I think its been raining every weekend since I made this adaptor, this weekend at last it was looking dry.
In the meantime I've been doing a bit of background work. Clearly there is a concern that this will increase the loading on the entire steering system, particularly in low speed situations. I don't have any figures to compare against but there appears to be plenty of evidence to suggest that Series steering is up to the job of supporting larger wheels and tires.
I manged to find an online tyre data calculator and if I pump in numbers for a typical 7.50" wheel tire combination and the popular 235/85 16 wheel tire combination I can get some numbers for the contact patch area. The numbers come out at 220cm2 for the 7.50 and 336cm2 for the 235/85. That's a 50% increase in contact patch area, if we assume we get a proportional increase in friction then that also means a similar increase in force though the steering and that's without the additional force due to the wider wheel with its increase offset. I understand that this conversion should reduce the number of turns lock to lock by about 25% so I'm reasonably confident about the loads being OK.
Anyway, a couple of pictures showing the conversion being fitted.
So its all bolted up and the tracking has been done and I've ended up going from 3 3/4 turns to 2 1/4 turns lock to lock, rather more reduction than I had expected.
Its been out for a couple of test drives just to make sure all is well. I can report that it all works extremely well, obviously takes a bit of getting use to but the steering is nicely weighted, you get noticeably more self centring and of course it makes all those tight urban manoeuvres that much easier, BUT something is not right. At low speeds, around 15 to 20 MPH a bump can send the steering into a wobble, nothing particularly violent or long lasting but not nice. I had may concerns about the geometry before starting on this. The tie bar is free to rotate on its ball joints and the drag link feeds into this tie bar. I've tried to arrange it so a virtual line between the two drag link ball joints intersects with the centre of the tie bar ball joint next to the adaptor. Operating the steering at rest there is no apparent twisting of the tie bar but it seems that when a wheel hits a road bump this tie bar can oscillate, this then has the effect of putting in a small steering input and the oscillations build up.
So its all been taken off and returned to stock, its been fun but ultimately futile.