Reply to Keith regarding threads
We have discussed the problem of the threads with Keith and concluded that the threads were not at fault. Keith was using a non tapped galvanised handwheel. With galvanized threads you can only use tapped oversize galvanised nuts as the galvanised layer effectively alters the size of the thread. Whilst this is well known in industry, perhaps less so else where. So we have now added a comment to that effect in each product description
64 mm diameter U bolts
Fiat have such fat roof bars that I needed to buy new U bolts to attach our cycle carriers. U-bolts-R-us advertised the very thing I needed so I ordered 12. They didn't have enough in stock but made the others very promptly. When they arrived, 5 of them are good and the other 7 are not fit for purpose. I think the poor ones must be the newly manufactured ones. The problem with them seems to be that the thread is full of the galvanising so they will not take M6 handwheels as required. I have ordered an M6 thread cleaning die on ebay and hope that will solve the problem.