The friendly "dumb" bike questions thread

[SpeckledJim]

RizzoTheRat said:

Surely ABS should be able to detect if the rear wheel has lifted without additional sensors. ABS would detect the rear wheel has locked, release the brake, and then if the wheel's lifted it wouldn't spin back up to the same speed as the front wheel.

Rider might not be using the back brake though.

[black-k1]

TheInternet said:

anonymous said:

[redacted]

Is the risk of lifting the back wheel not an issue with ABS? It is something I've wondered despite never coming close to doing it. I was under the impression that some bikes can detect rear lifting, but thought that others will allow you to go straight over the handlebars if you try hard enough, but I've no idea how hard that is to do.

ETA: The post above suggests you can reach maximum braking on some bikes without flipping.

Indeed you can easily reach max front wheel grip before lifting the rear. At the extreme a chopper with very long forks will never lift the rear. As a result, braking on choppers, even on a good, dry surface, will involve a very significant amount of rear brake and a lot less front.

Bikes like the K1?00S and the Honda Blackbird have a long enough wheelbase with a low enough C of G that they'd need a surface such as ShellGrip to have any chance of getting the rear wheel off the ground before the front locks.

[Krikkit]

SpeckledJim said:

RizzoTheRat said:

Surely ABS should be able to detect if the rear wheel has lifted without additional sensors. ABS would detect the rear wheel has locked, release the brake, and then if the wheel's lifted it wouldn't spin back up to the same speed as the front wheel.

Rider might not be using the back brake though.

Correct - if you leave the rear brake alone it'll use the IMU to know the orientation of the bike.

[black-k1]

Krikkit said:

SpeckledJim said:

RizzoTheRat said:

Surely ABS should be able to detect if the rear wheel has lifted without additional sensors. ABS would detect the rear wheel has locked, release the brake, and then if the wheel's lifted it wouldn't spin back up to the same speed as the front wheel.

Rider might not be using the back brake though.

Correct - if you leave the rear brake alone it'll use the IMU to know the orientation of the bike.

... but don't leave the rear brake alone! It could save your life.

[TheInternet]

black-k1 said:

Indeed you can easily reach max front wheel grip before lifting the rear. At the extreme a chopper with very long forks will never lift the rear. As a result, braking on choppers, even on a good, dry surface, will involve a very significant amount of rear brake and a lot less front.

Bikes like the K1?00S and the Honda Blackbird have a long enough wheelbase with a low enough C of G that they'd need a surface such as ShellGrip to have any chance of getting the rear wheel off the ground before the front locks.

Thanks. I'm pretty sure my very middling naked doesn't have an IMU so in theory is susceptible to lifting.

[Prof Prolapse]

anonymous said:

[redacted]

Whilst I accept the rear brake does very little on some bikes, none if the rear wheel is in the air, it does do some of the braking. I remember reading (but not confident of the accuracy of the source) that the front brake allegedly does 75%-90% of the braking.

So by ignoring the rear brake, potentially you're losing between 10%-25% of your braking ability. Which presumably translates to much longer stopping distances.

Personally I use the rear brake, but I do accept it's role is limited.

[black-k1]

anonymous said:

[redacted]

I think you are wrong with regards to the use of the rear brake and scientific research done by Aprilia also thinks you're wrong, and that research was done using sports bikes.

Scientific paper: On optimal motorcycle braking

Matteo Cornoa , Sergio Matteo Savaresia,, Mara Tanellia , Luca Fabbrib

a Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano, Italy b Piaggio Group—Aprilia Brand, Via Galileo Galilei, 1, 30033 Noale, Venice, Italy

Received 21 March 2007; accepted 1 August 2007 Available online 21 September 2007

http://www.elsevierscitech.com/pdfs/CEP_Corno.pdf

Some interesting details in section 3. The paragraph of interest says:

This section is concluded by observing that in the long 300-80 km/h braking maneuver, the difference of performance is very large, about 300 ms. This difference is largely due to the fact that the ‘‘traction’’ torque has been replaced by a ‘‘braking’’ torque at the rear wheel Although the braking torque at the rear wheel is rather small compared to the front-wheel one, on a strong braking maneuver the effect of the rear brake can be clearly appreciated. This is true, in particular, if the front-brake controller is able to maintain a small but non-zero load on the rear tire.

Note: My bold

So, even in the best conditions research by Aprilia says the rear brake will be of benefit.

BUT

More importantly, what we do when we are braking during normal time is "training" the muscle memory so that when we suddenly encounter an unplanned, unexpected event, we react instinctively. When such unplanned and unexpected events happen, we can not count on the surface being perfect thus we can not count on the ability to use enough front brake to lift the rear. Damp, gravel, mud, potholes, etc. will all reduce down the amount of work the front wheel can do, thus extending the stopping distance from it's theoretical minimum. In such circumstances, it's quite possible that increase in the stopping distance may be the difference between having an accident and not having an accident. as such, the additional stopping power offered by the rear brake may just save your skin.

