How to Determine Difference Between Hub Face and Spring Center on Trailer

Published 01/23/2015

Question:

My trailer frame is 4 inch channel with 1.5 inch flange and the out to out dimensions are 80 inches/frame width is 80 inches. I am trying to be thrifty and have to keep costs down. Aquired ford ranger aluminum wheels and tires for free. They have a 4 .5 in backspace and tire mounted on rim width overall is 9.75 inches. Axles are 3500 lbs. My question is what should the spring centre to hub face dimension be in order to keep my track legal and slightly under the max width width of 96 inches? Also the hubface out to out dimension? I am at my wits end trying different things. Also would , do you think 1 in approximate spacing between trailer frame and tirerim sidewall.Also I am using 9.75 by 72 inch tandem fenders and again another question, what clearence should I plan between tire top and inside top of fender? It will be packing aZ28 race car. I sure would appreciate your team answering my questions Thankyou . Good site.

asked by: Wayne M

Expert Reply:

We do not recommend using automobile tires/wheels on a trailer. Trailer tires are built special with a thicker sidewall that can accommodate higher air pressure and the weight of the trailer load compared to passenger vehicle tires. Trailer tires and auto wheels are not compatible. If you can provide the size of the current special trailer tires, and the diameter and width of your current wheels, I would be happy to recommend a tire/wheel combination for you.

With 3500 lbs straight axles the difference between the hub face and the spring center is between 11.25" (minimum) and 18.00" (maximum.)

According to my contact at Redneck Trailer Supplies you will need at least 2" between the inside wall of the trailer tire and the trailer frame. As for clearance between the tire top and inside top of fender you will want to allow 1.5" deflection at the rated capacity of spring for approximate full load dimension, and 3" above tires beyond that point for "maximum bump clearance." For best suspension performance allow 2-2.5" clearance above the top of the axle to the bottom of the frame.

I have included a link to a FAQ article on trailer tires for you to check out.

expert reply by: Chris O