Master cylinder brace: Grimmspeed vs Perrin

[StreetShotz]

One steel with a cap, one aluminum without, one beefed up aluminum one with a bolt (not a proper flat surface, just a 8.8 bolt) and then the knock off of the Perrin unit with "stronger" aluminum.

Man on man.

Seems like the only thing getting people over the GS is that little cap.....you can source these online to fit over the end of the Perrin unit, however this defeats one of the purposes of the bolt Perrin decided to use on there units.
Also worth mentioning, unless the end of the master and the cap used are perfectly flat (both matted machined surfaces) there will be room for movement between the two pieces. Easy way to test is mount the unit and use some feeler gauges around the edges of the cap and see how one side opens up and the other side tightens down under pedal application.

I have both units used by customers and have tested this but failed to get it on video. When the car comes in again I will grab a video of this.

[GrimmSpeed]

Originally Posted by StreetShotz

One steel with a cap, one aluminum without, one beefed up aluminum one with a bolt (not a proper flat surface, just a 8.8 bolt) and then the knock off of the Perrin unit with "stronger" aluminum.

Man on man.

Seems like the only thing getting people over the GS is that little cap.....you can source these online to fit over the end of the Perrin unit, however this defeats one of the purposes of the bolt Perrin decided to use on there units.
Also worth mentioning, unless the end of the master and the cap used are perfectly flat (both matted machined surfaces) there will be room for movement between the two pieces. Easy way to test is mount the unit and use some feeler gauges around the edges of the cap and see how one side opens up and the other side tightens down under pedal application.

I have both units used by customers and have tested this but failed to get it on video. When the car comes in again I will grab a video of this.

This all sounds accurate! The only thing I would add is that the cap that we use is machined for a loose fit where it interfaces with our bolt. That allows the cap to pivot around the bolt and sit flat against the master cylinder (as opposed to a cap that threads on). It's a little unclear if that's what you were saying or not, so I thought I'd clarify.

Matt Beenen
Engineering

[Snowblind]

I have the Grimmspeed brace and it firmed up my pedal feel and made my **** larger. Great product A+.

[StreetShotz]

Originally Posted by GrimmSpeed

This all sounds accurate! The only thing I would add is that the cap that we use is machined for a loose fit where it interfaces with our bolt. That allows the cap to pivot around the bolt and sit flat against the master cylinder (as opposed to a cap that threads on). It's a little unclear if that's what you were saying or not, so I thought I'd clarify.

Matt Beenen
Engineering

So if that's the case and the cap does not have a machined to fit 100% on the bolt you are not dispersing any load over a greater area.
If your cap sits on the master cylinder, and is a flat surface it will act much like an extension to the master cylinder, there for putting all the pressure on the end of the bolt (just like the Perrin) unit. So the comments about the amount of load per surface area are in fact mute as the tip of the bolt in both units in fact takes the full load of any force applied.
The only unit that I see dispersing any loads would be the Radium as it has a fixed cap (the bolt head) that it uses to support the master cylinder (but given it is not a perfect machined surface on the master or bolt there is uneven load dispersion).

At the end of the day, and with science to back it, there really is no one that is better than the other in its function (or idea of function). They all preform the same function for the same price point.

What would be cool to see is the Perrin unit with the GS cap on it.....sell the red caps separate from the brace?

[GrimmSpeed]

Originally Posted by StreetShotz

So if that's the case and the cap does not have a machined to fit 100% on the bolt you are not dispersing any load over a greater area.
If your cap sits on the master cylinder, and is a flat surface it will act much like an extension to the master cylinder, there for putting all the pressure on the end of the bolt (just like the Perrin) unit. So the comments about the amount of load per surface area are in fact mute as the tip of the bolt in both units in fact takes the full load of any force applied.
The only unit that I see dispersing any loads would be the Radium as it has a fixed cap (the bolt head) that it uses to support the master cylinder (but given it is not a perfect machined surface on the master or bolt there is uneven load dispersion).

