Pirelli sport demon fault

Just taken wheels off to have new tyres fitted as I’ve had enough of the sport demons, never liked them from new. Front wheel would lock on heavy breaking and mid corner the front would start to slide out as if you’d hit diesel or water, awful! When I removed the front I found a 10mm deep split across the tyre.
Not what I’d expect from a tyre that is only been on bike 14 months and done 3k miles. Would not recommend these to anybody, let’s hope the bridgestones are better.


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The tire looks like it has reached is end of life. Not much profile left.

I will have to replace the 6 year old Lasertec on my VFR. Only found these combinations:

Bridgestone BT 45 F/R
Pirelli Sport Demon Front / Rear
Dunlop Arrowmax GT 601 Front / Streetsmart
Heidenau K 65 / K 64
Metzeler Lasertec Front / Rear

Guess I will go for BT45.

Had the bridgestones fitted and tyre fitting place said front sport demon had delaminated and the rubber had come away from the carcass causing it to move and split, something they said should never happen on a road tyre but is seen on slicks. I certainly don’t ride that hard! Hopefully the BT45 front will feel a bit nicer, the sport demon rear felt fine.

The limited choice of tyres in general and the lack of any radials in particular prompted my move to 17 inch wheels.
There seems to be little or no development on crossplys,Metzler being the only company to produce anything new with the K-1 but the sizes are restricted with only the rear 140/80 of use to us.
I have seen 17 inch fronts built for the R using spokes and rim from an NS400R rear wheel,but the rim is too narrow to be of any real use.
Keeping a look out for a set of Astralite wheels after a rather disappointing foray into magnesium alloys.
Regards Bif

You’ll be more than satisfied with the BT45. The Dunlop Streetsmart is also a great choice for older bikes. I’ve used both of these tyres on the road and at track days on various 80s bikes. Also Metzeler has the Roadtec 01 in both radial and cross-ply. Ok only the cross-ply option is available for older bikes, but the rear is a bi-compound and grips well.

Looking at those pictures, it looks like a classic case of interply shear failure.

Road tyres for cars and bikes are made from synthetic rubber. This is how the various “compounds” can be produced.

Some manufacturers use the low sulphur vulcanising process, which is environmentally impeccable but bad news for any other consideration.

When a tyre is on load, the rolling radius at the bottom is smaller than at the top. As the wheel has a constant angular velocity, the linear velocity is therefore variable. The bit in contact with the road is going slower than the rest of the tyre, so the front of the contact area is being compressed, and the back of it is being stretched.

Now add the shear force of it being cranked over into the mix and you have a small portion of the tyre carcass trying to withstand four conflicting forces.

Low sulphur vulcanising reduces the moulding pressure and temperature, which reduces inter ply cohesion and inter ply shear stress tolerance, so eventually the combination of compression, tension, shear and tortion experienced in normal operation results in ply separation if any one of the forces exceeds design limitation.

That is what’s happening here.

The best thing to do is to avoid tyres that are manufactured using the low sulphur process.

To that end, Bridgestone, Dunlop, Michelin, Metzeler and Conti are your best bet.

I knew those Michelin tyre conferences would come in handy one day…


Thanks Chris, I for one will never buy another sport demon. The Bridgestone I am using now is much better, not had a single moment or twitch from it.