Radial v Cross-ply

Greetings. My first post.

I have in the garage a VF1000F2 almost ready for club registration (June 1985 build date) plus a donor bike. Apparently just 460 of these were imported into Australia so I figure they’re are very few remaining in roadworthy condition. Ok, so it’s tyre time and I’m going to ignite the long-standing (and unresolved) tyre debate on radials v cross-ply. There are several camps here: 1. those that believe you don’t muck with OEM chassis and suspension set-up and stick to cross-ply, but buy the most modern version you can (the new Dunlop StreetSmart are performing excellently on my GPZr 900). 2. Those that priortise authenticity over all other factors and would happily wear something with sub-standard (by 2015 standards) grip but must have that 1985 look. 3. Those that experiment with radials because they still think there’s life in the old girl (awesome motor!) and want to harass bikes 30 years younger in the corners. 4. Those that don’t give a s#%t.

This is my understanding thus far. I’m happy to be advised by anyone with knowledge and/or experience. The Bol D’Or rims will take 110/80 and 150/70. These tyres will however be ‘pinched’ and thus form a more triangular profile than the tyre manufacturer allowed for. They will also affect ride height and front/rear balance. The bike will now sit 2mm lower at the front and 7mm lower at the rear. Surely this must adversely affect ground clearance, but more worryingly rake the front end and make it slower to turn in (like a cruiser). To my mind the gains made through better grip by fitting these size radials would be negated by loss of ground clearance, slower tip-in, and altered geometry. Happy to hear people’s personal experiences.

Some initial research suggests the best solution is 110/80 and 140/80 in radial. This lowers the front by 2mm and leaves the rear unmolested. Tip-in should improve slightly. Only Avon seem to offer these sizes in radials. The new Storm 3D X-M on the front and the venerable A46 on the rear. I should mention that the latest cross-ply from Dunlop, the StreetSmart, grips well and is available in all the OEM sizes.

Finally there is the aspect of suspension. Radials provide far more ‘give’ than cross-ply. The suspension back in 1985 was set-up for cross-ply tyres with their near-rigid sidewalls. I imagine fitting radials would require some stiffening of the already soft suspension. Happy to receive feedback. Thanks in advance.

Ideally you would be better with a 4.00" rim for the 150/70 but it will fit on the standard rim.
Pekka in Finland is running this and 110/80 on the front in radials with no problems.
The slight pinching of the rear tyre helps to negate the loss in rolling radius due to the change in profile and in my own experience only caused a problem when using metzler or Pirelli tyres which already have a triangular profile.
Bridgestone’s Avon’s and Dunlop’s all have a flatter profile to start with.
No real negatives on the suspension or steering fronts plus longer tyre life plus better grip from modern compounds on the plus side.
Regards Bif

Thanks for the insight and sharing of your experience. I have now decided on Pirelli Angel GT. According to Pirelli they have a lower curvature and flatter centre compared to the outgoing Angel ST, so hopefully this will negate the ‘falling into corners’ effect caused by squeezing the tyre at the bead/rim. http://www.motorcycle-usa.com/402/16139/Motorcycle-Article/Pirelli-Angel-GT-Tire-Review.aspx
I’ll post my review once I’ve covered some distance on them.