...I'm getting a headache....numbers numbers everywhere...

(This is almost fun)

What I might end up doing is either running the 13" tires presently on the car to the ground (shame, really, since the tires are almost new, since I've yet to put 100 miles on the car since I got it - last year(!)), or sell the rims with the tires and get a new/fairly good used set of rims with new tires.

Whatever I do, I'm printing out this entire page to take the several tire shops in the area (Firestone, TireRack - their webpage won't give me info on the '70 240Z), and see which is the first one with mechanics who seem to know what they're doing, and go from there.

Brandy,

I'm reading and reading, and then I linked over to have a look at Ruby, and I have some basic confusion. Lets get some terminology straight, first. The wheel is the round metal thing that bolts on to the car. The tire is the rubber stuff filled with air that goes around the wheel. Wheels on a stock 240Z are 14" in diameter and 4-1/2" wide. Datsun 240Zs never had 13" wheels. Ruby looks like she already has 14" wheels. Go measure the diameter. 14" wheels are not very common any more and most people are buying 15" diameter new wheels to fit the Z. Used 14" wheels are quite common and Ruby will fit into a size 4-1/2" to 6" width without any problem. She could also wear a 15" wheel in those widths without any big deal. In used 14" wheels, some of the hottest fashions are "slots", "ARE Libres", and "Watanabes" in my opinion.

Now lets talk tires. The stock tire was a 175 /60SR14, but that isn't made anymore. 195 /60SR14s replace that old size and fit best on a 4-1/2" wide wheel. If you go over to the Tire Rack site, you can read about the size of the tire versus the width and what all those numbers mean. Check this site out also. http://www.powerdog.com/tiresize.cgi Keep in mind that Ruby's speedometer is set up for the original 175 size tire on a 14" diameter wheel and the resultant overall diameter. You want to stay as close to that diameter as you can. Around 22.3 inches.

So if you go with a larger diameter wheel, you will want a lower profile tire. Wider wheels will demand a wider tire. Have fun.

The wheels on "Ruby" don't look like factory wheels. They apear to be aftermarket wheels. I don't know about people in FL, but back in the day, a certain number of CA owners did put 13" wheels on their Z's for some unGodly reason that I have no clue about. Tire Size ( and thus wheel diameter) is easy to confirm, it's printed all over the the sidewall of the tire.

Another question, what is the difference between W and Y rated tyres?

Thanks, Justin

  Greatwhite said:

Another question, what is the difference between W and Y rated tyres?

Thanks, Justin

Speed Rating

The speed rating denotes the speed at which a tire is designed to be driven for extended periods of time. The ratings range from 99 miles per hour (mph) to 186 mph. These ratings are listed below.

Note: You may not find this information on all tires because it is not required by law.

Q 99 mph H 130 mph

R 106 mph V 149 mph

S 112 mph W 168 mph*

T 118 mph Y 186 mph*

U 124 mph

*For tires with a maximum speed capability over 149 mph, tire manufacturers sometimes use the letters ZR. For those with a maximum speed capability over 186 mph, tire manufacturers always use the letters ZR.

Quote from safercar.gov

Chris

Hi all,

my question is the following

i have bought 16x7 koning wheels for my car, and i want to install the following tire size: 225/50/16, does anybody knows if this size will work well on my car? I will aprreciate any advise

Thanks

  raul35 said:

Hi all,

my question is the following

i have bought 16x7 koning wheels for my car, and i want to install the following tire size: 225/50/16, does anybody knows if this size will work well on my car? I will aprreciate any advise

Thanks

Yes, they will work, but you might, or might not have to roll your rear fender lips a bit. I have the same size tires on Panasports and they rub just a bit. Some people report a rub with that size and other don't. The interference is very minor which would explain the different results.

  26th-Z said:

Now lets talk tires. The stock tire was a 175 /60SR14, but that isn't made anymore. 195 /60SR14s replace that old size and fit best on a 4-1/2" wide wheel. If you go over to the Tire Rack site, you can read about the size of the tire versus the width and what all those numbers mean. Check this site out also. http://www.powerdog.com/tiresize.cgi Keep in mind that Ruby's speedometer is set up for the original 175 size tire on a 14" diameter wheel and the resultant overall diameter. You want to stay as close to that diameter as you can. Around 22.3 inches.

I want to make sure this is correct? In my glove box it reads 175HR14 or 6.45H14. Cause if this is the case, my 205/60/15 tire is running about 9% slower than OE. So that means if my speedo reads 65mph on the freeway, in actuality I'm only doing about 59mph. I'm going to drive faster if that is the case

Will the variance effect my braking ability? Our cars didnt come with ABS right?

Actually, the difference is about 1% (revolution per mile basis), not enough to worry about.

I hope you're joking on the ABS question. Next you'll want to know how many airbags are installed, right?

Stock Tire - 175/60R14 >

Tires Tire 1 - 205/60R15 >

Section Width: 6.88 in 175 mm

Section Width: 8.07 in 205 mm

Rim Diameter: 14 in 355.6 mm

Rim Diameter: 15 in 381 mm

Rim Width Range: Unrecognized tire size.

Rim Width Range: 5.5 - 8 in

Overall Diameter: 22.26 in 565.40 mm

Overall Diameter: 24.68 in 626.87 mm

Sidewall Height: 4.13 in 104.90 mm

Sidewall Height: 4.84 in 122.93 mm

Radius: 11.13 in 282.70 mm

Radius: 12.34 in 313.43 mm

Circumference: 69.93 in 1776.2 mm

Circumference: 77.53 in 1969.2 mm

Revs per Mile: 934.4

Revs per Mile: 842.7

Actual Speed: 60 mph 100 km/h

Speedometer1: 54.1 mph 90.1 km/h

Speedometer Difference: - Speedometer Difference: 10.88% too slow

Diameter Difference: - Diameter Difference: 9.81%

  bavarian06 said:

Stock Tire - 175/60R14....

Wrong. The stock size is/was (the now obsolete) 175SR14 or 175HR14 (depending on year). That is equivalent to 175/80-14 in today's sizing, not 175/60-14.

  Arne said:

Wrong. The stock size is/was (the now obsolete) 175SR14 or 175HR14 (depending on year). That is equivalent to 175/80-14 in today's sizing, not 175/60-14.

Thats why I was asking for clarification if what 26th-Z posted is correct. Read my original post with the quote. Ok, good to know its 175/80/14, thx!