Corner balancing

[Elapid]

I have a Mk3 which I use for street as well as several track days per year. I built it with new Cobra brakes and a CNC master cylinder. It has always had a problem with the left front wheel locking before the right. Adjusting bias does not fix this unless I set it for the rears to lock up first which is bad. I've tried different pads, deglazing the rotors etc. I recently read an article in a Porsche magazine telling how someone with this problem in a Porsche had fixed it by corner balancing the car, that corner was too light. A lot of the racing shops around Indianapolis here have gone under in the past few years and I can't find anyone with scales. Is this something I should try myself? I know scales can be rented somewhere, I'm thinking JEGS or someone rents them? I'm sure corner balancing would improve handling on the track as well as braking. What experience have others had doing this themselves? If I have someone align the front suspension should that be done before or after corner balancing?
Thanks

[JKleiner]

Originally Posted by Elapid

A lot of the racing shops around Indianapolis here have gone under in the past few years and I can't find anyone with scales.

Performance Driven on the southwest side (near 465 and 67) can corner weight the car. (317)821-1548

Jeff

[Bob Cowan]

Corner balancing can be surprisingly helpfull, even for a street car. I prefer to do these things myself. It usually takes me a lot longer, because of the learning curve. But that allows me to adjust things just the way (I think) I want them. and if I make changes later, I can do it again.

I use Ruggles scales. I bought them used for a good price. But you can find them new for a whole less money than electronic racing scales. For the average garage mechanic who might do it once a year - maybe - they're worth it.

The trick is, though, the surface you're working on must be flat. If the floor is irregular, it's almost impossible. If the floor has an angl;e to it, you can often shim it up to be level at each corner.

But, try this first, it's free and doesn't take long. RFaise the front end on jack stands that are pretty level. Set the spring collers so they just contact the tops of the springs. Do the same in the rear.

With the car flat and the suspension settled, measure ride height at each corner. Adjust the front by making the exact same adjustment to each side. Do the same in the rear.

Now, you might find that ride height varies a little bit from side to side. But, that brings your corner weights really close to 50%. Mine was 51.5% after doing this. Then I used the scales to get it perfect. If that changes your tire lock up problem, then you need to get on the scales. If not, it's a differant issue.

[Elapid]

Many thanks to you both. I never knew Performance Driven existed down on the SW side, I'm on the NW. I'll definitely have to check them out, see what services they offer. I do enjoy the challenge of doing things myself so I may give it a try, I'm sure I'd learn a lot.

[TBSTANGS]

Build your own I have the plans somewhere. I got them out of a How to book about Fox body Mustangs. You us four bathroom scale and a leverage device you build by welding together angle or square tube steal. You set the car on the pads read the scales do a little math and BINGO you can start corner tuning your car. I'm good at math and VERY CHEAP so this was PERFECT for me. PM or email me if you would like the plans to build one. I would think Griggs or Maximum Motorsports may have the plans on their web site, but I can send them to you. HTH

Tony
ptb007@hotmail.com

[GWL]

Bob,

I always read what you have to say. Thanks for taking the time to post that explanation, it is now in my files for when I get to that point.

Tony,

I just did a quick search. Consumer Report says the average digital scale measures 350 lbs. There was one listed as 'Best' for $40 that measured to 380 lbs. That only gets you up to a total of 1520 lbs. Then you have to be concerned about accuracy. I've always understood that scales, torque wrenches, air gauges and other such measuring devices are more accurate in the middle of their range not at the extreme end as you would have to be doing when you used a bath scale that was able to measure up to what you needed. Why would any bathroom scale be made to measure 500 lbs. or more? We would need at least that much and more as explained above.

I really like the idea of making your own equipment and doing it yourself but I would question its accuracy here.

Bob,

How accurate do you try to get when measuring corner weights? What are your corner weights?

George

[TBSTANGS]

That is where the math comes in. Regular bathroom scales work. The car sets on a plate and frame, the scales set under the other end of the frame and it reads X lbs. There is an algebra formula in the plans and you take measurement A X B divide by the weight etc. I don't have the exact formula in my head but I do have it in the box with my scales and frames. I see you have emailed me, I'll find my file and send you the info. A friend tried it on his late-model race car against his car scales and said it was very close, I don't remember the numbers but was less than 5% difference?

Tony

[Doug Meldrum]

If you're coming through Salt Lake, I have a set.
D

[Bob Cowan]

Originally Posted by GWL

Bob,

I always read what you have to say. Thanks for taking the time to post that explanation, it is now in my files for when I get to that point.

Tony,

I just did a quick search. Consumer Report says the average digital scale measures 350 lbs.

I really like the idea of making your own equipment and doing it yourself but I would question its accuracy here.

Bob,

How accurate do you try to get when measuring corner weights? What are your corner weights?

George

You don't really need a scale any bigger than that. Mine only go to 220#.

Making them yourself would not be that difficult. Now that I see them, I could probably make them without too much difficulty. The trick is to be extremly accurate in measurements and welding.

