Better braking


rayivers

Well-known member
Location
CT, USA
I'll never forget the first time I saw an Alta up close - a '17 MX, at Town & Country Cycle in Hamburg, NJ. I was really impressed - the quality ! fit & finish! components! - and this was all before the test ride. :) The Brembo stuff looked great, and the brake pedal had plenty of clearance to the footpeg pivot with a cool showbike-style height adjuster. I remember thinking it would be so nice to have good stoppers from jump, after initial minor adjustments.

5 years later, things are a bit different. All that's left of my OEM system are the pedal, calipers, and hoses.

I need my brakes to react instantly, strongly, and consistently to rider input. My '08 YZ250F took two rides and @ 10 mins total adjustment time to get and stay there; every other bike I've owned fought me, sometimes to a draw. My Alta's pretty good now, though I'd still like 1-finger power up front.

Front Brake (pads, master cylinder)

The OEM setup worked decently at first; the new sintered pads & new rotor mated well, and the lower-pressure hydraulics (11.6:1, caliper:MC-piston area ratio) worked fine for me w/3 fingers but felt weak using 2, and unusable w/1 finger (which I strongly prefer). The rotor wore quickly & the holes carved slots in the pads, causing the brake to lose power. I surfaced the pads, but even after re-bedding them it was never the same. If you want to use new sintered pads and have a worn rotor, I'd highly recommend a new rotor or they'll take a long time to break in, with reduced braking power until then.

Next up were Brembo carbon-ceramic pads (below, OEM on R), which worked well for me on another 11:1 lower-pressure system. Once broken in they worked better than the OEM's even with the worn/uneven rotor, with more initial 'bite' and consistency. I've found that all pads - especially sintered - work quicker & stronger with higher pressure that raises friction-surface temps quickly, keeps the rotor surface flatter and debris out of the contact patches, and usually has shorter brake-on periods that are easier on rotors.

Brembo & OEM Alta Brake Pads (small).jpg

Like many Brembo and/or non-sintered pads I've tried, I had to source these from Europe (I've had good luck with Carpimoto and M4Tuning). Ask questions and get photos before you buy if there's any doubt about what you're getting, as nowadays it's ridiculously expensive to return them even if the vendor is willing.

At this point things were better but still not quite there, so I put on the Nissin '3/8' (.375" / 9.5mm-piston) master cylinder from my wheelie-practice bike (used on Yamaha '08 YZ250F and many other YZ's, eBay etc.), for a 12.7:1 ratio. I like the Nissin lever a little better, and I can adjust it closer to the grip. I also like the front hose connection, which adds a little hose slack & routes it away from the number plate.

Nissin F Master Cylinder (small).jpg

It was definitely an improvement on the Alta, but not like it was on the other 11mm-MC system. My front brake is now instant and consistent, though not as powerful as I'd like. I may go to a 9mm Nissin or Brembo MC in the future (p/n 10767774, OPP Racing), but I've got consistent 2-finger braking now so I'll live with it for a while.

acing-silver-axial-front-brake-pump-ps-9-with-tank.jpg


Rear Brake (pads, master cylinder, pedal-height adjuster, MC-plunger shimming, return spring)

The rear-brake work made the front look easy. :) The weird pedal-height adjuster had very limited range, so I had to make up a larger one that hit the pedal-pivot boss. :( With grinding I just barely squeaked out the tip lowering I needed (pic below is pre-final-adjustment, it almost hits the pedal boss now). I wanted a pedal that my foot didn't touch till I braked, then had extremely short tip travel to full braking power. To do this I had to set the pedal height precisely by trial and error, then adjust out nearly all the pad / rotor clearance with the shim washers. The tip of my brake pedal moves a total of .310" / 8mm, and the brake doesn't drag at all.

Pedal Height Adjuster (modified, small).jpg

Since the weak OEM return spring necessitated using an aftermarket Fasst spring, which eliminated the ability to thread-adjust the MC plunger at the low pedal height I had to use, the plunger needed to be shimmed using washers between the Fasst spring retainer and the plunger bottom - like I said, easy. :) I mean precise shimming; .133" / 3.38mm was too much (brake dragging) and .125" / 3.2mm wasn't enough (no dragging, but a little too much foot motion / effort required for instant braking). Hopefully .130" / 3.3mm will be perfect (the arm ratio is 6.3:1, pedal tip to MC-plunger motion). The good news is I finally have a rear brake that does exactly what I want, and nothing I don't.

