Tim
Unfortunately this could be due to a number of things, many of which could put your life at risk. For instance it could be something as simple as a lost balance weight, but could be due to more serious problems like kerbing damage to the tyre/wheel, or brake or suspension faults. If you are not totally confident of your abilities then this is one area where its definitely worth getting a garage or tyre specialist to check the vehicle over.
Note some “upgraded” alloy wheels are more susceptible to distortion as a result of kerbing than stock VW wheels. I have no idea how robust the Santa Monica’s are. If there is an issue with these wheels then its possibly covered in other threads.
If you really want to try and diagnose the problem yourself, then here are a few pointers.
The obvious first step is to begin by doing a quick visual check of the basics. Take a notepad and write down the make/size information from all 4 tyres on the vehicle. Check that all 4 wheels/tyres are compatible, and correctly fitted. Eg same size, correct pressures, any rotational indicators are complied with and you have not mixed radial/crossplys, no obvious tyre bulges, gashes or other damage, no loose/missing wheel nuts.
Assuming they are OK then start by replacing the suspect wheel with the spare tyre. (not got one the same size – then pop along to one of the Ace Café meets and see if you can borrow one) If that solves the problem, then test the wheel/tyre you have just removed by rolling the damaged wheel/tyre along a flat floor. If the tyre wobbles or has obvious bulges then ask yourself what caused the tyre/wheel to become distorted? If you have hit a large pothole recently or clouted a kerb too hard, then simply replacing it may not be the whole solution as damage may have been sustained by the suspension. If the tyre shows signs of uneven wear then don’t just replace the tyre and assume the wheel rim is OK - get a tyre specialist to check the rim carefully before thinking of using it again. If its badly distorted you may need to bin the rim.
If the tyres/wheel seem OK, then you need to check for damage/wear in the suspension linkages and especially check to see if there are any worn bushes.
Finally check the state of the brake disc/brake drum. Get an assistant to apply light/consistent pressure to the foot brake so that you can just rotate the wheel/drum by hand – is the braking consistent or does it catch noticeably at the same point during each rotation. If so check the brake disc is not scored, warped or has worn below the thickness set in the manual. If the car has drum brakes remove the drum and check to see if the drum is scored or has got contaminated with oil resulting in uneven braking.
Hope you get it sorted. Let us know how you get on.
Skimad