Corner Balancing MKIV - Street Car

[mcwho]

I am taking my MKIV in for its first front and rear (IRS) alignment next week.

I am gonna set the air pressure at between 22 and 24 lbs of air pressure for 15" tires, and have the front and rear (IRS) alignment done. They will also set the ride height first. I have it roughly set at 4 1/2" front and 5" rear right now.

The guy at the shop asked me if I wanted a four corner weighting. I said no because the car does not have the windscreen on as yet the and the paint and intererior is not finished up.

I don't think the interior will add more than 10 lbs, the Windscreen weighs 30 lbs.

How important is four corner balancing on a street car, and should I have it done now? and maybe rebalanced later?

[wareaglescott]

I am curious about this as well. My thought is what street am I possibly going to be driving this car on beyond 75% of its performance capability so it shouldn't really matter that much for me. Windscreen is almost in the middle of the car front to back and the weight should be evenly distributed left to right so I cant imagine that 30 lbs could have much effect either.
Curious what someone that actually knows what they are talking about thinks though?

[scottiec]

Corner balancing is not necessary on a street car, unless you are noticing some serious handling issues, or one tire locking up much earlier than others on hard braking, etc. If you do get your car corner balanced, not having the car in complete form will affect it, but not to a point that you will notice.

For example, if you have a car on the scales and take out 1 or 2 psi from a tire, you will see your cross weight change right before your eyes. It is very sensitive, and it will never be spot on. One breakfast burrito, and it wont be perfect.

I would recommend setting ride height, getting the alignment, and drive the car for a while. If you decide to get serious at track days, etc, then go for a corner balance.

[rich grsc]

Yes it should be done. Doesn't make a difference if you're on a track or a Sunday drive. If your corner weights are off, you can have understeer in one direction, and oversteer in the other, and it can effect front wheel braking. Not life threatening but annoying. Windshield and paint will not change anything, just get it done now.

[GoDadGo]

I think you just need to level it in order to get it close, which should be okay for a street car.

I have done a basic balance; however, it was with the body off. I cheated the process & through dumb luck and got it pretty close. Here is how I did it, but you need to know that my car is easy compared to the I.R.S. since it has the 3-link rear:

1. I set the ride height @ 4.5" and made sure the coil overs were set evenly from left to right.
2. Next, I raised the front from the exact center of the cross member using a 2x2 block on the jack.
3. I lifted the front off of the ground, pulled the front wheels and lowered the car back to ride height.
4. The car sat level on the rear tires with the front sitting on the jack which was dead center on the cross member.
5. I put the tires on the front and sat the car on its wheels.
6. After that, I reversed the process jacking the car from the differential using my spreader bar set evenly in the middle.
7. The front was a little off so I had to take about 1/2 turn off of the left front to get it level.
8. After that, we scaled the car and to our surprise it was right around 50/50 front to rear and 50/50 left to right as well.
9. I was really concerned how things would work out because of all my changes, but trying to simply level the car seemed to do the trick.

Note: While I have upset the Factory Five weight distributions because I moved things around, I think it should handle well enough for a peppy cruiser.

https://youtu.be/_wnHDNgnNqs

PS-Add-On:
I rode in and drove two FFR's before ordering my kit and those cars were amazing.
The first was a donor MK-3 build with the IRS while the second was a complete MK-4 kit with a three link.
The I.R.S. rode better, but the 3-link hooked better so I went with the 3-link.

[RoadRacer]

I'd say yes. I've corner balanced my cars if only to detect and fix any large errors. It's more important IMO than only leveling and hoping the weights then match. I balance with my weight in 45lb weights in driving seat so you expect the shocks to be not level after.. ;)

[GoDadGo]

I'd say yes. I've corner balanced my cars if only to detect and fix any large errors. It's more important IMO than only leveling and hoping the weights then match. I balance with my weight in 45lb weights in driving seat so you expect the shocks to be not level after.. ;)

Road Racer,

When we stuck it on the scales system each wheel was within 11-15 pounds of each other from left to right and from front to back as well.
Basically, each wheel is carrying 24%-26% of the total weight of the car so does it need to be closer than that?

Steve

[RoadRacer]

I'd say that's great, assuming drivers weight in the car

[2bking]

Yes it should be done. Doesn't make a difference if you're on a track or a Sunday drive. If your corner weights are off, you can have understeer in one direction, and oversteer in the other, and it can effect front wheel braking. Not life threatening but annoying. Windshield and paint will not change anything, just get it done now.
While rich grsc has a point here, I'll throw in my experience. I spent several days weighing mine to find the exact weight on each wheel just to know front to rear and side to side weights. I then very carefully set the ride height on a flat level floor. The frame is stiff so a little difference in ride height from side to side will change the wheel weighting but when I had the ride height the same on opposites sides, the resulting weight on the wheels was very close to the premeasured weights. My take away from all the measuring was that I wasted a lot of time weighing. I could have just carefully set the ride height and moved on to doing something else. I agree with GoDadGo, "you just need to level it in order to get it close, which should be okay for a street car."

So now my car is very well balanced for a flat street but not too many of the places I stop and turn are flat like the shop floor. I haven't notice any consistent over/under steer but then I don't drive on the edge of its available performance.

