ordeal. Do the jounce and roll a few times and then measure. And then again to recheck until the weights are steady.
07-24-2011, 04:49 PM
#78
Safety Car
C6 trim height specs are slightly different, especially the C6Z:
My C6 Z51 (sort of, DRM coilovers, etc) is going in tomorrow morning and I'm looking at:
Front: -1.75deg camber, 1/32 total toe-in, 7.5deg caster
Rear: -1.25deg camber, 1/16 total toe-in
Ride height: 4 1/2" to frame just in front of jacking puck hole, rear 4 1/2" to frame just behind rear jacking puck hole. (Hoping this falls in to the right range as measured "properly".)
This is a bit more caster and somewhat less rake than I have on the car right now. I'm also going to space the front upper A-arms out a little bit since I rub the wheelhouse at lock right now.
Can anybody confirm that T1 trim values are 14mm and 86mm? That's a significant drop from even the minimum tolerances for a C6Z (35.6mm, 102.6mm)...
My C6 Z51 (sort of, DRM coilovers, etc) is going in tomorrow morning and I'm looking at:
Front: -1.75deg camber, 1/32 total toe-in, 7.5deg caster
Rear: -1.25deg camber, 1/16 total toe-in
Ride height: 4 1/2" to frame just in front of jacking puck hole, rear 4 1/2" to frame just behind rear jacking puck hole. (Hoping this falls in to the right range as measured "properly".)
This is a bit more caster and somewhat less rake than I have on the car right now. I'm also going to space the front upper A-arms out a little bit since I rub the wheelhouse at lock right now.
Can anybody confirm that T1 trim values are 14mm and 86mm? That's a significant drop from even the minimum tolerances for a C6Z (35.6mm, 102.6mm)...
08-25-2016, 10:24 AM
#79
Le Mans Master
Here's how to measure ride height the correct and most accurate way.
This is also how Phoenix Racing does it when they setup their cars and cars for customers.
The first diagram is the factory settings with tolerances. These are at curb weight.
I currently run with 25mm in the front and 97mm in the rear. I'm running Penske 8760's with coilovers and my car only weighs about 2850#'s with me in it.
You should maintain a rake at 72mm difference front to rear.
T1 setup is about 14mm front and 86mm rear.
Front measurement is from the center of the front pivot bolt of the front lower control arm to the bottom of the lower ball joint. This is the 1 and 2 measurment of the Z dimension.
Rear measurement is also from the center of the front pivot bolt of the rear lower control arm to the bottom of the lower ball joint. This is the 1 and 2 measurment of the D dimension.
These are the factory specs
This is the Front measuring location "Z Trim Height"
This is the rear measuring location "D Trim Height"
This is a picture of the tool I made to make the measurements instead of buying the $250+ GM tool
I put the socket over the nut, then stick the magnet on the bottom of the ball joint. Then I turn the nut on the threaded rod until the 1/2" angled aluminum piece is level then I measure the height along the threaded rod subtract 1/2 the diameter of the socket and the angle + the magnet and I have my number. This is easier on a 4 post lift but I do it on the ramps in my garage.
Here's a link to the GM tool.
http://www.costplustools.com/Kent-Mo...ge_p_9541.html
Hope this helps clear up all the questions that always come up around this subject. The primary reason you don't want to get your ride height too low is because these cars have camber gain built into the suspension and if they are too low the gain will be too fast and actually cause the tire to break loose. There is also the issue of bump steer but that can be corrected.
The T1 settings will work because the springs are so stiff. If you aren't using T1 springs those setting won't work properly!
This is why I run the higher setting but I can get away with lower than the factory min. tolerance because of the wheel rates I run. If you use some of the street/track coilover setups out there and your car weighs close to factory curb weight you will not get away with settings this low.
The only way to properly lower your car beyond these settings and maintain good and predictable handling is to use dropped spindles like the ones LG sells.
Just my 2 cents on the subject.
This is also how Phoenix Racing does it when they setup their cars and cars for customers.
The first diagram is the factory settings with tolerances. These are at curb weight.
I currently run with 25mm in the front and 97mm in the rear. I'm running Penske 8760's with coilovers and my car only weighs about 2850#'s with me in it.
You should maintain a rake at 72mm difference front to rear.
T1 setup is about 14mm front and 86mm rear.
Front measurement is from the center of the front pivot bolt of the front lower control arm to the bottom of the lower ball joint. This is the 1 and 2 measurment of the Z dimension.
Rear measurement is also from the center of the front pivot bolt of the rear lower control arm to the bottom of the lower ball joint. This is the 1 and 2 measurment of the D dimension.
These are the factory specs
This is the Front measuring location "Z Trim Height"
This is the rear measuring location "D Trim Height"
This is a picture of the tool I made to make the measurements instead of buying the $250+ GM tool
I put the socket over the nut, then stick the magnet on the bottom of the ball joint. Then I turn the nut on the threaded rod until the 1/2" angled aluminum piece is level then I measure the height along the threaded rod subtract 1/2 the diameter of the socket and the angle + the magnet and I have my number. This is easier on a 4 post lift but I do it on the ramps in my garage.
Here's a link to the GM tool.
http://www.costplustools.com/Kent-Mo...ge_p_9541.html
Hope this helps clear up all the questions that always come up around this subject. The primary reason you don't want to get your ride height too low is because these cars have camber gain built into the suspension and if they are too low the gain will be too fast and actually cause the tire to break loose. There is also the issue of bump steer but that can be corrected.
The T1 settings will work because the springs are so stiff. If you aren't using T1 springs those setting won't work properly!
This is why I run the higher setting but I can get away with lower than the factory min. tolerance because of the wheel rates I run. If you use some of the street/track coilover setups out there and your car weighs close to factory curb weight you will not get away with settings this low.
The only way to properly lower your car beyond these settings and maintain good and predictable handling is to use dropped spindles like the ones LG sells.
Just my 2 cents on the subject.
Thanks
