C4 Squat issues
07-28-2012, 08:38 PM
#1
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
C4 Squat issues
Hey guys I've been reading on here for awhile now but finally decided to make an account. I've got a 1970 Chevy C10 truck that we put a front and rear 93' C4 suspension under with a full tube chassis and a LS2 and T-56 6 speed. The problem is the rear will squat so bad under hard acceleration and shifting it will actually drag the chassis. It still has the stock leaf springs and the total weight right now is 3,035lbs. We had it at the Columbus Goodguys show a couple weekends back and ran it on the autocross track, did decent but the weight transfer to the rear was killing me when it would squat. Does anyone know if there is a heavy duty leaf I could put in there or what to try? any help would be appreciated!
07-28-2012, 09:45 PM
#3
Burning Brakes
I would look at replacing the transverse leaf spring with coilovers. You are going to want to set your static ride height so that the half shafts are higher at the center section than at the outboard bearing, while stationary. What you want to be looking for is a nearly level half shaft at full acceleration. You will probably have to play with the spring rates to get it just right.
On my C4 racer, we relocated the rear shock mounts to achieve this very thing. Before the relocation (correct ride height), under full acceleration, the half shafts were higher outboard and it just screwed the handling all up. Good Luck with your project..............
On my C4 racer, we relocated the rear shock mounts to achieve this very thing. Before the relocation (correct ride height), under full acceleration, the half shafts were higher outboard and it just screwed the handling all up. Good Luck with your project..............
07-28-2012, 10:10 PM
#5
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
07-29-2012, 04:01 PM
#6
Tech Contributor
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Posts: 18,343
Received 767 Likes
on
549 Posts
Question: You complained about dragging the frame under acceleration. What's your anti-squat geometry in the rear?
07-29-2012, 09:15 PM
#8
Max G’s
Just find a solid rear axle for the pick up. Or you can get a higher rate transverse spring, largest anti-roll bar possible and adjust your ride height with the spring bolts.
07-29-2012, 09:46 PM
#9
Melting Slicks
Remember weight is going to transfer based on the CG height and wheelbase, and that will help pin the rear tires on acceleration. It's not the weight transfer that's the issue, it's the amount of that weight that is being held up by the springs and how much needs to go thru the linkage. What is probably happening with the present setup is that the rear end is hitting the bump stops because the vehicle is squatting so much.
It has less to do with spring rates, although if he has the base springs it's really going to be bad, he doesn't need coilovers, just get a set of higher rate springs (like Z51's or Z07) to start. Then he needs to get the anti squat right relative to his CG height.
07-29-2012, 10:04 PM
#10
Safety Car
That's the right question. My guess is no.
Remember weight is going to transfer based on the CG height and wheelbase, and that will help pin the rear tires on acceleration. It's not the weight transfer that's the issue, it's the amount of that weight that is being held up by the springs and how much needs to go thru the linkage. What is probably happening with the present setup is that the rear end is hitting the bump stops because the vehicle is squatting so much.
It has less to do with spring rates, although if he has the base springs it's really going to be bad, he doesn't need coilovers, just get a set of higher rate springs (like Z51's or Z07) to start. Then he needs to get the anti squat right relative to his CG height.
Remember weight is going to transfer based on the CG height and wheelbase, and that will help pin the rear tires on acceleration. It's not the weight transfer that's the issue, it's the amount of that weight that is being held up by the springs and how much needs to go thru the linkage. What is probably happening with the present setup is that the rear end is hitting the bump stops because the vehicle is squatting so much.
It has less to do with spring rates, although if he has the base springs it's really going to be bad, he doesn't need coilovers, just get a set of higher rate springs (like Z51's or Z07) to start. Then he needs to get the anti squat right relative to his CG height.
07-29-2012, 10:30 PM
#11
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
What's your attraction to coilovers for the rear? They're just a spring and shock (like the originals), but more expensive. You can get several different rates on the production spring (as you can with coilovers) and you can adjust the corner weight the same with either spring. What does the expensive solution buy you in your application that the stock design spring/shock setup won't?
Question: You complained about dragging the frame under acceleration. What's your anti-squat geometry in the rear?
Question: You complained about dragging the frame under acceleration. What's your anti-squat geometry in the rear?
That's the right question. My guess is no.
Remember weight is going to transfer based on the CG height and wheelbase, and that will help pin the rear tires on acceleration. It's not the weight transfer that's the issue, it's the amount of that weight that is being held up by the springs and how much needs to go thru the linkage. What is probably happening with the present setup is that the rear end is hitting the bump stops because the vehicle is squatting so much.
It has less to do with spring rates, although if he has the base springs it's really going to be bad, he doesn't need coilovers, just get a set of higher rate springs (like Z51's or Z07) to start. Then he needs to get the anti squat right relative to his CG height.
Remember weight is going to transfer based on the CG height and wheelbase, and that will help pin the rear tires on acceleration. It's not the weight transfer that's the issue, it's the amount of that weight that is being held up by the springs and how much needs to go thru the linkage. What is probably happening with the present setup is that the rear end is hitting the bump stops because the vehicle is squatting so much.
