Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

[Michael Stoops]

Backing plates, that little piece that threads onto a buffer and gives the pad something to stick to, are probably the most overlooked and under appreciated bit of hardware used by a detailer. This article will explore not just which backing plate should be used with which pads, but why they go together and what can go wrong if you mismatch them. While some of you may find this a tad over involved, those of you interested in all things detailing related should find it interesting, and you hard core detailing geeks will most likely be the first with a whole slew of questions.



Size, Flexibility, Compressibility - Transferring Power To The Paint

Perhaps the most obvious aspect of pad & backing plate pairing is size. You obviously do not want a backing plate to be the same diameter as the pad because that would expose the edge of the backing plate, with potential disastrous results. In the case of a recessed back on the pad, like with our Soft Buff 2.0 foam pads or the So1o foam pads, the backing plate drops right into place with a bit of pad overlap acting as a precautionary buffer zone. But with a flat backed pad like our original Soft Buff series pads, our microfiber discs and many of our competitors pads, there is no such recess so that safety factor is not built into the pad. It then becomes even more critical that the backing plate not be of too large a diameter. As an example, you should never use our W65 backing plate with the 6" diameter Soft Buff 2.0 pads as that combination allows no room for error.

Below is a W65 backing plate affixed to a W9000 (8") Soft Buff foam finishing pad. This is a proper match as the backing plate provides ample support across the pad without encroaching too closely to the edge, leaving a sufficient safety barrier.


The is the exact same backing plate mounted to W9006 (6") Soft Buff finishing pad. As you can see, the diameter of the backing plate is almost the same as the pad, leaving very little room for error. Spin that backing plate with any speed at all and then just tap it against an adjacent body panel, trim piece, tail light, etc and you're in trouble before you know what happened. The correct rotary backing plate for the 6" Soft Buff pads would be the W64 as it is smaller and will fit the smaller loop material just as the larger W65 plate fits on the larger pads as shown above.


Here is the W67DA backing plate affixed to a DMF5 microfiber cutting disc. You can see a nice edge of the disc that prevents the backing plate from coming in contact with body panel edges, trim, lights, etc. For those of you unfamiliar with this microfiber disc and backing plate, the yellow area is the outermost area of the backing plate, and the black ring around it is exposed loop material on the disc.


Here we see what would happen if you tried to mount the same DMC5 microfiber cutting disc to the W68DA backing plate. This is shown from the face side of the microfiber disc, and you can clearly see the backing plate behind it. As you can imagine, this is just a disaster waiting to happen. But we get calls all the time asking if these two can be used together - you can see why the answer is a resounding "no!".


Here's another mismatch, but it's commonly done. If you're doing this, stop. This is a W67DA paired with a Soft Buff 2.0 foam pad. The edge of this backing plate will actually start to cut into the laminated backing, especially when used in an aggressive manner. This backing plate is just too small in diameter for this pad, so you'll be seeing a lot of this pad sort of wrapping over the backing plate, further compounding this cutting effect of the plate against the backer.





But size alone doesn't tell the full story. Backing plates come in different degrees of hardness and flexibility. The softer and more compressible the backing plate, the less ability it has to transfer energy to the paint, and some overall cutting ability will be lost. That's not necessarily a bad thing as it may well be engineered into the whole system as with our So1o system. The W66 backing plate that is part of that system is a much thicker and more energy absorbing unit than the W65 backing plate is. While both could, technically, be used on the same pad you will realize more cut with the thinner and stiffer W65, even if you're using the same tool speed, same liquid, and same pad.

On the left is our W65 rotary backing plate, and on the right our W66 So1o backing plate. The difference in thickness is obvious.


But if these two backing plates were of the same density, and therefore same stiffness, then the added thickness of the So1o W66 backing plate would be meaningless. The image below shows nearly full compression on the W65 backing plate - it's a pretty firm plate, effectively transferring power from the tool to the pad and ultimately to the paint.


This is near full compression on the W66 So1o backing plate. This thickness and compress-ability allows for excellent contouring of the pad to follow panel shapes, but also "cushions the blow" when using the M86 So1o liquid during the finishing steps. Remember, the entire So1o system was engineered so that a single liquid, M86, can be used with the wool pads and foam pads within the system for everything from sanding mark removal all the way down to final finishing.



