Corner balancing explained
What corner weights and cross-weight (wedge) mean, why 50% cross makes a car handle the same both ways, and how corner balancing actually works.
cross % = (RF + LR) ÷ total × 100— one diagonal pair's share of the car.- You change cross-weight without moving any mass — just spring perch heights.
- Scale the car as it races: driver aboard, fuel at level, flat floor, final ride height.
Put a car on four scales and you'll almost never see the weight spread the way you'd guess. Corner balancing is the art of adjusting how that weight sits — not to make it "even", but to make the car behave identically in left and right corners.
The number that matters: cross-weight
Cross-weight (or wedge) is one diagonal pair's share of the total:
cross-weight % = (RF + LR) ÷ total weight × 100
At 50% the diagonals carry equal load and the chassis responds symmetrically. Above 50% the car gains grip in left-handers and loses it in right-handers; below 50%, the opposite. Oval racers run deliberate wedge because they only turn one way — a road or circuit car wants 50.0%.
Reading the four numbers
Four scales give you four readings, and they answer three completely different questions. Confusing them is the most common reason people "fix" the wrong thing.
| Reading | What it tells you | Can you adjust it? |
|---|---|---|
| Front / rear % | Where the mass sits along the car. Sets the basic handling balance. | ✗ move mass |
| Left / right % | Sideways bias — driver, battery, fuel tank position. | ✗ move mass |
| Cross-weight % | How the diagonals share the load. Sets whether it turns the same both ways. | ✓ spring perches |
| Corner weights | The raw inputs. Useful for spotting a seized damper or a bad scale. | — |
Why you can't fix it with ballast alone
Front/rear and left/right distribution are set by where the mass physically is — engine, driver, tank. Cross-weight is different: you can change it without moving any mass, just by adjusting spring perch heights. Raise one corner and you jack extra load into it and its diagonal partner, taking it from the other diagonal. That's why it's also called "putting wedge in".
Work through it with real numbers. Take a 1,220 kg car sitting at LF 320, RF 330, LR 280, RR 290. The RF + LR diagonal is 610 kg — exactly 50.0%. Now wind the LF perch up a few millimetres and jack 10 kg into that corner: LF becomes 330 and RR becomes 300, while RF and LR each shed 5 kg to 325 and 275. The cross diagonal is now 600 kg, or 49.2%. Nothing was added to the car and nothing was moved — the load simply took a different path to the ground.
That is also why you always adjust diagonally opposite pairs and re-scale after every change. Chasing one corner at a time turns into a loop you never close.
Disconnect the anti-roll bars first
This is the step most home sessions skip, and it quietly invalidates everything after it. An anti-roll bar connects the two sides of an axle: if it is under any preload when the car goes on the scales, it is holding load in one corner and taking it out of the other, and you will "correct" a cross-weight error that only exists because the bar is twisted.
Disconnect at least one end link on each bar before scaling, balance the car, then reconnect — and check the links drop back on without having to be levered. If a link has to be forced into place, you have just put the preload back and undone the session. Adjustable end links exist for exactly this reason.
How a corner-balance session actually goes
- Set ride heights first
Corner balancing is done at your final ride height, alignment roughed in.
- Load the car as it runs
Driver weight (or ballast) in the seat, fuel at your normal level — this changes the numbers a lot.
- Equalise tyre pressures
Set all four to the same cold pressure. Uneven pressures change rolling radius and corrupt the reading.
- Disconnect the anti-roll bars
Bar preload masquerades as cross-weight error. Drop an end link on each bar before you read anything.
- Scale it level
A flat, level pad: even a few mm of floor slope corrupts the reading.
- Roll it, bounce it, re-read
Suspension binds on the scales. Roll the car back and forth and bounce each corner before every measurement.
- Adjust perches diagonally
A small turn on one collar moves cross-weight a few tenths of a percent; re-scale after each change.
- Reconnect the bars, re-check alignment
Links must drop back on without force. Perch changes also move ride height slightly, which moves toe and camber.
What it fixes (and what it doesn't)
A balanced car turns in consistently both directions, puts power down evenly out of corners and brakes straight. What corner balancing can't do is overcome a fundamentally lopsided static distribution — it redistributes diagonal load, it doesn't move the engine. For that you're into relocating mass: battery to the boot, lighter seats, and so on.
When you can't reach 50%
Sometimes the collars run out of thread, or every adjustment trades cross-weight for a ride height you no longer want. Know when to stop: ±0.5% is close enough for anything short of a competition car, and the difference between 50.0% and 50.4% is far smaller than the difference a set of tyres or 2 psi makes.
If you are a long way out and running out of adjustment, the problem is usually not the perches. Check the obvious things first — a floor that is not level, a seized damper, a broken spring, a sagging spring on one side, or a car that was scaled without the driver. If the platform genuinely cannot get there, move mass instead: battery position, seat, ballast placement.
Street car or track car?
Both benefit, but the payback is different. On a track car the point is predictability — the same rotation into left and right corners, so you can drive to a limit that does not move. On a road car it is subtler: consistent braking, a car that does not pull under load, and even tyre wear across a set.
What matters more on the road is that you scale the car the way it lives. A road car carrying a passenger, a full tank and a boot full of luggage is a different car from the one you balanced empty. If the car spends its life loaded, balance it loaded.
FAQ
What should my cross-weight be?
For road and circuit driving: as close to 50.0% as you can get, measured with the driver aboard. Only deliberately offset it (wedge) if you race ovals or a track that turns predominantly one way.
Do I really need to sit in the car?
Yes — 75–100 kg placed off-centre changes corner loads by several percent, easily more than the imbalance you're trying to fix. Use the driver or equivalent ballast in the seat every time.
Can I corner balance without adjustable coilovers?
Not meaningfully. Cross-weight is adjusted through spring perch height, so you need height-adjustable spring platforms on at least one axle. Without them, focus on mass placement instead.
Do I have to disconnect the anti-roll bars?
Yes, if you want the numbers to mean anything. A bar under preload holds load in one corner and takes it out of the other, so you end up correcting an error the bar invented. Drop an end link on each bar before scaling, and make sure the links drop back on without being levered.
How often should a car be corner balanced?
After anything that changes ride height or spring load — new springs, new coilovers, a ride-height change, a big weight change like a stripped interior or a battery relocation. Otherwise it holds. It is worth re-checking once a season on a track car, because springs settle.
Is corner balancing the same as wheel alignment?
No, though they interact. Alignment sets the angles the wheels sit at (camber, toe, caster); corner balancing sets how much load each wheel carries. Changing perch height changes ride height, which changes the angles — so corner balance first, then alignment, and re-check the balance if the alignment needed a big correction.
What if my car is heavier on one side?
Almost every car is — the driver, the battery and the fuel tank are rarely on the centreline. Left/right imbalance is fixed by moving mass, not by perch height. Cross-weight is the part you can adjust, and you can hit 50% cross even on a car with an 8 kg side bias.