A question for the slalom racers, Why is front-end so stiff you lift a wheel Options

[stewteral]

Hey Slalom Guys,

I've been bothered by the pics of your cars lifting the inside front wheel under cornering. Years ago, this was the set up for 911's to adjust away from the car's oversteering nature.

However, from my past experience I've found that a car that would be too oversteery for the track would be about right for slaloms. As I saw it, it was most important to get the front end to turn-in crisply to carve the very tight turns.

So what don't I understand about running 914's? Are your courses so fast now the a loose car will get away from you? The fastest course I ever ran just barely
got Dad's old Cobra into 2nd gear (80 MPH).

Best,
Terry

[BMXerror]

I've read your post several times and still don't understand your question, so I'll start from the top.
-911s lifted the inside front wheel for exactly that reason. They were a bit tail happy, so they either softened the rear and left the front alone, or stiffened the front swaybar. It's the ability to roll in the rear (lack of a substantial rear bar) and disability to roll in the front (heavy bar) that results in it picking up the inside wheel. It's the same exact thing with 914s, because they like to oversteer a bit under steady state cornering too.
The reason they didn't just go to a heavy rear bar to reduce roll is because it would unweight the inside rear wheel and make it difficult to put the power down out of the corners. I was actually just doing back-to-back testing on the BMW that I race with and without a rear sway and finding the same thing. Front engine, rear drive, but the principle is still the same. The opposite is why front wheel drive cars lift the rear tire mid corner. I'm not sure why you're "bothered" by it. How it looks is not as important as how it works.

-I can't speak to track days because I've never done any, but I do know from autocrossing on many different surfaces that the balance of the car is very surface dependent. In general, the less grip a surface has, the more oversteer will be felt from the driver's seat. This is usually a result of how wavy the pavement is and how that relates to your spring rates. Basically what I'm trying to say is it's very difficult to judge car balance from the track to an autocross course, unless you autocross on the track surface.
We try to achieve balance on an autocross course just the same as you do on the track. You do want the car to rotate around the quick-flick type elements, but those are few. If you're too tail happy the car will be unsettled in the slaloms. If you make it too settled in the slaloms it'll be pushy, and you'll just burn time through the sweepers. However I can't really speak to the relationship between a track car and an autocross car. It may have something to do with the relationship between how fast you're eating up pavement and your wheel rate which is considerably different between the two. But that's a bit over my head, so I won't venture a guess.

-In SCCA autocross a fast 914-6 will top out at 65ish (correct me if I'm wrong all you FP guys) and I know PCA runs a bit faster. I've seen 80 in my 1.7 (in a parking lot) at a rather unusual PCA autocross, but that was ridiculous! No. We don't run all that fast. But a car that's too loose will get away from a driver that's too green at any speed.

I hope that helps. Not sure if that answers your question or not.
Mark D.

[URY914]

I think some of the pictures you see of 914's lifting a wheel is due to a combination of track surface and if the pavement it level. I've got a picture of my car with the front tire 3" off the ground and it looks impressive. In fact the corner exit was at the top of a rise in the parking lot and the tire lost contact with the surface.

Rear grip, weight transfer, pavement level, apex, car set-up, etc, etc, etc...

[J P Stein]

I think some of the pictures you see of 914's lifting a wheel is due to a combination of track surface and if the pavement it level. I've got a picture of my car with the front tire 3" off the ground and it looks impressive. In fact the corner exit was at the top of a rise in the parking lot and the tire lost contact with the surface.

Rear grip, weight transfer, pavement level, apex, car set-up, etc, etc, etc...

Many's the time we carried the inside front all the way around a long (for AX) sweeper. Since no other 914 could beat us with any regularity we didn't worry about it.

The car was set up fairly soft for our local very lumpy venue. It could be made to keep all 4 on the ground in a corner, but the trade off would be non-contact over the bumps......that would be slower & break parts.
We got hooked on occasion when running on nice smooth concrete....that means a 914 beat us on the 2nd day of a 2 day event....but not enough to take the overall.
We were 750 miles from home and he wasn't.

Another pic on asphalt.

[stewteral]

I think some of the pictures you see of 914's lifting a wheel is due to a combination of track surface and if the pavement it level. I've got a picture of my car with the front tire 3" off the ground and it looks impressive. In fact the corner exit was at the top of a rise in the parking lot and the tire lost contact with the surface.

