V8 Column for February 2006

SPACESAVER SPARE WHEEL FOR V8 ROADSTERS & MGBGTV8s

Space saver wheel fitted in a neatly trimmed V8 Roadster boot. (Photo: David Waterton)

With boot capacity being at a premium in a V8 Roadster when the full size steel/alloy wheel is in place, David Waterton (Tornado Red 4330) set about finding a suitable space saver spare wheel as an alternative. Although the speed limit for these wheel and tyre combinations is 50 mph (80 kph), I have had first hand experience of driving my non MG 'everyday' car, fully loaded, for over 300 miles on such a wheel without incident. Casting my mind back to a Silverstone International weekend meeting in the 1980s, I remembered a conversation with a Saab 900 owner whose 'weekend' car was a MGBGTV8. He mentioned that his Saab space saver was an exact fit for the four stud V8 hub. Given the 20 year gap, I started to search for a wheel at a local Saab breaker's yard. I discovered the hard way that the 'classic' 900 model had two different sized four stud hubs fitted during its long production run. The later, and more readily available, space saver wheel does not fit a V8 hub. The correct match, for the MGB hub, appears to be for the pre-1987 Saab model. This part is also no longer available

from Saab dealers but you will find the part number is stamped on the centre of the wheel near the stud holes as 8242088 together with the wheel size 4Jx15.

Having obtained a wheel rim from a breaker's yard, the next task was to check on tyre availability. There were various sizes of Michelin space saver tyres fitted during the production cycle of this 15 inch rim, none of which are available today. The fact that the standard V8 rim has a 14 inch diameter is of little concern, as it is the rolling circumference/revolutions per mile and load rating that are the important factors. My V8 Roadster is fitted with 195/60R15 tyres for which the circumference is 76.1 inches and the revolutions per mile are 833. The Factory fitted MGBGTV8 tyres are 175/80R14 with a circumference of 78.6 inches and the revolutions per mile are 806. It appears that in the UK, Continental and Pirelli space saver tyres are most easily available. I chose a Continental T125/80R15 95M tyre with a circumference of 71.9 inches and revolutions per mile = 882. This is -5.5% compared with my current tyres. That variation is, in my opinion, an acceptable trade off for boot space gained against a small speedometer error. After all it is only a temporary spare designed to get you home or to the nearest tyre repairer or supplier.

The final modification is to secure the thinner space saver wheel to the boot floor. To do this you either have to obtain a spare wheel retaining bolt, as fitted to the MGBGTV8, and then reduce its length so as not to puncture the top of the fuel tank, or go to your local bolt specialist supplier and purchase the correct length item and a large flat steel washer to hold your new spare wheel in place. The net result is considerably more room in the boot, enough for a good sized kit bag and various other items which can be stowed around the edge of the tyre.