Wheels

Width

Very early Imps had 3½" section wheels.
The standard rim is 4½"J x 12", used with a 155/82/12 tyre.
The 'J' simply refers to the shape of the rim's edge.

Imps work well on wider rims (and tyres) on the rear. Too wide is not good for an Imp, due to camber changes in the suspension.
Front:
• Recommended: 5½x13 (with 175/60x13 tyres)
• Possible: 6x13
Rear:
• Recommended: 6x13 on the rear (with 175/60x13 tyres).
• Possible: 7x13 at the back (with 185/60) is useable, but they are a little wide... perhaps a bit less offset.

From 4½ to 5 is an increase of 9.0%; to 5½ is an increase of 22.2%; to 6 is an increase of 33.3%.

Imp tuning & modification by J.D. Hansen: Wheel width is restricted to 5½" at the front and 7" at the rear by the space available. And there is no point in exceeding 5½" all round on a road car.

Tuning Imps by Willy Griffiths: You can fit wider rims without needing spacers and I do not recommend them. The best tyres can be fitted to 6  maximum section rims.
For racing, use equal rim widths and equal tyre sizes front and rear.

Rims ought to be just one piece and not the standard rim with a piece let in. Sawing a wheel in half to let in extra bits should only be attempted by a specialist.

With 5x13 wheels (like Panasport alloys) the front hubs are a fit problem, because the center cap does not fit onto the wheel after installed. The back hubs appear to be fine.

Has been done:
If you want to use steel rims from a metric car, chose some with the most favourable inside offset. (Perhaps the 5Jx13 of a nineties Opel Kadett). Then take them to an engineer to have them made fit for an Imp. He will completely remove the centre boss of the wheel (centre hub hole and wheel stud holes) and throw it away. Even the nearest metric size can't be made to fit.
Then a steel disc is prepared in a slightly lareger circle than the hole in the wheel (¾" / 18mm thick). The correct PCD centres and the centre boss hole (2 3/8" / 60mm) are drilled.
The edge of this disc gets rebated to form a seat the size of the hole in the rim. Then the rim and the newly made disc are welded together. If the disc is offered up from the inside of the rim, the rear offset will differ about ¾" / 18mm from the standard.
If you don't like the offset, the rim hubwelds might be removed on a lathe, repositioned and rewelded.
The stud holes will require a taper to suit your wheel nuts.

A lot of wheel achieve most of the width from the hubface outwards. An Imp needs a wheel with quite a bit of inset. Wheels suitable for front-wheel-drive cars are often suitable for the Imp, but you'll have to find a manuafturer who is willing to drill a blank casting for a 4" PCD and 7/16" UNF bolts/nuts.

Racers have a greater proportion of the weight on the rear than a road car. They used to run 8 inch on the front 10 on the rear.

Diameter

A topic that concerns rallying or racing Imps is whether the Imp ever had 13" wheels homologated. Competition Imps that run in the roadgoing class have to stick to what has been homologated. Using 12" wheels restricts the width of tyre that can be use, and anyway the choice in 12" tyres is getting more and more limited.
The homologation paper for 13" wheels on Imps is dated 1st January 1967 and the FIA recognition number was 526.

Secondhand

Powdercoating
In stead of buying new wheels, you could have a set of secondhand ones powder coated. The coating fills-in any pitting/scratches etc. Anything to be powdercoated must be clean to bare metal for the process to hold and work well long term. This can be either by fine sandblasting or some other type of media blasting.
First check carefully for

• eccentricity (incurable!). Eccentric wheels loose their balancing after short mileage.
• runout (can be sorted with the right facilities...)
• cracks, especially in the well where they let air out.

Magnesium
Magnesium deteriorates with age and becomes very susceptable to stress cracks or things like that. So be careful when you trade for old Minilites and such.

Minilites

Minilites

A 5x12" Minilite weighs 8 lbs

• Minilite style wheels, called 'Contesta' were made in Australia during the 70s by ROH - the spokes are a little shorter and the centre a little larger than the real thing. They were, in the 10" version, used on the Mini SS and LS models of the mid 70's - which made them kind of official. They are also commonly seen on Escorts in 13" and, yes, on Paul Ewins' Bolwell in a 12x5".
• A better replica is called 'Superlite', manufactured originally by Revolution in Australia.
  Now [info courtesy of Ian Scott] by Performance Wheels, retail price [October 2005] for set of 4 13" x 5.5J is 650 $ Aus is 230 £ UK.