DIY corner balance (easy)
08-27-2003, 07:25 PM
#1
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DIY corner balance (easy)
For 1992 C2:
4 new Bilsteins ~$600
4 new Michelins ~$900
4-wheel alignment $140
Total: ~$1640
My accountant (spouse) called a halt to the cash flow - something about sending the children to college and staying out of the poor house ....
I still wanted a good corner balance to optimize handling. What to do? It took some time, but I think I nailed the corner balance for a cost of less than $10, and no particular expertise required (an easy DIY project).
First I needed the tool for turning the spring perches. A pipe wrench works, but chews up the aluminum perches pretty badly (previous experience). I had some 1/4" x 3" steel flat bar. I transfered the shape from of one of the old perches using spray paint, and cut the profile with a jig saw. Used a file for the fine finishing, and it worked perfectly. If you can find one to buy, that is much easier.
I got the four corners within the factory tolerance for height. The allowance is +/- 5 mm at each corner, and each side should be within 5 mm of the other. No problems so far. The factory manual states that ride height is SECONDARY to corner balance in setting up the suspension. The corner weights should be within 20 kg side-to side, and you adjust the heights within the factory tolerances to get the balance correct. How do you weigh the car? I can't, and the shop I trust does not do corner balance even if I could sneak out the extra funds. Threre is an easy way:
The only other tool needed is an 8-ft long air hose and valve fittings to connect the Schrader valves on the two front tires together. I bought "valve extenders" at the car parts store. Truck stops also sell these for extending short valves on wheels with valve access problems. I cut the "extender" in half, and fitted an air hose between the fittings that thread onto the Schrader valve.
Put all tires at spec pressure, and fill the fuel tank (factory requirement). On the flattest concrete you can find, measure the distance from the concrete to the wheel rim (a set of pointed dividers makes this easy). There was less than 0.5 mm difference side to side - within the measurement error. I then connected the hose between the valves on the front tires, and lowered the pressure to 20 psi. This put the rims about 3 cm (1 1/2 inch) closer to the ground. The front tires exchange air through the hose, so the heavy side goes down, and the other side goes up as the air moves to equalize the pressure between the two sides. You will hear the air hissing until a new balance is reached.
I should have placed a 20 kg mass on a pillow on one front fender to see how sensitive the system is. I could press on one fender, and hear air hissing as it moved from the side I was pressing to the lighter side. I concluded that this was more that adequate to detect a 20 kg imbalance.
The observed difference side-to side was now 3 mm, showing that the balance was close, but not perfect. A small change (about 3 mm) on one of the higher corners balanced the front tires. After inflating the fronts back to 36 psi, the ride height was still well within the factory specifications.
Note that it is not necessary to repeat this on the rear. The car can be balanced by adjusting only one corner. The wheel on the opposite end and opposite side responds to change at any corner. If any two wheels are weight balanced, the other two will be as well (simple Physics).
The 4-wheel alignment was done after setting the balance. Ride and handling are excellent, much better that when I bought the car.
This was about a 1 1/2 hour job, plus the time to get and build the special tools (another couple of hours). Anyone care to try it? Let me know if you need the height settings and measurement locations. I will need to look them up again.
Cheers
4 new Bilsteins ~$600
4 new Michelins ~$900
4-wheel alignment $140
Total: ~$1640
My accountant (spouse) called a halt to the cash flow - something about sending the children to college and staying out of the poor house ....
I still wanted a good corner balance to optimize handling. What to do? It took some time, but I think I nailed the corner balance for a cost of less than $10, and no particular expertise required (an easy DIY project).
First I needed the tool for turning the spring perches. A pipe wrench works, but chews up the aluminum perches pretty badly (previous experience). I had some 1/4" x 3" steel flat bar. I transfered the shape from of one of the old perches using spray paint, and cut the profile with a jig saw. Used a file for the fine finishing, and it worked perfectly. If you can find one to buy, that is much easier.
I got the four corners within the factory tolerance for height. The allowance is +/- 5 mm at each corner, and each side should be within 5 mm of the other. No problems so far. The factory manual states that ride height is SECONDARY to corner balance in setting up the suspension. The corner weights should be within 20 kg side-to side, and you adjust the heights within the factory tolerances to get the balance correct. How do you weigh the car? I can't, and the shop I trust does not do corner balance even if I could sneak out the extra funds. Threre is an easy way:
The only other tool needed is an 8-ft long air hose and valve fittings to connect the Schrader valves on the two front tires together. I bought "valve extenders" at the car parts store. Truck stops also sell these for extending short valves on wheels with valve access problems. I cut the "extender" in half, and fitted an air hose between the fittings that thread onto the Schrader valve.
Put all tires at spec pressure, and fill the fuel tank (factory requirement). On the flattest concrete you can find, measure the distance from the concrete to the wheel rim (a set of pointed dividers makes this easy). There was less than 0.5 mm difference side to side - within the measurement error. I then connected the hose between the valves on the front tires, and lowered the pressure to 20 psi. This put the rims about 3 cm (1 1/2 inch) closer to the ground. The front tires exchange air through the hose, so the heavy side goes down, and the other side goes up as the air moves to equalize the pressure between the two sides. You will hear the air hissing until a new balance is reached.
I should have placed a 20 kg mass on a pillow on one front fender to see how sensitive the system is. I could press on one fender, and hear air hissing as it moved from the side I was pressing to the lighter side. I concluded that this was more that adequate to detect a 20 kg imbalance.
The observed difference side-to side was now 3 mm, showing that the balance was close, but not perfect. A small change (about 3 mm) on one of the higher corners balanced the front tires. After inflating the fronts back to 36 psi, the ride height was still well within the factory specifications.
