Author Topic: Front brake disc's for W109  (Read 1106 times)

s class

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Front brake disc's for W109
« on: 27 June 2021, 01:01 AM »
Hi guys I'm appealing here for any possible experience.  I'm working on a w109 3.5, and the front brake rotors have reached minimum thickness.  Options are to leave it, or replace with genuine Mercedes rotors, or replace with the FEBI rotors available online.

These are the thicker vented rotors the same as the 6.3 uses, not the freely available solid ones that most 108s use.

The FEBI rotors are about a quarter of the price of the Mercedes ones which would cost a fortune here in South Africa.

Any comments/experience/advice on the FEBI VS genuine question.

Please any help would be appreciated.

Thanks, Ryan

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

ptashek

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Re: Front brake disc's for W109
« Reply #1 on: 27 June 2021, 01:48 AM »
Febi, at least in Europe, offer a 3 year warranty on all rotors. I doubt they'd do that if the product was junk.
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UTn_boy

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Re: Front brake disc's for W109
« Reply #2 on: 28 June 2021, 03:40 AM »
The W109 3.5 never had the non vented rotors.  Also, the non vented rotors are not a W108 thing.  All W108 and non 6.3 W109 cars had solid, non vented rotors up to a certain point....something like mid to late 1969......possibly earlier. After that point, all W108 and W109 cars had vented rotors. The later models has their own VIN breaks as to when the switch happened.  However, the W109 3.5 came along after that switch had been made across the whole product line.  If the car you're working on has solid rotors, then someone in the past cheaped out and put solid rotors on. 

As far as the quality of the FEBI rotors I cannot comment on.  I've never bought aftermarket rotors.  But, as Lucas pointed out, if they're offering a 3 year warranty then I can't imagine they'd be too bad.  They may eat through pads quicker (assuming you're putting Mercedes pads on).  The future longevity of the FEBI rotors is yet to be determined, so I guess it comes down to whether or not you/the customer want genuine rotors or not.  Maybe buy the FEBI rotors to get you buy while money is being saved up for genuine rotors?  Just a thought. :) 
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s class

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Re: Front brake disc's for W109
« Reply #3 on: 28 June 2021, 10:52 PM »
THanks Aaron, and Lucas,

I probably wasnt clear  - typed the previous message from my phone.  This car does presently have the correct vented rotors. 

To give some idea of price, the genuine Mercedes rotors land here at about $500 each, whilst the Febi ones would be about $145 each after taking ino consideration shipping, taxes etc to get them from overseas.

One other issue that raises its head, is I was years ago led to believe that genuine MB rotors were heat treated, whilst aftermarket might often not be.  There is a brake specialist here that offers a heat treatment service for brake rotors - they typically serve the racing community.

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

rumb

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Re: Front brake disc's for W109
« Reply #4 on: 29 June 2021, 06:49 AM »
What is the minimum thickness? I have a used set lying around ad would like to know if they are any good.
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UTn_boy

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Re: Front brake disc's for W109
« Reply #5 on: 30 June 2021, 02:31 AM »
The new thickness of vented rotors is 19mm. 
The refinishing limit is 18mm.
The war limit is 17.80mm

So we only have 2.2mm of allowable wear.....that seems like very little. 

Ryan, The rotors from Mercedes are, or used to be, forged in house and heat treated.  I know they're still heat treated, but I don't know if they're still made in house.  The part number, 109-420-00-05, now has a "64" at the end of it....which usually means the part is sourced and/or made elsewhere.  So your guess is as good as mine. 

By the time you have the FEBI ones heat treated where will you be on price?  I imagine that may be a factor, too. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

s class

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Re: Front brake disc's for W109
« Reply #6 on: 02 July 2021, 12:14 AM »
Hi Aaron,

Thanks for that help and information.  I was under the impression from my workshop manual that 18mm was the min allowed, but I think thats the limit for machining as you say.  I have seen a new disc, and it's stamped "min thick 17.8".

The discs have been refinished apparently not too many miles ago, and measure up at 18.1 to 18.2mm.  No visible ridges or lips.  Its tough to say if inner and outer surfaces have lost equal material though.  Given that this car is not going to do much mileage, an option may be just to leave them be as theres 0.3mm left - I guess that would be customers choice. 

Any comments?

BTW heat treatment would be ~ $75 for a pair.

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

ptashek

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Re: Front brake disc's for W109
« Reply #7 on: 02 July 2021, 12:46 AM »
You haven't said what mileage or year the car is, but assuming it's last of off the line, so 1973, my super unscientific calculations suggest that at current mileage:

1.8mm of wear in 48 years => 0.3mm left / (0.0375mm wear / year) => 8 years of life left.

Say five to account for the unexpected.
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UTn_boy

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Re: Front brake disc's for W109
« Reply #8 on: 02 July 2021, 06:38 PM »
Well, Lucas brings up valid point(s), but we also don't know if the rotors have ever been replaced in the past.  So true mileage is definitely a factor.  However, my view is that if there is .3mm left, the owner rarely drives it, and there is no warpage, then leave them on the car until they really need replaced.  In the 5-8 years that Lucas has accounted for regarding the time left, that'll give you and/or the customer plenty of time to buy the good rotors from Mercedes.  And you'd better do that sooner rather than later.  Just like with the early or late W116 rotors (I can't remember which) they will likely become no longer available very soon....with no plans of ever offering them again.  If they do offer them again they'll be double the price they are now.  Just be sure to use genuine Mercedes pads to get maximum life out of the rotors.  The Mercedes pads are very soft and easy on the rotors......and they're cheap!  :)
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex