How would you design a late model ?

[MasterSbilt_Racer]

how many of you missed that it had been tried tested and concluded that a independent suspension on an oval track dirt car DID NOT provide more forward bite that a 4 bar rear suspension. It has been done and does nto work and also those road cars that have an independent suspension have a power to weight ratio much higher than a dlm and is part of the equation.....like i said in my opinion if it were to work you'd need a drastic increase in horsepower to gues in the neighborhood of 1200 HP or higher if you keep the weights in the current configuration. their is effective HP loss to the ground in an independent setup. your turning to systems that increase the scrub off of your numbers makign it ineffective with the current motors in these cars. 850hp wont cut it. and even if you get all of that worked out the tires simple will not hook up on dirt/clay

Where is this extensive test? An independent suspension will cause the drivetrain to have a 300 hp parasitic power loss?

[sj valley dave]

I have to agree with MB Racer on the 300 HP parasitic loss! Either someone is just tossing info around out there and has no idea or is just yanking peoples chains...IMO...LOL

[dualdj1]

how many of you missed that it had been tried tested and concluded that a independent suspension on an oval track dirt car DID NOT provide more forward bite that a 4 bar rear suspension. It has been done and does nto work and also those road cars that have an independent suspension have a power to weight ratio much higher than a dlm and is part of the equation.....like i said in my opinion if it were to work you'd need a drastic increase in horsepower to gues in the neighborhood of 1200 HP or higher if you keep the weights in the current configuration. their is effective HP loss to the ground in an independent setup. your turning to systems that increase the scrub off of your numbers makign it ineffective with the current motors in these cars. 850hp wont cut it. and even if you get all of that worked out the tires simple will not hook up on dirt/clay

Are you that dense that you think one test proves that it doesn't work?? All it might prove is that someone taking a road setup and putting it on the dirt doesnt work. The reason road race cars run such high power to weight ratios is because they have much more traction, it has nothing to do with losses in the suspension setup. There is no way possible that an independent suspension causes more than 15-20hp difference over a live axle, and I doubt it's even that much. You obviously don't know much about independent suspension.

[EAMShater]

well I guess since an independent suspension causes a loss of 300 hp I need to take the motor out of my new can am side by side and put in a 350? Cause if what you say is true then the speedometer is way wrond when it says I'm running 70. It shouldnt even move if the suspension causes all that drag.. right? Just askin..

[supercomet32]

the estimated HP number was just a draw from a hat what i was saying was that yes extensive testing of a Dlm chassis with an independent suspension setup had been done in australia and concluded that as it stands now there isn't enough forward bite in an independent setup like there is from a 4 bar setup. one the reasons being the hp loss not necessarily 300h[ but it was enough to drop considerable time on the stopwatch. my guess on hp was simply picking a larger number than the typical 900 950 or whatever because that much wouldn't do enough.at least to the power to weight ratio to equal the road race cars numbers that was brought up.

while the independent rear would let the tires have a smoother ride around it simply does not equate to faster times on the stop watch.

disagree all you want but their isn't anything on a independent suspension the tis going to launch a car forward nor allow you to corner like a 4 bar. the independent rear doesn't change the wheelbase totally changing your desired line around the track. also as you turn you going to have to lift more. the 4 bar lets you use your momentum to turn the car and get back on the throttle sooner which increases your corner speeds and as a by product dropping your lap times

[TALON75]

I think it could work, we run a BMW 320i in our mini stock class(it was a former track champion car which won 10 of 13 races), 1.9 engine which i believe is the smallest CC engine in the class, the car gets through the corners better than any but the key is to not get it too sideways . With independant rear being able to toe and camber the rears independantly is a big help . Too me if the LM you tested struggled with forward bite then you were overpowering it and it could be better with less HP and being real smooth . what kind of torque absorber was used in this test? was the diff solid mounted? these are some of the first issues I would consider, solid mount your 4 bar car and see how well the forward bite works for it . Who did this testing?

[supercomet32]

your comparing apples to oranges. no ministock has a 4 link in the rear. as for the differential from the article i read it seems the differential was solid mounted similar to the diff in a military hmmwv. the car had a 800hp motor from what i remember and running it side by side with another 4bar with the same motor it lost forward bite it also could not enter the corner as hard like you said it had to either slide it or slow down and stay as straight as possible thus giving it a serious disadvantage in the corner adn then it couldnt get up off the corner due to the drive lose.

other than the rear differences the cars were identical.

in their street stock type cars the independent rear is the norm and simply converting one of those cars to a 4bar drastically changed the lap times. .75+ sec faster or so on a the stop watch.

the 4bar allows you to stear through the corner faster using your momentum and the rest of the suspension gives much more forward drive. you just have to learn what to do with it to make it work.

[TALON75]

I would love to see this article, where was it published, do you have a link?

