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Old 12th March 2011, 00:39   #31
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Default Re: ABS for bikes: How different from cars?

Quote:
Originally Posted by Sutripta View Post
In the meantime, lets move onto another aspect: How does one detect an about to lock wheel?
Can be done 2 ways.
1. rate of rise in brake fluid pressure. (I believe this is used for BA as well as threshold point for rapid-flash brake lights)
2. rate of decrease of d(alfa)/dt. Alfa being angular rotation (or angle rather)
3. both these in combination with ambient air temp, auto wipe, TCS signal etc

However, these are telling you that is 'mostly likely to lock' rather than 'will lock'

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Originally Posted by Sutripta View Post
^^^
Agreed. But two fingers are normally sufficient to lock up the front wheel.
Hmm...depends. really powerful brakes with crappy tires yes. Not on my 650. I would fly over the bars before it locks up.
Def not on a F.drum with mechanical actuation.

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Originally Posted by Sutripta View Post
^^^
What do you think of the (more conventional) TVS system?
Didn't get much from that video other than F+R wheel speed sensors and ABS pump. What else different about it?

Last edited by Mpower : 12th March 2011 at 02:20.
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Old 12th March 2011, 04:09   #32
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by SS-Traveller View Post
Sorry, but one query from a semi- AFA bikes are concerned: Are there any bikes at all, which have a single brake circuit transferring braking force applied at a single point, to both front and rear wheels (the way a car's braking system does)? If not, why not? And why, in any case, did motorcycle brakes continue to be operated by separate limbs, through the last century (is it just force of habit, or does riding dynamics have anything to do with it)?


Functionally, a single circuit system will not be ergonomically good. Bikes need your complete attention, and not always will your feet be free to be on the pedal. Imagine a situation where you are in a slope, and the bike is rolling backwards. The only way of stopping it is to apply brakes with your hand and keep both feet on the ground. Where as, if complete control is on hands, then also there is this issue of feet being able to exert more braking power than hands, hence high speed braking issues.

Also, as some one pointed out earlier, bikes, apart from India, are not only used solely as A-B traversing machine. It is also used for the fun factor. In my opinion, a single circuit brake system loses out on this. To extract max fun outta riding your bike, you have to be as much involving. You got to know where and what exactly your wheels are doing, and you need to be able to control them independently.
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Old 12th March 2011, 07:19   #33
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Default Re: ABS for bikes: How different from cars?

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For clarity, preface the discussion on BA with 'In an emergency situation'. Major percentage of ABS invocation is also under emergency braking conditions. Don't think we're mixing up ABS and BA. And the topic on BA came up to illustrate user behavior differing from what the engineers foresaw.
Yes, thats exactly BA does. In emergency braking condition or rather we should term as reflex action braking where you slam the brake, ABS will come into play, ECU has some logic to understand this and applies high amount of pressure on all wheels consistently till the vehicle stops or the driver withdraws the foot from the pedal. it is claimed that manually high percentage drives fails to apply the required pressure on pedal hence EBA was introduced.

As for bikes i think EBD should have more prominence as it will control the force on front and back tires. While hard braking the weight is transfered to front and more force is required to lock the front and same way less force at back. So single pedal brake technology will be expensive for standard bike hence two independent brake system is in place.
In case of combined braking as in Honda, there should be some brake biasing control which automatically increase the braking force to front as weight is transfered.

Last edited by v&v : 12th March 2011 at 07:30.
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Old 12th March 2011, 11:40   #34
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by v&v View Post
As for bikes i think EBD should have more prominence as it will control the force on front and back tires. While hard braking the weight is transfered to front and more force is required to lock the front and same way less force at back. So single pedal brake technology will be expensive for standard bike hence two independent brake system is in place.
In case of combined braking as in Honda, there should be some brake biasing control which automatically increase the braking force to front as weight is transfered.
The same will hold true for cars too. Weight transfer will be there towards the front end. I don't think this is the only reason why we have two separate circuits for braking in bikes. There must be some practical reasoning into this.
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Old 12th March 2011, 12:10   #35
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by ajman28 View Post
The same will hold true for cars too. Weight transfer will be there towards the front end. I don't think this is the only reason why we have two separate circuits for braking in bikes. There must be some practical reasoning into this.
Nope. this phenomenon is remarkably more in bikes due to CG and also the drivers body mass also exerting force on front wheels while braking and is less in regular cars. what you say may hold good for F1 or sports cars.

