Hello all,

Well, I'm looking at doing some brake work on my 1974 240D. I have to drive down to the nearest air force base (auto hobby shop) to get any serious work done due to living in an apartment. It mainly needs a flush, but I was planning on replacing pads, hoses and rotors mainly for peace of mind. The pads and rotors are really ok (pads about ~3/4 worn), but once spring rolls around I won't have time to fix much (school).

So I've read through the manual and replacing the front rotors seems like quite the job, with removing the hub and all that. While the rotors are technically okay (no warping, thickness checks out) they are original.

So my question is, should I even worry about them? And if so, does the manual just make it look harder than it is (theres a couple of special tools that I have no inclination to get). And being that I'm going a bit of distance to do this work, and seeing how the McParts might not have little bits that I might need, what should I get ahead of time? I was considering just replacing the wheel bearings while I was in there.

Any good tips for the job, and should I replace anything else brake related, just for prevention (master cylinder, etc...)? BTW, there are 116kmi on the car.

Thanks,
Ben

There are two measurements that will tell you whether you need to change your rotors. One is the thickness. This tells you the amount of wear left in the rotor. It is measured with a micrometer. The repair manual will tell you the minimum thickness that is allowable. This will also tell you whether you can have the rotor machined if it has some wear groves in it.

The other is the 'run out' of the rotor. This is measured with a dial indicator and a magnetic base. Buy the set through Harbor Freight for not very much. This tells you whether your rotor has a wobble in it, i.e., not running vertical to the spindle center line. If you have a wobble you will often get a fluttering brake peddal. Rotors that wobble are either bent or have been over heated. In either case they are not really worth messing with. Get new ones.

If you car has less that 250k miles on it and you can't feel any grinding or roughness when you spin the rotor then don't worry about the wheel bearings. Make sure that there is no side play in the hub assembly by snugging up (do not over tighten) the wheel bearing nut.

To test for loose wheel bearings screw the lug nuts back into the wheel hub and snug them up. Grab the rotor at 12 and 6 o'clock. Rock it back and forth gently and see if you get any play. If you get play tighten the wheel bearing nut.

Also test the steering components for wear by rocking the rotor side to side. Watch the tie rods, etc. to see if there is any movent in the various ball joints. This will tell you if they are wearing. Might not hurt to replace your steering dampener at this time. It is only $35 or so.

with the above post. changing the hoses is not a bad idea, but they do last a very long time. i usually dont change them unless they start seeping. changing the pads is dead simple.

if you have excess energy and want to do something that will make a noticable difference, find a set of calipers from the later 123 and bolt them on. you will have a lot more braking power and great pedal feel too. change the hoses at the same time if you do this. the slightly different position that they bolt onto the calipers will cause them to leak in a month or two. i did this on my 74 and was very happy with the results. i think i had a sticky caliper on the 74 and had extra 123 calipers on hand though so it was pretty cheap to do.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Hmm, I think I might be able to snag some 123 calipers for not too much. I'm assuming that I purchase 123 brake hoses? Or are they the same?