Drifting Suspension Design

[bribyk]

As I'm now done with FSAE, I need a new project. I'd like to build a drift vehicle as it's fun and I'm not that quick. I have been able to find little on suspension design and/or setup for a drift car. I would think you'd start with a solid grip suspension (minimal RC migration relative to CG) and maybe add some rear toe-in to start the slide easier and make it more controllable. Anyone have experience or know a good source for drifting suspension?

[bribyk]

As I'm now done with FSAE, I need a new project. I'd like to build a drift vehicle as it's fun and I'm not that quick. I have been able to find little on suspension design and/or setup for a drift car. I would think you'd start with a solid grip suspension (minimal RC migration relative to CG) and maybe add some rear toe-in to start the slide easier and make it more controllable. Anyone have experience or know a good source for drifting suspension?

[R/TErnie]

www.unnaturalinc.com (http://www.unnaturalinc.com)

I used their dyno a couple of times...they're all a bunch of dorifito's. They will know. Ask for Wes.

[Jersey Tom]

Live / solid rear axle, hard tires, plenty of power?

[bribyk]

An independent rear would surely be much more controllable and tunable. I am hoping for some more technical info on what to aim for in designing the ultimate drift suspension. Perfect camber gain, high roll stiffness contribution from ARB, no roll center migration?

[Wesley]

(not this Wes)

As a disclaimer, I am absolutely no suspension guru.

That said, I would imagine you are correct - since a lot of the lateral force comes directly from engine torque (your rear mu being that of kinetic, not static friction) you would want a very high roll stiffness - less weight transfer side to side, and more longitudunally. Your camber gain in dive, and especially squat for the rear tires will be fairly important - you want to maximize the contact patch for longitudinal force delivered by the engine. I would think drift cars would be in a form of perpetual squat around corners because the cornering force is acting so much along the cars longitudinal axis.

Make sense to anyone more knowledgeable?

[drivetrainUW-Platt]

Build a drift truck. Do the math, 300hp rear wheel drive, no weight over rear axle.

[Jersey Tom]

Interesting. The ultimate 'drift' suspension.. how does one define that? 'Good' drifting means poor rear grip, no? Or just stupid amounts of drive torque. You'd think, just build a suspension with crap mechanical grip in the rear.

There had been talk for a while of converting one of our old SAE cars (2004 perhaps) into a drift machine by making it some sort of solid axle rear.

[Wesley]

You can engineer it, or you can back-woods brawl it.

In my entirely unbiased musclecar heritage opinion, you could stroke a big block of your brand choice to ~550 cubes, throw a mild cam and decent set of heads on it, and make 500 lb-ft of torque at about 2.5RPM. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

I don't care how you design your suspension - you're going to drift when you put your foot down. Doing it controllably? Well, you must not have watched Dukes of Hazzard. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[John Valerio]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wesley:

you would want a very high roll stiffness - less weight transfer side to side, and more longitudunally. </div></BLOCKQUOTE>

well you still have the same amount of load transfer (LLT = lateral Gs * CG height / track width). you still want the car balanced even when sliding, so i think that cranking the rear roll stiffness will help you on turn in and achieving your yaw angle but you will still have a mad oversteer tendency.

i havent really thought about it until now but i think if you have a TLLD only slightly higher in the rear, but you crank the rear low-speed damping up higher than the front, on turn in you will break loose in the rear at first, and then when the final roll angle is achieved (i.e. the dampers aren't moving anymore) the car will balance itself back out and you can drift up and down spiral ramps in parking lots. seems to makes sense, but i could be way off.

[Pete Marsh]

Competeitive drifting is harder than it looks. The competition is decided on drift angle, continous drifting, closeness and copying of the lead car and if possible, passing while drifting. Its also a knockout type deal so you can't blink.

The cars have to be faster than you think to keep up with the top guys. If you are slow, when your second the lead car will disapear into a cloud of smoke and be hard to copy. When your in front they will be all over you, pushing under your car in the corners or just driving around the outside of you. You will loose even if your solo show is good.

Don't worry about initiating the drift, thats what the power and hand brake are for. Both the engine and hand brake need to be really good. Responce and control, lock or turn the tyres hard at will.

Rear camber control is the difference between 4 runs or 2 runs per set of tyres. A blow out puts you on the trailer for the event and if you are cutting the edges down they blow easy.

Not enough tyre or weight on the back will make you too slow, but you have to have the power.

To make it nice while sideways I would increase front corner springs and adjust caster to tune the feel of it. Add a driver adjustable rear bar. Get rid of any Akerman so toe is stable and mod for more steering lock. Dial off the back brakes and practice left foot braking, this will help increase the angle while going straight or holding the same radius.

Have fun.
Pete.

[Figlio_del_Diavolo]

Not a suspension design thing, but a drift handling related bit of info for you.

