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Corner Weight

Motorsport Wheel Alignment Fundamentals

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What about the performing of Corner weight to a car.

Didn't see any module relative to this topic.

In my opinion, is something very important especially for a race car. I was searching the web in order to understand the whole thing and collect information, and i was expecting to see something here.

Thanks

We are planning a separate course covering corner weighting. We didn't include it in the Fundamentals course as it is a more advanced technique and of course requires a reasonable investment in the corner weight scales. We do however corner weight all our own cars.

Andre, may be it's a little bit strange questions.

But, at which level of racing it make sense to setup coilovers on corner weights? In other words, for example, is it possible to reduce lap time using cornerweight setup for track-day enthusiast? Or it's for pro-level where each 0.5 psi of tyre pressure is significant? :)

And another question - if it's reasonable to have different camber on right and left sides for "left" or "right" tracks, why we still want to have CR weight 50%?

Hi there Alexander.

Until Andre’s response, which i will like also to read, I would like to share my opinion with you.

The main reason for corner weighting your car is for getting the best balance out of it. Meaning that your car will act the same way trough the left and right corners.

So yes you can reduce your lap times if your car drives “friendlier” to you, giving you at the same time more feedback of what is happening.

The most important number you are looking using the weight scales is the Cross Weight. Meaning that the total amount in Kg (or pounds) of the front left tyre with the right rear tyre, must be as close as possible with the total amount of the right front and left rear tyre.

And the best example i can give you for a better understanding is to think your car like a table with four legs on a level surface. Four wheels, four contact patches to the ground , same as a table. If a leg of the table is shorter that the rest, then your table is out of balance and you have to either add some length to that one, or to remove some from the other three.

And again yes you can have different amount of camber on each side depending of your race track. You are always looking for the best or the fastest overall lap you can get, but again the corner weight balancing of your car is better to be as close to 50% as possible.

Im also interested in the corner weight course and to get more information about that.

PanMav Thanks for your comments/suggestions.

Suprazz you are welcome!

To clarify, the aim is to get the best tyre loadings, or more specifically tread, to get the best overall lap time while maintaining sufficient tyre wear to last the race, or refuelling range (endurance they commonly get 4 fuel stops per set).

For a mixed track, where there is a similar requirement for left/right turns, or to simplify setups for clock-wise and counterclock-wise a symetrical setup may be prefered.

For some tracks where there is a heavy bias towards turns one way (like circle track) the car may be set up with a strong bias for that, to equally load the tyres under cornering as that is where best grip is achieved. This may include a weight offset towards the inside of the track, differing cambers and other geometry like caster, cross-weighing (AKA wedge or jacking) so although the tyres are unevenly loaded at rest the drive tyres are more evenly loaded under acc'n out of the corners, to having physically larger tyres on the outside as can be seen in sprint cars.

I'm not sure if other race series' coverage has it, but sometimes F1 and the Aussie Supercars will show what the tyre tread temperatures are using an infra-red camera, which gives some idea of which parts of the tread are doing the work.

I'm rather looking forward to the new lectures as there is always something one has forgotten, mis-understood or plain never known - at a minimum I expect some good discussions.

In the meantime, I'd suggest checking out your bookstores, AMAZON, and other book retailers for relevant books as using different media sometimes makes things much clearer than one information stream alone.

Hello everyone

Corner weighting course should be live by the end of this quarter, will be led by me. It's a tricky subject to get your head round and for anyone who has ever corner weighted a car before, will know how frustrating and time consuming it can be trying to get the car balanced.

As everyone has said, a cross weight percentage of 50% is the usual aim with circuit racing, rallying, drifting etc, with the exception of oval racing. As PanMav said, wobbly table is a great example, and one we use in the course. If a leg of a table is shorter, then the other corner of the table will rock or lift. Meaning the weight is spread diagonally, which is why we aim for a cross weight percentage rather than a 'left to right' or 'front to back' (which are both important factors!)

Matt

Forgot, there is an added complication for live beam axle vehicles as found on the traditional 'muscle' car and older saloon/rally cars.

There is a torque reaction between the axle and the chassis to counteract the output at the gearbox tailshaft. For example, if the engine is producing 500 lbs.ft of torque, and the gearbox gear ratio is 2:1, that means there is 1000 lbs.ft to be reacted to that is applied through the suspension to the chassis. If you assume a 60 inch track, 5 feet, that means there will be a difference of 200lbs force applied to the rear tyres - AND the fronts as wedge/crossweight. As the suspension springs will be inboard of the tyres, the difference there will be greater - if they are, centre to centre, 36 inches, or 3 feet, apart that will mean a difference of 333lbs force.

That is why you will have observed some cars with open diffs (non-limited) only spinning the right rear - the tyres are getting equal torque (how differentials work) but because the right tyre is more lightly loaded it will slip more easily.

As the reaction is effectively adding wedge, to both fleft and right, there may not be noticeable body roll for normal road vehicles, but you may have noticed

drag cars squating on their right rear as the reaction is helping compress the right rear spring and extend the left rear. For those applications, there may be body roll evident as once the left front is picked up there is no roll resistance from the wedge across the front axle.

That body roll will also affect the rear geometry as the leaf springs, or longitudinal links, move through different arcs causing rear steer changes as the axle is turned slightly relative to the chassis.

Under engine braking, the affects will be reversed, but as the torque reaction is much less (less torque required to overdrive the engine and usually higher gear/less torque multiplication) it is often regarded as irrelevant.

We usually reply within 12hrs (often sooner)

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