Old Stumpy dropout issue.

I have an old Stumpy with horizontal forward facing dropouts; late eighties or early nineties frame depending who is telling me, I bought the Stumpjumper book but it's not in there - thanks Specialized. Twice now, on the same short sharp climb, the rear wheel has pulled loose from the dropouts and I've had to carry the bike home because a threaded axle is more in keeping with the age of the bike than a qr. Not that I actually know the age of the bike... anyway, on inspection the dropouts don't appear damaged, and this only happens on severe climbs. Assume that I've tightened the bolts correctly - is there anything else I could do to prevent this happening?

The following photo has been scavenged from the internet, it's not my bike but demonstrates the type of dropout I mean.



Thanks.

My 1996 Diamond Back Apex has a similar dropout issue - as with yours, on the odd short sharp climb, where I'm putting in absolute maximum power, the wheel axle has slipped out. The only solution I found was to change my Ti bolt up skewer with a Shimano steel QR that I can do up ultra tight using some brute force. The Ti was just too stretchy and I partially rounded the allen key bolt trying to get it tight enough.

My irritating drop out issue is the only fly in the ointment for what is an otherwise nice bike.

I built a stumpy for a friend on a budget and had the same issue. Solution was to use a nice strong set of skewers with a lot of knurling on the ends. I had used old skewers but they were quite worn so didn't have enough purchase, even when really tight.

This Stumpy doubles as my pub bike. Bolt on wheels seem to prevent thieving fingers... and it would be slightly ott to change the rear hub for the sake of this one climb.

Check the cone locknuts are the right way round and not damaged. Do you have washers between the frame and hub bolts?

Cone locknuts are present and correct. No washers between the frame and hub, washers outside the frame under those bolts.

Longer spanner then?!

New nuts, they do wear out (I'm aware how wrong this sounds).