Anti-Lock Brakes

This is -- of course -- a totally different situation, caused by the fact that a motorcycles centre of mass is much higher in relation to its wheelbase.

Nevertheless, a racing motorcycle's front tire can still be locked up by the brake.

Reply to
Alan Baker
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Seriously, what the hell?

Have you ever driven a car?

Reply to
Nate Nagel

nASScar still does it that way, and the lateral rod adjuster is controlled by a knob on the dash so the driver can make changes in brake bias as needed. Most of the rest of the world uses proportioning valves.

You still don't get it. Proportioning only ensures that no wheels lock up prematurely as you add braking pressure. But it does nothing to prevent lockup in general. Nor do you want it to, braking to the threshold of lockup is good driving technique.

Reply to
Steve

One wonders. A whole string of fact-free fiction posts in reply to himself.

If you type it enough times, it must be true... right??? :-p

Reply to
Steve

I'm beginning to wonder if he has even _read_ about driving a car.

Harry K

Reply to
harry k

It doesn't lock up because the rider doesn't let it. If one were to lock the front wheel of a motorcycle under braking, Really Bad Things would begin to happen Really Fast, the end result being a case of road rash.

That does not mean that the rider cannot force the front wheel to lock up if he for some reason he wants to (or, alternately, of the CoG is high enough, the motorcycle will flip end-over-end before the front wheel locks.) It just means that his self-preservation instinct is such that he will not allow that to happen.

No, it's defined as stopping in the minimum distance.

OK, I'll buy that.

Ultimate-braking? what's next? Stupendous-braking?

That's true of ANY vehicle. If you lock the wheels, the coefficient of friction between the tires and road decreases. Therefore, lots of people have spent lots of time, money, and materials trying to design braking systems that will allow the driver to come right up to that point before the wheels lock and be able to hold it there (and/or achieve this goal by other means, e.g. ABS.) This is not an ultimate brake torque issue - if you need more brake torque that's easy enough to achieve by any number of methods (larger diameter rotors or drums; higher coefficient brake linings; changing the pedal ratio and/or ratio of master cylinder bore to wheel cylinder bore; adding assist devices such as vacuum or hydraulic actuated power boosters.)

Proof of what? That a motorcycle has a high center of gravity and short wheelbase compared to a car? Most people already knew that.

nate

Reply to
N8N

AGREE heartedly with Ed on this one. For the average driver, ABS is a godsend in maintaining control while quickly reducing vehicle energy. And, insurance rates seem to support this thinking.

Agree also that under competitive driving conditions a well trained driver with heightened reactions can probably do better without ESC or ABS. That ability is probably good for a couple of hours at the wheel. But, at the end of a driving day, with twilight conditions and a longer complex reaction time, ABS can be a winner.

A downside is the tread damage that results from the staccato/machine-gun brake application one gets from ABS. After an aggressive ABS 'incident' it's a good idea to at least rotate tires or consider replacing them. Unless one does that, a set of brake discs will soon need aggressive resurfacing.

-- pj

Reply to
pj

Important to look at *which* cars.

On some models, brake drag may be caused by a defective windshield rain sensor.

Reply to
pj

I started driving in NW Ohio, where there was a lot of ice and snow from 1963 -

1983 when I left for... central Indiana where there was still some ice and snow.

I've slid on a lot of snow-covered roads. Its inevitable, even with AL braking. Stuff happens, and black ice rules, period.

Most memorable _not_ sliding was coming back from working a road rally in Michigan, and encountering some fairly pretty, fairly smooth, fairly deadly ice all over a really long bridge on I-475 around Toledo. Saw what was coming, lined the car up to enter the bridge straight-on, pushed the clutch in, and coasted all the way across it. But AL brakes or not, you're going for a ride if you attempt to change anything about your speed or direction on such a bridge.

He's very experienced, and _any_ speed on gravel with that car and it's AL brakes is "too fast for conditions." The best way to stop on gravel is to "lock 'em up." Its a fact. AL brakes make things _worse_ on gravel, not better.

Absolutely not. I have _lots_ of experience with gravel driving, and any normally-braked car would have stoped probably something like 15 ft short of the intersection with a maximum stop.

But it isn't hard to prove that a normally-braked car will out-stop an AL braked car severely on gravel.

Yeah, if you're boneheaded enough to hold the brake all the way down and not let the wheels turn, you have no control. Release them a bit, and you can steer - IOW, pump the brakes.

The situations where the difference between this method and the AL braking method meaning the difference between a crash and no crash are extremely rare. Most of the stuff you were going to hit with a regular braked car, you'll hit anyway with an AL braked car. Most of the stuff you were not going to hit with an AL braked car, you're not going to hit with a normally braked car anyway. The only real difference is knowing enough not to go sliding off into the weeds if you try to brake to the max - if you're experienced, you can do it. If you're not, you _might_ not slide into the weed in an AL braked car, whereas you would with a normally braked car.

Thats why I can be just as safe in either car, and don't need to be paying extra $$$ for the extra equipment that is also just something else to break down and need repair.

He was paying attention just fine - there was just no way to drive that thing on gravel reasonbly and expect to be safe, other than maybe pulling the wire for the AL brakes. That was a '93 Jeep Cherokee. My 98 Jeep Cherokee seems to do a little better, but is also kind of scary. The Subaru WRX does a lot better, although on gravel, I would still rather not have the AL.

Reply to
Dave Head

See...the motorcycle does achieve ultimate braking before front wheel lock-up. And there can't be anymore braking than the 100% weight transfer of ultimate braking.

There might be more hydraulic force to the brakes...possible...but not more effective braking than 100% weight transfer.

