Duke

Went for a second test drive of the new Leda suspension the other night..
Feels incredible!

Stock 951 -89 with stock wheels and 6 year old street tires.
Only mods was the new Leda coilovers and removed rear torsion bars.

This test was done before alignment etc...just straight out for a test drive! IMHO looks pretty good

Lemming

Love it, my Ledas were shipped this week, and I'm also doing front and back. My 924S track car sporting R-compounds and lots of camber should be screaming through those turns. What weight springs did you go with?

Serge944

You realize its impossible to get more than 1 lateral G without downforce? That is assuming your tires have maximum friction (constant of 1). How much downforce does the 951 have? I'm just curious because the lateral acceleration will increase with speed.

Scott at Team Harco

This may have been true a few years ago - before good tires were developed. It is now quite common for a car with good suspension and good tires to exceed 1.0 G lateral.

I regularly exceed 1.0 G with my Colt on sticky rubber. You tell me how much downforce this $hitbox generates.

However, I am skeptical of the data shown in the above graph. 6 year old street tires are not likely to promote 1.0 G lateral acceleration.

MichelleJD

Yikes on that 2nd pic!

I'm jealous of your new Ledas

Serge944

Well, at speeds, you always have some downforce. The air going over your windshield, and such. Imagine a perfectly streamlined car - you'll never reach over 1.0 g, even on the best rubber.

mroberts

Actually, a car is more likely to generate lift that downforce - it's shaped like a wing. It takes some work to remove that lift, and even more to get positive downforce.

Scott at Team Harco

No. Not sure where you learned about vehicle dynamics or tire dynamics. Most passenger cars actually exhibit lift at higher speeds.

As for rubber - there are tires that have been manufactured for years that permit lateral forces well in excess of 1.0 G (without the aid of aero downforce). It is in the micro mechanics of the interface between the tire and the road that makes this possible.

At Formula SAE each year there are cars getting better than 1.4 G at the skid-pad competition. The radius of the skid-pad is something like 25 feet. The speeds are very low. There are a few cars that use aero devices to generate downforce - but most do not. This is all mechanical grip between the tire and the "road".

You may want to do your homework on this.

Mongo

$1750 for the kit for 944s doesn't seem really that bad of a price. Now I just have to go hump my boss' leg for a raise to get sharp handling like that

Scootin159

I've always wondered...how does the Gtech know your RPM? The rest of it's data I imagine comes straight out of the accelerometer in it, but the RPM's confuses me.

mroberts

I *think* it pulls it out of the ripple on the cigarette lighter power

Serge944

Coefficients of friction over 1 - that is new to me. The vertical force on a car is the coefficient of friction multiplied by the normal force (mass x gravity). Whenever your lateral force is greater than this vertical force pushing down on the car, the car will lose grip. Could you please explain this phenomena to me? Is there a "glue" effect between the tire and pavement.

bleucamaro

This is where you prove to your physics teachers that they don't know anything about cars. there is no friction involved. Tires use mechanical grip. If you take a tire, and cut a cross section out of it, then put it on a road surface and put a bunch of weight on it, you will see that a tires rubber conforms to the road surface and mates with the roughness like a cog on a gear. When a tire has a hard compound it doesn't lock as well to the ground as one with a soft compound and produces less grip. But what about when a tire skids? A tire is breaking chemical bonds when it skids.

If you get some prof. waxing allegorical about how friction doesn't have anything to do with area politely raise your hand and ask him why drag racers and F1 cars need big tires.

cliff's notes: grip != friction.

Scott at Team Harco

As mentioned above - it's not glue - it's conformation to the irregular surface. The more accepted term is "mechanical keying".

There is a very good book on the subject: "The Racing & High-Performance Tire" by Paul Hanley.

In Mr. Hanley's book there is a table of friction coefficients. Rubber on dry glass has a Cf of 2+. Now wouldn't that be something if we could race on glass?

There is theory and there is practice. In practice - theory does not always hold up.

Manning

And a very interesting article on the subject a month or so ago in Racecar Engineering magazine