Spacers have always seemed to hold and live up to their strength and durability capabilities, very few instances of full failure are documented, even on the race track...I have the 5" total on the rear, 2.5 per side and they have not budged, and I beat them. I am replacing them with a Banshee axle soon which I have in my garage, just waiting for a winter rip down to do some other things as well, but the spacers have been great in the back.
Running spacers on the front of quads has always been controversial since front wheel spacers cause the wheels to go through a forward and backward sweeping motion when going through the steering range, which can cause force feedback to the rider and a tendency for the ATV to steer itself/bump-steer/over steering, etc, etc...
This is why things like extended A-Arm kits and front wheel flipping, etc, are so much more popular and definitely recommended as the procedure to follow, to get a wider front end on an ATV. I personally chose a much cheaper route than doing a FULL A-Arm upgrade, etc, and still got a full 9 inch stretch over stock. I used a product from Diamond J, their A-Arm extension kit. This kit basically re-locates all the mounting points for your stock equipment, widening each side 3 inches. The braces/brackets are heavy duty and super strong, race proven and actually much nicer than I anticipated on them being. They can be painted and customized to match your bike, etc, as well... I have now fitted Banshee shocks up front on the kit and the performance is perfect. a 400EX rear shock to finish it off and a substantial upgrade now over the stock suspension, all for less than $300 with the kit, shocks, etc.
There are 2 DJ kits available, a 4.5" and a 6", I went with the 6". Between this kit and a front wheel flip you are 9" over stock on the blaster, how can you beat that utilizing all of your stock suspension components, still leaving room for future upgrades if desired, all for under $200???
Brilliant, Just thought I would share this with you guyz/galz...
check um out here if interested:
Diamond J Kits for Blasters