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John ED Renstrom
07-27-2017, 01:35 AM
I have done a lot of tire swapping and have a whole batch of NOS stuff. time to find out what I have and don't have. so we found a good crack cut into the driveway to measure from. drew a straight line across the tire and rolled them out. now lets pretend we had them all mounted on correct wheels with the correct amount of air in them. even though the only tire mounted was the 235 it was flat. the n78 x 15 did roll out bigger the all the rest. the 235 was the shortest. but I did not expect the 820 -15 to be bigger. then the l78 I knew was going to be just a bit shorter, as I have them on my 72. were this is not exact it will give you and ida which tire not to buy.

John ED Renstrom
07-27-2017, 11:13 AM
got to tired to post more last night. when you start nodding off at the key board it's time to quit.

teh tires size marked out by this chart are n78x15 M&S off brand name. 820x15 BF Goodrich, 890x15 Uniroyal' L78x15 Kelly Springfield, &00x15 Mohawk, and the 235x15R is a Continental.

of note is that if you did the same comparison of the roll out of a tire the same size in a different brand you would get different measurements. this is why it is so impotent to keep the same brand of tire on the the drive axle of a car.

a fine example of this is the difference in the size of the 890 US Royal and the 890 Uniroyal. it is noticeable. but that one was the spare so it not around to compare roll out.

I was never impressed with the two ply side walls, so we picked up the Ls to swap then out on the 72 but hate to give up the duel WW that were standard on the car. do you keep the sub standard tires that look cool or got to a heaver one that are just OK. will it all depend on is your sitting in the garage or driving a distance.

here is a standing shot to compare how tall they are to each other. the far left one is the US Royal

Kurt Arends
10-02-2017, 08:43 PM
Ed,
I believe this one may be the original spare from my '75 S&S Victoria 3-Way. It is a Firestone NR78-15. Load range D rated at 2500 lbs. Fully inflated stands right at 30" tall.

John ED Renstrom
10-02-2017, 10:34 PM
the N78 was the 890 replacement when they went to the letters. that 75 CB I had came out with L78 according to the tag on the door so you might be right. the one N78 here is a direct match for the 890 same tread pattern and all. they should be a 31 inch diameter tire.

Kurt Arends
10-02-2017, 10:35 PM
This one is an NR78, not an N78. This is a radial.