Rear wheel keeps shifting

[NotRequired]

I just tuned my '76 Schwinn cruiser up for spring, and after riding as far as my daughter's bus stop my rear wheel has shifted over far enough that the tire is hard against the frame. So I readjust, tighten it back down, and in the same time my wheel has shifted again. It's gone as tight as it can. I'm wondering if the mounting brackets of the fender are causing the nut to slip. Perhaps moving them to the inside of the frame would help? Any suggestions?

Edit: It only seems to be the drive side that slips. The chain is loose and the tire presses against the non-drive side under the seat post at the bottom of the frame.

[jtj]

(03-14-2016, 05:01 PM)NotRequired Wrote:  I just tuned my '76 Schwinn cruiser up for spring, and after riding as far as my daughter's bus stop my rear wheel has shifted over far enough that the tire is hard against the frame. So I readjust, tighten it back down, and in the same time my wheel has shifted again. It's gone as tight as it can. I'm wondering if the mounting brackets of the fender are causing the nut to slip. Perhaps moving them to the inside of the frame would help? Any suggestions?

Edit: It only seems to be the drive side that slips. The chain is loose and the tire presses against the non-drive side under the seat post at the bottom of the frame.

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(04-01-2016, 07:13 PM)jtj Wrote:  

(03-14-2016, 05:01 PM)NotRequired Wrote:  I just tuned my '76 Schwinn cruiser up for spring, and after riding as far as my daughter's bus stop my rear wheel has shifted over far enough that the tire is hard against the frame. So I readjust, tighten it back down, and in the same time my wheel has shifted again. It's gone as tight as it can. I'm wondering if the mounting brackets of the fender are causing the nut to slip. Perhaps moving them to the inside of the frame would help? Any suggestions?

Edit: It only seems to be the drive side that slips. The chain is loose and the tire presses against the non-drive side under the seat post at the bottom of the frame.

I am no expert but maybe dish has shifted.