I have used dyna beads in bikes and ATVs with great results. Although it may say they will void the warrenty, consider the following;
If you go into a dealer with a cupped tire and want it replaced under warrenty, they will make a snap decision one way or the other. (This is before they know dyna beads are inside). Do you really think anyone would agree to replace a tire under warrenty and then change their mind when it is removed and the beads fall out? I don't think so. Warrenty if a decision made case by case. Maybe they will and maybe they won't. The mechanic won't care if beads fall out, he gets paid either way...
Warrenty coverage is probably more likely based on whether they see you as a good customer and/or just a complainer. Having been in the auto business most of my life it depends on a lot of factors. If a woman comes in screaming at the service writer becase her car was in 3 weeks ago for a brake job and now her water pump has failed; all she has to do is be a big enough pain and they will "warrenty" it just to shut her up and get rid of her. seen it hundreds of times...
Too much faith is put in the written document. For example you pay for insurance (medical, disability, etc.) You actually believe what the HR department tells you it will cover. The you have a serious accident or become disabled resulting in major expenses. they will drop you like a rock within the first two years and there is nothing you can do because it's in the fine print somewhere. I speak from expierence here. best part is you can't even sue them because they are probably protected by ERISA...
Now, I'm sure I'll get blasted by all the Insurance agents on here, but facts are facts. Everyone is in business to make a profit, and Dunlop or whomever is only going to help you out as long as it doesn't cost them too much. The paper contracts are not worth the paper they are written on.
jb