Much discussion has been had about the relative merits of Ortmanns vs. Super Tires, or urethane tires vs. silicone tires, particularly in the US and Canada, where these two types of tires are popular. Ortmann tires have a reputation for gripping regardless of dust, while silicone tires are said to grip best on dustless track. This test was designed to measure relative track speeds of these tires in clean and dusty conditions.
All tires were run on the same car (Fly Racing Porsche GT1-98), with the same wheels (Slot.It 17x10mm). This car was selected because it is very stable, and is easy to drive consistently. Testing was done on the same lane of East New York Raceway, a 61’, wood track surfaced with interior flat latex paint. For the first test, the track was cleaned by running a car with Super Tires, cleaning the tires every few laps with a sticky label, until no more dust was picked up. As a result, the track was very clean and dust free. Tires were then tested one after the other, for 50 laps each.
The second round of testing was done several days later, after a moderate coating of atmospheric dust had accumulated. Ortmann and rubber tire cars had been run in the interim. No track or tire cleaning was done at any time for the second test. Dust was apparent, adhering to the tires, after each pair had been run.
All tires fit the Slot.It rims very well, with a flat tread. All tires were very true as run. We rounded the outer tire shoulder slightly, if it were square cornered. Each pair of tires was run for 50 laps; best lap times are shown below:
Super Tires Silicone 4.922 sec.
Ortmann Urethane 4.935
Slot.It S2 Silicone 4.981
Slot.It S1 Silicone 5.058
Tru Grip Urethane 5.137
Jel Claws Rubber 5.148
Moderately dusty track:
Slot.It S2 Silicone 4.977 sec.
Super Tires Silicone 4.979
Ortmann Urethane 4.987
Slot.It S1 Silicone 5.048
Tru Grip Urethane 5.176
Jel Claws Rubber 5.176
On a very clean track, the Super Tires were fastest. On a moderately dusty track, the Slot.It S2’s were slightly faster than the Super Tires and the Ortmann tires, and both Slot.It tires were slightly faster than they had been on a clean track. However, a difference of .003, or even .010 seconds may be attributable to chance, or uneven driving (an insignificant difference).
Only the Slot.It tires appeared to be unaffected by the presence or absence of dust. All the other tires were significantly slower on the dusty track. Ortmann tires were .052 sec slower, which is a significant difference. These tests show results which differ from what we expected, so expect more tests to follow!