Nerding out on Brakes shall we? Not another tech deraliment

I have no idea really. My guess is that it will depend on how much of a vacuum is pulled how quickly and what the surface area is. The problem would seem to be how one knows what the % of dissolved gas in a fluid actually is. A little electrical probe you just dip in the fluid like a thermometer that just gave a magic reading would be really nice. But for the home shop I think you'd have to work by volume reduction comparisons?

My intuition is that sticking your finger over the end of a syringe and pulling bubbles out for 10-30 seconds is not a useful approach. But I'm probably biased against the degassing crew as per my previous comments.

A possibly useful example to look at is people who degas epoxy and silicone resins when pouring molds and the like. It seems like the time it takes to pump down the vacuum chamber + a few minutes sitting at vacuum will do the job in most cases for what's required in that field.

Here's an experimental procedure to learn more.

Start 2 fluid samples, say 100ml each. Vacuum sample A for as willing long as you are willing to, say 12 hours, and note it's volume after the test. Then vacuum sample B for some minimal value you hope will be effective and compare the results. Hopefully the volume differentials in the fluid you're testing are large/measurable.

You could then take the samples and put them in pressure vs displacement testing device and measure the compressibility difference between the samples. I've got a spring rate tester that could test at reasonable pressures and measure displacement. Getting the correct volumes in the tester and making sure you transfer them in an air bubble free way would probably be a large part of the challenge.

Even neglecting the degassing, simply testing the compressibility of the various brake fluids might be a useful endevour (maybe not, but I can't find any literature out there that points in one way or the other). Get a bunch of brake fluid bottles, open them to atmosphere (in case some one is fancy and shipping with nitrogen topped up bottles or something, doubt it...), give them time to rest, recap, shake them up like you're on the worlds bumpiest fedex route for 48 hours to get as much air in the gas as possible, to simulate what might be a real world usage scenario, then test the compressibility of bionol vs shimano fluid vs magura etc.

I'm not sure why people looking at brake fluid specs care about the specs we're provided (for normal riding, not cooking the absolute hell out of your brakes for hours at a time in some sort of infinite downhill fantasy that some people seem to live in.)

-Viscosity/Viscosity index? Seems silly, you've got huge leverage over the fluid via the mechanical advantage of the system, you could be pumping chunky peanut butter through the lines and not know it. Exceptions for this might be if you're riding around below -10c and are concerned about freezing. But you can't reliably infer -10c/-20c/-30c behavior from the 40c and 100c and viscosity index numbers that are normally provided by the manfuacturer. Props to manufacturers that provide the pour point.

-Boiling point? Silly again. Is anyone really getting their pads and rotors well into the "crazy hot" range, then getting fluid boiling point related fade and thinking the fix is purely just to change oil? The fix is better cooling, different pad contact area, pad materials, rotor size, technique, all ahead of fluid boiling point. Would I run with a boiling point of 50c or 100c? Probably not. But I wouldn't make that my #1 stat to look at if there were other stats out there that would affect you my brakes feel when I pull them normally 99.9% of the time (fluid compressibility, additives that might help with bite point wander, a good bulk modulus vs temperature curve, a fluid that creates more consistent seal rollback, a fluid that doesn't kill pet birds, whatever).

Another question I have about fluid boiling. If your fluid boils at 300c, but your EPDM/Viton seal life reduces drastically whenever they're hot (https://www.o-ring-prueflabor.de/files/02_expert_knowledge-thermal_over…) and caliper manufacturers for cars say a caliper temperature over 250c means replacing the seals (https://www.ebcbrakes.com/race-motorsport-articles/know-your-stuff-tech… ) (https://www.rogueengineering.com/Brembo-Caliper-Temperature-Sticker-Pai…) ... Do you care? If you're not winning a DH world cup and care about the longevity and usability of your brakes in most normal riding scenarios fluid boiling point seems like something you shouldn't care about at all as long as it's above some baseline like 150-200c. Maybe the 300c stuff will save you if you're being chased by ninjas.

That might be the same thing that we were talking about on the Hayes/Mondraker bike some posts earlier.

It allows the seals to reset with the pistons in the correct place. Almost the same thing as removing the rear wheel and pushing them a little out. Only easier and less tricky.

Would love to hear how they feel now and if that completely fixed the problem.

Hayes is having a 20% off sale, so I'm getting Dominions. Was going to order from their site, but my LBS price matched, so stoked about that (don't have to deal with shipping, duty, etc). Once I have a bit of time on them, I'll make sure to do a good review for all the clydes out there. Ha ha

Has anyone been able to set up Hope V4s to not squeak? Thanks to y’all’s tips mine are now feeling great with the pistons aligned and contacting the rotor at the same time, but they always chirp right when the pads engage. Maybe still not aligned?

This might be a pad material to rotor issue not your setup.

So what brakes have the least amount of lever throw? Saints?

Radic, then Intend

I'd say Maven and Saint are similar amounts of deadstroke but power ramps up faster on Mavens, so you get more power for a shorter distance. 

