FB Rear Suspension Geometry Problems/Options/Solutions
#53
Lives on the Forum
If I were to sell it, it would have to go locally. The mounts are already set up on my spare 3rd member, which would have to go with the trilink. Just not willing to try to ship something of that size/weight.
But really, I have not decided that I will sell it. I still might install it simply out of curiosity, or if I reach the point that I need to shave off one more tenth of a second and just can't get it any other way. lol.
Sorry if what I said gave the wrong impression. I wasn't actually being all that serious.
But really, I have not decided that I will sell it. I still might install it simply out of curiosity, or if I reach the point that I need to shave off one more tenth of a second and just can't get it any other way. lol.
Sorry if what I said gave the wrong impression. I wasn't actually being all that serious.
#54
Blood, Sweat and Rotors
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And, I have a 3rd link that goes thru the floor (straight link) and it really made the car more predictable. And higher cornering speeds.
#55
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So how adverse are these effects on cars that aren't lowered? How much more balanced and less prone to snap-oversteer is a car at stock height with stock springs? I suppose there's less preload and axle twist, but at the same time there's more body roll.
#56
Lives on the Forum
With the R-comps, you can push the car harder and it ends up leaning further. That little extra movement might be just enough to hit a binding point.
I run lighter springs and heavier swaybars. Gives a better ride on the streets, higher overall traction (too high a spring rate = skipping across pond effect), swaybars and ride height cancel out body roll. Seems pretty stable set up that way. No surprises, unless you work really hard to create them.
(sorry, I was answering an older post apparently. weird.)
I run lighter springs and heavier swaybars. Gives a better ride on the streets, higher overall traction (too high a spring rate = skipping across pond effect), swaybars and ride height cancel out body roll. Seems pretty stable set up that way. No surprises, unless you work really hard to create them.
(sorry, I was answering an older post apparently. weird.)
#57
Rotary Freak
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DriveFast7 - like the 3 link setup. That is what I had in my C Prepared Mustang and it worked really well. It is also what I will be putting in my RX7 as a part of the STU build
What class do you run in? Do you have a cover to goes over the link.....as I recall in Solo I was required to cover all suspension that entered the interior with a metal cover/bulk head
What class do you run in? Do you have a cover to goes over the link.....as I recall in Solo I was required to cover all suspension that entered the interior with a metal cover/bulk head
#58
Rotary Freak
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I pulled the fuel cell out of my car to work on the rear suspension. Here are some pictures of the current panhard bar I have in my car. You can see the Tri Link mount in some of the shots.
I did the fab work on the rear axle housing and made the rod. The rod ends are 3 piece 1/2" stainless. The mount on the chassis has been there for around 10-12 yrs. It looks like crap but has never cracked or failed.
I'll be replacing the chassis mount along with the rear axle housing as a part of my STU build up. The new setup will use a big bearing axle, longer panhard bar, relocated lower control arms and a third link that goes into the car.
I did the fab work on the rear axle housing and made the rod. The rod ends are 3 piece 1/2" stainless. The mount on the chassis has been there for around 10-12 yrs. It looks like crap but has never cracked or failed.
I'll be replacing the chassis mount along with the rear axle housing as a part of my STU build up. The new setup will use a big bearing axle, longer panhard bar, relocated lower control arms and a third link that goes into the car.
#59
Rotary Freak
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Here are some shots of the 4 Traction Bar setup on my friends E Production car. This setup has proven superior to the G-Force Tri-Link system as it allows the driver to apply power earlier in corner exit. The car also has a panhard bar that is extremely long. This car was built by KC Raceware......the KC Raceware rear aluminum hat/rotor setup can be seen.
This is the view from the left rear wheel well.
The upper traction bar attaches to the stock upper control arm mount on the axle housing. The other end of the upper traction bar attaches to a mount that is mostly contained in the car.
The lower traction bar uses the OE mount on the chassis and mounts to the rear axle a couple of inches lower than the stock lower control arm. Moving the lower traction bar mounting point on axle corrects suspension geometry issues caused by lowering the car
This is upper traction bar mount in the car
The mount is welded to the floor just in front of the wheel well. It allows for three mounting positions and is braced to the cage.
Here are a few more shots of parts on the E Production car. The transmission is a Jerico Y2K 4sp transmission. It came from a Nextel Cup team and was originally used for road race qualifying. It has gun drilled shafts and narrowed/lightened gears. It has proven to be bullet proof behind a rotary. Ratios are extremely tight.....1.81:1, 1.50:1. 1.25:1, 1:1. The Clutch is a 5.5" 2 disk Tiltion on a Mazdaspeed aluminum flywheel. The engine is a 85 13B street port built by Roger Mandeville
This is the view from the left rear wheel well.
The upper traction bar attaches to the stock upper control arm mount on the axle housing. The other end of the upper traction bar attaches to a mount that is mostly contained in the car.
The lower traction bar uses the OE mount on the chassis and mounts to the rear axle a couple of inches lower than the stock lower control arm. Moving the lower traction bar mounting point on axle corrects suspension geometry issues caused by lowering the car
This is upper traction bar mount in the car
The mount is welded to the floor just in front of the wheel well. It allows for three mounting positions and is braced to the cage.
