5" backing plate on the lhr21 mark 2

[Xplosive Detail]

Hey guys can you still put a 5" backing plate on the lhr21 mark 2? I want to try this out since I have a mark 1 15 and a mark 2 21. But the set screw plate is smaller on the mark 1 15. It's not just plug and play like I've read many times? Do I need to purchase a new mark 2 15 plate to fit the on the mark 2 21??

Thanks.

[Marc08EX]

Your 15Mk1 BP with the smaller mounting hole was their very early run of the Mk1 tools. Later Mk1 tools have an enlarged BP mounting hole, which is the same as the current Mk2 BPs.

The current Mk2 BPs are backwards compatible with the Mk1s, even the ones with the smaller BP mounting hole/spindle. But not the other way around.

So in your situation, you need to purchase a new 15Mk2 BP to fit your 21Mk2.

[Zubair]

The above response is correct but I find my 15 bp on my 21 MKII to have considerably more vibration and eats pads. I'm sticking to the larger bp on my 21 as it feels right.

[Eldorado2k]

The above response is correct but I find my 15 bp on my 21 MKII to have considerably more vibration and eats pads. I'm sticking to the larger bp on my 21 as it feels right.

What kind of pads has it eaten?

[Mike@ShineStruck]

Have you tried the 5in BP with the thin pros?

[Eldorado2k]

What kind of pads has it destroyed?

[Zubair]

What kind of pads has it destroyed?

The OEM Rupes 6" Blue and Green pads. The same pads had far less wear on my 15 after a couple of cars then just a panel on the 21 with 5" bp. The 21 with the intended 6" bp doesn't abuse pads though and is really smooth. I'm too afraid to mess something up as it vibrates and doesn't sound right with the 15 bp on the 21. Gimme a couple of minutes so I can do the free air vibration test with the 5" bp and 5.5 " ThinPro pads as requested and report back.

[Zubair]

Have you tried the 5in BP with the thin pros?

Okay just tested the 5" bp with a variety of 5.5" pads, GG Boss, LC ThinPro, BnS Urotec and Low-Pro. All those pads do fine on my 15 they donot run smooth and the polisher runs erratic with them on the 5" bp accompanied to a rattling sound. Slap on the 6" bp and intended pads and shes smooth again. While the vibration is not as bad as a PC or 3401 it is significantly more and very noticeable over using the intended 6" bp.

Something else I tried using the 6" bp with and without washer mod. With the bp marked, without the washer mod, run it on any speed from 1-6 free air and you will notice the rotation but can easily see the marking at any speed from 1-6. Now add the washer and repeat the test. From speeds 1-6 you cannot find the marking anywhere thats how insane the rotation is with a washer on a 21 MKII. My 15 MKI never displayed this huge of a difference by adding a washer as the 21 MKII displays.

[Eldorado2k]

Does it run smoother with a pad on a panel without the washer mod vs. with washer mod? I found that made a difference with my G21. Just a thought.

[custmsprty]

Dylan from Rupes posted an answer to this swapping plate sizes on the mk II's a week or so back.

[Zubair]

Does it run smoother with a pad on a panel without the washer mod vs. with washer mod? I found that made a difference with my G21. Just a thought.

If we talking smoothness the 6" bp is considerably smoother and quieter with the 6" and you can see, hear and feel the machine is designed around the weight of the larger 6" bp.

The washer makes absolutely no difference to the smoothness both on and off the paint what so ever but it sure as heck increases rotation considerably. It goes into hyper mode with the washer on.

[custmsprty]

If we talking smoothness the 6" bp is considerably smoother and quieter with the 6" and you can see, hear and feel the machine is designed around the weight of the larger 6" bp.

The washer makes absolutely no difference to the smoothness both on and off the paint what so ever but it sure as heck increases rotation considerably. It goes into hyper mode with the washer on.

I wonder how much added stress with a washer mod running on it long term would put on the motor.

[Todd@RUPES]

I wonder how much added stress with a washer mod running on it long term would put on the motor.

Zero.

[Marc08EX]

Zero.

Thanks for that info Todd!

[7.3powerstroke]

Thanks for that info Todd!

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