The corenrs weights are very accurate. I'v checked them by adding a known weight and I get the same reading on each scale.

LF- 632...........RF- 632
LR- 748...........RR- 732

Left side 50.3%, Rear bias- 53.9% cross weight- 50.3%

Originally Posted by TBSTANGS

That is where the math comes in. Regular bathroom scales work. The car sets on a plate and frame, the scales set under the other end of the frame and it reads X lbs.
Tony

Yes, they do work, and doesn't require any fancy math.

[ezglider]

I am new to this and interested in this topic. My RF will lock up first so maybe this method helps. i had adjusted ride height only with no idea what each corner weight is. My question is do you need 4 scales, or can you do it one at a time assuming you had pads that the other 3 tires sat on that were equall height to the scale. I would assume that you need to jack up the car to unweight the springs to adjust them anyhow so you can move the scale where you want. Maybe the constant jacking is not worth the hassle. Not worried about the cost of 4 bathroom scales , just thinking of the storage issues with 4 scales, and the assorted beam ballances that are fabricated.

On another related topic is there a guide that tells you Start Here for chassis setup? For example

Corner balance, then ride height, then align, etc

From there is there a guide that tells you Increase front tire pressure does X, Stiffening front sway bar does Y, and if the car has understeer do these five things in a specific order?

Basically a suspensions for unenlightened.

Thanks in advance

Jeff

[CraigS]

This is great info and very timely for me. I have a leverage type corner weight checker.It hooks into the wheel and you lift the wheel til it just clears the floor. haven't used it for a year. Went to do it a couple weeks ago and realized that my new Bullit front wheels don't have a surface these can grab.The old Cobra Rs were fine. Damn. So i will need to build some levers for bathroom scales.Elapid-you can backyard your way into a fix if you want.After following advice above to adjust your coilovers so they are the same left and right by measurement,see if that helps. If not, make a mark on that LF coilover adjuster ring so you ahve a reference you can return to.Now start cranking more ride height (corner weight) into that corner one turn of the adjuster at a time.Try this for maybe a total of 4 turns to see if you can fix the wheel lockup problem.Good luck

[Bob Cowan]

Originally Posted by ezglider

I am new to this and interested in this topic. My RF will lock up first so maybe this method helps. i had adjusted ride height only with no idea what each corner weight is. My question is do you need 4 scales, or can you do it one at a time assuming you had pads that the other 3 tires sat on that were equall height to the scale. I would assume that you need to jack up the car to unweight the springs to adjust them anyhow so you can move the scale where you want. Maybe the constant jacking is not worth the hassle. Not worried about the cost of 4 bathroom scales , just thinking of the storage issues with 4 scales, and the assorted beam ballances that are fabricated.

On another related topic is there a guide that tells you Start Here for chassis setup? For example

Corner balance, then ride height, then align, etc

From there is there a guide that tells you Increase front tire pressure does X, Stiffening front sway bar does Y, and if the car has understeer do these five things in a specific order?

Basically a suspensions for unenlightened.

Thanks in advance

Jeff

You could do it with only one scale. What a hassle that would be. Make an adjustment, weigh each corner. Make an adjustment weigh each corner. Lather. Rinse. Repeat. You'de be at it all day.

Storage really isn't that much. The parts stack together pretty well, and don't take up much room at all.

Chassis set up needs to be done in a fairly specific order. Ride height, corner weight, caster, camber, toe, bump, ackerman, etc. If you get them out of order, you get screwey results, and waste a lot of time.

There's a number of books available for chassis set up. Most of them are specific to a race car, and so might not be real helpfull. I find Carroll Smith's books to be really helpfull. His books are definatly aimed at race cars, especially the Ford 2000 spec cars. But he explains it well enough that you can apply it to any car. I'v learned a lot reading them.

You can start by setting the ride height properly. Start by unloading the suspension front and rear. Turn the collers so they just contact the top of the spring, but doesn't load the spring. Lower the car to the ground, and roll it back and forth a few times to settle the suspension. Adjust ride height by adjusting each side exactly the same. First do the front, then the rear. Then go back and do the front again. This method gets the corner weights pretty close. My car was only off by about 5% or so.

[GWL]

Bob,

I've been thinking about these scales.

How do you get the wheels to sit exactly on the same spot each time? I'm thinking about the distance from the center of the tire to the scale. What if you are off by, let's say, a quarter inch?

Pegasus used to sell the Ruggles scales but don't anymore. I found one on a Porsche site for sale. Spruce Aircraft sells a set of three for airplanes but there does not seem to be any dealer that sells them in a set of 4 anymore.

Thanks, George

[Bob Cowan]

Originally Posted by GWL

Bob,

I've been thinking about these scales.

What if you are off by, let's say, a quarter inch?

Pegasus used to sell the Ruggles scales but don't anymore. I found one on a Porsche site for sale.

