Dougal Cawley

Hi

I have posted this on the 911 forum as well, because i think you guys coiuld do with knowing about it.

I thought I would share something with you, because as time goes on things get forgotten and your magazine will probably be the best way to get this knowledge into as many relevant people in on ego as possible so I hope you can publish it.

We have come across a few issues with people balancing wheels on some of the wider classic Porsche wheels. There is often a problem caused by people not wanting to have balance weights visible on the visible flange on the outboard side of the wheel. The intention is to put all the balance weights inboard of the structure of the wheels, so the rim looks smooth and cool. However, if you want to do dynamic balancing it often doesn't work on some classic Porsche wheels.



Right i'm not sure how good this picture is, but maybe if i describe it it might help.

the top picture is a modern generic wheel. The structure of the wheel, on the left, is on the out board of the wheel, leaving 3/4 of the wheel available to fit weights on. importantly the outboard weights, (which arguably would be better on the out board flange) are able to be placed over centre so they do still balance the wheel.

The wheel under neath has the wheel structure in the centre of the rim. So when attempting to dynamically balance this wheel the weights that should be outboard are not beyond the centre of the rim, and therefore don't have the desired efffect. effectiuvely you are just putting weights on the right hand side of the rim.

If you have these extreme wheels, either suck it up and put that weight exposed on that outer flange. or simply statically balance your wheels.

I hope i have explained that well. if you are having your wheels fitted don't take it for granted that people will understand this. We have been in contact with some very well respected Porsche people and supposedly expert tyre fitters who have not spotted this, or forgotten it. because it is such an unusual scenario, and i guess a forgotten technology. We have recently come across difficulties with people wanting to fit extra wide 285/40R15 and even 345/35R15 rear tyres on really wide wheels, thinking they cannot balance the tyres. It isn’t the tyres that is the problem, it is the unusual wheel structure and the desire to have no visible wheel weights, which can easily be fixed with static balancing. Static balancing isn’t as good as dynamic balancing, but to do that you need weights on the outer flange.

It is the on going battle of fashion versus function.