chaoscreature

I was trying to get a set of loaner corner scales to check my car on after installing coilovers, but didn't have any luck finding some. Inspired by some "ghetto scales" I saw on the internet I decided to make my own. What I did differently on mine was I mounted the scales to the hub so that all of the suspension would be accessible. This way I could make height or weight changes without having to swap tires on/off.
Although I don't have a digital level these would also make camber and toe adjustments a snap. The hub mounting plate is hinged relative to the platform and the entire assembly is on rollers allowing the suspension to "settle itself."
They have a 7.25:1 ratio. I know they aren't accurate down to the nearest pound, but I think they are within about +/- 15 lbs per wheel. Accurate enough for my uses.
According to these my car weighs in at 3240 pounds with 1/3 tank of gas. With me in it I got the following readings:
RF: 645
LF: 696
RR: 1030
LR: 1030
I will dial out the 50 lb discrepancy in the front tomorrow.
Once I am done playing with these they will be up fro grabs to Rennlist and PCA members who want to borrow them. I built them a little "overkill" since I was using cheap materials... they weigh in about 35 pounds EACH but they are absolutely bullet proof.

One interesting note on the JIC's. I was surprised to see the tender springs completely flattened front and rear. It seems like they act as a large spacer more than anything. Is this typical of a main/tender spring setup?

race911

Just make sure you're level. Like perfectly level.

And most of your front imbalance is basically the battery being in the left front. You're never going to get a non-center drive (e.g. formula car) balanced across the car, let alone a street car. You've got adjustable drop links that you can dial out preload? Else, the stabilizer bars are going to weight jack across the chassis.

Toe will be a bitch without at least the diameter of the wheel to measure against. K-Toe should be a snap! (See my thread on the funky worn tires I just pulled off the yellow car, and what will be my fun checking the alignment in the next few days.)

AOW162435

Very cool!


Andreas

trophy

I like that, would love to borrow them, but shipping them across the border would cost more than making a set myself. Would love to see a bunch of close up pics or some diagrams if you are willing to share

Regarding the tender spring, it is really there to stop the spring moving around when it is in full extension, it maintains pressure on the spring so it doesn't move around.

968gene

very interesting idea. can you share additional pictures?

Stealth 993

Looks great! The tender springs are suppose to keep the main spring in the perch, under droop. You can also put in a much higher spring rate spring, but lower then the main, to give you a bit of progressive rate feel. It will help on small bumps. Of course you would need to reballance.

When you did this, did you have 1/2 tank of gas, & your body weight in the drivers seat?

chaoscreature

For the toe measurement I was going to pull the hub mounting plates back off, drill and tap them and screw a 30" long piece of aluminum angle to the hub. Two tape measures could then be draped across for measurement.
The purpose of me doing this was about 95% curiosity. I couldn't afford to have the car professionally corner balanced ($200 was the starting point at my shop) and just wanted to make sure the car wasn't too "jacked".
My garage floor isn't perfectly level, but it has less than 1 degree of slope. This amount of error is negligible considering the 3% error on each of the scales .

Stealth993,
That's exactly what I was thinking this morning. Without the lighter spring the main spring is so stiff that under rebound or if the tire hits a chuckhole the suspension would have very little travel or "droop". The soft tender springs extend the range of the suspension travel while keeping the car stiff under smoother conditions.

geolab

I am sorry to think that your corner balancing to my understanding is perfect on the car.
Something is not right in the front weighing measurements
in other words, if RL and RR are equal, FL and FR must be equal
When I do my corner weighing, If my rear right wheel is equal to my rear left wheel, I usually stop touching anything
please, correct me if I am wrong...

race911

Here's pretty much it's as good as it's going to get. On a LHD car, anyway.

https://rennlist.com/forums/showthre...ferrerid=21505

Thing I pointed out, that everyone pretty much ignores, is how much preload the stabilizer bars put on the suspension. If you don't account for that, it's all guesswork. (I get that the car here in question is not a hard-core track rat, so you do what you can for a street car and just accept things.)

cgfen

Peter
Bravo!

I'm just completing my AWD reinstall.
Would love to utilize your scales sometime soon.

cheers

Craig

johnsjmc

I thought you were supposed to aim for equal crossweights?

Garth S

Absolutely true!! In this link there is a shot of my car being corner balanced ... at least an approximation to the theoretical: there is a double layer of 3/4" MDF board forming a work base under the 4 load cells supporting the car. The MDF was carefully shimmed to be 'dead' level.

Once the car was adjusted, we slipped a 1/4" shim under one wheel .... and moved the diagonals by 30 lbs .... this is called 'wedge' for the circle track guys - but shows how sensitive the corner balancing exercise is to anything less than a true level working surface.

chaoscreature - great DIY jigs !!!!

chaoscreature

Race911,
By stabilizer bar are you referring to the sway bars? I unbolted them from the car when I did the suspension install. With the car sitting level there was no pre-load on the sways, they unbolted and didn't move.

if RL and RR are equal, FL and FR must be equal
This would be true if the entire car was perfectly symmtrical. I think the rule of thumb is that the sum of the corners will always be the same. Meaning you can't change the center of mass of the car through suspension changes, but you CAN dramatically change which tires are loaded more diagonally.

For example on my car:
RF + LF = 1341
RR + LR = 2060
RR + RF = 1675
LR + LF = 1726

The weight bias of the car with me sitting in it is approximately 40% front, 60% rear. The Left-Right bias is 51% drivers (Left) side, 49% Passenger (Right) Side. Not bad at all!
So come to think of it, last night I wrote that I would dial out the 50 lbs in the front... I think the best I can do is to split the difference (which will adversely effect the rear) and end up with something like this:

RF = 681
LF = 660
LR = 1045
RR = 1015

The better thing to do would be to move the battery to the passenger side of the trunk and leaving my suspension alone. That would help a bit and won't screw up my alignment settings.

bavarian06

sorry to crap your thread but i have a question about the tender springs. does it go on top or the bottom of the main spring? or does it vary by coilover application. i noticed yours were on top. a bit conflicted

bavarian06

my tenders are nearly collapsed with the full weight of the car as well, which is normal. suppose to go flat on the first sign of compression.