How do 818 axles break?

[Dave 53]

I guess I know how they break - twisting them too hard. What I really mean is, what is the point of failure? What is the weak link?

The outer CV shaft that goes into the hub sheared off in my case. Are there other points of failure experienced? Outer CV bearings? FFR provided axle shaft snapping? Inner CV joint failure? Something else?

I will assume there is a range of parts quality from cheap ebay parts to some source unknown to me that makes super strong 1000hp high end professional race car parts. If you've had an axle failure, please share the perceived quality of your parts. If you have higher end / strengthened axles or CV joints, please share.

Factory Five currently sells the FFR axle shaft for $95. And they sell a complete axle with both CV joints installed for $159. $64 for two CV joints installed - I'm gonna guess those CV joints are on the extreme low end of the spectrum. The build manual suggests parts from AutoZone.... I believe the original purchaser of my kit bought the complete FFR CV installed axles. $110 for the pair in 2017. I suspect the CV joints are of the lowest AutoZone quality. Is it enough to rebuild with Subaru OEM CV joints?

I'm trying to figure out my strategy for fixing my broken axle. And give the same treatment to my unbroken axle. And have a spare. Hearing from others about what has failed and what has been working on a track car or maybe even more relevant, an autocross car would be most helpful in coming up with a plan.

axle broken.jpg

[EZ$]

Damn Dave! You need to make a list of all the things that could fail and start checking them all out! I was going to see if you were heading over the C&C on Friday, but I think I know the answer. I think all of this falls into the "if it wasn't for bad luck..." category.

[Dave 53]

Damn Dave! You need to make a list of all the things that could fail and start checking them all out! I was going to see if you were heading over the C&C on Friday, but I think I know the answer. I think all of this falls into the "if it wasn't for bad luck..." category.

I'm analyzing everything between the gear shift knob and the tires and between the gas pedal and the tires. I'm analyzing what parts are still left over from the previous owner that I don't know the history of. There may be others beating their 818 as hard as I do out on a track, but no one harder! Add to the list of what it takes to make an 818 into a proper track car - something better than AutoZone axles! Just trying to figure out what that "something" is.

[Hobby Racer]

I've got hundreds if not thousands of track miles on my 818R using the FFR axles and Subaru OEM CV joints with no issues. Any shock loading like dumping the clutch or burnouts combined with sticky tires will put an extreme load on the axle shafts.

They will brake at the narrowest point or where there is a sharp corner from machining/forming (stress riser).

[Rob T]

Original axles on my car failed at the outer CV making crunching sounds. I did not wait for a total failure. I went with DSS axles. Since then I've had 85+ 15-20 minute track sessions. I probably drive at 7/10.

[Dave 53]

Original axles on my car failed at the outer CV making crunching sounds. I did not wait for a total failure. I went with DSS axles. Since then I've had 85+ 15-20 minute track sessions. I probably drive at 7/10.

Were your original axles the FFR built complete axle sets?

[Rob T]

The original axles were NAPA rebuilt.

[Dave 53]

The DSS axles are $1,600 a pair. The FFR axles are $320 a pair. Any sayings come to mind?

There are a couple of options in between, but for peace of mind, I'm getting the DSS axles.