Handling & ride height. How low is too low...

I have been looking at some charts of suspension design and geometry.

 

Common knowledge states that lowering the car will lower the center of gravity and improve handling. This is true up to a point given that your suspension was designed to handle the ride height.

 

The thing that intruiged me the most was the camber curves of a mcphearson type suspension. Most notably the L-arm rotation in relation to ride height.

 

It seems that if you lower the car too much so that the Lower L-arm goes beyond horizontal into an inward arch the camber curve goes to shit for lack of a better term.

 

During hard cornering if the L-arm is allowed to go into an inward arch (ie. past horizontal) The suspension design begins to increase POSITIVE camber. The tire begins to "fold in" on itself for lack of a better term. This is the case in a vehicle lowered to an extreme.

 

If the L-arm is kept below the horizontal the suspension follows favorable characteristics increasing NEGATIVE camber when leaning into a turn. This allows the tire to bite into the road. This is the case in a moderately lowered car.

 

So it seems that the common philosophy of lowering YOUR CAR = better handling is UNTRUE in some cases.

 

While lowering your CENTER OF GRAVITY = better handling is ALWAYS true.

 

Whereas the term lowering your center of gravity simply refers to your center of mass, lowering your car refers to THE ENTIRE CAR, the suspension geometry, in addition to the center of gravity.

 

It is important to make a distinction between those two.

 

So whats the proper way to lower a car to the extreme while keeping good suspension characteristics? For the mcphearson design it would entail raising the L-arm to subframe connection point so that the fulcrum is well above horizontal. This way you can slam your car and still retain an outward arch to the L-arm.

 

Food for thought... Comments?

You can increase your negative camber to beyond factory specs to deal with the cornering issue and changes in camber during hard cornerning. I have seen this on many super slammed Hondas, etc. The downside is that with the extreme camber, the car looks goofy just going straight because the wheels are angled so much. That also affects your tire wire, since you will wear out the inside of the tire much faster than the outside edge. Not sure ofa proper solution, but I am sur it is out there. I'm sure Keefe has much input and knowledge regarding this matter.

 

-Neil

Extreme negative camber also effects braking as the contact patch is reduced. It wears out tires and generally is a crappy way of going about yor business on a day to day basis.

 

Most Hondas also use an SLA (Short long arm)(dbl wishbone) suspensions that follow an entirely diffrent camber curve than a mcphearson design.

 

You can run extreme negative camber but if your L-arm is beyond horizontal the harder you corner the more POSITIVE camber the suspension is going to add to the static negative camber. This is bad.

 

I rather raise the ride height a little give up an inch or an inch and a half of a lower CG. Set my static camber and have my L-arms work below horizontal and have my suspension INCREASE negative camber when I corner harder.

The problem is not the camber curve. The problem is when you lower the car too much you actually raise the roll center, or the propensity of the car to roll in turns. That fights with the decreased tendency to roll given by the lower center of gravity. You need to find the right ride height where the lower center of gravity give you more roll resistance than the raised roll center takes away.

the problem on Honda's is that the camber is not adjustable as the car sits from the factory. That's why you see ridiculous camber....peeps are too cheap to buy the Ingals or Eibach kits to get it within factory spec or even a 'sport alignment'.

 

From what I have gathered in my short time on this board, 1-1.5" drop is the most you want to do on an LGT and still keep useful suspension travel.

Check out DM's car....I think that is one of the lowest Leggy's;)

Good thread.

 

The other thing an excessive drop will do is increase bump steer. You can feel that to a certain extent with many lowered cars... but generally the lower it is, the worse it becomes. Manufacturers engineer their cars to minimize bump steer from the factory. Assuming they did a good job, that means that when you lower the car, you're changing the static (resting) angle of the tie rods which puts the suspension out of the optimal position for articulation.

 

This is explained pretty well in an old thread at ElantraXD.com...

Ok this is hard to explain but I will do my best.

 

I noticed today that with my car being as low as it is that the tie rods from the steering rack are not straight across anymore like they were when the car was at stock ride height. Instead the tie rods are angled up about 2 inches above level. Now that is no problem when you are going straight but if you throw the car into a corner it will cause some issues that you may not even be aware of.

 

The tie rods from the steering rack follow the wheel. So when the wheel goes up or down as happens when the car leans into a corner the tie rods follow an arc. At stock ride height the tie rod is straight across and thus the wheel points straight ahead. If the tire moves up or down the tie rod in turn makes the wheel toe out.

 

Now with our lowered cars the tie rod is in an upward position in the arc and of course with a new alignment the wheel is straight. Now this is the important part. When the wheel moves up the tie round gets an even more extreme arc and will toe out the wheel. When the wheel moves down the tie rod is returning to a straight across level position and thus making the wheel toe in.

 

So lets add this together. Lowered car enters corner body leans the outside tire goes up into the wheel well and adds toe out, the inside wheel drops out of the wheel well and goes toe in. Do you see a problem? The tires are trying to turn opposite the direction you want the car to corner.

 

So I realized there is an easy fix. The outer tie rod end is mounted to the top side of the steering knuckle. Simple fix would be to just unbolt the tie rod end and mount it to the under side of the steering knuckle. This would make the tie rod straight across again and provide proper steering. Then one of my techs had to wreck it for me by reminding me that the hole the tie rod end fits into is tapered so that the tie rod end will only fit from the top.

 

So I don't know if there is any way to get around this. I am getting a knuckle and a tie rod end to stare at for a few days to see if I can come up with something.

http://www.elantraxd.com/yabbse/index.php?board=7;action=display;threadid=7282;start=msg83886#msg83886

 

If one were to relocate the mounting points of the tie rod ends as he mentioned, you could more or less rectify the problem. Or, just don't lower the car too much and all the little problems that come from the change in static ride height won't be such a big deal.

Check out DM's car....I think that is one of the lowest Leggy's;)

 

Linkage for all you fine peoples

 

http://legacygt.com/forums/showthread.php?t=18886&highlight=drift+monkey