Best dial setup
 

I'm planning on doing a conversion on my 300cd to early w126 vented rotors in the spring/summer. I'll replace everything in doing this, and obviously will need to set wheel bearings..

I've searched around and saw mention to hf parts. What is the best way to go? As a diy, spending a bit more on a part that will be more exact or easier to use is a good thing given the savings encountered.

So, recommendations of what is currently best?

Thanks!

You really don't need "the best" for this task. Any dial indicator with a magnetic base that can extend out to the tip of the spindle will be satisfactory.

The spec is .0005", but, in reality, anything between .0005" and .0015" will work just fine.

I already had a thousands of an inch Dial Indicator. What I did was opt to spend the extra Money and get a Metric Dial Indicator.
It cost about $10-$15 (meaning in the $27-$35 range + shipping if you order it) more to get one (I have not seen Metric Indicators for sale at Harbor Freight) but it does away with having to calculate or gestimate the measurement.
Mail Order machinist supply places like Enco and VME sell them.

Mainly having the metric one it is a convenience.

About 3 weeks ago I did buy a new Magnetic Base form Harbor Freight and it is better made than the made in Taiwan one I have used since the 1980s; The Harbor Freight one is much sturdier. It was on sale at that time at about $10.

There's really no need to use a dial indicator for this job. With freshly packed bearings, simply snug it down tight to force out the grease, then back it off such that there is still slight torque felt on the nut, then lock it down.

There's no need or advantage to vented rotors other than looks, unless you are using some racing pads that require gas venting.

Given that I haven't done it before, I'd rather do it right. I don't have a feel for it.

And I am inclined to add the additional thermal capacity of the heavier front rotors which will help act as a greater sync of converted momentum, since I'll be looking to put rebuilt calipers on anyway. Nobody sees the rotors, it really isn't a look thing on a w123, but a peace of mind and additional heat holding capability is provided, which is beneficial, IMO

^ That's not accurate, standard vented rotors have nothing to do with brake pad gas venting. Vented rotors don't increase thermal capacity, unless they contain more mass, however they will cool down quicker between stops.

Cross-drilled or slotted rotors on the other hand do "vent" brake pad gasses, but even that is overrated. The best benefit of either of those types of rotors is that they constantly "refresh" the brake pad surface by skimming off its top layer. However they come at a higher price and typically much shorter life...

Gawd, it's a diesel W123. How fast do you think it can go?

awww, Larry, I know you knew that!
the 126 vented rotors are much better for long stopping, and extended use. like said above, it's the crossdrilled, or slotted rotors that are a looks kinda thing.
them vents, help give you longer stopping before the fluid boils in the calipers! no improvement in stopping force though.

Vented Rotors should at least have more surface area and that should dissipate heat better.

Also there is some Air circulation through them due to centrifugal force.

I have seen Water Pump Impellers with the same design as the Vented Rotors so I assume Air would be moved by the same method through the vents.

My thought is more thermal mass for situations where there is continued sustained braking. Without more swept area, the benefit is more thermal mass, which I see as a benefit given the way most folks drive.

I do not know how and test could be done to make a comparison between the two that could be done buy a regular Car owner.

Did Mercedes have anything to say concerning the difference in any of their literature?

Just that they use the vented rotors in their w126 cars to help performance given the higher mass of the vehicle.

Higher thermal mass with lower overall mas means better capability to accept heat, and hopefully then higher sustained performance without needing to resort to aggressive pads.

Unfortunately man folks cannot drive on a highway without stepping on their brakes constantly. Anything that gives an advantage is of use.

I know what you're talking about now. You mean the vents between the inside and outside rotor surfaces, not the cross drilled or slots.

I'm trying to understand the need for brake improvement for any Mercedes since they started using four wheel disks. Barring an all out racing situation, there's plenty of brakes on these cars.

I've hauled my 300E down from 140 MPH before in amazingly quick, controllable style. I don't think any of my diesel MB's went fast enough to ever need much more than dragging a boot on the ground outside the door.

OUCH larry! you must have one heckofa big boot!:eek:
the vented rotors don't give ANY additional stopping power, but they do allow longer sustained braking. anybody that's towing, or climbing large hills can benefit from vented rotors, but don't expect ANY shorter stopping times, or ANY improvement at all under normal or even spirited braking!

You can expect mildly better stopping from the second gen. I really want to find a set of the 4pot r108 calipers for cheap.

110mph and then some.

Come to think of it, I guess a 5 cyl turbo might go that fast with a little patience.

I was late catching a plane one time and must have been downhill with a tail wind in my 84 Euro 240D 4 speed. I saw 100MPH on the speedometer.

In my experience, that seems to be more of a problem with "woman folks" than "man folks."

My 5 cylinder euro non turbo would do 110. At 90mph I currently have plenty of pull to pass that mark now, I am waiting for an open day at Road Atlanta to see what it can really do.

Yeah,X2 on that. But riding the brakes going up hill is what puzzles me.
maybe they think it is a foot rest ?

We do have a lot of hills here in calif., say compared to kansas where it is flat. going over the Sierra to Nevada there can be some steep down grades where a slight drag on the brakes to maintain speed, even when running in a lower gear can generate extra heat.

I usually try not to use my brakes any more than I have to. the people that race red light to red light, can sure generate some heat. Hey Dude! slow down, roll into the light, time your self, then when it turns green just down shift and keep going.

Charlie

This happens when people use their left foot to brake.

^^^^^^^^^^^^^^^^^^^^^^^^^ Great point!

That is one of the hundred reasons that I taught my kids to drive a stick shift. You don't develop that nasty habit.

I learned to drive on a 55 Chevy Step Side PU 6 cyl 3 on the tree. was taught to keep my foot off the clutch peddle unless I was going to use it. it wasn`t a foot rest either.
Also kind of hard to brake with your left foot and shift at the same time.

The dimmer switch was on the floor on the left side, and the starter was to the right of the gas peddle. And Disc brakes, what were those? we were stuck with drums.

Now 49 yrs later Iam stressed out if my W123 doesn`t have the Gen II W126 vented brakes :rolleyes:

Charlie

There is that, and there are also the idiots who every thirty seconds or so have to hit their brakes to adjust speed. What happened to letting off the throttle?

Think is when youre in a lot of traffic, trying to get somewhere fast, and then are doing this over and over because the traffic cluster keeps going up and down in speed.

More thermal mass means lower brake temperatures, better overall retained capacity, lower heat loading on the bearings, etc.

There is a reason why even buying a cheap car today we see vented rotors on the front axle (at least). If they could save a few bucks and a few pounds of unsprung weight, dont you think hyundai and the rest would be doing so on the small cars?