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Improved brake feel and performance by reducing master cylinder movement
Several brackets kits available online which brace the master cylinder via the strut tower mounts to counteract arc movement of the master cylinder due to firewall flex
Radium Engineering offers such a kit:
"The 6061 billet aluminum brace reduces firewall flex for a more positive pedal feel. It mounts to pre-existing threaded holes in the engine bay and requires no permanent vehicle modification."
"Because the master cylinder flexes in an arcuate path, a specially designed CNC machined foot contacts the master cylinder to counteract the arc movement. Preload is adjusted with the anodized aluminum green bolt then locked in place with the jam nut. Installation is simple and takes around 30 minutes."
Anyone aware of "arcuate" movement of Lexus master cylinders?
Perhaps discernable movement under heavy braking.
Probably less firewall flex on an Lexus LS400 than other makes.
However, if any master cylinder movement, then would contribute to overall mushy pedal feel.and longer stopping distances, especially under emergency stopping (entire master cylinder moves with firewall before pumping brake fluid)
Several brackets kits available online which brace the master cylinder via the strut tower mounts to counteract arc movement of the master cylinder due to firewall flex
Radium Engineering offers such a kit:
"The 6061 billet aluminum brace reduces firewall flex for a more positive pedal feel. It mounts to pre-existing threaded holes in the engine bay and requires no permanent vehicle modification."
"Because the master cylinder flexes in an arcuate path, a specially designed CNC machined foot contacts the master cylinder to counteract the arc movement. Preload is adjusted with the anodized aluminum green bolt then locked in place with the jam nut. Installation is simple and takes around 30 minutes."
Anyone aware of "arcuate" movement of Lexus master cylinders?
Perhaps discernable movement under heavy braking.
Probably less firewall flex on an Lexus LS400 than other makes.
However, if any master cylinder movement, then would contribute to overall mushy pedal feel.and longer stopping distances, especially under emergency stopping (entire master cylinder moves with firewall before pumping brake fluid)
Input? YES- The title of the video reads "Cure for Scion FR-S/Subaru BRZ firewall flex during braking"
Correct me if I'm wrong but you drive an LS400. I'll go out on a limb and speculate an LS has little to NO firewall flex.
Radium offers several products designed for a variety of makes and models both foreign and domestic. Their Toyota/Lexus section mainly caters to the Supra and IS crowd. Not a single product offering was designed for an LS vehicle.
Go ahead, spend the $80 and write a subsequent post telling everyone brake pedal feel is discernably "Better"
I'll hang on to my 80 bucks
Input? YES- The title of the video reads "Cure for Scion FR-S/Subaru BRZ firewall flex during braking"
Correct me if I'm wrong but you drive an LS400. I'll go out on a limb and speculate an LS has little to NO firewall flex.
Go ahead, spend the $80 and write a subsequent post telling everyone brake pedal feel is discernably "Better"
I'll hang on to my 80 bucks
Pay attention...
Am presenting a concept that may or may not be applicable to Toyota or Lexus.
The post inquired whether master cylinder movement on LS400...not rank speculation or the troll down under.
In the 5 minutes since I posted, you located and persuaded a second person to assist you, then dropped everything you were doing, ran out to your LS400 and determined zero movement of your LS400 master cylinder??
Now, since you started something here, if at all you pretend to intend to contribute meaningful input here, kindly locate that second person, have them actuate your brake pedal and report back to us whether discernible master cylinder movement.
Thank you. The title states: " Improved brake feel and performance by reducing master cylinder movement"
[QUOTE=YODAONE;10975095]Pay attention... The title states: " Improved brake feel and performance by reducing master cylinder movement"[/QUOTE
Pay attention... Always, early, and often.
Am presenting a concept that may or may not be applicable to Toyota or Lexus. "Anyone aware of "arcuate" movement of Lexus master cylinders?"
The post inquired whether master cylinder movement on LS400...not rank speculation or the troll down under. If you're inquiring a "?" at the end of the thread title would be appropriate.
In the 5 minutes since I posted, you located and persuaded a second person to assist you, then dropped everything you were doing, ran out to your LS400 and determined zero movement of your LS400 master cylinder?? You mentioned Speculation...
(I own a 430 btw)
Now, since you started something here, if at all you pretend to intend to contribute meaningful input here, kindly locate that second person, have them actuate your brake pedal and report back to us whether discernible master cylinder movement. ??????????????.........
Thank you.
The title states: " Improved brake feel and performance by reducing master cylinder movement"
I have a hard time believing that there is any flex whatsoever in LS400 firewall, but an even harder time understanding how it would affect the pedal feel.
The master is engaged by the pushrod in the booster which is directly bolted to the brake. If one moves they all move equally.
Not exactly an expert but the brakes are the one thing on my car I know best since I had to replace every single component of it when I got it. Went through many rounds of bleeding masters and calipers and not once did I notice any movement of the master whatsoever.
Maybe if you put power brakes on a yugo or something then it would come in to play. Surely not an LS.
It's a very interesting post though. I own a 97 & 00 Lexus LS400s & also have an 02 Mercedes CL500 & 03 E500, all in tip top shapes. I bought the 97 LS when it was a year old so I have it for 23 years now & it still drive like new. About 7 years ago, the master cylinder on the 97 LS started to leak so I replaced it along w/ new brake hoses on all 4 corners. Anyway, between the Lexus & Mercedes vehicles, I feel the Mercedes' brakes are much more firmer & powerful than the Lexus' brakes. For years, I've been wondering if it has some to do w/ the design, the brake components or the thickness of the firewalls since the Mercedes outweigh the Lexus by about 500 lbs (~ 3700 vs 4200 given or take). Perhaps, Yoda is right about there's more master cylinder movement in the Lexus' brake due to the thickness of the firewall???
