QuestionQUESTION: I have a 1998 mustang gt with 245/45/17 "ultra high performance" tires. They were balanced "several times" and road forced on Hunter GSP. They cannot get 2 of the tires balanced right and they vibrate from around 60 to 65 mph. Can I switch tire size so I can get a better choice of "premium, non-aggressive tire? Maybe 235/50/17 (or something with a softer sidewall that will balance easier and ride smoother.
ANSWER: Kevin,
If you had the tires "RoadForced" on a Hunter GSP9700, then you have a good idea about how much road force they are generating. While this is not 100% reliable as a diagnostic tool, it is the best information available.
I'm going to guess that you either 1) got good values and there is still a vibration or 2) you got high values and can't get them lower by indexing the tire relative to the rim.
If it is #1, then it is likely that changing tires is not going to fix the problem - the problem is not in the tires or the rims.
If it is #2 - and your post seems to say that - changing tire size is not going to help you much. A simple change as you proposed is not enough of a change - there will be more difference between different tires than there is between the same tire in a single increment in size.
Plus, changing tire size doesn't make a tire easier to balance or more "round".
But I haven't mentioned that the problem might be the rims.
I have yet to meet a "tire buster" who knows how to do the rims properly on a Hunter GSP9700. To get the ultimate answer, you have to do the rim by itself.
So before you start running off the deep end, make sure you've got the whole package identified. I can help you there, but I will need to know what the road force values are for all 4 tires.
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QUESTION: "Barry",
Thanks so much for the quick response. I don't know the "road force" specs, (wish I did). As info, I bought "brand new" OEM wheels just to make sure and exact same performance. (I wanted a different style anyway) The only other info I could offer is that "twice" they "re-balanced" and kept putting 1 particular tire on the back, swapping with a smoother tire from the back. Makes me think they know they can't get the balance where they want it.
AnswerKevin,
You need to take a little more active role in this. As I said in the earlier post - #2 is probably the situation - and that could mean either the tires or the rims.
If the tires are newish - meaning less than a month old - then wherever you bought them from should get this right.
But if they are older than that - especially much older than that - then you're probably looking at a new purchase - and as I said earlier, changing tire size is not going to be a help here.
But where you are at this point isn't conclusive if it is the tires or the rims. Just because the rims are OE, doesn't mean they are perfect!
