Corner weighting r300

[Klasik-69]

Not sure if this will benefit anyone but I just got through corner weighting my car and thought I would share the progress and results with the forum. I posted a picture of the spreadsheet I did of the process and hope everyone can read it.

 

First of all, the scales I used are the Proform brand and appear to be quite good but likely not quite as good as a set of Longacre scales. I put the car on my 2 post lift and set the scales down where the tires would ride squarely on the scales. I first made sure the floor was level in every direction, and luckily for me, the guys who did my concrete didn't have too many beers on my job. I didn't have to use any shims.

 

The first set of readings is the car just the way I had it, no adjustments and all sway bars attached. The wheels on the car are 15X7 Enkei with Toyo T1R tires, all set with 20 psi. Gas tank is 90% full and all other liquids are at their required capacity. And the first reading is without a driver in the seat. Total weight came in at 1247 lbs, a bit more than I thought the car was.

 

For the second set of readings, I set all the springs equally on the coilovers, and I sat in the car but without helmet on. The first or leftmost percentage column is the left side vehicle weight divided by the total weight. The next column is the rear weight divided by the total weight. The third column is the right front + the right rear weight divided by the total weight. The fourth column is the left front + right rear weight divided by the total weight.

 

As you can see, these cars are heavy on the left side unless you're a leprichan on helium. There is no way to change that aspect, no matter what you do on the suspension, it remains the same. What is of utmost importance is the "wedge" effect or the cross weights, and more specifically, getting the cross weights to be less than 0.5% from the theoretical perfect 50%.

 

You can also see the marginal but yet important effect of the sway bars connected. They do impact the corner weight cross weight percentages. The front sway bar doesn't have adjustable links (too bad) but the rear does and allows you to fine tune them AFTER you finish corner weighting.

 

I first started to make changes on the left front springs, and as you can see, wasn't able to get the results I needed. I first compressed the spring by 0.125" which made cross weight percentages worse. I then went the other way but started to run out of compression threads on the shock and the effects of this would only lower a car already dangerously close to the ground under the engine pan. So I restored the spring to the orginal starting point and went on the right front spring and compressed it by 0.250" (tightenned the coilover). I also put the hood back on (about 6 lbs) and disconnected both the front and rear sway bars (yep, should have done that to begin with).

 

As you can see, I am now within 0.03% of a perfect 50/50 cross weight differential percentage.

 

You will notice that the total weights vary from session to session, and that is due to rounding off on each wheel. The scale will move back and forth on each wheel weight by 1 lb or so and I set the spreadsheet formulas to total the recorded wheel weight.

 

Having a 2 post lift is a big help in doing this but you still have to settle the suspension after each up and down by rocking the car.

 

 

Comments, critiques and suggestions are more than welcome.

[Klasik-69]

Boy, that's impossible to read. sorry guys, I'll try puting in the actual spreadsheet, not sure if this will work, not too good with this kind of stuff;

 

CORNER WEIGHTING.pdf

 

I hope this is better.

[Kitcat]

Interesting. I look forward to finding out if you notice any meaningful differences on the track. Many of us have comented that our cars seem more balanced with a passenger-looks like it's true. Your car's weight at 1247lbs seems spot on, or even a bit light. My X-flow was abt 1225 w/o gas.

 

Since the Brits put the driver on the opposite side, and since clockwise tracks have a preponderance of right hand turns, maybe this "imbalance" to the driver's side is a competitive advantage there?

Edited August 26, 2013 by Kitcat

[SkinnyG]

I tried corner-balancing mine to 50/50 cross weights, but I kept locking up the RF wheel on braking (quite a spread between front weights). I later corner-balanced it so the FRONT weights were 50/50, and braking seemed better.

 

But I haven't autocrossed it much since then (2008), or done any further testing.

[Klasik-69]

Interesting. I look forward to finding out if you notice any meaningful differences on the track. Many of us have comented that our cars seem more balanced with a passenger-looks like it's true. Your car's weight at 1247lbs seems spot on, or even a bit light. My X-flow was abt 1225 w/o gas.

 

Since the Brits put the driver on the opposite side, and since clockwise tracks have a preponderance of right hand turns, maybe this "imbalance" to the driver's side is a competitive advantage there?

 

Good point, it may be exactly the case. I'm racing at Barber MS Park this coming weekend. That is a clockwise track with more RH turns so I can see if this is working out. I only wish I had previous lap times at that track with this car to compare.

 

I tried corner-balancing mine to 50/50 cross weights, but I kept locking up the RF wheel on braking (quite a spread between front weights). I later corner-balanced it so the FRONT weights were 50/50, and braking seemed better.

 

But I haven't autocrossed it much since then (2008), or done any further testing.

 

You can make the front wheel dynamically light by taking the spring tension down but it is surprising that you did it to such an extent that braking became an issue. I'm still on a learning curve with these cars so nothing surprises me that much. They are very light and as such, may exhibit some characteristics I'm just not familiar with. Most of you guys have been at it for many years whereas this is only my second.

[Dave W]

I had the same problem as Skinny G had with lock up. With the cross car Wts balanced to within 3 lbs, I was having the RF tire lock up. I believe part of the problem has to be the shock damping adjustments, and how quickly you transfer Wt. My Rear shocks, have the damping adjusted relative low [solid axle]. I ended up going with diagonal wts with the RF and LR carrying about 40 lbs more, which solved problem. It was trial and error just added a Qrtr turn to each corner, with RF carrying now with a slightly higher percentage. Dave W

[xcarguy]

Boy, that's impossible to read. sorry guys, I'll try puting in the actual spreadsheet, not sure if this will work, not too good with this kind of stuff;

 

I hope this is better.

 

 

Attachment is much better. Thanks for sharing. I'm corner weighting my Stalker this evening. We'll see how it goes. :smash: :deadhorse: :seeya:

[dallasdude]

You guys have hit of one of the limits of corner weighting.....you want to try and keep front left right balance within 50 pounds or so on a 2500 pound car, probably a lot less on a Caterham. Everything is a compromise, especially with the driver not in the center of the car. I think you give up a little bit of perfect crossweight to get the L/R front balance closer.

[Klasik-69]

After running at Barber this Labor Day, I can say that the car is now very neutral after corner weighting. I don't get the feeling that a left hander is easier or harder to negotiate than a right hander and transitions (hard left to hard right, or vice versa) are much smoother.

 

Having said that, it is possible that my mind is playing tricks on me by making me think that it is now better since I went to all this trouble. You might call it optimistic expectations. I wish I had run the track previously and had lap times to compare but I don't. I am very happy with the car and how it handles. Hardly a scientific evaluation.

[JBH]

One of the biggest benefits I noticed after corner balancing the car was under hard braking. I was flat spotting the right front tire on a regular basis because it had less weight on it and locked before the left front. After corner balance, braking distances were shorter and no more flat spots.

[Croc]

Jeff - Did you corner weight for 1 driver or driver/passenger?

[JBH]

One person - driver @ 175 lbs. I found carrying a second passenger significantly changed the handling and not for the better. I can't believe others think it helps (and it shouldn't if the car is set up correctly for driver only). I really feel the additional weight in the corners.

 

I think I have my car set up in the trailer. As I remember, it was possible to dial in the corner weights to take out a left side weight bias. Each car is different too. What works for one may not be the same for another.

Edited September 11, 2013 by JBH