Legend2TL

You can believe any of you own theories but that does not necessarily make it true. Brembo also recommends brake fluid replacement every 3 years.

https://www.bremboparts.com/africa/e...-my-car-195105

Have been to a few track days and tech inspection always looked at brake fluid whether car or motorcycle

https://www.roadandtrack.com/motorsp...rack-day-hpde/

Go to 2:00

https://blog.gorally.com/track-day-tech-inspection/

Go to 0:50 in their video.

TypeS22

man when I used to be a service writer we would tell the customer every 3 years, was only $99 so mostly everyone did a brake flush.

BEAR-AvHistory

OK no problem with that. Since you use "I am an engineer" what is your automotive engineering degree in? What auto companies have you worked for & what have you designed for them?

Me I just an US Army trained mechanic who does it for a hobby.

So based on your experience in the automotive engineering business.....what do you think is the condition of this brake fluid & how old is it. To be fair an showing you the cap which is obliviously vented & only has an O-ring on the rim, worse case for brake fluid. Is it safe to drive on do I need to change it now?

Legend2TL

yeah, that's a reasonable cost for a dealer. The latest gen ABS brake systems are the same as non-ABS brake systems to bleed/flush/fill, nowadays I just do single person bleeding/flushing which takes about a hour. Pretty easy to do for the do-it-yourself maintenance.


Meh, what's with the attitude? If you think you know more than brake manufacturers, car manufacturers, track tech inspection, auto tech educators, then believe your theories and forget them.

loki

It could get you in a lot of trouble speaking truth on auto forums, I wouldn't do so much of it. Better to let service commissioned "advisers" give proper advice.

Legend2TL

To many (most?) expanding knowledge and learning are empowerment, to the others ignorance is bliss

Legend2TL

Typically hubs are reused, only have had two not work out due to being pressed in incorrectly (outer hub diameter was squeezed causing rotation in the bearing inner race) in ~40 years. Whenever pressing in new cartridge bearings put them in the freezer for a few hours to contract some making it a little easier. They're probably the same wheel bearing and hub for non-Type-S and Type-S.

I just reread what I wrote and my technique for removing the splash shield is incorrect since the opening is a complete circle smaller than the hub outer diameter. Some of the older Honda's had a opening in the shield where the caliper hanger bracket is making it possible to remove the shield with the hub on but not here.

One other random food for thought is what effect the larger front brake rotor and more piston area has effect on brake balance and braking force, since the master cylinder and proportioning valve are kept?

BEAR-AvHistory

No attitude. I am just trying to find out what your training, practical experience is & what you know VS what you cut paste from manufactures & venders web sites. The other question is really very simple to answer. The question on the brake fluid in the res should be a sitting duck since you have seen someone looking into a res at a tech inspection.

Think you will find no one or next to know one that has ever had or personally changed their brake hoses in a recommended time period except to swap for stainless steel or replace a leaker.

Track inspections:
Note other groups may do it differently

My experience is I take my car to one of the groups selected inspection shops by appointment. In addition to peaking into the the master cylinder the car goes up on a lift wheels are pulled ect to have a full visual inspection then it gets a sticker that it has been inspected. If you have not had the full inspection & sticker, signed inspection report by a group authorized tech you can't run. The sticker also is specific for what the car is approved for. My car is not legal for competition. Then at the track it gets the visual inspection & you saw it gets a stick on color coded dot for the current day after the track visual.

Old AutoX sticker. Car has to be inspected prior to each season. Track Tech covers additional items & is more detailed on safety items

Helmets are examined for current compliance date & are stickered each season.

Seatbelts are date checked to be sure they are still valid. I have an open car do I have arm restraints on my belts, is my Jacket rated so on. Different groups might have different points but they have to cover the tracks requirements.

At the end of the day the point is if you see that some item is in very good condition do you change it because its recommended by someone who has interest in making money off the recommendation?

Legend2TL

Nope, what you wrote below is all attitude.
I referenced brake technical references from a range of legit sources including Brembo, if you wanna believe your theories over them go ahead.

praecisiovectura

With the respect in depth discussion on brake fluid, in light of the presence of other brake systems on gen 2, like, ESB and EBD, I presume that gravity bleeds won't work or as well, and you'll have to use a pressure or vacuum bleeder?



I was draining my oil catch can and was looking in the engine bay for the brake reservoir, and it's under the rear engine cover. Thankfully Acura used captive ones not like the plastic clips that hold the cover over the radiator that get lost or break easy. Of course I didn't remove them or install them per the manual which if you read will save you time or from possibly marring the cover.


As for brake fluid, we definitely don't skimp on it up here, as with hills and mountains, regular servicing is a must. Color is subjective quality, more reliable would be the conductivity testers, you don't have to buy them if you have a multi-meter though. Just simply stick both leads into the fluid and measure a baseline resistance value on good fluid, then check with dirty one to establish a trend as to establish your replacement interval. Same technique can be used for coolant too. The most reliable method is the boil point tester, but your average DIYer won't have one.


