Does Size Really Matter? (about tires)

[MadMatt62]

Hi all,

I know there are a lot of different tire threads throughout the forum but I'm coming to the Aurora owners because I own a '98 Aurora myself.

I'm needing a change of rubber and although the prescribed size indicates a 235/60R16 I was wondering whether putting 225/60R16 would have a detrimental affect on the handling of the car. The reason I'm asking is that the price difference between the 225 and 235 is about 30% and with 3 hungry kids and a shopping wife to support I'm looking at budgetary constraints.

Any opinions? I thank you in advance and keep up the great info everyone.

[ugsrich]

Well, you asked for opinions (and we all know what an opinion is akin to). I have a ’95 by the way so we share the same vehicle body style. That piece of information is irrelevant however as my opinion has less to do with the vehicle characteristics and more to do with the manufacturer’s specifications.

Given that brief background my opinion is that one should make every reasonable attempt to maintain their vehicle as prescribed by the manufacturer. The vehicle was nominally designed to be operated at those specifications. Naturally, given the fact that multi-ton vehicles, carrying large quantities of highly-volatile gasoline in their fuel tanks are engineered to be operated by morons at speeds in excess of 60mph (that’s a mile-a-minute to you and me) it is safe to say there is a HUGE safety factor built into vehicles systems. Not withstanding the safety factor that folks much smarter than me engineer into the vehicle I prefer a vehicle setup that keeps me in the nominal range. I believe this is important to ensure vehicle component longevity (tires in this case). I believe this is important in the case of vehicle handling and stability. And, I believe this is important in the case of operational efficiency.

Two of the three points mentioned drive specifically to the choice you are faced with; saving money on an alternate tire size. Given the criteria stated above various tire sizes will wear differently based their ability to dissipate heat. A smaller tire will rotate at a higher angular velocity to cover a given distance at a given speed. This means more heat build up (greater wear) and potentially shortened longevity (you may need to buy new tires sooner costing you $$$). The matter of wear will apply equally to your driving habits and is extended to include cornering, braking, etc. In terms of operational efficiency the vehicle’s fuel consumption is functionally proportional to engine speed (as well as other matters). Here again, a change in tire size will modify the velocity at which the engine must turn in order to maintain a given vehicle speed. Smaller tires will need to rotate faster and thus the engine RPM is higher and thus one consumes more fuel. On the matter of stability, most of us are not running NASCAR, there are simply too many other unpredictable factors, not the least of which might be the maintenance of proper tire pressure (when did you last check yours?), that to make rationale argument about stability is most likely not pertinent in most cases.

That’s my view and explanation. My opinion in short: Size does matter; operate the vehicle at its nominal design specification.

Let us know what you decide. Your decision will be the best one for you!

[newscarver]

check out this tire size calculator www.miata.net/garage/tirecalc.hmtl

[newscarver]

same link...click garage,click tires and wheels, click tire size calculator in the tire box

[MadMatt62]

Yeah I realized that after the fact and (too late) deleted my post of uselessness. Thanks. Gives me an idea of what I can work with.

[SteVB]

hi,
i have a VERY affordable solution. you can get great name brand tires on EbayMotors. i bought a similar set(of falkens) for my aurora & theyre SO much better than the 900.00 i spent on goodyear eagle LS (JUNK) that never rode good, & alot more affordable than the 700.00 set of michelin pilot`s that i had last time. you can`t beat the price.
here is a link: http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW.
if youre not an ebay member,now`s the time to become one. this price includes free shipping to your home.i almost thought it was too good to be true when i bought mine, but its real.
steve~

[unioncreek]

I did the same tire change on my 95 Aurora. I had bought new tires for my Delta 88 and then gave it to my son. I kept the 225 and swapped them over to replace the 235 on my Aurora. MPH is only about 1 so the difference is not great enough for the computer to realize the difference. I don't know what kind of tires you guys are buying, but I only spent $400 for speed rate tires and they last me up to 70K.

Bobg

[vamc]

i get yokohama as430 for mine. 130 bucks a peice. they are z rated. but i would stay with what the car calls for because the sispention and car weight can affect how the tries ride. meaning that some 225 or 235 tires will ride different. but all in all, use your best judgement, and talk to gm, they can also tell you what they think.

[dobbst]

I agree w/ the second post. I'd stay with what the manufacture recomends. That is 235/60R16. I just spent a little under 300 for kumho tires on www.tirerack.com. Have i ever heard of kumho? The answer is no, however they sure beat the $500 that goodyear would have cost me.

[blong1385]

going from 235/60 to 225/60's is not going to make a difference. i ran a set of 225's for a while and it was fine. going from a there is not much of a difference in size here. going from 235 to 225 is not much thinner, and it wont heat up faster and quicker like the first person replied on here. there are however different types of temperature ratings on tires. C to A, A being the best and C the worst. The A's will withstand heat much better and will degrade slower. switching to smaller tires will not degrade them. Infact they should give you better gas mileage because there is less tire contacting the roud, that is why you get better gas mileage if you run proper air pressure. I worked in a tireshop for 2 years so I think i know a little more than the average car owner.

[vamc]

Well AA is the best not A. "A" is second best. I have been working on cars for approx 9years. And i know that AA is the best. You did not state that before.

[BNaylor]

Sorry guys old thread. Thread closed.