Hi would anyone be able to help with a couple of prob's i am now having.
1. I am pushing the car hard then braking into a hair pin and the back starts bouncing as i brake and down change.
2. The back of the car is bouncing on hard cornering, could be to hard in the back spring area maybe?.
3. Am understeering like you would not believe.

Car has bluebird front end, 4degrees caster, a small amount of toe out and 2 degrees of camber. I am running 185 kumho slicks, ute rear end, gas shocks and reversed springs(4)

any help appreciated

Hi Jared, Are the rear springs the standard coupe springs apart from the eyes being reversed? or have you added leaves?
Are the kumo`s convetional or radial slicks? (Radials need to run alot more camber than 2 degs. more like 4.5.)

What tire pressure are you running?

What brand/valveing on rear dampers?

Does the diff have any lateral locating device?

Does the rear end have suficient travell? (you need min 3"droop and 4" bump with a live axel, thats 7" overall)

I`d try adding at least 2 degrees more camber and a little more toe out (about 4mm total) at the front.

The rear could be caused by insuficient droop travel on suspension/dampers, serverly under inflated rear tires (if the condition exists only with steering input) or exesive rebound on rear dampers.

Simon.

do you mean you have 4 flipped leaves?

how much droop travel do you have? measure it with and without the shocks attached.

what shocks? are they an off-the-shelf part for a 1200 coupe, or are they from another car?

my initial impression is that your rear leaf springs are all wrong. not that they're too hard, because that would make it oversteery, but that you don't have enough droop travel available and they're working against the shocks.

Another possibility is that the rear shocks are too stiff in rebound - if they are designed for another car?

understeer can be caused by alot of things. what is your front ride height (from centre of wheel to edge of gaurd?
what front spring rate?
what sway bar?
locked diff?

The rear hopping can happen if you change down to early.

Do all your braking before you downchange. You dont go through all the gears, you can slow a car faster by concentrating on maximum braking and then change into the gear the corner requires.

S.

Standard springs added,springs are inverted.
slicks are radial and tyre pressures are front 38 cold and rear 36 cold.
koni rear shocks and no lateral locating device.

thanks Simon your info is a great help

Ok bear with me on this as the sometime driving instructor in me needs a couple of questions answered:

First, how's your heel & toe down shifts. If you don't have this down or are a little rough you'll get the dreaded axle tramp...especially if your local track has a bit of wash boards on the entrance.

Next the gas shocks: are these adjustable and if so did you crank the rebound damping near full stiff..................the rear of the car may be jacking down on corner entry, so by mid corner it's riding nose high (think overloaded pick up truck) OR the shocks and springs are mismatched, the shock being woefully under damped and springs are just oscillating wildly (this would be the case over any bumpy stretch of track)

Finally the understeer (two part question) you mention a bit of toe out; How much toe and why. Did you dial this in because the car wouldn't turn mid corner? Was it set up this way or the recommended setting by someone? I ask this because it is common in front engine rear drive live axle cars for drivers to dial in more toe out to get the car to rotate mid corner, very often to compensate for abruptly letting of the brake pedal (nose pops up and unloads the car) vs. trail braking deep into the corner. Second part; coming off the hairpin are you oh so gently feeding in the throttle as in small bore cars like ours it's so easy to unload the front end by gassing it to early and to quickly.

Now what to do about it: first check all the mechanicals. are any bushes worn? are the springs momentarily binding?make sure both rear dampers are set up equally and not leaked oil or there charge? Are any bolts loose etc?

If all the mechanicals check out fine then it's back to you. Ask yourself at the exact moment the wheel hop what did you do. A quick way to find out if it's driver induced is to approach the corner as normal and just brake, no down shift, don't step on the clutch either............if it still does it try it with the clutch in, if clutch in solves then simply down shift and ease off the clutch just as you're easing of the brakes (had a students Mustang that need to be oh so gently coaxed this way).

As to the understeer ask the same question: when is the exact moment the understeer starts and exactly what input did you feed the car.

If the car is pogoing through long sweepers as well, check the rear dampers first.............the fronts being stiff in comparison to the rears will definitely cause understeer.

One other note be careful with the camber, to much negative will make it weavy as all get during threshold breaking.

Sorry to be so long winded but there are number of things that could cause this.

Tom

I'd suggest those tyre pressures are far too high for Kuhmo semi slicks and the car's weight. You're probably 8-10psi too high if you are doing multiple laps, or around 4-6psi too much if you are doing hillclimbs.

It's all a bit of a black art is'nt it!My wife wonders why i don't always sleep at night

Rallytwit has made a valid point.Does driver ability or lack of it make a reasonable handling car misbehave ?
A friend of mine used to race Under 2 litre Touring cars (yes he and I are that old) and has been back doing lap dashes the last couple of years in a Typhoon.His times were good around Winton but after an advanced driver course with John Bowe his lap times improved 4 seconds.The money spent on this day would have been the cheapest performance gain you could possibly get and he didn't even touch the car with a spanner.
Look I am not doubting setting up any vehicle is a black art especially when we get ideas from a number of different sources but if we are driving the cars properly our times should be quicker and more consistent and we should get a better feel for what the car is doing and then try vary our setup to suit.
Cheers
Bob

Have to agree with L18-b110.

Drop your tyre pressures a heap.

You will find HOT pressures on those tires most likely would be between 28 and 34 psi, depending on what the temps across the tread and tire look like.

S.