How to calculate what size trailer I need - Pirate4x4.Com : 4x4 and Off-Road Forum

GRMhick · 06-30-2011, 12:32 PM

I've spent the last 3 days looking at more trailers than I care to think about. The things I have noticed are the inconsistencies from manufacturer to manufacturer on what frame sizes they use on car/equipment trailers. So far I have seen:

3x5 Angle (with 4" channel tongue)
4" Channel
5" Channel
6" Channel
2x4" Tubing

These are on 16' and 18' 7k & 10k car trailers.

How do I calculate the frame strength, and is there a rule of thumb as to calculating this? Are there industry standards for frame size vs. length vs. capacity?

My goal is to maximize the load capacity of the trailer, while keeping under a 10k loaded trailer weight.

yager · 06-30-2011, 03:04 PM

IMHO for most people 5" channel perfect for 10k trailer, 4" good for 7k. I would also find a mfg with the double stacked tongue. This is where the tongue is a 2nd layer under main frame and extends back roughly to the first spring hanger.

Many manufactures have a standard frame and simple toss different axles under it. It's ok if its where you need to be, if not you end up with a heavy ass trailer for no reason.

370 · 07-01-2011, 07:46 AM

stick with channel.. angle frames twist and need the side rail to stiffen them up. and i've made the mistake of buying a box tube frame car trailer. the frames rot horribly! all the screw holes for the decking leak water into the box tube and the water sits and rusts the frame rails and crossmembers out

MT4Runner · 07-01-2011, 07:55 AM

Unless you go stupid thin, depth of your frame members is stronger for weight than additional thickness.

C5x6.7 has a ~3/16" thick web.
C5x9 has a ~5/16" thick web and not a lot more stiffness.

YellowSub1962 · 07-01-2011, 08:00 AM

I think any 7-10K trailer will work for what you're talking about. I have a 7K Carson car hauler that I put 10K (dual 5200's) running gear on, and a new coupler and have had it at 9K a bunch of times, and over 10K for 3 trips from CA to CO. On the smaller trailers as long as you have the "stacked frame" as mentioned above, you should be fine. mine is channel also.

Only way I'd go boxed frame is if it was aluminum.

Diesel_Dirk · 07-01-2011, 01:13 PM

Quote:

Originally Posted by 370

stick with channel.. angle frames twist and need the side rail to stiffen them up. and i've made the mistake of buying a box tube frame car trailer. the frames rot horribly! all the screw holes for the decking leak water into the box tube and the water sits and rusts the frame rails and crossmembers out

X2
Replaced the frame on mine once already.

370 · 07-02-2011, 03:05 PM

Quote:

Originally Posted by Diesel_Dirk

X2
Replaced the frame on mine once already.

mines getting replaced with a 4" c channel frame eventually... since it;s only 2 3500lbs axles.. only 1 of which has brakes

06-30-2011, 12:32 PM	#1 (permalink)
GRMhick Pirate4x4 Addict! Join Date: Feb 2000 Member # 87 Location: I live in hotels tear out the walls I have accountants pay for it all Posts: 7,203	How to calculate what size trailer I need I've spent the last 3 days looking at more trailers than I care to think about. The things I have noticed are the inconsistencies from manufacturer to manufacturer on what frame sizes they use on car/equipment trailers. So far I have seen: 3x5 Angle (with 4" channel tongue) 4" Channel 5" Channel 6" Channel 2x4" Tubing These are on 16' and 18' 7k & 10k car trailers. How do I calculate the frame strength, and is there a rule of thumb as to calculating this? Are there industry standards for frame size vs. length vs. capacity? My goal is to maximize the load capacity of the trailer, while keeping under a 10k loaded trailer weight. Last edited by GRMhick; 06-30-2011 at 12:34 PM.

06-30-2011, 03:04 PM	#2 (permalink)
yager Evil Twin Join Date: Mar 2002 Member # 10695 Location: Raleigh, NC Posts: 2,876	IMHO for most people 5" channel perfect for 10k trailer, 4" good for 7k. I would also find a mfg with the double stacked tongue. This is where the tongue is a 2nd layer under main frame and extends back roughly to the first spring hanger. Many manufactures have a standard frame and simple toss different axles under it. It's ok if its where you need to be, if not you end up with a heavy ass trailer for no reason. __________________ Mike Yager - Jeep TJ Build Up - Ecotec, Toy axles etc.. Ecotec - Technical Info E450 Ambulance VRAY (YAger RV) VRAY 2006 E450 - Ambulance Cummins Diesel Swap

07-01-2011, 07:46 AM	#3 (permalink)
370 Registered User Join Date: Feb 2010 Member # 153116 Posts: 1,055	stick with channel.. angle frames twist and need the side rail to stiffen them up. and i've made the mistake of buying a box tube frame car trailer. the frames rot horribly! all the screw holes for the decking leak water into the box tube and the water sits and rusts the frame rails and crossmembers out Last edited by 370; 07-01-2011 at 07:47 AM.

07-01-2011, 07:55 AM	#4 (permalink)
MT4Runner IDIot! Join Date: Mar 2005 Member # 44480 Location: Kalispell, MT Posts: 16,616	Unless you go stupid thin, depth of your frame members is stronger for weight than additional thickness. C5x6.7 has a ~3/16" thick web. C5x9 has a ~5/16" thick web and not a lot more stiffness. __________________ Motive Gear Land Use Team http://www.tenfactory.com http://www.motivegear.com http://www.nationaldrivetrain.com http://www.davezoffroadperformance.com http://www.mastercraftsafety.com FToy 086 - UHaul Toterhome

07-01-2011, 08:00 AM	#5 (permalink)
YellowSub1962 108" Smurfmobile Join Date: Aug 2000 Member # 1494 Location: The Land Of The Free, Thanks To The Brave! Posts: 8,265	I think any 7-10K trailer will work for what you're talking about. I have a 7K Carson car hauler that I put 10K (dual 5200's) running gear on, and a new coupler and have had it at 9K a bunch of times, and over 10K for 3 trips from CA to CO. On the smaller trailers as long as you have the "stacked frame" as mentioned above, you should be fine. mine is channel also. Only way I'd go boxed frame is if it was aluminum. __________________ Peter S. Di Primo PSD Enterprises, LLC - Waterjet, laser, metal forming, CNC work, Fiberglass and Carbon work, patterns and molds. No job too small. Prototyping and small production is our specialty, but we have the network to handle large jobs as well. Email me if you need something cut, bent, formed, milled, machined, etc. Founding Member - VCAS4WDC www.axlesnappers.org Help Fight Global Warming- turn your A/C on high and open all your windows. Alcohol, Tobacco, and Firearms should be a convenience store - NOT a government agency!!!! Last edited by YellowSub1962; 07-01-2011 at 08:02 AM.

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