It centres on an advert by Goodyear Dunlop which claimed its D207e tyre was "the only economically-priced tyre from the major manufacturers".
The ASA investigated after a complaint from Maxxis, which argued it was a major manufacturer whose tyres were more economically priced than Goodyear's.
"Because the ad did not make clear the basis of the claim, and because we had not seen sufficient evidence to justify Maxxis exclusion, we concluded that the ad was likely to mislead," says the ASA's ruling.
"The ad must not appear again in its current form. We told GDT to make clear the basis of their claims and to ensure their comparisons were fair in future."