How would you design a late model ?

[gdaagent]

I don't think a lot of forward traction is really needed. You don't need ANY if you don't slow down. A 4 wheel independent suspension car would smoke what we have today and it wouldn't be able to use a lift bar or pull bar.

I don't see independent rear suspension working on a high banked oval.

[Ghopper]

Independent rear suspension is the way to go if the rules allowed.

It would allow more fine tunning of toe/camber of the tires. The South American gentleman mentioned a verison of IRS that I am guessing is lacking the anti-squat we run now in the traditional 4-bars cars and therefore dynamic wedge on corner entry and exit.

Important qualities to look at are tire vertical load/toe/camber, overall vehicle dynamic wedge and torque vectoring (fixed in our case with tire stagger).


Ghopper

[abe_05]

4-bar does have problems that we all adjust around. If you were to design a new chassis, you must start at designing a new rear suspension. What good does rear springs do in most 4-bar setups? On throttle springs are useless. Car is standing up on 4-bars which is loaded by the forward force of the rear end and springs are completely unloaded unless you are on a tight track were car stays rolled over on right rear but left rear is never loaded by spring on throttle. Rear springs for the most part controls corner entry and chassis roll. So changing design were springs play a more important part would be my first idea of attack. What if you could load springs on acceleration? By theory this would be best scenario. This would control car and make it more stable. Cantalever design might be a good idea with current 4-bar.

[dualdj1]

I tend to agree with GHopper. Independent would be a world of difference, as you could make your geometry change on both rear wheels separately based on travel. IE, as car rolls over, wheel base either lengthens, shortens, or stays same, for desired effect.

[Matt49]

Independent rear suspension is the way to go if the rules allowed.

It would allow more fine tunning of toe/camber of the tires. The South American gentleman mentioned a verison of IRS that I am guessing is lacking the anti-squat we run now in the traditional 4-bars cars and therefore dynamic wedge on corner entry and exit.

Important qualities to look at are tire vertical load/toe/camber, overall vehicle dynamic wedge and torque vectoring (fixed in our case with tire stagger).


Ghopper

This brings me to a point that I have often pondered. With as much as we can get the cars to turn these days with rear-steer, should we not be tuning stagger toward optimum camber? I look at rear tire wear and often ponder this.

[supercomet32]

How many of you missed the comments of the indepedent not having the forward bite that the 4 bar has in real world test on cars in australia?....what part of that computes to some how two seperate side working seperately somehow work together to create more speed?....speed is the common denominator and one side deciding to do one thing while the other does something else just splits the possible horsepower distrubution effectively down the middle there has to be a trade off and in my opinion it would require more motor... you would be spending money on both ends....face it the 4 bar works and isnt a crutch. it works plain and simple...bell cranks work but once again adding more moving parts to the equation..JMHO

[MasterSbilt_Racer]

How many of you missed the comments of the indepedent not having the forward bite that the 4 bar has in real world test on cars in australia?....what part of that computes to some how two seperate side working seperately somehow work together to create more speed?....speed is the common denominator and one side deciding to do one thing while the other does something else just splits the possible horsepower distrubution effectively down the middle there has to be a trade off and in my opinion it would require more motor... you would be spending money on both ends....face it the 4 bar works and isnt a crutch. it works plain and simple...bell cranks work but once again adding more moving parts to the equation..JMHO

The independent can be tuned to give you everything the 4 link does and more. I guess a big block mod wouldn't be faster with an independent front suspension?

There hasn't been any work put into it, so sure if you just bolted a wishbone suspension under a late model it would be slower. How many road course cars have wagon-axle rear suspensions? Do they not have to accelerate rapidly out of slow corners?

[dualdj1]

the major difference between independent and solid axle is the lift effect you can get from the twisting of the axle itself (vs the standard way independent is setup). But since independent isn't used on dirt, no one has been able to play around with different ways to mount the center section to get the same lift effect as a solid axle. The center doesn't have to be mounted solid right where the center of our current solid axles are (as it is on say the mustang cobras or vettes, etc); it could be mounted on pivots with a lift arm to have the same effect as our current axles do. There are so many things you can do with independent, that while requiring a lot of learning, tuning and some creative engineering, would decimate solid axles.

[racin6mod]

back in 82 my father owned a 4 cyl. stock car with an independent rear susp. I think it was out of a toyota car but my piont is it was fast as he$$ many night the driver had a half lap lead when the thing broke an axle or the hub flange. the design was for street us so it could not hold up to the side loads of a dirt track.but I think this could be done right if you over design the weak areas around the outer ends of the axles and drive hubs plus it took a lot of rear percent.

[supercomet32]

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

[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.