Use Flex-Hone To Prepare Old Rotors For New Pads?

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Background: On bench lathes, it is normal practice to use a flex-hone to give a freshly resurfaced rotor the non-directional finish that is necessary to reduce noise and to reduce break-in time.

Issue: When an individual installs new brake pads onto serviceable rotors (old rotors that meet guidelines for thickness variation, rotor thickness and rotor runout), the old rotors have a slight amount of glaze and material leftover from the previous set of pads. I have found that the technique of "pad slapping," despite OEMs saying that it is okay, often results in a very lengthy break-in period. In other words, it usually takes a long time before the new pads fully seat and braking performance is restored.

I found a post from a motorcycle forum where an individual used the flex-hone to prepare his old rotors for new pads. It appears that the flex-hone did an excellent job of removing the glaze from the old rotors, as well as removing most of the old friction material that was embedded onto the rotor's surface:

http://forums.pelicanparts.com/5943167-post9.html

Link to product: http://www.thetoolwarehouse.net/p-18655-brush-research-mfg-rmfh120z25.aspx

Has anyone tried this practice before? It is quite intriguing and I think it may be a good step to add to a "pad-slap."
 
IME the length of time for a pad slap to break in is directly related to the pad materials. Soft organics take forever where a hard semi metallic may cut right through the garbage and result in a beautiful rotor in just a few hundred miles or one bedding.

I am wary of removing any material by hand as it could introduce a surface variation, but I doubt this process removes much at all.
 
Been doing this for a couple of years, haven't had any problems at all. I found the 1/3 hp motor was a bit underpowered actually, replaced it with a 1/2 hp version that runs a bit slower rpm's as well. Works pretty good
smile.gif

http://www.bobistheoilguy.com/forums/ubb...254#Post1967254

Note - this is not a fix for warped rotors or rotors with obvious surface issues, like gouges. I just use it to freshen up the surfaces of rotors in good shape at pad change time.
 
Looks to like it would work fine. In the GM service dept I ran in the early 90s GM had a TSB out about SWIRLING the rotors new and just cut. Techs used a scotch brite pad on their air drills. If this procedure was not done GM cars would not STOP worth a toot for 100s of miles!
 
Originally Posted By: Mud
Been doing this for a couple of years, haven't had any problems at all. I found the 1/3 hp motor was a bit underpowered actually, replaced it with a 1/2 hp version that runs a bit slower rpm's as well. Works pretty good
smile.gif

http://www.bobistheoilguy.com/forums/ubb...254#Post1967254

Note - this is not a fix for warped rotors or rotors with obvious surface issues, like gouges. I just use it to freshen up the surfaces of rotors in good shape at pad change time.


Thanks! I faintly remember a thread like that, but I was unable to find it.

In the absence of a suitable rotor "turning" device, do you think it would still work if I applied the flex-hone while turning the rotor by hand?
 
120 grit flap disc on a 4" angle grinder to both sides. Each rotor done in less than 60 seconds.

It also works good for the hat surfaces, too.
 
I used this kit on my old Accord. I used it once on the original rotors when they developed runout (pedal pulsated) and once on new Beck Arnley rotors that did the same thing within 10,000 miles. It is cheap and relatively easy to use. You end up with concentric grooves cut into the rotors. It freaks out tire people when they see it, but the guy who designed the product is a Detroit automotive engineer. I spoke with him the first time I used the kit eight years ago.

With my BA rotors, I even took them to a shop to have them machine surfaced. The problem returned in a few months. I did that because the Brake-Tru kit has gotten to be very hard to find. It's probably due to the nature of the process which seems very scary upon initial review. I can't recommend this product highly enough.

http://www.autosupplyco.com/content.wws?fname=braketru.html
 
Originally Posted By: The Critic


In the absence of a suitable rotor "turning" device, do you think it would still work if I applied the flex-hone while turning the rotor by hand?


I suppose it would be ok, but the finish may not be very consistent. One benefit of the motor drive was that all I needed to do was hold the drill while the motor turned the rotor at a steady rate to get a more even finish
smile.gif
IMO I don't think that you can hurt anything either way.
 
Originally Posted By: SteveSRT8
IME the length of time for a pad slap to break in is directly related to the pad materials. Soft organics take forever where a hard semi metallic may cut right through the garbage and result in a beautiful rotor in just a few hundred miles or one bedding.

I am wary of removing any material by hand as it could introduce a surface variation, but I doubt this process removes much at all.


I agree. Unless the rotor was spinning at an even speed and rigidly on a lathe, or just light even sanding with 120-150 grit sand paper would be fine. Pads will generally wear in to slight rotor imperfections in a matter of time.
 
Originally Posted By: hounddog
Techs used a scotch brite pad on their air drills.
that's what they did at our Service Dept too. Caddy dealership.
 
Originally Posted By: SteveSRT8
IME the length of time for a pad slap to break in is directly related to the pad materials. Soft organics take forever where a hard semi metallic may cut right through the garbage and result in a beautiful rotor in just a few hundred miles or one bedding.

I am wary of removing any material by hand as it could introduce a surface variation, but I doubt this process removes much at all.


I don't think it removes any metal from the rotor itself, but it certainly appears to remove any glazing and correct minor surface imperfections better than sandpaper. Just take a look at these before/after pictures that were in the thread:

Before:

Brake+maitenance+00313018735441301949112.jpg


After:

Brake+maintenance+0131301949144.jpg


Brake+maintenance+0141301949168.jpg
 
Originally Posted By: andyd
I use a knotted wire wheel in a grinder
I have one of those too and wondered WTH I would ever use it for again. Now I know, thanks!
 
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