Let’s talk extended / stainless braided brake lines real quick

Just installed HS's rear extended lines a few weeks back and also confirm they're Crown brand. Crown's website offers different lengths and colors if you're wanting to change things up.

 

Elaborate, please.

 

This ^^^^

https://www.crownperformance.com/2005-2017-tacoma/

 

@DG92071

Bumping this up. I still maintain that my original statements are correct, so I'm curious to you hear your input on this subject—for my own edification at the very least.

 

I have to agree with DG and it seems they're choosing not to involve themselves but I'll play and offer my layman's explanation.

Let's say for instance you have a very heavy but rather delicate tube that you're holding between two fingers, now take that tube and give it momentum, if you try and stop it with just those same two fingers it was balanced in when stationary you may only be able to stop it now by grabbing harder to slow the momentum but you will crush the tube, crushing the tube is akin to locking up the brakes you can still lock up the brakes but you are passing the safe point by only having that limited bit of contact, now wrap all four fingers and your thumb around the tube and you can stop it with less pressure and without crushing the tube by having more contact area; with larger brakes you have more contact area and are widening your threshold of braking power.

Locking the brakes up is exceeding the threshold of the tires stopping ability whereas larger brakes gives you a larger threshold gor more forceful breaking without exceeding the tires traction ability so it does increase stopping power up to that point.

However once the tires traction have been exceeded, and the tires are locked up, it doesn't make much of a difference how big your brakes are; it has been proven that a braking tire provides more resistance against the surface than a sliding tire, larger brakes can handle that resistance without having to build enough pressure that would force that wheel to lock up.

Ultimately it is a hydraulic system you're looking at pressure and effective resistance, larger brakes gives you more resistance at the same pressure and thus a larger window of effective friction before the break point.

 

Hold on, this is a long one…


This is where I disagree on some points. There are two extremes for the state of the motion of the rotor in this scenario: 1) the rotor is freely rotating, 2) the rotor is prevented from rotating.

In case 1, no clamping force is applied by the caliper pistons to the rotor. In case 2, sufficient clamping force is applied to prevent rotation. If a specific braking system is able to achieve the states of both case 1 and case 2 at a given speed for a given vehicle, then it is capable of achieving any state between case 1 and case 2 because it is a continuous system, and cases 1 and 2 represent the extremes.

The stock braking system on our trucks is capable of achieving both extremes and is therefore capable of achieving any state between those extremes. In other words, the stock braking system is capable of delivering sufficient clamping force to the rotors to provide enough braking “power” throughout the range of cases between case 1 and case 2.

While I concur that locking up the tires isn’t optimal for slowing down a vehicle—the static coefficient of friction is typically higher than the kinetic coefficient of friction for most surface interactions, including rubber on concrete/asphalt/etc. (although there are exceptions, e.g. PTFE on PTFE)—that is largely a function of the specific tire compound and the surface the tire is riding. It’s a very complex interaction that, like many real-world applications, isn’t described very well by the simple friction formula we all learned in physics class in school (F=μN)—luckily we can ignore this interaction for this discussion because it’s not particularly relevant. All we care about is: can a particular braking system achieve the extremes of cases 1 and 2? And for any modern car’s braking system, the answer will almost always be “yes”.

There are several ways to increase the maximum moment (torque) that a braking system could theoretically apply to the rotor/wheel system: change the pad and/or rotor material to increase the coefficient of friction between the pad and the rotor, change the length of the moment arm where the clamping force is being applied (moving the applied clamping force further away from the axis of rotation, i.e. bigger rotors), or increase the clamping force itself through an increase the hydraulic pressure in the brake fluid circuit by increasing the input load or changing the size of the pistons at the BMC and/or at the calipers.

For the last option, changing the input load simply means pushing harder with your foot (or changing the pedal-to-BMC system to gain greater mechanical advantage for a given input force). Reducing the total effective area of the BMC piston or increasing the total effective area of the caliper piston(s) (note that we are talking about the total effective area that the fluid sees, not the area of the piston external to the fluid circuit) will also increase pressure in the system (although there are mechanical limits for real-world applications for the system to remain practical).

When people upgrade their braking systems, they are typically changing one of those three things: better pads, bigger rotors, and/or bigger calipers with more total effective piston area. But is this really increasing maximum stopping power if the stock system can already achieve the states of both cases 1 and 2? The answer is no.

