cherokee95

iTrader: (5)

Just downloaded the Android version after reading this thread.....Worth every penny. Can't wait for the update with setup storage. Keep up the good work.

Martin Crisp

To make this thread more informative than just promoting my App, I thought I would from time to time talk about different setup principles.

Ok, so most drivers know that swaybars take away lateral grip the stiffer you make them. Do you know why? Those with my app...no cheating

Left Front Tire

iTrader: (37)

Martin,
A question about sway bars: when using a sway bar could I run a stiffer overall suspension setup but still have the benefits of using a softer setup?

caltek1

iTrader: (38)

Hello Martin,

What about hints and tips for setting up FWD cars. I find that they can be the hardest to get right and not all want to share the results.

Some ideas would be for understeer and oversteer. The rear end suddenly letting go mid way through the corner,etc

Regards,

Calvin.

Martin Crisp

I am not sure I fully understand your question. Are you asking about a scenario when you run stiffer swaybars and light springs?

caltek1

iTrader: (38)

Is it something to do with the less chassis roll and you diminish grip sooner.

I am still trying to get my head around all of this stuff and apply it to my car. I find that others can just walk up sya change this and presto it works. Me I have to muddle around looking for the differences to make teh car work.

I am finding a FWD car harder to get working than the normal TC.

Perhaps I just need to find a sweet spot and drive the car more smoothly.

I have the book, that I take to the track for guidance on setup, which lives in my pitbag.

Thanks for taking the time to write the book and make the App. I am sure a heap of us appreciate it.

Later,

Calvin.

Martin Crisp

First let me say, I have never worked on a front wheel drive setup before, so what I suggest, has no basis in actual front wheel drive experience. With the FWD cars, the fast majority of the cars weight is at the front of the car, which should translate into the car pushing while entering the corner because the front of the car wants to keep going straight due to the extra weight at the front of the car. I would imaging however that as the car starts to scrub speed to a point where the grip on the front tires is enough to overcome the lateral forces due to weight, and the vertical weight over the front tires could actually start to give the front tires more grip than the rear, then this could cause the snap oversteer. I would guess you don't experience this in a high speed constant speed sweeper, but more in the tighter corners that require you to decrease speed.

Assuming I am on the right track here in terms of the cause, and this typically happens at the apex of tight corners likely in an off power situation, we need to figure out a way to decrease the steering at that point of the corner.

If you increase your ackerman (i.e. the outside tire does not turn as much at full lock) this would help cause the car to push mid corner, which would likely help reduce the snap oversteer.

Next I would make sure I have a low roll center on the front of the car, as this can help with initial turn-in but induce push mid corner, which again could help reduce the snap oversteer.

Next I would think about the spring rates. If the realized spring rate at the front is much stiffer than the rear when you compare pushing the back and front of the car down into the driving surface. This could also be contributing to the snap oversteer as well as contributing to the push on entry. I would strive to find a balanced suspension that feels the same front and rear.

Last I would make sure you have a health amount of droop in the front and rear of the car...likely 3mm above ride height in the rear and 2.5mm above ride height in the front. This will smooth out the car in the corner and help prevent snap oversteer as well.

Again...I have not worked on FWD cars, so I could be out to lunch here. Give these ideas a shot and let me know how they worked.

Cheers.

Martin Crisp

Hey Calvin....keep at it...I still muddle around and get lost sometimes

Good attempt at answering the question..."why do stiffer swaybars take away lateral grip"....but sorry dude

I remember struggling with understanding why this was the case, as it would seem that keeping the car more flat would allow you to use the grip of both the inside and outside tires more, which would mean that stiffer swaybars should actually give you more lateral grip. ...but they don't.

here is a hint...there is something called a 'Tire Performance Curve' which basically states that as you add vertical load on a tire, it does get more grip, but for every x grams of extra vertical load you add, you get a reducing amount of additional lateral grip. In other words you get diminishing returns. Thus when you start to take vertical load away from a tire it looses grip more quickly than when adding the same amount of vertical load.

For example:
If you were to add 50grams more vertical weight to a tire, you might get X more additional lateral grip. However if you take away 50grams of vertical load you will loose Y lateral grip and Y is greater than X.

caltek1

iTrader: (38)

Thanks Martin.

I will give those ideas a try. I found from my initial setup on my FWD that by using a harder tyre up front and softer tyre on the rear the car worked very well.

When I changed to having to run the smae tyres front and rear, my setup did not work and the car would as you say transition from a slight push to a very snap of ther rear end which would make cornering a nightmare.

I did try somethings which sort of helped, but still not right.

I will go and put the above into practice and let you know how it goes.

Thank you.

Calvin.

Sydewynder

Swaybars increase the load on the outside wheel and decreases the load on the inside wheel.
Tire Performance Curve states increase in load (weight) is not linear to increase in traction. Higher the load the less traction is increased. (efficiency loss) Going backwards, more reduction in load will give you more loss in traction.
Putting the above two together when you corner, the increase in outside wheel traction is less than the decrease in traction on the inside wheel so the overall lateral traction is less. The bigger the swaybar the more load so the greater the difference in traction gain versus traction loss resulting in a bigger reduction of overall lateral grip.

Martin Crisp

You got it!!! In other words the greater the difference in load between the inside and outside tire, the less lateral grip you will get.

So then the next questions is....why would we run swaybars, if they reduce lateral grip?

1airborne

iTrader: (12)

To try to even out the load between the inside and outside tires.

1airborne

rickthejetman

iTrader: (4)

I hate my windows phone more and more every day. You can't buy any good @#%^$@ apps for it.

Martin Crisp

Actually, although that is a common answer,...not really...as the the swaybar takes away load on the inside tire and adds load to the outside tire.

Martin Crisp

sorry to hear that.... I actually really like the windows phone 7. I think the user experience is great....it' just too bad there are not as many apps for it. I have been thinking about making my app available on the windows phone, but I fear it will be a lot of work for only a few people. As it is event he android sells so little that it was really not worth the time to create it.