At the end of the day, and with science to back it, there really is no one that is better than the other in its function (or idea of function). They all preform the same function for the same price point.

What would be cool to see is the Perrin unit with the GS cap on it.....sell the red caps separate from the brace?

Yes you're absolutely right, the bolt DOES take the full force of the load applied. And it transfers that load to the machined cap, which then applied that force over a much larger surface area to the master cylinder. This is done so for two reasons:

1. It does not marr and dig into the cast master cylinder, eliminating any source of potential damage or failure.

2. It allows the cap to MOVE. The master cylinder doesn't simply move forward or backward, it moves in an arc shape. Watch the deflection videos that we've posted and you'll see exactly what I'm talking about. When the master cylinder moves in that arc our machined stop allows the face of the master cylinder to slide, as well as pivot. This helps to eliminate the bending forces that would be in place due to a bolt simply digging into the master cylinder, or from a fixed stop, because those two fixed solutions will try and prevent the slight arc motion (which isn't felt, but contributes to fatigue as it is a cyclic motion).

So the comments about the amount of load per surface area are not moot, as they are referring to the amount of load on the face of the master cylinder's face, and we've done this on all of our master cylinder brace designs for the two reasons I've mentioned above. Make sense?

Chase
Engineering

[StreetShotz]

Originally Posted by GrimmSpeed

Yes you're absolutely right, the bolt DOES take the full force of the load applied. And it transfers that load to the machined cap, which then applied that force over a much larger surface area to the master cylinder. This is done so for two reasons:

1. It does not marr and dig into the cast master cylinder, eliminating any source of potential damage or failure.

2. It allows the cap to MOVE. The master cylinder doesn't simply move forward or backward, it moves in an arc shape. Watch the deflection videos that we've posted and you'll see exactly what I'm talking about. When the master cylinder moves in that arc our machined stop allows the face of the master cylinder to slide, as well as pivot. This helps to eliminate the bending forces that would be in place due to a bolt simply digging into the master cylinder, or from a fixed stop, because those two fixed solutions will try and prevent the slight arc motion (which isn't felt, but contributes to fatigue as it is a cyclic motion).

So the comments about the amount of load per surface area are not moot, as they are referring to the amount of load on the face of the master cylinder's face, and we've done this on all of our master cylinder brace designs for the two reasons I've mentioned above. Make sense?

Chase
Engineering

Would that not be backwards?
1) Driver applies pressure to the pedal
2) Pressure transfers from pedal to master
3) Master applies pressure to the cap
- Being that the cap is not a machined to match surface to the master there is no time where it makes 100% contact with the face of the master cylinder. Also, as it is not a machined fit for the bolt, it does not make 100% contact with the bolt either.
4) Cap applies pressure to the bolt and then the bolt applies pressure to the bracket that is bolted to the strut tower.

My point is that being the cap is not completely flat, nor is the master, that there is no additional load dispersion compared to other designs. This coupled with the fact that all the load from the cap is applied to the tip of the bolt would not distribute the load forces any better than any other design. The only benefit of a cap such as that would be for aesthetics and allowing for there to be little/no damage to be caused during use.

To make the cap more functional as a load bearing surface, you could thread it so that is engages the threads as well as the tip of the bolt which would distribute the load forces over a greater surface area on the bolt to allow for less stress on the unit.

[GrimmSpeed]

Originally Posted by StreetShotz

Would that not be backwards?
1) Driver applies pressure to the pedal
2) Pressure transfers from pedal to master
3) Master applies pressure to the cap
- Being that the cap is not a machined to match surface to the master there is no time where it makes 100% contact with the face of the master cylinder. Also, as it is not a machined fit for the bolt, it does not make 100% contact with the bolt either.
4) Cap applies pressure to the bolt and then the bolt applies pressure to the bracket that is bolted to the strut tower.