[i.e.427]

Yes it should be done. Doesn't make a difference if you're on a track or a Sunday drive. If your corner weights are off, you can have understeer in one direction, and oversteer in the other, and it can effect front wheel braking. Not life threatening but annoying. Windshield and paint will not change anything, just get it done now.

This, what Rich said. And I'm going to add to it for those of you that use the "it's just a street car" excuse. In a production street car the frame/chassis is very flexible. Those cars use non-adjustable struts/springs and/or shocks and springs. Because the chassis is flexible the car's weight is very close to equal on each corner/corner cross weights. Now let's look at a race car chassis used for a street car. The frame is extremely stiff, to the point that one corner being 10-15 lbs. lighter than another will easily cause wheel lock up under braking and/or uncontrollable wheel spin under acceleration. We read a thread just this week about lateral grip of tires, ring a bell? Factory Five vehicles all use adjustable coil-overs for a reason and it's not just to set ride height. Every vehicle we build or service gets corner-weighted. It has been our experience that this makes it much easier to baseline the suspension setup. Those of us that drive our cars the way they were intended want the car to be as predictable as possible.

[scottiec]

This, what Rich said. And I'm going to add to it for those of you that use the "it's just a street car" excuse. In a production street car the frame/chassis is very flexible. Those cars use non-adjustable struts/springs and/or shocks and springs. Because the chassis is flexible the car's weight is very close to equal on each corner/corner cross weights. Now let's look at a race car chassis used for a street car. The frame is extremely stiff, to the point that one corner being 10-15 lbs. lighter than another will easily cause wheel lock up under braking and/or uncontrollable wheel spin under acceleration. We read a thread just this week about lateral grip of tires, ring a bell? Factory Five vehicles all use adjustable coil-overs for a reason and it's not just to set ride height. Every vehicle we build or service gets corner-weighted. It has been our experience that this makes it much easier to baseline the suspension setup. Those of us that drive our cars the way they were intended want the car to be as predictable as possible.

So do you corner balance the cars you build with the drivers weight? When that driver decides to do track days, he is going to have an instructor next to him which will change the weights. Being a "street car" isn't an excuse. If you are noticing a 10 or 15 lbs difference, you better be driving on the track. It will not cause wild and crazy unpredictable oversteer or understeer. For the six years I raced spec miata quite competitively, we would only corner balance to get close. We make a lot of adjustments after that to get the car to handle how we want.

I don't think there is anything wrong with a base line. However, I don't think people have to shell out $300 (what the cost is by me) to get a corner balance done unless they start to get serious about driving 10/10ths. Set the ride height, align it, then go from there.

[smithbks]

I have the same question as scottiec. DO you adjust for the driver? Further, should you adjust ride height with driver weight? Isn't that the only way to get it truly right? Everything else seems to me that we're dealing with "pretty close" anyway. Help me with this guys because what should be a simple concept is confusing me now.

[NAZ]

While it may be interesting to play with corner weights unless you have a specific goal what do you hope to achieve? Set the static ride height and have it aligned. While weight bias will affect handling and traction the static alignment is not affected by how much weight is jacked into any particular tire (notice I said "static"). That's your baseline. From there you can adjust corner weights, tire pressures, spring & shock rates, anti-squat, roll centers, and alignment specs to maximize performance for a particular load, a change in CG, and for the track conditions. A street car sees far more variables affecting all these settings than a track car. The difference between one occupant and two is significant -- are you going to put the car on scales and adjust corner weights every time you want to give someone a ride? Good luck keeping up with changing conditions on a street car and unless you have wheel scales & alignment tools to do this yourself you're still just setting the car up for a happy medium regardless of use on the street or track. Don't over think this.

[Bob Cowan]

Yes, corner weights matter on a street car. Just not as much as on a track car. On a track car, you want to work at getting it very precise. You'll even move components around on the car to get it where you want it. On a street car, you won't go to those lengths.

A well balanced car will do exactly what you tell it to, when you tell it to. It's a true joy to drive.

Set up the car the way you would normally drive it. If you and your wife would normally be in the car, put your weight and her weight in the seats. Put whatever weight would normally be in the trunk. And have about 2/3 of a tank of fuel.

[GoDadGo]

Hey Gang,

I just told my better half that she should gain some weight so that the car will be balanced when we start cruising around in our Cobra.
My weight bias is all on the right side of the car (About 25 Lbs. Total) so she should gain 25 Lbs. so we will be perfect from a corner weight perspective.
My point is unless you are John George, Karen Salvaggio or one of the other F.F.R. race car crew, you just need to set, get it close and forget it.

Steve

[Straversi]

Hey Gang,

I just told my better half that she should gain some weight so that the car will be balanced when we start cruising around in our Cobra.
My weight bias is all on the right side of the car (About 25 Lbs. Total) so she should gain 25 Lbs. so we will be perfect from a corner weight perspective.
My point is unless you are John George, Karen Salvaggio or one of the other F.F.R. race car crew, you just need to set, get it close and forget it.

Steve

My wife is going to love this car when I ask her to step on the scale every time we go out for a cruise.

[myjones]

Hey Gang,

I just told my better half that she should gain some weight so that the car will be balanced when we start cruising around in our Cobra.
My weight bias is all on the right side of the car (About 25 Lbs. Total) so she should gain 25 Lbs. so we will be perfect from a corner weight perspective.
Steve

My "better half" would have pointed out that if I lost 25 Lbs. it would give the same result. Just saying :)
DB