As long as you can trigger ABS in the dry, the braking system is more powerful than the tires, you're already getting the best stopping distance the car can do. Most cars can do this stock. You can put the biggest brakes in the world and it won't improve your stopping distance at all because the limit is in the tires. You would have to upgrade tires and\or suspension geometry to improve stopping distances.
Less compliant suspension would keep the car "flatter", resulting in less dive when you slam on the brakes. It would also reduce suspension deflection on the front wheels, which keep a better contact patch on the road, probably resulting in slightly better stopping performance. Upgrading brakes typically improves two areas: you have more tire than brake and can't trigger ABS, or more commonly, you want improved cooling performance for higher performance driving and not overheat the brakes\fluid.
As for pedal feel and immediacy, modern cars have been trending towards a firmer pedal for quite some time now. This is very much tuning within the hardware itself, rather than any mounting brackets. You won't get a firm pedal like a modern car just by making the mounting point better. I'm going to say you would have much larger impacts by changing the brake cylinder itself to a higher boost ratio, which would make for a firmer pedal and less "sponge". But that comes with it's own challenges.
I dunno if reinforcing the master would do much. I think it's one of those things where you have to test it to see if that is a weakpoint in the system. Maybe it helps, maybe it doesn't. It's a valid hypothesis to test though.
Before buying\fabricating parts, I would imagine a test for this would be quite straightforward. Get a friend (or a camera), pop the hood, look at the master cylinder. Stand on the brakes and see if it moves.
A bracket like this concerns me slightly though, because now you're putting longitudal stress throughout the master cylinder, in a manner in which it hasn't been designed for. Would that impact any of the seals\gaskets if it were suddenly being pressed against quite heavily?
400fanboy- Working on cars is 1 of my many hobbies for over 40 years so I consider myself a car guy but based on your explanation, you sure know a lot more about brake than I do. What you've stated makes sense so I agree with you 100% on this. Thank you
Fyi, my 03 E500 comes equipped w/ SBC (Sensotronic Brake Control) aka brake-by-wire system. Since it's computer controlled, the braking is very firm, effortless & the stopping power is so good but it takes some use to w/ the system.
I am very much your junior, but I am an nerd to learn facts. I like knowing how things work. But I can't wrench on anything to save my life. I guarantee YODAONE knows infinitely more than I do based on what I see him post around these parts .
Brake feels is totally independent on actual braking power. These are kinda two different discussions to have. Tuning the brake pedal to be "firmer" gives the impression that the car stops better. But in reality, you just more easily reach max braking pressure without having to stand on the pedal. You aren't really stopping meaningfully quicker.
You can also get into the weeds with brake by wire systems and their... compromised feel because there is no physical connection to the brakes, and your inability to properly modulate the brakes. I really have a bone to pick with Volkswagen cars in this regard. Audi is ok, but a lot of Jetta's I've been in over the last 10 years have been atrocious in this regard.
I have a hard time believing that there is any flex whatsoever in LS400 firewall, but an even harder time understanding how it would affect the pedal feel.
The master is engaged by the pushrod in the booster which is directly bolted to the brake. If one moves they all move equally.
Not exactly an expert but the brakes are the one thing on my car I know best since I had to replace every single component of it when I got it. Went through many rounds of bleeding masters and calipers and not once did I notice any movement of the master whatsoever.
Maybe if you put power brakes on a yugo or something then it would come in to play. Surely not an LS.
As time permits, will affix a dial indicator to determine if any master cylinder movement while depressing brake pedal and post results.
It may well be movement is negligible.
The investigation is based on the premise that if firewall at brake booster mounting point flexes, then that movement, if excessive, suggests that the master cylinder pistons do not move as quickly until the flex has run its arc.
The brake pedal assembly exerts a certain amount of leverage that could impart flex on the firewall.
At any rate if zero firewall flex, then a moot point, but such a simple measurement to acquire so felt compelled to investigate.
As time permits, will affix a dial indicator to determine if any master cylinder movement while depressing brake pedal and post results.
It may well be movement is negligible.
The investigation is based on the premise that if firewall at brake booster mounting point flexes, then that movement, if excessive, suggests that the master cylinder pistons do not move as quickly until the flex has run its arc.
The brake pedal assembly exerts a certain amount of leverage that could impart flex on the firewall.
At any rate if zero firewall flex, then a moot point, but such a simple measurement to acquire so felt compelled to investigate.
Would be interested to hear about the result 👍
I'm just wondering how significant the flex has to be before it actually translates into noticeable difference. Just considering newton's third makes me feel like it would only be even measurable with a severe jab of the pedal. I lack the dials to test this myself though so Ill wait for your conclusion.
Fixtured a dial indicator to measure master cylinder movement when actuating brake pedal.
First measured up - down. No measurable movement...
Yet I could see movement..but it was in and out, forward and back, in line with the angle of the master cylinder.
Refixtured the dial indicator to register in/out movement...
01-17-21, 08:51 PM
Improved brake feel and performance by reducing master cylinder movement