My point is that being the cap is not completely flat, nor is the master, that there is no additional load dispersion compared to other designs. This coupled with the fact that all the load from the cap is applied to the tip of the bolt would not distribute the load forces any better than any other design. The only benefit of a cap such as that would be for aesthetics and allowing for there to be little/no damage to be caused during use.

To make the cap more functional as a load bearing surface, you could thread it so that is engages the threads as well as the tip of the bolt which would distribute the load forces over a greater surface area on the bolt to allow for less stress on the unit.

Is it backwards? Nope. With a basic understanding of physics we know that if a force is applied in one direction, and there is no motion, there is an equal force applied from the other direction. So lets consider the interface between the load distributing machined cap and the master cylinder to be the center of our free body diagram. For right now lets assume that the master cylinder is not moving in a slight arc, but rather moving in a a pure X direction (if we don't there will be a slight component of Y direction movement, and the forces will not equal zero).

So pressure is applied at the pedal, and since the rod on the master cylinder is not held captive we can assume that the force transferred to the master cylinder is in the pure X direction, and is increased due to the lever arm from the pedal. This force is applied to the brakes, and excess force to the firewall. With no opposing force, the firewall, and thus the master cylinder, moves fore and aft. We'll refer to this movement in the positive direction (+), and thus a force in the positive direction.

So to oppose this movement we introduce the master cylinder brace. We know that to resist this movement we need to provide an equal and opposite force (we'll even assume no preload on the brace, to keep the initial displacement of the master cylinder to be at x=0, and not a negative number). The MCB is bolted to the strut tower to provide a ground. The stud is secured through the MCB, and the cap is pushed up against the stud. In this condition there is zero movement, and zero net force.

Now when we load the brake pedal, to achieve no movement at the master cylinder, the ground point must provide an equal, but opposite force, which it does. That force is transferred through the MCB, transferred through the stud, transferred through the cap. We consider the free body diagram's center to be the interface between the load distributing cap and the master cylinder face because this is the point of interest, and if the parts were separate there would be a displacement, which is not the goal of the MCB.

Now you can choose where you decide the center of the diagram is, which is what you're saying about what I was saying being backwards. You could say that since everything is connected and static that the force from your foot to the brake pedal acts entirely in one direction (+) all the way through the MCB, and the ground point (the strut tower) provides the negative force, and you'd be right.

But what I'm having a hard time explaining is that when we're talking about the interface between the cap and the master cylinder (the point of interest, and what we're talking about when we say that the load is applied to a much greater surface area on the master cylinder) we would consider the forces acting on the master cylinder and it's displacement as positive, and the forces acting on the the cap from the stud, MCB, and strut tower as negative. So since pressure is force/area the pressure acting on the master cylinder face is going to have the same force from the ground point due to the dramatically increased area, put reduced pressure when compared to the pressure applied to the cap from the stud (same exact force, put increased pressure due to reduced area).

For an analogy get a hammer, a nail, and a piece of wood. Put the pointy end of the nail in the wood and hit it with the hammer. It'll go right in easy depending on how much force you can apply with the hammer. Now get a nail, flip it over so the flat side is on the wood, hit it with the hammer just as hard as you did and see how far (it's displacement) it goes into the wood. It won't be even close.

This is one of the reasons why we have the cap, we wanted to dramatically reduce pressure at the face of the master cylinder while still applying the exact same force necessary to oppose the motion of the master cylinder. We don't care about the pressure being applied to the cap from the stud, as the cap is cheap and replaceable, but more importantly it is machined from billet, and is guaranteed to be 100% consistent (and with years and years of testing) so we know there will be no failures or damage due to pressure. We are also not concerned with the pressure or force at the bolt because through years of testing on the 10s of thousands of MCBs over 7 different cars that we've sold we know that it is a non-issue.

