Wanting to change from STs to LTs..........

We are the proud new owners of a 2007 K-Z Sportsman 5th wheel. The unit is in EXCELLENT shape for its age. This is our first (but likely won't be our last).

I have read numerous posts on the arguments of STs versus LTs. My conclusion is the I am going to replace the current tires/wheels with larger, more robust ones.

Here is what I currently have:
Tire: Load Max Radial
Tire Size: ST225/75R15
Overall diameter: 28.3"
Rim width range: 6-7"
Date Code: 614 0906 (waaaaay old!)
Wheels: Six bolt on 5.5" centers
Load rating for each tire: 2540 pounds
GVWR for trailer: 10,000 pounds

Here is what I want:
Tire: Michelin LTX A/T 2
Tire Size: LT245/75R16
Rim width range: 6.5-8"
Overall diameter: 30.5"

Wheel Choice #1: HiSpec Series 04
Wheel Size: 16x7
Wheel load rating: 3200
Offset: +5mm

Wheel Choice #2: HiSpec Series 05
Wheel Size: 16x6.5
Wheel load rating: 3580 pounds
Offset: 0mm

So, what have I considered so far?

1. Separation between current tires is 5.0". By using this size tire the separation would be 2.8". This would appear to be sufficient.

2. Currently there is 6" of suspension travel between the top of the tire and the floor of the 5th wheel. This would be reduced to 4.9". This, too, seems sufficient.

3. The passenger side shocks currently sit 3/4" away from the tire. This might be dicey with a bigger tire and wheel. If the tire is too close the options are to (a) put a spacer between the wheel and the hub with longer lug nuts or (b) move the shock to the other side of the axle (likely NOT a good option.)

4. The passenger side front tire is close to the fender. I could (a) trim off part of the fender or (b) install a brace underneath to push the fender our a few tenths of an inch or (c) a combination of (a) and (b).

5. The top of the tire to the bottom of the fender is 3.5". I don't know just how much more the bigger tires would protrude. Of course, the current tires don't have a problem with hitting the inside edge of the fender. I'm not sure if the bigger tires would have an issue or not.

So, what have I missed?

Thanks for your help!!

Paul.

laknox
Nomad
Jul 17, 2014
Sounds like you've done a lot of research already, so my only comment is that, since you seem to have clearance issues with the shocks, why not consider a narrower tire?

Lyle
Me_Again
Explorer III
Jul 17, 2014
Or just remove the shocks and give it a try. They only have minimal value anyway.
ol_Bombero-JC
Explorer
Jul 17, 2014
Me Again wrote:
Or just remove the shocks and give it a try. They only have minimal value anyway.

Yikes! - "minimal value anyway"

If you ever had a trlr *without* shocks - then added them, you would/should know the "shocking" night & day difference!.:R

"Minimal value shocks" (car/truck or trailer): they are most likely OEM and (way) overdue for replacement.

BTW - If you don't need shocks - take the shocks off your car or truck!..:S..:S

~

OP: You did excellent homework.
Suggest:
1. Michelin XPS Ribs in the size you stated.
2. *If* you feel you don't have adequate clearance between tires & shocks (appears to be a bit more than 1/4 inch which is "tight") - move the shocks further inboard, which is no big deal.

Sometimes the fender supports are easily bent to provide clearance.

Wheels - supplier not important. Wheels = Alcoa.

Buy and try *one* - with the caveat....for "test purposes" (no on-the-road time) - if it doesn't provide the clearance you want, the tire & wheel are "returnable".

~
gitane59
Explorer III
Jul 17, 2014
You have done very logical research and would only make one major change.
While going with wheel choice number 2 for a slightly narrower profile and less stress on the axle with zero offset I like Ol-Bombero would match them with Michelin XPS Ribs not LTX AT's.
Here's why.