A flexible backing plate, like our W68, allows for more uniform support to the back of the pad and therefore more uniform cut when the pad is forced to flex and bend in response to body contours. A very stiff backing plate, on the other hand, will force the pad to remain flat in these instances and you'll lose contact with the lowest point of the concave area of the panel, and therefore you'll lose uniformity of cut in those areas..

Here, the W68 backing plate is shown at full compression, which is almost nil. It's stiff as far as compression goes, but it's still quite flexible.


Here's the same backing plate showing the flexibility of the product, again allowing the pad to better conform to body contours while buffing.


There are times, however, when a stiffer backing plate is called for. In the case of our DA Microfiber Correction System the recommended backing plate, W67DA, is very thin and very stiff. When this is couple with the DMC5 microfiber cutting disc you are able to achieve a high level of cutting ability, even using a DA. Similarly, you've likely noticed that the foam on the microfiber finishing disc is thicker and softer than that of the cutting disc. This is because when performing the finishing step you don't need, or want, as much cut as you do when correcting severe defects. That extra foam thickness "softens the blow" so to speak, rather than having to move to a different backing plate for the finishing step.

The W67DA backing plate is a very firm, though not solid, backing plate. This firmness helps to direct the power of the tool through the pad and to the paint, especially helpful when working with the DA Microfiber System where heavy pressures are often used to achieve the level of cut possible with that system.

______________________________________________________

Synchronicity & Engagement: What Sticks To What, And How Well?

Some of the above is, or should be, readily apparent with just a bit of thoughtful observation. But what is equally important, if not more so in some cases, is just how that backing plate actually holds on to the pad. Sure, it's a hook & loop attachment system, that's obvious enough. But there is a lot going on in those little hooks and loops and they can prevent or cause a lot of issues when spinning any pad on any buffer, whether rotary or DA. So, let's take a closer look at what allows the pad to actually stick to the backing plate, how these hook & loop systems differ, and what happens in that tiny space where the pad and backing plate meet. First though, a few quick definitions of terms used throughout this discussion:

• DA or DA buffer: a dual action polisher such as Meguiar's G110v2, Porter Cable 7424, GG6, etc where the pad is moved in both a rotating and oscillating fashion, effectively changing direction numerous times during each full revolution
• Rotary buffer: a direct drive, high speed, high torque tool that spins the pad in a perfect circle
• Hook & Loop: commonly referred to by the trademarked brand name "Velcro", this is the two part material used to attach the pad to the backing plate - the "loop" side being the softer, fuzzy side and the "hook" side being the rougher, coarser feeling side; we refrain from using the brand name as not all hook & loop systems are made by them (just as not all tissues are made by Kleenex).
• Synchronization: a hook & loop system where in the two sides are specifically engineered to work with each other; this includes height of materials, density of materials, and shape of materials
• Engagement: the method by which the hooks & loops actually interact, both in tension (in simplest terms, a vertical pulling) and shear (in simplest terms, a lateral pulling)

For purposes of this discussion we're going to focus on two basic types of hook & loop engagement systems; "J" hooks and "micro"-hooks and their synchronized loop counterparts. A third type of hook, the "mushroom" hook - so called because of it's mushroom like shape - is not commonly used in this application.

"J" hooks

"J" hooks on the W66 So1o backing plate....


...and on the W65 rotary backing plate.


So named because they look like the letter "J" with the curved end acting like a hook that grabs onto the loop of the piece it attaches to. The shaft of the "J" is relatively long, and for the most part they are arranged in alternating rows with the hook end of one row pointing 180 degrees to that of the second row. This type of hook & loop pairing is most commonly used on rotary backing plates and the pads designed to go with them. This is a fairly long connection and a very secure one at that. Consider that a rotary buffer interacts with a pad quite a bit differently than a DA buffer does:

• a rotary always spins a pad in a perfect circle with virtually no lateral, or shear, stress; a DA moves the pad in a random orbit, changing direction constantly and placing a lot of shear stress on the hook & loop
• rotary users will often use a wool pad, which tends to be heavier than foam; wool pads are not used on DA buffers
• the angle that a wool pad is often used at (as opposed to perfectly flat against the paint) which creates a bit of a lever effect, putting the hook & loop into at least some degree of tension, or vertical, stress

