Club 80-90 Forums

Sorry if this is a daft question. My new speedo cap (square hole in centre) has fell off never to be seen again after only doing about 5 miles. It didn't seem as tight as the original which had fell off the week before. I tapped the new one on with a rubber mallet but thats not made it stay on. Could it just be the new one was not a good fit or is there something more sinister which caused the two to drop off. Just ordered a third one today   Thanks