w124 single diaphram vs dual diaphram brake booster

[yao500e]

Question fellow benz friends,

Single vs Dual brake booster.

Does dual booster just make the brake pedal far "more sensitive" or does it increase braking power, and shorter braking distances?

My guess is the former.

Any feedback would be appreciated. thank you.

 

[nocfn]

purely audible response.... will it quiet the cabin experience while braking.....

 

[yao500e]

purely audible response.... will it quiet the cabin experience while braking.....

got it. so as I suspected, it doesnt make the car brake any better?

 

[gsxr]

There are different boosters for 1990's vintage MB's, both single and dual chamber. The dual-chamber provide additional pedal assist ("boost") vs single. There are various levels of boost. See chart at PDF page #6 at this link, the "boost factor" shows the relative difference.

Boost factor only affects pedal effort, which is NOT the same as braking power. Too much assist means the pedal is very sensitive / touchy, which is annoying. Too little assist and the pedal requires a lot of force / leg muscle to get the stopping power you want. To get more braking power (reduced stopping distances) you need larger brake rotors/calipers, and/or different pad compound, and/or stickier tires.

Click the link below for my journey down the booster swap road from almost 15 years ago. Read the whole thread, it starts out all sunshine and lollipops, but storm clouds appear in post #2:

TLDR: Pedal feel is highly subjective, and what one person thinks is great, another may not like at all. Pad compound can seriously affect pedal feel as well. Bigger is not always better, as I learned the hard way; I had to "downgrade" to a different setup after my big MC+booster turned out to be un-modulateable (hmmm, is that even a word?) during trail braking.

W124 brake booster & master cylinder upgrade - MBWorld.org Forums

E-Class (W124) - W124 brake booster & master cylinder upgrade - Hi everyone, As you may (or may not) recall, I installed early 500E brakes on my 1987 300D earlier this year (300mm front (http://www.w124performance.com/images/W124_brakes/300mm_front2.jpg), 278mm rear...

mbworld.org

 

[yao500e]

There are different boosters for 1990's vintage MB's, both single and dual chamber. The dual-chamber provide additional pedal assist ("boost") vs single. There are various levels of boost. See chart at PDF page #6 at this link, the "boost factor" shows the relative difference.

Boost factor only affects pedal effort, which is NOT the same as braking power. Too much assist means the pedal is very sensitive / touchy, which is annoying. Too little assist and the pedal requires a lot of force / leg muscle to get the stopping power you want. To get more braking power (reduced stopping distances) you need larger brake rotors/calipers, and/or different pad compound, and/or stickier tires.

Click the link below for my journey down the booster swap road from almost 15 years ago. Read the whole thread, it starts out all sunshine and lollipops, but storm clouds appear in post #2:

TLDR: Pedal feel is highly subjective, and what one person thinks is great, another may not like at all. Pad compound can seriously affect pedal feel as well. Bigger is not always better, as I learned the hard way; I had to "downgrade" to a different setup after my big MC+booster turned out to be un-modulateable (hmmm, is that even a word?) during trail braking.

W124 brake booster & master cylinder upgrade - MBWorld.org Forums

E-Class (W124) - W124 brake booster & master cylinder upgrade - Hi everyone, As you may (or may not) recall, I installed early 500E brakes on my 1987 300D earlier this year (300mm front (http://www.w124performance.com/images/W124_brakes/300mm_front2.jpg), 278mm rear...

mbworld.org

Thanks @gsxr
really appreciate the information. That is exactly what i have concluded. However there are write ups that state dual diaphram boosters provide more brake fluid pressure to disc brakes. especially big brake upgrades.

An article such as this:

Best Brake Boosters for Better Braking

Power brake boosters offer lower pedal effort and better braking characteristics, but which one is right for your hot rod, muscle car, or truck? We take the guesswork out of that question with our latest buyer's guide.

www.speedwaymotors.com

 

[gsxr]

Thanks @gsxr
really appreciate the information. That is exactly what i have concluded. However there are write ups that state dual diaphram boosters provide more brake fluid pressure to disc brakes. especially big brake upgrades.

More pressure isn't always a good thing. As noted in my previous post, too much pressure (for a given amount of pedal effort) results in a super-touchy pedal that is basically unusable for normal driving. You only want/need a larger booster, with more assist, if you find it requires too much pedal pressure for the desired braking power. If it feels like there's no power assist, yeah, you may need a bigger booster.

An article such as this:

Copy/paste from that article:

"Single diaphragm brake boosters are commonly used for four-wheel drum or front disc/rear drum brake system configurations. Since drum brakes require a lower fluid pressure to actuate, the single diaphragm provides enough assistance. When upgrading to four-wheel disc brakes a dual diaphragm brake booster is recommended due to the higher fluid pressures required to move the multiple disc brake caliper pistons found at all four corners of the vehicle."​

​

All modern MB's have 4-wheel discs and few of those have a single-diaphragm booster.

