I want decreased pedal travel!

[Sean]

I did lots of reading today, on the 25mm master cylinder upgrade, among other things I've come to the following conslusions:

- The 750i 25mm Master Cylinder DOES decrease pedal travel
- The new MC DOES stiffen the pedal
- The new MC DOES require MORE effort from your leg to gain the same braking force. This is mechanical a FACT. When you increase the size of a piston on one end, and leave the other end the same, more force is required to equal the same distance traveled. Go here if you don't understand my attempt at basic explaination: http://auto.howstuffworks.com/brake.htm

From my understanding, getting this "upgraded" master cylinder WILL make heel-toeing MUCH easier. The problem I have on the track is, I'm not able to fully depress my damn brake pedal because I'm trying to downshift too, therefore I'm missing out on extra braking force. At the same time, since I'm not using ALL my braking force, I'm braking for a longer distance, thus heating my brakes up more than needed. This can lead to my issue I've had before, where my brakes begin to fade. I believe this causes the pads to glaze over.

Needless to say, I'm positive that doing such a change to my brakes will in fact decrease my brake pedal travel. That's certain.

However, there's one issue that remains. Due to this change, more force must be applied to the pedal to reach the same braking force (or piston travel distance)

So - unlike all previous threads on this forum that discuss this master cylidner upgrade (there are many - I know) - I pose a new question.

The point of this massive post: --------
It is this: If I upgrade to a 25mm master cylinder - can I upgrade the size of my brake booster to reverse the effects of the added pressure needed on the pedal? If so - what can I use???

DISCUSS


NOTE: We are not discussing the 25mm master cylinder upgrade - we are specifically discussing upgrading the brake booster. KTHXBYE!


LOL just realized I posted 3 threads in here in like 2 days time. oooo well.

[jlevie]

Hmm, I don't seem to have any problem in achieving threshold braking while heel & toeing with the OE brake configuration. Could it be that your technique and/or pad choice is less than optimum?

By threshold braking, I mean to the point that t6he slightest increase in pressure will lock up a front wheel as I have the ABS disabled on purpose in order to gain more braking performance.

[AlarmedBread]

Modify the throttle pedal so that it is lower to begin with, much cheaper and easier than messing with the brake booster etc.

[golde30]

^^that would work.

on my s50 swap with IX booster mounted to the firewall without spacer, i didnt cut the push rod down enough, so i had to bend the pedal tab forward a little bit (making my pedal higher to begin with) and now my breaks are super sensitive. i only need to press in the pedal about 1" for street driving.

[monty]

My car has the 750 master and it does take a lot of force to brake, it does'nt see the track, but on the street I dont really like it because if I have to dynomite the brakes because some ass clown pulls out in front of me it takes a greater distance to stop and isnt fun. I am looking to put the OE master back on so the braking is more responsive. Although you would think the 750 would improve response because it is made for a larger car?

[rwh11385]

I did lots of reading today, on the 25mm master cylinder upgrade, among other things I've come to the following conslusions:

- The 750i 25mm Master Cylinder DOES decrease pedal travel
- The new MC DOES stiffen the pedal
- The new MC DOES require MORE effort from your leg to gain the same braking force. This is mechanical a FACT. When you increase the size of a piston on one end, and leave the other end the same, more force is required to equal the same distance traveled. Go here if you don't understand my attempt at basic explaination: http://auto.howstuffworks.com/brake.htm

From my understanding, getting this "upgraded" master cylinder WILL make heel-toeing MUCH easier. The problem I have on the track is, I'm not able to fully depress my damn brake pedal because I'm trying to downshift too, therefore I'm missing out on extra braking force. At the same time, since I'm not using ALL my braking force, I'm braking for a longer distance, thus heating my brakes up more than needed. This can lead to my issue I've had before, where my brakes begin to fade. I believe this causes the pads to glaze over.

Needless to say, I'm positive that doing such a change to my brakes will in fact decrease my brake pedal travel. That's certain.

However, there's one issue that remains. Due to this change, more force must be applied to the pedal to reach the same braking force (or piston travel distance)

So - unlike all previous threads on this forum that discuss this master cylidner upgrade (there are many - I know) - I pose a new question.

