8-piston gator brakes -

[HAL9000v2.0]

They have commercial that say "Deadly stopping power." so I must test that.
first some pictures after testing.

What happened? 150kg bike and me traveling some 20km/h. Front tyre is kenda flame 3" wide, not inflated enough so actual surface in contact with ground is some 80x60mm
I delibretly squized breake as hard as I can to test it and bike stopped in some 0,2m with rear wheel some 1m above the ground. ( piston calippers simpli grab disc where it touches it. The disc was strong enough for all other breakes I have tested before. This one is amaizing! I have some experience in big bikes but never saw calipers grab disc as strong as this. Original disc that comes it gold phosphatised and this one was hard steel.
Disc is broken, adapter is broken, 10 spokes are broken, fox haven't got a skratch, and saliper was good.
I will make 2,5 mm disc without holes to see next weak spot...

 

[neptronix]

It lives up to it's name.. the stopping power can kill you
I wonder if they make rotors and other brake equipment that can actually withstand the power, lol.

 

[j3tch1u]

hope tech v2 vented rotors perhaps?

btw, how is the modulation/feel on those brakes?

 

[Ypedal]

.. ouch !..

 

[MitchJi]

Hi,

btw, how is the modulation/feel on those brakes?

Equally important or maybe more important than the stopping power.

What size are the rotors?

How much did the brakes cost?

Build quality?

Mixed information:
http://forums.mtbr.com/showpost.php?p=2471626&postcount=4

They come from making motorcross brakes,ive tried some on motorcross bikes and they are solid,so should be good for mtb

the 4 piston version was tested by "mountainbike magazin" 5/06* and compared to ~20 other discbrakes.

quote/translation:

"Gatorbrake 4 Piston 170mm/150mm
180 Euros each wheel
weight 494/573g

Modulation: 1 out of 5 stars
Power: 2 of 5
Fading Resistance: 2 of 5
performance when wet: 3 of 5

"even after a long break-in period, the gatorbrake didn't develop satisfying power. After only a few hard stops, the brake's power fades away completely. Modulation is poor because of the super hard pressure point [is that a word?]"

rating: weaksauce

it got the worst rating of all the 20 something brakes in that test, by far.
for example, they gave the juicy five (6" rotors) 4, 3 , 3 and 5 stars, and even more with bigger rotors.

 

[brumbrum]

i think the idea that the more pistons you have the more powerful the brakes is a bit of an urban myth. With high performance car modification it is often used as a selling gimic, if the caliper is huge and has 8 pistons it must have awesome stopping power. I think it's more to do with the brake in the piston and not the pistons in the brake.

However, it seems in this case that much stronger rotors are needed, probably solid steel

 

[HAL9000v2.0]

After analiysing I think that this was combo of bad adapter/bad disc.
Same dics 225mm work great on my bike with Magura break. Adapter was also custom and it is made out of 440 steinless steel, same as disc, tempered ad 600°C and then brushed. smallest section was 4x6mm. So that is all fine. I simply underastimated the force.

The callipers are realy nicely made and looks good They have 4 pads, each pad with 2 cylinders. Price is somewhere in the bottom half of middle hydraulic brakes class. I like how they work, it remindes me on R6 dual front disc; you hold lever on the same position and you can feel how blakes bites more and more. For someone with no motocycle experience they can feel like switch, and that can be deadly. At the end, I like them. Also I have dual 8 piston calipers system. Can't wait to test those...

 

[HAL9000v2.0]

... it seems in this case that much stronger rotors are needed, probably solid steel

Or smaller diameter.

 

[brumbrum]

... it seems in this case that much stronger rotors are needed, probably solid steel

Or smaller diameter.

Understood. they do sound like amazing calipers

 

[Stevil_Knevil]

They have commercial that say "Deadly stopping power." so I must test that.

Holy fark!

Finally, truth in advertising

What diameter is the bore in the master cylinder?

 

[Accountant]

Modulation: 1 out of 5 stars
Power: 2 of 5
Fading Resistance: 2 of 5
performance when wet: 3 of 5

"even after a long break-in period, the gatorbrake didn't develop satisfying power. After only a few hard stops, the brake's power fades away completely. Modulation is poor because of the super hard pressure point [is that a word?]"

rating: weaksauce

it got the worst rating of all the 20 something brakes in that test, by far.
for example, they gave the juicy five (6" rotors) 4, 3 , 3 and 5 stars, and even more with bigger rotors.



This was all true, but 2-3 years ago, when they entered the market with one bad serries of products.

Unfortuntely everyone remembered this well, and it is no longer true.

Anyway we use 6 and 8 calipers version, and they work very nice.

Modulation is great, and we will continue to use them.

 

[Kepler]

Agreed, the 6 and 8s work very well. I did find my 8's needed a few weeks to bed in though. Now they have great power and modulation.

