ACK!! No Brakes!

[dcstrom]

So I was visiting a friend in Northern California who lives 20 miles down a narrow, twisty, up-and-down dirt road. I wasn’t going particularly fast as I have 200lbs of gear on board. My technique when approaching tight turns, especially downhill ones, is to just touch the front brake, then drag the rear as I get deeper into the corner.

This worked fine for a while, but then the rear brake lost pressure – just nothing there. I could pump it and get something back, but it’s obviously not right. What was worse was that the front brake, while still sort-of working, would pulse as if the ABS was cutting in and out, but with about a second between pulses. A second can feel like a loooonnggg time when you are approaching a corner with a steep drop-off on the other side.

I stopped and both front and rear discs were blue, but the rear was hotter than the front. I let things cool down for 5 minutes and then continued gingerly, and had no further problems.

When the front brake started pulsing I considered stopping and disabling the ABS. But it occurred to me that the problem is not with the ABS, or not JUST the ABS – it must have something to do with the linked brakes? Presumably I had boiled the fluid in the rear? And then when I squeezed the front it would have to build pressure throughout the entire system before the front brakes would work. At that point there was some interaction with the ABS to cause the pulsing.

Does that sound like a fair assessment? And what’s the solution – bleed the brakes and put higher-spec fluid in it? Which one?

I’m a bit annoyed – in this case I was able to work around the problem, but I’m not going to be impressed if I get this problem on some much more difficult roads I may encounter on this trip – Copper Canyon is one that comes to mind… will be there in a month or so.

On the return trip I tried a different technique - slow on the approach to the corner (so, not much braking), and fast on the exit. Even with a full load, TCS2 makes it easy to hang the rear out so I can pretend I'm an expert rider


Trevor

 

[greg the pole]

Odd... I don't think you could
Boil the brake fluid that quickly. Should be dot 4 I believe.

Can you check both your wheel sensors? If
They are loose, the ecu will get mixed
Signals or no signal at all. This might affect the abs as well as tc.
Maybe it's air in the system, loose banjo
Fitting on one of the brake lines?
Not sure what else it could be.

 

[autoteach]

sounds like you boiled the brakes. I let a friend take mine for a spin and he had his fat foot on the rear brake for 4 blocks and swore he didn't. Blue disks = high heat. ABS can't cycle properly with air in the line. The difference between boiling point on dot 3 and 4 isn't much for off the shelf car store fluid. The good stuff is where it is at. I prefer ATE Super Blue.

 

[bloodline]

Boiled the brake. I've done it on my Yz. It usually happens when mud causes the brake lever not to return. In this case, I suspect the author kept the pedal covered and unknowingly applied the brakes for a long time.

 

[stevepsd]

Trevor,

Sorry to hear of this. Something caused the brakes to drag, that's for sure. And now you have a good chance that the brake pads and rotors are glazed and won't stop worth a hoot. Especially if the rotors are blue. Hopefully the rotors are not warped. Will need to hit the rotors and pads with 120 grit sandpaper to break the glaze.....

 

[snakebitten]

Boiled the brake. I've done it on my Yz. It usually happens when mud causes the brake lever not to return. In this case, I suspect the author kept the pedal covered and unknowingly applied the brakes for a long time.

Sounds plausible. But I suspect he doesn't think so. He didn't consider it as an explanation.

I do know this though; you can ride dirt roads for HOURS on this thing and not have his problem. I did a 4 hour non-stop dirt road through the mountains. Lots of gas/braking up n down. Most amazing big-bike ride of my 54 years. Other than loosening the right headlight connector, the beast was flawless. Road 6 more hours on tarmac to get back to my bed. (Melbourne)

Amazing machine.

 

[dcstrom]

Trevor,

Sorry to hear of this. Something caused the brakes to drag, that's for sure. And now you have a good chance that the brake pads and rotors are glazed and won't stop worth a hoot. Especially if the rotors are blue. Hopefully the rotors are not warped. Will need to hit the rotors and pads with 120 grit sandpaper to break the glaze.....

Yeah, that would be me! As I said, lots of steep downhill corners close together, heavily loaded, and I was on the rear brake more than I was off it. Not enough time between applications for the brakes to cool I assume. It's an unusual circumstance for sure, but not THAT unusual and during the next year I will be loaded and on steep roads in Sth America. I'd like to think I have a bit more leeway before the brakes start going away on me.

Rotors are not warped and brakes still work fine. Rear rotor is a bit grooved but has been like that for quite a while. Will be having a major service soon and will get the experts to take a look.

Trevor

 

[autoteach]

What rpm and what gear on the downhill?

you should bleed the brakes, as it won't entirely reconstitute itself to fluid.

 

[markjenn]

Yeah, that would be me! As I said, lots of steep downhill corners close together, heavily loaded, and I was on the rear brake more than I was off it. Not enough time between applications for the brakes to cool I assume. It's an unusual circumstance for sure, but not THAT unusual and during the next year I will be loaded and on steep roads in Sth America. I'd like to think I have a bit more leeway before the brakes start going away on me.

