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Corner Weighting


sdaddy

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Guess who's ready to check some weights :rolleyes:

 

The scales are here.... now just need the car :toetap05:

 

If anyone has suggestions on making some basic corner weight adjustments to a Birkin Series 3 with AVO shocks, please let me know. :bigear:

 

Once the weights are set, next step is confirming / final adjustments to alignment...

DSCN4275.jpg

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How quickly do you have to work before the digital display shuts off?

 

We'll see once the car arrives. I suspect the display is only active for about one min. I plan to capture the weight from each corner, make adjustments, and repeat as needed. Not the fastest, but it will be an almost one-time exercise. All four scales were only $60.

 

PS, The "better half" was a little offended at 400 lb capacity bathroom scales showing up at our front door... :eek:

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Before you start, mark the four tire spots on the floor. Then with a level, and a long straight edge shim under the scales to get every thing level. Don't be surpised if the garage floor is more then 3/8" off in that short span. I used a paint pencil marked the locations and required shim right on the floor.

Dave W

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Mike.

I'd like to compare to my notebook of facts & figures. Do you have the specific recomendations/measurements from BirkinUSA? Also are these for track use; what difference, if any, does road use/blatting about have for alignments?

 

P.

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With regards to these scales, don't you have to lift the car and put it back down each time to get the scales to read ? If that's the case, isn't that a bit tedious ? I wonder if they make the analog type scales for fat people so you can use it on your car. Even if they're off by 5 lbs or so, that should be close enough for corner weighting.

 

I have a shop nearby that does it for about $60 and gives you a computer readout. I like the DIY approach but real scales are about $1200. What do 4 bathroom scales cost anyway ?

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Paul: The Birkin-specific suspension setting is this: distance between the front eye bolts has to be at or v close to 294 mm. And it needs 1/2'-1" rake. After that, it's customer preference.

 

I run abt 1 1/2 neg camber all around (and have the excess outside tire wear to prove it), caster is at max, a bit of front toe out as well helps with turn in tho hurts straight line stability. I dont have the exact specs tho, I put them some where "safe...". My set up is more track oriented as that has been the main use of my Birkin.

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With regards to these scales, don't you have to lift the car and put it back down each time to get the scales to read ? If that's the case, isn't that a bit tedious ? I wonder if they make the analog type scales for fat people so you can use it on your car. Even if they're off by 5 lbs or so, that should be close enough for corner weighting.

 

I have a shop nearby that does it for about $60 and gives you a computer readout. I like the DIY approach but real scales are about $1200. What do 4 bathroom scales cost anyway ?

 

The problem with most of these scales is that they don't like horizontal forces. That means if you lower the front down on the scale the track gets wider and the scales mis-read. The rear axle is less a problem but still need to make sure there is not too much tugging sideways.

 

A few years ago I built a 4 rigs using analog 300 lbs scales and a 2:1 leverage (see image below). It works pretty well and takes care of the side forces although the car needs to be lifted quite high. However I have not been using it much lately. If I really need to re-adjust I just go somewhere to use proper racing scales.

http://home.earthlink.net/~slomove/sitebuildercontent/sitebuilderpictures/cornerscaledetail.jpg

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Thanks for the comments :hurray:

 

While my garage isn't level, I have installed a lift which is. I "engineered" some mounts for the scales so there's no car jacking going on ;-)

 

Hopefully the pictures provide a good idea of what I did. Rolling the car on and off the scale was very easy.

 

With an indicated 3/4 of a tank, the Birkin "as delivered" weighs 1290.6 lbs :eek:

 

Details are:

Driver front: 328.5

Driver rear: 333.1

Passenger front: 300.5

Passenger rear: 328.5 (same as driver front)

DSCN4340.jpg

DSCN4339.jpg

DSCN4338.jpg

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