$4.99 Shipping over $49 w/coupon DI499 | 2,350+ Products | 83 Brands | 12,000+ Reviews | 1,550+ Detailing Articles
Close Menu

Ask a Pro Categories

Pro Detailer Authors

Other Authors



Clean ⋅ Shine ⋅ Protect

Ask a Pro Categories

Pro Detailer Authors

Other Authors



Cookies are disabled in your web browser. To shop with Detailed Image, please turn cookies on and then refresh the page.

The “Washer Mod” on Rupes Bigfoot and Griot’s BOSS Polishers


Long throw dual action polishers have become the go-to machines for most professional detailers who offer paint correction services.  These machines yield excellent results in a shorter amount of time, making them the clear choice when time is money.

A unique trait that the Rupes Bigfoot and Griot’s BOSS machines share is that they do not spin freely like other free spindle machines do (ie Porter Cable 7424XP).  This is because these machines were designed with a shroud that contacts the rear of the backing plate which produces friction, and therefore does not allow the backing plate to spin unless the machine is powered on.

ATD | Washer Mod

The idea behind this was explored heavily by Kevin Brown of BuffDaddy.com.  Kevin explains that this shroud was implemented to slow excessive backing plate rotation when the pad is not under load while the machine is running.  So in situations where the pad is not in contact with a polishing surface, or barely in contact with the surface, and the machine is turned on, the ultimate speed of rotation is limited by the friction between the shroud and the backing plate.

This was seen as a potential performance inhibitor, so Kevin went on to develop what is now known simply as “the washer mod”.  The idea behind this simple modification is to eliminate the contact between the shroud and backing plate by inserting a thin washer between the mating faces allowing the backing plate to spin freely and therefore increase the backing plate rotation.  The benefit here is that more backing plate rotation can lead to an increase in cutting speed while also potentially aiding in your polishing results as well.

ATD | Washer Mod

As previously mentioned, a small spacer, or washer, is all you need to complete this modification and unleash even more potential out of your long throw polishers (note: The Griot’s BOSS machines include a washer in the supplied parts bag which users can install on their own).

ATD | Washer Mod

Simply place the washer in between the backing plate and the mounting face on the machine, then reinstall your backing plate.  Note that if you are purchasing a washer from your local hardware store to use in this application, do not choose an excessively thick washer as you still need proper thread engagement to hold the backing plate in place.  If you’re concerned about adding the spacer, you can replace the mounting bolt with a slightly longer one to make up for the additional height of the spacer.

Thanks to Kevin Brown for allowing me to share this information on the Detailed Image Blog. You can find the complete article by Kevin Brown, which discusses the benefits of long throw machines as well as the performance benefits of the washer mod, on the Autopia.org forums.

Zach McGovern
Attention To Detailing Peoria
Peoria, IL

17 comments on The “Washer Mod” on Rupes Bigfoot and Griot’s BOSS Polishers

  1. DC says:

    I tried it modded several times and prefer using the machines stock. Rupes did an amazing job balancing oscillations with rotation to get the maximum in cut, finish, and comfort. A lot of that stems from regulating the rotation. They found that “sweet spot”. With the machine stock I find that I’m usually ranging from speeds 1- 3, where modded I was on 5 -6. The excessive rotation also prematurely dried out my compounds (Zephir/M100) on their blue microfiber pad.

    One bad experience with the anti-spin feature came after thoroughly cleaning the machine. Upon the next use, I was getting black specs of rubber, a burning rubber small, and noticed that the shroud was trying to fold under itself. Eventually the shroud wore itself down, and my plate was free spinning. Since I didn’t care for how the machine operated with the plate free spinning I did some research, and discovered that the shroud needed to be greased (thanks Dylan). So I ordered a new shroud, got a tube of dielectric grease, and the machine works like a charm.

  2. Jai McRae says:

    Do you know if the original 5 inch backing will fit on the 21 mark ll ?

