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Steels, Mags, Alloys and Radials
The stud pattern on all Morris Minors, post-51, are of the 4-stud/4-inch variety. That is, there are 4 wheel studs which are 4 inches, or 102mm, apart from each other. The early Minors, usually those with side-valve engines and bolts instead of wheel studs, have a stud hole pattern that is of the 4-stud/100mm variety. Unfortunately, for most of us, it is the early model sizing that has become the most common in modern vehicles. This means that you can fit mag wheels designed for modern Japanese vehicles on your pre-51 Minor but not on your Series II/1000 Minor. The early Morris Marina used the same stud pattern as the post-Series MM Minor, as did the Vauxhall Viva.
If you want to fit mag wheels to your Minor, and you are lucky enough to have an early Series MM model, then the choice of mag wheel style is huge! Modern, small Japanese cars that use 4 wheel studs seem to have settled on the 100mm sizing that the early Minors also use. The only point to be careful of is that most Japanese cars are front-wheel-drive and generally have a different offset to the wheel than is desirable for a rear-wheel-drive car such as the Minor. The offset is the distance between the surface that bolts to the brake drum/disc and the outer edge of the wheel itself. The offset for front-wheel-drive wheels is generally more towards the inside edge; that is, when bolted on the car, the inner edge of the wheel is further in towards the centre of the car than on rear-wheel-drive wheels.
When choosing a mag wheel for your Minor always try the wheel and tyre on the car before buying. The wheel and/or tyre is likely to foul on the suspension upright/kingpin in the front and on the inner wheel arch at the rear. You should ensure that there is at least 5mm, preferably 10mm, clearance between the wheel/tyre and the nearest non-rotating object when the wheel is properly fitted and sitting on the ground. It is possible to fit spacer plates to the outside of the brake drum but this is not generally advisable as it puts extra load on the wheel bearings and wheel studs.
As mentioned above, the Series MM Minor has a wheel stud pattern that is exactly the same as many modern Japanese cars and so the choice of wheels is made that much easier (or harder, depending on your point of view!).
Later model Minors have a bit of a problem. The standard Minor rims are not designed for modern tubeless tyres and therefore you should always
use inner tubes with your Minor rims. The late model Van rims are slightly wider than the sedan rims, but the rule still applies. Always fit inner tubes to radial tyres on standard Minor rims
If you want wider rubber on the ground than the standard rims will allow, but still want steel wheels, then your options are fairly limited without changing the stud pattern. The good old Vauxhall Viva comes to the rescue here. The Viva uses the same stud pattern as the post-Series MM Minors but with wheels that are up to 2 inches wider and an inch smaller in diameter! This means that a set of 185/60x13 tyres can be fitted quite comfortably.
But there's a downside - there always is. The Viva wheel has a smaller centre hole for the axle/hub cover plate. This means the Viva wheels can't be fitted immediately to the Minor. The centre hole needs to be widened by about 8mm in diameter, or 4mm around the circumference. The best and safest way to do this is to have an engineering shop do the job on a lathe. This ensures that the wheel remains balanced around the centre and means that the wheel can still be machine balanced using the centre hole as the locator.
The quick & dirty, and needless to say far less desirable, way of widening the centre hole is to scribe a line marking out the new size of the hole and drill a series of holes just inside the line all the way around the circumference of the hole. Then using a hacksaw or cutting file, cut your way around the hole until it is the right size. Make the hole as round as possible. This will make the balancing of the wheel a little less costly in lead wheel weights. Note that this method is not actually recommended, and in fact may be illegal in your country, but it does do the trick!
If the wheels or tyres you have chosen to fit to your Minor are touching on the inside wheel arch or on the front kingpin, wheel spacers can be fitted to give an extra bit of clearance. Do not use washers over the wheel studs as your wheel spacers. Washers allow far too much flex in the wheel under cornering loads and do not spread the loads evenly over the brake drum or bolting surface. This will result in handling problems and could lead to broken wheel studs and potential wheel collapse! Don't use washers on the studs as spacers!
The only acceptable spacer is a flat plate of the appropriate thickness, drilled to the exact same pattern as the wheel studs, where the drilled holes are exactly the same diameter as the wheel studs. This prevents the spacer from moving under the centrifugal force of the rotating wheel. Also, the spacer should preferably by perfectly circular and all of the stud holes drilled at an equal distance from the centre of the plate. If not circular, then ensure that the spacer plates are perfectly square. Any imbalance in the wheel spacer will directly affect the balance of the wheel and therefore will cause the wheel to start bouncing along the road. You should have the spacer plates cut and drilled professionally. This will ensure that they are cut accurately (if they're not you have some come-back too) and may in fact be a requirement by law in your country. Check out the rules & regulations carefully!
Depending on the thickness of the spacer required you may find that the wheel studs are now no longer long enough for the wheel nuts to have anything left to screw on to! The wheel nuts should screw on to the wheel studs by at least 20mm or 3/4". Any less than this and I recommend you fit longer wheel studs.
The standard Minor wheel studs are between 1 1/2" and 2" long. Mini Cooper wheel studs are 2 1/2" to 3" long and can be fitted directly into the Minor housings. In New Zealand, these wheel studs are becoming quite expensive at almost NZ$10.00 each (approx US$7.50).
Using Mini Cooper wheel studs will fix the problem of running out of screw thread, but there is a note of caution here. The Mini studs have a longer 'shoulder' where there is no screw thread. If you want to return to using standard Minor wheels, or no longer require the use of spacers, then you may have to tap new screw thread into the shoulder of the new wheel studs. This is no easy job, especially as the wheel studs are made of tempered/hardened steel!
As described above, the standard Minor rims are not designed for modern tubeless tyres. You can fit tubeless tyres to Minor rims but you run the risk of the tyre peeling away from the rim under hard cornering, in which case if you have a tubeless tyre you'll have an instant flattie! This is not a Good Thing to have mid-corner!
The standard Minor rim usually takes a 5.20x14 inch cross ply tyre, but these are not only getting difficult and expensive to buy, but are not conducive to great handling! Swapping these for the equivalent-size radial tyre, a 155/70x14, will give your Minor a much better feel on the road; it will sit in corners much better (hiding the effect of worn shock absorbers!) and even provide a smoother ride. But a 155/70x14 tyre is pretty narrow for a Modified Minor!
Standard Minor rims can accept a maximum tyre size of 175x14, but this is an odd size in the non-metric world of tyres, so 165x14 is more common and keeps the rim within it's limits. Late model Van rims are slightly wider and can safely take a 185x14 tyre. Remember to always fit an inner tube to radial tyres - even to tubeless tyres.