Switching from 15 to 16 inch tires

[dpgllg]

I am considering switching my 15 inch ST225/75R15 LRE to a 16 inch LRE tire. I want to determine if this is feasible and affordable.

I Currently have the above mentioned tires on my 5th wheel. There are few choices in a Load Range E tire in 15 inch. This is what I know I currently have:
ST225/75R15 LRE
6 Lug wheels
Between 8 and 9 inches between tires
5200 pound axle rating

I know I need new rims tires but what other modifications are required? Do I need to replace axels brakes? Do they make a 6 lug rim to fit my current axle?

Thanks in advance

Dave

[JIMNLIN]

I just think that a LT tire such as a Michelin Defender.

I guess I am being proactive in that I want the best tire on the 5th wheel to eliminate any potential problems.

Dave

The Defender shows to be a all terrain type tread which isn't the best tread design for a tire on a trailer.
A good trailer tire needs at least a couple of solid ribs to keep the tire tracking straight with the tow vehicle. Much less sway issues.
If your wanting the best then its tires like the XPS Ribs or the Bridgestone R250 are a commercial grade all steel ply carcass with solid ribs for straight line tracking. Both are the holy grail so to speak for trailers with 5k/5.2k/6k axl

[htwheelz67]

I'm upgrading my triple axle ww to 16 as well, mine was rated for d rated tires though. the perfect fit from 15's are lt225/75/16 E tires, they are only barely an inch taller, the capacity is slightly less by about 150 lbs per tire BUT it is a much better tire than an st tire, in my case even though I have E tires my trailer came with D tires so I will be slightly more than D rating. The LT's will still be able to handle 10,720 lbs, if you get michelin xps tires or bridgstone durvais you will have absolutely no problems. On the cheap the falken wildpeak HT or sumitomo encounter ht are very heavy duty and long wearing. LT and vehicle tires tend to be slightly under rated to give them a bit of margin of saftey when overloaded, where as st tires don't have to conform to those standards.

[BurbMan]

OP, I agree it's a good upgrade, much better selection of tires and easier to find also. I'm not trying to talk you out of it, just pointing out that you should measure first to see what you;re in for.

[BFL13]

time2roll wrote:
I recommend tires the cover the full trailer GVWR.

They do. 4 x 2,830 = 11,320 which is more than the GVWR of 10,995.

The two axles are actually less than the tires at 10,400, but the axle weight at GVWR is 8,950 so that's ok. Lots of margin there.

It is a 5er. The pin carries a bunch of the weight--in this case 18.6% of it.

If you ever loaded the 5er to its axle rating of 10,400 your trailer would weigh 12,776, well above its GVWR. It would be worse if the tires got maxed. Now you are over the axle rating of 10,400 plus the trailer weight is even more above its GVWR.

IMO that trailer is designed just right. The numbers all work and have margin left over. Also those Reflections are kind of nice. 🙂

[Huntindog]

dpgllg wrote:
OP Here,

Thanks to everyone who responded!

The reason I am considering this upgrade is the selection of 15 inch Load Range E tires is limited. Only ST tires The 5th wheel has Westlake tires on it now and I have never heard of them before the purchase.

I just think that a LT tire such as a Michelin Defender.

I guess I am being proactive in that I want the best tire on the 5th wheel to eliminate any potential problems.

Dave

The best? Michelin XPS RIBS.
They are not cheap. They are the only tire I will use on my TT.

[time2roll]

I recommend tires the cover the full trailer GVWR.

[dpgllg]

OP Here,

Thanks to everyone who responded!

The reason I am considering this upgrade is the selection of 15 inch Load Range E tires is limited. Only ST tires The 5th wheel has Westlake tires on it now and I have never heard of them before the purchase.

I just think that a LT tire such as a Michelin Defender.

I guess I am being proactive in that I want the best tire on the 5th wheel to eliminate any potential problems.

Dave

[BurbMan]

I went from 15" ST LRD tires to 16" LT LRE tires. Everything looked OK when I put them but I wound up having clearance issues. You need a minimum of 2.5" above the tire as clearance for suspension movement. I thought I was OK until I took the first trip and saw the black rubber dust up under the wheel wells...I only had about an inch of clearance and while it looked OK while parked, every time I hit a bump the tire rubbed.