When I was out at Pikes Peak for the hill climb the last two times I went, main sponsor Falken had a drift showoff the following day at PPIR with several of their sponsored cars there. The way they were mounting the tires was something that I found pretty interesting. They mounted tires with a width smaller than the rim so the sidewalls looked like this \_/. I talked to some of the guys working on the cars and they told me it gives the car a much more progressive and controllable breakaway. Obviously the suspension is gonna play a big part here, but this seems to improve the controlability of the initial stages of the drift.

[John Valerio]

[QUOTE]Originally posted by Pete Marsh:

Both the engine and hand brake need to be really good.[QUOTE]

handbrake on entry i suppose, but i was going for more of an elegant solution.

[VFR750R]

Don't forget about front end geometry. I've heard that caster plays a big role in 'feel' of a cars drift angle and is one of the big reasons 240sx's( or everywhere else, Silvia's) are so good at drifting.

Although I'm no drifter, the King of drifting would have to be World of Outlaws sprint cars (I hope no one here will argue) and the car is setup to drift but the right front tire has enough caster and scrub it can effect the 'wedge' and therefore grip in the rear. To some degree the car is setup for an optimum yaw angle with front end geometry. I would take a look at those cars or even dirt anything for ideas that can be applied to pavement drifting. Obviously the 'roundy round' nature of dirt means some things don't apply, but there are similarties.

When designing an engine package obviously hp lets you drift more at higher speed, but throttle response and especailly throttle linearity can make a non driving mofo look like a hero. This seems to rule out 500hp turbo 4 cylinders but I guess once you're a pro and have the suspension dialed in, you can have any light switch motor work.

[absolutepressure]

You're all wrong, you need tracks to get ahead of the game in drifting. Couple more turbos and you could do that on pavement.
http://youtube.com/watch?v=xhbBWNcV5dA

After watching a bunch of drifting vids, I believe that there's a small slip angle in the front too, so none of your tires are ever in static friction. I know while drifting on snow they're not. I also know from watching some Formula D that grip is actually a good thing. Drivers want a lot of grip, and do better on grippier tires because it allows them to achieve bigger slip angles in the rear while staying in control, and it also allows them to go faster.

Trucks are definately not the answer. You want a balanced vehicle. The light rear end of a truck will just whip around the heavy front end. It's easier to kick out sideways than to move a heavy mass. So, in order to go anywhere, you'll be limited to fairly small slip angles...lame. And 300hp isn't gonna cut it. The cars have more than 500hp, and the viper? Idk, but well over 600 probably.

Compare the slip angles and speed cars (http://videos.streetfire.net/search/drift/2/21e139f7-02b6-434a-9393-993000b659ca.htm), big truck (http://youtube.com/watch?v=kInvYbesVa0), see? no forward movement, just a whip (http://videos.streetfire.net/search/sierra+drift/0/2036d9c9-479d-4459-9b5d-992a007fb869.htm), and of course, they're too tall (http://videos.streetfire.net/search/jeep+flip/0/0fbe41a7-60dd-4a95-9706-983e00a6c310.htm)

Just as a little extra as I was cruzin youtube, holy crap! The throttle response! It's like a delta rpm of 20k in .15secs! http://youtube.com/watch?v=gSHToyGIxWE&mode=related&search=

[james17]

This is your lucky day, no suspension design needed, I have a setup and tested drifter with documentation and all! It is my daily driving/ drag racing/ autocrossing tow vehicle and comes with free 5 mpg mod! It is a low miles (250K ish more or less???) 1984 C10 with a small block built for torque, toyo proxes STs, 3:42 gears and a 2500 RPM converter. I promise, in the 3 or 4 times I have autocrossed it drifting has been no problem at all! Tow your FSAE car, drag race your heart out, support your local oil company, and drift until the motor finally lets go... Cash only, local delivery avaliable...

[bribyk]

Your lateral load transfer would decrease due to the extreme yaw angle (like effective Mach number on a swept wing) and a corresponding amount of longitudinal load transfer would occur during steady-state drifting.

I would agree that steering geometry would be very important to get right. The lateral tire stiffness gained by mounting an under-width tire should make the car less nervous at high slip angles and should soften it's lateral force curve making it easier to control.

I would think that getting the car to take a controllable set (read: slide) would be the most important aspect. These cars don't just oversteer on turn-in, they kick the clutch pedal to break the rears loose. E-brakes are for mid-slide only.

Paul Morton's book "How to Drift" (great book on technique but little technical info) recommends a F/R weight distribution of around 53/47. A small Nissan truck (yes, I am building a drift truck, that's how we roll up here) has a weight dist of about 56/44. I don't think it would be too hard to get closer to the "ideal" by moving parts around (i.e. lower and rearer with the drivetrain). I just need to find an independent rear end that can handle the abuse, preferably domestic as they're cheaper (Ford Explorer?).

Keep those great replies coming (any drift tire engineers out there?).

edit: PS - Thanks James but I've already got a newer one in black. Mud terrains are much easier to initiate oversteer with.