Compare the 2 tread patterns side by side and you will notice a distinct difference.
The LTX AT will have very a blocky chunky tread pattern with no obvious continuous ribs of rubber running the circumference of the tire. also it should be noted that the tires shoulders are made up of blocks of separate rubbers blocks again for traction when turning corners in poor conditions.
This is for traction in poor conditions such as rain, mud, sand, hence the AT (All Terrain)

Now the XPS Rib will have Ribs running the entire circumference of the tire for direction stability and smooth rolling. The shoulders also will have solid ribs with small lateral sipes or grooves for water extraction running the circumference of the tire . The treads shoulders on the Ribs are designed to minimize side traction when turning tight corners minimizing lateral suspension stress.
Lastly the tires which will be subject to a high continuous load factor being used on a trailer therefore the highway RIB tread pattern will run cooler than the chunky aggressive LTX All Terrain tire due to less flexing and moving if the tires treads pattern as it turns and rolls in use.
Cooler tires always equates to longer life.
JIMNLIN
Explorer III
Jul 17, 2014
Compare the 2 tread patterns side by side and you will notice a distinct difference.
The LTX AT will have very a blocky chunky tread pattern with no obvious continuous ribs of rubber running the circumference of the tire.

Excellent point for a highway trailer. Now if the OP goes off roading then that type tread will help tracking in mud/etc.
Tires for trailers need at least one solid rib in the center of the tread or both edges for best tracking/handling.

We have a much better tire tread choice with the two all steel ply commercial grade Bridgestone R250 or the XPS Ribs.

Goodyear Wrangler HT
Firestone Transforce HT
Cooper Discoverer HT3
fresh dated BFG Commercial HT
fresh dated Uniroyal Laredo HD-H
Paulb1310
Explorer
Jul 17, 2014
Thanks everyone for the input!!

Laknox:

Interesting comment. I did some research and discovered that the next size down in either the Michelin LTX A/T 2 or Michelin XPS Rib is an LT225/75R16. However, there is no LT235/75R16. There is a LT235/85R16 but this tire is too tall.

Gitane59:

The XPS Ribs look like a really great tire. And the reviews on Tirerack are stellar. They do appear to require a narrower wheel which would certainly help in the clearance issues. I was just trying to avoid that $300.00 cost per tire. But then, I guess some sacrifices have to be made, huh? lol

Another question:

It appears that if I were to put on the XPS Ribs that there is a range of tire pressures that I could actually run. Is it recommended to run a lower tire pressure since I will be loading the tire less than 80% of its capacity? Or does less tire pressure totally defeat the purpose of going with a larger tire?
Paulb1310
Explorer
Jul 17, 2014
Jimnlin:

Thanks for the input. I will research each of those tires. Do you have first hand experience with any of these tires?

Does anybody else have first hand experience with any of these tires in this list?
tvman44
Explorer
Jul 17, 2014
BF Goodrich Commercial TA in 225x75 R16 is what I went to from 225x75 15 1" taller same width.
padredw
Nomad
Jul 17, 2014
I put on four Firestone Transforce HT based on recommendation of a tire dealer who is very active on another RV forum.
Me_Again
Explorer III
Jul 17, 2014
Paulb1310 wrote:
Jimnlin:

Thanks for the input. I will research each of those tires. Do you have first hand experience with any of these tires?

Does anybody else have first hand experience with any of these tires in this list?

I ran XPS RIBs for 6.5 years and 40k+ miles and now R250's for two years. The R250's are about 50 bucks less per tire and just as good. Trailer is 12,200-12,400 and I run 71 pounds inflation.

I said remove the stocks and test because Cardinals had stocks for years and quit putting them on in 2011. Our club members are not running out and installing them.

I would install LT235/85R16E R250's on 6 or 6.5 zero offset wheels and deal with stocks as necessary. On trailers it is very important to have zero offset wheels centered on hub bearings. Just ask Titanium owners that got OEM axles and wheels that were not setup that way.

Chris

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Wanting to change from STs to LTs..........

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