 

[yao500e]

There are different boosters for 1990's vintage MB's, both single and dual chamber. The dual-chamber provide additional pedal assist ("boost") vs single. There are various levels of boost. See chart at PDF page #6 at this link, the "boost factor" shows the relative difference.

Boost factor only affects pedal effort, which is NOT the same as braking power. Too much assist means the pedal is very sensitive / touchy, which is annoying. Too little assist and the pedal requires a lot of force / leg muscle to get the stopping power you want. To get more braking power (reduced stopping distances) you need larger brake rotors/calipers, and/or different pad compound, and/or stickier tires.

Click the link below for my journey down the booster swap road from almost 15 years ago. Read the whole thread, it starts out all sunshine and lollipops, but storm clouds appear in post #2:

TLDR: Pedal feel is highly subjective, and what one person thinks is great, another may not like at all. Pad compound can seriously affect pedal feel as well. Bigger is not always better, as I learned the hard way; I had to "downgrade" to a different setup after my big MC+booster turned out to be un-modulateable (hmmm, is that even a word?) during trail braking.

W124 brake booster & master cylinder upgrade - MBWorld.org Forums

E-Class (W124) - W124 brake booster & master cylinder upgrade - Hi everyone, As you may (or may not) recall, I installed early 500E brakes on my 1987 300D earlier this year (300mm front (http://www.w124performance.com/images/W124_brakes/300mm_front2.jpg), 278mm rear...

mbworld.org

read the post and write up on mbworld. very informative. thank you. @gsxr

 

[nocfn]

Did we ever get a definitive fix for the noisy brake mechanics.... Thanksgiving wishes to all by the way....

 

[yao500e]

Update, i installed an SL500 dual diaphram and bigger Brembo F40 front brakes on my '95 C36. 13.1 inch (vs 12.6 inch stock)

Car is more sensitive to braking which is GOOD and it seems to stop a little better in stop in go traffic.

 

[gsxr]

what year SL500? There were different boosters used on different years.

 

[yao500e]

what year SL500? There were different boosters used on different years.

Thats a good question. let me get the model number and report back. its also cool to even see a dual diaphragm booster in a C36 lol.

 

[nocfn]

watching with popcorn, but curious if there is an E500E definitive fix for the noisey result from stepping on the brake pedal? (audible annoyance only not a braking problem)

 

[yao500e]

Hello @gsxr

brake booster model: Lucas A0044302730.

 

[gsxr]

brake booster model: Lucas A0044302730.

Got it. You upgraded 2 steps, from the single-diaphragm 10" with 3.85 boost factor used on most 6-cyl 124 and most W202, to the dual-diaphragm 8/9" with 5.60 boost, used on the 400E/500E and most R129's to 1997. Should be a pretty big difference.

Did you retain the original master cylinder?

 

[nocfn]

Does that one fart as well (since it is for the E500E/E400E?

 

[yao500e]

Got it. You upgraded 2 steps, from the single-diaphragm 10" with 3.85 boost factor used on most 6-cyl 124 and most W202, to the dual-diaphragm 8/9" with 5.60 boost, used on the 400E/500E and most R129's to 1997. Should be a pretty big difference.

Did you retain the original master cylinder?

Yes. i retained the stock C36 master cylinder. not sure what the difference of master cylinders. physically, they looked very similar so my mechanic just decided to keep the stock one.

 

[Santosmercedes]

Got it. You upgraded 2 steps, from the single-diaphragm 10" with 3.85 boost factor used on most 6-cyl 124 and most W202, to the dual-diaphragm 8/9" with 5.60 boost, used on the 400E/500E and most R129's to 1997. Should be a pretty big difference.

Did you retain the original master cylinder?

Hello Dave,

First of all, I wanted to thank you for your great contribution to the community.
Do you happen to have any information (diameter / boost factor, etc.) about part number A0044302730, please?

I am looking to upgrade the brake booster and master cylinder on my W124.
For the master cylinder, I am considering using A0044307501.

For the brake booster, I initially planned to use A0044302230 or A0044306530, but they are very difficult to find in my area.
I was therefore thinking about switching to A0044302730, but I’m not sure what the differences are.

 

[gsxr]

Hello Dave,

First of all, I wanted to thank you for your great contribution to the community.
Do you happen to have any information (diameter / boost factor, etc.) about part number A0044302730, please?

I am looking to upgrade the brake booster and master cylinder on my W124.
For the master cylinder, I am considering using A0044307501.

