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BRAKE CALIPERS. The good, the bad, the lovely.

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Great brakes are a wonderful thing regardless the speed potential of the machine they are tasked with stopping.  They provide a level of luxury and inspire confidence when riding in challenging terrain. 

Of the various types and designs, the first aspect I'd like to discuss is the "opposing" piston arrangement vs. the "parallel" type we have on our 230F.  Most dirtbikes employ the type we have on our 230F, not sure "parallel" piston is the correct term for these but they require a bracket and pins so it can slide and apply pressure to the rotor.  While it pushes the pad against the rotor it also pulls the the pad on the "dead" side of the caliper in to put pressure on the other side of the rotor. 

Then there is the "opposed piston" style caliper, an equal number of pistons on each side of the rotor.  It is rigidly mounted, requires no bracket or pins and pushes both of the brake pads against the rotor and then pulls them back when released.  Not only does this style of caliper provide better clamping force, it does not require pins to slide on which is a good thing I'd think in the off road environment.  One downside is the added width of the caliper on the wheel side of the rotor, a narrow area on most off road wheels.  A Yamaha R1 caliper I have sitting here is too wide to fit over the rotor on my 230F, need to find something smaller/narrower.

This brings us to the mounting style, the hot new "Radial" style vs. the traditional .....not "Radial" style.  All radial mount calipers I've seen have "opposed piston" arrangement.  The braking force the calipers absorb is "better" absorbed according to the internet.  The also look very racer, mad baller, well hard.

KTM currently uses a radial mount caliper on the front of their 85SX and 105SX, possibly on the larger models as well.  Prior to the radial mount they used a slick looking traditional mount 4-piston "opposed" caliper front and rear on some models. 

With all of the recent discussion of how to best go about shedding weight while not giving up any performance I think it is important to consider all of the options out there and upgrade where ever possible along the way, especially if a new caliper must be procured or a custom set up figured out.

Anybody have experience with KTM 4-piston caliper brakes?

Edited by MetricMuscle
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OK, in an effort to cool this topic down, how about sharing what you know about good trail bike brakes?

What calipers are you familiar with that work well?

What calipers are known to be great, better than the competition?

Since all of the 250/450 MX bikes use the same front brake pad I am assuming all of their caliper are very similar in design.

All of the current Mini MX bikes use 2-piston calipers or 4-piston except for the CRF150R.  It still uses the same single piston caliper the CR80/85 did.  It is common to upgrade to a larger CRF250/450R caliper using an adapter bracket on the Honda forks but I'm wondering how the OE 2-piston calipers on RM/KX/YZ 85/100 compare to the CRF250/450R calipers.  The brake pads are similar in surface area.  I'm thinkin' the Mini MX caliper would be lighter but still provide similar power.

 

Other aspects of disc braking systems which add to power is rotor diameter, pad material, master cylinder size and design........

Is it risky to run a larger diameter rotor in gnarly rocky rutted rooty terrain, from an "easy to damage" perspective?  A larger diameter rotor offsets the need for stronger clamping force.

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Isn't the stock 230 ffront brake plenty good for dirt?  Are you planning to SuMo?

Buddy's Yama Wr250 SuMo has 17" wheels and larger front rotor.  He dirt rides it with dot knobbies, says brakes are awesome.

 

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I've used most of the brake systems mentioned:

Opposed piston fixed calipers on my Trials bike (made by AJP) and floating calipers on J bikes (1 & 2 piston made by Nissin)

Automotive almost exclusively use floating calipers.

They all work well but you must also consider that what you feel in the lever when riding is also the result of the master cylinder design and the friction of the brake pads because it all about the brake creating torque at the rotor and how that transfers to the tire contact patch. 
Case in point is the mini bike hubs use a 220mm rotor vs 240mm on most other dirt bikes, that means less torque if other things are equal but a lot less force at the tire contact patch if you install a 21" rim/tire.  I had that problem with a CR85 front end on my XR so I made a bracket and used a XR250R front brake and it works good with the 21" front wheel, even with the 220mm rotor. A friend has used single piston and double piston mini bike brakes on his conversions and i've found the brakes more than adequate with a 21" wheel, but not as strong as a caliper from a full size bike. Brake pad material also makes a difference, see later.

The Trials bike with the little 4 piston caliper has brakes with very light lever pull and smooth brake action.

