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Rear Radius Rods


New Member
I've seen many different types of radius rods used in t bucket solid rear suspension set-ups... cut front end radius rods mounted on the rear axles, ladder bar type, original rear radius rods, etc. I have a really good set, not rusted, of 1936 Ford radius rods that I'm using for my track-t. They are strong because I've tried to bend them to see how much flex there is and I can't see any flex. Of course they have been shortened a bit. My question is how strong, how much power should they be able to handle by themselves. I've seen the other radius rods mounted usually in front of the rearend on a vertical mount. The 36 Ford radius rods mounts underneath, horizontally, sort of around the axle tube. Has anyone used these and had problems with this type of setup? I do plan to add another thick walled tube which will mount on top of the rearend, beside the yoke and run the same length as the radius rods, mounting at the same distance. This should relieve some of the twisting stress.
I've used these on 2 cars with no problems. One thing I would suggest is to remove the factiry welds and reweld them. If you look at them you will probably see little holes in the welds which makes them prone to cracking. These were also used on '35 Fords.Unless you are planning on gobs of horse power, you probably won't need the extra bar. That's not to say it would't hurt though.

You don't by any chance know of another set of these for sale do you?

The ideal length for hair pins is the same length as the distance from the front u-joint to the axel housing. On short wheelbase cars this is sometimes hard to follow.

Youngster. I'll check those factory welds and re-weld. As for installing the third radius rod, I saw a kit online using a third rod on the older ford banjo rearend which had been modified to use a modern drive shaft and not the old torque tube. They said with the torque tube removed, it weakened the rear assemble. Don't know if that's true or not but I do know that it can't hurt.

In the power department, I'll be running a Buick 430. Mostly stock... about 375 to 400hp but close to 500Ft-lbs of torque. So I want strength. But I also like the look of the old radius rods. I could have built something like a NASCAR setup, truck arms, but I think they look too boxy. I though about going with the SO-CAL radius rods but I bought the ones I have now for a quarter of the price SO-CAL wants.

I saw a pair of old ford radius rods on Ebay a day or so ago. They might still be there. I think they were from a 35-36 ford.
I'm going to go a different direction on this one. These were never meant to act as radius rods, but just to work in conjunction with the torque tube of the stock rear end. There have been several posts on places like the HAMB where these were used this way and then broke. One report was within the last couple of months.

Here is one sad tale:

I don't want to step on any toes here, but I also don't want to see anyone killed and me not say anything. :ciao: I have split bones on the rear of my '23, but they are special ones that PSI sold at one time to mount an open driveline in an old Ford that originally had the banjo rear. They are twice as heavy as the stock Ford bones. Please do not use the stock ones in this application.

donsrods. I went to the link you provided. Definitely an eye opener. After reading what they said I think I will be looking at making a change or two. I thought the possibility of the two bolts mounting the radius rad to the rearend might be a problem, thats why I considered mounting a third rod on top to reduce the torque acting on the rear housing. I found pictures of a modification using a split front radius rod with a bushing welded in the back. This could then be used either as the bottom of a hidden four link or as part of a three link set-up. With the four link, I would think that there might be a problem with the differences in the lengths of the rods themselves. You wouldn't want a four foot rod on the bottom and a two foot rod on top, I would think. The three bar though would work good and be easier to convert. Thanks.

This is why forums are so great. It's better to learn something now then to have it bite you later.
I honestly did hesitate before posting because I didn't want to throw a wet towel on your plans, but I have heard numerous reports, both on the internet and in magazine articles, about how these will snap with no warning. They were only designed to position the Ford rear and not be the sole locator. No amount of reinforcing seems to be an absolute guarantee that it will last. I have cut these in half, and the tubing is surprisingly thin.

PSI went out of business probably in the 80's, but if you can locate one of their kits these were designed specifically for this purpose and are extremely thick and strong. I lucked out and found a set on Ebay a while back and stayed up until 2 am to win them because I needed them for my T. :ciao: They do come available once in a while, so you might keep your eyes open.

As for the bars being different length, yes, you are right. They need to pivot in the same spot to avoid binding. Shoot us a picture of what you are working with and maybe we might be able to offer another suggestion. In the meantime, here is a picture of the PSI bars I was talking about.

Thanks. Right now I'm looking at two options. First is to get some 1" od 3/16" thick tubing and tap the ends to 3/4" fine thread. The ford radius rods a 1/8" thick and have a 1" id from side to side. I can cut the ford rods, drill a few holes in the side of the rods, slide the 1" tubing through the old ford rods and then weld the tubing to the rods through the holes and around the ends. A lot of work but it would keep that old school look. Or I could get some 1 3/8" od tubing, weld a 1" bung on either end. That would be faster, strong but not as pretty. Either way I still plan to go with the 3 link set up. Found several helpful web sights and printed off the information.
I'm going to do a 180 here. I took it for granted that you were talking about a closed driveline. My mistake. If you are going to run an open drive shaft, you defently want to go to another type of rear end control system. Sorry, I didn't mean to mislead anyone.

If you are interested in selling those '36 bones, let me know.


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