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Old 10-25-2020, 04:20 PM   #1
Rocknoids
 
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Upgrade tires from C to D or to E

I tried searching the forum and found 79 pages of different tires issues.
I have a 2014 FR 8289WS. The Prev. Owner upgraded to ST 225/75R/15 D.
I have a quote from a tire shop to install E rated tires. Is that going to be too stiff? Should I stay with D rated or does it really matter?
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Old 10-25-2020, 04:38 PM   #2
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For a small price difference, you will be safer with good load range E tires. After much tire failure experience, I recommend Carlisle ST225/75R15 E. Don't even think about Titan load range E tires, as they were junk and I failed them in a thousand miles or so.
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Old 10-25-2020, 04:54 PM   #3
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I read somewhere with the E rated tires, the trailers bounced around too much because the tires were too stiff. I am concerned with rattling & shaking the trailer to pieces.
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Old 10-25-2020, 06:28 PM   #4
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We have a 2013 8289 and went with E couple years ago. No issues. Do it.
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Old 10-26-2020, 01:13 PM   #5
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My trailer used ST225/75R15's.
I had 2 blow outs 2 months apart on 3 year old tires.
I was disgusted...and after a lot of research - I was able to go from 15" rims (6 lugs) to 16" rims.
I got LT (light truck) tires vs. ST (special trailer) tires.

I ended up with 20% more 'reserve load' capacity.
I can calculate out tire pressures....and reduce the pressure. For example - going from 60 psi to 45 psi might provide adequate load capacity - and less stiff ride over the 60 PSI. I don't mind a slightly stiffer ride -so I keep the pressure a bit higher.

LT tires have a higher speed rating - and don't seem to become 'BOMBS' after 3 or 4 years from initial installation.

I had to carefully measure - but the 16" tires I added - decreased the separation between tires by about 1" - and I still had 2" before contact. And - plenty of vertical clearance between the top of the tire and the underside of the trailer. Some trailers - no room to go with a slightly bigger tire. BUT - if you have the room - give it some consideration.

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Quote:
Originally Posted by Rocknoids View Post
I tried searching the forum and found 79 pages of different tires issues.
I have a 2014 FR 8289WS. The Prev. Owner upgraded to ST 225/75R/15 D.
I have a quote from a tire shop to install E rated tires. Is that going to be too stiff? Should I stay with D rated or does it really matter?
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Old 10-26-2020, 01:29 PM   #6
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The ST rating tires have a stronger sidewall to handle the torque loads of sharp turns. Our 8528RKWS had "C"s on it, but we are finally good with MAXXIS load range Es. Don't forget to upgrade the valve stems if you decide on Es. I would avoid LT tires for that reason. "YMMV"
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Old 10-26-2020, 01:35 PM   #7
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Are you concerned?

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Originally Posted by vineyardmh View Post
My trailer used ST225/75R15's.
I had 2 blow outs 2 months apart on 3 year old tires.
I was disgusted...and after a lot of research - I was able to go from 15" rims (6 lugs) to 16" rims.
I got LT (light truck) tires vs. ST (special trailer) tires.
Double- and triple-axle trailer tires are subject to huge sideways forces that trucks don't encounter.

Visualize what happens when the truck is turning left and the truck axis is 45 degrees to the trailer axis (moderately sharp turn). Because neither trailer axle turns, the front-axle tires are being dragged sideways to the left and the rear-axle tires are being dragged sideways to the right. In even tighter turns, the situation is worse. Now visualize the truck and trailer at 90 degrees. One hundred percent of the movement is sideways.

ST tires are designed for this sort of abuse. Are you certain that LT tires are?
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Old 10-26-2020, 02:36 PM   #8
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Rocknoids, I wouldn’t be concerned about the rougher ride for Load Range E; Its been 5 years but my 15” Carlisle Load Range E were terrible-lost 2 in less than 5K mi. Sidewalls blew out. Not near as stiff as Maxxis which 2 sets got me by very fine.
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Old 10-26-2020, 03:07 PM   #9
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I put on e rated goodyear endurance 3 years ago and have put on over 10,000 miles on them and they are still going strong. they are better than D rated
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Old 10-26-2020, 03:14 PM   #10
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Just make sure they are made in USA or Canada.
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Old 10-26-2020, 03:26 PM   #11
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Quote:
Originally Posted by Marc G View Post
Just make sure they are made in USA or Canada.


Not all Chinese tires are bad, some of them are better than USA made tires. Also many USA tires are garbage.
Remember most tires get a bad wrap because we under inflate, over load , drive faster than the tire rating.
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Old 10-26-2020, 06:40 PM   #12
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I'm going with the E rated tires.
2 new axles then 4 new tires by the end of the week. Now I start traveling distances again.
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Old 10-26-2020, 07:22 PM   #13
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I went with the Carlisle E tires. They did not change the rate of bounce to any noticeable degree. They have an upper end speed rating that I would never consider approaching, but they give me greater confidence if I ever am in a situation where I have to accelerate to over 65/70. The E tires are really the way to go!!
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Old 10-26-2020, 09:01 PM   #14
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Think of your tires as you do the rear springs of your pickup.

