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Track Test Tech | Adjust the front track width. track test

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ADJUST THE FRONT TRACK WIDTH

Track width is a fundamental set-up parameter that is easy and quick to adjust. Based on our test driver’s impressions and AIM telemetric data, let’s discover how widening or narrowing front-end track actually impacts kart performance

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What

Verify how the kart responds to front track adjustments

How

Test 1: “two-notch” front width
Test 2: “five-notch” front width

Where

Adria International Karting Raceway

In which conditions

Even and well-kept tarmac, but completely rubber-free (the test was done in the middle of the week); this is why we opted for extremely high-performance tires like Vega White

Weather
26°C (79° F)
IN THEORY
FRONT TRACK WIDTH

Front track width is one of the factors that determines how much grip the front end has and so how fast the kart enters and covers corners. There are two main principles that regulate to front width. First: a wider front track increases the difference in height between the front tires while steering (in itself determined by the Ackermann angle), with an obvious consequence on grip. The second has to do with the fact that the front inside tire rotates more than the outside front tire, with an ideal rotation point that obviously varies according to front track width: the wider the track, the greater the radius of the ideal curve trajectory to follow. So, to sum up the two: the wider the front track, the more front end grip and the better performance through wide-radius bends. The effect is the opposite with a narrower front track.

REAR TRACK WIDTH

Our test is concerned with variations in front track width, but rear track also plays an important role. On today’s karts, this is usually set at the maximum regulatory limit of 140 cm. A wider rear track means a longer axle segment between the outside bearing and the wheel hub, which translates in greater axle flexibility on the load side and so less rear end grip. Narrow the rear track and you get the opposite effect.

TIRES AND GRIP

If you use soft tires on a track without much rubber you won’t get excessive bite (neither in the front nor the rear) and so you’re not going to feel the typical draw-back effect while accelerating. Even so, you need to make sure front and rear grip are well balanced. Setting the front track very wide increases bite at corner entry and mid-corner handling, but could give insufficient traction on corner exit, as the rear inside tire will remain slightly lifted even without much steering. In addition, as a rule of thumb, high front end grip causes greater rear end sliding.

FRONT TRACK 2 NOTCHES
53’’600
Set-up
Rear track 140 cm
Camber Neutral
Caster Neutral
Rear height Low
Front height Low
What we expected

For our first test session, we decided to do several laps with a standard set-up. The front track was set by sliding the hubs to two notches – so, not very wide, for a very free front end. With these settings on a track with poor grip conditions and where a couple of fast wide bends are key – the one leading to the finish stretch and the one at mid-straight – we were expecting poor front-end behavior. Let’s see if that was actually the case.

Driving impressions

The feeling was that the chassis behaved nicely the whole way, with a good overall balance and with the high-grip Vega tires making a difference, at least in terms of corner trajectory. The two critical points turn out to be precisely the track’s two key fast bends, where corrections (especially at mid-bend) cause serious loss of time.

Analysis

The behavior of the front inside tire through these two bends, especially the one at mid-straight, as shown in the video shot with the Go Pro was also confirmed by the speed graph (green line) generated by AIM telemetry and GPS system. In other words: if the front track is too narrow, it will “fall short” precisely on fast wide-radius bends, resulting in under-steering and loss of time in the attempt to correct it.

Tires

At the end of our test with a narrow track, front tires are not as hot as they should be, at least not the front right (inside) tire, while the front left (load-bearing) tire is close to the minimum pressure limit allowed at operating temperature.
At this point we’d like to remember the following general rule of thumb: if tires have so little bite that they always slide and always do so excessively, they won’t warm up sufficiently, especially on a track with poor grip conditions – like the Adria Karting Raceway during our test.

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