These are the main reasons why a long-ish "J" hook and synchronized loop are primarily used in rotary applications. And foam pads designed specifically for rotary use (think So1o System foam pads) should also have a loop backing synchronized to this "J" hook if for no other reason than long life of the loop material. The foam may not have the weight of a wool pad, and they are generally held much flatter to the paint, but you still don't want to tear apart the loop each time you pull it off the hook. Heat isn't much of an issue because friction is greatest where the pad meets the paint, and becomes less and less as you move away from that point and toward the tool.



"Micro hooks"

"Micro hooks" as found on the W67DA backing plate.....


...and on the W86 & W68DA backing plate. You can see how much shorter and thicker these are than the "J" hooks shown earlier.


The micro hook gets its name from the simple fact that the hooks are very small. Simple enough. So what's the advantage? On a rotary buffer with a foam pad, there really isn't a big advantage to one system or the other. On a DA buffer, however, the difference is huge. Consider now how a DA buffer interacts with the pad:

• a DA moves the pad in a constantly changing direction due to the action of the tool, creating huge shear forces on the hook & loop when used on a DA
• wool pads aren't used on DA buffers and both foam and microfiber pads should always be held as flat to the paint as possible (other than limited instances of pad "edging" to remove specific, severe defects), eliminating any real tension forces

That first point is the really critical one. On a DA the direction of the pad is ever changing - it's almost like controlled chaos. Those directional changes are constantly trying to throw the pad free from the tool, and the shear forces where hook and loop come together can be very high. That shear force creates heat build up as the tool forces directional changes in the pad - directional changes transmitted through the hook & loop - which is where friction is highest with a DA tool. If the hook and loop was long there would be excessive free play in this scenario, even if they were properly synchronized.

As a bit of a side note, micro hooks came about due to the growing popularity of hook & loop engagement systems in DA sanding; long hooks would actually create high spots on the face of the abrasive media that interacted with the paint, behaving almost like a bed of nails. Not a good thing. It didn't take long to recognize that the lack of heat generation inherent in this shorter hook & loop would yield benefits when polishing paint with a foam pad on a DA tool.

Now, as you might imagine, these engagement systems come in different sizes and strengths - literally hundreds of variations - for both the hook and the loop components. That's where you start to get a sense that synchronization becomes quite important, even within a type of attachment system. When you start to mismatch these two parts then the engagement deteriorates over time:

• If the hook is too aggressive, even if it's the right type for the loop, it will start to pull the loop material apart each time you dismount the pad from the backing plate
• If the loop is too aggressive, even if it's the right type for the hook, it will start to destroy the hooks, pulling the barb straight or breaking it off altogether each time you dismount the pad

Both of the above scenarios will happen whether you're using a DA or a rotary buffer; the damage occurs simply by removing the pad from the backing plate. You do, after all, affix a pad and subsequently remove it on both tools.

But with a DA things become even more problematic due to the directional changes we mentioned above. If the engagement system is properly synchronized, there is very little free play between the two components, so heat buildup is kept to a manageable level. But lose the synchronization and things get sloppy, friction builds, and excessive heat is the net result. You don't even have to use the tool all that aggressively, or put a lot of pressure down on the pad, to generate a lot more heat with an unsynchronized engagement system than you would with a properly synchronized system. But the more pressure you do apply, and the higher the speed of the tool, plus the longer the buffing time, the greater the heat becomes. And that heat can become quite excessive, easily exceeding 200F, (we've seen well in excess of 250F!) causing break down of the pad foam, the hook & loop system itself, or even the backing plate depending on its construction.

There is one exception to all of this, however, and that is when using a micro hook backing plate with a loop that is technically synchronized for a longer "J" hook. This will happen, for example, when using the So1o foam pads (long loop) with a W68DA backing plate (short hook) on a DA, or when using the original Soft Buff 6" pads (long loop) with a W67DA backing plate (short hook). Neither side in these un-synchronized pairings is overly aggressive relative to the other, but you will sacrifice a bit of engagement strength when using these combinations. In both cases, however, you're using these un-synchronized pairings on a DA so you'll be keeping the pad flat and under pressure so a small loss of engagement is acceptable. Heat is still kept to a minimum since there is much less "slop" or "looseness" when a short hook engages a long loop than when a long hook engages a short loop.


