The first thing I did yesterday morning was to call Cork Adams at Precision Wire Wheel, and the information he gave me made me feel that my wheels might not be as bad as it seems. I had heard before about British wire wheels having specific requirements for balancing, but I don’t know why I assumed Ferraris would be any different!
The hub of a wire wheel seats to the hub on the car via beveled mating surface. If any other surface is used to check for trueness, there will be inaccuracies. It seems this was the case with what happened at the tire shop the other day. The wheel was mounted to the balancing machine where the outer ring of the hub was used seated to the machine. This surface where the spokes are mounted, is not always true, and should not be used to balance the wheel.
Just to make myself feel a little better I checked for trueness with a wheel mounted on one of the hubs. Instead of getting really anal with a dial indicator, I used this phillips head screwdriver clamped to a jack stand to check by eye. I left a slight air gap between the wheel and the screwdriver, and carefully turned the wheel. I measured three points on the wheel, the outside of the rim (as pictured), and both bead seats where the tire would mount to the inside of the wheel. There was a slight deviation, but certainly not as bad as it looked a couple of days ago. Cork trues wheels to 0.010 inches in wobble (what we would be checking in this picture), and 0.020 inches in up and down movement. His extreme accuracy guarantees no returns on his work. Cork explained the even Porsche allows 0.040 inches deviation on the Rudge knock offs, which he thinks is excessive. I guess it’s all a matter of taste, and acceptable vibration.
Cork Adams suggested I take my wheels back to the tire shop and see if they would mount one of their cone adapters to the rear face of the wheel. We needed to find one that would fit to the bevel of the wheel, and allow that to be our reference point for trueness. Unfortunately, we looked at all the combinations of cones and adapters, and couldn’t find something that would work! So I spent another morning taking my tires and wheels out for a drive!
Brian Brown, who works for Patrick Ottis Co. in Berkeley, told me they had special adapters made up for their local tire store to balance Borranis, so I think I’m at the same point. I spoke to my friend Dave, the CBS machinist, and he thinks he can machine an adapter to fit on the balancing machine that will work. I took some measurements of the balancing machine, and I’m going to bring him one of my wheels. I’m pretty confident we’ll come up with something that will work!
Many of you are probably wondering what has François done all these years of restoration. He takes his tires to a guy who has all the machines and adapters to do this kind of work, but he’s really expensive! It’s almost embarrassing to say how much it costs, even with Ferrari prices! I’m determined to find a cheaper alternative, and if I’m successful, I may even save some of François’ customers a buck or two!
Previous Restoration Day
Next Restoration Day
Ferrari Home Page