Huh, using stock Hope green pads and Hope rotors, but maybe the pads are glazed.

Welcome to hope. honestly, go watch any Hope sponsored athlete, all the t4v4 brakes squeal. 
aston also said its normal.
 

Same here, I'm running them with Galfer standard black pads and Trp 2.3mm rotors and they squeal a lot. I don't really find that annoying, I'm sure it's worse for other people around me

Change of plans. Went into the shop to get Domain's, but they had a set of Lewis (yes, the sort of Trickstuff knockoffs) brakes, so I'm going to give them a try. My shop brought them in because they were curious, but wanted someone who can put them through their paces. I'm 6'4 and 120kg and a half decent rider. Will definitely be able to give them a decent go and give some good feedback, good or bad. If they're no good, we'll swap them out for Domains. 

For better or worse, I honestly don't care where they were made, if they look like another brake that's already out there. They didn't infringe on any IP, have (apparently) different internals and have improved some things on the levers. All I care about is whether they work and that's what I want to find out. 

It's for science. Lol

We're going to go ride Dead Dog on Mt.7 next weekend and I can think of a better track to test brakes on than the upcoming Psychosis DH course. IYKYK. Ha ha ha. 

Final thoughts on the Cura 4 w/ Trickstuff Power pads and FCS levers. 

The bleed/install was generally easy, no hose twisting or other issues, it all bled very smoothly. The FCS install wasn't hard but finding the right snap ring pliers was a bit tricky for me because the snap ring is so small, tbh I'm not sure why you couldn't just use the already installed plunger/washer/seal, but I followed the instructions still. The lever is slightly smaller and the contact adjuster appears to move a cam fore/aft on the lever to change progression of the lever. It's a subtle difference but you can notice it. Lever reach adjuster works the same. 

The lever uses a bushing and there is some up/down play in it. It's not enough to drive me nuts but over time I can imagine it wearing and flopping around more (the NSMB review commented on this as well), I wish they'd use bearings here, I know it adds weight and complexity but damn bushings are annoying when they wear and the lever flop is just blah in 2024. Pads install easy from the top down. 

I did notice the lever was a bit mushy despite bleeding several times, I zip tied the lever to the bar for a few hours then it seemed to firm up. I have no idea why. My suspicion is it has to do with pistons the same way you have to do a similar process to align the Mavens, but idk. I had no issues with sticky pistons but I also worked them in and out several times and I didn't keep them on long enough to really induce that kind of problem. Paul Aston claims this is a common issue with the 4s, but I also hear there is a running change that may have fixed it.

The power is....there, it just takes a while. If you like long lever throws, these are probably a good option. The power comes on late in the lever stroke even with the FCS adjusted in, power just comes on really slow compared to Intend, Maven, Maxima, Hope T4 V4. It may be ok for lighter riders or people who like that feel, but it was too slow for me. It does ramp up progressively by the time you reach that point, though, and it's easy to modulate. 

Personally they feel like a previous generation brake. The power comes on late and requires a fair bit of hand strength to reach. It's not excessive but it is fatiguing compared to brakes that drop power much sooner in the stroke. For lighter riders these might work fine but they didn't really pan out for me. I think they are in the right ballpark but need refinement to match more modern options. 

220lb rider on a Geometron G1 with 2.3 203mm Formula CL rotors. I'd choose them over Shimano, possibly Magura, and Codes. Not over boutique brands like Intend, Radic or Trickstuff and def not over Hope for heavier riders. If you like short lever throws they are definitely out. If you are lighter and want power to come on more gradually, they are a good choice, I feel the lever has a better feel than Shimano or Magura, possibly Hayes aside from the slight lever play up/down.

Which Lewis variant? 

Trying the LH4. 

Were they at the insideline by chance? because I saw them there. Mt 7 would be the perfect place to test any brake. That's what made me upgrade my Codes.

I just finished installing the Dominions on a friend's bike just now and found the installation pretty easy. Fit and finish leaves a lot to be desired though. 

Read a few people in this thread rave about galfer green and purple pads. Curious if anyone have experience with those and trickstuff pads and could compare.

Absolutely they were/are. Cam and I had a good chat about them last night and figured it would be a good chance to test them out. I'm not sure I'd be willing to order them and try them out that way, but having a shop in on the experiment helps a whole bunch. Ha ha

Recently bought some Dominions and have a theory about all the excessive lever throw/dodgy bleeds that some people experience.

It seems all the non-oem bleed kits come with SRAM fittings i.e. an m5x0.8 threaded fitting with an elastomers on the end. When bleeding my dominions the first time, I tried fittings like this but they leaked fluid under pressure and pulled lots of air in under vacuum.

The reason for this is there's no spotface on the bleed port for the o ring to actually seal against so it just extrudes itself off of the lip if you thread the fitting in further.

If you look at the bleed port plug fitting that comes with the brakes, it uses a metal to metal seal on what looks like a 45deg taper:Sure enough it looks like the Hayes pro kit comes with fittings with a taper/cone and no o rings.

