rear suspension question for the setup guys.

[englertracing]

Hello late model guys.
Currently I run a ministock.
I'm building a road/hillclimb special if you don't know what hill climb is, its basically like an asphalt rally up a hill.
I'm using a bunch of late model stuff a cambered winters rear end some billet bird cages. And ohlins lmp shocks.

Now my question is do you think its worth the trouble to use a z link setup for no rear steer of course, a 5th coil, and brake floaters on a road race car?

Is there any disadvantages?

To me it seems like the best type of axle suspension because everything is adjustable seperately but of course all you guys know that.

[dualdj1]

well, with a road course car, you actually do want roll steer too, but you need to make sure you can roll both ways (assuming this isn't a straight line hill climb).

Not sure what I'd suggest though suspension wise. My gut says you don't really want it squatting too much, so maybe a pullbar setup of some sort, which would also help out of the corners. Probably have to run something like the rayburn purple bar with no rake to keep the rear end centered properly.

The easiest for that stuff is always leaf, as it has a natural roll steer, and don't need any extra control arms. But I'd think any suspension could be made to work.

I'm intrigued though, and would be curious to see what you come up with/end up using.

[Matt49]

My belief is that 4-bar with a lift bar would generate the best combination of forward bite and rear-steer. That being said, if the "track" for the hill climb is really rough, a swing-arm setup may produce more consistency and drivability.
Regardless, you'll want to avoid a j-bar/panhard bar type setup like we use in late models and perhaps look into something like a watts link style deal for lateral location and roll center control.

[englertracing]

well, with a road course car, you actually do want roll steer too, but you need to make sure you can roll both ways (assuming this isn't a straight line hill climb).

Not sure what I'd suggest though suspension wise. My gut says you don't really want it squatting too much, so maybe a pullbar setup of some sort, which would also help out of the corners. Probably have to run something like the rayburn purple bar with no rake to keep the rear end centered properly.

The easiest for that stuff is always leaf, as it has a natural roll steer, and don't need any extra control arms. But I'd think any suspension could be made to work.

I'm intrigued though, and would be curious to see what you come up with/end up using.

I didn't think I would want rear steer. In my book race car vehicle dynamics it says rear steer in the direction we use on dirt, on asphalt, it will steer itself tighter roll more, and steer more untill it goes around.

I did read opposite of what we use on dirt may be desirable. I figured if I set it up with both bars of a z level and equal length no rear steer. With several mounting holes I could make it steer either way.

As for.lateral location. Watts link. But I'm also looking at a neat device called a mumford. It is far more flexible with roll center location vs a watts but the complexity of 1 more bell crank/ link.

What's the difference between using a pull bar vs a Lift bar?
I was thinking lift bar with about no squat. I don't know anything about a pull bar.

Matt
Why do you think the swing arm would be advantagous on the rough.

Its a little rough, but nothing like a dirt track can get.

[Matt49]

I didn't think I would want rear steer. In my book race car vehicle dynamics it says rear steer in the direction we use on dirt, on asphalt, it will steer itself tighter roll more, and steer more untill it goes around.

I did read opposite of what we use on dirt may be desirable. I figured if I set it up with both bars of a z level and equal length no rear steer. With several mounting holes I could make it steer either way.

As for.lateral location. Watts link. But I'm also looking at a neat device called a mumford. It is far more flexible with roll center location vs a watts but the complexity of 1 more bell crank/ link.

What's the difference between using a pull bar vs a Lift bar?
I was thinking lift bar with about no squat. I don't know anything about a pull bar.

Matt
Why do you think the swing arm would be advantagous on the rough.

Its a little rough, but nothing like a dirt track can get.

A couple of points. I may have misinterpreted what you were saying but the lift bar isn't what creates the antisquat...that's done by the drag links in a 4-bar setup.
As for the swing arm over a 4-bar when it's rough. 4-bar is excellent for generating mechanical downforce/loading of the rear wheels but if the track is rough, it can become very erratic (load shifting back and forth from tire to tire) and difficult to stay smooth under acceleration. A swing-arm setup seems to roll through rough patches with much more driveability.
Believe it or not, most good dirt tracks are extremely smooth these days which is why 4-bar has become the dominant and preferred rear suspension. But if the track end up rough for some reason, put money on the swing arm guys to have above par finishes.

[JustAddDirt]

rear suspension

Myself I would go with a swingarm.
You can get rollsteer if the bar angle settings are correct. the springs are in the correct neutral location for right and left turns. should be very controllable going both right and left
I think a pullbar would be best, but a liftbar would work well also.
Swingarms to not need all that thrust angle for traction,and are much more predictable, and consistant handling.

On an 4 link oval car we always rotate into the birdcages with left turns, so if you do go with a 4 link, I think you should float both springs on the front of the birdcages.
4 link cars use bar thrust angles for traction, and I believe it would be way too uncontrollable on a right and left turn application with the bar angle needed for high traction the rear steer would be way too much.
How many 4 link cars do you see racing on pavement.....none.
All are 2 link, 3 link applications.

But if you were to mount the birdcages solid to the rearend like a dragcar it may work.

If you use a double panhard bar like on the dodge durango's it should have a neutral effect on handling.

[CrumpRacing]

Swing arm, pullbar and a right side straight (panhard) bar like Rayburns old purple bar.

[englertracing]

http://www.not2fast.com/chassis/mumford.shtml

This is going to be the lateral location device.

Im still thinking r/s would be bad on pavement. Most stock vehicles the outside of the car gets shorter in a turn like my mustang before I got the rear suspension right for dirt.

I wish my track was smooth victorville auto raceway. They fired the guy doing the Awsome prep work john aiden. He runs sprints and a speedway bike track. He could prep our track so nice. After they canned him they butchered the track. It was like a baja course. My mustang just dominated the pintos 8 1st places out of 11 races.

I guess the late models would be generating the anti squat from the 4 bar angle being so steep

But what about the torque arm 5th coil? This acts as a swing arm and generates anti squat as well doesn't it?

[Matt49]

Technically, anti-squat is mechanical in nature and is only affected by the angle of the drag links. The lift bar is using the torque of the rear end to attempt to lift the car which results in counteracting down force to the rear tires. So while it is achieving some of the same things as antisquat, it isn't technically antisquat. The 5th coil is simply absorbing some of the lifting. In a dirt late model, the location of the 5th coil (how far it is from the rear axle) can have a drastic affect on handling. Of course you also need a chain or 6th coil assembly to absorb the force of torque in the other direction under braking. This is only if you have the brake calipers clamped to the axle tube. If the brake calipers are on the birdcage, brake forces are absorbed by the drag links. You'll see dirt late models with various combinations of brake locations depending on what desired. Floated on one side and clamped on the other, clamped on both sides, and floated on both sides.

[englertracing]

Does anyone see any disadvantages to a 4 bar with A 5th coil on asphalt? I watched a video of some dlms on a short track and one of them set the overall track record.