One last tire question

T

tparrent

New member
Out of an abundance of caution, I went to the boat yesterday to check the tires one more time before ordering new ones.

The lettering on the tire at various places was K550 Load Range D ST 225/75 D 15

I then measured the rim diameter. Edge to edge, the measurement was 16 inches, not 15.

Now I have learned that dimensions are not always obvious as in lumber 2x4s so I wondered if I was being a fool for actually measuring the actual, real, undeniable diameter of 16 real world inches when I've been assuming these are 15 inch tires.

Am I missing something here?

I'm thinking about going to a store that selss tires on rims and measuring a wheel labeled as 15 inches to see if it really is.

As always, thanks for your help.
 
If the number you give is mounted on your rims and that is what you have been using they are 15 inch.

My 14 inch measure 15" out the outside but that isn't where you would measure it. You would measure the inside dimension of the flange and it won't be exact.
 
I think the tire/ wheel diameter is not measured on outside. the wheel is flanged both inside and outside otherwise the tire would fall off. There is undoubtedly 1/2 inch of tire all the way around that you can't see, hidden by the flange. What tires are on there now? don't overthink it:)
 
I am surprised at the "e" trailer example, because it is misleading. Like Jody and several others, I have 14" tires on 15" rim--In hour case it is approximately inside bead of the tire. You have a 15" tire, and that is what you need to replace it with.
 
Does anyone else think it's bizarre that the tire measurements are part metric and part English?

Thanks to all the responses, I now know what I need. Probably.
 
Tom, my friend, if those tires are holding air, hook up drive slowly to the nearest tire shop (I have had very good service from Discount Tire) and have them mount up the appropriate tires. No guessing, no fussing, no measuring, no jacking up a trailer, no trip to the emergency room. Give them a credit card, and in about an hour, you will be driving away with new tires.

Then, go enjoy your retirement. You might find that 22 is all the boat you need for you and occasionally, you and Spike.

Have I ever given you bad advice? Have you ever taken the aforementioned advice? This is a good time to start. :wink:

Best wishes,
Jim
 
Steel rims have a 1/2 lip to hold the bead. Aluminum are sometimes less.

If you look at something other than trailer tires and the C, D type ratings used on ST tires, you will see that tire width and aspect usually effects the load rating for each vehicle tire size. Aspect will effect diameter and width and, within reason, can determine whether the tire will fit under your fenders. Also, non-trailer tires are available in High Load (sometimes just saying "HL") and low rolling resistance. Low rolling resistance is usually a function of standard air pressure (usually +50-60 psi), which again tends to increase load ratings.

I went from 13" galvanized steel wheels with skinny trailer tires to 15" aluminum wheels with wider high load, low rolling resistance all season tires, so I went through all of the secret tire-language gobbltigook. I'm almost fluent.

Mark
 
Against all my better instincts, I took Jim's advice and went to Discount Tire and verified they have tires in stock. The guy told me a bunch of stuff and I asked him which tire I should buy. He picked one and that's what I'm going with!

I'm bringing the boat over on Friday to have them installed.

Now if anything goes wrong, I'd never blame Jim - but I would liberally and creatively quote him in the story of the disaster! :D

The weather has been fantastic here and I am so tempted to get on the water but I'm resisting until I get that old gas pumped out.
 
I'm OK with being quoted, Tom... especially if it keeps you from being crushed under a boat trailer. :wink: Not knowing what gas you put in the boat before not using it since the turn of the century, I think pumping out the old stuff and perhaps replacing fuel lines is probably a good move. I'm guessing your motor has a carb, not fuel injected, so you may need a carb rebuild, as well.

Then, one last bit of advice: use it. Frequently. Best thing for a boat. But, since you have owned 361 boats since we first met, you probably know that. In the words of the philosopher Nike: Just do it!

Let me know if I need to come east and spend a week or two with you... that ICW stuff is a bit different from sailing in the Great Lakes.

Best wishes,
Jim
 
"One Last Tire Question." There is no such thing as one last tire question. This site and every trailer related site, RV or boat has long long long lists of tire questions. I just had to chuckle at the title of the post. We all have tire questions come up every year. How is it that something that is just round an rubber can be of so much interest to us all?
 
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