Track Testing: Is more weight an advantage in the wet?

We decided to head out for for another track test on a Saturday morning…and it was raining. We then had a good occasion to go back to try the weight effect test, but this time on a wet track. It is in fact true that with wet track conditions heavy, tall, or both, drivers suddenly become much more competitive. Why is this?

Weight gives more grip, more balance to the chassis? Could be, since weight generates a vertical force that increases grip on tires, even though weight also increases lateral force around corners and longitudinal inertial force both when accelerating and, in particular, when braking.

Start of test

1
The wet track at La Mola during our test

Base of the test with wet track started from the same parameters of the test published on the August issue, done on dry track conditions. Track was still La Mola at Rieti. Weight variance was also kept equal to 10 Kg, using the same technique of the rubber belt used by scuba divers. This was a must even greater then with dry track conditions, since we know that wet track can often change characteristics drying up and becoming wet again with rain, wind and sun showing up. Already ran in Vega rain tires were used, to avoid having more performance in the very first laps because of new rubber tread. As you might remember La Mola is a medium speed track with a couple of slow curves and a mixed sector of sharp changes of direction that determine a very low average speed and good need for grip. Then a faster sector follows with a long very fast curve and a straight to follow. This means our test has been done feeling the differences in all types of track sectors.

Plus 10 kg

Once more we started with a plus 10 kg weight so we could quickly get rid of the belt and go on with the testing on unvaried track conditions. First laps were quite ok with rain tires working well on wet asphalt. Braking, running along curves and acceleration exiting curves was strangely quite easy. To have any loss of grip, such as under steer entering corners or rear tire blocking effect during braking I had to strongly push and bring the kart to the very limit. Of course weight of the kart with the additional 10 kg had also the negative effect of slower acceleration exiting curves which I could only partially verify, and had to weight for the second session of test without the additional 10 kg.

2
The wet track at La Mola during our test

Lap times improved constantly since my confidence with kart and track grew lap after lap. Of course my driving was done following the rules of wet track. This meant I ran along curves on the external part of the track to avoid going on the asphalt that was covered with rubber that, as we know, becomes extremely slippery when wet. Lap times became constant after the first 6 laps, and best lap was set on lap 10 at 1.00.25 sec. Maximum rev decreasing of around 600 revs compared to dry track conditions, lost mainly because of lower speed on the long wide curve at the beginning of the straight and because of the need to anticipate breaking at the end of the main straight (where start/finish line is positioned).

Lap 10th 1.00.25 sec (Best lap)

Sector 1: 18.22 sec (best time)

Sector 2: 29.05 sec (best time)

Sector 3: 12.98 sec

Max revs: 13.175  (best revs)

 

Lap 8th 1.00.48 sec

Sector 1: 18.38 sec

Sector 2: 29.15 sec

Sector 3: 12.97 sec (best time)

Max revs: 13,120

 

Lap 6th 1.00.62 sec

Sector 1: 18.45 sec

Sector 2: 29.20 sec

Sector 3: 12.97 sec

Max revs 13,059

 

Best theoretical lap: 1.00.25 sec

Sector 1: 18.22 sec (best time)

Sector 2: 29.05 sec (best time)

Sector 3: 12.97 sec (best time)

 

Standard weight without the additional 10 kg

3
The Tony/Rok test kart

After the  first 12 laps times did not improve and we decided to take away the additional 10 kg. We had to be careful with track conditions since asphalt was wet, but it was not raining and any sun or wind could have dried the track quickly and our test would have not been valid anymore.

Now the feeling of the kart was incredible since sliding when running along curves and when accelerating exiting curves was impressive compared to the + 10kg setup. Braking was incredibly less effective even though I would have expected more difficulty with the plus 10 kg. It was as if the additional vertical force created globally much more adherence between rubber of the rain tires and the asphalt. The difference between this situation and the slick tires on dry track was that the kart has never really a problem of too much grip and is always sufficiently “free” exiting corners. So the feeling is that additional weight, up to a certain extent, increases grip without sticking the kart and tires to the asphalt (no negative effect then!).

Laps were constantly around the same values as with a plus 10 kg setup. So starting from lap 13 as first lap without additional 10 kg laps went on without being able to improve lap times, even though best final lap was very close to the previous setup. After 20 laps best time was set at the 19th lap with 1.00.30. Best theoretical lap was also higher then with +10 kg set at 1.00.29 sec. Best lap was then slower of 5 hundredth of a second and best theoretical was slower of 4 hundredth. So finally the + 10 kg seemed to keep constant or eventually slightly improve final setup and performance of the kart. Of course this still has to be evaluated considering specific wet track conditions, and surely there is a limit to more weight not impacting (or eventually improving) kart performance and behaviour, but surely final result of the test indicated how more weight in wet track conditions has a very different impact on kart performance compared to dry track conditions.

 

Lap 19th 1.00.30 sec (Best lap)

Sector 1: 18.24 sec (best time)

Sector 2: 29.07 sec (best time)

Sector 3: 12.99 sec

Max revs: 13.195  (best revs)

 

Lap 18th 1.00.58 sec

Sector 1: 18.43 sec

Sector 2: 29.17 sec

Sector 3: 12.98 sec (best time)

Max revs: 13,110

 

Lap 15th 1.00.72 sec

Sector 1: 18.50 sec

Sector 2: 29.24 sec

Sector 3: 12.98 sec

Max revs 13,100

 

Best theoretical lap: 1.00.29 sec

Sector 1: 18.24 sec (best time)

Sector 2: 29.07 sec (best time)

Sector 3: 12.98 sec (best time)

After the 20th lap track conditions began to change and asphalt showed some areas drying up with lap times improving quickly of some tenths of a second per lap, so we understood our test had ended exactly at the right time!