Choose Your Partner


So, what backing plate should you be using with which pads?

• Soft Buff pads - W7000/6, W8000/6, W9000/6
  • Rotary: W65 (W7000/W8000/W9000)
  • Rotary: W64 (W7006/W8006/W9006)
  • DA: W67DA
  • Hand: S6HP for all of the above
  • Considerations:
    • both subsets of these pads (6" and 8") utilize a longer loop that is synchronized for a long "J" hook normally found on a rotary
    • historically these pads predate the proliferation of DA polishing, hence the rotary engagement consideration for both sizes; use of the 6" pads with a DA became more common and the shorter hook on the W67DA backing plate minimizes heat buildup when used with that tool
    • for rotary use the W66 So1o backing plate can be used with the W7000/8000/9000 pads if you want more edge flexibility, but you will lose a bit of defect removal

• Soft Buff 2.0 pads - W7207/4, W8207/4, W9207/4
  • Rotary: 4" pads - W63
  • Rotary: 7" pads - W68
  • DA: 4" pads - S3BP
  • DA: 7" pads - W68DA
  • Hand: 4" pads - S3HP
  • Hand: 7" pads - S6HP
  • Considerations:
    • priority for hook & loop material is given to the DA since that's where the most secure engagement must be made; remember, foam pads on a rotary should be held very flat to the paint so they don't necessarily need the security of a long "J" hook that a wool pad does, but the DA requires a shorter hook to minimize heat build up.
    • since the priority is given to DA use, all pads in this series have loop material synchronized for a micro hook, so even the rotary version of the W68 backing plate must have a micro hook
    • the recessed back side of these pads is designed to accept the diameter of the backing plate for perfect centering
    • many other backing plates, our own W67 for example, may have the right hook & loop but the edge of these backing plates is an abrupt cut off and that can dig into the laminated loop material of these pads, destroying them over time
    • the W68 backing plate provides excellent, flexible support across the full width of these pads, giving solid connection between pad and paint, ensuring uniform defect removal even along tighter body contours.

• So1o System Pads, including WWHC7 & WWLC7 wool, WDFP7 & WDFF7 foam
  • Rotary: W66
  • DA: W68DA (foam only)
  • Hand: S6HP (foam only)
  • Considerations:
    • these pads are truly part of a system and since that system uses both wool and foam pads and is designed specifically for rotary use, a longer "J" hook and synchronized loop was chosen to provide proper engagement for the wool pads, even if that is overkill for the foam
    • because the loop material on the foam is synchronized with the long "J" hook on the W66 backing plate, the foam pads really are not suitable for use with a micro hook backing plate made for DA use; excess heat and deterioration of the loop material will occur with repeated use.
    • even though the So1o foam pads are the same diameter as the Soft Buff 2.0 pads and the W68 series backing plates will technically fit into the recess on the back side, the loop material on these pads extends to the edge of the recessed area while on the Soft Buff 2.0 pads it does not - so added to the non-synchronized hook & loop with these pads and the W68 backing plate you also have limited contact between the two, making a marginal situation even worse.
    • even with that last point in mind, you can get away with using the So1o foam pads on a W68DA backing plate for DA use, but we highly discourage the use of any of the So1o pads with the W68 on a rotary buffer due to the less secure engagement.
    • optionally the W67DA backing plate can be used for waxing only with the WDFF7 foam finishing pad, or the S6BP can be used for general defect removal on the DA with foam pads only

Here is a So1o WDFF7 finishing pad next to a Soft Buff 2.0 finishing pad. The pads are the same diameter and have very similar, though not identical, recess on the back side. But the loop material is different on these two pads - the So1o pad has loop material all the way across the recess while the Soft Buff does not. Further, the loop material itself is different as the So1o is a longer loop synchronized for use with a "J" hook on the W66 backing plate, the Soft Buff 2.0 uses a short loop for the "micro" hooks on the W68DA. As stated earlier, this is one of the exceptions where you can safely use the So1o pad with the W68/W68DA backing plate.

