Wheels and Tyres...

Such a subjective topic...what to fit, what looks best, what handles best?

The idea of this page is to show the standard rims and tyre sizes, and link through to upgrade or alternative rim sizes, but definitely not to offer the definitive answer - the choice is very subjective, especially where tyres are concerned!

Firstly a few FAQ:

Rim details: 

MGB/BGT - 

• Rim
• Rim Width = Steel 5J/ Wire (60 spokes) 4.5J
• Pitch Circle Diameter = 4-stud 4.5" (114.3mm) (Steel wheels)
• Offset = 22mm approximately.

MGB GT V8 -

As per B/BGT but using a steel/alloy structure Dunlop rim.

MGC (and optional on B/BGT) - 

• Rim Diameter = 15"
• Rim Width = 5J
• Pitch Circle Diameter = 4.5" (114.3mm)
• Offset = 22mm approximately.

Tyre details:

MGB/BGT - 

Original fit: 

Radial or earlier, Cross-ply 165 14 (usually implies an 80% tyre wall height) which gives a rolling diametre of 620mm (24.39")

Alternative fit: 

• Radial 175/75 14 which gives a rolling diametre of 618mm (24.33") or a reduction in diameter of 0.32%
• Radial 185/70 14 which gives a rolling diametre of 615mm (24.2") or a reduction in diameter of 0.81%

Other sizes are often queried such as:

• Radial 175/70 14 which gives a rolling diametre of 601mm (23.65") or a reduction in diameter of 3.06%
• Radial 195/65 14 which gives a rolling diametre of 609mm (23.98") or a reduction in diameter of 1.77%  (Caution when fitting to a 5J rim, it may invalidate your insurance).

Comment:

Availability of tyres in 165 14 is becoming more difficult on the high street although specialist tyre suppliers can still offer the 165 14 tyres in brands like Uniroyal, Falken, Toyo etc.  Be aware of some that may be a commercial rating rather than passenger car.  

The choice of 185/70 14 is usually down to the wider availability and lower pricing of this size.  Be aware that some owners may experience tyre rub on the rear axle - a condition that is less likely to affect the standard ride height rubber bumper cars, but may affect the chrome bumper cars.  This is down to possibly worn springs or just a quirk of the B/BGT in that the axle is sometimes not perfectly central.

Speedo Accuracy - The percentage changes shown above reflect the fact that the speedo accuracy will be affected.  A reduction in the overall diametre means the speedo will over read, whereas an increase in the overall diametre will give and under-read on the speedo.

MGB GT V8 -

As B/BGT but originally with 175 14 tyres.  

Speedos will be specific to the factory V8, but if you are fitting a more powerful engine to a B Series powered B then increasing the rolling radius of your tyre would allow a greater top speed, but speedo accuracy would be out accordingly.

MGC (and optional on B/BGT) - 

Original fit: 

165 15 (usually implies an 80% tyre wall height) which gives a rolling radius of 645mm (25.39")

Alternative fit: 

• Radial 175/75 15 which gives a rolling diametre of 644mm (24.33") or a reduction in diameter of 0.16%
• Radial 185/70 15 which gives a rolling diametre of 640mm (25.2") or a reduction in diameter of 0.78%

Tyre Pressures on all B/Cs: 

I have avoided quoting these as this is a matter of personal preference and modern tyres do not always perform at their best when using the original tyre pressure settings.

From its launch the B and BGT were offered with either steel rims or wire spoked wheels.  The choice is a matter of taste.

Wire Wheels

Wires give the classic look, but there are some issues to consider:

Wire Wheels offer the classic B look, and work well with the chrome bumper cars, but a few points to keep in mind:

• Converting to Wires requires different hubs to fit
• More effort to keep them clean (although Fairy Liquid spray is reputed to work well!)
• Requires tubes
• More expensive to purchase or replace
• Harder to find specialists capable of balancing and maintaining the rims
• You'll need to keep the brake drums and callipers looking smart!
• You'll need to carry a soft mallet and remember "Soldiers march off to the front" as the threads are handed depending on the side of the car.
• A clonking from the rear could be worn splines on the hub.

Steel Rims

AKA Mk1 rims, these were normally fitted with a chrome plated hub cap as shown on the BLMC Publicity photo of an MGC GT below.

For the retro look, without hub-caps, below:

RO-Styles

For more on these wheels see Restoring RO-style rims

Introduced in the early 70s, so called as these were manufactured by Rubery-Owen in Birmingham and come in two options, either chrome plated with black inserts or steel with a silver finish and black inserts.  The off-set varies slightly between older and later Bs.  The correct finish is a satin black inset with a fuzzy edge to the inset as a result of spraying the insets with a mask.

A chrome version was also available but these are likely to be a specialist restoration and not a DIY restoration unless the chrome is still in exceptional condition.

Dunlop BGT V8 Rims

These rims were the standard factory fit on the V8 BGTs. Read more about budget versions and restoration here by JC.  The Dunlop V8 wheel is constructed from an aluminium disk in the centre of the wheel, which is riveted onto a chromed steel rim. They were fitted as standard equipment onto factory original V8 cars.

Alternatives

Anything is possible, so long as the PCD, rim width and offset allow the fitment.  Even differing PCDs can be sorted with enough time, patience and money.  Of course, the ever popular period look Minilite is the easiest choice without detracting from the car's classic lines.  However, other styles can prove equally as attractive, although some will find anything too modern with too low a profile will not gel with the car's styling.

For more on alternative rims...

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