One could rock with higher boiling point brake fluid to extend safe operating life. I believe the highest boiling point DOT 3/4/5.1 is Motul 660 which has 600+F, but as others have noted brake fluid is inherently hygroscopic and this absorption can cause corrosion in brake lines. From a safety perspective, the lower the boiling pointing will increase brake distance, or result in complete loss of braking ability in harsh conditions, prolong track use, or going down hill with no engine braking.

For any math, physics or engineering majors on the forum, would be interesting problem to evaluate the sizing of the 2nd gen TLX brake systems, as I know many reviewers have criticized the curb weight of the vehicle.


I believe the above information sufficient to solve, you have weight, as well as distribution at wheels, and diameters of the discs. It would be an interesting trade study, to see 13 v. 14.3 increase in diameter and the presence of 4 pistons on the front on Type S compare to standard calipers. I imagine most people upgrading aren't really tracking their car, and its mainly a CDI, chicks-dig-it factor, like people that paint their calipers red, than that concerned on braking performance to be able to discern a difference. Which, I'm admittedly guilty of doing, painting calipers to have a more sporty look. It's been awhile, but couldn't find any good free-body diagram analysis of brake systems, doing a quick search found a couple reference resources to bookmark and read later, unless you want to start from scratch and re-derive the design equations in the link below:
https://www.mitcalc.com/doc/brakescl...esclutches.htm
https://www.engineeringinspiration.c...rakecalcs.html
https://www.tjprc.org/publishpapers/...IPER%20_1_.pdf

E92Vancouver

Nice job! Those wheel bearings were already looking dry. WTF??? The A-Spec and Type S have the same master cylinder? For real?

BEAR-AvHistory

Dry wheel bearings on an almost brand new car? Expect all those with a 2021 TLX better get into service to get the dry wheel bearing replaced.

mike03a3

The key data missing is the actual area of the pads and the information necessary to calculate it: Ro, Ri and a

praecisiovectura

Gotcha, my bad, well how about these assumptions, just using CAD sketch tracer without having the pads in front of me to pull actual area.

Stock pad area estimated at 15.359 in^2, and Brembo at 22.74 in^2?

Legend2TL

Good math and engineering you linked there.

Oh and somewhere in these engineering equations below you'll find that yes indeed that red or yellow calipers are used that braking forces increase by ∛π/(4*e)

You can see the light gray colored grease at 5:30

IIRC, even the 3G TL had the same master cylinders for the Brembo and regular caliper front brakes.



I assume that gravity bleeding or pedal pressure bleeding can be used to bleed/flush the brake fluid. Don't have the Acura TLX shop manual for bleeding/flushing the brakes but the brakes are very similar up to the brake booster being an electric servo/stepper motor. So as long as the battery is good, I presume the brakes work when the TLX is turned off.

Below is the 4 channel brake modulator braking system for a S2000 which I presume is similar for the PWM control solenoid valves/. The NO (Normally Open hydraulic valves in the ABS modulator allow the brake fluid to return to the reservoir when the pedal is released (releasing the servo motor and hence master cylinder piston allow the fluid supply opening to appear).





And the respective total area of the different calipers pistons and each of their pads dynamic coefficient of friction,

Here's a quick online example that goes through the math and physics

BEAR-AvHistory

Nice presentation. I was reading it & was interested in a few things one related to the fluid. I have been running catch cans since 2011 on my first turbo & was wondering what you had them/it on. Have also run a catch can on one N/A engine 5.0L Coyote but removed it for open filters when I discovered it was not subject to state restrictions or annual inspections.

Second thing I always relied on a tester for determining when I need to change brake fluid not dealer recommendations once a car was out of free factory maintenance that included brake service. They dropped the free brake service that would have covered both my 2020 & 2022. I thought it might be a good time to step up to a better unit than a Chinese knockoff. I have not seen the German tester you showed in your post before.

Did you get it here or in Europe & how well does it work? I have had reasonably good luck with my current unit staying in calibration using a fresh can of fluid as a base line test but there is always some doubt.

BTW if I have to open up any system for any reason I will pressure bleed a fresh can through it before I'm finished.

Camaro194

Yep, looks like you can use traditional methods for bleeding the brakes. I shared the instructions from the FSM

https://acurazine.com/forums/second-.../#post16779616

praecisiovectura

Awesome, thanks for sharing, good to have in the back pocket - got to remember to disconnect the battery though.

I've only had the OCC for a month or so, so less than 1K, with cold weather and short trips mostly murky brown watery-fuel mixture. Although the blow by was more prevalent on Honda's 1.5L engines, anecdotal reports with the K20s, like those below is why I decided to preempt it now to prevent the intake valves from fouling.

https://acurazine.com/forums/3g-rdx-...-974408/page3/
https://www.driveaccord.net/threads/.../#post-6739889

Haven't looked too deep into the PCV system on the K20s to see if the breather side needs it as well though.
Oh that German brake fluid analyzer was just an image I found online of one, the one I was familiar with is the Speedi Bleed one, but looks like they don't manufacture it any more. Sadly most things have gone overseas/outsourced, probbly all made same factory but different sticker gets slapped on it. And in terms of calibration, just use water, and adjust according if the offset is different, add or subtract.

