Why is there a ridge on my dual-compound tyre?

Q. I have a Suzuki GSX-R1000 K8 running Dunlop Roadsmarts, getting 5500 miles out of the rear with too much commuting and motorway work.

• Save cash on motorcycle tyres

There’s 2.8mm tread depth left at the centre with about 4.5mm at the edge of the harder strip, but there are two ridges running around the tyre that look like they are where the tyre compound changes.

These tyres are my first dual compound rubber and are a brilliant combination of a great carcass, superb feel and confidence in the cold and wet, and long life.

But they have been squirmy for a while too, maybe the ridges make it even worse around slime, slush, groove tarmac and white lines?

Is ridge development exacerbated by riding style (eg. accelerating at slight lean with both compounds in contact) and is there a way to prevent it?
Bbstrikesagain, MCN tyre forum
 
A. Although the border between tread compounds seems a likely reason for the ridges, tyre pressures can have an effect.

If you’re not running them at 36psi front/41psi rear they can overheat which will affect the wear rates.

The tyres are getting close to the end of their lives, so you’d struggle to get them replaced, but if you return them to the supplier they should send them back up the line to Dunlop for analysis and you’d get a report on their findings after they’d given them a thorough examination.

Other tyre firms offer the same inspection service.