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Disk brakes and quick-release: a dangerous combination?
A rider's research shows that braking forces can eject wheels from the dropouts. Read this and check your setup...
Japan-based Scottish MTB rider James Annan has uncovered what could be a serious problem for MTB riders who use disk brakes with quick-release wheels:
http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html
We'll be doing a fuller article on this subject next issue - but for now I strongly suggest that all riders and manufacturers read and inwardly digest that website. The problem does appear to be real and the arguments well-founded, and James has been backed by authorities including Chris Juden of the CTC, Peter Eland of Velo Vision, well-known MTB journalist (now manufacturer) Brant Richards and Jobst Brant, author of The Bicycle Wheel.
Manufacturers of brakes and forks have been wary about responding so far. The issue has only in the last day or so been raised in a high-profile way on bike trade websites such as BikeBiz so teh industry has yet to decide how it'll be handled.
So for now, check your setup and ride safe.
Posted on 13 May 2003
Your comments ...| From: Gerry Leach ([email protected]) on 13 May 2003 |
Looks to me as if the brake caliper should be in front of the fork. Then the reaction force will be upwards, forcing the wheel into the dropout slot.
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| From: Ralf Grosser ([email protected]) on 14 May 2003 |
I fully agree, that under the discribed conditions callipers and anker should be placed in front and not behind the fork.
Its a matter of verz simple mechanics, once you think about it.
Early diskbrakes on Motorcyles also had the calliper and anker in front and not behind.
Quite a few motorcycles with drumbrakes also had the anker on the frontside of the Fork.
Prehaps they only moved things behind the fork when materials and components got stronger.
Ralf |
| From: Ben - Kinetics ([email protected]) on 14 May 2003 |
| It's probably on the back of the fork just because that looks neater. The earliest disc brake I have - a very early Hope cable one - has the caliper attached to the hub spindle by an arm, and it just rests against the fork leg. This won't have this problem, of course... |
| From: Ralf Grosser ([email protected]) on 14 May 2003 |
Today I went into a motorcycle shop and had a look at forks.
Most newer motorcycles have forks that are closed at the end.
Or are clamped shut from below with a U piece.
On most the wheel can only be removed by slipping the axle out sideways.
Some older Harley Davidsons and BMW motorcycles have the caliper mounted in front of the fork, or have the drumbrake either anchored in the center, or in front of the fork.
With quick release axles keep in mind, that they were patented 50 years ago for racing cycles.
Thy work quite well fore this purpose as long as you tighten the lever correctly.
They never were intended for use with diskbrakes, and if you anchor the Caliper behind the fork, you do get a downward momentum, that I presume can cause the axle to eject from the forks dropouts.
BTW at Spezi I did notice, some folding bikes and recumbents use a V-Brake mounted behind the fork.
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| From: andy scaife ([email protected]) on 15 May 2003 |
At least some good appears to be coming from this. What posessed mfrs to try this barmy config anyway? Showroom appeal probably ("Look, this one's got discs" "Yeah, but I wanted Quick releases cos it's what racers have") For heaven's sake, they'll be making off-road bikes with exposed transmissions next!
I read somewhere that makers began putting caslipers behind the forks to protect them from tree-branch damage on trails. Also the braking force will push the caliper into the fork leg rather than trying to rip it off forwards. All quite sound, and the ejection drawback doesn't apply if you bolt the wheel in properly instead of using QRs. I too have one of those early Hope cable jobs like Ben's, which seems very secure to me. I also have a recumbent with a rear-mounted v-brake which to me just seemed to look more 'correct' from an engineering point of view. Again, forces pushing it onto its mount instead of trying to rip it off. |
| From: Ralf Grosser (Buzz [email protected]) on 15 May 2003 |
Haveing a brake Mounted behind the fork, like a Hydro oe V-Brake, will give you some force downward, but how much depends on how low the brake is anchored. This means, on a large wheel not very much, but the lower you get the more downward leverage you will have.
The most being of course on a diskbrake.
I also would have assumed that a brake mounted behind the fork would be best, but the problem that James Annan has brought to our attention, has been quite an eye opener.
Sofare I have only had diskbrakes on motorbikes, wher they are tried and proven, and do not have quickreleases.
The day you stop learning something new is the day you stop liveing. |
| From: Dave Kahn ([email protected]) on 16 May 2003 |
James has done an excellent job bringing this problem to light and is to be congratulated. He has described 2 separate mechanisms - 1 for the force ejecting the wheel and 1 for the quick release coming undone, which is needs to happen before it can be pulled past the "lawyer lips". There is enough real world evidence for this problem to be taken seriously, including Russ Pinder's recent serious accident.
Incidentally the ostensible reason for siting the caliper behind the fork rather than in front of it is to keep its weight closer to the steering axis thus minimising any adverse effect on the handling. |
| From: Ralf Grosser ([email protected]) on 17 May 2003 |
I do not believe, that placing the brakecaliper in front of most Telescopic forks will have that much of an adverse effect on handling.
The handling of suspended Maintain Bikes is a laugh to begin with.
Most Mountain Bikes with their 26 inch wheels have too much unstrung weight allready, so a little more or less in front will not really be noticed.
I do not believe, that placing the brake in front of most Telescopic forks will have that much of an adverse effect on handling.
The handling of suspended Maintain Bikes is a laugh to begin with.
Most Mountain Bikes with their 26 inch wheels have too much unstrung weight to begin with, so that a little more or less in front will not really be noticed.
The last few years, we have seen an industry go wild, trying to convince the consumers, that they need bicycles with components bigger then what we had on mopeds 20years ago. A bicycle has become something ridiculous, that looks like a Motorcycle with pedals.
The problem is, that if you want to build something that looks like a motorcycle, looks is not all you need to copy.
Do your homework, and also have a look, why some solutions on motorcycles are the way they are.
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| From: Ralf Grosser ([email protected]) on 17 May 2003 |
I do not believe, that placing the brakecaliper in front of most Telescopic forks will have that much of an adverse effect on handling.
The handling of suspended Maintain Bikes is a laugh to begin with.
Most Mountain Bikes with their 26 inch wheels have too much unsprung weight already, so a little more or less in front will not really be noticed.
The last few years, we have seen an industry go wild, trying to convince the consumers, that they need bicycles with components bigger then what we had on mopeds 20years ago. A bicycle has become something ridiculous, that looks like a Motorcycle with pedals.
The problem is, that if you want to build something that looks like a motorcycle, looks is not all you need to copy.
Do your homework, and also have a look, why some solutions on motorcycles are the way they are.
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