ADDITIONALLY

As all new bike are now fitted with ABS there is no negative to using the rear brake. If there really is no rear wheel grip (and be honest, how often does that really happen on the road?) then the ABS will automatically remove the rear brake anyway. If the ABS doesn't kick in then the additional braking effort from the rear WILL help you stop quicker.

[black-k1]

Prof Prolapse said:

Whilst I accept the rear brake does very little on some bikes, none if the rear wheel is in the air, it does do some of the braking. I remember reading (but not confident of the accuracy of the source) that the front brake allegedly does 75%-90% of the braking.

So by ignoring the rear brake, potentially you're losing between 10%-25% of your braking ability. Which presumably translates to much longer stopping distances.

Personally I use the rear brake, but I do accept it's role is limited.

It's role is limited in good conditions but it's role increases as conditions worsen. In the worst possible conditions (ice for example) you'd only use the rear.

[Bob_Defly]

black-k1 said:

I think you are wrong with regards to the use of the rear brake and scientific research done by Aprilia also thinks you're wrong, and that research was done using sports bikes.

I thought the rear brake didn't work on Aprilias anyway?

[Krikkit]

On a bike with ABS I'd use the RB, on my current one without I wouldn't even think about it in an emergency - I'd be concentrating on getting the maximum out of the front brake without going over the bars.

[Prof Prolapse]

black-k1 said:

It's role is limited in good conditions but it's role increases as conditions worsen. In the worst possible conditions (ice for example) you'd only use the rear.

Good to know as that's how I use mine.

On the adventure bike I used the rear more in general, presumably the weight distribution is a factor, in the wet it's about 50/50.

When I rode in the snow (never again), I only used the rear or engine braking (two cylinder helped).

So yeah, agree entirely with what you say.

[KTMsm]

black-k1 said:

More importantly, what we do when we are braking during normal time is "training" the muscle memory so that when we suddenly encounter an unplanned, unexpected event, we react instinctively.

I did wonder as a relatively new road rider whether I would be fast enough to brake in an emergency situation - thankfully, it was an automatic reaction.

[mike-v2tmf]

A chap I worked for many years ago used to open the bleed nipple on the rear brake of his bike and allow some air to enter the rear brake system to "soften" the effect of the brake in the event of a panic brake situation, I admit to adopting this too at the time * though not now

[DirtyHarley]

Just a side bar on the brake talk - on cruisers the rear brake is normally quite useful as there is still a fair bit of weight at centre/ towards rear.

I will however join the club of singing the praises of an ABS equipped bike - my current bike is my first fitted with it, and I am pretty sure it's saved me closely inspecting the floor twice in the 2 and a bit years I've had it; one in an emergency situation on a motorway and another on muddy sludge.

The only thing that annoys me a little with it is if you hit a pothole whilst braking, occasionally I'll get the pulsing as if the ABS is kicking in despite the front being firmly planted, easily fixed by easing up and reapplying, but brakes the concentration a little (a pun - I'm getting to be like BN now!)

[vindaloo79]

SpeckledJim said:

ETA: just realised I said 'retain directional authority' when I should have said 'steer'.

What a divvy.

[Zarco]

Are brake lever guards compulsory on track days?

I've got my first track day at Silverstone on 28th. I've bought a R&G lever guard but can't work out how to fit it. I'd rather not bother now!

Quick Google says MSV and some other providers insist upon lever guards now. This isn't an MSV day though. Terms and conditions on Silverstone website don't specify it (I have sent them an email for clarification).

Pictures of my predicament:

[trickywoo]

Zarco said:

Are brake lever guards compulsory on track days?

I've got my first track day at Silverstone on 28th. I've bought a R&G lever guard but can't work out how to fit it. I'd rather not bother now!

I’d be very surprised if they are. My experience of track days is that the Wild West was tamer and safer.

Unless your bike is too loud they don’t care about it. It could only have pads in one caliper and they wouldn’t know.

I’d say if someone gets close enough to you on a track day to warrant a brake lever guard that is the least of your worries.

[Zarco]

Have you done one recently?

My sentiments exactly regarding the possible benefit a lever guard will actually give me.

[Onelastattempt]

Zarco said:

Are brake lever guards compulsory on track days?

I've got my first track day at Silverstone on 28th. I've bought a R&G lever guard but can't work out how to fit it. I'd rather not bother now!

Quick Google says MSV and some other providers insist upon lever guards now. This isn't an MSV day though. Terms and conditions on Silverstone website don't specify it (I have sent them an email for clarification).

Pictures of my predicament:

Don't you just unbolt the original bar end and bolt the lever guard in its place?

[Zarco]

Sadly not. Original bar end has an M8 bolt. Lever guard comes with M6 and an insert.

How to get the insert inside the bar tube is what baffles me.

R&G website stated it would be compatible with my bike and take 'seconds'