Topic: Changing Aspect Ratio

[buickrendezvous]

I have a 03 Buick Rendezvous, and I need winter tires...  the stock Tires are 215 70R16, can I go to a 215 65 R16, or 225 65 R16.  The 215 70 R16 are almost double the price in the town I live in.... any help would be great!!

thanx

[keithb]

First off I'm surprised at the cost premium that you noted. Checking Tire Trends for a Hankook W300 and you see that the 215 -70 is actually about $20 cheaper per tire than the 215-65. Obviously something different going on at your local tire store.
Both options that you noted will be smaller diamater and reduce ground clearance -not much for the 225-65 but 0.43 inches (diameter is 0.85 inches less)   for the 215-65 -this is a fair bit. Also the 225-65 will be slightly wider and, while not a big difference, it is not preferable direction for winter tires where narrower is better. Both options will throw the speedo off a bit.
you can compare tire dimensions for different sizes. However when the diameter difference from the base tire is greater than 3% , you get a pop-up warning that brake failure
is a risk . Does anyone know the rational behind this?

[HeliDriver]

... However when the diameter difference from the base tire is greater than 3% , you get a pop-up warning that brake failure
is a risk . Does anyone know the rational behind this?

I think the danger in this case is that a change in tire diameter could confuse the vehicle's ABS computer, possibly causing the ABS to malfunction, or maybe just not to function quite as the manufacturer intended.

I do think the warning is a little over the top, though. To me, brake failure means that you stand on the pedal and nothing happens. 

[ArticSteve]

If this car is driven at a reasonable speed and not over loaded get the 215/65/16 on steel rims.  The speedo will be off by 2 mph @ 60 mph (will read 58.2 mph)  ABS not a problem.  Its all about the money.

[morty]

Why not just stick with the stock size? As stated the 215/70/16 is usually cheaper and will keep everything stock. I cant see a 225/65/16 being cheaper let alone available as it is sold out most places and a premium price.

[ArticSteve]

Why not just stick with the stock size? As stated the 215/70/16 is usually cheaper and will keep everything stock. I cant see a 225/65/16 being cheaper let alone available as it is sold out most places and a premium price.

The poster said this:  The 215 70 R16 are almost double the price in the town I live in.... any help would be great!!

If he says they're almost double in his town then one can assume he has priced the other two sizes and that they are available.   His concern/question is with change in aspect ratio.

[morty]

Almost double means someone is charging too much for their tires. In most other places the 215/70/16 is dramatically cheaper. It is the best option.

[ArticSteve]

 

[Windex]

Changing the aspect ratio of the tire is OK, given that:

1) the overall diameter (and circumference) remain as close as possible to the original size.  slight variations are OK, and larger variations are also OK, as long as you replace all four tires.  If you replace only two, then the ABS computer will become confused by the different speed readings front vs. rear.

2) that the section width of the tire (the first number in the tire size) is small enough to fit the car without rubbing on the fender or strut.  The only way to tell this one is to fit the tire and see, or talk to someone who has experience with that vehicle/tire size combo.

a helpful site for checking tire size differences:

http://www.miata.net/garage/tirecalc.html

Good luck!