This week was tire week. I have never really thought much about tires. I had no idea what the sizes meant. I had a hard time figuring out what tires should go on Isabelle. I had no idea what kind of rims I needed. I spent almost every evening looking at tire specifications and Craigs List, trying to figure out the world of tires.
From the GMC truck service manual for a 1968 Pickup, a 1500 series has 7.35-14 tires.
The closest tire is a 185R14.
Cooper makes a good tire and one place near Seattle that sells Cooper tires is Courtesy Tire. This tire is 25.5 inches in diameter with a section width of 7.3 inches, which is very close to the original 7.35 inches. The tread width is 5.45 inches. A more common tire with a summer, street tread is the Yokohama Y356 185/R14
D available at Tire Rack also locally available at Discount Tire.
The bolt pattern on a 68 GMC is 6X5.5, which just means that there are 6 lugs and the diameter of the circle made by the bolts is 5.5 inches. The current rims I have are quite wide. I'm not sure exactly how wide, but they are way too wide for most tires I might consider. Toyota's sometimes have a 6X5.5 bolt pattern.
Now, the tires that Isabelle has on her are size 245/70R15. These tires have a tread width of 7 inches, a section width of 9.9 inches, and an overall diameter of 28.5 inches. This means the tread width is 1.55 inches wider than the original tires. The sidewalls are cracked, though, even though the tread is OK.
I used to deliver pies in a 77 Chevy Van. I would be on icy roads at 5am going north out of Eugene on my way towards Albany. If I slowed down to around 50 MPH the front wheels would shake until I hit 45. It was quite nerve-wracking, particularly when combined with all the road construction at the time. The owner of the pie bakery told me it shook because the tires were too big for the van. Since Isabelle has manual steering, I'm particularly concerned with getting tires that will work with the steering and front suspension the way they are supposed to.
On the other hand, big tires are fun. Around the same time I was delivering pies, a friend of mine got some big tires for his '61 Ford Pickup:
He would race up and down the alley with his big tires. He was quite happy with them. I don't remember exactly why the alley was the best place to race around with big tires. I suppose there were a lot of potholes.
In the end I decided to use some 225/75R15 tires. I found some 6 inch rims and tires with decent tread on an online board and decided the price was right. I took my son with me to get them. The guy who was selling them lived in the outskirts of Puyallup (which is in the outskirts of Tacoma [which is in the outskirts of Seattle]). The turnoff to the cul-de-sac he lived on was not marked well, so we missed it and had to turn around. He lived in large, new construction house. His wife had told me on the phone that he would be in the shop around the back. We drove around the house to the shop. I got out and peeked in the shop and saw a 60-66 GMC/Chevy truck he was working on. He came around the corner with greasy overalls on. I gave him the cash and he helped load up the tires and rims. We talked for awhile. I asked him about whether he did his own body work, and he said he did. He said that his dad was a really good welder, but he did OK. His day job was as a doctor.
Here are the rims and tires on Isabelle:
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