    • Reece @ DI says:

      Jai – The original 5″ backing plate will not fit the Rupes 21 Mark II. The old backing plates will have a product number without an “N” and they only fit the ES Big Foot units. The new backing plates have product numbers that include the “N” and they are compatible with both the ES and Mark II units.

  3. Robert McCarty says:

    I don’t use the washer mod. My 21 and 15 work great without the modification. The Rupes machines were designed to run without the washer and to be vibration free. I trust the Rupes engineers to do their job. Rupes itself does not endorse the washer mod. Griots is totally different. Their tools are manufactured in China. I do not know if Griots tested their machines with and without the washer mod to see if the vibrations were the same.

    • Rupes has stated that this minor modification does not impact the warranty coverage on their tools, so to me, they are not against it and do not see it as a risk to their original design. We have used our machines both ways, and personally prefer the added rotation available with a free spinning assembly. Thanks for your feedback!

    • Morgan says:

      Yeah, but Griot’s has a no bs lifetime warranty. Rupes charges you an arm and a leg and has a one year warranty.

      • Reece @ DI says:

        Morgan – Rupes has a one year warranty against manufacturer defects and a pretty awesome and easy to use flat rate repair program if anything happens after a year. For Griot’s, they do have a lifetime warranty against manufacturer defects and they can help with repairs if needed as well. Both warranties are great in their own way and both companies do make some great polishers overall.

  4. Brae says:

    I like this mod & have been using it for a few years now. With the increase of rotations I find it much easier to work the surface and am more able to remove defects. It’s kind of like stepping closer to using a rotary buffer for that speed cut but with a little less of the worry of burning through as fast. If it’s too fast, turn down the speed. Also with practice & patience it is possible to do a lot corrections without the need to wet sand.

  5. Rick says:

    I did the mod but used a nylon washer instead of a metal one which made fitting it much easier. A few strokes with a file and the sides of the washer and it was ready to insert. I have smooth rotation and no binding.

  6. Nathaniel Hicks says:

    Can the washer mod be used on the Rupes mini?

  7. Cee Rock says:

    I have the Boss 15 I like it without the washer. Sucks that it needs to be lubricated after each use…

  8. When I received my first Rupes in November 2012 I tried it on a few panels without the washer mod. After getting a feel for the tool stock, or as I like to call it, “valet mode” I installed the washer and the difference was immediately noticeable. I have not looked back since and the first thing I do with every new Rupes and BOSS tool that has the shroud is to put the washer in. Not only does it allow you to get full potential of the tool, but most importantly it also allows the backing plate to spin freely, which is a must for blowing out your pads with compressed air.

    If you like running it stock there is nothing wrong with that, but for me it was a no brainer.

    Thanks for the article, Zach! 🙂

  9. I got my Rupes 21 back in 2013, no one in argentina was aware of the washer mode then, now to be honest I don´t use the 21 very often, to correct paint I usually do it with a rotary, thing is in my country there are lots of high end european cars, and those come with hard clearcoats , cars such as Mercedes, Jettas and Alfas come with this kind of rock-hard paint. I finally found some information on the mod by reading an article written by KB, and completed the mod yesterdar, I have to make more tests but I felt the machine´s power flows better, and the awfull friction in the blue side of the backing has stopped, I´m now I´m thinking about writing something on my blog based on this interesting article, so thanks for this Zach and with your permission I´d like to translate this article to spanish, It´ll sure be very usefull to my fellow detailers in latin america

  10. CRR9561 says:

    Has anyone used a rupes 75E 3 inch backing plate on the rupes 12E?

Leave a Reply

Your email address will not be published. Required fields are marked *

Commenting Rules

  • Try to keep your comments as relevant as possible.
  • Don't be abusive: no personal attacks or any other nastiness.
  • Feel free to express your opinion, but do so in an eloquent way.

If you do not respect these rules your comments may be edited or even deleted.

My Offers
Black Friday 2
Big Discounts While Supplies Last - Clearance Items - Shop Now
Limited Time Only - BOGO Buy 1 Get 1 Free - Shop Now
Free Stuff
Close overlay