We are specialists in suspension Established in 2004 / Rapid Response to Email / Technical Staff as Standard

  ABOUT US    |    CONTACT US    |    Project Work    |    Blog    |    Bilstein |

Telephone us 01903 879111

Corner Weighting & Chassis Balance

 

Back to Contents

 

Corner Weighting and Chassis Balance

 

 

Corner Weighting Service (£180 inc vat) and Chassis Optimisation service (from £80 inc vat per axle)  from Balance Motorsport - located in South East England near Brighton and Worthing in Sussex Countryside


Please contact to make an appointment Please note no cars over 2000kg, no SUVs


 

What I do

Recently a customer brought an interesting car to the workshop. A classic CRX from 1989 the 1.6 16v version. He said he was getting excess oversteer. Now I know these are well balanced and do not sport a large rear anti-roll bar. We identified the shocks were too stiff but he still had the roll bar disconnected. The car came in and it was noticed the roll bar was fouling on a cross tube reinforcement. I set about fixing this with an upgrade to adjustable links and replaced the rubber eye bush in the bar with a steel insert. This was produced by a local engineering firm I've used for all sorts of things. Very skilled chaps. The point is suspension work isn't simple. The cross weights were out on the CRX. 47.5% Reverse Wedge across LRRF. This wasn't helping oversteer in a left hander. The gain from optimising for one direction is rarely worth the loss in the other. e.g if a circuit has 6 bends and 4 are right handers, it would be unwise to optimise the chassis only for right handers.

Balance Motorsport provide something different. Your car stays with me while we assess the requirements derived from initial testing where you point out the issues to us. You tell us what you want and I will deliver to the best of my ability what you asked for. Sometimes it might require a bit of finessing but we usually get there first time. If upgraded parts are required then you can get a quote for those. For example if you brought a front wheel drive car in with lots of understeer and the set up is good then really a larger rear anti-roll bar would usually be required, often with a change in ride height.

Below was the CRX on the scales.

 Corner Weight Scales at 50% Crossweight

50% is not a guarantee! Unless you have adjustable drop links then to get to 50% is not always possible, however the last 3 cars into the workshop had non-adjustable links and all left at 50.0% with the driver in. 


Some coilover basics

- when installing coilovers align left to right right side units.

- please ensure coilover rings stand a chance of turning. If they are heavily corroded there will be a full strip and repair service offered for suspension brands that Balance Motorsport retail. The service does not include freeing off cold welded spring seat adjusters.

 

Corner weighting using scales is the theoretically simple practice of adjusting the suspension preload to ensure an even 50% cross weight (for a typical circuit with left and right turns). The logic is simple, a 4 wheeled vehicle no matter what it's weight distribution front to rear or left to right can be optimised so that across the diagonal the weight split is 50%. Balancing the cross weight ensures the car will be as good as it can be, round both right and left hand bends. If you only travel in one direction that is a whole different kettle of fish!

So for example, below this car not only has 50/50 front to rear weight distribution, but also side to side, and even corner weights to.

Car overhead 50/50 weight split and 50/50 cross weight



 

Now let us suppose that in reality the weights are as follows

 

overhead car 60% cross weight


We can see that 60% of the weight is found across the left rear to right front cross weight. This car would work well around a right hand bend but less well around a left. How can we make it 50 % cross weight without actually moving weight around?

Well what we do is add preload to the opposing diagonal (we may need to actually reduce preload on the other diagonal as well). When corner weighting (assuming the anti-roll bars are disconnected) you will find one pair across one diagonal will be low and one pair across the other will be high. If we add preload on just one corner the opposing corner will increase as well. e.g if we turn the spring collar clockwise on Left Front the figure will increase. Right Rear will also increase. Right Front will decrease as will Right Rear.

The end result is that when you corner weight a tin-top the ride height with driver on board will not be even all the way around. That is an inevitable result of balancing something that is not balanced!

However it is very easy to go too far and then end up with the car on stilts. The "secret" is to install each coilover with a fixed measured amount of preload (measured with a tape measure) between left and right units. Then set the ride height for correct rake (don't make the mistake of setting the ride height using the arch to wheel measurement - even if the ground is level it's unlikely your car will be completely square!).

Now set the toe and the camber angle. Put the car on the scales and it won't be a million miles out. If you set the ride height using a tape measure rather thankeep the preload on the units the same, the chances are you will be a way off 50%. The best advice is to make small changes at a time. If you cannot disconnect the anti-roll bars on both ends then remember the figures will play tricks on you - increasingly LR can also increase RR as the roll bar transfers the preload over! In this instance it is even more important to make small changes. We once had a Rover 216 race car here for corner weighting that some University Students gave up on (they were used to a single seater) it really was miles out but it was the fact the rollbar links weren't adjustable that caused the problem. When theory tells you one thing and in practice the scales tell you another there is always an explanation! (oh and make sure the scales are plugged in correctly that can be confusing as well!)

 

CALL TODAY TO BOOK IN 01903 879111

 

 

Back to Contents