[MasterSbilt_Racer]

your comparing apples to oranges. no ministock has a 4 link in the rear. as for the differential from the article i read it seems the differential was solid mounted similar to the diff in a military hmmwv. the car had a 800hp motor from what i remember and running it side by side with another 4bar with the same motor it lost forward bite it also could not enter the corner as hard like you said it had to either slide it or slow down and stay as straight as possible thus giving it a serious disadvantage in the corner adn then it couldnt get up off the corner due to the drive lose.

other than the rear differences the cars were identical.

in their street stock type cars the independent rear is the norm and simply converting one of those cars to a 4bar drastically changed the lap times. .75+ sec faster or so on a the stop watch.

the 4bar allows you to stear through the corner faster using your momentum and the rest of the suspension gives much more forward drive. you just have to learn what to do with it to make it work.

A street independent rear is designed to turn equally well left or right. A street independent rear has zero anti-squat geometry. Anti-squat is where the forward bite comes from.

[racin6mod]

the power loss thing is bs flat out! I would bet it really has less power loose over all. I have a vetter rearend in the shop now and the torgue required to turn the unit is with in a couple inch pounds of a 9inch 3rd member.the forward bite is were I think the problems would start showing up.if I remember correctly we had a 62 percent rear in a 4 cylinder car that was easy to get but with a lm it's a problem.

[supercomet32]

you test is a static test when the independent rear is travelling through its motion range it uses different amounts of torque to spin.

for all the engineers here that think itll work please go waste your money doing a test that has already been confirmed.

im done talking either you get it or you dont. you probably also think a nitro'd ricer can beat 400+ hp on the street too right.

there are numerous reasons why the independent works in some cases and doesnt in others...on a dirt oval it does not work better than a 4 bar

[MasterSbilt_Racer]

you test is a static test when the independent rear is travelling through its motion range it uses different amounts of torque to spin.

for all the engineers here that think itll work please go waste your money doing a test that has already been confirmed.

im done talking either you get it or you dont. you probably also think a nitro'd ricer can beat 400+ hp on the street too right.

there are numerous reasons why the independent works in some cases and doesnt in others...on a dirt oval it does not work better than a 4 bar

The 4 link was once confirmed to be slower than the monoleaf. The swingarm was once considered superior to both on slick surfaces. I would say the swing arm/pullbar is probably superior to the 4 link for "going forward", but what difference does that make at a place like Eldora Speedway?

This one off test proves nothing. Were the control arms mounted perpendicular the the frame rails? Parallel to them? Somewhere in between? Were all of these iterations attempted? Various amounts of anti-squat angle? Two wheels tied together cannot grip as well as two that are free to do their own thing. A dirt car needs more than forward bite. We are not drag racing. Food for thought.

You are correct that there is some power loss when the differential is driving a wheel that is at a 20 degree angle to the center of the differential. The amount of loss is going to depend on the u joint. A latemodel cannot use all the power it has, so that doesn't concern me too much.

Besides, when have the Aussies not been 10 years behind in dirt racing technology?

[dualdj1]

im done talking either you get it or you dont.

All you have done is talk. I have not seen one shred of evidence or proof of what you say. You've provided no references, no credible numbers, and brought no credibility to yourself in this debate.

As MBRacer points out, there are so many different variables you can change, that even if you could provide us with the evidence of this test, one test still proves nothing. "Independent Suspension" is a broad generalization, the same as "Solid Axle" suspension (ie 4-bar, swing arm, leaf spring, tortion bar). How you apply it can be very different.

[Ghopper]

Independent rear suspension....If it becomes legal, it will be faster in ~2years or less.

No one will waste time on testing it till it is legal. Other benefits are component lower replacement cost and safety. I dont want to write an essay on this...but involves decoupling and containment.

The solid axle only lives on because it is all we are allowed to run. Any previous dirt IRS test was done without our most recent knowledge. For example: did you know that F1 cars completely unload their left front tire when turning left under thottle? mmm - just like a dirt car (i say unload, not hang it in the air)


Ghopper

[Ronin]

Unfortunately I was not able to access this site for a while and could not comment as posts were updated. I will post some comments below but cannot reference each relevant post....

If you were able to make an independent suspension differential rotate about itself (as a live axle does) it will not produce the same reaction torque on the wheels as a live axle does. An independent suspension differential will have to be mounted on the chassis, so the reaction torque will be absorbed by the chassis, not the wheels as in a live axle. This reaction torque aids traction and is controlled using a torque arm or pull-rod. Joining an independent suspension differential to the wheels will make it a live axle.

One advantage of an independent suspension is that you will be able to independently adjust traction and steering. On a 4-link there is a degree of change to either variable as you change the other variable.

Keep in mind that the j-bar ads a considerable amount of side bite to a dirt oval racecar. Replicating the effect of a j-bar on an independent suspension could create undesirable motion ratios of the outside/inside wheel (depending which side you mount the bar on the chassis).

Independent suspensions always have a degree of camber change as the chassis roles. Remeber that asphalt racecars do not roll as much as dirt race cars, so camber changes can be controlled much easier. The freedom of movement between the chassis and a live axle in a 4-link allows the rear wheels to always be in perfect contact with the ground as there is not camber changes.

It is always good to reduce unsprung mass. However, considering the suspension travel on 4-link suspensions it will be very difficult (dare I say impossible?) to use rocker arms to actuate the shocks. If you draw a rocker arm arrangement you will notice that the angle change makes it very difficult to maintain constant ratios. A system like this will require very large rockers which might become impractical.