The point of this massive post: --------
It is this: If I upgrade to a 25mm master cylinder - can I upgrade the size of my brake booster to reverse the effects of the added pressure needed on the pedal? If so - what can I use???

DISCUSS


NOTE: We are not discussing the 25mm master cylinder upgrade - we are specifically discussing upgrading the brake booster. KTHXBYE!


LOL just realized I posted 3 threads in here in like 2 days time. oooo well.

dude, you haven't driven your e30 in months....

do you really think you need to be worrying about shorter pedal travel?

don't you like being able to precisely articulate the pedal for just the right amount at the track?

if you want to have more jerk reactions, go with a shorter ratio steering rack TOOOO

[Sean]

My car has the 750 master and it does take a lot of force to brake, it does'nt see the track, but on the street I dont really like it because if I have to dynomite the brakes because some ass clown pulls out in front of me it takes a greater distance to stop and isnt fun. I am looking to put the OE master back on so the braking is more responsive. Although you would think the 750 would improve response because it is made for a larger car?

Good review. Thanks!I needed some feedback on this. It's good to know that not everyone experiences something great. Or rather, that there's a real-world example of this "upgrade" not being an upgrade at all.

Yea...Heeter, I know.... :p I can't help but think about things I can do when I get home though. lol And, actually, I already have a 2.8i rack, and honestly, I love it.

Hmm, I don't seem to have any problem in achieving threshold braking while heel & toeing with the OE brake configuration. Could it be that your technique and/or pad choice is less than optimum?

By threshold braking, I mean to the point that t6he slightest increase in pressure will lock up a front wheel as I have the ABS disabled on purpose in order to gain more braking performance.

Yep, and I wasn't hitting that point. I know for a fact, because I did some turns without heel-toeing, and I could hit the threshold. It's mainly because my size 13 foot and my lack of space for legs since I have to be close for the wheel limits the motion my foot can make. So, rather than "heel-toeing" I'm more of "side-to-side" downshifting.

Modify the throttle pedal so that it is lower to begin with, much cheaper and easier than messing with the brake booster etc.

How do you go about doing that? I need to get home and drive my car...LOL


Is the brake pedal adjustable? I mean, that's all I really want is to get the brake and throttle more even. I'm happy with then feel as is.

Thanks so much, guys, this is what I was lookin for!

[Massive Lee]

The 25mm MC swap was initially intended for owners of e30 M3s with originally bigger 23,8mm MC and bigger caliper pistons. This swap is also great on e30s with brake upgrades.

In the case of a stock e30, going to a 25,4mm MC means a 40% increase in hydraulics. That's a lot. I suggest perhaps using a 23mm MC instead.

[Sean]

I thought about that - but the e30 m3 cylidner requires a different sizes mounting hole for one brake line, doesn't it? Not impossible by any stretch of the word, but I think I’ll investigate other avenues first. Thanks for bringing that up though!

[Massive Lee]

A 23mm MC is available from other cars such as 5 series and have two 8mm outputs. Check e24 and e28 MCs...

[Sean]

A 23mm MC is available from other cars such as 5 series and have two 8mm outputs. Check e24 and e28 MCs...

Same mounting too, with the 2 mounting holes directly across from each other? (both on the horizontal)

[cheades]

You can also change your technique, use your toes on the brake and heel for the gas.

[Sean]

You can also change your technique, use your toes on the brake and heel for the gas.

I would if I could. It's impossible for me to do due to my lack of space for legs.

Maybe I'll invest in a steering wheel + spacer instead of messing with a master cylidner - then I may be able to heel-toe better.

[AlarmedBread]

How do you go about doing that? I'm happy with then feel as is.

As with most things, when someone says 'modify' it means bend, cut, or weld. In this case bend is all you'd need. You'll also need to shorten the pedal stop to get WOT.

I am able to blip the gas perfectly well with things as stock, but I do have a momo wheel with a 1.25" spacer so my knee isn't hitting the wheel anymore. I also use the side of my foot, no one actually uses their heel. ;)

[cheades]

Yes a Momo spacer and smaller wheel make a huge difference, at 6' I have to sit a bit farther back than I like to (which is pretty close) because my knee will just touch the steering column if I don't have it one click back.