Tires tires tires

[thatmacguy]

Long story short: Due to an inability to find 165/80/15s on a routine basis, I've moved to (original appearance) 5.5" steel wheels and 195/65/15 tires, which produce close to the same rolling diameter. I'm not fond of this particular set of tires however, and since I happen to need 4 tires in that size for my Prius, I will be moving them there and replacing my Beetle tires with something better. I do run autocross, so I'm going to stick with something in the "high-performance" range, but want to shift down to 185/65/15s on the front and stay with a 195/65/15s on the rear. This will help make the look of the car from the front a little less weird (wide tires look fine from the rear and sides, but from front-on they are freaky!). The Bridgestone Potenza RE960As Pole Positon is the only performance tire available in a 185/65/15 (at least, the only one I can find).

Will this small difference in rolling diameters be a problem for autocross or daily driving? Would I be better off sticking 185/65/15s on the car all-around? I expect the "contact patch" can be sufficiently different between the two sizes to cause much of an issue, but I don't know if different rolling diameters will create problems.

Thanks!

[dubfreak1]

Hi David,

Keeping the tires the same size front and rear will allow you to rotate front to rear, plus the 185/65 will give you a little overall gearing advantage compared to the 195/65. I don't have any experience with the Bridgestones you are asking about, but do like Bridgestones in general. I ran Fuzion HRi tires on my Jetta with good results. They were very prerdictable and drivable. Mine are shaved to 4/32nds. Whatever tire you buy, consider getting it at the Tirerack and have them shaved. Call Denny at 1 800 428 8355 ext 321 and he will help you out. I know you want to use these on the street too, so maybe you will want to go to 6/32nds. The closer you shave them the better they will work, however.

Rudy

[dansam]

I have a set of 1980 camero z28 aluminum rims in gold (think general lee wheels in gold) with get this 245/60r14 bfg T/A's (yes Ill make anyone a hellovadeal) I got them cuz they were the same hight as a stock bug tire and I put them on the dune buggy for cone racing, well that is untill I test drove them and learned a lesson in big tires on light cars. The loading area is so light (pounds per sqr inch of rubber on the road) that they handled worse than my skinnies. They kinda understeer like crazy like you are on gravel. I asked some people in the know and found out there was just not enough weight on the front to push the tire onto the ground so they kinda skit over the pavement on turns!!! That is a big reason I went to the skinnies 165/80r15 on the 5 spokes. I really like em and they handle great. Im sure Ill tax there limits this summer but I like oversteer anyway

Dan

[dansam]

oh yea um, JC whitney has a great deal on the 165/80r15's

[thatmacguy]

Thanks guys! I actually do like the handling of the current tires a fair amount - at least in my case they do have more grip than my old 165s (of course, those 165s were so old they were starting to show cracking, so I had the get them replaced ASAP). They are Kumho Ecsta ASTs, which I think will be fine on my Prius. My primary reason for moving is to get a slightly nicer ride on the Bug and to reduce the fatness of the front tires just a little.

I should probably have specified that I'm not trying to build this car for just autocross, so I actually want to keep the rolling diameter as close as possible to "correct" - so that I can still drive on the highway without feeling like I'm overtaxing the engine. Thus my idea of going 195/65/15 on the Rear and 185/65/15 on the front. In the end, if it looks good on the car, I guess 185/65/15 all around does make more sense. The rolling diameter isn't that much different, so it can't make *that much* difference at highway speeds I suppose. I'll look up my tire-calculator and check it out from a statistics standpoint.

I do have a serious "snap understeer" issue, but that is due to a problem in the front suspension which I'm currently in the process of attempting to rectify. I also don't like understeer, but I can live with manageable amounts of it, especially as I can induce oversteer instead by letting off the throttle (assuming I have enough speed) and letting that wonderful rear-engine design start pulling the back around. What I don't like is when the car transitions from progressive and manageable understeer immediately into "going absolutely straight ahead." It did this so badly at one event last year that stopped mid-course and drove tenderly off the track thinking that something in the front end must have broken... Oops!! Really scared me (probably scared the people I was driving straight towards as well).

But, if I were to go 195/65/15 rear and 185/65/15 front do you see any potential handling problems due to the mixed tire sizes?

[dubfreak1]

A friend ran this exact setup on his 70 Bug and it worked out fine. I'm planning on 195/65 Rear and 165/80 Front on my Black 70. These are street applications. You will aggrevate understeer with smaller fronts, however.

[thatmacguy]

Thanks again guys. I have my local tire-shop putting a used 185/65/15 on a wheel for me tomorrow, that way I can see what that size tire looks like on the car.