Would they last longer if you kept the truck loaded to its maximum capacity all the time or would they last longer if you loaded the truck to a lower weight?

I will tell you the answer, they will last longer if you load them lightly.

Now consider the tires and the increased load bearing capability. At the same trailer weight they will be bearing a lighter load compared to their capacity.

As for the trailer bouncing around, dampening such bouncing is the purpose of the equalizer system on your two axles.
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Old 10-26-2020, 11:55 PM   #15
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Yes - your miles may vary.....and anyone looking to switch from ST's to LT's - should research the snot out of it. I did - and I am a professional engineer - and I spent many months researching and evaluating before I made the transition.

NOTE - I indicated that my new tires had greater load carrying capacity - and I tend to operate stiffer (i.e. - if each tire is carrying 2500 lbs load - I don't HAVE to inflate to 80 PSI to get 3450 lbs - rated load. BUT I do inflate more than necessary for better overall carrying performance. AND - I am happy with the results thus far....no blowouts in many years.

The 'huge sideways forces' are usually at very low speed when maneuvering to get into or out of a trailer site. Not frequent and always at low speed.

BTW - watch this video - and jump to about 3:50. Interesting remark - the guy doing the video states that AirStream Trailers (yeah - discount trailer company looking to shave dollars? NOT! ) - now installs LTs on their trailers. BUT - hey - what do they know.




Quote:
Originally Posted by Larry-NC View Post
Double- and triple-axle trailer tires are subject to huge sideways forces that trucks don't encounter.

Visualize what happens when the truck is turning left and the truck axis is 45 degrees to the trailer axis (moderately sharp turn). Because neither trailer axle turns, the front-axle tires are being dragged sideways to the left and the rear-axle tires are being dragged sideways to the right. In even tighter turns, the situation is worse. Now visualize the truck and trailer at 90 degrees. One hundred percent of the movement is sideways.

ST tires are designed for this sort of abuse. Are you certain that LT tires are?
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Old 10-31-2020, 10:36 AM   #16
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What pressure are the rims rated for?
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Old 10-31-2020, 11:02 AM   #17
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Quote:
Originally Posted by Rocknoids View Post
I tried searching the forum and found 79 pages of different tires issues.
I have a 2014 FR 8289WS. The Prev. Owner upgraded to ST 225/75R/15 D.
I have a quote from a tire shop to install E rated tires. Is that going to be too stiff? Should I stay with D rated or does it really matter?



You will only gain the LR-E tire load capacity if you inflate to LR-E levels i.e. 80 psi which may be too much for a light weight trailer that may only need ST225/75R15 LR-C load capacity.


Does the certification table show ST225/75R15 C ? or something different?


What were the scale readings when you weighed your fully loaded RV?


The answer to these two questions is important if we want to provide informed reply.
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Old 10-31-2020, 11:10 AM   #18
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If trailer came with a LR-C tire it was probably rated for the load the trailer was designed for with the mandatory safety margin.

Upgrading to a LR-D tire in the size mentioned will increase the capacity by 15 percent over the OE design (+the built in margin of safety).

Going to a LR-E tire adds 25% margin OVER AND ABOVE the OE tire which already had a safety margin built in.

Going two sizes up will do nothing for the load capability of the trailer itself and yield a stiffer, rougher riding tire with a higher cost. You still have the same frame and axles which both have their own load rating.
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Old 10-31-2020, 11:12 AM   #19
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I don't want to start another ST vs LT debate but some facts are important to consider.
- LT tires must be capable of passing more difficult DOT testing than ST tires.
- The Load formula for ST type tires is based on a 65 mph max operation speed.
- The SAE Speed test is designed for Passenger type tires and only requires the capability for a brand new tire to run the stated speed for 30 minutes
- Load capacity is a function of tire size and air pressure. larger size or higher pressure can result in more load capacity. BUT simply going to a higher Load range but not increasing inflation pressure is unlikely to deliver any increase in load capacity.
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Old 10-31-2020, 12:03 PM   #20
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Quote:
Originally Posted by TitanMike View Post
If trailer came with a LR-C tire it was probably rated for the load the trailer was designed for with the mandatory safety margin.

Upgrading to a LR-D tire in the size mentioned will increase the capacity by 15 percent over the OE design (+the built in margin of safety).

Going to a LR-E tire adds 25% margin OVER AND ABOVE the OE tire which already had a safety margin built in.

Going two sizes up will do nothing for the load capability of the trailer itself and yield a stiffer, rougher riding tire with a higher cost. You still have the same frame and axles which both have their own load rating.



My concern is that for DOT regulations, there is no "margin". They only require the total load capacity of the two tires on an axle be able to support the GAWR. This ignores the well known side to side weight imbalance so it is possible or even likely that one tire on an axle is overloaded while meeting NHTSA requirements, which means there is negative "Safety Margin".


In 2017 RVIA changed their guidelines to require a 10% margin but that is not a legal requirement only applies to association members.
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