Rear grip, weight transfer, pavement level, apex, car set-up, etc, etc, etc...

Many's the time we carried the inside front all the way around a long (for AX) sweeper. Since no other 914 could beat us with any regularity we didn't worry about it.

The car was set up fairly soft for our local very lumpy venue. It could be made to keep all 4 on the ground in a corner, but the trade off would be non-contact over the bumps......that would be slower & break parts.
We got hooked on occasion when running on nice smooth concrete....that means a 914 beat us on the 2nd day of a 2 day event....but not enough to take the overall.
We were 750 miles from home and he wasn't.

Another pic on asphalt.

Hi JP,

Thanks for your explanation as your pics were among those that bothered me. Now I see that it was an issue of lumps & bumps and not severely stiff front spring rates.

I must admit that while your pic of the car has one of the front tires off the ground, the other 3 look beautifully PLANTED on the road surface.

Given the BIG toe-in change in the rear through suspension travel, I'd be interested to know what your static setting are. For a stock suspension car, I have been advised to set static toe at 0 to 1/8" toe out.

enjoy,
Terry

[J P Stein]

Static camber was set at -.5 front & rear....bias ply tires. I fooled around with toe quite a bit and ended up with 0 toe f & R. Toe out made the car too squirrely under heavy braking & corner entry....AX is a game of inches. 21mm T bars & 275 lb springs. Since one doesn't get many chances at a course (3 passes at SCCA), IMO making the car easy to drive all over the range of crap course designers throw at you......everything to long sweepers to 180 deg single cone pivot turns, tight spaced slaloms, wide spaced slaloms, variable length cone slaloms. Basic oversteer to help rotate the car...but not too much. Tire pressures were all we fooled with at an event. Got a bit carried away with lowering the rear in that second picture.....bout rolled the tire off the rim, oops. It scared the crap outta me when I saw that pic. (IMG:style_emoticons/default/w00t.gif) never went below 20 psi after that....19 in front.
22mm AR bar set half hard is enough to lift the inside front. On a butt smooth surface a lot stiffer/lower setup would be the cat's ass and all that flopping around would be gone. I drove a track set up 914 on our venue once. It was at least twice as stiff as mine & it was undriveable there.

My car carried only about 350 lbs on each front wheel. As you can see the total front weight often was transferred to the outer front (some went aft, of course)
The shocks were very soft in rebound & just stiff enough in jounce.....even then it would rattle your eyeballs....(literally) double vision on the rough patches.

Did I say our home venue is rough? A bad patch.This could be avoided...once ya knew it was there. The natural line took you there tho.

[SirAndy]

How about lifting two wheels? (IMG:style_emoticons/default/biggrin.gif)


https://www.youtube.com/watch?v=Pb_VjzyZODs



(IMG:http://www.914world.com/bbs2/uploads/post-179-1147909420.jpg)

[SirAndy]

And one more. Right after that pic was taken, the car got up on two wheels! Notice the lift in the rear ... (IMG:style_emoticons/default/w00t.gif)

That was the first time it did that, the video posted above was the second time.

(IMG:http://www.914world.com/bbs2/uploads/post-2-1116816965.jpg)

[stewteral]

Static camber was set at -.5 front & rear....bias ply tires. I fooled around with toe quite a bit and ended up with 0 toe f & R. Toe out made the car too squirrely under heavy braking & corner entry....AX is a game of inches. 21mm T bars & 275 lb springs. Since one doesn't get many chances at a course (3 passes at SCCA), IMO making the car easy to drive all over the range of crap course designers throw at you......everything to long sweepers to 180 deg single cone pivot turns, tight spaced slaloms, wide spaced slaloms, variable length cone slaloms. Basic oversteer to help rotate the car...but not too much. Tire pressures were all we fooled with at an event. Got a bit carried away with lowering the rear in that second picture.....bout rolled the tire off the rim, oops. It scared the crap outta me when I saw that pic. (IMG:style_emoticons/default/w00t.gif) never went below 20 psi after that....19 in front.
22mm AR bar set half hard is enough to lift the inside front. On a butt smooth surface a lot stiffer/lower setup would be the cat's ass and all that flopping around would be gone. I drove a track set up 914 on our venue once. It was at least twice as stiff as mine & it was undriveable there.

