When I bought The-Big-Red-One it came with tyres that looked pretty good. On closer inspection it turned out the date codes stamped on them suggested they were produced in 1991 and 93 or even 1981 and 83. As the bike was released from government service in 1986, and seems to have virtually had no use in the years since then, I reckon those tyres are from the ’80s. Now, I’ve got a 30 year-old daughter with her own kiddy and these tyres are older than her!
I made a search of the internet looking for advice on tyres for loopframe Guzzis. Originally the tyres were the same, front and back at 4.00 x 18. There aren’t many options for a 4inch front tyre these days. The Heidenau K36 at £117 a pair look good and in keeping with the bike’s style but the others are from makers I don’t know. I decided to go with a 4.00×18 rear tyre and to use a 100/90-18 on the front. This seems to be the standard thing to do. The 100/90 is almost exactly the same width as the 4 inch but a lower profile. It’s actually 9mm lower than the old tyre (If I were to put a metric sized tyre on the back I’d choose a 110/90 profile – slightly wider but the same overall diameter).
My options seemed to be;
- Bridgestone BT45. 4.00×18 64H and 100/90-18 56H for £135.
- Continental Go! 4.00×18 64H and 100/90-18 56H for £121.
- Dunlop Streetsmart. 4.00×18 64H and 100/90-18 56H for £138.
- Metzeler Lasertec. 4.00×18 64V and 100/90-18 56H for £162.
- Michelin Pilot Activ. 4.00×18 64H and 100/90-18 56H for £121.
I decided on the Michelins. They have good reviews and were reasonably priced, bearing in mind I would have to get tubes and pay for fitting. It would be too much to ask my dodgy wrist to cope with tyre changing. H-rated tyres are not strictly necessary. S-rated would be good enough but are not available from makers I trust.
I wouldn’t want to have to fix a rear wheel puncture at the side of the road on one of these. To do so you’d probably have to remove fairing, fuel tank and battery then lay the thing on its side to get the back wheel out. I had the luxury of a friends bike lift. I took the panniers and their frame off in one piece then put the bike on the jack with a sheet of thick ply accross the “prongs” of the lift to support the sump with a block of wood under the frame further back. It was very steady but I should have undone the axle nuts while it was still on the ground.
Removing the wheels is pretty straightforward and probably needs no description but you get one anyway!
First the back wheel. The right hand silencer needs to come off. I undid the clamps holding the silencer to the header pipe and to the crossover to the other silencer but, of course it wouldn’t come off without the left hand silencer being freed from its header as well. If I have to do this again I’ll just disconnect both silencers and remove them together with the crossover. The rear brake needs to be disconnected. The rod from the pedal (I have a left-side brake) is released by slackening the adjuster and then tied out of the way.
Then the nut holding the brake torque arm to the hub is undone and the nut and bolt at the other end loosened and the arm can come clear of the drum.
Now the axle can be released. There is a big 27mm nut to undo and, as I’ve hinted already, this would have been best undone while the bike was still on the ground. Once that is off undo the pinch bolt on the swing arm and pull out the axle while supporting the wheel.
The wheel along with the brake plate can then be pulled off the splines on the rear drive box.
Now for the front. The brake cable needs to be removed from the brake drum. I slackened off the adjuster at the wheel end as well as the one at the lever to do this. Then the cable can be moved out of the way.
There’s another 27mm nut on this axle to undo and then a clamp bolt at the bottom of each fork leg. Support the wheel and the axle will come out (and the cover plate from the right side of the wheel will drop on the floor with a clang!). The wheel with brake plate can then be lowered from between the fork legs.
I took the wheels round to “Gerwyn the Tyres” in the village and left them and the new rubber with him for the day. When I collected them, he described the trouble he had getting the old Pirelli Mandrake tyres off. They were so tight he was worried about damaging the rims and he ended up cutting the bead wires. The new tyres went on, no problem. It was just as well I hadn’t tried to do the job myself.
Next day, I checked the wheel bearings for smoothness then refitted the wheels. It was just the same procedure in reverse. Adjusting the brakes was easy as nothing was disturbed on the brake plates.
I might have to experiment a bit with tyre pressures. The riders handbook gives solo pressures of 21psi front and 25psi at the back. Back then, tyres had much heavier sidewalls than they do today. Current thinking is for 32psi front and 36psi rear. Some advocate even higher figures. It seems important to maintain the 4psi difference front to back and, as it happens, I used to run 30psi and 34psi in the V7Sport which is not as heavy.
I’ve ordered a luggage rack from TLM in The Netherlands. I might get a plate to fit a Givi box to it at some point.
I managed to get the bike onto its centre stand today by myself! The wife’s help was not needed! Clearly my wrist is improving although it’s still painful at times.
Should have taken a photo with the new tyres!