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on-ramp's Avatar
 
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Ride Height.... how are my calculations?

In attempt to find out if the shop changed my ride height in the front during alignment, I have calculated:

I measured the distance from ground to center of tire = 12.00" . Is this correct? tire pressure 29psi, 16" tires.

For Euro ride height, this is distance "A" , and A - B = 108mm +/- 5 mm, or 4.250" +/- .197"

Last edited by on-ramp; 03-21-2004 at 07:31 PM..
Old 03-21-2004, 04:55 PM
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a picture is better for illustration purposes.

I should be able to place a piece of wood about 7.06" long underneith the 1.38 diameter to achieve the euro spec height, correct?

Old 03-21-2004, 05:40 PM
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ok, now i'm very confused...the 7.06 is not that at all , it's more like 6.37 (center is too low) and the distance from the fender edge to the ground is 26.5", both sides.

What's going on?


Last edited by on-ramp; 03-21-2004 at 07:27 PM..
Old 03-21-2004, 07:14 PM
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Think about it.

It does not matter how much you change the ride height -
ground to center of wheel will not change!!!!!!!!!!!!!!!!!!!!

What will change is the height from ground to wheel arc (fender lip) 26,5" is high.
Remember to have your can cornerbalanced.
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Old 03-21-2004, 08:17 PM
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On-Ramp,

It appears your CALCULATIONS are right on. You are obviously puzzling over the torsion bar appearing low, and the body appearing high. Indeed, that digital image shows a fairly "spacious" front fender. Here a few more items to consider:

(1) The horizontal plane from which you measure the hub center AND the torsion bar center must be perfectly flat and level, just like your diagram.
(2) When these measurements are made, the opposite side front corner likewise must be on that same horizontal plane.
(3) If the car has been jacked up prior to measuring, one should compress and then release the suspension, then measure. (If you still have a spare tire in the trunk, stand on it several times).
(4) This measurement is always taken without any pre-load from stabilizer bars. Detach from A-arms first, then measure.
(5) Lastly, if all else checks out, ask your alignment facility if they removed your front torsion bars from their tubes. If so, you may need to re-index your front torsion bar splines.

Good luck. Let us know what you discover.
Ed LoPresti
RacePro Engineering
New York
Old 03-21-2004, 09:48 PM
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In stead of jumping in your car, I prefer to roll it back and forth a couple of times, it also relieves the stress in your tires.
Allways lower it at both ends at the same time.
If it's high (it looks like it) you need to lower it by reindexing T-bars at both ends and have it realigned. You can adjust some in front by turning the screw.
To check if the rear t-bars are set to the same height you can use your floor jack. Jack it up precisely in the middle in front of your gastank with 2 pieces of wood with a waterpipe inbetween (front/rear dir.) This way your car can roll a little.
Reindex the fronts with the adjustscrew in midway pos. and again check the setting by lifting at the back this time lifting on engine block seam.
This will give a fair chance you can adjust the rest of the cornerweight on the front adjustscrew.
If you DIY don't give up, many times we all need to redo several times to get it right, good luck.
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Old 03-21-2004, 11:33 PM
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The measurement from the ground to the center of the wheel hub will only change if you change tire pressures, weight of the vehicle, or tires and wheels. This measurement will be a constant factor, it will only be affected by wheel/tire changes. Changing the ride heighth, will not alter this. The distance from the ground to the bottom of the fender lip is what will change if adjustments. Not trying to be an A$$, but just letting you know you need to look at a different measurement point.
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Old 03-22-2004, 05:29 AM
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Why re invent the wheel. 3.2 CAB is correct, so is Palle7688
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Old 03-22-2004, 10:43 AM
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Guys don't flame him, I've seen drawings of what he's talking about.
As I recall, they want you to measure/calculate the diff between center of wheel to center of torsion bar=ride height. To me a lot of measurements and calulations for nothing, use the fender lip, unless ofcause your fender is bended.
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Old 03-22-2004, 11:49 AM
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that's the way you achieve a euro ride height, read 101 Projects, pg. 147, "Lowering the 911"

my 108mm is more like 124mm, torsion center too low but the ride height seems too high.


Last edited by on-ramp; 03-22-2004 at 06:56 PM..
Old 03-22-2004, 06:51 PM
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I have an idea!

Instead of that bothersome getting under the car to take measurements (and then subtracting), or that troublesome kneeling down to measure the fender lips, why don't we just measure ride height by the top of the radio antenna?

In that way, we could check it daily, in 3 seconds, and in any kind of weather!

(Hey, Wayne, here is Project # 102, just waiting to be documented.)

Ed LoPresti
Old 03-22-2004, 08:32 PM
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Don't know about those 108 or 124 mm, but if you feel your car should sit lower, lower it!!
The 7,060" is that measured on the front or rear end of the T-bar?
Did you remember to subtract half the dia. 1,380=0,69 (it's for the center)? 7,06-6,37=0,69 GOT YOU!! :-)
Center of wheel measurement is perhaps correct for your can, donno, but the reason for the measurement is that, if you put bigger wheels on the cars ride hieght over tarmac will change, but setting will not.
The reason for carening for settings is that those will affect steering. A lowered car will wander more, be a bit darty, you will have bump steer. The more you lower it, the worse it gets.
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Old 03-23-2004, 07:20 AM
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