RiderSite.com - Motorcycle Forums

As my EBC HHs were due for replacement, I was looking for what to go with next. Ever the experimenter, I installed a set of Ferodo CP911* on my bike. In doing so, I noted a disclaimer printed on the package that basically stated that if I had sintered pads on the bike, I should bead blast the rotors before installation or I'd suffer a performance loss. Well, needing brake pads, I went ahead and installed the CPs anyways, and sure enough - My brakes, heretofore more potent than stock, lost a significant portion of their performance, and became worse than stock.

Having been very satisfied with the performance of the Ferodos I had on the bike before the EBCs, I shot an eMail to Ferodo and politely asked why this was so. The reply is quite illuminating:


***********************************
Gentlemen,

I installed a set of CP911* pads on my iron rotors, replacing a set of EBC HHs. I did see the disclaimer stating I will notice decreased braking
performance if I don't bead-blast the rotors to clean them, but went ahead anyways.

Well, you're right: They take more effort and don't stop as well as the sintered pads I had on there... BUT - they seem to be slowly getting
better. So my question is, should I forget about them and switch to sintered pads again, or will they get better over time.

Thanks!

Scott

***

Scott;
When switching from sintered pads (any brand) to the carbon based race pads, it extremely important to do so on properly prepared rotors. It all comes down to deposition layers and material compatibility. FYI: the carbon pads
typically don't perform as well at lower thermal levels as their sintered counterparts.

The following is a copied reply to a similar inquiry regarding the use of sintered pads on iron rotors:

The above was copied and forwarded to us by a Ferodo BrakeTech dealer who thought similarly that confusion indeed exists relative to the questions raised in the letter from Greg Cardenas posted on your site.

As such, we'd like to take a stab at clarifying some basic points on this rather convoluted issue:

There's really two very elemental dynamics in play when it comes to material life expectancy [rotor and pad] at the friction couple: € Friction related abrasion [on the rotor pad track]
€ Thermal stress distortion [i.e.: warping of the rotor and/or backplate] Although this is the simplistic view, I'll focus here since this forms the basis of our recommendations:

1/ MATERIAL ABRASION.
Most sintered metal pads are designed specifically for use on stainless steel rotors which is typically a harder material in general than cast iron. As such, some of these friction materials do indeed gall the rubbing surfaces to
varying degrees. If this occurs on stainless, the softer cast iron will normally suffer to a greater extent. Since there are so many different
sintered materials out in the market (with the vast majority specific to stainless steel) we must as a general rule of thumb recommend to our customers that they not use them on their iron rotors as the potential for premature problems is real and potentially expensive.

2/ THERMAL DYNAMICS.
Regarding sintered pads on Ductile iron, Gray iron, carbon steel or stainless for that matter; using the base assumption that the friction material isn't overly abrasive [causing galling, scoring, etc.], the real issue is thermal capacity. All conventional metals used in rotors have their own thermal dynamics to deal
with; total mass, shape, lightening/venting hole type (placement and quantity) combined with inherent thermal conductivity of the resident material all play an integral role in material stability at peak operating temperatures. What we're essentially talking about here is resistance to distortion [warping, coning, etc.].

This is a complicated and convoluted subject that has few simple answers as there are so many variables to factor in. But one basic truth is that the sintered pads, including our new SinterGrip series, run hotter at the interface than do "most" organic pads...by as much as 150 degrees [F] in our testing. If you're running near the edge of thermal capacity with a particular rotor type and design and high performance / racing organic pads (like the carbon based CP911Star), switching to a racing sintered pad will surely exacerbate the problem. In majority of instances where a problem occurs, thermal stress induced distortion is the culprit.

Another area of potential confusion is the many and significant differences between the classes of iron; the two main categories being primarily the Ductile irons and Grays irons. There simply isn't sufficient room here to expand on those differences here without taking up excessive room...have to leave that for another time.

We manufacture our BrakeTech Superlite rotors from computer controlled Continuous Cast [billet] ductile iron supplied by America's oldest and most experienced foundry specializing in advanced composition cast iron. Cutting from billet is clearly a more expensive process than many others but we do this to have greater control over material matrix, eliminate porosity and have the most consistent micro structure possible. Does all this extra care and material selection guarantee they won't warp? Nope. There's very few guarantee's in this world (outside of death and taxes) and in the rarified atmosphere of racing, even less...we just build our SuperLites to be better than most.

In final answer to Greg's question regarding our recommendation of the Ferodo SinterGrip ST pads on the Superlite rotors; we've dyno tested them extensively and have discovered no significant abrasion related problems with this combination. After over 200 dyno runs, they didn't distort either. But bottom line when it comes to thermal stress distortion; as noted above, there's no guarantee this won't happen under the right circumstances.

Hope this provides some insight.

--
Jeff Gehrs
Ferodo BrakeTech USA
909-471-3476

http://ferodobraketech.com
*****************************

After reading this reply a couple times, I decided that:

1) If you are running iron rotors, don't use Sintered pads, as the wear rates are significantly higher.

2) If you've already installed Sintered pads, you should stay with them because re-prepping the rotors is a PITA.

3) Sintered pads leave deposits on your rotors which won't allow Carbon based pads to preform to their potential.

4) Carbon pads do work well, and run cooler than equivalent Sintered offerings. Side benefit for iron rotor users - Their low metal content shouldn't allow the pads to rust to the rotor's surface.

I believe this explains why the Carbonne Lorraine pads did not work up to many people's expectations.

Since I never got a clear answer regarding whether the Carbon pads I now have will eventually wear through the surface and then perform up to standard, I have ordered a set of sintered pads. I do plan on running the CP911s for a while yet to see if they do come back up. If so, I'm sure I can find a worthy recipient of the sintered pads. If not, I have fresh pads standing by.

Scott

By Befbever on Tuesday, May 21, 2002 - 11:28 am:



How's about you bead-blast the rotors and put the CP's on? Worth a try?
Very illuminating btw, Scott.

By Scotteq on Tuesday, May 21, 2002 - 11:55 am:




--------------------------------------------------------------------------------
Quote:
How's about you bead-blast the rotors and put the CP's on?


--------------------------------------------------------------------------------



Bef - I simply don't have a bead-blaster in my toolbox. I'll ride them for a while and see. It'll be a few days before the new pads arrive, anyways. I'll see if they get any better.

Scott
By Befbever on Tuesday, May 21, 2002 - 12:00 pm:



Oops. Sorry, I was hoping you'd be our guinea pig.

By Crmc33 on Tuesday, May 21, 2002 - 12:17 pm:


I suppose it might be a silly idea but I wonder if a good scrub of the rotors with a strong solvent and scotchbrite before fitting the carbon pads would help?
just a thort, might be worth a go one day.

By Yellowstreak on Tuesday, May 21, 2002 - 12:37 pm:


My limited experience of bead blasting steam turbines is that it is done for consistent surface tension, and to work harden the surface to some extent. We have also used it to swell undersize shrink fit diameters back into tolerance.
It also looks nice and uniform, asthetically pleasing to the customer and I am sure they charge dearly for it..
Why they do it on brake rotors is probably for similar reasons. May need the increased surface hardness to break in the pads. I be guessing!!

Dave

By Oldgit on Tuesday, May 21, 2002 - 12:50 pm:


Wet + dry, Halfords, BQ etc