Rear LH02 tyres indicating practically no wear except for some diagonal lines in the internal area of the tread just toward the axle hub. The very smooth surface indicates low grip.

After our look at weights last month, as promised we finally managed to do an interesting track test on tyre compounds. Tyres, as we know, are one of the major parameters of kart performance. LeCont is a company that works 100% on performance tyres.

We were at the international track of Viterbo. Asphalt temperature was 37°C.

The tyres

LeCont kindly and promptly sent us three sets of different tyres named LH01, LH03 and LH02, together with a set of rain tyres. The wets have not been part of our test. The three LH tyres go from the softer compound (LH01) to the hardest (LH02). Such hardness is measured in IRHD grades:

• LH01 - 48 IRHD
• LH03 - 54 IRHD
• LH02 - 60 IRHD

The three types of tyres are also recognisable from the coloured line that runs along the entire diameter of the tread. Blue for LH01, green for LH03 and yellow for LH02. Dimensions are 11x7.10-5 for the rear tyres and 10x4.50-5 for the fronts. The LH tyres in general are made to be simple to use and have long lasting performance. They are made with polyester and have quite a soft structure that works quite well with a low grip track, but maybe are not as high performing as other racing tyres on high grip tracks and with rubber on the asphalt and high temperatures.

Testing begins - LH02

Given that all three sets of tyres had the same structure, differing only in tyre compound, the idea was to understand how a difference in tyre compound hardness can act on tyre performance and on lap times. We used the hardest tyres, the LH02, first. The pressure was set at 9,5 psi. We know that for LH tyres LeCont indicates a 12-12,5 psi working pressure once the tyres are up to temperature. There were no other karts on the track, so very low grip. This was the reason for using 9,5 psi instead of a more traditional 8,5 psi. In the first laps I needed to find the right pace and also to try to get the feeling for both the tyres and the track. Grip was not particularly high and the performance was acceptable, but not astonishing. The balance of the kart was good and no particular defect was shown by the tyres, with grip quite constant from the first laps and no sudden loss of grip at any time. Good performance entering the curves, but some limits in traction and generally the rear tyres had limited grip especially along fast curves. Lap times started from high values both for my need to warm up and for the need of the tyres to warm up!

• Lap 1: 64.68
• Lap 2: 64.25
• Lap 3: 63.16
• Lap 4: 63.10
• Lap 5: 62.57
• Lap 6: 62.15
• Lap 7: 62,01 (fastest)

After the 7th lap, the times were more or less constant. The hardness of the compound was evident all the way. There was good overall performance by the LH02 tyres, but the need to have long lasting tyres with harder compound had on the other hand some limits on a low grip track and especially when lateral acceleration on fast curves asked for high lateral grip. The braking performance anyway was also pretty good. After around 15 laps the tyre tread showed very good resistance to wear, which is the main aim of the LH02 tyres.

Rear LH03 tyre with grainy tread surface indicating much greater grip compared to the LH02. Still just a little wear in the internal area of the tread indicated by small diagonal lines.

LH03

We then quickly changed to softer tyres, the green LH03 tyres, and starting pressure was 8,5 psi. Already in the first laps I felt the performance was much higher. Grip was greater with the tyres doing all the work to obtain grip even with still almost no rubber on the track. Traction and lateral grip were greatly improved and the lap times quickly confirmed my feelings.

• Lap 1: 62.03
• Lap 2: 61.70
• Lap 3: 61.18
• Lap 4: 61.39
• Lap 5: 61.00 (fastest)
• Lap 6: 61.09

Lap times went on constantly after lap 6. A great difference was evident, especially at the end of the great straight of the start where the very fast right turn needs great grip, especially on rear tyres, so that speed can be kept high without releasing the accelerator for too long.

Front LH03 tyres with slightly grainy surface and no real wear.

Rear tyres with good grip slide just slightly towards the external part of the curve permitting the kart to turn following the right trajectory. With the harder yellow LH02 tyres such a curve was pretty difficult and speed had to be reduced too much.

The front LH01 tyre with good grip indicated by the tyre surface but also rubber being ripped by excessive sliding when pushing hard for performance. Lines both diagonal and longitudinal are present in a wider area of the tread. Set-up should be improved.

LH01

The final test was done with the blue LH01 tyres. Another 6 IRHD degrees reduction for the softest tyres of the set. The starting pressure was again set to 8,5 psi. The feeling on the first laps was of great ease in driving the kart. Higher grip and a slightly better driving sensation, better than the LH03 tyres. But the astonishing performance came from the fact that the high grip left the kart free to run smoothly along curves and exit them.

Rear LH01 tyres with grainy tread surface indicating good grip but also visible wear effect in the internal area of the tread with greater diagonal lines formed. The balance between performance and wear (20 laps) is still very good.

Pushing harder and harder, the lap times decreased constantly. Braking and entering curves was great and also the traction and lateral grip given by the tyres was excellent. When the limit entering corners was passed, the front tyres slid laterally, but performance was not impacted too much and control of the kart was always possible.

• Lap 1: 61.02
• Lap 2: 61.00
• Lap 3: 60.80
• Lap 4: 60.41
• Lap 5: 60.72
• Lap 6: 60.70
• Lap 7: 60.20
• Lap 8: 59.90 (fastest)
• Lap 9: 60.01

So the blue tyres gave, predictably, the best performance. And, incredibly enough, the lap time difference was very similar, around 1s, both between LH02 and LH03 and between LH03 and LH01. So it is as if a change of 6 degrees of IRHD is equal, at least on the Viterbo track and with the Rok kart, to one second of lap time. The wear of the blue and green tyres was also very low and so performance seems to be very good combined with longevity of the tyres. Only the front tyres showed some wear of the tread because of lateral sliding when pushing really hard entering the curves. This aspect could most probably be solved though by working on chassis set-up.