Hello to you all,
I am going to be doing some brake work in the near future and would like some of your (esteemed) feedback on possible upgrades. The car in question is an 86 300E, and is subjected to street use only, but I'm on it pretty hard sometimes! I have decided, based upon posts in this column, to go with ATE Dot 4 fluid as a replacement. My questions are:

1) What do you folks say about slotted or cross-drilled rotors? Are they effective on the street? How about the noise and durability issues?

2) There are so many so-called performance pads out there I'm turning to you for the skinny. Are there any brands worth investing in for a measurable improvement in braking power?

3)Given that the car is an 86, should I replace the rubber brake line hoses? Are these a regular replacement item? If so, anyone have experience with the braided steel/teflon variety? Can you feel the difference as claimed by most manufacturers or is that really just at the limit?

Forgive the long post, but I'm sure others out there are interested in the value of similar upgrades.

Regards,
Nick

Happy St. Patrick's Day! Have a green beer!

Hello Nick:

I am awaiting anwsers to your questions from the group. I have a 560 SEL that I also planning to renew the brakes this spring.

Hope you get a response soon..

H. O. Tyler
90 560 SEL
85 300 SD
84 240 D

Nick,
I would recommend raiding the corporate parts bin. A 400E brake conversion is something we have looked into before. The only question left unresolved is whether the master cylinder would have to be replaces as the twin-piston front calipers may be a bit more than the stock is up to. You could also try the big brake upgrade offered by Brembo but I don't know how well it would do as far as noise and whatnot. If you stick with MB parts bin raiding then I'd stick with OEM pads. For what you would be doing you would be quite hard pressed to overtax them and the downsides of going to an aftermarket pad would far outweigh the very small (if any) gains you'd get that .5% of the time. I've heard from several reliable sources that the slotted rotors can "groan" a bit under low-speed use. The cross drilled ones can have a bit of a rep for eating pads. (think cheesegrater) As far as brake lines go...as old as your car is I would replace them but you can go OEM just as well as SS lines. You would get the biggest gains from having fresh lines and the OEM's are certainly very high quality.

Hope this helps...Lee

PS if you are seriously interested in looking into doing a conversion for your 300E just fill out a PartsShop inquiry and we'll look into it.

I would be very interested in getting a complete list of what was involved in going to 400E brakes on my 300E, especially as regards the need to replace the brake master cylinder. I finished the Sportline and Euro light project, and am working on the stereo now. The next project will be the brake conversion, timed to coincide with the next brake fluid flush - new ss lines and fluid at a minimum, 400E calipers and rotors possible depending on cost. Specific cost factors are: 1) Do the rear rotors and calipers need replacing to 400E specs, or are they the same for both cars? 2) Is it necessary to change the master cylinder as well? (I believe that a post by RC imports in the past said it worked OK?) and 3) Is the ABS the same for both cars, or does it need upgrading as well.
If the only difference is the front rotor and caliper type, I will probably do the conversion. If the ABS and master cylinder needs modifications, I will probably stick with what I have. Thanks for the input!

------------------
JCE
87 300E, 62k miles
Smoke Silver

Would it be possible for MercedesShop to come up with a price quote for a conversion of some of the popular models, like the w201, w124 and more. I would not mind having an OEM conversion.

------------------
Chirag (Charlie) Patel

99 Mercedes-Benx ML 430 V8 w/custom TV, Video, UHF, speaker system
93 190E 2.6 w/ an amp, equalizer, and CD-changer, integrated w. stock stereo for integrated cellular phone speaker system
2001 C-Class - Maybe

Submit a PartsShop inquiry and we'll start digging. (though allow this may take awhile to get the research done)

Let me know....Lee

I agree with Peter -- SS brake lines and cross-drilled or slotted rotors.

Brian

I would not use drilled rotors. They are prone to stress cracking under severe use. Unless closely monitored this can lead to catastrophic failure. Use gas slotting. It gives same benefit from a performance standpoint and is safer. The stainless lines are a good addition. They will definitely improve pedal feel over aged stock lines and will allow the ABS to cycle faster to better approximate threshold braking.

Thank you all for your replies.

Any brand and source recommendations for the slotted rotors and lines?