I won't re-explain from my previous post about the cap to stud fit being loose to allow for the master cylinder to move in its arc motion (up and down or side to side), because I think that's pretty well covered by now. If that part didnt make sense either, please let me know. I'm not sure if you read my previous post about why we DIDNT thread the cap on as you suggest in your final paragraph, but it is to reduce the bending force on the stud (think cyclical fatigue), and so that the cap does in fact stay perfectly flat to the face of the master cylinder, which keeps the pressure between the two interfaces THE SAME under all circumstances, as opposed to if the cap were fixed to the bolt, it would allow the master cylinder face to rock against the cap, which would constantly change the area of the cap that is contacting the face, which is what you're saying our design does in the first place. But in fact the opposite is true, not holding the cap captive is the ONLY reason why we can guarantee that the pressure between the master cylinder and the cap stays consistent, and why we chose this design, and trust us, we tested the other design 5 years ago and did not like it.

I really hope that this makes sense to you, because what you're saying is the problem with our design and how to fix it is, actually the strength of our design and fixes the condition that you're concerned with.

Also, I'm not sure if you've actually installed one of these or why you're saying our cap is not completely flat, and that the master cylinder is not completely flat, because I assure you that both of these surfaces are VERY flat.



Let me know if there is anything else I can help you with,
Chase
Engineering

[StreetShotz]

Great info, but my points still stand.

I have installed a good half dozen of these on various cars (both BRZ and FRS) and there great units. Nothing but positive things to say.

The analogy of the hammer and nail works for me. However lets break that down a little further.
In your case the hammer (master) and nail (bolt and cap) and in 3 pieces. The head of the nail (the cap in this case) is separate from the nail (bolt). If you are hammering a nail with a head that's not attached, but sitting on top of the shank of the nail you will not be transferring the force exerted on the head (cap) of the nail to the body of it.

As for the surfaces being flat, the cap may be perfectly flat, however the master varies widly between cars. I currently have 6 in shop and they are all different. With one item being near perfectly flat and the other not being completely flat then you are not distributing load as described.
Either way, it works for the purpose designed and works well.

[Shankenstein]

Originally Posted by GrimmSpeed

Let me know if there is anything else I can help you with,
Chase
Engineering

Chase & Jeff - In case it's not said often enough, the 86 community appreciates the honest and thorough answers that you guys take the time to provide.

It only takes 1 person to say that "6061 is a decorative material" and the myth gets perpetuated.

Coated steel is cost effective and works for most environments. Grimmspeed's focus has been functionality (with an approachable price tag), so it's easy to see why they went in this direction.

For aluminum, here are the main choices (disregarding cast alloys):
2024 for high strength, medium corrosion resistance
6061 for medium strength, high corrosion resistance,
7075 for high strength, high corrosion resistance

If you aren't welding it and cost is irrelevant... 7075 is excellent. 6061 is half the cost and easier to work. 2024 is solid, but for exposed locations (like an engine bay) you'll want to coat it. For Perrin's goals (gorgeous but functional parts) 6061 was a great choice.

Pick the one that's best for your budget, location, and purpose. The design of both parts gets the job done.

- friendly neighborhood engineer

[GrimmSpeed]

Originally Posted by StreetShotz

Great info, but my points still stand.

I have installed a good half dozen of these on various cars (both BRZ and FRS) and there great units. Nothing but positive things to say.

The analogy of the hammer and nail works for me. However lets break that down a little further.
In your case the hammer (master) and nail (bolt and cap) and in 3 pieces. The head of the nail (the cap in this case) is separate from the nail (bolt). If you are hammering a nail with a head that's not attached, but sitting on top of the shank of the nail you will not be transferring the force exerted on the head (cap) of the nail to the body of it.

As for the surfaces being flat, the cap may be perfectly flat, however the master varies widly between cars. I currently have 6 in shop and they are all different. With one item being near perfectly flat and the other not being completely flat then you are not distributing load as described.
Either way, it works for the purpose designed and works well.