My car carried only about 350 lbs on each front wheel. As you can see the total front weight often was transferred to the outer front (some went aft, of course)
The shocks were very soft in rebound & just stiff enough in jounce.....even then it would rattle your eyeballs....(literally) double vision on the rough patches.

Did I say our home venue is rough? A bad patch.This could be avoided...once ya knew it was there. The natural line took you there tho.

Hey JP,

I think I understand your setup: not much camber as the chassis is stiff enough not to roll much. Roll is the worst thing for a 914 as the loaded rear wheel toes-in
.100" for each 1 inch of compression.
I appreciate playing with toe can have some benefits: a little front toe-out is said to aid turn-in, but I found that anything more than 1/16" made the car so nervous there was NO relaxing on-track. The rear is another story: 0 toe is a great place to start, but some toe-out could help the car rotate. Of course, how much and when to make the adjustment will only work if you know you'll run a tight or high-speed course.

I'm in 100% agreement: a car that is easy to drive is a fast car.

Enjoy,
Terry

[EdwardBlume]

Sharp turn grippy tires... and you can Dukes o Hazard anything. When you get to a higher level of racing, its good to figure out how best you can keep it all down as best you can.

[EdwardBlume]

I think some of the pictures you see of 914's lifting a wheel is due to a combination of track surface and if the pavement it level. I've got a picture of my car with the front tire 3" off the ground and it looks impressive. In fact the corner exit was at the top of a rise in the parking lot and the tire lost contact with the surface.

Rear grip, weight transfer, pavement level, apex, car set-up, etc, etc, etc...

Many's the time we carried the inside front all the way around a long (for AX) sweeper. Since no other 914 could beat us with any regularity we didn't worry about it.

The car was set up fairly soft for our local very lumpy venue. It could be made to keep all 4 on the ground in a corner, but the trade off would be non-contact over the bumps......that would be slower & break parts.
We got hooked on occasion when running on nice smooth concrete....that means a 914 beat us on the 2nd day of a 2 day event....but not enough to take the overall.
We were 750 miles from home and he wasn't.

Another pic on asphalt.

In this pict, you can see the weight of the car is on the rear tires (roll under) but not so much on the front. It tells you that Brit is accelerating out of the corner while still turning, but there's not much holding the front down. Might be quicker to put more gas in the tank.

[6freak]

drive n your ass off will get tires off the ground every time

Pacwood Wa ... Old Hampton mill 2010 914shootout

[6freak]

nutter one just for fun

Same venue

[Randal]

And one more. Right after that pic was taken, the car got up on two wheels! Notice the lift in the rear ... (IMG:style_emoticons/default/w00t.gif)

That was the first time it did that, the video posted above was the second time.

(IMG:http://www.914world.com/bbs2/uploads/post-2-1116816965.jpg)

I remember Bill P. doing the same thing with his 911 race car at Alameda on a tight turn. You could see the bottom of the car he was up so high. Pretty scary even watching it happen.

So, what do you think caused this radical, up on two wheel, event?

My guess: Rob is right, grippy tires and a tight turn.

[ChrisFoley]

Its not just autocross 914s that pick up a front wheel while cornering. (IMG:style_emoticons/default/biggrin.gif)

I had outbraked the zee going into Big Bend.
The picture was taken as I turned toward the 2nd apex.
Speed - about 75mph.

[Randal]

Its not just autocross 914s that pick up a front wheel while cornering. (IMG:style_emoticons/default/biggrin.gif)

I had outbraked the zee going into Big Bend.
The picture was taken as I turned toward the 2nd apex.
Speed - about 75mph.

OK we are impressed, your car is just stuck to to that corner. You must know someone that builds good suspension components!

What tires you running?

[ChrisFoley]

What tires you running?

Hoosier R45A cantilever slicks at that time (2004).

[6freak]

i think Mr Andy gets (IMG:style_emoticons/default/first.gif) for the amount of air under the tire...maybe 225lbs rear springs might help that ??

[URY914]

Me in about 1997 at Sebring.

[SirAndy]

i think Mr Andy gets (IMG:style_emoticons/default/first.gif) for the amount of air under the tire...maybe 225lbs rear springs might help that ??

I went with 250lbs rear springs after that picture was taken. I also added a rear sway bar.

(IMG:style_emoticons/default/driving.gif)