So...for simplicity sake let's choose one part...say the master cylinder...and work with that. Now put a small master cylinder on the motorcycle front brake and the rear wheel does not hold off the ground during maximum braking. Now put a slightly larger master cylinder on the motorcycle front brake and the rear wheel does not hold off the ground during maximum braking. Now go to the next size master cylinder on the motorcycle front brake and the rear wheel does hold off the ground during maximum braking. So now stay with that last master cylinder size on the motorcycle front brake. And ultimate braking has been achieved without front wheel lockup...

Now the motorcycle could have front-to-rear hydraulic brake proportioning such that at maximum braking the front brake gets 100% of the hydraulic force with the rear brake getting 0% of the hydraulic force...and now the motorcycle brake system is working like a car system. And the rear wheel is off the ground at maximum braking, the front wheel is not locked, and actually ultimate braking of 100% weight transfer has been achieved...on dry pavement.

But posters here have suggested that car brakes are so large that they will always lock-up the brakes...even in a straight line...and even on dry pavement...and in spite of correct front-to-rear hydraulic brake proportioning.

I'm saying that if the car brakes are about the right size...then with correct front-to-rear hydraulic brake proportioning...there will be very little problem with wheel lock-up...in a straight line...and on dry pavement...and without the use of ABS. Then on wet pavement the ABS is needed to avoid wheel lockup...because the brakes are sized for dry pavement.

Reply to
PolicySpy

If a motorcycle can lift its front wheel (100% weight transfer) under braking, then maximum braking force is achieved AFTER that has occurred. That's true no matter how you propotion braking force. If the front wheel doesn't lift and it is capable of lifting, you haven't provided maximum braking force.

This is true for cars as well, but most of them can't lift their rear wheels under braking.

That's right. Properly functioning car brakes can always lock up the wheels.

Brakes sized such that they could just barely lock up the wheels under dry conditions would be horribly undersized in practice.

Reply to
Matthew Russotto

And you are -- in every possible detail -- completely wrong.

Reply to
Alan Baker

gnu/linux...which version?

I REALLY don't like ABS. It 'works' at odd times, like if the car hits a bump with the brakes applied, etc. it's a real pain.

I like to have more control over my car than my car has over me...

Reply to
Hachiroku

False. You are correct in so far as that the shortest stopping distance is achieved with wheels that do not lock. You are also correct in that if the rear wheel of a motorcycle is pulled off the ground that said motorcycle is at or near the maximum deceleration that it can physically achieve. However, you are completely wrong that that is all the more stopping force that you can get out of the brakes on a typical car (or motorcycle.)

Think about it. My grandmother has to drive a car. If we set up the brakes in her car so that she can achieve maximum stopping force, then what happens when I, who outweigh her by about a factor of two and am proportionally (if not more so) stronger, drive the same vehicle? Of course the brakes will lock up long before I run out of leg strength.

It is the driver (or the ABS) that determines whether the wheels will lock or not, not the engineers that designed the brakes. The engineers design the brakes so that they are correctly proportioned and (hopefully) that a 5th or 10th percentile driver will still be able to panic stop successfully (that is, in other words, that a person of average size and strength will me more than able to force the wheels to lock if he pushes as hard as he can on the brake pedal.) In a good car, the engineers will also design the brakes to be fade resistant, such that a car can make repeated maximum deceleration stops from high speed without glazing the brake pads or causing them to outgas to a degree that stopping power is noticeably reduced. They will also design the brakes to be responsive to the driver, such that he can "threshold brake" successfully with a minimum of wheel lock.

nate

Reply to
Nate Nagel

And brakes so wimpy would probably heat soak after the first hard stop, and suddenly it's 1960 (again.) Although even by that date good brakes were available on *some* cars (Studebakers always had decent brakes after 1954; Buick was using aluminum drums on production cars in an attempt to shed heat faster, some imports were coming through with disc brakes by that point.)

nate

Reply to
Nate Nagel

Switching from a modernish 1996 car to a 1964 Commander OHV6 with stock brakes can be a lesson in automotiive advancement

Reply to
SeaWoe

We did an off road test with some Jeep TJ's with ABS after the first one following the old CJ7's and YJ's over a ravine top and down the other side had a losing argument with this tree you had to stop to avoid before a turn. The TJ owner just couldn't stop, his wheels wouldn't lock and he calmly just rammed the tree.

So the damage was done and he was convinced to try again. This time with the ABS fuses out. Well no surprise, he had no trouble at all stopping before the tree.

So he was a real good sport and as curious as we were so he put the fuses back in and tried again. Well, once again he calmly rolled into the tree, there was just no way to stop.

Note: If this tree hadn't been there, it was a sheer drop...

We have since done many more downhill dirt tests like that and now I always recommend if you plan on following me in my old CJ7 off road, you need to pull some fuses....

Thankfully my 2000 Cherokee doesn't have ABS, that might have been a deal breaker...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00 2000 Cherokee Sport 'New' frame and everything else in '09. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

I forgot about the six cylinder brakes. Can't remember the last time I drove a Stude six :)

nate

Reply to
N8N

Not at all. My ex managed to lock up the brakes on a motorcycle while learning to ride. Unfortunately it was my motorcycle, too.

--scott

Reply to
Scott Dorsey

Sure there can, you MORON.

Riddle me this: by your theory, a motorcycle will stop fastest if the rider leans forward to achieve 100% weight transfer sooner during braking.

So why do motorcycle riders (in the real world) shift their weight REARward to keep as much weight on the REAR wheel as possible? To allow them to fully use the braking power of both wheels!

You're claim that "maxiumum braking is defined as 100% weight transfer" carries about as much weight as a truckload of post-holes.

Reply to
Steve

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