So why do people upgrade these things in the first place if the stock system can already achieve the states of both cases 1 and 2? Well, there are plenty of good reasons to do so, such as increasing the thermal mass and heat dissipation to reduce brake fade or improving pedal feel by requiring less input force to achieve the same braking moment. In real-world applications, this can definitely improve braking performance—if you’re towing downhill and brake fade becomes so extreme that you can no longer apply enough of a braking moment to slow down the rotors/vehicle sufficiently, you will certainly have a problem. These are valid considerations and upgrading the braking system can improve overall performance in the real world, but again, it doesn’t increase maximum braking “power” when compared to the stock system—both systems are capable of achieving the states described in cases 1 and 2 and therefore every state in between cases 1 and 2 as well.

This gives us some context to discuss the specific topic at hand, braided stainless steel brake lines and my assertion that upgrading to braided stainless steel brake lines won’t improve braking performance by a measurable amount, if at all, and that tire choice, suspension geometry, and weight distribution (and overall weight) has a far greater effect on ultimate stopping power.

The first thing that we have to understand is that everything is a spring—and I mean everything. All parts of the circuit that see fluid pressure will deform as the pressure changes: the BMC, the lines, the caliper, the pistons, etc. No material is infinitely stiff, so any real-world object must be treated as a spring unless you can make the determination that the strain for that object is negligible in a given system for your desired set of loading conditions. When the pressure increases in the braking circuit, the primary stress generated in the brake lines is hoop stress. This hoop stress necessarily induces strain which means that the brake lines expand because they are springs (i.e. not infinitely stiff). We care about this because if the strain is large enough, it can cause a significant amount of energy to be “wasted” because it’s being expended to increase the volume of the fluid circuit by expanding the lines (this is similar to having air bubbles in your brake circuit—the fluid is expending energy to compress the air bubbles, instead of being spent to move the caliper pistons).

For the solid steel lines, this expansion is so small it can be considered negligible. We can do some top-level back-of-the-envelope calculations to see that this is the case. If make a conservative assumption that the maximum pressure inside the brake fluid circuit is 1,500 psi (~0.01 GPa), the hoop stress (using thin-wall assumptions) in the lines is 9 ksi (~0.06 GPa). If we assume that our solid brake lines are regular carbon steel (Young’s modulus ~200 GPa) with a ~1/4" OD and 20 thou wall thickness (a good approximation for our stock hard lines coming from the BMC), this results in a strain of 0.0003 m/m, meaning that the mean diameter of the brake line expands by only 7 hundred thousandths of an inch (0.00007”, or ~0.03%). I would call that fairly negligible.

I don’t know the effective Young’s modulus for Nylon-braided rubber (it depends heavily on the type and amount of Nylon and how it’s braided in the rubber) or the exact size of the rubber lines in our trucks (I tossed mine when I upgraded), but we would expect the strain to likely be much higher. For reference, the Young’s modulus of plain silicon rubber for small deformations is on the order of 0.01 to 0.1 GPa, compared to plain carbon steel at ~200 GPa. That being said, Nylon-braided rubber, as is used in many brake lines, resists strain far better than plain rubber.

So the real question is, how much do our stock rubber brake lines expand (or really, how much does this expansion contribute to a change in the total volume of the entire brake circuit) when the brake circuit is at maximum pressure? I’m willing to bet that it’s not much—the engineers at Toyota knew what they were doing when they designed our brake systems. Upgrading to stainless steel braided lines will likely decrease the amount of expansion a small amount, but it’s safe to say that it’s marginal.



TL,DR: Stainless steel braided brake typically won’t improve braking performance and should really only be done if you want to improve durability and/or you want longer lines. This video below does an OK job at summarizing the topic.

Also, if anyone has any other info or analysis that comes to a different conclusion, feel free to share it or poke holes in any of my calculations/assumptions/etc.—new/better info (especially real-world data!) is always welcome.

https://www.youtube.com/watch?v=6LJiPDAr9f8

 

I've not really heard of braided lines increasing the maximum overall power of a system...but they can help keep the brakes at a higher power level with respect to temperature vs stock lines, i.e. they don't fade as quickly.

I've done track days on the same motorcycle with and without braided brakes lines (same bike/rider/gear/roughly the same ambient temperature) and they absolutely do make a difference with brake feel/fade with repeated frequent hard uses and the system is operating at a high temperature. I'm sure the difference is negligible when the brake system isn't heated up from repeated hard use (e.g. normal street driving.)

This performance difference is even more apparent on systems that get used hard and have a small amount of mass/fluid/cooling capability such as downhill mountain bikes....although I've only run braided lines a few times in this case as I found that, depending on the brake model or manufacturer, braided lines sometimes negatively affected the brake feel overall (like trading brake modulation for sheer power.) Of course that is a personal thing as not everyone sets up their bike the same way. That and disc brakes on bikes are usually way more fiddly to work with than car/truck brakes.

