If it's in the shoulder We use the 2 finger rule, which is put 2 fingers on the shoulder if the nail is in that area then it's a new tire or we will install your spare. Thats it. It is a dangerous repair and it's probably not going to hold. If you repair a tire like that, you have just opened the door for a possible lawsuit. Same thing with string plugs they are in noway safe. If it is a last resort then do it to get you to a facility that can install a patch. IM SURE THIER ARE DISAGREERS ON THIS!! Tires are a very touchy topic these days for shops. So (most) many cars and also SUV's are coming with speed rated tires. It is crucial to stay with the same factory rating. You can go higher just not under. Many shops are still breaking this rule, but good news is that more are not. Lets face it you can get sued for about anything these days. Why break a rule and open the door.