Last edited by v&v : 12th March 2011 at 12:24.
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Old 12th March 2011, 14:39   #36
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by ajman28 View Post

An ideal braking for the bike will be similar to the car, where both F & R brakes are applied with the same pressure. This is tricky since R brake is controlled by the foot where it is only natural that more pressure is applied. I think this is one of the main reasons why they set different "play" levels for the foot pedal brake and the hand lever brake. Also, in Indian bikes we find disc brake option mainly in the front. This makes the F brakes more efficient.

On a personal note, if I have to choose between a locked front wheel or a locked rear wheel on a bike, I would go for the locked rear wheel. It is easier to balance the vehicle when you have rear skid. You get some more time to react with a rear locked wheel as compared to a front lock.
wrong !, ideal brake distribution is 70% front and 30% rear , on sportsbikes its 80% front . see this article for more details Braking - xBhp.com : The Global Indian Biking Community
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Old 12th March 2011, 20:25   #37
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by Rollin' Thunda View Post
I think the linked combined braking sytem of Honda is essentially designed to be safer for newbies.
.....
but it might still create an over-dependance on the ABS to save you-- which might get you into problems if you later ride a non-ABS bike. Here too practicing emergency braking as above would help avoid getting into bad habits.
Interesting PoV.
Considering Honda's C-ABS debuted on their premium offerings, and are still offered on those, I would think there is more to it than 'saving newbies'.

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Originally Posted by ajman28 View Post
An ideal braking for the bike will be similar to the car, where both F & R brakes are applied with the same pressure.
Not really. Same pressure, different braking forces. By design.



Quote:
Originally Posted by Mpower View Post
Can be done 2 ways.
1. rate of rise in brake fluid pressure. (I believe this is used for BA as well as threshold point for rapid-flash brake lights)
2. rate of decrease of d(alfa)/dt. Alfa being angular rotation (or angle rather)
3. both these in combination with ambient air temp, auto wipe, TCS signal etc
I think you cant derive without having a value for mu. Which varies.


Hmm...depends. really powerful brakes with crappy tires yes. Not on my 650. I would fly over the bars before it locks up.
But what if you were superglued to your seat?
Quote:
Originally Posted by dhanushs View Post
Functionally, a single circuit system will not be ergonomically good.
.....
To extract max fun outta riding your bike, you have to be as much involving. You got to know where and what exactly your wheels are doing, and you need to be able to control them independently.
Interesting PoV. Food for thought.

Quote:
Originally Posted by Mr. Nobody View Post
wrong !, ideal brake distribution is 70% front and 30% rear , on sportsbikes its 80% front .
What does the percentage refer to?

Guys,
When I was talking about how to detect a wheel about to lock up, what I had in mind was how to distinguish it from coming to a normal stop.

Why are no experts chipping in with riding techniques. Because would also like to discuss things like braking during cornering, trail braking etc. Maybe that will also clear up the air on why bikes have (and persisted with) two separate brake circuits.

No comments on the Moto Guzzis?

Regards
Sutripta
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Old 12th March 2011, 22:33   #38
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by Sutripta View Post
Why are no experts chipping in with riding techniques. Because would also like to discuss things like braking during cornering, trail braking etc.
Panic brake is always in a straight line. I only feather the brakes when im leaned over'

Quote:
Originally Posted by Sutripta View Post
Why are no experts chipping in
OK thats it, now myself, dhanush, nobody, vv, ajman are all offended and disappointed
Quote:
Originally Posted by Sutripta View Post
When I was talking about how to detect a wheel about to lock up, what I had in mind was how to distinguish it from coming to a normal stop
but what do you do with that info? Run in energy save mode?? ABS systems in cars run on CAN networks that react vv.quickly.

Quote:
I think you cant derive without having a value for mu. Which varies
Yes you're right. But this is approximate calculation anyway. Like I said, you can use things like ambient air temp, rain sensor/TCS input to apply a correction factor. (generally speaking)

Last edited by Mpower : 12th March 2011 at 22:36.
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Old 12th March 2011, 23:15   #39
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by Mpower View Post
Panic brake is always in a straight line. I only feather the brakes when im leaned over'
That's what we are all taught. (But trail braking is the hot topic nowadays.)

