OE-style Aftermarket Radius Arm Quality?

a2thy · Aug 9, 2017

I need to replace the driver side radius arm on my 2wd '97 Mazda B2300 but didn't want to shell out the much steeper price for an OEM replacement unless absolutely necessary. I figured I'd check and see if anyone here had any experience good-or-bad with the Dorman, Mevotech, or any aftermarket brand arms.

I noticed some slight variation among both aftermarket and oem arms (depending on year, I'm assuming). Some come with a long/large triangular hole stamped out of the middle whereas others in the same generation do not. Also, some models use a bolt and nut to secure the shock to the arm via a bolt hole whereas others use a threaded stud welded to the arm in the same location. Not sure if these subtle differences are worth narrowing my part search but figured I'd see what you guys thought about that just in case.

4x4junkie · Aug 9, 2017

I've heard reports on arms with the shock stud, the stud can break off when you go to loosen the nut to remove the shock (due to rust/corrosion). The ones with the bolt won't have this issue (if the bolt breaks you can always replace the bolt). I believe the stud design started for 1989 models, but they are for the most part interchangeable across all years having the twin-beam front suspensions (some early arms may have smaller axle holes you might need to drill larger to use on a later year axle).

As simple as the OEM-style arms are, I don't think there would be any major issues with aftermarket OEM-replacements (as opposed to extended radius arms made for suspension lift kits). Just stay away from any welded-together arms (if there is such a thing). The threaded stud being welded in at the end of the arm is OK however.

Have you tried looking first for a replacement arm in a wrecking yard? This would be the first place I'd look, as this is a part that doesn't normally go bad or wear out, with the possible exception of it rusting out. If rust is an issue where you are, you might be able to get one shipped out from a yard in another area of the country.

a2thy · Aug 10, 2017

Thanks for the reply. Very helpful.

I had a hunch that a load bearing stud + economy weld + corrosion + time = trouble. So if I have to go with a welded stud, I'd consider coating it in some Chassis Saver or something and keeping it as clean/rust-free as possible.

To my shock and dismay, the closest junkyard that was willing to pull and ship the ship the part was over 150 miles away! That put the total cost at $65. About $30 more than a new aftermarket arm, shipping included. There must be hundreds of these used arms floating around my local area. The yard workers probably just don't want to pull them, given how much of a PITA it is to get that I-beam/coil spring bolt out.

a2thy · Aug 10, 2017

Thanks for the reply. Very helpful.

I had a hunch that a load bearing stud + economy weld + corrosion + time = trouble. So if I have to go with a welded stud, I'd consider coating it in some Chassis Saver or something and keeping it as clean/rust-free as possible.

To my shock and dismay, the closest junkyard that was willing to pull and ship the ship the part was over 150 miles away! That put the total cost at $65. About $30 more than a new aftermarket arm, shipping included. There must be hundreds of these used arms floating around my local area. The yard workers probably just don't want to pull them, given how much of a PITA it is to get that I-beam/coil spring bolt out.

Captain Ledd · Aug 10, 2017

They should interchange with the old/new style. I have a 1995 beam (would have been stud style) and the original '84 arms under my 1984. That also would be a dana 28 going to a Dana 35, still fit.

I would go with the older style with the bolt and tab, and not the stud for reasons mentioned above.

And yes, it is an absolute PITA to get that stud out. I broke a 1" box end trying to get mine out. That was after I ground the hex down because I rounded the first two sizes off.

a2thy · Aug 10, 2017

Now it appears as though there are at least three different styles of radius arms to choose from: those with a bolt hole, a welded stud, or a tab in addition to a bolt hole. This being the case, only if the "tabbed" variety you mentioned are compatible with 2wd models. Please correct me, if I'm wrong. Also; if anyone knows what makes any type of the 4wd arms incompatible, that information could be just as helpful. The more information we get on these, the better. I'll do my best to make heads or tails of it and hopefully help point others in the right direction, in the future.

4x4junkie · Aug 10, 2017

I suspect 4WD arms have a wider opening where they mount to the axle than 2WD arms. I can't swear to it though as I haven't directly compared them (4WD arms are 5¾" wide where they go around the axle).

Captain Ledd · Aug 10, 2017

The Tab is not a 3rd style. There are only two.

One, has a welded stud. This is the newer style.

the second, Has a bolt that goes where the welded-in stud would otherwise be. To hold the other end of the bolt and keep it from flopping around, there is a little metal triangular bracket/tab that also bolts to the arm. This is the older style.

Top picture is the New/Stud

Bottom picture is the Old/Bracket (tab)

Captain Ledd · Aug 14, 2017

4x4junkie said:
I suspect 4WD arms have a wider opening where they mount to the axle than 2WD arms. I can't swear to it though as I haven't directly compared them (4WD arms are 5¾" wide where they go around the axle).

Measured mine with a cheap square (all I could find, was about to head out).

4wd arms are indeed pretty close to 6" on my square (I'll just assume they're 5 3/4"

the 2wd arms measured solidly around 5", definitely without a doubt about an inch less than the 4wd arms.

Measured on my '97 2wd, '97 4x4 donor, and my '84 (original arms) with the '95 axle beam.

OE-style Aftermarket Radius Arm Quality?

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