Question regarding swaybars
Thread Starter
Burning Brakes
Joined: Mar 2002
Posts: 839
Likes: 0
From: Lewiston, Maine
Question regarding swaybars
In choosing swaybar sizes, I have run into an unknown area for me. I am hoping that with the connections this forum provides that someone may answer my questions.
Known facts:
I don't want the rear spring to: A) "do a good enough job" and B) act as a swaybar AND a spring. I'd rather the spring perform its duties and the swaybar perform its duties; with a little help from the spring.
Vette Brakes and Products offers three front bar sizes, and three rear bar sizes.
Front= 1.000" 1.125" 1.250" (or 1" 1 1/8" and 1 2/8")
Rear= 0.625" 0.750" 0.875" (or 5/8" 6/8" and 7/8")
All of the suspension combination packages that VB&P puts together utilize 1.125" front and 0.750" rear bars. I'm guessing that this is a "hot" setup.
My questions are these: Would I maintain the same aspect ratio if I chose 1.000" front and 0.625" rear bars, or 1.250" front and 0.875" rear bars? What if I selected the biggest rear, and the smallest front? In the latter scenario, I'd still induce understeer (barely) and the bars would be closer to equal. How would my handling behave with a 1" front bar and 7/8" rear bar?
A big THANKS goes to those who aid me with this.
Known facts:
- A front bar larger than the rear bar will inherently induce understeer.
- A rear bar larger than the front bar will inherently induce oversteer.
- A stock 1969 Corvette has 49% of its mass on the front wheels and 51% of its mass on the rear wheels.
- My car is different than stock however, the bubble window is going bye-bye soon, the fiberglass monospring reduced weight in my car's rear, and I've got aluminum heads and an aluminum radiator in mind.
- I have 275/40-17s planned for the front and 315/35-17s planned for the rear (ZR-1 sized).
- Some small block cars did not come with a rear bar from the factory [including mine]
- I have purchased and installed a dual-mount rear spring which, because of its unique mounting points, may also "act" as a rear sway bar.
- Racers with the dual-mount spring don't install a rear swaybar because it does a good enough job, and they are concerned with saving weight.
I don't want the rear spring to: A) "do a good enough job" and B) act as a swaybar AND a spring. I'd rather the spring perform its duties and the swaybar perform its duties; with a little help from the spring.
Vette Brakes and Products offers three front bar sizes, and three rear bar sizes.
Front= 1.000" 1.125" 1.250" (or 1" 1 1/8" and 1 2/8")
Rear= 0.625" 0.750" 0.875" (or 5/8" 6/8" and 7/8")
All of the suspension combination packages that VB&P puts together utilize 1.125" front and 0.750" rear bars. I'm guessing that this is a "hot" setup.
My questions are these: Would I maintain the same aspect ratio if I chose 1.000" front and 0.625" rear bars, or 1.250" front and 0.875" rear bars? What if I selected the biggest rear, and the smallest front? In the latter scenario, I'd still induce understeer (barely) and the bars would be closer to equal. How would my handling behave with a 1" front bar and 7/8" rear bar?
A big THANKS goes to those who aid me with this.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Roll resistance is not linerar. See the Addco web site for a chart that shows the relative resistance of various bar sizes.
With the larger tires, you can use a larger rear bar without rear end breaking loose.
With larger rear bars, you lose the benefit of the independent rear suspension - it acts more like a straight axle.
This may be a situation where there is not single right answer. Settings on your dual mount rear spring, bar size, camber settings, tire size and pressure can all be varied tosuit your driving style or track conditions.
With the larger tires, you can use a larger rear bar without rear end breaking loose.
With larger rear bars, you lose the benefit of the independent rear suspension - it acts more like a straight axle.
This may be a situation where there is not single right answer. Settings on your dual mount rear spring, bar size, camber settings, tire size and pressure can all be varied tosuit your driving style or track conditions.
Thread Starter
Burning Brakes
Joined: Mar 2002
Posts: 839
Likes: 0
From: Lewiston, Maine
Originally Posted by Me2
If you don't want the rear spring acting like a swaybar, why are you running the dual mount?
There is nothing wrong with running a rear sway bar along with the dual-mount spring however. It's only because of the unique mounting of the dual-mount that it may act as a sway bar.
I don't want my rear spring performing two duties. I would like a sway bar to take up that duty so that the rear spring can perform its own duties.
Thread Starter
Burning Brakes
Joined: Mar 2002
Posts: 839
Likes: 0
From: Lewiston, Maine
I'm not turning anything off and this is part of my compound question. To "turn off" the dual-mount would be to dismount its brackets from the crossmember. The spring wouldn't work very well after that.
What I would like to know is: What sway bar sizes should I run, keeping in mind that the rear spring will naturally have some tendency to transfer weight side-to-side. Will a "gi-normous" rear bar do a better job of making sure that it is the primary candidate in transferring weight?