For the brake booster, I initially planned to use A0044302230 or A0044306530, but they are very difficult to find in my area.
I was therefore thinking about switching to A0044302730, but I’m not sure what the differences are.

What year / model is your 124? Be careful with the upgrades, the wrong mix of parts can result in sub-optimal braking performance.

A0044302730 does not exist in the EPC but appears to be used on 6-cyl 140 and most R129 (except V12 and late R129). If so, it's the same size / boost factor as the 400E/500E booster. A0044306530 is the 400E/500E booster.

I'm not sure about the differences between the various boosters, but the location of the vacuum port may vary, which could cause problems.

If you haven't seen my brake spreadsheet before, click here, check out the page with booster specs. Part numbers are not on there... I need to try and add those for reference. So, it takes some work to figure out what part numbers are used on which chassis/engine combination.

 

[yao500e]

What year / model is your 124? Be careful with the upgrades, the wrong mix of parts can result in sub-optimal braking performance.

A0044302730 does not exist in the EPC but appears to be used on 6-cyl 140 and most R129 (except V12 and late R129). If so, it's the same size / boost factor as the 400E/500E booster. A0044306530 is the 400E/500E booster.

I'm not sure about the differences between the various boosters, but the location of the vacuum port may vary, which could cause problems.

If you haven't seen my brake spreadsheet before, click here, check out the page with booster specs. Part numbers are not on there... I need to try and add those for reference. So, it takes some work to figure out what part numbers are used on which chassis/engine combination.

hi @gsxr I messaged you directly. if you get a chance to check it. thank you!

 

[Santosmercedes]

What year / model is your 124? Be careful with the upgrades, the wrong mix of parts can result in sub-optimal braking performance.

A0044302730 does not exist in the EPC but appears to be used on 6-cyl 140 and most R129 (except V12 and late R129). If so, it's the same size / boost factor as the 400E/500E booster. A0044306530 is the 400E/500E booster.

I'm not sure about the differences between the various boosters, but the location of the vacuum port may vary, which could cause problems.

If you haven't seen my brake spreadsheet before, click here, check out the page with booster specs. Part numbers are not on there... I need to try and add those for reference. So, it takes some work to figure out what part numbers are used on which chassis/engine combination.

---

I have a 1991 W124 250 Turbo Diesel (124.128) that has been swapped with an OM605 turbo diesel engine. Of course, I used your website, aka the W124 Bible.
For the braking system, I made the following modifications:
Front: ATE 320×30 0014200083 / 0014200183
Rear: ATE 278×9 1294200283 / 1294200383
I tried to replicate the U.S.-spec E500 setup, which normally uses 278×24 discs on rear, but the calipers were difficult to find and very expensive. I believe that since the disc diameter and piston sizes are the same, there should not be any brake balance issues; however, brake endurance will obviously not be the same, and there is a risk of disc warping. If that turns out to be the case, I will try to source 278×24 discs or possibly 300×22.

For the master cylinder, I am planning to use a new A0044307501, most likely from ATE.

Regarding the brake booster, I have just found an A0044306530. I will see whether the braking is too sensitive with it; otherwise, I will do as you did and try to find a limousine brake booster, A0044300030. Do you know whether TRW is a good brand for brake boosters?

 

[gsxr]

---

I have a 1991 W124 250 Turbo Diesel (124.128) that has been swapped with an OM605 turbo diesel engine. Of course, I used your website, aka the W124 Bible.
For the braking system, I made the following modifications:
Front: ATE 320×30 0014200083 / 0014200183
Rear: ATE 278×9 1294200283 / 1294200383
I tried to replicate the U.S.-spec E500 setup, which normally uses 278×24 discs on rear, but the calipers were difficult to find and very expensive. I believe that since the disc diameter and piston sizes are the same, there should not be any brake balance issues; however, brake endurance will obviously not be the same, and there is a risk of disc warping. If that turns out to be the case, I will try to source 278×24 discs or possibly 300×22.

Nice upgrade there! The non-vented rears should provide the same brake bias as a USA-spec E500, just with a bit less fade resistance. The 320mm fronts are a massive improvement on the lightweight 124.128 chassis.

For the master cylinder, I am planning to use a new A0044307501, most likely from ATE.

Regarding the brake booster, I have just found an A0044306530. I will see whether the braking is too sensitive with it; otherwise, I will do as you did and try to find a limousine brake booster, A0044300030.

You may find the pedal to be a little touchy, depending on the brake pad compound used. However, test drive and see what you think.

Do you know whether TRW is a good brand for brake boosters?

I've always obtained used brake boosters. I don't know if TRW makes new aftermarket boosters, but TRW is generally decent stuff (except for their cheap LCA's, but that's a different discussion).