The lost art of tire truing

Editor’s note: This article was originally published on April 24, 2018

Most tire shops these days attack your car as if they were auditioning for a NASCAR pit crew. “Time is money” in the automotive repair world. Mounting and balancing tires has become a “dirty” job often given to entry-level workers, guys who are eager to complete the task as quickly as possible and return to their smartphones.

We take for granted the scant contact patch which glues us and our metal cages to the tarmac at ever-dizzying speeds. While tire and wheel technology has greatly improved over the years, some of those gains are negated by indifferent installation; we just aren’t placing a value on the skills needed to do it with precision.

It wasn’t always this way. In the past, balancing a tire required tools and techniques that have gone away with reliance on computerized spin balancers. Nowadays, wobbly wheels are simply loaded up with lead weights to offset the imbalance. This relieves the symptoms, but it’s not the cure. Your tire can still be mounted way out of whack because no tire or rim is perfectly round.

With the road feel of older cars, these flaws get magnified. So, you’ll understand why I chose to go old school when mounting tires to my 1974 Maserati Bora, a supercar that (if singer Joe Walsh is to be believed) “does one-eighty-five.”

The Bora rides on Michelin XWX tires developed especially for the 1960s-70s era of high-speed European supercars, such as the Ferrari 365, DeTomaso Pantera and Lamborghini Miura. In period, they carried a maximum speed rating of 186 mph, giving some measure of comfort to guys like Joe Walsh.

For such collectable cars, having the correct type and profile of tire is critical to their operation and value. For these cars, Coker Tire in Tennessee offers reproduction Michelin XWX tires with a slightly more-sober speed rating of 168 mph. These are well-built, rugged and expensive tires – but like everything else in the world, they are not necessarily perfect.

Which brings us to the lost art of tire truing. Finding a shop that still has a tire lathe won’t be easy, let alone an operator with the skill to use it. Once employed everywhere in the industry, most truing machines are now gathering dust in back rooms. Serious racing shops and semi-truck tire-repair facilities are your best bet, as the efficiencies gained in truing are still valued there.

I’d read on a hot-rod message board about a shop an hour north of Chicago still practicing this arcane art. O’Brien Tire Sales in Mount Pleasant, Wisconsin, is a mom-and-pop tire store that’s been around since 1967. Sadly, founder Al O’Brien passed away at age 75 just a few months after celebrating the shop’s 50th anniversary, but son Mark O’Brien and employee Rich Clausen carry on the tradition of bespoke tire service. They systematically true every new tire they install.

Mark started working with his dad at 16 and moves deftly around the tidy shop. Upon breaking the heavy bead on the old tires, we run into evidence of the bane of tire guys everywhere: Fix-A-Flat. The gooey substance makes it difficult to mount and dismount tires without binding or leaking, so it must be cleaned off with a wire-wheel before proceeding.

After replacing the valve stems and checking the sidewall for any orientation instructions, liberal amounts of tire mounting lubricant are used and the new tire slips on easily. This is important because if the tire grabs and produces a cinched spot, Mark will have to break the bead to rotate and reseat the tire for best results.

We check the runout on the truing machine, and indeed one tire is found to have more lateral runout than can be corrected by shaving. Mark finds the high spot on the tire, pops the bead and rotates it 180 degrees, returning it to the machine and thus curing the problem. This step alone is something unlikely to occur in most tire shops today.

Now we are ready to shave the tire. The wheel is mounted in a jig specific to the Maserati’s bolt pattern and not the center hole of the rim, which is not true-center. Mark positions the lathe’s cutting wheel, which moves on an arbor in three planes against the tread as the machine spins the wheel with a roller.

The object is not to flatten the face of the tire, but to lightly shave off slight high spots within the existing curved profile. O’Brien checks his work with a profile gauge, but only years of hands-on experience can produce the desired results.

The material removed is between 1/64 – 1/128^th of an inch thick, and the amount of shavings from one tire fills the palm of my hand. They’re as light as feathers. Still, looking over the cusp of the spinning tire, the slight wobble is now gone. Only now that we have acquired a truly round tire are we ready for the finishing touches on the computerized spin balancer.

Mark explained that the process is best utilized on new tires that have not had a heat cycle or been used on the road. “We could true used tires, but we’d have to spend so much time cleaning every little rock out of the tread so it doesn’t damage our cutting blade. We also need the tires to be at operating temperature so they are elastic and as round as they can be, not cold with a flat spot from sitting.”

Mark was impressed with the quality of the Michelin XWX reproductions from Coker Tire.

“Normally, you see more imperfections on brand-new tires. These were exceptional,” O’Brien said. “My dad Al used to say this about truing tires: ‘It’s meant to make good tires great, not bad tires good’.”

For my sports car, the inexpensive step of properly mounting and balancing my tires certainly took me from feeling good to feeling great. As far as doing “one-eighty-five” with my new tires…well my friends, I’ll never tell.