Bolt-on VS Interference Fit Supercharger Pulleys

posted in: GTT Blog & News

Our GTT Super Charger pulleys use an interference fit system to the shaft (same as OEM pulley) rather than the ‘bolt on’ type.

As you can see these ‘bolt on’ pulleys have slid along the shaft (the big gap shown in pic) this makes the supercharger out of line with the other pulleys which causes the belt to wear very quickly or even jump off.

Also you can see that the supercharger seal retaining clip (tab seal) has had to be removed to fit this pulley on far enough (see image) This is not ideal, and could result in the seal moving and leaking.
These ‘Bolt-on’ types are now well known to slip, slide and even fall off on rare occasion.

This is often discovered during a GTT Supercharger rebuild.

Identifying the problem. A sudden loss of power will be caused by this as the supercharger has lost all drive or intermittently as the pulley jams then slips repeatedly . Also the water pump will too! Over heating is inevitable as the water-pump is driver by the supercharger, if not fixed it can result in catastrophic engine damage!

Note: If pulley slips, it can result in scrapping the nose end of the supercharger because the shaft will wear beyond the point any pulley can be installed correctly.


Another case pictured: a common brand “clamp-on type” pulley that’s been grinding against the Main oil seal!

The Seal retaining clip wasn’t present! Perhaps it vaporized or was not installed to allow the pulley to fit. (clip is required to stop the seal drifting out!)


Since 2003 when we first released our pulleys we have never known our pulley have never slipped, move or fall off, plus the tab seal stays fitted.

Mini Gen 1 GTT Supercharger Pulley