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My last landing, my Sonex pulled pretty hard to the right. Thought I lost a bearing or my brake froze or something. This is what I found....

Interesting. Never saw this before or heard of it happening to anyone. Was the bolt installed with a NEW AN365 Elastic Stop Nut (some people call it Nyloc or such) when assembled, and if so was the nut still attached the bolt or missing? A lot of heat is generated in braking but never enough to melt the nylon and allow it to back off. Even if not torqued down all the way I can't imagine it would back off either. Perhaps no nut installed or wrong nut used?

Kip mentioned having seen broken wheel bolts before and recommends upgrading to AN hardware:

viewtopic.php?f=21&t=319&p=2322#p2321

If your bolt did break, you are not the first person it's happened to. I'm using the bolts the wheels came with and haven't had any issues yet.

I wonder what caused the Sonex to pull hard? Did the bolt catch on something?

I didn't get too far into the issue. I was short on time and figured I'd have to order some parts anyway. I'll say, right off the bat, that the bolt is a generic stainless variety and AZUSA calls out for cad steel. I have the Tracy O'brien brakes on my plane. These bolts run through the wheel and stick out the back where the tips provide the catches for the brake rotors. They have the threads filed off the ends where they catch the rotors. Honestly I didn't look to hard at the nut side of things yet. I don't think the bolts are original to the wheels. They appear to be a mod to make the brakes work.

Just happy I didn't go spinning off the runway when the bolt caught the outer bracket of the wheel pant. Bent the bolt and did a minor number to the bracket. I guess its kind of lucky it had softer stainless bolts. A higher grade may have held fast and exploded the pant or completely locked that wheel.

All six bolts will be replaced with cad plated real steel. Nuts will be replaced with high temp nyloc. While I'm at it I think I'm going to replace the axles with O'Briens.

Bad picture but you can see the bracket for the pant. Near the top right (over the aluminum corner) you can sort of see where the fiberglass is discolored (more yellow) where it took a hit from the bolt.


Bent bolt where you can see the tip has been worn where it comes in contact with the disc.

This is not common, but it does happen. I've had it happen on standard category planes with AN hardware as well. It doesn't hurt to pull the wheel pants off and check tires, wheels, bolts, etc. every now and than!

it that a crack in the wheel below the bolt? How about using metal locking nuts if heating of the AN365 nuts from prolonged braking is an issue.

waiking59 wrote:it that a crack in the wheel below the bolt? How about using metal locking nuts if heating of the AN365 nuts from prolonged braking is an issue.

So it appears. Might just have to get a new wheel too.

Yours is not the first report of this. Replaced all of mine with AN bolts. Note: If those are the larger 5.00 x 5 tires, you do not need more than about 25 PSI, and definitely not the 50 PSI Sonex recommends for the small tires.

David A. Sonex TD

PS: Wrote this before finding your later post with info on heating from contact with brake disk. That would do it with any type of nylon locking bolt.

My Tracy O'brien Brakes came with stainless Bolts and all metal lock nuts. Is that what was originally
on yours too? I ask because they have a lot of wear on them, so I wonder if I should order new ones. I have near 800 hours on mine. Not sure if I can find AN hardware with enough threads to allow me to get the disk pin machined. I suppose I could just thread it more...

Regards,

Robert,

N157SX.

rbarber wrote:My Tracy O'brien Brakes came with stainless Bolts and all metal lock nuts. Is that what was originally
on yours too? I ask because they have a lot of wear on them, so I wonder if I should order new ones. I have near 800 hours on mine. Not sure if I can find AN hardware with enough threads to allow me to get the disk pin machined. I suppose I could just thread it more...

I'm guessing they're original to the brake system. Honestly, you knew my plane before I did and I haven't run through the books to see where/when these brakes were added. I still haven't figured out what I will do yet but I think I'd rather have hardened bolts on there than stainless considering the beating they take. If you'v got 800 hour on em, you might consider replacement. You can see how worn the "nipple" on mine is after 300 hours.