The problem is that the rear brake has only a small fraction of the stopping power of the front and can dissipate only a small fraction of the heat. Do the math and the front has about 650 sq cm of swept brake area, while the rear has about 250 sq cm. This means that almost 75% of the total stopping power (and heat dissipation) of the bike is on the front of the bike.

When you start asking the rear to supply nearly all the stopping power in a challenging situation (loaded, hills, etc.), it quickly overheats. It is no different than slapping an XR100 brake on the front of a sportbike and expecting it to repeatedly stop from speed. And when it overheats enough, you boil the brake fluid and lose the brake all-together. And this probably plays hell with the ABS system, even on the front.

The only real solution is to not rely on your rear brake so much. In challenging situations, you simply can't ask it to supply the majority of the stopping power of the bike. It's not big enough.

- Mark

 

[viewdvb]

Its not as hard as you think to boil DOT 4 fluid. I used the same technique as Trevor on a non-linked bike on the road for steep downhill mountain hairpins. I don't see much alternative to dragging the rear to prevent increasing speed as you tip in. Although I could use a lot more front before trailing the rear round the bend my approach speeds were higher than might be expected off-road. I definitely did not touch the pedal between applications. I admit I was fully loaded but the rear brake disappeared after 5 or 6 close hairpins. Nothing, not even pumping it. I changed my approach and slowed down a lot, avoiding the now useless rear brake. 5 minutes later it was working perfectly again and stayed that way for the rest of my trip with no additional sponginess or slack implying that the fluid did indeed reconstitute. I changed to DOT 5.1 (avoid DOT 5 which is not fully compatible) and the problem never reappeared not even when provoked in a similar manner. The significant difference in temperature tolerance between 4 and 5.1 was enough to do the trick.

 

[Waspworks]

Solution = Knock it down a gear and go in at higher rpm...

Never believed in trail braking. The only time I am ever touching the brakes mid corner it is the front brake (if i'm in too hot) or the back brake on roundabouts and very slow corners, perhaps behind traffic..

Greg.

 

[scott123007]

I don't understand why anyone is using the rear brake at all. You can use the front which automatically integrates the rear, and never be in any danger of losing traction, on any surface. The first thing I did with my bike was to practice grabbing a handful of front brake in all sorts of terrain to see how it would react, and never did it do anything but come to a crontrolled stop. I know it's hard to wrap our heads around the idea that the ABS works that well, but if you don't trust it, you're just compromising your learning curve.

 

[dcstrom]

I don't understand why anyone is using the rear brake at all. You can use the front which automatically integrates the rear, and never be in any danger of losing traction, on any surface. The first thing I did with my bike was to practice grabbing a handful of front brake in all sorts of terrain to see how it would react, and never did it do anything but come to a crontrolled stop. I know it's hard to wrap our heads around the idea that the ABS works that well, but if you don't trust it, you're just compromising your learning curve.

Exactly what I did too, and it didn't take long to develop confidence in braking hard on loose surfaces. The ABS is fantastic when braking in a straight line - but that's not what I'm doing here. The ABS won't help you much when TURNING at slow speed on a steep, downhill, loose surface. The tendency is for the front tire to slide sideways when you load it in the middle of one of these turns. I still use the front a little, but I feel like dragging the rear helps settle the bike and pull it into the turn, and if it happens to slide sideways I don't care - it's not as much of a problem compared to getting the front sliding.

I'll admit my technique is a holdover from years of riding non-linked, non-ABS bikes, and if somebody has a better way I'd be happy to hear it

 

[BaldKnob]

My technique is full on front brake prior to turning then just trail with the rear if needed while leaned over. Works great and allows the front tire to focus on steering. The S10 also has very good engine braking so don't be scared to click it down and use the tranny. There is no slipper clutch so exercise caution leaned over... the ass-end will step out!

 

[troll]

I don't understand why anyone is using the rear brake at all. You can use the front which automatically integrates the rear, and never be in any danger of losing traction, on any surface. The first thing I did with my bike was to practice grabbing a handful of front brake in all sorts of terrain to see how it would react, and never did it do anything but come to a crontrolled stop. I know it's hard to wrap our heads around the idea that the ABS works that well, but if you don't trust it, you're just compromising your learning curve.

I am here with scott. I don't use the rear brake unless I am trying for max brake application or unless it is super greasy mud. The linked brakes and ABS are beyond what I ever imagined they would be. I also use engine braking a lot, but it will skid the rear without the control of ABS. This bike is almost idiot proof. Use that hand brake, it works amazingly well. Even on loose down hill turns ::26:: ::26::

 

[Rasher]

Solution = Knock it down a gear and go in at higher rpm...

Never believed in trail braking.

Yep, most riders are happy to redline their motors when gaining speed, but somehow seem to think more than 3,000rpm on a closed throttle is unacceptable.

