SRAM launch new powerful Maven brakes

[dave303e]

2 hours ago, michaelbiker said:

Forgive me if this is a stupid question but why don’t we need to replace the oil in our car brakes every year like it’s recommended on DOT oil bicycle brakes? Is this a requirement on motorcycles too?

 

Wall mounts, sketchy travelling, working on the bike upside down, often the brakes get bumped and the air in reservoir goes into the system. Cars also are not weight weenie-ing to the max so the seals and build is often a lot stronger, with power assist brakes as well the seals can stick a lot more, but with a bicycle your hand must actuate that piston so they can't get too much of a tight fit/seal. 
Ford ranger service schedule says new brake fluid every 2 years.

[Shebeen]

On 2/23/2024 at 2:36 PM, dave303e said:

You ever lost half your breaking capacity 180km into a 400km national offroad motorcycle race on a 2t with relatively no engine braking available... I have, that is why I am particular about what goes into my brakes.

We squeezed 4 of our bikes into a van with all kit and camping gear to go to the race and when we arrived I realised my brakes were super spongey. Could only get DOT3 brake fluid at the local town nearest the race and because we were so tight on space no one brought any. That fluid boiled after a few hours and it was a super fun day out for the rest of the day.

So I have my reasons, it is not a fun lesson to learn the hard way.

surely the braking forces on a motorbike are way increased over a mtb? We don't compare chain issues between motorbikes and mtb, so why braking? nothing wrong being overly cautious but i reckon mtb specific sceanrios would be a lot more relevant.

 

[question for the experts - @DieselnDust] Also, to boil something takes a lot of energy so it's one thing getting to boiling point but another issue going past it. Even then my physics brain tells me the brake hose should then become pressurised and the calipers should bite - why do they become squishy?

 

 

[DieselnDust]

10 minutes ago, Shebeen said:

surely the braking forces on a motorbike are way increased over a mtb? We don't compare chain issues between motorbikes and mtb, so why braking? nothing wrong being overly cautious but i reckon mtb specific sceanrios would be a lot more relevant.

 

[question for the experts - @DieselnDust] Also, to boil something takes a lot of energy so it's one thing getting to boiling point but another issue going past it. Even then my physics brain tells me the brake hose should then become pressurised and the calipers should bite - why do they become squishy?

 

 

Great question!!

In mineral oil, water has to be entrained in the oil. These oils have an affinity to absorb water but when heated will release that water more easily than a glycol (DoT oils)

Boiling point is not so much the issue but rather bulk modulus. We refer to boiling point because there a correlation to bulk modulus. Liquids are generally considered as incompressible right…,

but that’s at room temperature. Get a liquid close to its boiling point its bulk modulus changes and it can then be compressed. When it boils it’s a gas and gas bubbles are compressible. 

so we accept that hydraulic oils absorb water. In many large hydraulic systems we fill fit filters and coalesces to know the dirt and water out to very low parts per million levels. There’s no such luxury in a vehicles braking system so we need an expansion chamber to allow for fluid expansion at temperature and also an oil that can hold onto water molecules so that they behave as fishery have a higher boiling point. To do this the water molecules have to be separated from each other and bonded to the oil or something in the oil. Glycols do this quite effectively which is why they are used in brake fluids in all machines. Mineral oils have limited capacity to do this because it’s achieved through a small dose of emulsifying additives. Can’t have to much because water emulsions have bulk modulus problems ( will need a big expansion chamber). 
 

so to answer why does the lever feel squishy?

Generally this won’t happen during braking. A hit brake will often suffer face due to either pad material overheating and friction reducing, or due to fluid boiling and gas bubbles compressing because of excess water in the oil. Even at small quantities, water that isn’t bound to the emulsion additive in mineral oils will boil due to pressure and temperature from the braking and pressure. Remember under pressure the water won’t boil at 100C, it will boil at a higher temperature but this is still lower than the surrounding oil or glycol.

