Did I buy the wrong backing plate?

A

avalys

New member
I just bought a PC 7424, along with a 6" flexible backing plate and some 6" pads, from CMA. Their site recommends that backing plate / pad combo, so I didn't do much thinking about it.



But, reading on here, it seems like the consensus is that using a 5" backing plate is better, because it gives you some safety margin if you screw up.



How much of an issue is this, really? I was really looking forward to detailing my car this weekend, and I don't want to have to go hunting for another pad on Saturday morning. Should I go buy a 3M 5" pad from some auto parts store, or will the 6" one be fine for my purposes?



My car is really not that badly swirled - I'm thinking that one pass with 3M Perfect-It III Machine Glaze will take care of it. I will probably end up doing the tight areas by hand anyway.
 
merci said:
I think what kgb meant it gives you more room for error.



CMA's 6-inch pads are really 6.5-inch pads. :D
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Opps! That is what I meant! Plus the Curved Variable Contact pads are resessed which keep the backing plate away from paint all together.
 
I have that pad combo and can tell you that I prefer the 5" better. Its not a problems with backing plate sctratching the paint as the pads are slightly larger than the plate, but as Patrick said the velcro is smaller than the backing plate. See when you start to apply some pressure to the pad the backing pad grinds into the blue part of the pad that is not covered by the velcro and start eating away the foam. It tends to reduce the life of the pad over time. I would either use different pad like the 7.5 or call up CMA and ask if they can swap you for the 5".
 
Agreed. It seems to only happen to my white polishing pads, but I'll be sure to confirm the velcro is at least 5.5" wide on my next set before I order them.:doh
 
jetskie said:
I have that pad combo and can tell you that I prefer the 5" better. Its not a problems with backing plate sctratching the paint as the pads are slightly larger than the plate, but as Patrick said the velcro is smaller than the backing plate. See when you start to apply some pressure to the pad the backing pad grinds into the blue part of the pad that is not covered by the velcro and start eating away the foam. It tends to reduce the life of the pad over time. I would either use different pad like the 7.5 or call up CMA and ask if they can swap you for the 5".
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Hmm, interesting.



Perhaps I can put some tape on the outside edges of the backing plate for this weekend, and then swap it out next week. I really don't want to wait another week, and it looks like the weather is going to be good too...
 
While you can use a 7.5", for the PC, the larger the pad, the less the pressure is concentrated and the larger the span on non-flat surfaces so it actually takes longer to buff the car. Ironically, a 7.5" pad for a rotary has the opposite effect, it's too strong because the outer edge is spining faster and more risk of marring. So I would get the correct 5" backing plate and be careful with the 6" plate/pad combi in the meantime.
 
I think you are fine with the 6" backing plate and 6.5" pads on a PC. I've done several cars with that combo and while I have seen some light "cookie cutting" of the pads due to the backing plate being larger than the pad backing, it hasn't destroyed any pads yet. The less pressure you use on the PC the less chance of cutting the pads. If you use the right product and pad combo you might need to make an extra pass or two for signigicant polishing needs or scratch removal. I've found that heavy pressure isn't necessary and bogs the PC down. Remember the PC isn't a rotary and you will probably spend most of your time polishing, not cutting.



I purchased a Porter Cable 5" flexible backing plate and weight from Coastal Tool online and tried that with my LC pads and my Meguiars pads. My experience has been that the 5" plate works best with the Meguiars pads and the 6" plate works better with the LC pads.



After buying a PC backing plate online I noticed that my local Home Depot had the 5" PC backing plates inthe tool corral in the back. Same price as online. If you really want to use a 5" backing pad without waiting, try your local HD.
 
Mike,



I'm trying to search out the PC backing plate on HomeDepot's website, but I can't locate it. I need a 6" plate by tomorrow and would like to just pick it up at my HomeDepot.
 
I didn't look it up on the HD web site, so they may not sell it through the web. I just happened to come across them at my local Home Depot while I was looking for a drill bit. I wandered to the back of the tool corral and there they were on the wall. I'd just call the local HD and ask the tool crib person to look for you.
 
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