Simple tyre fitting
Old hands might well laugh at this, but it’s surprising how many enthusiasts have a problem with this simple task and/or fail to understand the concepts behind it; so here’s a pocket guide…
A simple task that often confuses
Traditional scooters have split wheel rims to make the task of tyre fitting and removal relatively easy. Not all wheel rims are the same; the examples shown in the accompanying pictures are from the vintage Vespa GS160/SS180 and split symmetrically in half, as do the Lambrettadesigned type. Most Vespa rims split in a two-thirds/one-third manner.
TUBES AND VALVES
It's important to note that there are a few rules with respect to inner tubes that should be kept in mind on the simple grounds that your life could depend on them.
There are two types of 10-inch inner tubes that are meant for either the Lambretta or Vespa: 1: The Lambretta tube – this has the brass tubular air valve with an approximate 30-degree bend (pic 1).
2: The Vespa tube – this has a 90-degree bend in the valve tube (as shown in the tyre fitting details).
The two designs are very similar, but are fitted slightly differently. The Lambretta-type valve, when correctly fitted, points outward from the centre of the fully assembled rim halves and tyre assembly. The Vespa type (and the reason for the long, right-angled valve) passes across the inside edge of the rim flanges when assembled. Obviously, either type of tube can be fitted to either make, but doing so will prove to be either awkward, as in the Vespa case, or downright dangerous in the case of the Lambretta.
The awkward point is simple to explain – if you happen to fit the Lambretta tube to a Vespa, the valve sticks out as per the Lambretta scenario already mentioned. Not the end of the world, you might say, but when the rim is bolted on to the hub, it will be found to be difficult to fit an air hose adapter to the valve because of its more upright angle and its close proximity to the hub.
A Vespa type tube, when fitted to the Lambretta rim, again will go on okay… BUT – and it's a big BUT! – the right-angled valve stem sits somewhat clumsily poking out from the side of the Lambretta rim and although the assembled wheel can be fitted safely to the back wheel hub of a Lambretta – that is NOT the problem. However, if you are daft enough to fit the same rim to the front hub, the long right-angled valve – on rotation of the wheel – will come very close to the head of the large bolt that forms the pivot for the front suspension trailing link. At this point you might conclude: “Well if it misses – it misses – what's the problem?” (A reasonable conclusion, to be honest). That is, until you consider that just spinning the front wheel cannot replicate the movement of the suspension when on the road. Remember the twin forks of the Lambretta are not linked and are independently sprung. The wheel assembly, as it negotiates road bumps, also moves from left to right, as well as just rotating. It's almost inevitable that this long valve stem will inevitably knock against the suspension pivot bolt and, if this continues over a few miles of riding, the valve stem base adjacent to the tube will be forced to move against the cut-out in the steel rim for the valve stem, until it finally breaches the tube air chamber at this interface. The tyre will deflate very quickly in these circumstances. A front wheel puncture at any speed has to be experienced, as has hospital food!
Another rule often ignored is the reuse of old tubes inside new tyres. Many do this, but it's risky when you consider that your life might well depend on this item. Best to buy a new tyre and tube as a set.
TYRE FITTING (AT LAST!)
Simple when you know how…
All you need are the items shown in the main opening picture, plus a foot pump. The socket is either a 1mm or a 13mm depending on nut size (scooters pre-dating the mid-1960s had as original fitments 14mm M8 nuts). Standard scooter tyres for largeframe models are usually 3.50 x 10-inch tyres. More about the ‘magic ingredient', talcum powder, later.
Inflate the tube so it just forms a soft doughnut shape (pic 2). Liberally sprinkle talc inside the tube, rubbing it into the tyre bead as you go. Push the loosely inflated tube into the tyre, noting the valve direction from the points mentioned on the previous page. Pull the tube around the inside of the tyre to allow the talc to cover all surfaces (pic 3).
Using the rim half with the valve stem cutout, insert the valve and place the inside of the rim against the tyre bead (pic 4); doublecheck the valve is facing the correct way. You can now rest the loose rim on a flat surface, reach inside the tyre and push the bead with thumb pressure on to the rim half. The talc helps here as it's a lubricant.
Now, placing the remaining half of the rim so both the rim studs and the adjacent holes of the adjacent rim half line up, press the rim halves together. Try to line up the stud nearest the valve stem first and then run a nut on to the thread for a couple of turns. Press the next nearest stud into place and run a nut on to this in turn, working your way around the rim halves until all the nuts are loosely positioned (pic 5).
This is where the fact that the tube was partially inflated comes into play. Not doing this renders the tube liable to be pinched by the rim halves, if left flat when the nuts are fully tightened – again the talc allows the tube to slip into place inside the rim when the tube is finally inflated (pic 6).
The above description is for when you're lucky and hand pressure alone can force the rim halves together. On occasions, maybe only the first two nuts can be easily fitted. This is not a problem, as more air can now be slowly pumped into the tube, being careful not to over-inflate to the extent that the tube balloons through the gap between the rim halves. This added air pressure, alongside the lubrication from the talc, will force the tyre further on to both rim halves until all the rim studs slide into their locating positions and the nuts can be run on to the studs one by one, as above.
For those very safety-conscious folk who might be worried that the tube might be rucked up inside the tyre air chamber (and to guarantee that this has not happened) the tube should now be deflated and finally pumped back up to the desired air pressure.
Job done!
AFTERTHOUGHT…
Tyres having ‘slick' or ‘semi-slick' tread patterns must be fitted to the rims to match the direction arrows on the side walls. The valves must obviously also be fitted in a manner to suit this direction of rotation.