CapriRacer wrote:
mtnmonkeys wrote:
I've been following this thread as time has allowed and have a question for CapriRacer. My question is, "Have I made an unsafe choice in tires?"
I replaced a set of Karrier LoadStar ST235/80-16 tires rated at 3500 lbs. @ 90 PSI with a set of Bridgestone R250 LT245/75R16 tires rated at 3042 lbs. @ 80 PSI. (For what it's worth, the wheels on the trailer are aluminum and rated at 3100 lbs. @ 80 PSI.) These tires are on a Cardinal 34TS 5er with a GVWR of 14.4K lbs. with 12k allotted to the axles. We consistenly load the trailer to approx. 12.5k-13k lbs. with ~9850 lbs. on the axles.
Now, if I understand correctly, to help reduce the chance of failure in the ST tire, it should be loaded to no more than 85% of its rated capacity? If that's the case, 85% of 3500 lbs. would be 2975 lbs., so the Bridgestone tires rated at 3042 lbs. should be okay? Or am I missing something?
I guess that's a few more than one question. Thanks for any insight you can provide.
First, go to my web page on ST Tires:
Barry's Tire Tech - ST Tires
Early on, I recommend weighing the trailer and getting the individual tire loadings. You've quoted axle weights - but it is unclear if you've actually weighed each axle individually. I'm assuming you did not.
If you follow the procedure I outlined, then you would need to add 15% to the average tire load (9850# divided by 4 times 1.15 = 2832#).
You need to select a tire with a load carrying capacity such that it doesn't exceed 85% of the rated load (2832# /.85 = 3331#)
- and here is where it gets sticky. Because of the different ways the load capacity can be calculated, LT tires when used in trailer service have more capacity than what is listed on the sidewall. In my opinion, you actually increased the load carrying capability - and if you'll look at the spreadsheet I wrote up, you followed my recommendation (with the provision that you are using a different size that has the same load carrying characteristics)
As I said in the spreadsheet, the controversy here is that the rated load carrying capacity of the LT tire is lower than the tire being taken off and that ought to make any tire dealer nervous and likely to refuse to make the exchange.
And one last thought: I note that the Karrier LoadStar ST235/80R16 Load Range E has a different load vs inflation pressure rating than what is published by the Tire and Rim Association. I wonder what is going on there.
Kenda has chosen to go their own way concerning ST235/80R16 and ST235/85R16 tires. They use differing pressures and capacity ratings than most in the ST industry that is targeting the 7K/7.2K axle and above market including dual tire usage ratings. This gets a "low cost" option for the larger axle market in CE and industrial markets.
Look at the Kenda Karrier and Karrier HD here:
Kenda Trailer tires
