We mount hundreds of sets of track tires per year and a conversation that comes up regularly with some keyboard racers is the idea that wheel weights need to be taped down with foil tape. While foil tape will prevent wheel weights from falling off, we don't believe this is necessary nor is there a net benefit from doing so. Here's why we don't recommend it or bother doing it on our personal track cars.
It's important to understand that wheels are not in a permanent state of balance after attaching wheel weights. Take even a purely street-driven car and drive on a set of perfectly balanced tires for 10000 kilometres and spin the wheels again on a balancer if you don't believe us. The fact is tire wear will change the balance of a wheel and tire combo and while street driving may not result in excessive imbalance due to tire wear, track driving quickly exacerbates the issue.
Take this Nankang CRS front tire from our GT4 for example. You can see significant outside shoulder wear while the inside still has relatively good tread. If this wheel were to have been perfectly balanced when the tires were brand new with perfectly even tread one can easily see why this would no longer be balanced after this type of wear. Additionally you can see the chunks of excess rubber stuck to the tire and further lumps and bumps on this tire that would surely affect the smoothness of the ride as well as the balance. This is why chasing perfectly balanced and smooth tires on a track setup is typically an exercise in futility. If you're not tracking to the point where your tires have chunks or uneven wear, you're probably not generating enough heat to lose wheel weights anyway.
As an experiment we did tape down the weights on this wheel (video below) and still saw a net imbalance of around 1.25oz which is definitely enough that you would feel a vibration at highway speeds. We did line up the marks on the tire to the valve stem on this tire and noticed it did not shift whatsoever yet the tire still went out of balance. It's also worth noting all of the rubber and marbles stuck to the inner barrel of the wheel which also impact the balance of the wheel/tire.
OK sure, a track wheel probably won't remain perfectly balanced even if the weights don't move whatsoever, but is there any downside to using foil tape? Having dealt with so many sets of track wheels with and without the use of foil tape, we'd say that the biggest downside is additional cleanup as the tape has to cover not only the weights but additional surface area of the wheel barrel to be effective. If a wheel has excessive tape residue and cleanup is necessary to balance a wheel properly, expect to be charged an additional hour of cleanup to remove residue and tape marks to give a wheel a clean surface to stick wheel weights onto. Scraping old weights off will also be significantly harder if there's a layer of tape over them.
In our opinion, this puts you in a situation with minimal upside and definite downsides. It's unnecessary extra costs/labour/cleanup for a process that isn't actually effective in keeping a wheel balanced.