Best dial setup - PeachParts Mercedes-Benz Forum

JHZR2 · #1 05-02-2010, 02:15 PM

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!

Brian Carlton · #2 05-02-2010, 11:06 PM

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.

Diesel911 · #3 05-02-2010, 11:36 PM

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.

#4 05-03-2010, 07:06 AM

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.

JHZR2 · #5 05-03-2010, 08:11 AM

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

bmwpowere36m3 · #6 05-03-2010, 09:14 AM

Quote:

Originally Posted by LarryBible

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.

^ 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...

R Leo · #7 05-03-2010, 09:18 AM

Quote:

Originally Posted by JHZR2

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

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

vstech · #8 05-03-2010, 09:20 AM

Quote:

Originally Posted by bmwpowere36m3

^ 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...

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.

Diesel911 · #9 05-03-2010, 11:11 AM

Quote:

Originally Posted by bmwpowere36m3

^ 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...

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.

JHZR2 · #10 05-03-2010, 04:36 PM

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.

Diesel911 · #11 05-04-2010, 02:31 AM

Quote:

Originally Posted by JHZR2

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?

JHZR2 · #12 05-04-2010, 07:50 AM

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.

#13 05-04-2010, 08:40 AM

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.

vstech · #14 05-04-2010, 08:48 AM

Quote:

Originally Posted by LarryBible

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!

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!