 

[Hillhater]

I dont know why we have 2 threads running on this but to repeat from the other thread...
Why would the disc be fitted this way to put the flimsey disc spokes in compression under braking ?
It would seem to be much stronger and safer if that disc had been fitted the other way round to keep the disc loaded in tension .

 

[mdd0127]

My Elixir rotors show that they need to be installed in a way that doesn't make sense to me. I accidentally had the front one on backwards for a long time and it seemed fine but I switched it back anyway. I think it actually felt better before and I might run the rotors backwards on the prototype bike unless I find a good reason why I shouldn't. I'm really considering cutting some custom rotors because the mtb stuff is a little flimsy sometimes.

 

[Alan B]

I dont know why we have 2 threads running on this but to repeat from the other thread...
Why would the disc be fitted this way to put the flimsey disc spokes in compression under braking ?
It would seem to be much stronger and safer if that disc had been fitted the other way round to keep the disc loaded in tension .

I wondered the same thing when I got my front disc brake. Looking around, pretty much all bike disc brakes are set up with the arms in the disc in compression. Steel strength in either tension or compression is not that different, but it seemed strange. I did some searching and the only thing I found thus far that was very informational was this:

...

Tech reply from Hayes in 2009:

The reason for the spoke design is that there are two sources of stresses in the rotor. The first is mechanical stresses due to torque and the second is thermal stresses within the rotor. As the braking surface heats up, it expands. The inner portion of the rotor near the hub is comparatively much cooler. With the outer braking surface expanding with higher temperature and the temperature of the center remaining largely unchanged a thermal stress is imparted on the spokes. The spoke design is specified such that the mechanical stresses and the thermal stresses occur in opposite orientations, attempting to cancel each other out and lowering the total stress in spokes as opposed to adding together. The result is the “sweeping forward” spoke pattern.

...

Looking at the bent parts, it would seem that the fork to brake adapter was not up to the stress of this braking event. A smaller rotor might be better as the adapter would not be as stressed. In any case a stronger adapter is indicated for this use.

 

[Hillhater]

. Steel strength in either tension or compression is not that different,

you may want to debate that with a structural engineer ! .
The metal strength is one factor, but the strength of the component design is completely different.
(EG:- would you want to see wheel spokes used in compression only ?)

. A smaller rotor might be better as the adapter would not be as stressed. .

Sorry,.... but i believe that the loading on the caliper mount & adaptor increases with the reduction in diameter of the rotor.
This is a torque arm effect, so the bigger the rotor, the less the torque reaction at the caliper.
(another advantage of rim brakes,.... minimum force loading on the braking components. !)

Tech reply from Hayes in 2009:

The reason for the spoke design is that there are two sources of stresses in the rotor. The first is mechanical stresses due to torque and the second is thermal stresses within the rotor. As the braking surface heats up, it expands. The inner portion of the rotor near the hub is comparatively much cooler. With the outer braking surface expanding with higher temperature and the temperature of the center remaining largely unchanged a thermal stress is imparted on the spokes. The spoke design is specified such that the mechanical stresses and the thermal stresses occur in opposite orientations, attempting to cancel each other out and lowering the total stress in spokes as opposed to adding together. The result is the “sweeping forward” spoke pattern.

That MAY be valid, ( the temp gradient is not that big ),.. but the thermal stress will be insignificant compared to the braking loads, and as i said above the mechanical design is far more important than actual material strength in compression.
If they were concerned about total stress levels, they would have simply made the "spokes" wider.

 

[dpearce]

i'm an idiot..

 

[Alan B]

. Steel strength in either tension or compression is not that different,

you may want to debate that with a structural engineer ! .
The metal strength is one factor, but the strength of the component design is completely different.
(EG:- would you want to see wheel spokes used in compression only ?)

. A smaller rotor might be better as the adapter would not be as stressed. .

Sorry,.... but i believe that the loading on the caliper mount & adaptor increases with the reduction in diameter of the rotor.
This is a torque arm effect, so the bigger the rotor, the less the torque reaction at the caliper.
(another advantage of rim brakes,.... minimum force loading on the braking components. !)

Tech reply from Hayes in 2009:

The reason for the spoke design is that there are two sources of stresses in the rotor. The first is mechanical stresses due to torque and the second is thermal stresses within the rotor. As the braking surface heats up, it expands. The inner portion of the rotor near the hub is comparatively much cooler. With the outer braking surface expanding with higher temperature and the temperature of the center remaining largely unchanged a thermal stress is imparted on the spokes. The spoke design is specified such that the mechanical stresses and the thermal stresses occur in opposite orientations, attempting to cancel each other out and lowering the total stress in spokes as opposed to adding together. The result is the “sweeping forward” spoke pattern.

That MAY be valid, ( the temp gradient is not that big ),.. but the thermal stress will be insignificant compared to the braking loads, and as i said above the mechanical design is far more important than actual material strength in compression.
If they were concerned about total stress levels, they would have simply made the "spokes" wider.

