Rover P5 and P5B Wheels and Tyres. Rover P5 and P5B wheels are 5 x 5in PCD bolt pattern (5 x 127mm), 15 inch diameter.
On the P5 they are plain steel with chrome covers, whereas the P5B changed to what were popularly called Magnum style (as in Magnesium style), but now are better known as Rostyle wheels. The ‘R’ and ‘O’ of Rostyle doesn’t reference ROver as some claim, but references Rubery Owen, the British engineering company and supplier that produced the wheels for Rover.
Part of the issue I have with modern tyres is they can look too small on a car like the P5. Too small as in the sidewall looks too shallow, leaving the wheel arches looking empty. This is because modern tyres have a much lower sidewall height (profile) than older tyres – typically 30% lower. This article looks at the options open to P5 owners, and tries to find a balance between safety and looks.
Before we get to the detail, it’s important to say that any deviation from standard tyre fitment should be notified to your insurance company, or you could find yourself with invalid insurance. This even applies to fitting radial-ply tyres when cross-ply were specified in the manual, although it seems most companies accept this change. It’s better to ask and be sure, rather than assume.
A great generic resource on tyres and wheels is The Wheel And Tyre Bible.
It’s also worth pointing out that various sources state that the maximum safe width of tyre on a 5 inch wheel is 185mm. However, searching for equivalents to a 6.70x15 tyre on Longstone Tyres, a well known classic tyre supplier, throws-up radial options between 185 to 205. As with many things tyre-related, it’s very difficult to find a single answer to a question.
The original P5B tyres were cross-ply Avon Turbospeed or Dunlop Roadspeed, 6.70 x 15. Cross-ply tyres were much taller than radial-ply tyres, with a standard profile of around 100%. 6.70 inches equals 170mm, but to have that sidewall height a modern 70-profile tyre would need to be 243 mm wide (170mm / 70%). The nearest standard size to that would be 245/70 15 – much too wide for safety on a standard P5 or P5B wheel.
So, we need to make some compromises. The tallest radial-ply tyre is 80-profile. To achieve a height of 170mm would require a width of 213mm (170mm / 80%). The nearest standard size would be 215/80 15. That’s better but still generally considered too wide for safety (or it’s at least at the limit of a safe width according to what you believe) and several sources suggest it will place too much strain on the steering system. As mentioned earlier, 205 width is about as far as most people go.
Additionally, 80-profile tyres are only really available for vans (unsuitable for cars due to ride characteristics and/or speed rating) or 4x4 vehicles (SUV’s or off-roaders). There are a few that may be suitable though, especially when you consider the weight and suspension layout of a P5 – it’s not too dissimilar to a modern 4X4 (a P5B has a solid rear axle and weighs 1,600Kg, whereas a classic 4x4 has solid axles front and rear and weighs around 2000kg).
A 195/80 or 205/80 4x4 tyre with a tread pattern for mainly on-road usage still has a lower sidewall than the original 170 mm (156mm and 164mm respectively), but they are about as near as can be achieved with modern tyres.
If you want to use a car tyre, it seems the only generally available options are 70-profile tyres, and you’ll just need to live with the lower-profile look of the tyre (a 205/70 tyre has a 144mm sidewall height compared to 170mm for the original crossply tyres), as well as the inaccuracy of the speedometer / odometer and the increased engine speed for a given road speed. But, notify your insurer to be sure you’re covered.
This article was updated on 28 May 2017 following feedback from a reader – I appreciate taking the time to correct my basic maths error! The error doesn’t change the advice in the above article, but does affect some of the values in the table below.
|Size||Type||Width||Sidewall Height||Circumference||% Difference||Indicated 70mph Is Actually||Notes|
|6.70 x 15||Original Equipment: Avon Turbospeed or Dunlop Roadspeed||6.70 inches / 170 mm||6.70 inches / 170 mm||2265 mm||-||70 mph||Original factory-fitted tyre, crossply.|
|195/80 15||4x4 tyre||195 mm||156 mm||2176 mm||-4%||67.2 mph|
|205/70 15||Car tyre||205 mm||144 mm||2097 mm||-7%||64.8 mph|
|205/80 15||4x4 tyre||205 mm||164 mm||2226 mm||-2%||68.8 mph|
Cross Ply tyres recommended to be inflated to 26 psi.
Radial tyres are recommended to be inflated to 30 psi.