Thread: LT vs Radial

Originally Posted by Pedro_The_Swift

The front tyres we raced on at Donald were "tractor" tyres,, 16x5",, REALLY high profile,,
no more than 6" of tyre on the road,,


and at 210kph they raised up, in the centre, quite a bit!!


<snip>

interesting that you mention this Pedro as I was thinking of this characteristic when I wrote my little reply above.

This is a typical characteristic of a Bias/Cross ply tyre.

Watch a Top Fuel Dragster as it launches and watch the Goodyears grow. They use this as an adjunct to the cars normal gears when launching down the strip, and it's for this reason Drag tyres will always be bias construction. Drag car tyres grow enormously at speed. A radila tyre, due to its construction can't do this.

Back in the early eighties at the height of the Ground Effects era in Formula One a tyre war was raging between Goodyear and Michelin, with Goodyear using bias construction, and Michelin radials.
Goodyear had the upper hand drawing on its previous decade of racing dominance until the sliding skirts that were used on the outside of the ground effects tunnels were banned, and a mandatory minimum ride height introduced. These skirts literally ran on the ground and sealed off the underbody venturi, maximising the pressure differential between the upper and lower body surfaces and hence maximising down force.
The FIA, in its endeavour to reduce cornering speeds banned sliding skirts, forcing the teams to run their cars with virtually no suspension to minimise ride height changes and keep downforce and hence grip at a maximum.

Instantly the rules had turned in favour of Michelin as a radial tyre grows very little at speed, whereas a bias tyre grows substantially, in this instance increasing the distance between the skirts and ground and letting air bleed, drastically reducing down force.

Goodyear were forced to try and develop radial race tyres to compete with the French manufacturer, and Michelin dominated F1 for the next couple of years.

I killed two LT BFG's last summer and replaced them with some P carcass michelins the tyre shop had going cheap.

The difference in ride is amazing, even with the same 40psi in them the P casing is a much softer ride. But the michelins rounded shoulders are death on gravel roads, they follow ruts that the square shouldered BFG AT's climb out of.

The sidewalls on the BFG's are at least twice as thick, I'd expect airing down in soft sand and the like you could heat up and wear out a BFG sidewall faster than a thinner P casing. But the michelin feels thin enough to push a ballpoint pen through.