When all is said and done, I want a rear sway bar that will work: A) with a matched front sway bar, and B) will take much of the weight transfer duties away from the spring. Yes, the spring will inherently transfer weight. I am presuming that a rear sway bar will do a majority of that work.
The ending of the third paragraph in my initial post says it best, "I'd rather the spring perform its duties and the swaybar perform its duties; with a little help from the spring."
What I would like to know is: What sway bar sizes should I run, keeping in mind that the rear spring will naturally have some tendency to transfer weight side-to-side. Will a "gi-normous" rear bar do a better job of making sure that it is the primary candidate in transferring weight?
When all is said and done, I want a rear sway bar that will work: A) with a matched front sway bar, and B) will take much of the weight transfer duties away from the spring. Yes, the spring will inherently transfer weight. I am presuming that a rear sway bar will do a majority of that work.
The ending of the third paragraph in my initial post says it best, "I'd rather the spring perform its duties and the swaybar perform its duties; with a little help from the spring."
Team Owner
Joined: Apr 2006
Posts: 29,335
Likes: 51
From: Monterey, CA
I'm no expert, but I would think that the spring is going to do its thing regardless, and a big bar would just make it too stiff. Also, there is no "magic setup", as it all depends on your overall setup, driving style, track, etc.
Personally, I would try it without a bar and see how it does, then adjust from there.
Personally, I would try it without a bar and see how it does, then adjust from there.
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Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Originally Posted by Me2
I'm no expert, but I would think that the spring is going to do its thing regardless, and a big bar would just make it too stiff. Also, there is no "magic setup", as it all depends on your overall setup, driving style, track, etc.
Personally, I would try it without a bar and see how it does, then adjust from there.
Personally, I would try it without a bar and see how it does, then adjust from there.
Abby Normal
Joined: Dec 2001
Posts: 53,452
Likes: 92
From: Press "2" for English
Originally Posted by 1969Vette383
I don't want the rear spring to: A) "do a good enough job" and B) act as a swaybar AND a spring. I'd rather the spring perform its duties and the swaybar perform its duties; :
a sway-bar is and always has been a cheap band-aid approach to the ultimate goal, that is a progressive, rising rate spring. one that increases spring rate at a non-linear rate as opposed to the much easier and cheaper method of a linear rate production style spring. the big problem with rising rate springs is they are very specific to the application. they are typically custom wound (i.e. coil) based on vehicle static weight, ride height, total travel and a bunch of other variables.
you would be far better off getting, or fabricating, a 'universal' style that clamps onto the bar so that you can change the length of the lever arm to tune it. this would be far easier to produce and tune, and it would give you alot more flexability in the size bar you select as a starting point.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Ditto Clutchdust on the adjustable lever arms.
Also call Dick Guldstrand at Gulstrand Engineering in LA (310-391-7108). He probably knows more about Corvette suspensions than anyone not inside GM.
Also call Dick Guldstrand at Gulstrand Engineering in LA (310-391-7108). He probably knows more about Corvette suspensions than anyone not inside GM.
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Suspension "system"...
RE Guldstrand...and it is important to consider shocks,springs,sway bars as a "system"...you must also be prepared to "experiment" some as well by "testing" the vette...in some cases,a rear sway bar is not needed...depends on a combination of factors...
This is a very good read on the topic:
http://wiki.corvettefaq.com/index.php?title=Suspension
Click on Corvette Handling...it is a big file....worth printing for references..
Rich
Last edited by rihwoods; Sep 18, 2006 at 12:39 PM.
Drifting
Joined: Dec 1999
Posts: 1,462
Likes: 1
From: Reno nevada
VB&P allowed me years ago to mix and match on the kit.
My 71 has 460# with 1 1/8th spring end adjustables with poly mounts.
My rear has 360# mono and 5/8th spring end adjust. IMO - the 1/2, 9/16th and 5/8th have such a low % of off side compression that they don't really do all that much. Just marginal change.
I do know that you can't make a blanket statement about sway bars. If car "A" has wide sticky tires like you want, body roll will be increased because of additional traction induced "G" loading. Car "B" with junk 15 inch tires and wheels could be over sway barred with the same diameter making it tail happy.
My 71 has 460# with 1 1/8th spring end adjustables with poly mounts.
My rear has 360# mono and 5/8th spring end adjust. IMO - the 1/2, 9/16th and 5/8th have such a low % of off side compression that they don't really do all that much. Just marginal change.
I do know that you can't make a blanket statement about sway bars. If car "A" has wide sticky tires like you want, body roll will be increased because of additional traction induced "G" loading. Car "B" with junk 15 inch tires and wheels could be over sway barred with the same diameter making it tail happy.