• W4000 Cut & Shine wool
  • Rotary: W65
  • DA: N/A
  • Hand: N/A
  • Considerations:
    • this pad is not suitable for DA or hand use
    • long "J" hook on backing plate is synchronized with loop material on pad, giving a strong bond even when the (relatively heavy) pad is worked slightly on edge

• DA Microfiber Correction System pads - DMC-3/5/6 & DMF-3/5/6
  • Rotary: N/A
  • DA: 3" discs - S3BP
  • DA: 5" discs - W67DA
  • DA: 6" discs - S6BP
  • Hand: 3" discs - S3HP
  • Hand: 5" discs - N/A
  • Hand: 6" discs - S6HP
  • Considerations:
    • these pads are not suitable for use on a rotary buffer
    • correct size backing plate for each of the three different sizes
    • micro hook & loop synchronization for a strong engagement and minimal heat generation

The chart shown below puts all of the above pairings into an easy to reference format.



We would like to thank Jason Rose for sharing his vast knowledge on this topic, developed over many years of product development here at Meguiar's. Without his help we'd all just be sticking any pad to any old backing plate.

[greg0303]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Absolutely fantastic article, Mike.

Backing plate/ buffing pad combo is so often mismatched. Not any more.

[Marc08EX]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Very informative article Mike!!!! Thank you so much for taking time to post this!

I'm one of those guys who think that a backing plate is just a way to stick a pad to a buffer. I'm glad I found this article!

[Marc08EX]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Mike, quick question.

What if the flat face of the backing plate is not perfectly perpendicular to the threaded bolt that attaches the backing plate to the D/A or rotary (or the BP is not perfectly parallel to the x-axis when it's connected to the buffer), will this cause any damage? When you spin a pad with this problem, the backing plate starts to wobble. I would assume that it would cause problems when using a rotary because of weight balancing (think of an unbalanced centrifuge). But how about when using a wobbling BP on a D/A? Will it destroy either the BP or the D/A down the road? Will it wear out the parts faster than normal?

Thanks!

[davey g-force]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

What an awesome thread - thanks Mike!

I must admit, I didn't know there was so much involved with backing plates.

[umi000]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Fantastic thread, Mike - great information, and very well presented. The shots of the hook material make it easy to see the difference between the two types.

[BillE]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

THANK YOU Mike!

The pictures realllly help to finally understand the different types of hooks.

Bill

[rapport25]

Thanks Mike, for a great write up !!!.

[Michael Stoops]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Thanks guys, but there's no way I could have done this without a very lengthy conversation with Jason Rose - the man is a walking encyclopedia of technical information; it's almost spooky.

Marc, your question about a wobbly backing plate is interesting. On a DA it shouldn't be a big issue due to both the oscillation of the tool and the compression of the pad absorbing some of the energy of the wobble. Unless, of course, the wobble is extreme. From what I've seen of the backing plate you have with this wobble, it's nothing to worry about.

[N_ROC10_DUCE]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

i never really looked at it like that!! thank you for this..

[imz4n]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

This takes all the guess work out, no more excuses on my part. Wonderful thread.

[jarred767]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

I am also one who didn't really even think twice about the backing plates. Now I know so much more of the why behind it. Thanks for the great write-up - even if it was a while back.

[Daniel Kinder]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Thank's Michael for writing a very informative topic! I know I'm only 2 years behind you writing this but this answer's a lot of questions and reason's behind some of the things I've wondered over the years from polishing paint to bare aluminum and seeing, hearing and remembering things in the past about while still using the correct technique with a product and pad one might not get the full benefit or good results as the product should have had. Have a lot of reading and studying to catch up on for not being in the scene for the last couple years, technology, products and paint polishers have advance a lot in their techniques!

Thanks again Michael and Jason for helping and teaching us that the little things play a big role in the outcome of a product!

[P-Shooter]

Re: Backing Plates - More Than Just A Way To Stick A Pad To A Buffer

Any chance to see an updated chart? Sorry, I'm still learning. haha