One more tire question

I've looked on tirerack and odyclub (registered but haven't received an e-mail and it's been a while) and I can't find the answer to this. I noticed with some tires there are people going up a size, to 235/60/16 from 225/60/16. I think this has something to do with a rating (one is 97 and one 98 on certain tires). Honda seems to want/require a 98 rating and going up a size gets it. Is it ok to go up a size, and how does that effect things like gas mileage and odometer/speedometer? What happens if you get a tire with a 97 rating? We never tow anything and, if I understand correctly, the rating has something to do with pounds per inch on the tire, or something related or similar. We are thinking of going with the Michelin hydroedge or Michelin X as those seem to be the most recommended that I can find on odyclub, but I believe on both of them you have to go up a size to get the rating Honda wants. Sorry for all of the questions......it seems like I'm finding out that I don't know much about the stuff on my car and I want to understand it to the best of my ability before having someone try to sell me something that shouldn't be on there!!

don't worry about the 97 versus 98 rating... that is relatively meaningless. you are right that it has to do with weight rating, but there is no practical difference between 97 and 98...

as for tire size, many people opt to size up a notch, because it will improve the handling of the car... that is one of the first and least expensive things people do to improve the cornering (and emergency avoidance) capability of their cars. but there is a proper technique to choosing larger tire sizes. you can increase the tire width (235 vs 225 is a 10mm increase in tread width) but then you should decrease the sidewall height (60 to 55). this is because that second number in the tire size (the 60 in your example) is called the aspect ratio, it is the height of the sidewall, expressed as a percentage of tread width. so a 235/60/16 tire has a sidewall height of 235 X 0.6, or 141mm. if you increase your treadwidth from 225 to 235, you are also increasing your sidewall height by 6 mm. this will increase the overall circumference of your tire and result in your speedometer reading slightly slower than your actual speed. so the proper way to upgrade your tire size would be to go from 225/60/16 to 235/55/16. then your speedometer will remain calibrated.

WOW!!! I think you've probably forgotten more about cars than I will ever know! Thanks a bunch! I think we've decided on the michilen X (can't seem to find the hydroedge anywhere around here). Now just to decide which size, but if we can find it probably the 235/55/16.