Author Topic: Braking stresses  (Read 19251 times)

TonySmith

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Braking stresses
« on: January 26, 2005, 10:47:24 AM »
In dry weather on good roads I usually only use my front brake. In wet weather or if mud, gravel etc. is present I'll use both brakes fairly evenly. With modern brakes the maximum braking force achievable on a bicycle is limited by the high centre of mass and short wheelbase causing the rider to go over the bars, not by braking power or traction.
 While there's no doubting the front only approach is best for an emergency stop I wonder if it should be used all the time, given that most brake applications are rather lighter.
 From a wear and tear viewpoint on the brake levers, cables, blocks and rims it should even out - only using the front will double the rate of wear at the front while the back will last forever (compared to 50/50 use) but what about the fact that the entire stopping force is passed throught the forks and headset? Also, is this suitable for a laden bike where the forces are greater but the weight of the rear end is increased? And what about the increased heating of just the front rim?

 

Colin

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Re: Braking stresses
« Reply #1 on: January 27, 2005, 09:46:30 PM »
In the 1960s, I was advised at primary school, by a visiting policeman, to always use both brakes together and apply the front brake slightly before the rear one. I have followed that advice since. When braking strongly, the front brake will be the more effecive, due to weight transfer onto that wheel. That's why cars, motorcycles (and some bicycles) have more powerful brakes at the front and why (like bicycle wheel rims) their front brake pads suffer more wear than the rear. So the front brake and wheel rim will normally suffer more wear (even if you try to apply the braking selection 50/50.

Colin
 

Pedaldog

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Re: Braking stresses
« Reply #2 on: January 28, 2005, 06:59:32 PM »
I second what Colin says. I was taught the same thing when learning to ride my motorbikes at the age of eight years and I have used it for the last 35 years with (Mostly!) success and confidence.
 

marcg

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Re: Braking stresses
« Reply #3 on: January 29, 2005, 06:31:04 AM »
I remember in the distant past - either with motorcycle training or bicycle training, I'm not sure which, being taught - always front brake first follwed by the rear and then 50/50 in the dry (I think) and a different percentage in the wet.  I can't remember the wet pecentage.  Maybe 60/40.
You never hear that now.  When I took my big bike test a couple of years ago there was no mention of this kind of thing.
 

luceberg

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Re: Braking stresses
« Reply #4 on: January 30, 2005, 12:25:29 AM »
Well, I tend to favour the rear brake, to no ill effect over the years, except my rear rims wear out first. Mostly used for speed control rather than stopping.
 Applying the front brake puts weight on the front wheel and proportionally away from the rear,so the rear wheel has more grip and hence more power when applied on it's own. Touring loads on the rear increase grip further.
 To stop quickly, I would put my weight as far back as possible and apply both brakes about the same.
 

ahconway

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Re: Braking stresses
« Reply #5 on: January 30, 2005, 07:03:09 PM »
I've always used both brakes, more or less equally.

The most important thing from my point of view is shifting your weight back when braking hard. If I know I need to slow down fast, I'll sit out of the saddle slightly and push my bum off the back of the saddle as I brake. That ensures that I don't end up going over the bars.

I was out in the wet for the first time today with my new Raven Tour and Pasela Tourguards and was surprised to discover my rear wheel locking up with hard braking on tarmac. I ended up in a worrying slide a couple times today, but I got a handle on the situation eventually. Never had that problem with Marathons or Specialized Nimbus Armadillos...
 

TonySmith

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Re: Braking stresses
« Reply #6 on: February 01, 2005, 02:19:07 PM »
Regardless of tyre choice you'll always get the rear wheel to lock if you use the rear brake when braking hard, due to it having little or no weight on it. Try a few emergency stops on a good, dry road using both brakes and a few using just the front. With practice you'll stop faster with just the front and avoid the problem of the back wheel locking up. Moving back in the saddle will help but to make enough difference you'll probably have to sit on the rear rack.
 

brevetpilot

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Re: Braking stresses
« Reply #7 on: April 07, 2005, 05:33:13 PM »
I think Colin has it about right. I think John Franklin's Cyclecraft book has a great section on this, but I don't have my copy to hand. I know I read something on Sheldon Brown's site about the importance of condition of the front tyre/brake to the overall control and safety of a cycle.

He makes some good observations regarding tyre rotation (to even out wear). Basically said, if you insist on doing it, then put the new tyre on the front and the old on the rear.
 

rogerzilla

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Re: Braking stresses
« Reply #8 on: June 14, 2005, 07:03:57 PM »
The back brake really wears out first because it's sprayed with gritty water from the front wheel.  Nothing to do with using it more.
 

matthews2398

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Re: Braking stresses
« Reply #9 on: December 18, 2006, 09:44:29 PM »
A very interesting problem for a cyclist and I must confess that my Raven Tour fitted with Magura 33 rim brakes stops very quickly and reliably with front brakes first applied.

A number of years ago it was discovered that applying the rear brakes first on an articulated vehicle made the rig unstable and caused it to jackknife. Going back to the drawing board they realised that the way to keep the vehicle stable was to apply progressively the front brakes and then the rear ones. This did not get rid of the problem completely but it proved a much better solution than rear brakes first