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Tyres: Old before their time?

It isn’t just wear that destines a tyre for the scrap heap. Age, use, environmental exposure and storage can severely affect a tyre’s performance. Here are a few things to think about.

It isn’t just wear that destines a tyre for the scrap heap. Age, use, environmental exposure and storage can severely affect a tyre’s performance. Here are a few things to think about.

The UK is enjoying (or enduring, depending on your viewpoint) its hottest summer in over 40 years. And I’ve just been riding in it. Not a massive amount, mind you, but it did provide an unexpected perspective on tyre performance in very hot weather.

I was fortunate enough to be given a BMW S 1000 XR to blat about on. The same ‘bike, in fact, as I rode last year.

But something was amiss. While the supersonic performance of the S 1000 RR-derived motor was as mind-scrambling as ever, the handling and grip were noticeable by their absence. What was going on?

When dry means slippery

With no rain for almost three months, the UK’s road surfaces had not been cleaned. At best this leads to a build-up of rubber, sometimes dusted with the sort of granules one sees ‘off-line’ at a race circuit. And, like a race circuit, this can provide plenty of grip on the rubber line. On road, though, with traffic criss-crossing on different paths, this is a rare occurrence.

More usual is something far less welcome. Oil, diesel, dirt and dust can bond and impregnate the surface of the tarmac. Without heavy rain to clean it out, the result is a slippery mess. It’s especially noticeable on the sort of large, fast roundabouts common in the UK and which bikers usually enjoy. Not this time, however. I experienced several slides, even without troubling the far edge of the tyre and with no more than gentle application of power.

So common was this, it raised another issue: Traction Control. It’s not that fast-acting, is it? Invariably, I had rolled off the gas before the Bosch brain has decided to do anything about it. I guess that’s another story.

Perhaps even more troubling than regular rear-wheel slides was what was occurring up front. Which was nothing: i.e. nothing in the way of communication, feel or discernible grip.

It would have been easy to shrug and blame all this on the diesel-slicked roundabouts, but when things aren’t working properly or I’m not enjoying riding a motorcycle I tend to go all analytical about it. It’s the journo’s curse.

Tyred out?

Two things suggested blame could not all be sheeted home to what the exceptional summer had done to busy roads. First, the same vagueness and uncommunicative turn-in was happening on rural backroads. Then the penny finally dropped, when half of one roundabout was re-surfaced with pristine new tarmac overnight. Yes, there was more grip, but things still weren’t right. There was still no confidence. The front wasn’t talking.

Having already checked the tyre pressures and tried cycling though the Electronic Suspension Adjustment’s options, all fingers were now pointing at the tyres.

Less so the rear. On that pristine tarmac, a big handful of throttle did nothing other than dig the rear in and make the front go light. The rear tyre was relatively new. But the front was the original, dating from around the time the XR was built in late 2015/early 2016. And it had been subject to an unusual life.

Use and abuse

The XR’s owner, a lifelong friend, has an enviable collection of motorcycles. Sharing garage space with the BMW are immaculately restored classics including a B31 BSA, an A65, a Triumph Tiger T100, a Suzuki GT250, a B44 Victor scrambler, a friend’s RD350 LC and a Harley 1200 Breakout.

Recently, it’s the Harley and the B31 that get most use. In fact the XR had only been out three times since I rode it last year, otherwise stored in an unheated shed. And perhaps that’s where the problem lies. That, and the fact the front tyre saw a couple of track days in its early life.

Tyre manufacturers do offer advice on the ageing of tyres, and all modern hoops have a ‘birth’ date on them.

Picture of tyre showing manufactured date

The tyre pictured (not the XR’s) shows it was manufactured in week five (05) of 2016 (16). This coding was adopted by all the major manufacturers in 2000. Prior to that, different codings mean it’s a bit of a puzzle to work out the age. But if your tyres are pre-2000, bin them now or donate to a motor museum.

Common manufacturer advice is that your tyres are good for about five years from ‘birth’ then you should have them ‘professionally inspected’ annually up to age 10, when they’re officially past it. Presumably this would involve use of a durometer to measure hardness, because tyres that have ‘had it’ go hard, thereby reducing grip. And that’s what I reckon happened to the front hoop on the XR.

Heat cycles are usually what does for a tyre, if it doesn’t get worn out. But so can irregular heat cycles, like hitting track day temperatures, furring up at the edges, then standing unused for many months in temperatures that can reach freezing or even below.

Conclusion

Manufacturer recommendations are all very well. Actually, you could say they have an interest in persuading you to replace tyres earlier rather than later. But, in fact, their general advice that you should have no problems up to about five years comes with a heap of caveats. Here’s what Michelin say on the matter:

“It’s no easy task to predict the life span of tires, which does not depend on their production date but varies depending on numerous factors. A tire which hasn’t been used at all, or which has only been used lightly, can still be exposed to environmental conditions that reduce its life span. Several factors may affect their service life: weather conditions, storage and usage conditions, load, speed, tire pressure, upkeep, driving style, etc.”

The official motorcycle ‘Michelin Man’ dishes advice on tyre ageing.

Tyres are everything on a motorcycle. It goes beyond having sufficient grip. The feel you get from your tyres plays a huge part in your enjoyment, confidence and willingness to commit. When so many motorcycle accidents are caused not by riders exceeding the limits of what was physically possible, instead failing to get the maximum out of the machine, the conclusion is clear. If you suspect your tyres aren’t quite as good as they used to be, even if they’re just a few years old, you’re probably right. And a new set of rubber could be the best investment you’ll ever make.