tire sizing - Fiberglass RV


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Old 11-05-2006, 02:28 PM   #1
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I'm looking to buy a U Haul. It has bad tires after sitting six years. The old tires are six ply 4.50 X 13. Try looking those up! Seems they changed sizing methods twice over the years. Does anyone know what the new tire size is??
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Old 11-05-2006, 04:02 PM   #2
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I think this type of old size tire has a 90 aspect ratio (sidewall height is 90% of the section width), so a 4.50 x 13 would be something like a 115/90D13 in modern sizing (I'm guessing they're bias-ply). Someone else may have the authoritative answer in a more current sizing system, and some helpful U-Haul owner can probably provide the express route to exactly the size and type of tire that work, but here's another approach:
  • check the overall diameter of the existing tires
  • examine the wheel wells for clearance, to determine how much larger (in width and diameter) you can go
  • select a modern tire of a decent size (i.e. wider!) which will fit properly; it will have a lower aspect ratio (likely 80), and the load carrying capacity must be checked
  • get wheels of the right width for the selected tires
  • find wheels of that size which fit a U-Haul (you have my sympathy...) if the current ones are not suitable
  • tow on a good tire setup!
I doubt that this exact size will exist by any other designation, since tires this small are still sold using this old size specification system. The smallest routinely available Special Trailer tires with current sizing specifications are around 175/80-13, which is a much wider and significantly taller tire; trailer tires without the "ST" designation, using the old width x wheel diameter sizing system only seem to appear in wheel sizes up to 12", so I can believe that the 4.50 x 13 is hard to find.

Seriously, while 4.50 x 13 trailer tires are probably still available from somewhere, that's a 4.5" wide tire. I doubt anyone would drive a car twice the weight of a 13' U-Haul on four of them today, so why use two of them on the trailer? As I recall earlier Fiber Stream tire discussions, this is even narrower than the 4.80 x 12 which was stock on that trailer, and with its tandem axles it uses four of them!

For comparison, the original tires for Bolers circa 1979 is B78-13, a generally obsolete size which is still available; however, I think most people now use a 175/80R13 for them. One supplier lists the B78-13 as 24.7" tall; much bigger than a 4.50 x 13, which I think would be about 21.1" tall. The 175/80R13 might still fit, and passenger car tires are readily available in sizes such as P175/70R13 (that's what's on my Civic today), which would be shorter (about 22.6"), and very close to the 4.50 x 13 diameter.
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Old 11-05-2006, 08:54 PM   #3
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I guess I should ask U Haul owners what size tires are you running with?
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Old 11-05-2006, 11:23 PM   #4
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The tire choice issue is not trivial, and it has been discussed here quite a bit, such as in the topic Auto/Truck tires on 13 ft. Scamp?, Bias or radial?. Even in that one, I'm not sure the definitive answer for 13' U-Hauls is given, so it would be good to hear from the other U-Haul owners - there are at least 7 U-Haul owners in the forum, and a few must have 13' trailers.

The reason for my comment about finding wheels is that U-Haul used an unusual hub size - see the topic tires n rims, 14 inch. In that one, it seems that some were using 13" wheels, and other 14", but it's not clear to me what the stock tire size was, or what it was replaced with in 13".

A couple of U-Haul owner reports from the "tires n rims" topic:
  • Jeanne and Steve's 1985 13' U-Haul apparently had 5-1/2" or 5-1/4" wide stock wheels; it seems unlikely to me that they ever had 4.5" wide tires on them! The tires were ST175/80R13, 24" tall.
  • Tom Stewart's 1984 U-Haul had 7.00-14LT tires on non-stock Weld Racing rims - maybe that's a bigger U-Haul model.
In the end, if the concern is whether or not tires would be available for this potential trailer purchase, I wouldn't worry about it. Something reasonably priced will likely fit, so I would budget for a set (that's three - remember the spare!) of tires (no new wheels), and concentrate on assessing the less readily replaceable parts of the trailer.
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Old 11-06-2006, 07:41 AM   #5
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I have to travel 600 miles to pick up this trailer that has bad tires. I thought I'd just buy two tires with rims. That way I could just pop them on and not have to worry. I have a fast turn around time and wanted to leave town 12 hours after arriving. No time for shopping locally, then have to tow the trailer in and get tires mounted.

It looks like the tires aren't my only problem. Thanks Brian for leading me to a post that gives me info on the hard to get rims I need first! Thanks fiberglassrv.com for having the U Haul parts manual available, confirming the info I read in another post.

I usually run Goodyear Marathons on my trailers. They have served me well with my other campers.

Quote:
The tire choice issue is not trivial, and it has been discussed here quite a bit, such as in the topic [b]Auto/Truck tires on 13 ft. Scamp?, Bias or radial?. Even in that one, I'm not sure the definitive answer for 13' U-Hauls is given, so it would be good to hear from the other U-Haul owners - there are at least 7 U-Haul owners in the forum, and a few must have 13' trailers.

The reason for my comment about finding wheels is that U-Haul used an unusual hub size - see the topic [b]tires n rims, 14 inch. In that one, it seems that some were using 13" wheels, and other 14", but it's not clear to me what the stock tire size was, or what it was replaced with in 13".

A couple of U-Haul owner reports from the "tires n rims" topic:
  • Jeanne and Steve's 1985 13' U-Haul apparently had 5-1/2" or 5-1/4" wide stock wheels; it seems unlikely to me that they ever had 4.5" wide tires on them! The tires were ST175/80R13, 24" tall.
  • Tom Stewart's 1984 U-Haul had 7.00-14LT tires on non-stock Weld Racing rims - maybe that's a bigger U-Haul model.
In the end, if the concern is whether or not tires would be available for this potential trailer purchase, I wouldn't worry about it. Something reasonably priced will likely fit, so I would budget for a set (that's three - remember the spare!) of tires (no new wheels), and concentrate on assessing the less readily replaceable parts of the trailer.
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Old 11-07-2006, 08:21 PM   #6
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Unless a previous owner changed out the hubs, it's unlikely that you will find a rim that fits without some homework and careful searching (see current thread on this) -- Apparently, UHaul equips all their trailers with non-standard running gear to deter thieves from renting a trailer and then swapping out good stuf for bad.
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Old 11-13-2006, 01:09 PM   #7
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Just to let you know, the trailer I bought had the original 1984 U Haul rims and U Haul branded tires on it. I had a tire company come out to the site and mount brand new
ST 175/80/13 tires, 6 ply. The diameter is the same as the original tires, 24 inches. Tows like a dream.
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Old 11-13-2006, 01:50 PM   #8
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Quote:
...The diameter is the same as the original tires, 24 inches...
It seems that the originals must not have been 4.50 x 13, as first thought, since it is extremely unlikely that a 4.50 inch wide tire would have 5.5 inch sidewalls.
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