along the vein of what 34_40 mentioned you may have too skinny of belt .. see if all your pulleys look to be the same size if so then perhaps go with a size wider belt .. i have`nt fooled with belts in a long but gates used to size their belts by the first digit being the width then the second 2 or three being the length .. such as a 7350 would be 7 being a standard width and the 35 being how long it was and the 0 being no fractions .. a 8352 belt would be wider and be 35.2 inches long ..