PUR NRG

What reference point do you use to determine ride height at all four corners? I'm trying to adjust JIC coilovers and while I can measure the shock itself I have no idea how that really translates into ride height. I've also noticed cars tend to be lower on one side than another. Any help would be appreciated.

As a side note, I am also having difficulty adjusting the height of the rear coilovers. It may be because the top hat is torqued down too much but I can't get any movement using the adjusting rings. Might have to unbolt the bottom end of the shock and unscrew it that way.
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DEPAKOTE HELP

BoxerGT2.5

The biggest thing is to make SURE your on a level surface. Another tip is to make sure you have a full tank of gas. Here is an illustration of varied methods to check ride height.

GeorgeH

iTrader: (2)

When setting up my Miata, I like to get under the car, and measure from the ground to a chassis hard point, like the bottom of a suspension arm at it's inside pivot (i.e., where the aligment eccentrics are). I use a stanley tape measure with a lock - pull the tape out a little, engage the lock, and get under the car. Now, rest the tape measure body on the ground with the tape pointing up, and slowly work the tape out (you can still pull the tape out when the lock is on, it's just stiffer, which is what you need in this situation) until the end of the tape just touches your choosen hard point. Now, do the same thing on the other side of the car and you can tell if your car is level. Get somebody to sit in the driver's seat if you are really ****.

In case you don't already know this, be careful when setting the front to rear rake. (i,e., difference in ride height front to rear). The rear is probably supposed to sit a little higher than the front. If you don't get the rake right it could make the car under or oversteer, depending on how you err. Do the instructions that came with the coilovers give you guidance here? If not you might want to look at what the factory service manual says, or check a stock car and duplicate the rake (but not the actual ride height, of course).

One last thing - when comparing ride heights of different cars, the best way to measure is from the wheel center to the fender lip - this method eliminates the variable of tire height, as well as body panel fit.

GeorgeH

iTrader: (2)

Or you could just get it corner weighted and not worry about if it looks perfectly level.

PUR NRG

Thanks George. The answer is all of the above?

I want to set ride height primarily so I don't have to drive the car on 2x4s in order to jack the car. As it stands I have to use a small 2x4 block on the jack pad so it clears the MS side skirt. That's too much wood. (please, no jokes)

Measuring from the bottom of the side skirt, OEM springs give 5" clearance. JIC preadjusts their coilovers for lower ride height but they go too far for my taste--something like 3" clearance. I am trying to set it at 4 1/4" which should be a good compromise.

JIC's instructions don't even adequately discuss how to adjust shock height (you have to disconnect the rear shock). They talk nothing about rake.

Once I have it set at a good level I'll take it in for corner weighting. And then pray I never have to deal with a flat since I probably won't be able to get a jack underneath if that happens.
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******* strokers

GeorgeH

iTrader: (2)

Yeah, don't get greedy with ride height if you want to drive it on the street.

I know this may be a little unconventional, but I'd reccomend staying away from coner weighting initially, despite my comment above. Get the car where you think you want it (the 4 1/4 you mention above) and then go autocrossing. If the car pushes too much, or is too loose, try balancing the car by changing the rake. Also play on the street and make sure you have enough travel. Once you are happy with the setup (which could easily take most of the season unless you autocross every weekend or are very good at chassis setup) then get it corner weighted as the finishing touch.

So, how does rake affect neutrality? It depends. On the one hand, lowering one end of the car relative to the other *should* make the lower end stick better, since you are lowering the roll center. However, lowering also reduces bump stop clearences, and therefore lowering effectively increases spring rate at full compression. This increase in effective spring rate has the opposite effect of the lowered roll center, and it's tough to predict which effect is stronger - you just have to try it and see.

Going back to my Miata, I found that lowering the rear of the car would make it oversteer more - so, the bump stop effect was stronger than the roll center effect. You'll just have to experiement and see, unless you can find somebody who has already gone through this and duplicate their setup. Even then the wheel/tire package can affect the final results.

Have fun - I've enjoyed my coilovers in my Miata. Learned a bunch about setup, although I'm still no expert.