Hahaha, nice one, needed a good laugh.Thanks for also sharing cross reference information from S2000 brake system, good to know.


Stayed at a Holiday Inn Express last night, decided to brush off my old cobwebs from statics analysis and try to solve/estimate performance and results in the following below: Thanks for sharing the sample problem, helped me work through my units, as using imperial, I accidentally multiplied by 32.174 for gravity, forgetting lb force, not lb mass. And forgot to divide by 12 to get the units all in ft in the equations, units still bite me in the ass.


Note, the following assumptions on the table above:
-CG Height Assumed Half the Height of Vehicle
-Geometry of Pads/Discs All Estimated Not True
-Coefficient of Tire-Road Friction Was Set at 0.29


-Coefficient of Pad Friction Assumed Was 0.35 (From Above Sample Problem)
-Estimated Braking Torque Required By Using the Following FBD Below


In short despite Type S being heavier by ~300 lbs, running Brembos appears to reduce the brake pad pressure psi by half, combination of larger pad area and larger effective rotors. And the addition of 4 pistons, not only ensures a more uniform pressure field, but also reduces the required brake fluid pressure required to drive the pistons by nearly 5 times. No wonder they're standard for racing/sport applications, so not just a CDI factor.

BEAR-AvHistory

Am surprised all turbo cars do not have them as standard equipmen, t. Have had 6 turbos so far & every one of the barfed into the catchcans I installed. The cans seem to work well as I did not have any cokeing issues in the cylinders, my intake systems & intercooler did not show any oil residue.

Can't comment on breathers on that setup, would guess it would not be a good plan. This is my current setup with a pair of breathers one on each valve cover. There is no PVC system on the car.


This is the prior system also with no PVC system. The two hoses Y together at the rear of the engine, run to catch can mounted on the firewall that exhausts into

a draft tube.
Black hose plugged into the valve cover is the start of my original system feeding the catch can

Legend2TL

WOW!!!!, yes you did stay at a Holiday Inn Express last night indeed!!

Very impressive work you've done there. I did have one comment, you have the tire/road coefficient of friction (Cf)set at 0.29 which I presume you meant the static Cf . For dry smooth pavement being asphalt or concrete that would be low number, I'd use something like ~0.9 for dry would be in the proper range of static Cf.

Physics 101 Tire Friction

Great stuff you've done there, have to look at it some more!

FWIW, some of most important numbers to know are the differences between the static and dynamic Cf between tires and pavement.
One a dry road, if the tire exceeds the traction limit's the tire starts to slide (it is no longer "static with the pavement") so the Cf goes from static (~0.9) to dynamic (~0.7) so maybe not as great at braking but still the majority of traction in there.
However on a wet road the difference between the differences between the static (~0.7) and dynamic Cf (~0.3) is much greater which is where ABS, SCS and other electronic aids are so helpful to regain traction. Which is why it's best to drive at much below the tire's limits in the wet, I know I don't have Senna-like skills in the wet. Our poor daughters had to endure car tire physics lesson from their engineer parents

http://hyperphysics.phy-astr.gsu.edu.../frictire.html

BEAR-AvHistory

What would you need to run the numbers on a 4000lb car with Front 6 piston, two piece 15" disc, P275/35YR19 & Rear 1 piston. two piece 14.6" disc, P285/30YR20, weight distribution 51/49

Tires are high performance summer Michelin tires, driver select AWD or RWD, driver select Integrated Brake system (sport/comfort) tested stopping distance 70-0 146ft.

Would this gain much upgrading to a 4 piston rear caliper?

praecisiovectura

Off the top of my head, should reduce nominal hydraulic required pressure by another half, yup, as suspected. Last row below once I had a chance to estimated your pad area based on on linear scale from Type S Brembos.


All things being equal, you could expect the same reduction in nominal brake sizing requirements from rear upgrades from stock brakes too just based on the numbers.

You're correct, the illustration of static and dynamic coefficients of friction was illuminating, as I hadn't wrapped my head on the transition between the two conditions and all the detailed variables involved. Running with a fiction coefficient of near 1 as you suggested would be prudent for the engineer, for tire to road contact, would be most conservative and presume this is what the automotive engineers do size with. Whereas running with a lower coefficient at brake pads would assume more brake torque is required, assuming no losses/knock down factiors, curious to know what the industry standard practices are for sizing and safety factors involved.

Anyway, to help save some time, for you, or other technical majors and nerds that like to geek out, here's the equations that were used in the charts above:


You've got to solve for estimated brake torque required first to size the brake system, since I didn't know what the moment of inertia and angular velocity of the wheels were I just ignored wheel torque. This was all to get in the ball park any way, as I only working with estimates for the brake geometry. And, since I didn't have the centroid geometry for vehicle weight, I used the weight distribution ratio to extract the span wise differences for a and b legs respectively, everything else breaks down pretty intuitively after that. Interesting rabbit hole to go down for sure - the more you know, as I never really gave much thoughts on brakes nor the physics/kinematics involved.