Once upon a time tyres were black things that stopped the sparks, and the screeching, and the weird upright on-rails cornering. They made the bike a bit taller too, but "grip" was ultimately not as important as longevity. Longevity as in, "I found this Excelsior thing in the barn and restored it, but I didn't have to replace the lovely white wall tyres. Look! No cracks in the side wall."
They weren't made from a "compound" as such, more like string, two metal hoops, some canvas, and as much of that stuff that oozed out of trees in Malaya that you could get to stick to the canvas stuff that criss-crossed in several layers to give truth to the "cross ply" description. "Angry almost-bonded layers" is probably a better description, and the negative karma generated by these primitive pneumatic rim covers used to attract every mono-filament edged piece of rubbish laying about on the road surface. Punctures. Remember when you used to have to fix your push bike tyres once a week? Or motorcycle tyres that would somehow grow an eight inch nail two miles into a week off, touring the "district"? It was Cross-ply negative karma wot did that.
I made a feeble attempt at racing in the late '80s/early '90s. Radial tyre technology was just making its way onto the street, but for 400cc machines you were stuck with cross-ply tyres with all that entailed. Suspension was designed with the greater amount of give inherent in cross-ply sidewalls in mind, and a lot of you guys with late '80s 250s and 400s are probably giving your kidneys an avoidable pounding if you've fitted radial tyres. For racing on a budget there was really only the Metzeler Comp K Me33/ME1 combo, or Michelin A38/M49s if you were unlucky enough to have an 18" rear wheel. It's difficult to describe it, but these tyres would feel great right up until the middle of a 10 lap race at Manfield and then would go "soft" on you. The suspension would feel like all the settings had been wound up to full compression, or the preload had been maxed, but the tyre carcass would flex and make the bike wallow. You couldn't brake as late, and couldn't get on the gas as early, and all the rich bastards on slicks (Avons or Michelins) would just vanish into the middle distance. Two races in one.
Then Yokohama and Pirelli gave us radial tyres. The Yokohamas were my favourite, with 003, 005, and 007s, all different compunds and tread patterns, with the 003s a near slick, like Dunlops D218s today. Wow did they tie the skinny 37-38mm forks in knots, and you couldn't get enough rebound damping. Shocks would overheat, brake fluid would boil because you could finally use ALL the brakes, and bikes would shimmy all the way out of corners.
Fast forward 15 years and "Sport Touring" cross ply tyres have the same near vertical parabolic profile as slicks from 1990, their side walls are half the height the used to be, and they feel like modern radial tyres. I can't believe how much difference the Pirellis have made to the CB400. The Bridgstone BT39s that were on it, were contemporary with the tyres of 15 years ago, and with the rear squared off and down to the wear bumps, they were definitely past their prime. I hate the weird feeling you get, like rake and trail figures are changing as you roll up over the "edge" on a squared off tyre. The bike goes from neutral and stable, to cruiser, and then to sport bike quick, all while you negotiate the arc of one corner.
All I've done is ride home on the motorway and then a couple of laps of Maungaraki and Korokoro to get the release agent off, but wow! I just about ended up on the footpath when I turned into Korokoro at the Petone lights, and all the corners up Korokoro that had peculiar little challenges can be negotiated on a precise line, despite shagged rear suspension. I'll post some updates on how they go as I scrub them in more, and maybe give them a bit of "urge" (not to Velox levels though - I'm not that mad). The tread depth is of a similar "wow I dropped my keys and they fell in my tyres and I can't get them out" as Avon's sport touring tyres too, so I imagine they'll last well too.
As you can tell though I've bonded. I'm stunned at how far tyres for smaller bikes and commuters have come. These things would have been class winning tyres in F3 15 years ago.
http://www.pirelli-moto.com/en_96/ti...me=SPORT_DEMON
Tyre sizes I've fitted are 110/70x17 Front, and 140/17x17 Rear. Price was about $350 for the set.
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Originally Posted by Jim2
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