Radial Tires to Replace Old 7.75-15 Size on Vintage Boat Trailer  

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Expert Reply:

Your vintage trailer's 7.75-15 size tires are probably on the order of 30 years old at this point and this exact size is no longer offered. A close modern equivalent is a 205/75-15 size, which is slightly wider at just over 8-inches and also about 27-inches in overall diameter once mounted. We offer four different 5-bolt wheel patterns: 5 on 4-1/2 Inch, 5 on 4-3/4 Inch, 5 on 5 Inch and 5 on 5-1/2 inch. I have linked an article to help you determine which you have.

We can certainly help you find wheels/tires to replace these but given the age of the trailer it is VERY likely that you will be in for more than just new tires. You will probably need to replace your hubs, bearings, seals, etc. along with the tires and wheels. You may also need to replace your suspension's springs as these do wear out with age. If the springs are rusty you should consider replacing them. Please see the linked article on trailer suspensions.

In order to select new tires, wheels, springs and hubs you will need to know your axle's weight rating, which should be indicated on a sticker or plate on the axle itself. You will also need to pull a hub and obtain the part numbers form the bearings and seals. The linked photo shows the typical appearance of those numbers. It also shows where to measure the spindles (with a digital caliper) in the event you cannot find part numbers.

We also offer complete axle/hub/bearing kits in axle ratings up to 3500-lbs. For example, Dexter offers an axle kit # 35545I-EZ-89 which includes the axle beam, 5-on-4-1/2-inch idler hubs (meaning hubs without brakes), bearings, races, seals, grease caps, wheel studs, lug nuts, and marine-grade wheel bearing grease.

Please let me know your hub/wheel bolt pattern, axle weight rating and bearing/seal information and I will be glad to check for available new parts.

expert reply by: Adam R

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