What exactly is the proper adjustment for the rear running board truss rod? The one on my '14 is quite bowed in the middle and the threaded nuts are at the very end of the rods. Should these rods be relatively straight?
One is bowed,as you say,to provide "bounce clearance"for the radius rods.
Jack, I don't think Bill was referring to the fact that the rear truss rod has permanent bends near each end for clearance but rather was wondering about the total temporary bend or sag if you will, which occurs as you tighten the nuts. I have some experience with this. Mine broke, I welded it and one year later, it broke again. I made a new one from scratch. I believe you need to tighten the nuts until the rod just starts to bend. Too much bend and there will be less support for the running board. It seems you can never adjust it for maximum support and you can't. This is clearly the reason that Ford introduced the large and sturdier stamped bracket in 1920. I hope that helps.
You're absolutely right - my back truss rod is sagging in the middle pretty bad. It sound like I should loosen the nuts and adjust the rod so it's only slightly bent.
Yup, I even have to loosen mine a bit because I installed it with the more is better approach. BTW, the new steel won't make it any stiffer.
I have used a floor jack and block of wood to push most of the sag out. Suggest pushing on it some before you loosen up any nuts. Removing the sag should provide better running board support.
In my opinion, the running board brackets and truss rods should be adjusted in such a manner that the running boards themselves are in a satisfactory position that is flat and parallel to the ground.
I've seen Model Ts with running boards with the outside edge cocked-up, cocked-down or the entire running board slightly twisted. You can eliminate this by fine tuning the brackets and truss rods.
Personally, I like to have the truss rods under slight tension.
I would suggest that over the years and miles the running board brackets themselves get bent out of shape and you really should get out your tape measure and restore the running board brackets to proper shape and dimensions based upon the frame dimensions. I have made a CAD drawing of frame made not from measurements I made of any frame but made from the actual Ford blue print for the frame. Remove the truss rods and get the running board brackets into the correct locations and then install the rods to provide support at those correct locations.
Here is a link to the free drawing which I have made. While this is a drawing of an early frame the later frame without the rear cast iron body brackets has all of the body brackets at the same locations as the later frame so the dimensions you need are the same for any frame that has running board truss rods.
I meant to also post some research on the running board truss rods that we make. You can make your own of course if you need to but the back to back z bends are tough to get in the same plane. Our stock of the correct single chamfer nuts is very limited but you might be able to make your own. Follow the link on our product page and download the history of the truss rod part itself if you want more info.
Thanks everyone, for the great advice! John, the drawing is very helpful - but I have a question. If the running board brackets themselves are bent upwards when the truss is off, can I just bend them cold to the correct height or do I need to use some sort of tool for this?
I have an accessory running board brace on three of my T's. These stiffen the body a lot, reducing the amount of bending when stepping on a running board for example.
It appears that my running board brackets on the drivers side are about 1.5" too high (bent upwards), according to the diagram that John posted. Can I bend these brackets cold? If so, is there a certain method used to bend them easily?
They can be bent cold and it is a rare model T that does not have them crooked due to stumps and other objects getting snagged on the truss rods. They seem generally to be bent in all directions but most everyone bends them without removing them from the frame. I confess I farmed that job out to my body guy since I didn't own any equipment at the time. The bracket ear with the hole in it is supposed to end up vertical and when the frame is straight and the brackets bent correctly to the frame dimensions given, the rod will sit horizontal without stress although you have to flex the brackets a bit wider to get the rods in place but they flex back to correct position if that is where they were.