Size does matter (with tires) - Fiberglass RV


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Old 07-04-2010, 09:38 PM   #1
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I always wondered why it was a b**ch to get tires off the hubs and out from under the wheelwells of my 13' Scamp. Jacking my poor trailer so high and really wrestling the rubber donuts out from under the body fender of the wheel well, I now know that while you think the tires you buy fit even if they're not stock, you better measure twice & buy the right freaking size.

The tires that were under my Scamp when I bought it back in '07 finally dry-rotted themselves into oblivion, and I've yanked them out to get new. That was when I realized that the two P185/80 R13's under the trailer are no match of the P165/80 D13 spare hanging under the back window.

It's obvious that whoever put tires under this Scamp before me, probably settled for what the guy at the tire store had in stock that was the closest to what he really needed. Yeah they fit, just barely.

Or maybe it's that he enjoys next to impossible tire changes in the middle of a lonely stretch of road because you can't jack your trailer high enough to get your flat out from under your wheel well. (There...I said it... it's out of my system...time to move on...)

While we're on the subject, anyone have problems finding P165/80 D 13 tires nowadays? I figure I'll be finding out pretty quick on way or another.

...betcha it's a "Jesus" Tire...the kind that makes you say "GEEEEEZ..... when you find how rare & pricey they are!

BTW, the wheel bearings looked great but I've repacked them anyway.

With grease under my fingernails,
ConwayBob
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Old 07-04-2010, 09:42 PM   #2
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Old 07-05-2010, 07:26 AM   #3
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Bob, the only thing worse than wrestling an oversided tire out from under an under-sized wheelwell in a rainstorm on a dark, lonely country road is finding out that next, you have to cut the wheelbearing off with a hacksaw... I've had some really fun trailering experiences... please remind me why I enjoy trailering so much????

Roger
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Old 07-05-2010, 08:15 AM   #4
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Now I know why Roger wasn't concerned about the tire clearance on the Bigfoot 15B17CB he sold us. He probably had seen worse on one of his previous trailers ;-)
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Old 07-05-2010, 09:54 AM   #5
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One of the things that no-one seems to recognise is how much tyres (sorry, tires) contribute to aerodynamic drag. Vehicle drag coefficients are always quoted for the base model as it's common for larger-engined models to have a coefficient 10% worse - from a combination of just wider tyres and a bigger radiator. Changing my little toy car (a Mini) from 175 to 195 tyres dropped it from 40mpg to 38mpg.

There may be good reasons for having a bigger tyre, but it's worth remembering the penalties too - folks are hooked on the idea that anything that contains a bigger number just must be better than anything with a smaller one, but it's often untrue.

Andrew
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Old 07-05-2010, 10:08 AM   #6
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Been there, done that. Link to my post on Tires:
http://www.fiberglassrv.com/board/index.ph...st&p=275043
Plus a second one a few down.

Explaining why I went with a Carlisle ST165R12

If you are still running the original axle, replacing your axle might give just the lift you need.
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Old 07-05-2010, 12:39 PM   #7
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Old 07-05-2010, 09:27 PM   #8
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Changing my little toy car (a Mini) from 175 to 195 tyres dropped it from 40mpg to 38mpg.

Andrew
If you kept the same aspect ratio but just went with wider tread then you actually increased the diameter of the tire. If that's the case, then your MPG may not have actually suffered if you haven't adjusted your odometer to reflect the change, since you're actually travelling further than your odometer gives you credit for.

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Old 07-06-2010, 06:42 PM   #9
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I always wondered why it was a b**ch to get tires off the hubs and out from under the wheelwells of my 13' Scamp. Jacking my poor trailer so high and really wrestling the rubber donuts out from under the body fender of the wheel well, I now know that while you think the tires you buy fit even if they're not stock, you better measure twice & buy the right freaking size.

The tires that were under my Scamp when I bought it back in '07 finally dry-rotted themselves into oblivion, and I've yanked them out to get new. That was when I realized that the two P185/80 R13's under the trailer are no match of the P165/80 D13 spare hanging under the back window.