OK thats it, now myself, dhanush, nobody, vv, ajman are all offended and disappointed
I'll join you! Actually, I've not found a definitive list put up by anyone. Could it be because we are all car guys who bike for fun.
On a more serious note, sports bikes are all about using the front brakes. That is the expected behavior of the rider. In this scenario, why C-ABS? I'm talking about it on Honda's litre class.


but what do you do with that info? Run in energy save mode?? ABS systems in cars run on CAN networks that react vv.quickly.
We do have to stop.
What I'm wanting is a list which goes like this:
In this situation, brake like this because of this.
To this I want to add 'and therefore, for best results, the ABS system should respond like this.

Regards
Sutripta
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Old 12th March 2011, 23:28   #40
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Default Re: ABS for bikes: How different from cars?

I was going through the link which Mr. Nobody had posted and came across the following statement in the very first post in the link:

Quote:
Does braking, throttle control, body position also change on the track and on the street?
NO...whatever you learn at the track are simply the most effective tools to handle your bike and to keep it stable. And why would you not want to keep the bike stable on the streets. So not using the rear on the streets isnt so weird because only racers do that at the tracks.

Using the rear is too much of a trouble with too huge a risk with minimal rewards. Hence the common advice of ignoring it. You can ofcourse use it as much as you want. You will however be better off focussing more on the front as in 9 out of 10 times the front is more than sufficient to stop your bike from any speeds.

5. The rewards of using the rear brake are minimal and the risks associated are insane. If you want that ounce of more braking power you have to use the rear brake. That ounce is what I chose to ignore.
Unquote.



Now I am a little confused. I cannot agree completely with what is stated there. Aren't we supposed to use both F & R brakes for best performance? Isn't that supposed to be the safest method too?

Last edited by ajman28 : 12th March 2011 at 23:33. Reason: Typo
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Old 12th March 2011, 23:52   #41
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Default Re: ABS for bikes: How different from cars?

Quote:
Originally Posted by Sutripta View Post


What does the percentage refer to?

Guys,
When I was talking about how to detect a wheel about to lock up, what I had in mind was how to distinguish it from coming to a normal stop.

Why are no experts chipping in with riding techniques. Because would also like to discuss things like braking during cornering, trail braking etc. Maybe that will also clear up the air on why bikes have (and persisted with) two separate brake circuits.

No comments on the Moto Guzzis?

Regards
Sutripta
70/30 % means that 70% braking is done by front and rest on rear on most indian bikes . on sportsbikes rear wheel does not have much weight on it so its 80 % front . when you brake on bikes quite a lot of weight is transferred on the front tire and we can press press the front disk way harder than rear and not fear wheel locking up as traction increases a lot when the weight is transferred there . the front tire is also thinner than rear one but the weight transfer is what make it have lot more grip than rear on braking .having a pillion on bike also changes braking dynamics , you get a lot more weight on rear so you can brake harder on the rear wheel .

trail braking is when you brake even while taking a turn , it uses only rear brake , never use front brake on turn . the rear brake is used lesser and lesser as you lean more as tire contact patch decreses on lean . generally for new riders its recommended to do all braking before taking turn .

when front tire locks up , it usually wipeout time ! its is very quick and gives nearly no time to react and unlike rear tire where you can easily lock it up and slide it around for fun .

@ajman28 - indian riders especially most commuters do not have good braking technique . they use too much rear brake and fear using the disk .
braking should be majorly with front while using rear to stabilise bike . on indian roads that are usually covered with gravel etc we have to use rear brakes but on good clean tarmac its the front thats more significant than rear . yes use both rear and front .

Last edited by Mr. Nobody : 12th March 2011 at 23:56.
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Old 13th March 2011, 01:08   #42
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Default Re: ABS for bikes: How different from cars?

Quote:
Originally Posted by Sutripta View Post
Because would also like to discuss things like braking during cornering, trail braking etc.
Quote:
Originally Posted by Mpower View Post
Panic brake is always in a straight line. I only feather the brakes when im leaned over'
Well, the real purpose of ABS, both in Cars and Bikes, is to aid steerabilty. So, ABS is mainly intended to aid hard(panic?) braking under cornering.

In cars, steering maneuvers is handled mainly by the the position of wheels (steers in the direction it is pointed to). There is not much driver can do. But in bikes, not only the direction of the front wheel, but the angle of lean is of utmost importance. At a speed, you just cant turn your bike even if the wheels are NOT locked. You need to lean your bike(change in CG), so that the resultant centrifugal forces are balanced, and you keep turning along circumference of the curve.

