Dennis,
Thanks for the comments. The cracks were all in the same location - roughly
in the middle of the sidewalls - I'll post a picture to photobucket.
Tire wear has been even over the 30k distance. Having said that, the front
radius arm bushings are definitely shot, almost certainly original & every
time i look at them I think i should replace them.
The upper control arm bushings have been replaced and are in good shape. No
obvious brake fluid leaks (& remember, this was all four tires that were
bad).
Best advice I've seen so far is that the 44 psi I was running the tires at
was too low, the new ones are now at 48 psi and I may increase that further
to 50 (front) & 55 (back)
Thanks,

Michael Hart
Palo Alto, CA
'87 2WD Westfalia ('T3WESTY')

On Sat, Nov 22, 2014 at 8:01 AM, Dennis Haynes <d23haynes57@hotmail.com>
wrote:

> Was this cracking of the sidewall or where the tread meets the sidewall?
> Big difference. Tread separation and the steel belts working out can be a
> design or manufacturing defect but that usually occurs on both sides unless
> there is also an alignment or other issues. Same for under inflation.
> Sidewall checking or cracking on the inside only can be indication of fluid
> contamination. Brake fluid in particular does a number on tires over time.
>
> For alignment there are a number of mounts and bushings that go bad that
> will allow the alignment to change under load. The front radius rod mounts
> are a biggie. They may almost look good but they get compressed and allow
> the caster angle to change drastically and this will side load the tires
> during turns. If you don’t know when they were done last they likely need
> it. The upper control arm bushings are another sneaky cause of alignment
> and tire issues. I just had one (new) fail during a trip and completely
> trashed a pair of Nokian tires in about a 1,000 miles.  That was a very
> expensive bushing.
>
> Dennis
>