It's obvious that whoever put tires under this Scamp before me, probably settled for what the guy at the tire store had in stock that was the closest to what he really needed. Yeah they fit, just barely.

Or maybe it's that he enjoys next to impossible tire changes in the middle of a lonely stretch of road because you can't jack your trailer high enough to get your flat out from under your wheel well. (There...I said it... it's out of my system...time to move on...)

While we're on the subject, anyone have problems finding P165/80 D 13 tires nowadays? I figure I'll be finding out pretty quick on way or another.

...betcha it's a "Jesus" Tire...the kind that makes you say "GEEEEEZ..... when you find how rare & pricey they are!

BTW, the wheel bearings looked great but I've repacked them anyway.

With grease under my fingernails,
ConwayBob

We had the original tires on our 81 Boler.As we are planning a loooooong road trip this summer we knew we would have to replace the tires.That said I wanted to put the best tire available on.Maybe a Maxis,heard they were great,or why not Carlise,good reports on them,and oh ya don't forget the Marathons.Well guess what,not one of the tires i considered were available in the 165 size.All started at 175.Really considered getting that anyway cause heck it would not make that much difference would it and would probably be an improvement cause bigger is better.....NOT......After one tire was installed we found it a really tight fit which might lead to rubbing.We were finally able to get a tire in the 165/80D13 range.It is made be Dee Stone tires.$97.00 per,Total 232.10 for 2 tires and a spare installed. They look great,fit great,and ride great.I never heard of this brand but I am perfectly satified with the purchase . Pat.
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Old 07-06-2010, 11:06 PM   #10
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Quote:
Explaining why I went with a Carlisle ST165R12
Oops, got a PM giving me a heads up I may have messed up on size. Yep, went out and looked and sure enough I've got ST145R12 tires on my trailer.

And that is what my original post says. It goes to show you how closely people read what we write. Thanks for the correction. My apologies for any confusion.
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Old 07-07-2010, 04:35 PM   #11
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After a couple of days I've got to report that the largest tire dealer in Myrtle Beach...(Blacks Tire)... does not have 165's (trailer tires). Has 175's for $56/each. Funny, I mentioned I might go check out Camping World...the guy sez "Don't bother...they order from us." I felt like a canary staring down a hungry housecat. I walked out.

Look, I gotta know...is it safe to use tires rated for passenger cars or what...I can't seem to get a straight answer from these tire stores.
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Old 07-09-2010, 09:24 AM   #12
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Bob H,

ST tires are recommended. If you are forced to buy P or LT tires, be sure to get an appropriate weight rating maybe 20-25% over the weight each will carry. All the info is printed on the sidewall of the tire and you can read it before you have new tires installed. Specs are probably more important than brands. The advantages of ST tires are supposed to be better UV protection and stiffer/stronger sidewalls. Those advantages may be a little "iffy". As for safety, you don't have to read these forums much to realize that tires are problematic. Don't buy the cheapest tires! BYW, I run Goodyear Marathon STs.

Bob B
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Old 07-09-2010, 09:45 AM   #13
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Have you considered reradiusing the wheel opening. You could simply copy the same radius ,only out an inch or so... Or you could change the shape for a unique look, like tapered toward the back or squarish like a 49 Merc. The squarish look is really classy. At any rate, a reradius will give more clearance and a much fresher and newer look to your trailer, while allowing space for a better tire size.
The heigth from rim difference between a 165 and a 175 tire is only eight mm, and since a new tire has 11/32 tread depth the difference between a new 165 and a worn 175 is negligible.
Your difficulty is innate to the trailer to some degree, and is exacerbated by age and axle wear.
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Old 07-09-2010, 01:59 PM   #14
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Floyd ,y thoughts exactly... about the axle. It's 27 years old unless it's been replaced and if it hasn't it probably should be. Changing tire size is only a band aid.
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