In the UK you can't buy these fittings on their own, you have to spend £75 on the "pro" bleed kit to get them. Because I'm a tightarse I simply refuse to do this so I modelled some up in cad (without the threads), 3d printed a few and cut a thread on the end with an m5x0.8 die.

I didn't expect them to work but they work beautifully and I got a really thorough leak-free bleed of the lever, lines and caliper and pulled out an an insane amount of air from the prior dodgy bleeds. The result is exceptionally short lever throw and a totally consistent bite point which satisfies me greatly. I used the old sram bleed method to achieve this e.g.

-degass syringes, bleed lines, hold lever pulled with rubber band and close lever syringe, vacuum bleed caliper, push fluid back through to lever and disconnect caliper syringe then finally vacuum bleed the lever.

If anyone would like the CAD file I can upload it when I'm next at my laptop, you obviously need a die to cut the thread too but these aren't expensive.

Because they're plastic and threaded I don't expect them to last very long so I've started turning some out of brass on the lathe for something more robust, just need to finish the barb profile on the right hand side and cut the thread on the left:

I've tried power+ and galfer green. It's been some time now and I didn't use them back-to-back, but there were clear differences. Power+ seemed like singularly focussed, dry condition, race pads. I made the mistake of installing them one January and aside from hardly working when wet, they lasted something like 10 hours. You might get more life out of them if it's not muddy.
The greens were a lot more versatile: they felt similarly crisp when dry, but instead of being useless when wet, they were quick to regain power. They lasted way longer (still nowhere near a metallic pad, but good enough). Of the two, the Galfers would be my obvious choice to buy again.

100% on the tapered bleed fitting tip.  About a year ago there was a PB interview with one of the Hayes guys, and he said as much in other words.  He specifically recommends taking a pair of Knipex and giving the fittings a little bit of extra torque to make sure the bleed fitting tip bottoms out in the bleed port.  As soon as I started doing that, my bleeds got way more consistent and stopped getting that infuriating trickle of bubbles when I did vacuum bleeds.

Any opinions on MTX Gold pads and Galfer Purple for bike park?

Great tip - all I would say is to be careful putting too much torque into them as I've seen people ruin high pressure conical hydraulic fittings by continuously overtightening them over time and damaging the sealing faces

I'm back to hate on my Hayes Dominions some more. Did a full caliper and lever bleed as per the manual, cleaned and lubed the pistons, fitted new pads and got them perfectly aligned. Right after bedding them in, the lever throw is roughly the same as my trail bike's Codes.

After just 2 days at Dyfi the dead throw is back to a massive 35mm of travel before bite (measured from grip to lever tip). This also means I can pull the lever all the way to the grip if I squeeze hard, even though they rest at 65mm (again, grip to lever tip).

Front and rear are pretty much identical, power is good and the bite point is sharp so I can't believe it can be a bleeding issue at this point. Are these brakes just not capable of handling bike park levels of abuse? I'm about 185lbs kitted and running 223 rotors too, so it's not like I'm built like a tank and cooking them all day. Would appreciate any final suggestions before I give up.

I run galfer 2mm rotors 223 front 203 rear  with galfer green rear purple front no squeal..(galfer makes hopes pads)  Both DH bike and enduro no squealing.

See my post further up - are you using SRAM style fittings to bleed or Hayes ones that don't use an o-ring?

Your symptoms definitely sound like air in the system and were the same as mine when I was trying to use SRAM fittings to bleed them i.e. lever felt great right after bleeding and dead throw increased dramatically when I started riding.

Since getting a decent bleed I've found the lever throw dead stroke to be very similar to my old codes.

Shigura Mix.

IMO not ridable as of almost no modulation

As of strapping the lever over night etc.:

if you pull the lever, you open the reservoir / mastercylinder connection, close the mastercylinder/hose connection. let it sit like that, air bubbles will wander from the mastercylinder to the top of the reservoir and not sit in the mastercylinder anymore. hence air bubble should not get into the system mastercylinder/hose. this doesn't replace a propper bleed but could help itching the last percent out of a propperly bled brake.

dominion leverthrow: true, after around half the pad wear, i quickly vacuum bleed the system (1-4 pull/push on syringe with a super small amount of dot) and the brake feels as new. sure it's an extra step but i'd rather have a super crisp and constant lever feel than worring about those 3 min of work

tried the code, new code, hope tech 4 and dominions in the last year, stick with the dominions.

cool BTS story for the lewis "knock-off": DT Swiss bought trickstuff, engenier (or owner or whoever) wasn't all that happy, founded a new company, kept his design and improved it, released it as a new brake: Lewis.

wha't i've heard. No idea whether smoke, fire or bullshit

edit: one page later we're smarter, the rumor turns out to be bullshit!

Highly doubt it, first sets of what became Lewis brakes had to be bought on Taobao by someone in China and shipped over.

Edit: founders pictured below, I'd suspect Trickstuff founders are German, not Asian? https://www.lewisbike.com/about-us.html