GearHeads Corner

I measured a couple factory made 60T XL timing pulleys and see that the depth of the root is  .050" when I create a 60T XL pulley in GM 3.02 and using the dimension feature of my CAD program I measure the depth to be .070" Why is there a difference. I would think GM would also have a .05"depth.
Dan Mauch

Dan;

Again I'm no expert in this field, however from what I understand of these, the root tolerance can vary from manufacturer to manufacturer. Since most belts do not touch the bottom of the roots, and as long as the tooth pitch and the general form of the tooth is correct, then I was led to believe that the actual fillets and roots tend to be pretty tolerant. Do you have the specification sheet of this 60T XL pulley, or is this just measurements taken from existing pulleys?


Cheers
Bob
:)

I have a batch of various  XL timing pulleys. I measured several of them and found you are correct. The root depth does vary for .040 to .070"
Thanks Bob
Dan Mauch

Hi Dan:

Yup, specs do vary, sometimes considerably.. and sometimes the written specs are purposely fudged.. weird world of pulley specs...

Art