Besides speed, vehicle weight is other thing that can cause the brake system temperature to rise faster on a modified vehicle than on a stock one. Whether it's 35" E-rated tires on beadlocks with more rotating mass or steel bumpers and armor, many people on this forum have added significant weight to their trucks with their mods. A heavy vehicle that is working the brakes hard will see the brake temps rise faster even at lower speeds than a lighter weight vehicle using the brakes in a similar manner (think a fully loaded/armored Taco pulling a trailer down a mountain road vs a bone stock rig on the same road.)

I'm also sure there is a point where a larger/wider/heavier wheel/tire combo can exceed the braking capability for a stock brake system (larger mass plus longer moment arm along with larger contact patch.) I used to have a Jeep Cherokee that we threw some 33s on. On the first shakedown drive it was clear that the stock brake system was definitely not up to the task even at moderate street speeds



TL,DR: while rubber lines are probably fine for a non-modified Tacoma that is used within the driving parameters that Toyota's engineers (and bean-counters) envisioned it being used (let's be honest here: mall crawling with occasional trips to Hope Depot and the ski resort). If you've increased the weight of the truck and/or you drive it hard and you want to squeeze every last little bit of performance out of your braking system then braided braked lines may be for you

 

I'm not interested in having the debate. The proof of my opinion is everywhere where brakes are used. Thank you for your understanding have a great day.

 

All good! I believe that you are incorrect in this instance and feel that I have provided enough background/support to show why—but I respect your choice. If you change your mind, input is always welcome! I hope you have a good day as well.

 

Do you have a hypothesis as to why brake feel/fade felt different on your bike (i.e. the reason behind why you felt less fade under heavy braking conditions when using braided stainless steel lines)? I don't see why braided stainless steel lines would have a significant difference in thermal resistivity between the fluid and the air compared to stock Nylon reinforced rubber lines (with the exception of the stainless steel, which itself has relatively low thermal conductivity itself when compared to other common metals, the materials used in both stainless steel braided lines and stock lines don't have great thermal conductivity)—and even if they did, the surface area is so small (as is the volume of fluid in that section of the system) that I'd imagine the cooling effect to be marginal.

Unless the stock lines were damaged or worn to the point where the expansion of the stock rubber lines could no longer be considered insignificant, I'm curious where this perceived improvement in performance is coming from.

Do you have any data? Regardless, I do appreciate the anecdotal evidence and input.

There's no doubt that upgrading other brake components can help with things like brake fade and feel. That being said, I maintain that if a stock braking system can achieve the states of both cases 1 and 2, then upgrading parts of the braking system will not improve ultimate braking power (although it can allow the system to maintain performance better over time during periods moderate to heavy use).

 

I believe that as the brake system heats up the components will expand. The more heat that is put into the system the more the brake hose will want to expand. This will put the reinforcement in the brake hose (nylon in the rubber hose and braided steel in the SS/teflon lines under increasing tension as the hose thermally expands. Obviously the exact dimensions and material makeup of the nylon/SS wires in the braid is going to vary by manufacturer...but I would expect SS to have a tensile strength in the order of magnitude roughly 5-10 times higher than nylon. The distance of the reinforcement from the c/l of the hose will also factor into this.

The brake lines on my motorcycle were OEM and only about 2 years old. I did not notice any damage or deterioration in them. The brake fluid in the system was only a couple of months old with average street riding and some weekend canyon trips. When I did my first track day I definitely noticed brake fade as the sessions went on. I changed lines before the next track day 2 weeks later. Obviously I needed to add fresh fluid and bleed the system. Everything else about the bike (brake system, tires, etc) was the same.

The only data I have was lap times: they were much improved during the second track day. The delta between beginning of session and end of session laps also went down with the braided brake lines. Exactly how much of this was due to the brake lines vs track familiarity I cannot say...but I was much more confident in the hard braking sections without my brakes losing power as they were working at elevated temperatures.

Braided brake lines are not about ultimate braking power; they're about maintaining peak power for as long as possible as a given braking system is put under hard, repeated use where the system doesn't have a chance to cool down. I'm pretty sure that if you look at most racing series that don't just go in a circle (F1, MotoGP, Superbike WC, Le Mans, WRC) they use some form of brake lines above and beyond nylon-reinforced rubber.

 

https://sdhqoffroad.com/products/05-current-toyota-tacoma-sdhq-built-brake-line-kit

SDHQ has a kit 3/4” front and +2” rear. Looks like their heat shrink has a crown logo too.