mark kibort

Thats more like it. Now, if they really wanted to see what the difference was between them and you, all they needed to do was look under your helmet.

RKD in OKC

Out of curiosity, what I am supposed to call what I am adjusting when I adjust the rebound for more or less body front to rear roll to balance the grip when I initially apply throttle or brakes?

mark kibort

I dont know, but you can start here:

http://autopedia.com/stuttgart-west/...Physics01.html

Weight transfer has nothing to do with suspension, and everything to do with Cg height, wheel base and weight/bal of the car. The suspension's job is to keep the wheels flat and in contact with the ground.

worf928

RDK. Give up. Physics works differently for MK. You can feed the animal but do not attempt to pet it.

O?? RLY?

How is it then that changing ride height on one end of the car will change static weight distribution front to rear?

Must only work up here in Yankee Land.

RKD in OKC

Okay, I did the perfunctory reading and more technical term research.

Mark is correct in that the AMOUNT of weight transfer is set by CG, weight, and wheelbase. However, the RATE of weight transfer is a function of the SUSPENSION. I think Mark has been mistaken as I have been talking about adjusting the RATE of weight transfer NOT the AMOUNT. Or to be more precise the timing of weight transfer with respect to the function of the bias valve and rear braking.

Also, softer rebound allows lift which moves the CG and not just vertically, the movement of the CG allows MORE weight transfer...not very much, but it is enough to make a difference to an otherwise balanced setup.

mark kibort

Wolf,

Are you serious?

Let me clarify. weight transfer has everything to do with weight, Cg height, and wheel base. To the extent that suspension can change Cg height, is the amout it can effect weight transfer. It is a small factor of the weight transfer in handling, acceleration and braking.

Actually, that is a great example of what im talking about. go ahead, change the ride height front to rear and see what it does to weight distribution.
All you end up doing is changing the Center of Gravity hight. (which will ever so slightly change weight distribution, front to rear). What you can change is cross weight balance or corner weights.

Again, there is no weight transfter due to squat or dive. It has ONLY do do with physics dictated by wheel base, weight and Cg height.

You are totally confused on what the suspension is used for. Just because you can predict some of the effects of suspension changes, doesnt mean you undertand the principles.

Where are you guys getting this stuff (or thoughts)?

mk





ride

RKD in OKC

Shocks and RATE of weight transfer.

Turnfast.com Last Paragraph.

Also...

http://www.turnfast.com/tech_handling/handling_shocks In the SUMMARY

mark kibort

Now you are pointed in the right direction, but still a little off the mark. The rate of weight transfer is a function of tire grip and forces which create the forces of acceleration or decelleration, both in the longitudinal and lateral planes. The ability of the tires to create these forces can be a result of the optimization of tire postion on the road. (suspension adjustments, shock, spring, settings). The rate of weight transfer is directy proportional to the rate of acceleration.

You keep on drawing from your intuitive feelings of the car rockering back and loading up the rear wheels and thoughts that the weight is transfered because of it. This is not entirely true.

Your last statemement is not true either. the raising of the Cg is not good. for a given rate of acceleration or deceleration, the forces will have to go up. In otherwords, you can get a greater rate of deceleration with the Cg hight lower for a given force at the tires. This is why we spend so much time lowering the race car!

I feel we are getting closer to agreement.


mk

mark kibort

Good article.

As you corrected yourself and Wolf must be shaking his head in embarrasment, the article says:
"Contrary to what you may be inclined to believe, the amount of weight transfer is not altered by springs, shocks, anti-roll bars, etc. Weight transfer is a result of inertia and momentum. These suspension components cannot change that. What these components can do is impact how much the suspension moves in response to the load change, and how quickly the load transfers to the tire contact patches."

This all goes back to driver style, input, and compliance. Weight transfer rate is certainly assisted by sprngs and shocks. That has not been in question.
Again, many factors.

Mk

RKD in OKC

I think you need to re-read my first post dude. EVERY place I mentioned weight transfer I qualified it with RATE.

mark kibort

Your right. I was not reading your post correctly initially. I corrected that part of my last post. That certainly added fuel to the fire. Sorry about that. Other were talking about weight transfer and I was speaking to them in my responses.

the flyin' scotsman

Not getting into the physics debate but shall provide input based on my racing experience on GP motorcycles:

Different race tracks require different suspension set ups even though the horsepower of the machine and weight of racer remain constants. Why?..........the corners have different radiuses, different angles of flatness, camber etc, longer straights giving higher approach speeds requiring harder braking. We would alter spring rates, suspension fluid levels and viscositys, change the position of the shocks in both front and rear of the machine and even change the engine position to later weight loading. Suspension was also fine tuned with changes to compression and rebound.

Changes became very effident in the grip levels on the front and rear tyres especially as the weight transferred from level distribution on the straights, full front while braking and somewhere inbetween when the brakes are released and the machine is pitched into the corner then loads the rear as the power is fed back on.

Suspension set up was such a black art we had Ohlins representatives advise the team at the various tracks we raced on.


On topic; I use the 33bar bias valve on my S4 for spirited (not racing) driving...........works much better than stock..........IMHO

mark kibort

All true on race cars as well. The suspension set up is a series of trade offs. Its designed to keep the tires at max grip possible for most of the time possible.
One set on one car will not be right for all drivers. The "rate of weight transfer" can be delt with in all sorts of different was with driving style. However bump, compression settings to keep the wheels on the roads, and not "jacking down", or "bouncing", the suspension, are universal settings for a given car on a particular road course at the same speeds and line.

On topic, if the 33 bar valve works now, what if you added 305s up front? suddenly, you could have x% more braking g's, and x amount more weight transfer to the front, and what was good before would be working the rear brakes more while they would have less weight on the rear tires. that could be bad.

worf928

mark kibort

Remember, you said changing ride hight can change weight distribution front to rear.

Wolf, the purpose of the suspension is to keep the wheels on ground as flat as possible. It also controls the RATE of weight transfer, but not the transfer itself. In general, we want as little movement as possible without having the tire bounce over bumps, and jack down in transisions.

Getting back on topic, we are still talking about fine tuning here, unless we are talking street cars on the street. again, in full threashold braking, the weight transfer could be near 800lbs. this leaves very little weight on the rear tires for braking effect. If you could dynamicaly change its effect of bias for straight line braking and turn in, that would be interesting. But, you cant. If I was to guess, you would probably want about 50-75% of max braking capacity on the rear to keep it from locking up under trail braking. Just think, 2500lbs up front and 500lbs on the rear tires. You tell me how much braking force you want in the rear as you enter a turn from 135mph . But, what do I know.

mk