My CRF250X uses the same caliper as most other late Honda dirt bikes. However the lever feel is very light and the brakes are grabby at low speed which can make low traction situations sporty. It is interesting that the Honda pads are large compared to other calipers and use a high friction pad material. DOT requires all brake linings to be coded for  normal and hot friction, here is a good read on "brake edge codes"  http://www.federatedautoparts.com/Docs/TTBulletins/S001E005.pdf and http://faculty.ccbcmd.edu/~smacadof/DOTPadCodes.htm

The HH pads have the highest coefficient of friction and are known to be grabby at low speeds; and the CRF250X uses HH pads and I don't like grabby brakes.  EBC sells several different friction  materials for each pad so there are options to adjust brake feel, their descriptions don't always use edge codes but they do describes the friction and recommended applications.  And the EBC pad site: https://ebcbrakes.com/products/brake-type/

Master cylinders make a difference with various piston sizes and leverage ratios. Rebuild kits can provide a clue to piston size.

One other interesting item is Nissin makes two different sizes of pads for use on a several calipers, that offers a method to change braking with a simple pad change.

88-95 XR250R
87-94 CR125/250/500
88-92 XR600R
91-92 XR250L
88-92 XR600R
All of the above use the same pads but the EBC catalog lists a larger pad that also fits:

95-07 CR125/250
96-04 XR250/400R
96-08 RM125/250
03-11 CRF230F
07-11 CRF150F
04-11 CRF250R/X
02-11 CRF450R/X

 

 

 

Edited by Chuck.
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Don't know a whole lot of "technical" info, so to speak, on brakes, but what I do know is this:  on a KTM, you'd better not be pulling that brake lever with more than one finger unless you want to go over the bars.

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16 hours ago, sneaky98gt said:

Don't know a whole lot of "technical" info, so to speak, on brakes, but what I do know is this:  on a KTM, you'd better not be pulling that brake lever with more than one finger unless you want to go over the bars.

Oh Yeah! That one I don't like! 

I had a chance to ride a mates Yammy FZ09 recently. Holy cow that thing has some stick!!  :jawdrop: 

All was going well until I grabbed a handful of front brake at 'ahem' KMH. It frightened the s**t out of me! If it didn't have ABS brakes, the bike and I would have been doing high speed front flips down the road.

So now when I ride it I keep saying to myself: 'One finger, one finger, one finger! :naughty:

Very nice bike though! :thumbsup: :) 

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I am currently running the 4 piston ktm/formula brake system. '04 105 front end. I have started using the Goldfren S33 pads which seem to offer better bite.  This seems to be a decent set up for trail work.  Most stops only require one finger, but you need to pull pretty hard on the lever if you want really want to stop quick.  The brake does get hot and starts to fade with prolonged use.  I have never been in a situation where I could not slow down, but extended down hill sections require increased lever pressure as time goes on. I think that the oversize rotor kits would be nice, and I may go in that direction when the stock rotor wears out.

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20 minutes ago, stevethe said:

My bike uses the CR85 forks and wheels and I can say there was a big difference in going from a one piston to a CRF450 two piston caliper. 

Do you feel the smaller 220mm rotor is acceptable for a 230f sized bike with the addition of the bigger caliper? Galfer makes a 240mm "oversized" rotor for the 150R/80/85 size hub. I assume youre running a 21" rim on the smaller hub?

Edited by xplodee
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Just now, xplodee said:

Do feel the smaller 220mm rotor is acceptable for a 230f sized bike with the addition of the bigger caliper? Galfer makes a 240mm "oversized" rotor for the 150R/80/85 size hub. I assume youre running a 21" rim on the smaller hub?

Yes CR85 hub and smaller disc. With the twin piston caliper it's a stopper. No need for a larger rotor. 

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Great info.  I didn't realize the Mini MXers used a 220mm rotor and most everything bigger a 240mm rotor, including the 230F. 

I have CR85 forks on one of my 230Fs but I need to replace or repair the left side lug, the lower part which the axle goes thru and the brake caliper mounts to.  The axle hole was drilled out for a 15mm axle but it isn't straight/square/plumb so the caliper drags on the rotor a little bit, even with shimming.  I've come up with a few ideas but wanted to consider other factors that could be optimized at the same time.  For some reason, CRF150R forks are the most expensive and least plentiful on eBay compared to CR80/85, RM85 forks, both of which are Showa 37mm forks but with a 12mm axle hole instead of 15mm which the 150R is in OE form.  The RM85 forks have different caliper mounts for a different 2-piston Tokico caliper and I am assuming is spaced for use with a smaller 220mm rotor.  I'll be using a CRF230F front wheel with a 240mm rotor and may try to use a CRF250R front wheel which also has a 240mm rotor. 

