Anyone broke an inner part of axle?
 

Seems like most I see on here are the outer CVs breaking. Car wheel hopped on launch and broke the driver side inner.

Heres the video. I was trying to take down a hellcat


Attachment 223250
Attachment 223251

So to clarify, the CV didn't break. The floating axle broke, time for an upgrade.

Okay thats what i thought. The actual shaft broke. I was confused because it didn't look like other pictures ive seen.

Im going to stick with oem units for now and keep them as my weak point. It wheel hopped really bad because i had the launch rpm basically perfect between full wheel spin and bogging.

Im going to address the wheel hop and see if i can get a few passes out of mazda axles

Wrinkle wall or street tires?

Wrinkle wall at 20psi. Probably would help if they were lower but any lower pressure and the back end of the car sways on the big end.

That sounds scary

time to beef up the rear end moar. hop is gonna do some serious damage if you don't
I actually had better luck launching from 2nd and playing with the LC settings to feed in boost gradually on launch

Turns out the outer part took some damage too
Attachment 223316

Identical break
 

I recently broke the RHS axle in the same place, launching on (approximately) 40TW semi slicks. Once I had removed it from the car, I noticed that it also had fractures leading diagonally into the splines on the outer end - similar to yours.

These axles have seen hundreds of launches over the last 5 years, including earlier days when I was still working out how to launch sticker tyres without inducing wheel hop.

I have ordered a set of “400hp” DSS axles.

https://cimg7.ibsrv.net/gimg/www.mia...24631775a.jpeg
https://cimg1.ibsrv.net/gimg/www.mia...3292a5cea.jpeg
https://cimg4.ibsrv.net/gimg/www.mia...2ae33d724.jpeg

Whats your method to launching without wheel hop?

Given that I'm the guy who also has a broken axle, I may not be the best person to ask... ...and I know nothing about launching wrinkle wall drag tyres on a drag strip...

However, my understanding of wheel hop in a Miata is that it is essentially caused by the wheel cycling between grip and wheel spin as the suspension arm bushings load and unload. Essentially:

Step 1: suspension arm bushes are unloaded and the wheel is not being driven
Step 2: The clutch is released, transmitting drive to the wheel. The wheel grips the track and propels the car forward. As the wheel moves forward (slightly more than the car), it loads up the suspension arm bushings and compresses them - the wheel moves forward until the bushings are compressed, and as it does, additional toe in occurs, reducing available grip (sqwat and additional camber is also happening which reduces grip)
Step 3: The bushes reach the maximum compression as the wheel toes inwards and the wheel breaks traction and begins to spin
Step 4: As the wheel spins, less torque is transmitted to the ground, allowing the bushings to return closer to normal position, and toe in is reduced and the wheel regains traction
Step 5: The wheel grips the track... and so the cycle repeats

In my case, with stock suspension arm bushes, a higher RPM launch that is enough to keep the wheel spinning seems to prevent the cycle of hop from beginning because the wheel never regains enough traction until the car is properly moving and I'm changing into 2nd gear.

I plan to upgrade to Delrin bushings as soon as SADFAB are ready to sell me a set. My hope is that this will take some of the forward/backwards compliance out of the rear suspension and make hop easier to control at lower RPM.

Someone else chime in with more expertise!

My plan is bracing the drive train. Ill see how it goes next trip to the strip

Reduce compliance from drivetrain, slip clutch on the launch = good 60' time and no wheel hop.

Ive broke maybe a half dozen like that over the years. always by the inner CV usually the inner cv housing gets divits where the ball contact it first and the inner cv starts getting angular slop. at first I thought it was that I was putting over 300 ft lbs on Hoosiers but we have also broke a couple on the CSP car. Normally I've found good used OEM ones last better than parts store stuff. Put some new Autozone ones on the CSP car been in 1.5 years they are completely rusty on the outside and the inner CV's have a good amount of angular slop, absolute garbage compared to a decent junk yard set. Car has no rotating mass a twin clutch and gets launched hard all the time.