CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[strat61caster]

Originally Posted by Tokay444

It is ridiculous to argue that 3 tires have more grip potential than 4 though.

Theoretically nobody should be arguing with you, you're right. You'll have more grip available with all four tires on the ground. We're agreed that this is in respect to driving hard and going for maximum performance right?

Practically speaking "grip potential" is less important than going faster, and often times going faster means lifting a wheel off the ground whether that be softening suspension to handle poorer sections of pavement (or daily driving) or the driver upsetting the car via hitting a curb or with purposeful weight transfer.

If four wheels on the ground was always faster drivers would stay off the curbs on racetracks, but they don't, time and time again the best drivers in the world upset the car on purpose because it helps find a faster laptime. Professional chassis engineers and amateurs choose softer springs than what may be optimal around a theoretical corner because being able to have the car settled over rough pavement or a big bump or two is usually worth more time than the two or three corners where not lifting a wheel could provide that extra bit of grip and a few hundredths of a second.

Keeping all four tires on the ground at all times is not top of the priority list, especially for us amateurs. Hey, if you know of a perfect setup out there that does everything, go promote it and sell it, you'll be at the very least able to afford a comfortable lifestyle. 99.99% of the time suspension is designed as a compromise, one of those compromises is usually lifting a wheel if the circumstance arrives there, and in the opinion of many, it's not worth getting your panties in a twist about it as long as the car is perfect in every other regard. Yes you can tune it out, but usually at the expense of some other aspect of the car's performance.

Besides, it means cooler pictures.

While googling for pictures I came across some interesting threads over at Pelican Parts, old school Porsche guys discussing this very thing almost two decades ago, people vehemently disagree, but funny enough, all the guys who say lifting a wheel is fine have pictures of their car on track... all the guys saying it's awful don't have any pictures of their cars on track...

[churchx]

"funny enough, all the guys who say lifting a wheel is fine have pictures of their car on track... all the guys saying it's awful don't have any pictures of their cars on track..." seemed best bit

[Racecomp Engineering]

Originally Posted by Gforce

I believe the context is driving around bends.

Well duh. I'm just throwing fuel on this fire. I like it when people think.

(I'm not in the "you must keep all 4 tires on the ground" crew).

Originally Posted by Gforce

Even if you have an awd car and even in a straight line you cannot achieve equal grip from all four tires. "Weight transfer" (unfortunately named as no weight moves) means it is impossible to obtain usable equal grip from four tires. But you know that, if you're a suspension supplier.

Sure you can, and with a little math it's not hard to figure out how (at least in a straight line).

- Andrew

[Tokay444]

Originally Posted by strat61caster

Theoretically nobody should be arguing with you, you're right. You'll have more grip available with all four tires on the ground. We're agreed that this is in respect to driving hard and going for maximum performance right?

Practically speaking "grip potential" is less important than going faster, and often times going faster means lifting a wheel off the ground whether that be softening suspension to handle poorer sections of pavement (or daily driving) or the driver upsetting the car via hitting a curb or with purposeful weight transfer.

If four wheels on the ground was always faster drivers would stay off the curbs on racetracks, but they don't, time and time again the best drivers in the world upset the car on purpose because it helps find a faster laptime. Professional chassis engineers and amateurs choose softer springs than what may be optimal around a theoretical corner because being able to have the car settled over rough pavement or a big bump or two is usually worth more time than the two or three corners where not lifting a wheel could provide that extra bit of grip and a few hundredths of a second.

Keeping all four tires on the ground at all times is not top of the priority list, especially for us amateurs. Hey, if you know of a perfect setup out there that does everything, go promote it and sell it, you'll be at the very least able to afford a comfortable lifestyle. 99.99% of the time suspension is designed as a compromise, one of those compromises is usually lifting a wheel if the circumstance arrives there, and in the opinion of many, it's not worth getting your panties in a twist about it as long as the car is perfect in every other regard. Yes you can tune it out, but usually at the expense of some other aspect of the car's performance.

Besides, it means cooler pictures.

While googling for pictures I came across some interesting threads over at Pelican Parts, old school Porsche guys discussing this very thing almost two decades ago, people vehemently disagree, but funny enough, all the guys who say lifting a wheel is fine have pictures of their car on track... all the guys saying it's awful don't have any pictures of their cars on track...

I'm glad we can see eye to eye.

[Gforce]

Originally Posted by Tokay444

I'm glad we can see eye to eye.

So, you both must think that springs and suspension affect maximum weight transfer.

They do not.

Weight transfer is a misnomer.

The weight transfer effect is the reaction forces to the forces generated by the contact patches parallel to the ground. These forces reach a maximum just before the car slides (or in the acceleration mode the drive wheels spin up ) or the vehicle inverts.

Therefore, maximum lateral cornering grip is achieved just before the vehicle spins or inverts. At that point, only the maximum possible grip developed by the tires on the outside of the bend matter. Perfect setup for maximum cornering speeds requires a wheel to lift in order to develop maximum grip. If an inside wheel isn't lifting and the car is still not sliding there is more speed to be found in those outside tires. This is just physics.

So, you will see that the grip developed by the tires on the inside of the bend can drop to zero and theoretically at least the car can continue to increase its cornering speed.