Hillhater, I am reporting what I have found in my research. I shared your initial observations regarding the configuration of bike discs but after looking around I find that very few are designed in tension, and some that were had problems that way so they changed to compression. If you find my research inadequate please do your own. I see many problems with your arguments but I'm not interested in a debate. Enjoy.

 

[Hillhater]

no problem Alan,..I have no wish for debate either, but i dont like to see inaccurate statements made.
As a professional Engineer, i have spent my life researching this kind of stuff.

 

[Alan B]

no problem Alan,..I have no wish for debate either, but i dont like to see inaccurate statements made.
As a professional Engineer, i have spent my life researching this kind of stuff.

Please let us know what you find in your further research on this. I have reviewed my earlier comments and find them to be accurate in my experience. There are many engineers on this board.

In an earlier comment it was mentioned that the original poster has not used the disc that was supplied by the manufacturer which was smaller diameter. I wonder if the mounting adapter was also a non-approved part. These changes may have caused or contributed to the failure.

Changing to a larger diameter rotor increases the caliper forces as they are the mathematical product of the friction coefficient (constant for a given caliper, hydraulic pressure and pad) and the velocity of the rotor surface. The larger rotor has a higher velocity, so the forces will be larger than the "standard" rotor. However this is equivalent to braking at higher speed so by itself should not be an issue.

But perhaps more importantly the stiffness of the support system is also changed...

The larger rotor also requires an adapter to move the caliper out to the new radius. This places the caliper further away from the lower support and potentially weakens the caliper support.

It appears that the caliper support failed, so these factors are critical to the issues:

Was this a high quality caliper adapter? Or a clone with possibly incorrect metallurgy or design??

Was this system operating within the manufacturer's design parameters?

Glad to hear the test pilot was not injured, by the way! (Other than in the wallet...)

 

[HAL9000v2.0]

You are both right. I'll say thet even better is when force is pushing the part BUT this is onla when force goes streight and here is not souch thing. Here is situation that I made bigger rotor (225mm) and, ofcourse, I had to make bigger adapter. The adapter was made out of steel and it was no weaker then any I did before,
The problem is that the adapter was to flexible and when I hit the brake, momentum was created (because mount is ofsetted from center of caliper) and caliper is twistd and shifted off the center of. As the disc "legs" was also designed on the edge of thin construction shift of more then 1,1 mm was enough to colapse the disc.

 

[Hillhater]

.....Changing to a larger diameter rotor increases the caliper forces as they are the mathematical product of the friction coefficient (constant for a given caliper, hydraulic pressure and pad) and the velocity of the rotor surface. The larger rotor has a higher velocity, so the forces will be larger than the "standard" rotor.

sorry again Alan, but that is fundamentally wrong !
The braking force is a Torque reaction around the wheel spindle, and the further from the spindle centre the calliper is..the less the force required to produce the same torque.
You went wrong in assuming the hydraulic pressure on the pads remained constant for different rotor diameters.

 

[Alan B]

.....Changing to a larger diameter rotor increases the caliper forces as they are the mathematical product of the friction coefficient (constant for a given caliper, hydraulic pressure and pad) and the velocity of the rotor surface. The larger rotor has a higher velocity, so the forces will be larger than the "standard" rotor.

sorry again Alan, but that is fundamentally wrong !
The braking force is a Torque reaction around the wheel spindle, and the further from the spindle centre the calliper is..the less the force required to produce the same torque.
You went wrong in assuming the hydraulic pressure on the pads remained constant for different rotor diameters.

The original poster stated that he "squeezed the brakes as hard as he could" in this test. So the mechanical force is constant based only on the operator's strength. The mechanical advantage of the brake lever is constant. And the hydraulic pressure is therefore a constant in this case. This is fundamental in the stated example in this thread (see post #1). This is NOT a case of equal braking torque. It is a case of panic stop maximum friction. In which case the larger the rotor, the greater the braking force.

Have a nice day,

 

[Ypedal]

and lets not forget the extra heavy bike, with fat low pressure tire giving max grip = taco !..

on a normal bicycle an " endo " would have resulted ! lol..

 

[Hillhater]

The original poster stated that he "squeezed the brakes as hard as he could" in this test. So the mechanical force is constant based only on the operator's strength. The mechanical advantage of the brake lever is constant. And the hydraulic pressure is therefore a constant in this case. This is fundamental in the stated example in this thread (see post #1). This is NOT a case of equal braking torque. It is a case of panic stop maximum friction. In which case the larger the rotor, the greater the braking force.

Have a nice day,

you are "Wriggling " Alan, ... trying to get away from your original statement re Rotor diameter vs calliper force...

the larger the rotor, the greater the braking force.

.. correct,.. but not necessarily a greater force on the calliper/mount. You are mixing up "braking force" .. with calliper loading force.
for any given braking force (stopping power) ,.. a larger rotor will result in less calliper loading force. ( because the braking "torque arm" is larger)