It has less to do with spring rates, although if he has the base springs it's really going to be bad, he doesn't need coilovers, just get a set of higher rate springs (like Z51's or Z07) to start. Then he needs to get the anti squat right relative to his CG height.
07-29-2012, 10:32 PM
#12
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
http://67-72chevytrucks.com/vboard/s...=512270&page=3
This is a page that has some good pictures of how we have it set right now.
This is a page that has some good pictures of how we have it set right now.
07-29-2012, 10:36 PM
#13
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
I just wasn't sure what it was going to take to get it under control but I knew there were guys putting coilovers in to help it. but if I could keep the transverse spring I would love to. I just wasn't sure who to talk to, where to get springs and parts of that nature so I thought someone on here would be able to point me in the right direction.
07-30-2012, 12:32 PM
#14
Melting Slicks
It looks like you have a ton of adjustment available for the rear trailing links, so you can get any amount of anti-squat that you want.
There was a thread on C4 anti-squat here on the road racing and autocross page, here it is....
http://forums.corvetteforum.com/auto...y-so-much.html
This will explain how to calculate how much and should be a good guide. As I said, you can first increase the spring rate a bit. The C4 rear suspension is limted by jacking effect, you can get yourself into a whole bag of trouble if you put in too big a spring and too big a sway bar at the same time. Here is a link to the chart that has the spring rates for each year and model.
http://www.corvetteactioncenter.com/...usp_chart.html
You don't want to go to the 26mm rear bar with a heavy rear spring, but other than that you can up the spring rate from what you most likey have, and it is probably the right thing to do.
Then you need to reset your trailing links to account for the higher center of gravity of your rig relative to the corvette.
Since you have a huge number of holes in the mounting brackets you need to raise up the angle of the links, so that the extened point where the cross is closer to the CG. Don't just go mucking with the links, figure out what will give you what you want before you change it and life will be a lot better.
There was a thread on C4 anti-squat here on the road racing and autocross page, here it is....
http://forums.corvetteforum.com/auto...y-so-much.html
This will explain how to calculate how much and should be a good guide. As I said, you can first increase the spring rate a bit. The C4 rear suspension is limted by jacking effect, you can get yourself into a whole bag of trouble if you put in too big a spring and too big a sway bar at the same time. Here is a link to the chart that has the spring rates for each year and model.
http://www.corvetteactioncenter.com/...usp_chart.html
You don't want to go to the 26mm rear bar with a heavy rear spring, but other than that you can up the spring rate from what you most likey have, and it is probably the right thing to do.
Then you need to reset your trailing links to account for the higher center of gravity of your rig relative to the corvette.
Since you have a huge number of holes in the mounting brackets you need to raise up the angle of the links, so that the extened point where the cross is closer to the CG. Don't just go mucking with the links, figure out what will give you what you want before you change it and life will be a lot better.
The following users liked this post:
C4ProjectCar (03-22-2021)
07-30-2012, 09:49 PM
#15
8th Gear
Thread Starter
Member Since: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
It looks like you have a ton of adjustment available for the rear trailing links, so you can get any amount of anti-squat that you want.
There was a thread on C4 anti-squat here on the road racing and autocross page, here it is....
http://forums.corvetteforum.com/auto...y-so-much.html
This will explain how to calculate how much and should be a good guide. As I said, you can first increase the spring rate a bit. The C4 rear suspension is limted by jacking effect, you can get yourself into a whole bag of trouble if you put in too big a spring and too big a sway bar at the same time. Here is a link to the chart that has the spring rates for each year and model.
http://www.corvetteactioncenter.com/...usp_chart.html
You don't want to go to the 26mm rear bar with a heavy rear spring, but other than that you can up the spring rate from what you most likey have, and it is probably the right thing to do.
Then you need to reset your trailing links to account for the higher center of gravity of your rig relative to the corvette.
Since you have a huge number of holes in the mounting brackets you need to raise up the angle of the links, so that the extened point where the cross is closer to the CG. Don't just go mucking with the links, figure out what will give you what you want before you change it and life will be a lot better.
There was a thread on C4 anti-squat here on the road racing and autocross page, here it is....
http://forums.corvetteforum.com/auto...y-so-much.html
This will explain how to calculate how much and should be a good guide. As I said, you can first increase the spring rate a bit. The C4 rear suspension is limted by jacking effect, you can get yourself into a whole bag of trouble if you put in too big a spring and too big a sway bar at the same time. Here is a link to the chart that has the spring rates for each year and model.
http://www.corvetteactioncenter.com/...usp_chart.html
You don't want to go to the 26mm rear bar with a heavy rear spring, but other than that you can up the spring rate from what you most likey have, and it is probably the right thing to do.
Then you need to reset your trailing links to account for the higher center of gravity of your rig relative to the corvette.
Since you have a huge number of holes in the mounting brackets you need to raise up the angle of the links, so that the extened point where the cross is closer to the CG. Don't just go mucking with the links, figure out what will give you what you want before you change it and life will be a lot better.
Thanks again everyone!
