Five Chassis Tuning Tips for Beginning Racers

By January 15, 2014Track Day
5chassistips-beginners

Ever since the first cars appeared on dirt roadways there have been the death defying adventurers that have wanted to push the laws of physics and the limits of their growling chariots. The challenge is always to get more horses and better “handling”.

While horses are expensive, it’s actually relatively easy to achieve some pretty awesome gains on just about any production motor.

Handling on the other hand; well, very often this is seen as the Nerds domain. People with laptops with more processing speed than the Challenger, working on mathematical formulas that would leave Einstein baffled. Truth is; once you understand what’s going on, meaningful handling improvements are within your grasp… and a sweet handling ride should definitely be on every racing enthusiast’s to-do list!

1. Fine Tune Your Wheel Alignment

The first thing we need to do is find out what our wheel alignment settings are. So get your car down to the local tire dealer and make sure that they have 4-wheel alignment equipment. In other words he can measure each wheel simultaneously, without having to re-position the car.

Get a print out of the results and study them carefully: You don’t want to see major (out of manufacturer’s specification) differences left to right.

If you see something like a left rear with a +4mm toe-out and a -2mm toe-in on the right rear, on a beam axle (such as commonly fitted to front wheel drive cars) or a solid axle (such as fitted to the Mustang) – this would not be good. The reason being you probably have no adjustment in this plane, and would need some slotting or bending of mounting brackets.

If you’ve never done this before, now’s the time to remember to keep any changes to small increments – and do start with the easy ones!

2. Switch to Lower Profile Tires

Light-weight wheels with low profile tires are the first step. Unsprung weight is a killer of sweet handling, as is a tire that flexes under hard braking or cornering. By all means consider upping the width, but always mindful of the correct rim offset, so that the wheels actually do fit inside the arches. Also be careful of the effect of a change in rolling radius on the overall gearing of the car.

3. Find Your Camber Sweet Spot

Next you want to look at the camber – if you’re doing any form of track work, you’re probably going to need a bit of negative camber on the front wheels – start with a degree and progress from there. Don’t forget chassis tuning is often a trade off: Too much camber and the beast will be very nervous in a straight line and could even “bump steer” (yes the term describes it perfectly). If you have a tail-happy RWD drive, like some of the older Beemers you might also want to dial in a bit of negative camber at the rear.

Now we can start adding some of that trick stuff, you see the pro race cars bristling with.

4. Keep Your Suspension Points Tight with a Strut Bar

Under hard cornering the monocoque (single shell) chassis tends to get all out of shape, so we want to keep the suspension mounting points from moving around too much (relative to each other). We do this by adding a strut brace – a tube or sometimes forged bar that ties the tops of the struts together. This is a bolt-on item, and companies like Eibach and Tanabe make really good products at reasonable prices.

5. Reduce Body Roll with Stiffer Suspension Components

Another bolt on item that any serious track car needs is a set of springs and dampers to meet the hectic conditions encountered on a racetrack. There are so many combinations of spring and damper that it’ll be impossible to cover them all. So we’ll just look at cars with struts and/or coil springs and dampers.

The objective is to reduce excessive body movement which results in significant geometry changes that negatively impact on the handling. By fitting stiffer springs (reduced coil diameter, increased wire diameter, or more coils/ft) we limit body roll. But a stiffer spring will oscillate wildly with the standard dampers, so you need to fit uprated dampers that match the springs – if possible fit a set which are bump and rebound adjustable. (Koni make a great damper which you can even adjust from inside the cockpit).

First prize here, would be to fit a “coil over damper” system – like you see on motorcycles and most serious race cars. This allows for (amongst other advantages) corner balancing the chassis by adjusting the spring pre load on each corner. At this time you could also seriously look at making changes to ride heights – although this can have quite radical effects on handling behavior.

Continually Test & Fine-tune Your Changes

Once you’ve got this basic setup completed, it’s time to get out on track and test the changes. Remember to record all settings and compare setting changes to lap times and sector times. And don’t forget to up your tire pressures for the track.

After a few days the smile will vanish and you can contemplate the other goodies on your wish list: Those carbon fiber doors and fenders, the fancy wishbones and those must-have stabilizer bars and bushes.

Photo credit: bortescristian Flickr CC

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