Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 01-25-2012, 05:59 AM   #21 (permalink)
Tire Geek
CapriRacer's Avatar
Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 758
Thanks: 2
Thanked 351 Times in 215 Posts
Originally Posted by skyking View Post
Thanks for that. I have a question to pose:
I am building a 5th wheel trailer with (2) 2000 pound rated axles, and the common tire size in that situation is ST175/80R-13, with a 24.1" dia. 23.2" loaded height, 1360 LB capacity. I have planned around the ~23.2" loaded height. Other design factors require that I keep the diameter around this value.
I can't find any resistance data on these tires.......
And you won't. Aside from the fact that finding RR on regular passenger car tires is difficult and complicated, ST tires (like LT tires) are largely exempt from the regulations that apply to passenger car tires - so they are proportionally ignored by the folks that are interested in such things.

Originally Posted by skyking View Post
.........The super low crr bridgestone b381's are available in a 185/70R14 with a similar diameter and a 1200 pound capacity.
The trailer's planned load values are closer to 900 pounds per tire, about a 10% cushion below axle rating.
So this tire is slightly wider, but has a lower aspect ratio. Any thoughts? Are trailer tires low crr to begin with?
One quirk that you are not aware of is that Passenger car tires have to be derated 10% if used on a truck or a trailer. So the load carrying capacity would be 1200/1.1 = 1090 (or about a 21% reserve capacity)

But be careful. These things have a way of growing out of hand. I wouldn't be surprised if that 900# load turns into a 1,00# load pretty quickly.

  Reply With Quote
The Following User Says Thank You to CapriRacer For This Useful Post:
skyking (01-25-2012)
Alt Today
Popular topics

Other popular topics in this forum...

Old 01-25-2012, 11:47 AM   #22 (permalink)
Master EcoModder
skyking's Avatar
Join Date: Apr 2011
Location: Tacoma WA
Posts: 1,365

Woody - '96 Dodge Ram 2500 SLT
Team Cummins
90 day: 23.82 mpg (US)

Avion and Woody - '96 Dodge/Avion Ram 2500/5th wheel combo
90 day: 15.1 mpg (US)

TD eye eye eye - '03 Volkswagen Beetle GLS
90 day: 49.05 mpg (US)

Mule - '07 Dodge Ram 3500 ST
Thanks: 708
Thanked 500 Times in 326 Posts
Thanks. I'll not derail the thread further, but I am weighing the trailer as I build it. The torsion half axle sizes jump from 2000 to 3500. torsion axles perform best when loaded near design capacity; a lightly loaded torsion axle is a rough riding one.


2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle

currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears
  Reply With Quote
Reply  Post New Thread

rim, wheel, width

Thread Tools

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com