Managing lateral weight transfer
03-09-2014, 03:56 PM
#1
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Managing lateral weight transfer
I think we all have weight transfer for braking and acceleration figured out.
Transfer weight to the front and the brakes grip a lot better, which is why you squeeze the breaks.
Same for the gas, squeeze until you start transferring the weight, and you get more grip.
But what about lateral?
Are you guys trying to maximize it or minimize it?
How about quick transitions where you're bouncing back and forth, like a slalom?
How are you including tire slip angle into the mix?
Transfer weight to the front and the brakes grip a lot better, which is why you squeeze the breaks.
Same for the gas, squeeze until you start transferring the weight, and you get more grip.
But what about lateral?
Are you guys trying to maximize it or minimize it?
How about quick transitions where you're bouncing back and forth, like a slalom?
How are you including tire slip angle into the mix?
03-09-2014, 05:30 PM
#2
Melting Slicks
In transferring weight to the rear you are doing that to increase the grip on the rear wheels so you can accelerate faster, similar to the font, you are actually changing the balance of the car by moving weight fore and aft when you want and need to. Lateral is different, in that you aren't changing the balance so it's not the same.
This is where smoothness does come in to play, if you yank on the car it's going to get upset and not be as fast because the tires can't respond that fast. On a road course you want to be smooth all the time..
In some cases, though, depending on the balance of the shocks, you can get the car do act differently by applying steering more quickly, but that's generally not fast in that you are pitching the car to get it to do something that it really doesn't want to do.
That said, in some tight autocross situations you can "throw" the car through a very tight section and get it to go through at a speed that is much higher than it really should. I've done that a few times when I screwed up and went into a section that couldn't be taken nearly that fast and just threw the car and it worked.
Once I had a well endowed passenger who was talking and I was distracted and when I realized that I was in way way too deep I just stabbed the brakes, threw the car and it skittered, hooked, and I squeezed the gas as it shot through a very tight chicane... The announcer went nuts and the run was FTD for the day... But on the next run I tried it again and it didn't work.... It takes just the right combination of brake, steering input, and then throttle to pin the front tires yank the wheel, and the apply the gas to pin the rear tires....
Randy Pobst was the real master of this kind of technique. He could make cars do things that mother nature said was impossible..
This is where smoothness does come in to play, if you yank on the car it's going to get upset and not be as fast because the tires can't respond that fast. On a road course you want to be smooth all the time..
In some cases, though, depending on the balance of the shocks, you can get the car do act differently by applying steering more quickly, but that's generally not fast in that you are pitching the car to get it to do something that it really doesn't want to do.
That said, in some tight autocross situations you can "throw" the car through a very tight section and get it to go through at a speed that is much higher than it really should. I've done that a few times when I screwed up and went into a section that couldn't be taken nearly that fast and just threw the car and it worked.
Once I had a well endowed passenger who was talking and I was distracted and when I realized that I was in way way too deep I just stabbed the brakes, threw the car and it skittered, hooked, and I squeezed the gas as it shot through a very tight chicane... The announcer went nuts and the run was FTD for the day... But on the next run I tried it again and it didn't work.... It takes just the right combination of brake, steering input, and then throttle to pin the front tires yank the wheel, and the apply the gas to pin the rear tires....
Randy Pobst was the real master of this kind of technique. He could make cars do things that mother nature said was impossible..
03-11-2014, 01:52 PM
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The track is shorter than the wheelbase, so it changes even more.
I never quite got what people mean when they say "throw the car" into a turn, can you explain?
03-11-2014, 02:47 PM
#4
Safety Car
Rear lateral and front all run together in a smooth drive, you start off in the braking zone 100% forward g's transition to 100% side (albeit very briefly pending driving style) and then transition to 100% rear. It's the best way not to upset the car.
Throwing the car into a turn is usually present when someone is sawing at the wheel prior to apex (assuming no brake issues, or over trail-braking). You basically yank the wheel just enough not to throw the car into a drift, but to get most of the rotation done earlier in the turn. Might cost you a MPH, maybe two near apex, but you can jump on the throttle way earlier because you pretty much skip a big portion of the lateral transfer to rear. Work in tight quarters or quick transitions. You have to have good car control though. You see momentum cars do this quite a bit so they can get back to throttle quicker.
Throwing the car into a turn is usually present when someone is sawing at the wheel prior to apex (assuming no brake issues, or over trail-braking). You basically yank the wheel just enough not to throw the car into a drift, but to get most of the rotation done earlier in the turn. Might cost you a MPH, maybe two near apex, but you can jump on the throttle way earlier because you pretty much skip a big portion of the lateral transfer to rear. Work in tight quarters or quick transitions. You have to have good car control though. You see momentum cars do this quite a bit so they can get back to throttle quicker.
03-11-2014, 08:00 PM
#5
Melting Slicks
"Throwing" the car is using a fast large input of lock all at once to generate a high yaw rate. To do it effectively you have to transfer a lot of weight to the front wheels, do the steering input and then, as the car turns in, you have to roll on the power to shift weight aft and keep the back end from continuing to rotate around past the front end..
The rolling back onto the gas is important because by putting the weight on the back end it creates understeer.
This is primarily a low speed manuever, in that it's generally done in things like low speed offsets where you can gain a lot of time if you don't slow down as much and blow through them.
It's a lot harder to do with cars that have longer wheelbases because you have a hard time shifting as much weight fore and aft with a longer car. The first gen RX-7's were very "tossable" and you can do it with a C4, but a lowered C5 isn't very "tossable" at all.
The rolling back onto the gas is important because by putting the weight on the back end it creates understeer.
This is primarily a low speed manuever, in that it's generally done in things like low speed offsets where you can gain a lot of time if you don't slow down as much and blow through them.
It's a lot harder to do with cars that have longer wheelbases because you have a hard time shifting as much weight fore and aft with a longer car. The first gen RX-7's were very "tossable" and you can do it with a C4, but a lowered C5 isn't very "tossable" at all.
03-12-2014, 11:48 AM
#6
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Ok that's what I'm doing with the heavy braking, but I'm not managing to get the weight back to the rear tires
https://www.corvetteforum.com/autocr...rn-in-but.html
https://www.corvetteforum.com/autocr...rn-in-but.html
03-13-2014, 04:26 PM
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I've read all the books
Looking for different perspectives
I know FWD cars go faster with 3 wheels on the ground.
Most RWD & AWD cars try to keep all 4 on the ground.
Though BMW's go faster pulling the inside FRONT tire off the ground.
Looking for different perspectives
I know FWD cars go faster with 3 wheels on the ground.
Most RWD & AWD cars try to keep all 4 on the ground.
Though BMW's go faster pulling the inside FRONT tire off the ground.
03-13-2014, 07:59 PM
#8
Intermediate
Usually best to think in terms of the available traction at each tire. Loading two tires with the weight of the entire vehicle (lifting two tires off the ground in transition as an extreme example) is, in theory, no different than loading all four tires. You have twice the load acting on half the contact patch. This is OK to a point but eventually ultimate traction starts to fall off as you overload the tire. You're always better off limiting the weight transfer so you can distribute tire load as much as possible. I suspect "pitching" the car occasionally works when the sudden input causes the chassis to respond before the "sprung" part of the car has had a chance to catch up. Once it does I would expect a slide. Sorry for geeking out but this is a great subject.