size compromise

good day.

just wanted to ask something (tire rack gurus and to anyone).

what would be the right replacement for my stock tires (195/70/14)?

i checked the radius of a 215/45/17 and a 215/50/17. my stock tires lie somewhere in the middle of these two. should i go with the bigger or the smaller? what is an allowable percent diffrence or change in radius?

thanks!!

Your 195/70-14 tire is 24.7 inches the following sizes will be close to this size:

245/45-16 24.7 50000 245/40-17 24.7
205/50-17 25.1 50150 255/40-17 25.0
215/45-17 24.6 50450 265/40-17 25.4
215/50-17 25.5 50700 275/35-17 24.6
225/45-17 25.0 50900 285/35-17 24.8
235/45-17 25.3 53400 215/40-18 24.7

We recommend staying within a 3% margin of the original size excluding clearance issues. I don't have enough info on your car to know what sizes will rub.

Main advantages of going a little smaller are better gearing & sharper steering response because of the shorter sidewall.

Main disadvantages of going a little smaller are harsher ride, more road noise over bumps, larger fender gap (not as much of an issue on lowered cars) and slightly worse fuel economy.

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thank you!!

There is a math formula to figuring out how tall each tire is... check this out.
185/65 R14 - thats 185mm of tread width. there is 25mm in an inch.... 185/25=7.4"
65 is the series... all this is, it's a % of the treadwidth.
65%=.65x7.4=4.81" multiply this # by 2 = 9.62" , (because this is your sidewall, the tire above, below and all the way around the wheel) + your rim size which in this case is R14=23.62"=185/65R14.
205(8.2")/45(45% of 8.2"=3.69"x2=7.38") R17(+ a 17" wheel)=24.38" = 205/45R17. and it works like that! enjoy!

First, the width (in the example: 185), is the SECTION WIDTH, not the tread width. The section width is the width at the widest part of the tire excluding ornamentation, such as lettering and curb ribs.

There are many tire size calaculators on the web. Find a search engine and type in "tire calculator". These calculators work pretty well for camparing overall diameters

BUT!!!!

Word of Caution: Most calculators make the following assumptions which are not 100% true:

1) The nominal section width is exactly what the size says it is.

2) The nominal aspect ratio is exactly what the size say it is.

3) The revolutions per mile can be calculated from the overall diameter using Pi r squared. - actually this needs to be reduced by 3%.

4) All tires of a given size are built to the same dimensions.

AND back to the issue:

In addition to the diameter, the load rating needs to be considered in selecting tires. A P195/70R14 has a load index of 90 or a load carrying capacity of 1312 # at 35 psi. (Note: Tires without the P in front will be slightly different)

That means a P215/50R17 is OK because it has a load index of 90, but a P215/45R17 is not.

Hope this helps.

well thats cool...
I hadn't thought of that, which makes sense to add in the different manufactures, then the different load ratings, and maybe even traction ratings aswell.
Ive posted it in another segment of the forum, but with my automatic transmission, well I hate it. My vehicle has only 114k, and has been well maintained, so it's a strong motor. I would like to swap that tranny with a manual transmission... it might be a big job, but Ive thought it through and so far, I reckon I can do it within a single weekend, that's if I have all that I need, tools and assembly units. if you know more than I do on this, please look for the thread I started lastnight and help me out! thanx!

does the load rating refer to the max carrying capacity of the tire?

The load index indicates to the maximum load carrying capacity. However, the inflation pressure that this capacity is achieved at may vary depending on the type of tire it is. Normally passenger tires are "Standard Load" and the maximum load is achieved at 35 or 36 psi, but there are some expections. "Extra Load" or "Reinforced" tires use 41 psi. These will be indictaed on the sidewall.

Hope this helps.