Upsizing tires and stability

[Tommyboy]

I recently bought a '95 Ford Aspire for commuting (45 mpg). The front tires were/are 175/70R13's, and fairly new. The rear's were 165/70R13's and were not good. I went to the tire store and got some new rear tires to match the fronts. The tires from the factory were 165/70R13's.
It now seems to have poor stability, as if I could easily roll the car on a sharp turn. Would the larger tires cause that much effect? It wasn't this bad before I replaced the rear tires.

 

[XS650]

Quote:

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I recently bought a '95 Ford Aspire for commuting (45 mpg). The front tires were/are 175/70R13's, and fairly new. The rear's were 165/70R13's and were not good. I went to the tire store and got some new rear tires to match the fronts. The tires from the factory were 165/70R13's.
It now seems to have poor stability, as if I could easily roll the car on a sharp turn. Would the larger tires cause that much effect? It wasn't this bad before I replaced the rear tires.

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It would be difficult to feel the difference between those two sizes if they were the same make and model tire.

If you mixed tire make and model, then most anything could happen.

As a guess, it sounds like the rear tires you put on are a lot less stiff than the fronts.

If that's the problem, try swapping your tires front to rear, the car will feel stabler with the flexier tires on the front.

Were they cheap tires?

 

[XS650]

Have you checked tire pressure. Tire stores are notorious for getting that wrong.

 

[GMGuy]

What pressure are you running? Maybe you need to bump it up a couple pounds and see what transpires.

Alex.

 

[GMGuy]

Ooops. Gotta remember to refresh when I have a bunch of tabs open.

Alex.

 

[Tommyboy]

Thanks.... haven't checked the tire pressure.
And, yes, they were the cheapest they had. Mohawk or something. The front's are the Eclipse from Les Schwab.
I'll try swapping them then, thanks!

 

[wantin150]

I'll throw in my vote for air pressure also. If the front's are almost new, then having the newest tires on the rear isn't "that" important. For curiosity sake, what does this mfg recommend for PSI for this vehicle?

 

[XS650]

Quote:

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Thanks.... haven't checked the tire pressure.
And, yes, they were the cheapest they had. Mohawk or something. The front's are the Eclipse from Les Schwab.
I'll try swapping them then, thanks!

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Set the pressure to factory pressure first.

 

[Master ACiD]

10mm width shouldnt make any difference in what youre getting. id vote for a pressure issue as well.

 

[Quattro Pete]

Quote:

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id vote for a pressure issue as well.

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Or just a ---- tire with very soft sidewalls.

Also, if he went from nearly bald tires to new tires with full tread, he will experience more "tread squirm" - the same tire with full tread will not feel as responsive as a bald one.

 

[kazual]

I would think air pressure or worn suspension. Check your struts or shocks.

 

[Quest]

kazual is right on the money.

I used to own a Ford Festiva (pre Apire, same as Mazda 121) and I must tell you that as you rake up the mileage, the rear shocks tend to go first and the softness and relatively instability during maneouvering (cornering,etc.) is mostly attributed to bad struts + shocks.

REplace them ASAP for good road handling and suspension characteristics are important to these lightweight cars. If you ignore this problem it may cost you dearly down the road (or even your life).

I had mine replaced with MOnroe immediately after I acquired my Festiva, and then the vehicle handled very well afterwards (it was my winter commute car for 3 yrs in icy highway conditions with Woosung 12" tires)

 

[ewetho]

On smaller cars I had found changing sizes that increases sidewall height does cause a loose floppy sensation. Remember as you get smaller tires each change is a larger percentage of the overall. So it is possible that you felt a change in what it does. Also a change in brand and quality change in tire can cause a major change even in the same SIZE. So it could be a double whammy.

Check your pressures though. You may just have to slow down.

 

[rjundi]

The likely case if the tire pressure is okay is you bought junk tires. Budget tires in small tires are plain awful and IMHO not worth it. A quality tire is not significantly expensive in this tire size range.