Maybe you have a third party app connected to Strava which is assigning the old bike to the activities.

Oh man, that might have been it. Will know soon enough! 

Hey @Cwoodffr, 
If what @Jan_Mantau noted isn't the issue, the retired bike may still be set as a default. Follow these steps to fix this:

• Go to your Gear page on Strava:  strava.com/settings/gear


• Expand the retired bikes section


• Hover your mouse pointer to the right of the bike in question


• Select "un-retire"


• Remove the default setting from the bike, then you can retire it again

Yes I have done this multiple times to ensure there was nothing selected, or specifically one that I never do.

Then it may be the third party app! We do have another post where the user had the same issue; you can check it out here: Activities defaults on retired bike
Let us know if you still have issues after checking your third party apps. 

Reporting back. It was a third party app. All fixed. Thanks!! 

Hey @Cwoodffr, 
Thanks for the update; glad all is good now!