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Discussion Starter #1 (Edited)
So... After successfully adding the MWR Lift Point Kit last week I decided to dive into switching out the OE Blistein dampers for a set of Nitron Singles. The Nitron's arrived (new in the box) with the car. Shinoo at Sector 111 called me to talk through the particulars of these specific Nitron dampers after a single PM! (Thank You). The 450/front, 600/back Single setup seems very reasonable and easy to switch out later.


First the Lotus went back up on the lift (MWR lift points are really nice!)


The Blistein's are removed.


The rear dampers side-by-side.


Next... A Nitron installed on the left rear.


Finally... A wide shot of the Lotus "shedding" the OE shock absorbers and springs.


Next Up... setting Ride Height, Corner Weight, and Alignment.
 

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Discussion Starter #2
Alignment...

So I've been studying up on the topic of ride height, wheel alignment, and corner balancing in these pages and have a plan. I decided to add a set of Atlas (alignment) Wheel Stands to my garage workshop and spent the morning assembling the blue monsters.

The stands are really nice with a 3/8" steel top, heavy duty legs, and adjustable feet. Kind of a PIA to assemble because the holes only barely line up (nothing a couple of pipe clamps couldn't handle). I did a rough height adjustment and slid the stands in under the wheels.



Getting the tops of the stands aligned in the same plane using a small two-axis bubble level and a 78" carpenters level was surprisingly easy. I'll certainly re-check this later but for the moment it looks like the stands will work nice. I plan to borrow a set of race scales from some friends and am thinking through how to provide slip plates under the wheels. Obviously... I'll have to set up some stops to keep the car from sliding off the stands! Has anyone here used the Hub Stands from Flyin' Miata for corner weighting and alignment? Hub stands seem like a really nice way to accomplish these tasks.







 

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You will love the Nitrons, I do! Play with the settings for the best ride. I actually set them a couple clicks harder and it gave me a better street ride. By the way, nice shop!
 

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My slip plates are a pair of .090 aluminum sheets ~15x15 with some grease in between. The slip plates are very important to get good readings
 

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the lift kit & stands are badass
 

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How much does a lift like that go for? I'm looking at 4 post lifts because it seems it would be easier to work around the center of the car.
 

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Discussion Starter #9
Alignment...

So I spent a little time in the garage this afternoon refining the placement and aligning my alignment stands. I set my PLS laser on a tripod shooting right down the center line of the car. Using the laser and bubble levels I think I can get the platforms in the same plane within 1/16" easily. The 2 ton jack stands make lifting one side of the Lotus off the stands a simple operation.



Looking under the car with the laser on shows how easy it is to things lined up pretty close just by "eye". But it also got me thinking about thrust angle and wondering exactly how one goes about measuring it. I know it is usually described as the angle between the drive wheels and a theoretical line down the middle of the chassis. Can anyone here point me towards resources describing thrust angle measurement (I looked around some but have not found much). How, for instance, do you know your strings are lined up to the car (thrust?) properly. I see folks measuring off the ends of their hubs but that's not necessarily aligning them to the chassis. Is the center line of the Lotus chassis marked in some way the vertical laser could be aligned to? Does it matter?



I made a quick stab at ride height using an adjustable square but am going to wait until I have the scales before I get carried away.

 

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By thrust angle I think you talking about rear toe which should be symmetrical about the centerline of the car. I mark the chassis equidistant between pickup points in the both the front and rear. Because the distance between front and rear pickup points is so long compared to the tire diameter, it is not that critical. 1/16" is usually an easy tolerance to achieve. I have a Dunlop toe gauge, so my procedure beyond will be different than yours.

John
 

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You have the disease! God save you!
 

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Discussion Starter #14
Some Thoughts...

So I've been thinking about how to measure (and adjust) ride height, corner balance, and alignment all at the same time. I have a concept I'd like to run by the experts here (be gentle... I'm new).

As seen above my Lotus is up on a set of leveled wheel stands. I'm drawn toward using FM Hub stands for this process because they provide un-fettered access to the adjustable shock absorbers. But it is difficult to directly measure ride height using the stands especially since the car has bigger diameter wheels out back.



my first thought is to fabricate a pair of ride height "bars" with spacers to engage the chassis at the measurement spots under the car. With this sort of gage I could measure ride height directly from a string strung through the center of the wheel hubs (like Carl likes to do). I think this would also allow me to check the "thrust angle" using Carl's method. Kind of like the (incomplete) sketch below.



Taking this one step further I'm thinking that placing the hub stands and race scales on top of the wheel stands provides a "fixture" where all three (four?) elements of this job can be measured and adjusted.



So... before I run off to buy hub stands... does this concept make sense to you guys?
 

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Looks fine -- almost. Rolling radius of a tire is not 1/2 it's free diameter. With car on the ground, properly weighted and air pressures where you want them hot, mark a front and rear tire and the ground contact. Roll the car 5 tire revolutions exactly and measure the linear distance travelled then calculate the rolling radius. Separate calculations for the front and rear, obviously. :D
 

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Discussion Starter #17
Rolling radius of a tire is not 1/2 it's free diameter. With car on the ground, properly weighted and air pressures where you want them hot, mark a front and rear tire and the ground contact. Roll the car 5 tire revolutions exactly and measure the linear distance travelled then calculate the rolling radius.
So the height of the center of the wheel is something less than 1/2 the diameter... like maybe 20-30mm?

I was thinking you might have to "calibrate" a measurement like this. That is measure it conventionally afterwards and save away a "fudge factor" for the next time on the fixture.

I played around for a couple of minutes tonight and think a really long carpenters level (96") and two hockey pucks might make a good starting point for my "ride height bar".
 

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So the height of the center of the wheel is something less than 1/2 the diameter... like maybe 20-30mm?

Much less than that as tire spring rate probably is at least 320N/mm, but you have to measure and calculate rolling radius as I noted earlier. There is some rolling radius info in tire manufacturers' specs (revs/mile) but it is at a specific load, rim width, tire pressure and zero camber so not likely to be representative of our situation.

I was thinking you might have to "calibrate" a measurement like this. That is measure it conventionally afterwards and save away a "fudge factor" for the next time on the fixture.

Yes, although should do it beforehand.

I played around for a couple of minutes tonight and think a really long carpenters level (96") and two hockey pucks might make a good starting point for my "ride height bar".

Yes, but even easier if you can get some aluminum magnets instead. :p
 

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Discussion Starter #19
First... Formulabob It's nice folks like you steering us in the right direction that makes a place like this so worthwhile. Thank You!

So I've been thinking and looking around some more. I found a Tire Radius Calculator on a forum devoted to VW Syncro (micro Bus) owners here. It is a nice Java script that lets you enter tire data and then calculates static and dynamic rolling radius. Obviously it is set up only for their vehicle weights, tire pressure, etc. but is interesting to play around with. I'll drag my Lotus outdoors and measure the rolling radius as soon as spring arrives (assuming it ever does here in Minnesota!) and get the numbers right. In the mean time I think the numbers will look something like this...



I've also played around with a little more detailed diagram of the "fixture" for ride height, corner balance, & alignment. Two Hockey pucks and a 78" carpenters level works surprisingly well as a measuring tool under the chassis. I am able to hold the level and hockey pucks to the ride height registration points using some really soft foam on the lifting points of my scissors lift (I'll take a few photos...).

 

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Discussion Starter #20
Also... The folks at Paco Motorsports (the manufacturer) have updated the FM Hub stands to a new and improved version. They say it is easier to calibrate and it looks to me like switching hub plates will be a lot simpler.

 
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