I also changed out the OEM PS13 master cylinder to a PS12 (Brembo p/n 10.8505.20, OPP Racing again; Brembo makes an 11mm, but it has a remote reservoir) for more everything; I found the 13 to be slow, weak, and inconsistent (OEM PS13 ratio 4:1, PS12 4.7:1). I used the same carbon-ceramic friction material as the front, which responded well to the increased pressure. It was a pain to bleed as the hose goes up and then down, but it got done (love that Motion Pro brake bleeder, and the Brembo no-leak nipples too). The old MC's rubber boot had to be moved over to the new MC as the new center hole was too small.

1247_1024x1024@2x.jpg

Motion Pro bleeder:
31Wwotlet-L._AC_.jpg
 

TCMB371

The Silent Assassin
Forum's Sponsor
Location
Temecula, CA
Whats the position of your rear brake pedal with the cam like that? I stand a lot (you can stand way more on electric bikes vs gas) and find that i prefer the rear pedal slightly higher than level with the Tusk footpegs. I usually ride on the balls of my feet and having the pedal higher makes quick dabs of the brake easy while standing. It's great for standing and braking (like you should be doing) as it doesn't require much ankle flex and lets you stay further back on the bike.

The return spring on the rear master cylinder is an absolute must on these bikes. Stock is way too easy to press which makes it too much like a light switch. I've recently been experimenting with doubling up the return spring for even more resistance. I'm back on the 1 spring setup now and i'm torn between the two. Might try to find a resistance level of 1.5 springs.

I run EBC Double H pads in the front and they are amazing. I've tried a few others like cheap Neutrons sintered metal pads, mid grade sintered pads, etc. Nothing has worked quite as well as the EBC's.

In the rear I never have issues locking up the rear brake and it doesn't fade either so i just run cheaper pads in the rear. Tusk Sintered Metal pads are fine in the rear.
 

rayivers

Well-known member
Location
CT, USA
The rear edge (highest point) of my pedal tip is even with the top of the lower frame tube. I'm 5'11" with unusually long legs, and my riding position on a stock bike is normally the basic 'jockey crouch', with feet aimed near the F tire contact patch. Since I can't really point them down much more, I need the brake to fully activate with minimal motion. With the way it's adjusted now, I can't feel the springs much at all, just a small amount of 'hydraulic squash' in the MC.

I can ride on the balls of my feet while standing, but as soon as I sit down they slip off the leading edge of the pegs & slide down to the arch, so that's where they normally stay.

My stock pads were HH sintered (BRM11EHH) - they worked pretty well. I'm currently looking for a 320mm front rotor & adaptor.
 

rayivers

Well-known member
Location
CT, USA
Front Caliper Replacement (2 x 28mm pistons)

Instead of the big rotor, I went with big caliper pistons - wow, what a difference! I used a Brembo 22.7610.00 2x28mm caliper (KTM p/n 59013015101, used on the '09 250XC-F and many others). Apparently Andrew Short used this with a 10mm master cylinder during the 2015 SX season, when he was the king of holeshots. It bolted right up, but it's bigger and 270g heavier - no free lunch, I guess. (a 320 rotor would've been heavier too, though). I got my caliper NIB on eBay for $186 shipped ($290 list).

Brembo 28mm F Brake Caliper (eBay).jpg

Installation did not go well - the bigger cylinders hold a ton of air, my Motion Pro 8mm mini bleeder was the wrong size (this one needs a 10mm), and the copper crush gaskets leaked with 11 ft/lbs on the banjo fitting. I went with Honda 90545-300-000 aluminum ones + carefully-applied hard-setting Permatex, no leakage.

Even after successful bleeding the lever felt soft, so I figured the first test ride would last about 50 feet. Wrong! Regardless of the feel in the garage, on the street it was instant and potent, with a more linear response than the on/off 24mm caliper. This setup feels exactly the same with 1 finger as it did before with 2, which was just what I wanted - as long as I remembered just-one-finger, I was instantly comfortable with it despite the big power increase.

