by txfsealord » Sun, 11 Jan 2009, 11:05 pm
Hi Inky,
I was looking today at the 2nd Portafold brochure on this site, which I haven't viewed before (I have an Ansfold) & I noticed it specified 5.20-12 tyres. This has to mean the use of Hillman Imp wheels, as they were the only 12" rims for this stud pcd (pitch circle diameter) available at that time. The picture in the brochure shows a Vauxhall Cresta towing a Porty fitted with 12" wheels.
It's interesting, as Imp wheels have a very big offset (displacement outwards). When they're fitted to an Austin A35/A40 to lower the gearing from those cars' original 13" rims, they stick out as if they have 1" spacers behind them. Now, on our vans I've noticed there's very little clearance, on the Rubery Owen axles, between the tyres of Mini wheels & the ends of the radius arms. If they were originally using the Imp rim with its huge offset, that might well explain this.
Also, the towball height often looks low compared to the 'modern average', both Portys & Ansfolds tending to adopt a nose-up attitude when hitched to a car. Add this to the large amount of room in the wheelarches, certainly more than needed for 10" rims, it all points to the 12" Imp rim as original fit in my opinion.
There is the issue of available suspension travel though, before we all rush off to eBay for Imp wheels. Bigger wheels mean the usual settling of the ride height on Port/Ans, due to the axle mounts distorting the fibreglas floor, spring-settlement etc., must be corrected otherwise the bigger tyres wear through the arches when running.
One last point: later Minis had 12" wheels which would also fit our studs. These had even less offset than the standard Mini rim as these cars all had disc brakes which protruded further than the earlier drums. I don't know if these rims would fit without fouling anything. I think it unlikely.
Steve Lord