How to reduce negative front downforce?

[davekmoore]

Calder cropped compressed.jpg

The pic is at Calder last Sunday. Probs only doing 150k at that point. As well as the undesirable lift in the pic it was also understeering in the corners. The front coilovers can be wound down a touch, but not too much further as it's a daily driver. Any other simple suggestions?

[beavis]

Is lift your problem, or understeer?
Understeer into the corner, mid corner, or corner exit?

Generic solutions are:
Softer front shocks/swaybar.
Raise the rear.
Stiffer rear shocks/swaybar.


I should not tell you these things or you will go even faster.

[davekmoore]

Seems the understeer may be driver error solved by braking more/earlier and entering slower with less steering angle, thus also avoiding the oversteer late in the corner due to too much steering angle left on.

Reckon the car would be faster down the straights and more stable in the corners if the front wasn't up at that angle so I'll try the coilovers downwards a touch at the front and up a touch at the back. Gotta be careful with this as there are already issues with tyre clearance at the front even after rolling and a bit of pulling of the guards. And it is a daily driver so speed humps have to be taken into account.

The DD aspect also means I can't have a splitter or air dam on all the time. Is there something that I can buy off the shelf or copy from someone else?

[Apu]

BYP have a quick release splitter kit for Hondas...the question is which one would best fit. It really is quick release - pull the pin, release a couple of bolts, slide the splitter off.

[bruce]

Negative front downforce? That'd be front end lift.
Suspension set up as others have said.

[greenMachine]

Google '949 racing crusher'.

[davekmoore]

Negative front downforce? That'd be front end lift.

Yeah, 'twas a play on words.

[davekmoore]

Google '949 racing crusher'.

That looks like the airdam in 5 of post number 124 here http://www.miataturbo.net/race-prep-75/ ... 612/page7/
Properly ugly but pretty effective and looks the cheapest and simplest to make and to fix onto the car when at the track.
Think I might try 3 though in order to still have air getting to the radiator, intake and brake ducts.

[lightyear]

You could start by taking the car to Nick for corner weighting. He will set it up with a bit of rake too.
You could borrow my front spoiler to see if it makes a difference. It is pretty quick to install and remove.

[Magpie]

Were you accelerating at the time of the photo?

Changing suspension settings will not have a great impact as they only control the way the springs manage weight transfer. Changing spring rates will, but it could end up way too stiff and cause other handling issues. However increasing both spring rates will decrease body roll.

Again the oversteer is a weight transfer issue, that is too much weight transferred to the front over powering the tyre grip. As suggested by others this can be solved by braking earlier and less speed. You could stiffen the front or soften the rear shocks or lower front tire pressure or raise the rear.

Another solution is aero. Instead of a splitter a wing with an angle of attack that causing the nose to be pushed down. However this will reduce the weight on the rear and possibly cause lack of grip.

[davekmoore]

You could start by taking the car to Nick for corner weighting. He will set it up with a bit of rake too.
You could borrow my front spoiler to see if it makes a difference. It is pretty quick to install and remove.

It has 1/4" of rake. Going to 1/2" today while swapping the brake pads.
Yes, would love to borrow your spoiler please before deciding to make/buy something. Great offer. Thanks. Sandown?

[davekmoore]

Were you accelerating at the time of the photo?

Flat in 5th so some acceleration happening. Not as much as when in a lower gear.

Another solution is aero. Instead of a splitter a wing with an angle of attack that causing the nose to be pushed down. However this will reduce the weight on the rear and possibly cause lack of grip.

Will take up Lightyear's kind offer of a loan of his front spoiler. If this effectively lightens the rear I'll live with that as I reckon a bit of oversteer would be quicker than the present understeer.

[Magpie]

Understeer is easier to manage and correct, lift off the throttle!

If you know the weigh at the front/rear, CoG, wheelbase and g force you can calculate the weight transfer. Knowing this will help you push the limits on braking later or earlier to avoid under/over steer. However you then need to consider surface conditions and tires for mechanical grip as well as weight transfer and suspension settings.

Changing springs will only change how far the front/rear compresses as it will always be the same weight. The dampers control how fast/slow the weight transfer s made.

[davekmoore]

Understeer is easier to manage and correct, lift off the throttle!
If you know the weigh at the front/rear, CoG, wheelbase and g force you can calculate the weight transfer. Knowing this will help you push the limits on braking later or earlier to avoid under/over steer. However you then need to consider surface conditions and tires for mechanical grip as well as weight transfer and suspension settings.
Changing springs will only change how far the front/rear compresses as it will always be the same weight. The dampers control how fast/slow the weight transfer s made.

Gotcha.
Lifting off to counter understeer feels slow all the way round the corner and seems to result in exit oversteer and wheelspin, as evidenced by the fact that at least one normally aspirated car was within 0.012 seconds of me at Calder last Sunday. I'm going to try braking earlier and more, and entering slower.
There's 1/2 and inch of rake on the car now and it's still ok at 30kmph over 20kmph speed hums.
It has Tien coilovers and I'm wondering if I could drop the top two adjusters down to lower the preload on the spring?

[lightyear]

Yep, you can use it at Calder. Your springs shouldn't have any preload if the wheels are off the ground.