THSCC Forums

This may have been discussed before but I can't find treads. Does anyone know where 4 cornor weight scales are available locally? I know a while back there was some discussuion of the club buying a set and storing them at HH. I am interested in adjusting some coil overs.
Thanks
Mark

I use 4 bathroom scales and levers to reduce the weight each scale "sees" so it can be read. I use a 3:1 set of boards. Pretty easy to do and farily accurate.

Ron

Ron, I have been wanting to try this method myself. Can you go into a little more detail on how you do this? I understand that you need some type of lever system to reduce the effective weight on the scale down to something that it can handle (~300lbs or less).

I have always wondered if there would be side thrust problems that would cause the scale to bind up internally and give incorrect values. Do you use any type of roller system to deal with this? Do you measure all four corners at the same time?

_________________
Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Here is an example of a lever system.

Rollers are available to deal with binding.

http://www.madone.net/html/goods___services.html

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Dick Rasmussen

FS 50 2018 Mustang GT

I currently set my diagnal weights at Krause & England.
The going THSCC rental rate is $75.00
We still have a plan to purchase a set of "club scales" for the Track
Program where Mark Cooper would be the "keeper of the scales"
with access on Sat mornings when the shop is not used.
If finances keep up and Mark is still agreeabe, I will push to implement this at the end of the season given that there is still support to do it. In the mean time I keep paying Peter to use his scales.

_________________
Mark Vitacco
THSCC TT Chairman
mvitacco@bellsouth.net

Ok, here are some follow up questions.

With respect to using Krause & England's scales...

* In practice how does this work? Do you make appointment and do work at their shop? Take scales home for X hours?
* If you do the work at their shop do they have someone to read the scales while you sit in the car or do you need to bring your own helper?

And in general...

* How long does it take you per session to get your corner weights were you need them?
* I assume this is done via adjustments to spring perches on each corner. Does the adjustments cause geometery changes that you need to realign the suspension afterwards? In my case with Honda double A arms all around and with me not having aftermarket adjustable length arms or shims, I am assuming that I can play with corner weights via Ground Control perch adjustments and there is nothing that I can do with respects to the resulting suspension issues (in this case most likely slight camber changes) that results?

As you can tell I am a total newbie on how to go about doing this.

_________________
Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Richard:

I call ahead and "book" making sure the scales are available and
they have space for me to work. the scales don't leave the shop
unless Pete has them in the Transporter to use in the field.
I do the work myself, usually takes me less than a hour. However, the first time it took me about 2 hours.
I take my own floor jack as the shop jacks may be in use and they
are big iron things that are cumberson and I like my alloy H.F. Special.
A helper would be good but David showed me a trick where you use
a broom stick handel to work the keypad while sitting in the car, Don't
laugh it works.
You prep-the car by removing the sway bars-this is very important
and should be done before you get there.
Prep the shop by making a flat patch. I have a long carpenters
level and a 10 ft length of angle iron that I use to level the pads.
I use a stack of 24" square floor tiles to make the "flat patch"
You want the diagnals level with side to side. Pete's storage shop
near the front door is pretty good I usually just 3 tiles on one corner
and the floor may still be marked from the last time I did this.
You can't change the "corner" weights unless you physically move
major components in the car. What you are setting are the diagnal
weights so RR + LR = LF + RR, THis will make the car ballanced the
same in both left and right turns.
You raise the spring purch to increase weight on that end or lower
the spring purch to decrease weight, so the up (more) and down (less)
relationship is easy to remember.
First set the ride height about where you want it keeping mind where
your roll center is and keeping bump steer to 0 or at least to miminum.
Then if you have one diagnal say 300 lbs more than the other, don't
crank in all the justments on one diagnal say turn the high side down
one turn and the low side up one turn instead of 2 turns one side.
When you get down to say less than 50lbs then you can just crank
one wheel.
The end of the car with the most weight will be more sensitive to
changes. So a FWD with 70 to 80 on the nose will have most of
the adjustmens done on the two front wheels because you would
have to crank in a lot of turns to see any difference on the back
and you don't want to reload the rear axle.
A car with 50/50 distribution like a Miata or Corvette will take
equal adjustments front and rear.
Since we don't have a alignment rack with turn plates its time
consuming this is the procedure:
1) take weight measurment and record diagnals
2) jack up on side, remove wheel, make adjustment.
3) replace wheel, set down repeat same for other side.,
4) roll car on/off scales 6 times to settle the suspension
use a wheel stop because you don't want it roll off the ramps
and into somebody's $200K Lambrogani.
The lighter the car the more critical it is to get close to 0%
difference, the heaver the car the less critical getting to 0%
Once the diagnals are equal lock down the purches and the
rest you can do at home.
Make a flat patch and with you seated in the
car connect the say bars so that you can rotate the end link
bushings by hand. Put washers under the sway bar brackets
untill there is no pre-load on the bar-this can usually be done
on just one side. That is also very important.
Then measure the heights as acccurate as possible, i use a
dial caliper on the spring seats and record them. IF you need
to remove a spring you can set it back and still be near perfect
if you measure carefully.
Depending on the quality of springs this can be a once a season
job, twice a season job, or every weekend you race drill.
Having a stiff & stable car with a substantial roll cage, like the Scirocco,
and qood german quality steel springs tends to keep things
stable. I have used springs that never measured the same
twice so you get what you pay for. G.C. uses the good stuff. I would
think doing this at the start of each season would be sufficiant.

IF you run VIR full course a lot you can really tell when the
weights go off because the assendings esses are actually
a 100mph sallom and it becomes very obvious if the car wants
to turn on direction more than the other. If you go to Roebling
you can actually play with some "wege" and get better lap times.

The cost of doing this several times a season does add up. I really believe
a club our size should have a set of community scales considering the
number of people with various coil over setups running street mod
and Street Prep in both the AX and Track programs. With two
cars with coil overs kits I could have paid for half a set with what I
already paid in rentals.

If you want more detail there is a excellent paper on this subject
on LongacreRacing.com's web site, just search on Longacre.
I would be happy to help you if you can make the arrangements.
Feel free to call or email

_________________
Mark Vitacco
THSCC TT Chairman
mvitacco@bellsouth.net

Richard, sorry for not getting back to this earlier. I haven't been following the thread.

The levers I use are pieces of 2x6. One end goes on the bathroom scale( I mark where the end of it is for repeatability.

The other end of the 2x6 is held up with a brick which is very close to the same height as the scale.

I marked off the 2x6 into I recall, quarters. Then put the car on it so that 1/4 (or 1/3 or whatever you choose) is between the wheel and the brick and the rest on the scale.

Before you put the car on the wood, cal the set up. Its pretty easy. Weigh yourself on the scale. Now, weigh yourself standing on the mark where the wheel would be. That will give you the ratio of reading to actual. Pretty simple.

Take your weights on each corner and multiply by the calibration factor and that will give you actual weights at each corner. Whole thing usually takes me a couple hours with adjustments.

Good luck!

Ron

Mark;

See my post I have a set of digial scales!
call me

_________________
Mark Vitacco
THSCC TT Chairman
mvitacco@bellsouth.net

Someone should pull Mark's post above out and put it in the "threads worth saving" area. That is the most understandable description of corner weighting that I've ever seen. Others either skip important bits (like levelling the scales!) or get so complex that it's impossible to understand what's most important.

--Kevin H.

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2003 WRX (again!)