I seem to remember people telling me not to use stainless bolts on suspension parts. I always thought it odd that some parts like that were available in stainless.
One of Mart's recent youtube posts addresses this. He shows new nuts where the taper is nothing like an original wishbone nut seat.
Exactly. And that was the point of my previous post. When you subject the perch to loads for which it was not designed without knowing exactly what they are, and what the perch can take, all bets are off. Bob
It depends a lot on the grade. The 300 series of stainless ( 302, 303, 304 , 316) steel cannot be hardened by heat treatment due to their low carbon content. The 300 series will work harden with processes such as bending, rolling, forging etc, The 300 series is the most corrosion resistant. Because the 300 series cannot be hardened (Therefore increasing strength) probably not the best candidate for a suspension parts. However the 400 series (410,420 440, etc) of stainless steel has a higher carbon content which makes it hardenable by heat treatment. The higher hardness and therefore increased strength make it suitable for higher stressed parts. The 400 series is often used for forging and fasteners. The 400 series is not as corrosion resistant as the 300 series but still much more corrosion resistant then the plain high strength carbon steels
Maybe, but I’ve been given the gears over running a single reservoir brake reservoir and how I’m going to die on here, so I wouldn’t be surprised.
Stainless has a bunch of different make ups as the 300 series has a a bunch of nickel making it less prone to rust and good food grade and not good strength . The others 400 series has less nickel but more chromium to give it strength but still not that strong. The 17-7 has more chromium then nickel with a good iron content and good for strength. The problem with 17-7 is it will rust if not attended to. Stainless is good for dress up goodies but would check to see series for suspension components. As for original spring perches the threads were roll formed and not cut. The aftermarket are cut threads and added stress to the materials...
Ok , I had the exact thing happen to a perch 40 years ago , yes I said 40 on a 32 sedan with a dropped axle . At the time the perch came from PETE & JAKES . Was replaced at no charge . Hard to say what caused it , was my shock mount loose and moving causing stress on the part or a defective part . Since then I’ve never had a situation like this and I have lots of miles on both my coupe and roadster , and other cars I have had a hand in building . Since this incident I’ve always made sure the nut was tightened and seated in the shock mount properly . Also used locate . Some have key ways to stop the nut from loosening . As many of you know the nut will work loose and the shock mount will swivel . An opinion from a pro builder or supplier would be welcome I’m sure . Just my two cents .....
That unit was installed "Rolling Bones style". The car had no provisions to keep it from dropping to the ground with the axle in front of the crossmember and no nerf bars or anything else to catch on the axle. I can't remember the particulars on why the owner thought it broke but I am pretty sure he installed it himself.
I talked to Roadster Supply on theirs. This is their reply. FYI. So factually SoCal perches are cast and made in Taiwan. Not forged.
Thanks for the heads up @Fry and I would be surprised that a USA manufacturer is still around. We stopped manufacturing brake springs for the automotive industry . This is when it took longer to do the paperwork then making the springs.
Apparently roadster supply has changed suppliers as they used to be forged when So-Cal had them? I have some early So-Cal perches that I know are forged because before I used some of them for a special project I had them checked (for what it's worth)
Would be interesting to know what alloy of stainless steel or steel is being used in the investment casting.
I think those street rod lower shock mounts put bending loads on perch bolts in addition to the clamping loads for which the perch bolts were originally designed.
If that is directed at me, I do not run those. My lower shock mounts are welded directly to the wishbones behind the axle.
If your running a dropped axle aren't you adding leverage when the brakes are applied and therefor overstressing that area? Sounds like a magnafluxed original pair might be the best solution. Shiny isn't that important. $.02 worth.
Interesting that even though Roadster Supply told you they're cast they're advertised as forged? I have sent Ray the owner a message to get this clarified. I don't want to be spreading false information.
The center section of the axle can twist fairly easily and does't subject the Perch bolt to nearly the force applied to it under braking. JW
Bingo!!!!!!!!!!!!! Also, the perch bolts for the 28-34 are designed to be used on an axle with a 2'' boss and a much thinner section on the top part of the radius rod. So when used on a later axle with a 2 1/4'' boss and the later thicker radius rod (for the canter levered spring, 35 on) you will find the perch bolt is only supported by about 3/4 of the axle, ad an axle drop to the mix and you have a serious issue. I discovered this while rebuilding my RPU. My fix was to turn down a matching nut to the size of the shaft and lock it on with loctite. JW
No; I wasn't trying to relate that to your perch bolt failure. It was just something I thought fit this discussion. I seen so many of those mounts rotated off to the side and even a couple bent; along with shocks mounted with very limited compression room.
Flop did not build the 3 window you are referring too. My good buddy @hotrodderhaag built it, did an amazing job on it. It was set up the similar to the rolling bones cars. Flop just chopped it. And the perch that failed on it was a Speedway perch that was apparently junk from the get go.
It would be interesting to see photos of the failures. You can learn a lot just by studying the failure mode. Bob
If I remember the pictures of the failed perch the taper had been machined off which may have created a shear point? After the crash pictures were shown on here there were some great computer generated images by the boys at Hot Rod Works that compared the various loads generated by the different ways of mounting the perches, it was enlightening.
Any word on any of the original style Bob Drake perches failing? Sent from my SM-A705W using The H.A.M.B. mobile app
Fry is right, I was wrong I just heard back from Ray at Roadster Supply and their perches are now investment cast. I wonder what investment cast means? If I wasn't so long in the tooth I'd tackle making a USA made forged perch but at 75 it's to late.
I thought the same thing, I’d think there would be a market, maybe not. If one was to buy one from roadster supply would you buy the stainless or plain steel version?
The Jalopy Journal