Thanks, George

Won't matter if it's off a little. The cross bar is a welded in piece of angle iron, with the flat part at the bottom, like an "L". The bottom of the wheel plate also has a piece of angle iron welded to it. But it's welded with the point up, like an upside down "V".

By matching the upside down V to the L, the measuring point remains the same every time. Obviously, you want to get it centered under the tire. But if you're off by a 1/4", it won't really matter.

I bought mine used from some one on this site (I think). Saved me a bucket load of money. Pegasus still lists them on their site, I guess yhey havn't updated their catalog.

If Spruce still lists them, I would call them and ask for four. Or buy three. Once you see them, you can make a fourth one without too much trouble.

Maybe I should start making them for sale? Or are they patented?

[bstuke]

Originally Posted by Elapid

It has always had a problem with the left front wheel locking before the right.

I am going to go out on a limb and suggest there is something else wrong. I have Cobra brakes on the front and a Whitbys vacuum assisted brake setup. I rarely drive mine on the street and have never had one front wheel lockup before the other. They lock up at the same time.

I have not corner weighted my car.

[Doug Meldrum]

I just weighed my car and need opinions. The ride height looks pretty good but the corner weight probably needs some minor adjustment. The scale I used is made specifically for weighing vehicles (trucks for the highway patrol) and are spot on. Do these numbers look good?

LF 520# RF 520#
LR 610# RR 590#

[stephenwagoner]

Mark Donahue in his book "The Unfair Advantage" tells us buying 8 bathroom scales, and using 2 scales per corner, with a board on top to distribute the weight equally between the pair of scales. Then he made 4 wooden ramps (one per wheel) to drive the race car up on the scales. Simple. Best of luck. -- steve

[ffspecracer]

Doug,

Not bad. Really depends on how accurate you want to be. Your numbers show a cross corner of 50.45% and 49.55%. As a racer, I get mine dead on 50/50.

[Wade Chamberlain]

Originally Posted by Doug Meldrum

I just weighed my car and need opinions. The ride height looks pretty good but the corner weight probably needs some minor adjustment. The scale I used is made specifically for weighing vehicles (trucks for the highway patrol) and are spot on. Do these numbers look good?

LF 520# RF 520#
LR 610# RR 590#

Ideally, you'd weigh the car with you in it, and try to get your cross-weights equal. (LF+RR = RF+LR)

[ffspecracer]

Wade, Good catch!

I wasn't paying attention. Those corner weights do appear to be without driver.

[Tom Veale]

Hi Brian,

For the track I always weigh the car with me in the driver's seat. That's how it will be on the track.

When I did the Pumpkin Racer, I had no scales. First I got the car at about the ride height I wanted at all four corners. I put some adhesive tape down on the garage floor for the tires so I would be able to measure everything in essentially the same spot after adjustments.

Next I drove it over to the County buildings where they have a freebie scale (where the trucks get weighed when making deliveries) and drove the Pumpkin on and off various ways. Front axle, Rear axle, Front Right, Front Left. Rear Right Rear Left. Left Side, Right Side and total car weight.

The county scales are only +or- 10 pounds, but even so, that helped a lot when I found out I was nearly 80 pounds off on cross weights!

I drove it back to the garage, parked on my tape markers and jacked up the Right Rear first and put in one full turn. I did the same at the Left Front. Then it was back to the county building and on their scales (outside, open all day and night, no attendee). Second weights showed I'd overshot by about 20 pounds. So, back to the garage.

This time I measured ride height again and then backed off the Right Rear about 1/4 turn (it was just barely higher than the Left Rear while the fronts seemed exactly the same). Then back to the county one last time. It was as good as the scales would allow me to be. I figure I was within 0 to 15 pounds on the cross weights.

The difference was Big on the track. Afterward the car behaved pretty much the same going through lefts and rights. Before doing this it had been non symetrical in handling. The next year I changed spring rates at the rear of the car and went through the same procedure before heading to the track. The new springs did just what I wanted (remove some front "push") and again the car was essentially symetrical in handling lefts and rights.

When I finished up the FFR '33 Street Rod I did the same thing. The chassis might be a bit more 'square' than the FFR Challenge car was as I didn't need to make much in the way of adjustments to the springs based upon symetrical ride height. Maybe 1/2 turn on one rear coil was all. It's a sweetheart on the track, too.

As a benefit, I met a couple of guys who work for the county who build and restore cars. I got invited to a hot rod breakfast that happens once a month that I knew nothing about!

So, that's about as cheap and dirty as one can get! This would be more than adequate for most street cars. If you aren't going to the track, you could set the cross weights without a driver and then it would be pretty close when taking a passenger for a ride.

Best regards,

PS: Are you coming to Road America in a few weeks?

[Don Payne]

Originally Posted by Doug Meldrum

I just weighed my car and need opinions. The ride height looks pretty good but the corner weight probably needs some minor adjustment. The scale I used is made specifically for weighing vehicles (trucks for the highway patrol) and are spot on. Do these numbers look good?

LF 520# RF 520#
LR 610# RR 590#

A bigger engine up front will help!