Note that it is not necessary to repeat this on the rear. The car can be balanced by adjusting only one corner. The wheel on the opposite end and opposite side responds to change at any corner. If any two wheels are weight balanced, the other two will be as well (simple Physics).
The 4-wheel alignment was done after setting the balance. Ride and handling are excellent, much better that when I bought the car.
This was about a 1 1/2 hour job, plus the time to get and build the special tools (another couple of hours). Anyone care to try it? Let me know if you need the height settings and measurement locations. I will need to look them up again.
Cheers
08-27-2003, 07:44 PM
#2
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What a nice idea! I have a couple of questions for fellow UK Rennlisters...
1. How much does it cost in the UK to have the 964 corner-balanced?
2. Which garages have the facilities for doing it?
3. Where can we get, in the UK, the valve thingys that Springer refers to?
I'd be happy to give it a go!
1. How much does it cost in the UK to have the 964 corner-balanced?
2. Which garages have the facilities for doing it?
3. Where can we get, in the UK, the valve thingys that Springer refers to?
I'd be happy to give it a go!
08-28-2003, 12:38 AM
#4
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Springer3 -
The only way you could be sure you have a proper corner balance by equalizing weight between the two front tires only, would be if by some chance act of God your chassis was perfectly square, the car's center of gravity exactly midline, and you had your weight sitting in the driver's seat. These conditions are rarely met in the real world.
I'm not a suspension wizard, but I'm pretty sure you are not corner balanced.
Chip
The only way you could be sure you have a proper corner balance by equalizing weight between the two front tires only, would be if by some chance act of God your chassis was perfectly square, the car's center of gravity exactly midline, and you had your weight sitting in the driver's seat. These conditions are rarely met in the real world.
I'm not a suspension wizard, but I'm pretty sure you are not corner balanced.
Chip
08-28-2003, 02:15 AM
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Springer3
I agree with Chip, this is a very crude way of doing a corner balance. You really need a good set of scales to do a correct balance.
A good low cost way of doing the job is to borrow some scales. If you're a PCA member most likely someone in your region has a set of scales they will be willing to loan to you for a very low fee ($25??).
ABS is kind to mis-balanced cars. Without ABS you learn which corner of the car is "jacked" very quickly.
Dan
I agree with Chip, this is a very crude way of doing a corner balance. You really need a good set of scales to do a correct balance.
A good low cost way of doing the job is to borrow some scales. If you're a PCA member most likely someone in your region has a set of scales they will be willing to loan to you for a very low fee ($25??).
ABS is kind to mis-balanced cars. Without ABS you learn which corner of the car is "jacked" very quickly.
Dan
08-28-2003, 05:37 AM
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Robmug
I have spoken to three shops now which have all said that cornerbalancing is not entirely a necessary spend on a road car. They would gladly take my money from me, but suggested it can be spent better elsewhere! They all agreed that if I track the car its a different story.
I have spoken to three shops now which have all said that cornerbalancing is not entirely a necessary spend on a road car. They would gladly take my money from me, but suggested it can be spent better elsewhere! They all agreed that if I track the car its a different story.
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08-28-2003, 06:27 AM
#9
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Thanks John...however, no-one has actually proved that Springer3's method doesn't work...I know it seems unlikely, but even if it is crude, it may be better than nothing?
I can't get my head around the physics of it, it just doesn't seem right...but what if it is?!
My head hurts!
I can't get my head around the physics of it, it just doesn't seem right...but what if it is?!
My head hurts!
08-28-2003, 07:43 AM
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I've just been at Red Line at Teeside (I know, miles from anywhere...) and they mentioned they do four-wheel alignment and corner balance for a fixed price of £170.
Phil
Phil
08-28-2003, 08:33 AM
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Originally posted by Phil Raby
I've just been at Red Line at Teeside (I know, miles from anywhere...) and they mentioned they do four-wheel alignment and corner balance for a fixed price of £170.
Phil
I've just been at Red Line at Teeside (I know, miles from anywhere...) and they mentioned they do four-wheel alignment and corner balance for a fixed price of £170.
Phil
If you haven't treated your car to an alignment in quite a while, this would be a good add-on.
08-28-2003, 08:59 AM
#14
Originally posted by johnfm
Robmug
I have spoken to three shops now which have all said that cornerbalancing is not entirely a necessary spend on a road car. They would gladly take my money from me, but suggested it can be spent better elsewhere! They all agreed that if I track the car its a different story.
Robmug
I have spoken to three shops now which have all said that cornerbalancing is not entirely a necessary spend on a road car. They would gladly take my money from me, but suggested it can be spent better elsewhere! They all agreed that if I track the car its a different story.
08-28-2003, 09:05 AM
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Originally posted by Christer
Since owning a car which throws it's toys out of the pram as soon as you even start mixing tyres front and rear, I have always been a firm believer in corner balancing. Especially in a car which so easily exceeds the speed limits and is so sensitive to changes. If you consider that you can change your rear pink reflector for another rear pink reflector for the same price as a cornerbalance, I would say that there are plenty of things you can really waste your cash on instead of ensuring as far as possible that your car is properly balanced.
Since owning a car which throws it's toys out of the pram as soon as you even start mixing tyres front and rear, I have always been a firm believer in corner balancing. Especially in a car which so easily exceeds the speed limits and is so sensitive to changes. If you consider that you can change your rear pink reflector for another rear pink reflector for the same price as a cornerbalance, I would say that there are plenty of things you can really waste your cash on instead of ensuring as far as possible that your car is properly balanced.