[Shebeen]

21 minutes ago, DieselnDust said:

Great question!!

In mineral oil, water has to be entrained in the oil. These oils have an affinity to absorb water but when heated will release that water more easily than a glycol (DoT oils)

Boiling point is not so much the issue but rather bulk modulus. We refer to boiling point because there a correlation to bulk modulus. Liquids are generally considered as incompressible right…,

but that’s at room temperature. Get a liquid close to its boiling point its bulk modulus changes and it can then be compressed. When it boils it’s a gas and gas bubbles are compressible. 

so we accept that hydraulic oils absorb water. In many large hydraulic systems we fill fit filters and coalesces to know the dirt and water out to very low parts per million levels. There’s no such luxury in a vehicles braking system so we need an expansion chamber to allow for fluid expansion at temperature and also an oil that can hold onto water molecules so that they behave as fishery have a higher boiling point. To do this the water molecules have to be separated from each other and bonded to the oil or something in the oil. Glycols do this quite effectively which is why they are used in brake fluids in all machines. Mineral oils have limited capacity to do this because it’s achieved through a small dose of emulsifying additives. Can’t have to much because water emulsions have bulk modulus problems ( will need a big expansion chamber). 
 

so to answer why does the lever feel squishy?

Generally this won’t happen during braking. A hit brake will often suffer face due to either pad material overheating and friction reducing, or due to fluid boiling and gas bubbles compressing because of excess water in the oil. Even at small quantities, water that isn’t bound to the emulsion additive in mineral oils will boil due to pressure and temperature from the braking and pressure. Remember under pressure the water won’t boil at 100C, it will boil at a higher temperature but this is still lower than the surrounding oil or glycol.

[The Ouzo]

3 hours ago, hansolo said:

Loving how we are going round in circles "inventing" new stuff to end up basically where we started...

Pretty soon SRAM will be touting new "less powerfull" brakes to make you go faster or a new standard to mount these stronger brakes to your bike. 

Hoping I don't sound like a Luddite but I really think we could do with better lower end components for the masses rather than just making more and more expensive components.  

developing high end tech generally eventually means the technology trickles down to the lower end.

Think about cars, tech we have as standard in lower end cars now was high tech stuff reserved for top end models only in the past. 

Think groupsets, Shimano 105 today has tech from Dura-Ace and ultegra of a few years back.

Thats generally how the normal R&D works.

[Headshot]

I am not a fan of the look of the latest flat facing SRAM levers and these don't disappoint. They do seem to be very effective brakes though...

[DieselnDust]

SRAM brakes developed due to leaps and bounds of the erratically funcytioning taper bore brakes of the mid to  late 2000’s. 
Once they stopped trying to reinvent the wheel (stopper) their brakes actually worked very very well. I still have Guides with revised lever internals that are strong and reliable 

[MORNE]

https://www.summitbikes.co.za/index.php?id_product=1740&controller=product
 

grab em while they are hot. Garenteed to be the cheapest set you’ll find in store😅

Quite a substantial set of things though. If you consider the rotors around 1k each and you get 4 in the box, including adaptors etc, i guess the price isn't too hectic. At least not Dominic’s. You’ll pay 5k more at other stores soon lol.  Pitty it’s the pikey red though.

 

Edited February 27 by MORNE

[BaGearA]

55 minutes ago, MORNE said:

https://www.summitbikes.co.za/index.php?id_product=1740&controller=product
 

grab em while they are hot. Garenteed to be the cheapest set you’ll find in store😅

Quite a substantial set of things though. If you consider the rotors around 1k each and you get 4 in the box, including adaptors etc, i guess the price isn't too hectic. At least not Dominic’s. You’ll pay 5k more at other stores soon lol.  Pitty it’s the pikey red though.

 

Brakes , rotors ( incl options ) , adapters + Bleed kit 

 

Seems like a freaking bargain to me