Another thing which occurred to me is that a 2-piston sliding caliper will have LOTS more pad area than a 2-piston opposed caliper will.  Pad area is important for both providing friction and absorbing heat.  My OE 230F front caliper has always performed well with minimal maintenance, just pad replacement.  No issues with the sliding pins, they are sealed up with grease after all.  But it isn't just pad area which creates the grab, it's the leading edge.  Some 4-piston calipers use 4 individual pads so as to have 2x the leading edge length.  Some pads have grooves cut in them which will create another leading edge.

Another thing I don't like is how low the calipers are mounted on offroad forks.  Adapter brackets move the caliper even further down to make it even more prone to coming in contact with something hard.  I realize this probably doesn't happen as much as I'm worried about it but why not move it up instead of down?  Yes, there are limitations but if someone is making an adapter bracket and can locate the caliper higher, instead of lower, then why not? 

Would a 320mm SuperMoto rotor be a liability offroad? 

Heat.  The rotor will always feel hotter than the calipers after hard braking and surely sintered metal pads should absorb and transfer more heat than organic or other such less metallic pads will.  A larger diameter rotor can absorb and transfer heat better than a smaller one simply due to mass but what are the best ways to manage brake heat transfer and dissipation?  If staying with a smaller diameter rotor can the design compensate for less mass?  Wave rotors claim to do some magic shit that isn't obviously apparent to me but they do stay cooler.  More surface area on the outer edge?  Creates a cooling wind vortex which vacuums the heat out of the rotor?  Is there some fancy trans-thermal adhesive that can be used on the back of the pads to improve heat transfer to the pistons or caliper?  Is it possible I'm over thinking most of this?

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Rotor cooling is one reason I don't use rotor shields.
For more information about brake parts download EBC's Motorcycle Parts catalog. It has listings for pads, rotors etc plus  cross reference and application sections  in the back.
My take is that the J bikes tend to use generic Nissin brake parts but often with unique features for a particular bike model, the result is brake pads will fit a broad range of bikes but the calipers may not interchange within the same group of bikes, but it is a good indicator for further research.     

 

2 hours ago, xplodee said:

Do you feel the smaller 220mm rotor is acceptable for a 230f sized bike with the addition of the bigger caliper? Galfer makes a 240mm "oversized" rotor for the 150R/80/85 size hub. I assume you're running a 21" rim on the smaller hub?

A 220mm rotor is about 9% smaller in diameter than a 240mm rotor so 9% less torque with everything else being the same. You would feel that as a slightly firmer lever.
Two things that affect braking happen with a larger caliper; larger friction area and more piston area for greater pressure against the pads. 

I measured the pistons on some calipers and changing from a CR85 caliper to a two piston XR250R caliper increased piston area the piston area 84%.
Same thing for pad areas; changing a CR85 caliper to XR250R caliper increased pad area about 60%.
That is such an increase in braking that you will also need a MC with a piston larger than the CR85, so I used the XR250R MC. 

I tried using the XR250R MC with the CR85 caliper (and 21" wheel) and lever pull was too high, almost like a drum brake because it wasn't easy to lock the front wheel on dirt.  The CR85 MC needed a rebuild and based on the above research I felt a larger brake system would be better, and it is.

My CRF250X has a similar size caliper but the Honda pads are HH class friction (edge codes) and the brakes are too grabby so I need to find some FF pads.  If you read the links that I posted the FF pads have 30% less friction than the HH pads and a rep for smoother initial brake than the HH pads.  That would make my X brake feel more like my XR250R brake.

I have a Trials bike with those little Trials types of calipers and discs, and the brakes are one finger with shorty levers at low speed. Since I don't ride it as fast as my bigger bikes I don't have much experience with higher speed braking but it seemed OK and a friend trail and logging road rides his without problems.

Edited by Chuck.
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1 hour ago, MetricMuscle said:

Great info.  I didn't realize the Mini MXers used a 220mm rotor and most everything bigger a 240mm rotor, including the 230F. 