Here are a few more shots of parts on the E Production car. The transmission is a Jerico Y2K 4sp transmission. It came from a Nextel Cup team and was originally used for road race qualifying. It has gun drilled shafts and narrowed/lightened gears. It has proven to be bullet proof behind a rotary. Ratios are extremely tight.....1.81:1, 1.50:1. 1.25:1, 1:1. The Clutch is a 5.5" 2 disk Tiltion on a Mazdaspeed aluminum flywheel. The engine is a 85 13B street port built by Roger Mandeville
#61
Blood, Sweat and Rotors
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DriveFast7 - like the 3 link setup. That is what I had in my C Prepared Mustang and it worked really well. It is also what I will be putting in my RX7 as a part of the STU build
What class do you run in? Do you have a cover to goes over the link.....as I recall in Solo I was required to cover all suspension that entered the interior with a metal cover/bulk head
What class do you run in? Do you have a cover to goes over the link.....as I recall in Solo I was required to cover all suspension that entered the interior with a metal cover/bulk head
I don't have a cover but really should make one out of 1/8" aluminum.
Nice work on the EP car.
#63
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So is it not possible to just make adjustible upper links, that can be easily shortened or lengthened based on ride height, the way tie-rods are? Sure they'll still have different rotation radius to lower links, but at least they would allow you to untwist the axle a bit, making the suspension behave as it would at stock ride height.
#64
Rotary Freak
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So is it not possible to just make adjustible upper links, that can be easily shortened or lengthened based on ride height, the way tie-rods are? Sure they'll still have different rotation radius to lower links, but at least they would allow you to untwist the axle a bit, making the suspension behave as it would at stock ride height.
A Tri link does allow you to make pinion adjustments as well as helping with bind because the upper arms are no longer used. But it isn't a complete solution on a lowered car because the lower control arms will be still be out of geometry.
I raced my RX7 with the rear suspension setup like this for years and with 100-135HP it was not an issue. However if you add power - like what you have with a good race engine - this will become an problem. Basically it will cost you time on corner exit.
#66
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Can't the bind simply be addressed with softer bushings? It's obviously not an optimal solution for hard racing, but for lowered daily drivers and occasional track cars it might be enough.
Even with tri-link and panhard, you still have lower links, right? And they still need to twist.
Even with tri-link and panhard, you still have lower links, right? And they still need to twist.
#67
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Can't the bind simply be addressed with softer bushings? It's obviously not an optimal solution for hard racing, but for lowered daily drivers and occasional track cars it might be enough.
Even with tri-link and panhard, you still have lower links, right? And they still need to twist.
Even with tri-link and panhard, you still have lower links, right? And they still need to twist.
The suspensions that I have pictured in this thread- my panhard bar and the 4 link setup - have spherical bearings at each location. If you remove the springs from either car you can manipulate the rear axle through an incredible range of motion with no friction and no binding. Roll rate is controlled by the springs only in both of these suspensions.
#68
The Shadetree Project
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I already added a link in this thread on how to modify your bushings to give more roll compliance.
PB&J racing mod.
http://www.pbandjracing.com/rear_suspension.html
PB&J racing mod.
http://www.pbandjracing.com/rear_suspension.html
#69
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Yes, softer bushings are better because they allow compliance without adding an artifical spring rate. There is an excellent write up on this on the mazdatrix web site in the racing section. The owner of Mazdatrix very successfully campaigned an FB in PRO7 using new control arms with factory bushings.
The suspensions that I have pictured in this thread- my panhard bar and the 4 link setup - have spherical bearings at each location. If you remove the springs from either car you can manipulate the rear axle through an incredible range of motion with no friction and no binding. Roll rate is controlled by the springs only in both of these suspensions.
The suspensions that I have pictured in this thread- my panhard bar and the 4 link setup - have spherical bearings at each location. If you remove the springs from either car you can manipulate the rear axle through an incredible range of motion with no friction and no binding. Roll rate is controlled by the springs only in both of these suspensions.
I already added a link in this thread on how to modify your bushings to give more roll compliance.
PB&J racing mod.
http://www.pbandjracing.com/rear_suspension.html
PB&J racing mod.
http://www.pbandjracing.com/rear_suspension.html
#70
Rotary Freak
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Yeah, spherical bearings work too, but they're probably a lot noisier than bushings, which may or may not matter. I was also thinking that instead of adjustable upper link, there could be a link with a vertically offset pivot and, it could possibly have a bend in it too, so that as it travels up and down, it's not a constant radius in relation to the lower link. That could possibly do away with adjustment. In fact I can think of a few ways to make a plug-and-play self-adjusting upper link, that would likely be guided by the lower, or vice-versa, but it would probably be kind of expensive.
Using the G Force Tri-Link as an example, the Tri Link arm is "J" shaped to clear the floor. However the axis that the link operates on is a straight line that intersects the axis of the mount on the rear axle and the mount on the body. If the rules allowed....the Tri Link would be a straight control arm that passes through the floor of the car.....like what you see on DriveFast7's car.
I would not recomend spherical bearings for a street car - at least not with out having at least one end of the suspension element fitted with a poly or rubber bushing. They are not only noisy but they also rattle themselves loose constantly. Also they have no protection against moisture and dirt and would be short lived. I use the racing suspensions I am familar with as examples of what you "can" do if you have a racecar.
I think there are examples of the successful use of the stock suspension on this thread. So it can be done. These are compromise solutions but so is driving a lowered car on the street. I think that if you follow the advice of those that are doing what you are trying to do, as well as adopting their driving style, you will be successful.
My opinions with respect to suspension run more towards the complete optimization for full on competition. The starter of this post is working with a car in a class that has few restrictions. In that situation it makes sense to take full advantage of you can do with a car.
#74
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Unless you change the pivot points you are accomplishing nothing. The shape of the control arm is not relative. Some how you would have to have a variable pivot point that corrects for geometry issues. I have seen stuff like this on circle track cars...but they only turn one way and can be setup for a specific track.
the mazda 6 uses 2 upper control arms, and 2 ball joints, so when you turn the steering wheel, the upper axis of the kingpin changes, so it changes scrub dynamically
i dunno if there is SPACE or its legal to do something like that, but i guess it would be possible to make some sort of dual/virtual pivot thing...