ballzout

Looking for reasons why we've broken 2 axles in 14 months ( 24 races ) right at the stub axle ! I've heard the newer cars come from PMNA with the stub axle only tourqued to about 200 ft. lbs, and over tourquing might be a cause.
Something we noticed with our complete new set up was how much slop there is on the threads of the stub on the new axle, with a stock bolt on the axle we recorded .002 of play of the bolt shoulder, and with the stub axle threaded all the way to within 2 threads of the max, it has over .010 wobble?
I'm using a Cup axle ( 90 ) this time instead of a GT3 street( 16) and a completely new suspension set up. It's happened both times on the left side, if it does it again, I'm going on a diet !

racerfb1

try running the car at the recommended ride height, if you go lower than Porsche recommends u will break axles due to the angles

claykos

Heavy curb hopping while on the power will cause the axles to break after awhile. Do you frequently run on a track where you hop the left side over a curb?

ballzout

Actually NOT, these things are so highly over sprung, I learned early on to keep off the curbs, but now that you made me aware, I will run even further outside the curbing !

ir_fuel

Just drive in the middle of the track. Not only will your axles live longer because of no curbs, but nobody will be able to pass you!
It's win-win!

Surfbum

Does anyone know what PMNA suggests to change out axles on 996 & 997 cups?
I know some of the WC guys change out at 25 hours, but they are doing standing starts.

ir_fuel

I thought axles was every 40h?

Glen

Check left rear upright for wheel bearing play. Is it moving inside the upright, ie wallowing out. Not the bearing itself but where the bearing presses into upright. Will only show itself when hot, will be tight when cold.

Dont worry about curbs etc..had 17000km on my last car still original halfshafts, ran over curbs, thropugh grasssover jumps etc....

michaelmount123

Glen's the voice of reason, eh? What, you don't drive in the middle of the track??

amso3

Here is what is published in the '06 Cup manual. I doubt the Porsche shipped the cars with 200 ft lbs torque on the axle nuts

OlsenMotorsports

Axles are timed out at 25hrs..... With a Hollinger box no lower than 105mm rear ride height and newer RSR box can go down to 90mm rear ride height.

200ft lbs max torque with no anti seize on the face of the stub axle where the nut seats. Add a dab of red loctite and you should be good to go.....

+1 to wheel bearing play and big curbs

Bernie930

Since when has PMNA recommended 200lbf for the axle nut? Please show me, have been running them at stock settings forever without breakage, incl 24 hr events, not incl CV failures of course

ballzout

Great input guys. I have thought about ride height, will be checked for sure. Bearings were old, so much so the ***** were blue ( this ought to get some post replies )with crust for grease, not to mention the serious play in hub on the upright as we tore it apart ( broken axle without pressure holding it together... much of course) ! Todd Opperman said every 11' and newer cup he's took delivery on has had about 200 ft lbs at the stub, after a session they re-torque them up to around 300 and go racing without fail. Olsen, what was the red Loctite on? and the +1 bit about ... splain more !
Rp

Glen

Lol, not usually. I'm an unpaid durability tester. Middle of track is great for equipment and bad for results...

Michael, how are the hotrod projects going?

michaelmount123

'Scuse the digression; no hijack intended.....

Just finished a GTA 4.0L, Glen. Had hoped to run it on an engine dyno, but time interfered with sorting out a harness. Will run on a chassis dyno then track test next week.

...back to axles, curbs, slammed ride heights and and worn out suspension components....