I wound up installing the Correct Track II alignment kit which also adds 2" of height to the trailer. That fixed the clearance issue.

Of course the factory ran the 1/2" black pipe for the propane tight to the inside of the frame, so installing the kit meant relocating about 20' of pipe (all the gas appliances are ib the rear of the TT so it's a loooong run from the tanks up front).

Then I needed to re-adjust the hitch again so the TT would tow level, which meant ordering a new stinger bar from Hensley.\

All in all, very happy with the upgrade and no more blowouts. Point here is that if you go this route, be prepared for additional work and expense you may not have planned on.

[wa8yxm]

I have done something like that with both of the light trailers (TT and PUP) I had.. Make sure you have the needed clearance around the tires. if you have dual tires or dual axles tire to tire as well.. If you do, GO FOR IT

The larger tire will be less likely to blow, will run cooler and place less strain and wear on the bearings. You may need to adjust your brake controller is all.

[BFL13]

Some folks just like to have more capacity even when they don't need it. No reason to talk them out of it---it is a personal comfort thing and that's that.

However, just to clarify the OP's weight situation as is, here are the numbers:

5er's dry weights--UVW - 8,253 and Dry Hitch - 1,535, so percentage of pin wt is 18.6%

GVWR - 10,995 so at that, 18.6 % pin wt is 2,045 and axle wt 8,950

We know these can vary a little by how you load the trailer and how much is in which tanks, but it will be near there.

So now we have two 5,200 rated axles for 10,400 to carry 8,950, which is plenty (so that is why the trailer has them)

And four tires to carry that will need 2,238 each in capacity--assuming each has an equal share (they don't as PT mentioned, so you want some margin)

The ST225/75R15 LRE has a capacity of 2,830 which has that margin over the 2,238. (which is why they are on there)

The OP wants more margin. But that does not mean the trailer is designed all wrong. It is just that the OP wants more margin.

http://www.sturdybuiltonline.com/ST22575R15-Trailer-Tire-Radial-by-LoadStar-LRE-2830lb-Capacity_p_87...

[JIMNLIN]

op wrote:
I am considering switching my 15 inch ST225/75R15 LRE to a 16 inch LRE tire. I want to determine if this is feasible and affordable.

Upgrading from a ST225/75-15 D with 5200 lb axles 6 lug hubs to a 16" LT E is the best upgrade for a trailer for 40k-60k miles and 7-8 years of trouble free service.
I've done this upgrade on every rv and non rv trailer with 4xxx lb/5200 lb axles I've owned.
I'm not a big fan of expensive wheels on a trailer. I use modular white or silver steel wheels from mostly my equipment trailer mfg down the road from me. I've bought many trailer wheels from southwestwheels.com in years past. Prices run around 50 bucks for a 16" x 6 lug 3045 lb rated wheel.

[pianotuna]

Hi,

There is a firm in Texas where I purchased new rims. I ended up with taller but narrower tires that had a lot more carrying capacity. I may end up having to add another leaf to the springs in the rear as the metal ages.

My old tires (Michelin) were actually overloaded on the driver's rear. For some unknown reason the makers put the battery bank, fresh water tanks, and waste tanks all on the driver's side. How typical of RV makers.

One of the issues is finding a rim that has a sufficient air pressure rating. I'm right on the maximum for the rear dual rims.

[rhagfo]

BFL13 wrote:
Wheel well clearance above the tire stopped us from going to 16 from 15. Also width issue on one side where a fatter tire would have rubbed on the metal LP gas pipe going past between tire and frame.

If you can't fit the 16s and it is to gain height for being nose high when hitched, be sure you look at raising the pin box (ours had three height options) and lowering the hitch---juggling all the while how much clearance you still have above the truck box rails.

If none of that gets it done, then you are left with putting spacers between frame and springs to gain height back there.

Interesting both of those issues can be overcome. Gas line can be moved further inboard, I needed to do this to Install shocks on our 5er. Overhead clearance could be as easy spacers or axle flip.

[time2roll]

dpgllg wrote:
Do they make a 6 lug rim to fit my current axle?

http://recstuff.com/trailer-wheels/16-inch/

Brakes should be fine. If you want to upgrade consider 6,000# axles, disk brakes and 8 lugs. Going to be a few extra $$.