OK, if we are talking low speeds, then also, while cornering, for the front/rear wheel to skid(and lose steerability), the wheel need not necessarily lock up, it just needs to lose traction, which is very easy of you don't position the machine properly.

In order to achieve perfect braking while cornering, the least you can have apart from 'skill' is, independent control over your wheels. There are times when the front wheel loses traction before the rear, and vice versa. and in those times, we need to individually release/apply brakes.

The front biased, single circuit (60/40 or 70/30) braking, works for cars, but not for bikes. Yes, if its on a straight line always.

Also, ABS in bikes, do they aid steerability as much as in cars?.

IMO, it just helps us 'Indians' who are so dependent on back brakes, from fishtailing. Unless, we are made to drive on situations like ~shiny ceramics, with water as shown in the promo's.
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Old 13th March 2011, 06:50   #43
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Default Re: ABS for bikes: How different from cars?

Quote:
What I'm wanting is a list which goes like this:
In this situation, brake like this because of this.
To this I want to add 'and therefore, for best results, the ABS system should respond like this.

Regards
Sutripta
Condition - 1
Wet road condition/slippery road - This is one condition where ABS will come in to play most whether in straight line or cornering.

Condition - 2
Sudden/Reflex/Panic Braking - ABS & BA & EBD what ever techs available comes into play to bring the car/bike into dead stop without locking wheels. it is detected by sudden bang on brake paddle, which will trigger all the above.

Condition - 3
Driving cars/bikes at higher speeds , here is where ABS assists in better handling, cornering .
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Old 13th March 2011, 18:55   #44
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by Mr. Nobody View Post
70/30 % means that 70% braking is done by front and rest on rear on most indian bikes .
Needs a qualifier to the effect that at maximum deceleration, these are the contributions of each tyre.

Quote:
Originally Posted by v&v View Post
Condition - 1
.....
handling, cornering .
Could you please elaborate on it. As in 'in this condition, I would brake like .... because the laws of physics say ......

Quote:
Originally Posted by dhanushs View Post
Well, the real purpose of ABS, both in Cars and Bikes, is to aid steerabilty. So, ABS is mainly intended to aid hard(panic?) braking under cornering.
.....
Also, ABS in bikes, do they aid steerability as much as in cars?.
The first statement is debatable.

In a car, locked wheel => A) increase in stopping distance from best attainable (approx 130%), and B) Loss of steerability.
On a bike, locked wheel => A) increase in stopping distance from best attainable, and B) Wipeout

The accepted practice on bikes is no braking while turning. Why?

AFAIK, the mechanics of turning in a car and a bike are very different. (I think it requires a very thorough discussion. In a separate thread). In a car, we will have steering control even under fairly heave braking. (Here we are talking of the case where otherwise you would have control over the vehicle. The only extra force you are adding now is that due to braking. If you enter a turn too fast, well you know the rest.)
On a bike, the amount of braking force you can extract during cornering before a wipeout is extremely limited. The purpose of ABS on a bike I guess would be to keep you upright, and in control during heavy braking.

Since ABS can pressurise/ depressurise the line, should bike manufacturers put in accelerometers/ gyro, and disable (or otherwise reduce) braking during cornering. Can we have a button on the handlebar called 'trail brake', which I punch when entering a corner, allowing me to emulate my biking heroes.

Regards
Sutripta
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Old 14th March 2011, 09:26   #45
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Default Re: ABS for bikes: How different from cars?

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Originally Posted by Leepower View Post
Just check out this site: Saferide claims:


Saferide Motorcycle Antilock Braking System (briefly referred to as
My point is are they misleading customers by claiming that they are selling ABS like the one on Honda CBR 250R????
And they are selling it only for around Rs 1200 bucks, that speaks for the quality -- Honda is charging 20K more for CBR 250R with ABS???
And ABS as far as my limited knowledge goes only works if you have disc brakes on the front and rear, right??? So to install it on my Bullet 350, I'll have to first install rear discs. Correct me if I am wrong.
1. It is a misnomer to think that quality is always directly proportional to the cost of product. Now a days, good proxy sensors, solenoids and electronics/ software algorithms required for ABS do not cost much.
2. My son and his friends completed a B Tech project - an equipment which automatically stops the bike engine when stand still for more than 30 sec, say, at a signal, and restarts by a flicker on throttle. You know, it costs only Rs 1500. Soon this feature may appear on bikes with a fancy company price tag.
3. As regards disc brakes, I do not think disc brakes are must. If so, how is it working in cars with front discs and rear drums?
Regds
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