Datsun Roadster Forum-311s.org

mattywood wrote: I might win a prize for most indecisive 311s member.

Well, I don't know. I think I'd vote for you ... but ... Darn! I just don't know. Let me flip a coin. hmm. Maybe two out three?

mattywood wrote:Going by what you say I should run 60 15s on a 195. I have checked price of 60s and 55s and they are $$$ for a good tyre. I had a look at alvins ride running 195 50 15s and they look fantastic and the tyre I want to run is a Yokohama C drive which much cheaper as a 50 series. Do you see an issue with handling running a 50 vs a 60? I know guys run 50s on 16" wheels in australia. I might win a prize for most indecisive 311s member.

I would run the 195 50 series 15s...I an assuming you are running at least 5.5" rim. I run the 195/60 series x 15" on 7" rims and they rub on hard corners ( that depends on the offset and body mounting). My next tire will be 195/50x15. You car will have more acceleration with the smaller tires by just a bit.

Using the calculator that Fergus gave me and using specs from the Road & Track Survey I came up with the following calculations:

The 5.6o x 14 appears to equal an aspect ration of 73 given that the article quotes a speed of 111 mph @ 6000 rpm for 3.89 final.

Thus

All speeds below calculated @ 4K rpm in 4th gear (i.e. 1.000 to 1.000)

65 x 14 (3.89=70) (3.70=73.9)

73 x 14 (3.89=74.1) (3.7 = 77.9)

I always thought that with original equipment that 1K rpm = 20 mph.


3.89 ratio = 70

mraitch wrote:Using the calculator that Fergus gave me and using specs from the Road & Track Survey I came up with the following calculations:

The 5.6o x 14 appears to equal an aspect ration of 73 given that the article quotes a speed of 111 mph @ 6000 rpm for 3.89 final.

Thus

All speeds below calculated @ 4K rpm in 4th gear (i.e. 1.000 to 1.000)

65 x 14 (3.89=70) (3.70=73.9)

73 x 14 (3.89=74.1) (3.7 = 77.9)

I always thought that with original equipment that 1K rpm = 20 mph.


3.89 ratio = 70

You neglected to compensate for tire slip which will make the effective aspect ratio larger.

So what factor should one add (or multiply) in for tyre slip - given 4000 rpm and approx 70-75 mph

mraitch wrote:So what factor should one add (or multiply) in for tyre slip - given 4000 rpm and approx 70-75 mph

Who knows? I sure its more at 111 mph LOL

DatsunBucky wrote:

mattywood wrote: I might win a prize for most indecisive 311s member.

Well, I don't know. I think I'd vote for you ... but ... Darn! I just don't know. Let me flip a coin. hmm. Maybe two out three?

We could add a poll question, then form a committee