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PRODUCT BULLETIN:

IMCA AIR PRESSURE, SIPING & GRINDING TIPS

3-06-09
By: Shanon Rush
1) What is the proper air pressure for the IMCA tire?
a. Temperature profile across the tire is the best indicator
- If your temperatures are even across the tread, your pressures are correct       
b. We always recommend running the most pressure possible
- Under inflated tires will feel soft, squirmy, unresponsive
- Over inflated tires will be loose with little traction, “on top of the track”
c. Standard IMCA Modified setup:
- Heavy Track - 15 right side, 12 left side
- Slick Track – 14 right front, 10 left front, 13 right rear, 8 left rear

2)  How should I sipe my IMCA tires?
a. Why do we sipe?
- To build or remove heat
 
1. We sipe across a tire to increase wear and build heat. 
We sipe around a tire to reduce heat and increase sidebite when additional traction is not necessary. 
- Reduce block stiffness and increase wear on tires too hard for track conditions     
b. Siping tips
- We generally never sipe more than ˝ depth of any block. 1/3rd the depth of the block, or 3/32nds, is preferred in most   situations.
- The more sipes you apply, the shallower they should be. In turn, the less sipes you use, the deeper you can cut while still minimizing the risk of chunking.
- The more evenly you can space your sipes within a block, the better their performance will be. You should always try and limit the amount of small, unsupported corners of a block to reduce tread chunking.
- Unless facing severe track conditions, IMCA tires seem to like aggressive siping, both across and around, the tire. In turn, if the track is severe, only shallow, circumferential sipes should be used to help reduce temperature and possible tread blistering. Taylor your quantity and location of sipes to the track conditions; the easier the track, the more sipes and vise versa.

3) What is the best siping tool to use?
a. I have no preference on how sipes are created. All the tools I have seen accomplish the goal, it just depends on what your budget will allow. I personally use a 4-8 blade unheated hand siper available from many IMCA parts suppliers.

4) When and how should I grind my tires?
a. I prefer a light grit sanding disk on a variable speed, high torque grinder. I am only looking to remove the surface “shine”, not cut away layers with my grinder. If you see smoke while grinding, reduce your grinder speed or disk grit.
b. Generally, I prefer to sand/grind before I sipe to assure my sipes maintain their attended depth.
c. I would much rather sipe and sand a tire than use one of the aggressive grinding disks currently in use. There is very little control on depth, size, and location of the “sipes” created by these grinders.

  

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