Rim and Tire Question

cpaulsen wrote:
I went from ST235/80/R16 on my 6" wide rims to LT245/75/R16 and have never had a problem.

I recently did this as well, based on speaking to others and the Bridgestone tech line. The tire engineer I was transferred to said "don't worry about it". I mind-effed this decision for way more time that I care to admit...

I've run slightly over-width tires - often at very low inflation pressures - on my truck for years, and have never had an issue, so I don't feel concerned at all.

The tire spacing on my Cyclone 3950 with 235/85-16 was too close for comfort, could not even fit an x-chock between the wheels. It's a common issue, based on what I've read on various forums.

The 245/75-16 Duravis R250's are a smidge smaller, giving me more space between my tires for both piece of mind, and the use of x-chocks.

I will help you with a little math. The BFG Commercial TA LT235/85R16 is 31.4 inches and diameter and the Bridgestone Duravis R250 is 31.8. Subtract those numbers from your 32.25 space and in both cases you have less than 1".

Now for the LT245/75R16s. TA is 30.4 and R250 is 30.7. So the TA gives you 1.85" and the R250 gives you 1.58" between the tires. Get the R250's!

Chris

I just got back from the dealer and verified the measurements at home. It looks like I have 32 1/4" between the axle centers. All of the other measurements looked good. I have about 3.5" from the top of the tire to the bottom of the wheel well. I have 3" from the inside of the tire to the frame. The outer tire to the trim above the wheel is close, but it might require some manageable trimming.

Me Again quoted a 33" spacing between centers for the LT235/85R16. Therefore it looks like I will need to go with the LT245/75R16. Please correct me if I am wrong.

Now I just need to find out if the tire shop is OK with putting the tire on a 6" rim! It sounds like a lot of you are not having a problem with this (Thanks JIMNLIN!).

Thanks for all of your help!

Two hours and 3 minutes!

This is a quote from a well known tire retailer. I've highlighted the key words.

Personally I think going outside of approved parameters should be decisions for the experts to sign off on as the quote below supports.

"Some vehicle manufacturers have developed Original Equipment applications in which the rim widths are not within the tire's original approved rim width range. While outside the normal recommended rim width ranges, these applications meet the specifications of the vehicle manufacturer".

FastEagle

^^^ There you go someone with actual commercial and RV towing experience providing real world input. Get it done before a bird poops on your plan. Chris

Tires on trailers aren't as sensitive as the same tire on a tow vehicle to issues (not all) like proper tire/wheel width. Thats why LT245/75 has always worked fine and why folks that have used them don't have issue .... like they would on a truck.

Unlike the same tire on a truck, those tires on the trailer will operate 24/7 at close to their max weight rating which eliminates issues like riding the centers and other issues we would have with a same tire on the tow vehicle.

I've worn out several sets of LT245/75-16 E tires on 6" wide trailer wheels on my equipment trailers. I got the same 40k-60k miles out of them just as the LT235/85-16 E tires.

I prefer a narrow tire like the 85 series tire for trailer use. If it was my trailer the first choice would be the LT235/85 but if there wasn't room then I would go with the LT245/75 tire. They will work fine.

My trailer is at the dealership having the alignment checked. They called me yesterday and said that I can pick it up today.

It sounds like I need to see how much clearance I have between tires. Once I get it home I will take some measurements of the wheel to wheel distance and let everyone know.

Thanks for the help.

CapriRacer wrote:
OK, here's the deal:

The allowable rim width range for an ST235/80R16 is 6" to 7 1/2".

The allowable rim width range for an LT235/85R16 is 6" to 7 1/2", but the tire is 1" larger in diameter - so you will need 1/2" more clearance.

The allowable rim width range for an LT245/75R16 is 6 1/2" to 8". It is 0.3" smaller in diameter, but it is 0.3" wider - so you need a little more than 1/8" side clearance, if you are using the same wheels.

Please note that tires move up and down due to suspension movement, but they also deflect sideways under cornering. The clearance you see when the vehicle is not moving is not what happens when the vehicle is moving. It takes some experience to determine how much you need.

Also, if you use a rim that is outside the allowable range, you MAY experience some issues. Common complaints are center wear, sensitivity to cross winds, and following the ruts and grooves in the road.

Personally, I think replacing ST235/80R16's with LT235/85R16's makes a whole lot more sense than LT245/75R16's.

However sometimes the axle spacing is to close for the LT235/85R16's. Dexter calls for a minimum tire to tire clearance of 1". For most 235 installations axle center to center needs to be at least 33"! Just saying! Some trailers do not meet that requirement. Got to love it when OP does not return with additional info!!!!

Chris

OK, here's the deal:

The allowable rim width range for an ST235/80R16 is 6" to 7 1/2".

The allowable rim width range for an LT235/85R16 is 6" to 7 1/2", but the tire is 1" larger in diameter - so you will need 1/2" more clearance.

The allowable rim width range for an LT245/75R16 is 6 1/2" to 8". It is 0.3" smaller in diameter, but it is 0.3" wider - so you need a little more than 1/8" side clearance, if you are using the same wheels.

Please note that tires move up and down due to suspension movement, but they also deflect sideways under cornering. The clearance you see when the vehicle is not moving is not what happens when the vehicle is moving. It takes some experience to determine how much you need.

Also, if you use a rim that is outside the allowable range, you MAY experience some issues. Common complaints are center wear, sensitivity to cross winds, and following the ruts and grooves in the road.

Personally, I think replacing ST235/80R16's with LT235/85R16's makes a whole lot more sense than LT245/75R16's.