F355 high speed handling

Alan, love the hre's with the yellow calipers. Nice car.

 

Alan, first things first - did you get the alignment checked? Are the tires worn? As someone who tracks his 355 regularly, I can attest to the solid handling of this car at all speeds up to, say, 140+, where the need for a wing becomes readily apparent, a la 355 Challenge.

I'd take the car to get the alignment done first. And make sure your tires have good tread across the surface (if your rear alignment has some negative camber built in, it'll wear the inside of your rear tires heavily, so be sure to check the entire tread).

vty,

--Dennis

 

Check your tire pressures too.

 

PS beautiful rims.

 

The handling of an F355 is about 3 times more sensitive to alignment than an M3. In addition, there are two strategic issues with respect to the F355 chassis versus alignment that you should be aware.

1) There is an instability in the front end as you transition from gas to brakes if the front end is too low and especially if you try to apply any steering input under brakes. The cure is to set the front end to factory ride height.

2) After you get the front end at the right ride height, you can use the rear ride height to control the oversteer/understeer relationship. The factory ride height will result in a slight understeer but is decidely closer to neutral than to understeer. Lowering the rear increases understeer while raising the rear induces oversteer.

Before you get the car aligned, A) put new tires on it, B) set the air pressures to 39-40 PSI* (equal within 0.25 PSI), C) 1/2 tank of gas, and D) your body weight in the drivers seat.

I strongly suggest you check the cornerweighting when you get the car aligned.

SPECS:
Front:
Camber: -0.5 to -0.75
Caster: +7
Toe: 2mm IN
Ride Height: 163 mm

Rear
Camber: -2.0
Toe: 2mm IN
Ride Height: 187mm

Ride height is measured from the level ground surface to the center of the rear pivot bolt at the chassis on the rearward end of the lower control arm.

When I got my F355 it was not sorted well. I learned this stuff sorting it. I tried aligning it, having it aligned at a 'typical shop', and finally took it to a race prep shop who did it right. It is now possible to take my hands off the steering wheel at 150+ and watch the car zoo down the road with less than 1 foot of side-to-side wander (hands off at 150).

With the factory settings 1-2 PSI change in tire pressures can be used to fine tune oversteer/understeer. If you need more than 2 PSI, you should raise or lower the rear ride height by 2 turns of the collar and then see what tire pressures rebalance the car. I can run 34/34 F/R on Bridgestone S03s on the road and on the track (33/33 at MSR).

Finally, be aware that the ubiquitous 265/35ZR18 is NOT a correct rear tire size for the F355**. You really want the 265/40ZR18 but since there are not many of these, you may find youself tempted with the 265/35--don't do it, use the 275/40ZR18 instead.

*These are the hot pressures a tire will run at the track, and are the pressures you should get the alignment done at.

** 996 Porsches use the 265/35 tires thus makeing every high performance tire manufacture create a 265/35--too bad the disrupt the rear ride height of the F355 chassis.