Ridden other bikes on some of Europe's highest roads such as the Stelvio Pass and La Bonnette (must be well over 100 corners in a 10 mile steep downhill descent) and never boiled the brakes - Warped discs though ZZR1400 (twice - Pyrenees and Black Forest) and GS (Alps) and it seems most manufacturers now make discs from old bean tins - post warranty I fitted PFM's to the ZZR and could not warp them (then again neither could Steve Hislop when he set IOM TT records with PFM's)

Trail Braking is great for an extra couple of tenths off a lap time, or for throwing your road bike into a hedge. I prefer to be at the right speed in the right gear approaching a bend, ideally with a bit in reserve.

Often riders get "locked" on the brakes, normally you should be back on the gas just after you turn in, staying off-throttle often makes a bike feel horrible mid turn, especially on downhill turns with the front feeling like it is gonna wash, the answer is normally to get back to gas, but many folk grimly trail the brakes instead.

I tend to go in late (deep) and slow on downhill mountain switchbacks and to get back to gas ASAP, and on those bends that go on forever let the engine do a lot of the braking - often I am in second, and sometimes first gear on these corners, waiting, waiting, waiting for the exit drive, but it is very easy to go in too fast to start with - most cornering problems on motorcycles are caused way before the bend has even started, even if you don't notice until mid turn or exit the chances are your entry line / speed was the culprit.

 

[Waspworks]

Yep.... Down a gear you have gobs more power when you want it, you have the advantage of stronger engine braking, and you can play on and off the throttle to regulate corner speed.
Never been one afraid to haul like hell on the front brakes mid corner in the face of pending disaster.. Lot safer than hauling on the back brakes.

Greg.

 

[thfraser]

Good thread, especially for a dirt noob like me. Last weekend, this bike absolutely spoiled me. We did an easy 50 miles of off road driving, a mix of gravel and those sorta gravel roads where the weeds in the center are taller than your waist (in some cases they were almost as tall as the bike). Then to top this off, most of the riding was over leaf infested and covered areas, and we did a bunch of miles at night too.

End result, the brakes work great, I didn't have any issue with the brakes, at first I was a touch nervious, but the S10 just makes it so easy. I went through some pretty slimy muddy areas with leaves. Occasionaly the bike heaved side to side and bucked a little, but nothing that the TC and ABS couldn't handle. I only napped the bike once, as I went through a decent sized rut filled with water, mud and leaves. And that was my fault as the wheel started to go up the side of the rut, and I ended up stalling it. But it started right up and trucked out of the rut like it was a perfectly normal happenstance. At the end of the rut, was a leafy covered gravel road, the brakes easily handled the bikes mass and stopped with ease.

I took the ERC course the weekend before the trip. We practiced some emergency braking in the course - Wow, the brakes on the S10 are awesome. I'm sure that training, even though it was pavement, helped me learn how the S10 brakes. I also did a little practicing when we had some straight sections on the roads/trails that we traversed. It totally surprised me on how well they work. We were 12 miles back on some gravel/dirt road from the nearest paved road, including some nastly little switch backs over the mountain. The S10 handled excellent, I was able to manage an excellent pace without any issues. The brakes and new K60's provided me the confidence that I needed for those nasty switchbacks. Sail2xxs was following me for those 12 miles and I think I surprised him on my pace!

If I didn't have the S10's excellent ABS, TC, torque and engine braking, I would probably had taken a bunch of naps with the bike.

All I know, is I want to get another chance to hit some of those off road areas and do some more riding! ;D

It was one of my best motorcycling weekends ever!

 

[Tremor38]

Exactly what I did too, and it didn't take long to develop confidence in braking hard on loose surfaces. The ABS is fantastic when braking in a straight line - but that's not what I'm doing here. The ABS won't help you much when TURNING at slow speed on a steep, downhill, loose surface. The tendency is for the front tire to slide sideways when you load it in the middle of one of these turns. I still use the front a little, but I feel like dragging the rear helps settle the bike and pull it into the turn, and if it happens to slide sideways I don't care - it's not as much of a problem compared to getting the front sliding.

I'll admit my technique is a holdover from years of riding non-linked, non-ABS bikes, and if somebody has a better way I'd be happy to hear it

Hmmm. I don't think there is really a problem with the brakes here. The weight of the Tenere combined with the downhill grade and frequent dragging of the rear brake doesn't make boiling of the rear brake fluid sound surprising. I've boiled the fluid in the rear brake of a 250cc motard with no luggage going down a steep grade with hairpin turns. I would guess what you were doing with a fully-loaded Tenere on maybe slightly less of a downhill grade and around larger radius turns would have the same combined effect. I'd say a slight adjustment to technique is all that's needed.

 

[dcstrom]

I just had the 24k service and brakes were bled, replacing original fluid with Motul 600. Now I have a much firmer feel at the lever, better than it was even new. Actually I always though brakes felt a bit spongey, not any more.

Between the better fluid and adapting my riding style, I hope not to see this problem again.