I have CR85 forks on one of my 230Fs but I need to replace or repair the left side lug, the lower part which the axle goes thru and the brake caliper mounts to.  The axle hole was drilled out for a 15mm axle but it isn't straight/square/plumb so the caliper drags on the rotor a little bit, even with shimming.  I've come up with a few ideas but wanted to consider other factors that could be optimized at the same time.  For some reason, CRF150R forks are the most expensive and least plentiful on eBay compared to CR80/85, RM85 forks, both of which are Showa 37mm forks but with a 12mm axle hole instead of 15mm which the 150R is in OE form.  The RM85 forks have different caliper mounts for a different 2-piston Tokico caliper and I am assuming is spaced for use with a smaller 220mm rotor.  I'll be using a CRF230F front wheel with a 240mm rotor and may try to use a CRF250R front wheel which also has a 240mm rotor. 

Another thing which occurred to me is that a 2-piston sliding caliper will have LOTS more pad area than a 2-piston opposed caliper will.  Pad area is important for both providing friction and absorbing heat.  My OE 230F front caliper has always performed well with minimal maintenance, just pad replacement.  No issues with the sliding pins, they are sealed up with grease after all.  But it isn't just pad area which creates the grab, it's the leading edge.  Some 4-piston calipers use 4 individual pads so as to have 2x the leading edge length.  Some pads have grooves cut in them which will create another leading edge.

Another thing I don't like is how low the calipers are mounted on offroad forks.  Adapter brackets move the caliper even further down to make it even more prone to coming in contact with something hard.  I realize this probably doesn't happen as much as I'm worried about it but why not move it up instead of down?  Yes, there are limitations but if someone is making an adapter bracket and can locate the caliper higher, instead of lower, then why not? 

Would a 320mm SuperMoto rotor be a liability offroad? 

Heat.  The rotor will always feel hotter than the calipers after hard braking and surely sintered metal pads should absorb and transfer more heat than organic or other such less metallic pads will.  A larger diameter rotor can absorb and transfer heat better than a smaller one simply due to mass but what are the best ways to manage brake heat transfer and dissipation?  If staying with a smaller diameter rotor can the design compensate for less mass?  Wave rotors claim to do some magic shit that isn't obviously apparent to me but they do stay cooler.  More surface area on the outer edge?  Creates a cooling wind vortex which vacuums the heat out of the rotor?  Is there some fancy trans-thermal adhesive that can be used on the back of the pads to improve heat transfer to the pistons or caliper?  Is it possible I'm over thinking most of this?

Transferring heat to the caliper is a bad thing. The rotor is far more effective at removing heat than a big mass like a caliper and fluid. Heat buildup is always a bigger problem with worn brake pads and brake fluid that is past it's prime.

I am a bit surprised that calipers do not have any cooling fins though.

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I have the ebc oversized brakes and they are more than enough, all this bike needs rear disc. What rear hub is the best option?

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1 hour ago, 4strokeridertt said:

Transferring heat to the caliper is a bad thing. The rotor is far more effective at removing heat than a big mass like a caliper and fluid. Heat buildup is always a bigger problem with worn brake pads and brake fluid that is past it's prime.

I am a bit surprised that calipers do not have any cooling fins though.

Ok, so we want to transfer as little heat as possible to the caliper, let the rotor dissipate as much heat as possible.

 

7 minutes ago, ROD Kerry said:

I have the ebc oversized brakes and they are more than enough, all this bike needs rear disc. What rear hub is the best option?

 

What is the diameter of your oversized rotor?

I use my rear brakes so little I'll just stay with the drum.

Hey Chuck, is there a drum brake arm which will fit our OE CRF230F rear drum that is shorter in length than the OE 230F part?  I'm talkin' about the arm which attaches to the shaft which opens the shoes.  If I could find a shorter one then I would like my rear drum even better.  Quicker acting and with less power would make it easier to use and less likely to lock up when I do happen to use it which is when negotiating extended down hill runs using front brake, engine brake and rear brake.

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From my experience drums have a lot of issues from lack of water resistance to short usable lining life. On my old RM I needed to remove and clean the brakes after every Enduro and add a shim to the anchor pin so I could get thru the next Enduro. I also replaced the front linings every other. I also use to pack a short strip of soda can aluminum that  I could wrap around the shoe anchor to get a few more miles out of the linings.

Honda likes to reuse parts so I suspect the splines on the shoe cam are standard Honda size and over the years Honda has used a variety of styles and sizes of levers on off road bikes. Another option is reduce the length of the arm on the brake pedal, just drill another hole for the brake rod.

Or with some hacksaw work you can reduce the length of lining on the leading shoe. And add some cross and X groves to speed up recovery from water.

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