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Old 07-21-2007, 08:31 AM   #1
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1968 17' Caravel
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Tire conversions advice, please

Please could anyone suggest to me what tires I need to replace
my perished old Caravel tires. They are 7:75 x 15.
Is there a metric tire that will do the job?
Thanks, Stew
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Old 07-21-2007, 11:35 AM   #2
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Stew---The important thing here is load carrying capacity of the replacement tire. Make sure the sum of the two tire capacities exceeds the trailer GVW by a comfortable margin. A metric equivalent is fine, (ie 205, 215, 225x15). Be sure to check the wheel for road worthiness.
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Old 07-21-2007, 02:23 PM   #3
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I have a 67 Caravel and am also looking for replacment tires. I checked a number of tire conversion charts on the internet. All the charts show that the closest replacement tire for 7.75x15 in the P metric 75 series is a 205/75R15. For sizes in other series (70, 65 and 60) check TireRack.com.

All the ST205/75R15 tires I found are load range C tires which means their rated at about 1,800 lbs per tire at around 45 to 50 psi depending on manufacturer. I can't find a GVWR for the Caravel but my A/S with water tank full weights about 2,600 lbs. Add stuff and the trailer probably comes in at around 3,000 lbs. This means the trailer when loaded for travel weighs in at about 83 percent of the load rating of the tires. This is an acceptable margin for me but may not be for others.

If your wheel wells will accept them, a 225/75R15 carries a load rating of D which is about 2,500 lbs per tire at 60 psi depending on manufacturer. That should provide plenty of weight margin for a Caravel unless your a rock collector. I wonder however, if a tire load rating of D is significantly greater than the rating of the wheel and axle for the Caravel and therefore overkill The wheels on my trailer are five bolt hole steel wheels. I have not been able to find replacement steel wheels in this configuration that exceed a load rating of 1,800 lbs. If anyone reading this knows of 15 inch OEM steel wheels with a five bolt on 4.5" centers pattern that has a higher rating, I'd like to hear about it.

Good Luck.
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Old 07-21-2007, 03:24 PM   #4
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Thanks for that, very useful.
I would also rather fit different wheels if I could find a fit.
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Old 07-21-2007, 03:50 PM   #5
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TireRack are good folks, they will provide all the help you need
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Old 07-21-2007, 06:06 PM   #6
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Try Trailer Tires and Wheels - trailer tires, boat trailer tires, trailer wheels, boat trailer wheels, aluminum trailer wheels for a nice selection of aluminum trailer wheels
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Old 07-21-2007, 07:30 PM   #7
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Lew pointed you in the right direction for 5 x 4.5 aluminium replacement wheels. Some of the aluminum wheels on that site have ratings as high a 2150 lbs at 60 psi. I don't understand why a wheel would have a weight rating for a particular psi. Perhaps they mean that the wheels are rated at 2150 lbs and are robust enough to handle tire pressure up to 60 psi. Perhaps someone more knowledgable of wheel rating could weigh in here. Anyway, If you wanted to go with the higher rated tire like a 225/75R15 the aluminum rims would make more sense since they are closer to the load rating of the tire.

I would point out however, that there have been a number of posts on this forum that suggest that a tire with too high a load rating inflated to the pressure recommended on the tire can be harmful to the trailer. Since the tire is an integral part of the trailer's suspension system, it seems possible that an over rated tire inflated to the full pressure could in effect stiffen the "suspension" and increase the shock impact on the trailer from pot holes and other irregularities in the road.

I suppose it would be possible to underinflate a higher load rated tire but that would seem to introduce its own set of problems. I like the retro look of OEM steel wheels especially painted black with the chrome style hub caps that came with the original so I am planning to stay with the system that came with the trailer. I also noticed that the 1967 Airstream Manual recommends that the 7.75x15 tires in the Caravel be kept inflated to 45 psi. The recommended inflation pressure for the ST205/75R15 is 45 to 50 psi depending on the manufacture. This suggest that these tires might have the same "resiliency" as the 7.75x15 that came with the trailer and perhaps work better with the torsion suspension to maintain the same ride characteristics as the original package from the factory.

Anyway, I think I have beaten this horse to death and I see it is now about 1:30 am Sunday in Greenwich so I don't expect you'll be checking this thread anytime soon. Tires are always a fun topic on the forum let us know what brand and size you finally decide on.
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