What Can You Do To Cure Understeer In Your Racecar?
You might have faced a situation where you are looking to cure understeer in your race car? The temptation is to head off looking at all kinds of suspension changes. This is fun but can get confusing fast. In this article, I share an experience where we cured understeer using information from our tyres to guide us – and not in the way you’d first expect.
You Discover You’ve Got Understeer. Grrrr
So imagine you are out on track. You’re driving your favourite racecar. It is a lovely sunny day. The track is dry and it feels like you have the place to yourself. Your warm up has gone well and you are now starting to press on to see what kind of lap time you can achieve.
Arriving at the fast sweeping left corner, the front tyres start to loose grip. The turn-in was fine. Once you get to the mid-corner though, the balance completely changes.
As soon as you start to accelerate, the front of your racecar starts to push out. The more you press on the wider you go.
Understeer is great in a road car, preferable even, but not what you’re after in a racecar.
If you’ve ever felt understeer like this then you will know, it can be extremely frustrating.
But You’ve Done The Hard Work!
As a driver you have done all the hard work! You have got the car into the corner, got it rotating and just at the time you want to get back hard on the throttle… aggghhhh… no front grip!!!
Turning the steering wheel more will only make your situation worse. You have no option but to back out and wait.
What you want is to be able to pin the throttle and get off down the straight. You know every 1 mph you can gain through the corner you’ll carry all the way until the next braking point.
Unless you find a way to cure your understeer it is not going to happen. Worse, you are giving away some of the easiest lap time. Plus – if you are racing – you are leaving yourself vulnerable to attack.
Mid corner understeer? No. No thank you!
Our Experience To Cure Understeer
So how can you get rid of it? What can you do with your tyres?
Recently we had this challenge. The racecar had been well balanced at the previous track. We did nothing to change the setup yet now we found ourselves with this mid-corner understeer.
Whenever the driver (me!) got back on the throttle from mid corner, the front would wash out wide. What it actually felt like was the tyre was “folding-in” under itself when you did this.
As an engineer the first thought is that the front axle is too stiff so we should be looking at softening it off. You might be following a simple guide like this one which will also say the same. The car we run has a front anti-roll bar (sway bar) so that might have been the logical thing to soften off and try.
Real Clue In The Tyre Pressures
Before we did though we looked again at the tyre pressures. If the front tyres were being worked hard, then you would expect the front pressures to be high. What was surprising was that they weren’t. If anything they were a few psi low.
The track surface has a reputation for being smoother than the previous track we had been at. It dawned on us. Rather than the front tyres loosing grip because they were over-worked, perhaps they were under-worked?
A Surprising Solution – Stiffen The Front
The surprising solution we found to cure understeer was to increase front stiffness. We did this over a couple of runs. First increasing the bar stiffness. Then increasing the tyre pressure.
The result was that the car came alive, the tyre pressures came up at the front and the driver could get on the throttle as soon as the car was ready.
You hear people say, “Get your tyres right, before looking at the rest of the suspension…” and that worked here.
For more on how to set your tyre pressures perfectly use this tool.
Then interpret your tyre temperatures. with this one.