Do you ever use your back brake?

[Nutsey]

I don't know what the correct way is, but almost always use both brakes equally. In fact in the current weather I couldn't use just one without crashing into stuff.

[Si]

Shifting your weight/COG forward increases your stopping distance.

thankyou, that's what i knew - but is edwards saying the opposite, am i misunderstanding, what's going on?

If you really want to improve your braking in all situations practice pushing forward with you feet on the pedals, this needs to be done so hard that you are now pulling hard on the bars.e

What it sounds like to me, is that Edwards icould be describing someone leaning their bum off the back of the saddle to get their weigh back. I 'pose the problem is that it doesn't say which direction the feet are pushing - if it's forward then it will move the rider backwards. A bit like unweighting the front wheel before going over a tree root, or going down a really steep descent. Not quite sure why one would need to pull on the bars - a firm grip, yes - but pulling could result in the rider moving in an arc, back and then up, thus pushing the weight back to the front during braking. If what's being described is unweighting the front wheel then it makes sense in that you want to keep your weight as far back as possible during heavy braking.

[blackbike]

Thanks for all the replies, though I'm not sure I'm any the wiser about the need for a rear brake.

I use a 105 dual pivot front brake on my two main bikes and they work so well I never need the rear brake. Even swooping fast downhill towards traffic lights in Knutsford my front brake gives me total control and a short stopping distance. On my tourer I have a tektro very deep drop dual pivot brake which is OK but not brilliant. Even on that bike I never use the rear brake as I allow longer to stop.

I use the rear brake a bit when off-road on my MTB.

[Si]

Thanks for all the replies, though I'm not sure I'm any the wiser about the need for a rear brake.

Oh, that's easy....you approach a busy T junction at speed, you start to squeeze the front brake and suddenly the lever is back at the handle and you've not slowed. Luckily, you've a rear brake too, and throwing your weight back and whacking the rear on stops you just before you end up hitting a fast moving car. On inspection the nipple on the front brake has come away from the cable inside the lever (where it's difficult to see it starting to fray without removal, and where you weren't expecting it to have any problems as it's less than six months old).

[meic]

I think that a change in the type of road surface that you ride on may increase the use of a back brake.
Reading all this debate about doing emergency stops on the front wheel alone makes me realise just how poor my road surfaces are in comparison to many other peoples.

Going over the handlebars! Fat chance around here. Front wheel gone from under you and sliding down the gravel and cowpat coated roads is what you get for too much right hand around here.

[Edwards]

My appologies for not replying sooner.
Si is correct in the unloading the front wheel. If you pust forwards with your feet to push your body backwards. The forward momentum is then taken by the feet not the hands.

[Ellieb]

I'm not sure I understand why I wouldn't use the back brake.It's there. Why not use it? It just seems to be a wee bit perverse to put all your braking action through one small contact patch whne you can put it through two. Obviously the amount you use the back depends on the conditions....

[339451trykit]

Use of the back brake is vital for control at slow speed when manovering in trafic or round obsitcals. If the front is used, good control is lost.
At speed under heavy braking, both brakes should be used. The front will do most of the stopping and the rear will help the control. I think 70% and 30% is somewhere near the optimum.
In cyclo cross the rear brake is vital. The front brake is fine on a dry course but it will quickly bring you down on anything slippery. Riding down steep embankments the rear brake will do all the controling and only gentle use of the front brake can be used, otherwise if the front wheel hits a bump and stops turning, its a trip over the bars. I have plenty have cross experience and found out the hard way a long time ago.

As for me now, I only have front brakes on my most frequently used machine so I have no choice. It's a racing trike with two V brakes.
This gets interesting when entering a turn and you suddenly decide you are going too fast. Applying lots of brake in a turn just makes the trike go straight on. The only real answer is to hang off the trike further and pray. Of course entering the turn at a sensible speed is the correct idea, but that gets boring!
Trykit

[Mick F]

Going back to Centre of Gravity if I may .......

I spent a little while this afternoon on my bike in the hall with our bathroom scales. By using a makeshift ramp I could roll onto the scales and weigh each wheel with me sitting normally. It wasn't easy!

In the end, I weighed me - don't ask - then only weighed the loaded front wheel. The rest of the weight was on the rear so adding weight of bike to weight of me and subtracting the loaded front wheel weight, I could work out the loaded rear wheel weight.

I stress this wasn't easy, and my figures may not be spot on, but what I found by weighing a few times was that my COG is just under 2.5"(60mm) behind the BB.

I don't know what that does for any figures that may come out for doing a header, but it was interesting nonetheless.

Also, I've been riding my rollers quite a bit over the last few days, and I tried a decelleration experiment.

By stopping pedalling at 20mph, my wheels stop in only 2 seconds. Just shows you the resistance of the rollers. Anyone want to care to say how far that would make my stopping distance on a real road and how it compares to real life stopping? I reckon it is PDQ!

[hubgearfreak]

20mph, my wheels stop in only 2 seconds.
Anyone want to care to say how far that would make my stopping distance

yes, 20mph is c.10ms. so 2 secs is c.20m

[drossall]

But you're only doing that speed at the start of the process...

[andrew_s]

20mph is 32kph = 32000/(60x60) = 8.9 m/s
Stopping distance would be 8.9m (assuming braking at a uniform rate for the whole 2 seconds).
8.9 m/s to zero in 2 sec is 0.45g, so you should be able to stop that quick when riding.

[hubgearfreak]

yes of course. my answer is double the correct one

[Mick F]

Yes but ......

Two things:
1. Can you stop in 2 seconds from 20mph? I don't think I can, but yet to trial.
2. My COG is further back than Andrew S showed in his excellent diagrams and all the calculations after that.

[Deckie]

On rollers the only thing to stop are the wheels, you don't need to take into account the momentum of the entire moving body so two seconds is unlikely as there will be much more energy for the brakes to deal with.

Having a thought - leaning forward when approaching/rounding corners downhill - this would load up the front wheel thereby increasing the friction with the road surface. Theoretically you could then take the corner at a higher speed... I won't try it on the tandem as Joules would not be impressed - she doesn't like going downhill at the best of times!

Thinking of which - tandem braking is entirely different as the rear wheel does not unload so both brakes are very effective. This is probably true of cargo bikes when loaded.