The cost of 14 inch tires is getting a bit pricey( and tough to find) so I have been thinking all winter about going to 15's. My thoughts/concerns are these: I will have to adjust speedometer ..... are parts available if the cable brakes or I need to change speedometer? Will my current original hubcaps fit the new rims? Will larger tire raise car any? ( great if it could)
I have a 64 88 and I would like it to ride a tad higher. ( I installed dual exhaust without changing the manifold so the pipe sits low!) Lastly is it worth it...I figure 15inch tires will be a bitch to buy 4 years from now!
Thanks for your ideas

 

Measure the outside diameter of your tires and buy a 15" that is the same overall height or a little taller if that is what you want, i.e. make up for the increase in rim height with a decrease in sidewall height so you work out about the same. Your hubcaps won't work.

 

Once again, the WHEEL diameter is unrelated to the TIRE diameter. The speedo only cares about the tire diameter. As noted, if you select 15" tires with the same O.D. as your 14s, there will be no change. This used to be called the "plus one" method of tire sizing. Usually if you go up one inch in wheel diameter and down 10% in aspect ratio, the O.D. is close enough. For example, on my wife's Civic, the stock tires were 175/70-13, but optional tires were 185/60-14 and 195/50-15. All were about the same O.D.

 

Nobody has addressed the hubcap question. I do not see how 14" wheel covers will fit on a 15' rim?

 

I previously said that the hub cap wouldn't work, assuming its a full size wheel cover.

 

try this site hope it helps
http://www.1010tires.com/Tools/Tire-Size-Calculator

 

I just wrote a simple formula in Excel to let me compare sizes, and I don't need to enter the PITA security code every time.

Note that these numbers are theoretical. A tire is not rigid and the actual diameter and section width will depend on air pressure and rim width. In addition, since the tire deflects under load, the dimension that matters for speedo calibration is not the theoretical diameter (or radius) but the actual rolling radius, so the percent speed difference shown on the website above is not accurate. Tire vendors for large truck tires actually provide rolling radius, or the analogous revs-per-mile number.

 

I always use this calculator:

http://www.discounttire.com/dtcs/infoTireMath.dos

 

Same math, same answers. Unfortunately, it also does not (and cannot) provide the LOADED rolling radius, which will change the revs/mile number that this website provides. These numbers will always be only estimates. So long as one understands that, any of the calculators use the same math formula - which is extremely simple:

For answers in inches, the formula is:

(section width [in mm]/25.4*aspect ratio/100)*2+wheel diameter = theoretical overall tire diameter

As an example, for a 235/70-15, we get

235/25.4=9.25" section width converted to inches
9.25*70/100=6.48" sidewall height (70% of section width for a 70-series tire)
6.48*2=12.96 (there are two sidewalls)
12.96+15=27.96" overall outside diameter (sidewall height x 2 plus wheel diameter)

 

No but it's a simple way to get close enough based on like assumptions to make a rational decision. There are also differences in dimensions between manufacturers that one does not consider when doing these formulas.

 

Hey everyone great suggestions and directions. In the end it does come down to money; do I want to buy four new rims and four new tires and then find decent looking hubcaps or do I spend good money on two new 14inch tires. I may as I stated at the beginning be delaying the obvious....sooner or later I will have to go with 15inch. I am curious, assuming I purchase the 15" do I get a better ride and performance? If I do that may be the final nail in the 14" tires so to speak. Again thanks for all the responses.

 

If you select 15" tires with the same outside diameter as your 14" tires, they will have shorter sidewalls. This means that ride will be slightly stiffer (some people, like my wife, would call that "worse" ride) and handling will likely be slightly improved due to less sidewall flex. It's questionable as to whether you will actually feel this difference, however the "butt g-meter" (which is about as well calibrated as the butt dyno) will likely tell you there's an improvement.

(In case it's not obvious, that last sentence has [SARCASM][/SARCASM] tags)

 

I can get 14inch tires at small fraction over cost local
sending you pm
Happy Easter