Monster Truck Tyres
Whenever somebody first sets eyes on a Monster Truck or vehicle of similar gargantuan proportions the first thing to be commented on are the four 60” high tyres propping the truck up. Despite the trucks paintwork, chassis or custom build its normally the tyres which instantly steal the lime light.
The reason for this is that they are as impressive as they are ludicrous. They are built for a job which they perform without equal while at the same time, being highly impractical. And so once again they steal the show in this article which we dedicate to the largest and most cumbersome and in our opinion, most visually impressive of all tyres.
So firstly, a bit about the tyres that so easily draw a crowds gaze. Full size monster trucks generally use an agricultural style of tyre knows as floatation tyres. They were originally designed to be used on large and heavy farm machinery and so their abnormal size was designed to spread the weight of the vehicle over a large footprint in order to reduce compaction. And so with a huge footprint and a large air chamber the tyres are well equipped to carry heavy loads at relatively low pressures.
The flat stable tread spreads the load evenly across the footprint in order to maximise floatation and therefore, minimising ground compaction. This means that the driver of whichever vehicle is large enough to need these oversized tyres, will be in relative comfort and stability thanks to a combination of low pressures and extremely flexible side walls.
So the tyres, already outfitted to carry heavy loads, were the obvious choice to adorn a Monster Truck and quickly became an integral part of its make-up. But apart from the desired, outrageously large, appearance the tyres were actually over specced for the job. Each tyre can carry over 9 ½ tons but your average Monster Truck weighs less than 8 tons.
In Monster Truck racing and competitions keeping the weight to a minimum is, of course, a concern. To maintain height when jumping and to keep the truck moving as fast as possible the tyres are often modified to suit the specific needs of the event. Drivers will often shave 1 ¼ inches off of each tyre reducing the weight by up to 160lbs. With each tyre and wheel combo weighing the better part of 1100lbs each, this can make for some interesting handling characteristics.
This means the bulk of the weight is what is called un-sprung weight and with a large amount of the weight below the suspension, the steering will be heavily influenced by the terrain and the truck will have a tendency to bounce over bumps rather than the springs and shocks absorbing them.
Having all this low down weight in each corner does have an advantage though. When it comes to jumping, the extreme width between the wheels and low down ballast provide some of the much needed stability required to keep the truck upright. A necessary feature which doesn’t always manage to do its job flawlessly. Several companies manufacture these tyres which service the larger vehicles so well. Of these companies are some of the well known brands such as Michelin, Firestone, Goodyear and Dneproshina. Certainly most of the trucks you will find in Europe will be sporting tyres made from one of these companies. But you would be hard pushed to buy one of these tyres with your pocket money as, depending on make, they can be anything from £1,755 to £3,315.
And so, its easy to see why the tyre is such an important feature of a Monster Truck, both aesthetically and practically. Below are some general stats of the tyres for ease of reference.
Written by Tim McKay & Alex Eichner (www.leisurepursuits.co.uk)
Manufactures: Michelin/ Firestone /Goodyear /Dneproshina
Overall Diameter (In): 64.8
Overall width (in): 39.6
Rim Width (in): 36
Loaded Radius (in): 28.4
Centreline tread depth: 58/32nd
Rolling circumference (in): 194.2
Tyre weight (lbs): 782
REV per Mile: 326
100% tyre volume (gal): 368
Min running pressure (psi): 14
Max Pressure (psi): 41
Max load per tyre @ 25mph @ 35psi (lbs): 13,860 (6.2 ton)
Max load per tyre @ 5mph @ 35psi (lbs): 20,840 (9.5 ton)
Price: Depending on make £1,755 to £3,315