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Old 06-30-2011, 12:32 PM   #1 (permalink)
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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.
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Old 06-30-2011, 03:04 PM   #2 (permalink)
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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.
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Old 07-01-2011, 07:46 AM   #3 (permalink)
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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

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Old 07-01-2011, 07:55 AM   #4 (permalink)
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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.
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Old 07-01-2011, 08:00 AM   #5 (permalink)
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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.

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Last edited by YellowSub1962; 07-01-2011 at 08:02 AM.
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Old 07-01-2011, 01:13 PM   #6 (permalink)
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Quote:
Originally Posted by 370 View Post
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.
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Old 07-02-2011, 03:05 PM   #7 (permalink)
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Quote:
Originally Posted by Diesel_Dirk View Post
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

Last edited by 370; 07-02-2011 at 03:06 PM.
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