Best "performance" tire for a 70 240z

[w3wilkes]

Mathew, WOW! What a nice table, thanks. I'll just have to remember that per your table with my 205/60 R15's that when my speedo reads 100 MPH I'm really only going 98.63 MPH. I call that "close enough". I'm guessing that you used 82% for this final version of the table? I will mention that I have the same original unused spare tire as Mike. I may be a lousy measurer, but I got 25.125" inflated to 25 PSI so Mike and I are less than .05" different.

 

[Freez74]

Thanks for posting the chart, very useful information!

[CanTechZ]

Here is a very good tire data calculator that does comparisons as well.  Requires more inputs, but it gives back a lot of information like the basic tire spec plus static and dynamic rolling radius, contact patch size, stiffness rate, speedo reading, etc. all based on input speed and air pressure and vehicle load.

http://paws.kettering.edu/~amazzei/tire_calculator.html

It does use metric system inputs and outputs but lower down the page there are some useful unit convertors as well as other tire related information.

[Matthew Abate]

I used 80% for the table because of that Michelin I found, but I can easily make a copy in other ratios. 634mm comes to 24.96” in diameter. I assume that different brands will get you different diameters, but the .165” difference between these and the Michelin is less than you lose before buying new tires so ¯\_(ツ)_/¯.

 

 

Sent from my iPhone using Classic Zcar Club mobile

 

[Matthew Abate]

In related news, Yokohama just brought back its 1981 Advan HF Type D tire: https://jalopnik.com/yokohama-brings-back-a-1980s-tire-so-you-can-make-your-1819844548

 

I would LOVE to get my hands on a set of these, but they seem to be JDM only.

[Robert Bohl]

Matthew, many thanks for the tire size chart.  This discussion got me interested in checking the tires on my 1971 240Z as they may be overdue for replacement; although the cars' Goodyear Eagle +4 (195/70R14) tires look brand new and handle well, they were installed in 1990! 

I always felt that the engine's RPMs at cruise had increased since replacing the original Toyos with the Goodyears, so I measured the circumference of my never-used OEM spare, a Toyo Radial Z-1 175HR14 inflated to 35 psi.  The measurement was 80.25", which if my calculations are correct yields an aspect ratio of 84, slightly higher than the other measurements in this discussion. 

In any case, the high RPM mystery has been solved, and I may choose new tires that are closer to the diameter of the Toyos.  This leads to the following question, would it be possible to upsize to a 205/70R14 without any clearance problems on a '71 240Z?  I have 7" ARE wheels and a stock suspension.

Edited October 5, 2018 by Robert Bohl

[jakay11]

The tires currently on my series 1 240Z are from roughly 1980 are more square than round... and I don't even want to think of internal dry rot...

So being the retired engineer (I now sell real estate) I created this tire size grid to match up rolling diameters across wheel sizes (+0, +1, +2, ect)....
Also from my Porsche days I have found and used the tire size / speed calculator as well... (Both attached).

So assuming 195/70R14 is the stock tire on 5" rim w/ 15mm offset.  (and there are differences between mfg on rolling DIA, but lets ignore that for now)
Browsing online, there aren't many options at all for a tire of this size.  So the question becomes to goto a 15" or 16" rim... on a 7" or 8" wide rim on either...

Putting something like a Pirelli Trofeo R seems, well stupid, if your not tracking/autocrossing this car... so what do people like these days that doesn't over-tire the car and destroy the handling?

• 205/60R15 on a 15x6" or 7" rim (30 options on tirerack)
• 205/55R16 on a 16x6" or 7" rim (148 options! plus 3 addl track tires like the Trofeo R)
• 225/50R16 on a 16x7" or 8" rim (42 options plus 12 addl track tires)

So the question is do I stick with something like the 60-series on 15s and risk them becoming harder and harder to get, or do I go for the 50 or 55-series on 16s and run the risk of the ride/handling going to crap?
Further muddying of the water is that the current Miata and Toyota GT86 run basically economy tires to allow the cars to move around... (My car is basically stock except for period mods - Koni shocks, rear sway bar, and exhaust... all installed by Bob Sharp Racing in '71)

while I was browsing on tirerack and found this... which also may be useful. 
 https://www.wheel-size.com/calc/?wheel1=195-70-14X5.0ET15

 

Tire size.xlsx

Tire&SpeedCalc.xls

[siteunseen]

I have 15s and think they "fit" the 240s best. Plenty of tires available in my searching. Presently running Hankooks from tiresdirect.com.

16s on my 280 because I bought them first. Wish I had 15s on it too. 

[Pmg]

I've got 225/50/16 on an 8" zero offset and I think the fit is perfect on a non-flared s30.

[Jeff G 78]

4 hours ago, Pmg said:

I've got 225/50/16 on an 8" zero offset and I think the fit is perfect on a non-flared s30.

Depends on the brand and model of tire.  My Hankook RS-2 225/50R16 tires on zero offset rims rubbed on my car.  The very high performance summer tires tend to have squarer profiles and can rub.

 

Edited December 29, 2018 by Jeff G 78

[LeonV]

If you're limiting yourself to just those sizes listed, 15's are out of the picture unless you'll be driving n the snow.

Taking the 205/55-16 size as an example, sounds like your use-case falls somewhere into the max/ultra high performance summer category. Your comment about "over-tiring" a car tells me you like to go beyond the limit but like for that limit to be low enough that it can be exceeded without "excessive provocation".

Based on experience, good choices are the Firestone Indy 500, BFG SC2, and Dunlop DZ102. All have nice road manners and should match well with your setup and use-case. I run 225/50-16 Bridgestone RE-11A rubber (discontinued, unfortunately) which have fantastic grip but take commitment to get the car loose.

Tirerack does a pretty good job of reviewing tires, I'd recommend watching/reading when available.