After a dozen or so hard brake checks, I noticed two things: 1) the rotor was too hot to touch, it wouldn't have been before (caliper was cool, though); and 2) the rotor surface & old pads were finally making 100% contact, despite extensive break-in. High pressure did in minutes what medium pressure couldn't in months. I like high pressure. :D
DESIGN NOTE: to any company spec-ing out a brake system (Stark?), check out the list below and consider using big-piston calipers, which give a much wider range of power adjustment using easily-available & installable master cylinders.

Here are some rough relative braking-power numbers, lo to hi (if anyone can confirm or correct the question-marked items, I'd appreciate it)

12mm MC / 28mm caliper pistons / 260 Rotor: 10.9:1 (MC = master cylinder)
10mm / 24mm / 260R (OEM Alta, non-SM): 11.5:1
9.5mm / 24mm / 260R: 12.7:1
11mm / 28mm / 260R: 13:1
9mm / 24mm / 260R: 14.1:1
10mm / 28mm / 260R? (Andrew Short): 15.6:1
9.5mm / 28mm / 260R (my setup): 17.3:1
9mm / 28mm / 260R: 19.1:1
9mm / 28mm / 320R / Warp 9 cal. bracket #7?: 23:1 (includes bigger-rotor advantage)
10mm? / 4 x 24mm? / 320R (OEM Alta, SM): 27:1 " "

My own personal impression... a +5% higher ratio above is noticeable, +10% is significant, +20% an in-your-face increase, and +30% & up may be too much unless you're willing to use less fingers on the lever and/or change your front-braking habits substantially (my 17.3:1 setup is +50% over stock). My main concern in the near future is if a panic-braking situation pops up, my muscle memory will grab a big 2-finger handful and do my 1st real stoppie, which may not end well. After a few more rides I think I'll be OK.

For the EXR-to-SM guys who'd prefer more stopping power, the 23:1 setup above would give serious braking using the stock EXR fork + 320R wheels. It might be too much for dirt and get pretty hot during hard street stops, but it's easier & cheaper than changing out the wheel and fork, or trying to adapt the giant SM 4-piston caliper.
 

Philip

Administrator
Staff member
Location
Ann Arbor, MI
My own personal impression... a +5% higher ratio above is noticeable, +10% is significant, +20% an in-your-face increase, and +30% & up may be too much unless you're willing to use less fingers on the lever and/or change your front-braking habits substantially (my 17.3:1 setup is +50% over stock). My main concern in the near future is if a panic-braking situation pops up, my muscle memory will grab a big 2-finger handful and do my 1st real stoppie, which may not end well. After a few more rides I think I'll be OK.

A few years ago I went to the California Superbike School. Every student gets to ride an almost new BMW S 1000 RR there for the entire day -- a real superbike! That thing had unbelievable front brakes! EXTREMELY sensitive. They were so sensitive, I had to re-learn how to use them because my standard 1 or 2 fingers were not working at all! My fingers were not sensitive enough!

I ended up using a very weird technique. I would put the pointing finger on the brake lever, relax my right hand's grip, and then move my entire upper body and the forearm back. The pointing finger would pull the brake, but then the deceleration would immediately throw my weight forward, move my forearm back, and reduce the front braking. It appears as if I was using my back muscles to control the deceleration, LOL! I do not recommend this technique, but this is what I had to use in the interim while my right finger was learning the super-light braking efforts that were required on that BMW superbike.

IIRC, the Alta SM comes with the same Brembo front caliper as the BMW S 1000 RR, but only it has 1 of them and not 2.
 

rayivers

Well-known member
Location
CT, USA
Wow, that sounds fun & scary at the same time! Maybe that super-quick & powerful response is just what's needed to slow down quick in the 170 - 190mph speed range. I wonder if a foam or rubber tube pushed onto the lever to add a little softness would've helped, at least a little? Have you ridden an SM? I'm curious how that brake responds, seems like it should be plenty strong.

I'm certainly grateful for the 'squish' in my setup, especially after yesterday's ride in wet leaves. :( I did a few straight-line panic stops in the beginning which were twitchy but OK, after that it wasn't too bad (all 1-finger).
 

Philip

Administrator
Staff member
Location
Ann Arbor, MI
Have you ridden an SM? I'm curious how that brake responds, seems like it should be plenty strong.
Yes, at GP Motorcycles of San Diego back in 2006. The front brake was the most impressive thing about the bike. The rest of the bike was just okay, LOL! I tried more stoppoes than wheeloes.

IMG_20161221_1342450.jpg
 

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