CALL SECURITY!
Paul Basset is fitting Heidenau 67 tyres, like I’ve used on the project Triumph, to his 1967 BSA Victor Special wheels (with original chrome rims). There are holes for one security bolt on the front and two on the rear, but he asks if, since he’s not planning to use the bike off-road at low pressures, I think he can do without fitting them. He’s found that tyre fitters sometimes have trouble pinching the tubes with the bolts fitted.
I fitted security bolts to the 3T because powder coating left the inside of the wheel rims very smooth, filling the serrations inside the bead that give some grip for the tyre. The security bolts should prevent the tyre creeping on the rim, stretching the inner tube until the valve tears free, causing an instant flat – a ‘blowout’. The pressure of an inflated inner tube is normally enough to grip the tyre firmly against the serrations on the rim – but on competition bikes, where pressures are lowered to increase tyre contact area for grip, you can get slip even so. Grasstrack and speedway bikes, subject to violent acceleration, often have a hole drilled in the tyre sidewall for the valve; then, if the tyre shifts, it takes the tube and valve along with it – but that’s not suitable for all situations.
Paul decided to compromise for road use, fitting just one bolt to the rear and none on the front. I’d block the rim holes with grommets if possible, to prevent the tube/ rim tape chafing against the hole. Finally, while fitting tyres with security bolts is tricky, the key thing is to ensure the bolt is pressed fully up into the tyre while fitting, unscrew the nut to the end of the thread. ISDT riders could fix punctures in minutes, so it’s more a knack than anything.