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#1 WINTON SPRINTS HANDLING QUESTIONS
bobthebuilder Posted on: 2008/9/9 9:41
Hi Guys
Just did another sprint meeting on the weekend and ended up with identical times to last time (1.48.12). Front end was great with extra castor and camber. We softened up the rear by removing overload springs and felt like it was three wheeling on higher load corners (with the rear wheel up )which is a very unnerving feeling.Traction out of corners was better like this. Any ideas as to what our problem might be ?
We also put a 2 1/4 inch free flow exhaust on and dropped 400 revs at the end of the straight.Does this sound like the exhaust is to big without enough back pressure
Thanks
Bob


#2 Re: WINTON SPRINTS HANDLING QUESTIONS
bert Posted on: 2008/9/9 9:47
A bit confused Bob,you picking up the unloaded front or rear wheel?


#3 Re: WINTON SPRINTS HANDLING QUESTIONS
bobthebuilder Posted on: 2008/9/9 9:59
Rear wheel was unloading big time.It could have been on the bumpstop . It has got me puzzled


#4 Re: WINTON SPRINTS HANDLING QUESTIONS
Daveman Posted on: 2008/9/9 10:24
Are you running a rear swaybar? what sort of tyres?

If you are picking up the inside rear wheel you could well be on the bump stops


#5 Re: WINTON SPRINTS HANDLING QUESTIONS
bert Posted on: 2008/9/9 10:24
So assuming i understand you,the inside rear was spinning madly mid corner and not giving any drive,but just hanging.

Just reading it again,what do you mean by "unloading"is this the wheel you are leaning on or the un weighted wheel,as you have mentioned bump stops.


#6 Re: WINTON SPRINTS HANDLING QUESTIONS
aidaniel Posted on: 2008/9/9 10:38
you might need to harden up your front end as when your front end drops under brakes and you turn the whole car pivots across the diagonally opposite wheels. back pressure with your exaust only saves your valves and deminishes power so you get more power out the manifold as apposed to a full system but your system might be a bit big. what size motor is in it? softening up the rear by removing the overload springs only softens it up after a certain amount of travel as they are only designed to work after they are carrying a load.


#7 Re: WINTON SPRINTS HANDLING QUESTIONS
sikyne Posted on: 2008/9/9 12:08
Yes, firstly check you have at least 3" of rear bump travell and 3" of droop. But usually the rear would oversteer if the bump stops are hit not lift the inside. Increase the front sway bar a fair bit. dont be in a hurry to put heavier front springs in, try the bar first.



#8 Re: WINTON SPRINTS HANDLING QUESTIONS
bobthebuilder Posted on: 2008/9/9 12:44
Thanks for the advice guys.
The inside rear wheel is unloading. It doesn't spin madly as we have a LSD in it.
There is mention of a rear sway which is something we have thought about. The front end is not the problem it feels great.
If the rear is on the bump stops do we just remove them ?


#9 Re: WINTON SPRINTS HANDLING QUESTIONS
sikyne Posted on: 2008/9/9 23:38
Have you got any photos of the front of the car whilst cornering, it would be good to see how much roll the car is getting.

You say the front is good, but presuming the body isnt twisting too much if the inside rear is getting too light eg. LHR, that means the RHF is falling over too far.Thus the heavier front bar, dont desmiss this unlees your car is understeering(pushing) like a pig.

Another thing that can cause this is insufficient rear end lateral locationing.

As you corner the diff moves sideways under the body puting more load on the outside rear tire and less on the inside. the more grip your tires have the worse it becomes.
Solution: Panhard bar, watts linc or "A" arm.

But if your using stardard road tires this shouldnt be a big problem. without these devices i would use a urethane front spring eye bush.

I would look at these two areas first.

Simon

Edit: all suspension should have bump rubbers wether it be on the body the diff, spring seat or in the shock itself most race cars use the latter. The suspension should not contact these at any time durring normal driving/racing. They are there to prevent sudden shock loadings of metal to metal contact in the event of running into unforseen objects or holes. In your case the curbs around the track! or running off!


#10 Re: WINTON SPRINTS HANDLING QUESTIONS
bert Posted on: 2008/9/9 23:51
Bob,there are several questions to be answered before a solution can be arrived at,and every action causes a reaction in chassis handling.On the assumption theres no one in Albury that can advise you without ripping you off and selling you stuff you may not need,i am sending you a PM with my number to do with what you like.

A satisfactory end result will,using this forum take months of tooing and frowing



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