Each end of the car can be treated separately when considering maximum potential grip. A rwd car that loads its outside rear wheel at a faster rate than its outside front wheel is dangerous to drive and will be slower than a car that does the opposite. A fwd car that loads its outside front wheel at a faster rate than its outside rear wheel will be slower than one that does the opposite but will only be dangerous for a novice who does not understand power effects on traction. Awd cars are, well, different. I know of no awd car that is fast that does not lift an inside front wheel first.

Fastest cars always unload the inside tires in bends as much as can be achieved with the grip developed by the outside tires. Always.

[Gforce]

Originally Posted by Racecomp Engineering

Well duh. I'm just throwing fuel on this fire. I like it when people think.

(I'm not in the "you must keep all 4 tires on the ground" crew).



Sure you can, and with a little math it's not hard to figure out how (at least in a straight line).

- Andrew

I'd like to see those numbers since I do not think it is possible.

Weight transfer makes this impossible. Indeed, this is the Achilles heel of fwd cars and awd cars suffer from the same problem.

[Tokay444]

I found the first person to be added to my block list on this forum.
Except I can't find the block button...
Found an ignore button. That should suffice.

[nikitopo]

Originally Posted by Tokay444

I found the first person to be added to my block list on this forum.
Except I can't find the block button...
Found an ignore button. That should suffice.

I did the same ...

[Gforce]

F=ma

Where F is the lateral force generated by the tires at ground level which is equal and opposite to the "weight transfer" force. This force acts through a lever arm with the effective end at the height of the CG and the fulcrum at the outer tire contact patch I.e. at ground level.

m = the mass of the vehicle (referred to commonly but inaccurately as the weight)

a = the change in velocity, either speed or direction.

The resulting weight transfer force F is considered to act at the CG of the mass at some height off the ground. It is useful to also consider this effect as divided between two CG (ok since all CG are imaginary) one centred over the front axle and the other over the rear axle.

Until the outside tires slide F rises and is exerted as a torque trying to rotate the mass around its roll centre. The roll centre is similarly best divided into two, one each for each axle as the body rotates around the axis passing through both.

Confusion arises by conflating the rotation effect with the torque causing the rotation effect. The torque is unaffected by the springs or the suspension. Body roll is affected but, as far as grip is concerned, that is a so what situation.

Failure to fully understand the difference between body roll and weight transfer leads to incorrect suspension solutions being implemented.

[jvincent]

Originally Posted by Tokay444

I found the first person to be added to my block list on this forum.
Except I can't find the block button...
Found an ignore button. That should suffice.

You are relatively new to the forum so you missed his previous two incarnations on the forum, both of which ended up being banned.

[Gearhead1]

I want more front negative camber and positive caster for occasional track days. My BRZ is a daily driver including winters with sand and salt so I would like to avoid the noise/harshness/maintenance of spherical rod ends, plus I'm happy with the OE springs and ride height. I decided that having plates welded on the front subframe to move the rear LCA pivot point out 3/4" on each side might be a simple fix to move things in the right direction.
I haven't found a solution to the longer tie rods that would be required. '95 Mitsubishi Eclipse inner tie rods are longer, but only about 5/16", so I still need another 1/2" in additional length. Does anyone know for sure if the Eclispe inners will work and it they could be paired with, say, tie rod ends for a '95 MR2 (Moog pn's ES 3558 and ES3559)?
Any experience with tie rod extensions (Excessive Manufacturing lists Toyota Tie Rod Extensions-S1 14mm x 1.5 adapter)?
Any other advice?

[Tcoat]

Originally Posted by jvincent

You are relatively new to the forum so you missed his previous two incarnations on the forum, both of which ended up being banned.

Couple of the Best Of Collection (and on topic so relevant to this discussion):


http://www.ft86club.com/forums/showt...=71770&page=15


http://www.ft86club.com/forums/showthread.php?t=56887

[gramicci101]

Originally Posted by Gearhead1

I want more front negative camber and positive caster for occasional track days. My BRZ is a daily driver including winters with sand and salt so I would like to avoid the noise/harshness/maintenance of spherical rod ends, plus I'm happy with the OE springs and ride height. I decided that having plates welded on the front subframe to move the rear LCA pivot point out 3/4" on each side might be a simple fix to move things in the right direction.
I haven't found a solution to the longer tie rods that would be required. '95 Mitsubishi Eclipse inner tie rods are longer, but only about 5/16", so I still need another 1/2" in additional length. Does anyone know for sure if the Eclispe inners will work and it they could be paired with, say, tie rod ends for a '95 MR2 (Moog pn's ES 3558 and ES3559)?
Any experience with tie rod extensions (Excessive Manufacturing lists Toyota Tie Rod Extensions-S1 14mm x 1.5 adapter)?
Any other advice?

You're way overthinking this.

RaceSeng top mounts have adjustable caster and camber. RCE top mounts have adjustable camber and a fixed amount of increased caster. I think Velox increases caster as well, but I'm not sure about that. Any one of these will be cheaper and easier than slapping together mismatched rod ends and hoping for the desired outcome. If you really want an adjustable front LCA, SPL makes one ($$$) and RacerX can custom make one to your specs.

[Racecomp Engineering]

Also, why not camber bolts and the WL ALK for some extra caster? (if you want to avoid plates)

- Andrew