What Factors Should Drive My Choice Of Drive Tyres?
What's the secret to long drive tyre life?
Part of it is selecting the right tyre for your drive axles. Notice, we didnâ€™t say â€œselecting the right drive tyreâ€. Because sometimes the right tyre for your drives isnâ€™t a â€œdriveâ€ tyre at all.
Why is that?
Most drive tyres are designed to provide traction, so that the torque of the engine can be transferred to the road. Youâ€™re taking upwards of 40 tons of vehicle at rest, and trying to get it into motion.
Sometimes, those aggressive lugs and blocks that characterise most drive tyres may be unnecessary.
How can that be?
For best traction and torque transfer, Indy and some other racing cars use â€œslicks.â€ The road surface has to be hard and dry, and slicks maximise the amount of rubber in contact with the road â€“ and the traction that results.
Dry traction is a function of the amount of contact between tyre and road. â€œSlicksâ€ actually produce the highest possible traction on clean, dry road surfaces.
So why does everybody use aggressive lug and block patterns?
Actually, not everybody does. Some fleets have run rib radials in drive positions, very successfully.
Why use rib radials on drives?
In some operations, such as some local delivery and bus operations, on a highway type surface, rib radials can be an excellent choice for drive axles. Even on wet roads, the traction can be superb. And typically, rib radials have shallower tread depths than lug or block patterns. Thereâ€™s less tyre weight to put into motion. In addition, contact with the road is more or less continuous throughout the tread face. That means less noise and vibration. And generally, there is a reduced tendency for irregular wear, especially of the â€œheel and toeâ€ variety.
For some fleets, ribs are just more practical. Especially if they can standardise on a single size and pattern for all axle positions. That can greatly reduce tyre inventory.
Finally, rib radials usually have far less rolling resistance than drive radials. That can mean superior fuel economy.
Will any rib radial work?
Not necessarily. Youâ€™ll want to test it, on your own vehicles and over your own routes, before making a commitment to rib radials on drive axle positions.
Remember that, unlike steer and trailer positions, tyres on drives are subjected to very high torque. That can cause tyres to wear rapidly.
In addition, youâ€™ll also want to consider the fact that many drivers donâ€™t believe rib radials will give them the traction they want.
On good road surfaces, rib radials provide powerful traction and fight irregular wear, while effectively cutting through water and films
What kind of irregular wear occurs on drive tyres?
Pretty much any kind, but one of the most troublesome is â€œheel and toeâ€ wear. As the name implies, individual tread blocks are worn unevenly, with more wear on the â€œtoeâ€ of the block (the last part to leave the road as the tyre turns) than on the â€œheelâ€.
This wear is caused by slipping and â€œsnappingâ€ of the toe of the block edge as it loses contact with the road.
Tread blocks can develop excessive wear on the edge that touches the road last. Called â€œheel and toeâ€ wear, changing the direction of tyre rotation can sometimes counteract these patterns.
What can we do about that?
If heel and toe wear is the only irregular wear you have, cross-rotating your drive tyres, to reverse their direction of rotation, can help equalize wear patterns by transferring wear forces to the other side of the blocks. Nevertheless, youâ€™ve added a lot of extra tyre handling. (If youâ€™re experiencing alternate shoulder lug wear on open-shoulder drive radials it may be due to a mismatch of inflation pressure in dual assemblies).
You can also switch to a shallower tread drive radial with shorter blocks that squirm less. But, you must sacrifice original tread â€“ and mileage â€“ to combat the irregular wear.
Cross-rotation of drive tyres can help scrub out heel and toe wear patterns. It also can help equalize wear if the tyres on one tandem wear faster than those on the other