Excellent, I completely agree that they're both great units. We said it before and I'll say it again, when it comes to choosing which one, pretty much just buy the one that you like better as far as form and function goes. And I appreciate that you've worked with both as it lends some great feedback.

And in this case the hammer and nail analogy actually works perfectly again. Since the "wood" is the face of the master cylinder, it should make a great deal of sense, as the head of the nail when contacting the wood behaves as the cap, the shaft of the nail being contacted by the hammer behaves as the stud, and the hammer behaves as the strut tower, since it is applying the opposing force. You're mistaking it for an impact force, instead of the instantaneous force that occurs once the hammer contacts the nail.

Now in the instance you're saying about when you would make the nail into two pieces, a head and a shaft. What I say still is true. You said "If you are hammering a nail with a head that's not attached, but sitting on top of the shank of the nail you will not be transferring the force exerted on the head (cap) of the nail to the body of it."

You 100% WILL be transferring all of the force (except the minute amount lost as heat on contact). Why wouldn't it transfer? If you cut the head off a nail, set it on top of the nail, and hit it with a hammer straight on, it will go in the exact same amount as if the nail was one piece. The force can not disappear into thin air since energy is conserved.

This is because at the instant the hammer contacts the head of the nail, it is already in contact with the nail, and at that instant they ALL act as one piece. Don't believe me? Try it. Don't want to cut the head off a nail? Put a penny on top of the nail and hit it, it'll act exactly the same, and the argument that the force isn't transferred because it is not 1 piece will be debunked. Don't want to do that? Put a cap on an egg, and hit it with a hammer. The three parts are not connected, but at that one instant when the hammer hits they will be, the force will transfer through the cap 100% (assuming no heat or deformation) and the egg will surely break.

The force is transferred in an instant, and they all behave as one body at that instant because they are all touching each other with no gaps or displacement.

We know this is always true on our master cylinder because we tell customers to preload it a certain amount. This not only provides some initial force from the strut tower, but also ensures that the displacement between the stud, cap, and master cylinder face is always zero.

I really hope that this makes sense because I'm running out of ways to explain the same thing, and we might just have to agree to disagree so I can go back to designing parts

Originally Posted by Shankenstein

Chase & Jeff - In case it's not said often enough, the 86 community appreciates the honest and thorough answers that you guys take the time to provide.

Thanks Shank I really appreciate that (I'm sure Jeff does too). We appreciate the work, info, and help you've put into the community too. I feel like not too many people realize just how difficult of a job this can be sometimes, and we appreciate support from everyone

Chase
Engineering

[GrimmSpeed]

Originally Posted by GrimmSpeed

Don't believe me? Try it.

Just sayin.

Matt Beenen
Engineering

[KelvinBRZ]

Excuse me for reviving a dead thread, but I've started my investigation on the master cylinder brace yesterday. I'm aware there's $60 & $100 ones, which I'll have to dive into a bit further.

The real question is... Should I be investing a similar amount of money in an upgraded winmax w1 sport brake pads, or a MC brace?

I DD my BRZ, and it seems like under hard brakes, the brake pedal travels too much, as well as the brakes don't seem that confident.

[MightyMeeple]

Originally Posted by KelvinBRZ

I DD my BRZ, and it seems like under hard brakes, the brake pedal travels too much, as well as the brakes don't seem that confident.

Question: have you upgraded tires?

I actually feel like there is just a little too much travel in the brake pedal until I really get onto it....but once I'm there the brakes do a fantastic job of stopping the car (I'm referring to spirited driving on street).

[KelvinBRZ]

Originally Posted by MightyMeeple

Question: have you upgraded tires?

I actually feel like there is just a little too much travel in the brake pedal until I really get onto it....but once I'm there the brakes do a fantastic job of stopping the car (I'm referring to spirited driving on street).

Nope hahah, same old Prius tires that came stock 30k miles ago

I agree that there is a lot of travel - I wonder if the MC brace will fix that