Incidentally, I run on Eibachs and Bilstein HD shocks and am happy with their overall effect on vehicle dynamics, including braking.

Also, should these slotted/drilled rotors be paired with performance pads (and which ones)?

Finally, I'm not sure I understand how new lines would change the ABS cycle frequency, although it may improve efficiency.

Thanks again,
Nick

Anytime I read about cross-drilled rotors, there's always a post about stress-cracking/catastrophic failure. Is this just perpetuating a "wive's-tale" or is there truth/proof to these statements? Just curious if anyone has first-hand knowledge of the so-called, "pitfalls" of having cross-drilled rotors. I've heard things like water gets trapped in the holes and boils from the heat, which produces a "steam-layer" between pads and rotor, leading to decreased braking, etc. Also, didn't/don't they come standard on some high performance exotics? If "yes", then I would have to say they're safe and effective. If it were NOT safe, that'd be like putting V-rated tires on a Ferrari -- oops, Ferrari DID do that and got sued for it!

Thanks for any feedback.

Brian

Brian,
I think that, for the large part, the rotor fracture symptom of cross-drilled rotors has been alleviated. A stress fracture needs a stress concentration to be inititiated. With regard to a brake rotor, the potential for a stress concentration lies in 1)a poor quality casting or in 2)the abrupt changes in local cross-sectional areas created by drilling dozens of holes through the disc. Given that most of the high-performance drilled rotors available today are made with high-quality rotors to begin with, that solves problem #1. Additionally, nowadays, the holes are not only drilled but radiused as well, thus creating a longer 'neck' where the x-section change occurs - thus minimizing the stress concentration factor in and around the 'neck', solving problem #2.
Further, I imagine one would need to generate more heat than one is likely to do in street driving to crack even a rotor of mediocre quality, let alone the factory ATE or Brembo drilled rotors.
And yes, many exotics use drilled rotors as stock equipment. As to whether drilled or slotted is more appropriate for street use, the new 911 Turbo has front rotors that are both drilled and slotted!
I think quality, brand-name drilled rotors should be safe - my original question was whether or not they are worth the investment for a street car.
Thanks to all for an interesting discussion thus far...
-Nick

I tried cross drilled rotors on my 500E. If I had not performed a thorough inspection of the brakes between run groups at a track event they would have failed. They had been drilled and champhered. You cannot champher the inner portion of the hole. Factory brakes are cast with the holes and then drilled as a finishing operation. Check out cars at a track event. No one with big fast cars uses drilled rotors. They are beneficial under wet track conditions and are used by ralley cars to improve initial brake response under the really adverse conditions they encounter. They do work on motorcycles to help reduce the gyro effect and aid in turn in. For street use they would probably help initial brake response under wet conditions. Normal street use will not tax the rotor enough to induce failure.

Thanks for relating your first-hand experience, Lou - it's the most valuable kind!
What signs did you look for during inspection that warned of imminent rotor failure?

I noticed that I felt a warped rotor type of vibration. Upon inspection, the pads were almost completely gone after about 12 laps or 48 miles. The previously minor cracks that had radiated out from the holes had met and resulted in a warped section that had cracked about 2/3 way through. One blow with a hammer and it broke a section from the inner rotor surface.

i have a 1989 300E and have done everything under the sun with upgrading my stock brakes.

i find that the best combo is using ss brake lines (techna fit: tel # 310-530-1476), ate power discs (foreign auto parts: tel #(800)728-1601, cost is about $55/ea for the front on a 300e), motul dot 4 brake fluid (i think it is just as good or better than the ate), and porterfield carbon/kevlar brake pads (tel #949-548-4470).

i also had my rotors silver cad plated (for corrosion) + cryogenic (to relieve stress and extend rotor life and pads).

in my opinon, brembo upgrades is really overpriced. (not very cost efficient). and definetely don't use cross drilled rotors, cuz i used them and the rotors wore out before the pads did. the pads heated up and cooled down so quickly that it hardened the pads so much that it tore up all the rotors. get them slotted. similar concept. the integrity of the rotor is alot stronger on a slotted rotor than a drilled rotor.

hope this info helps.