Author Topic: Disc brakes - rear only - bad idea?  (Read 3833 times)

Tiger

Disc brakes - rear only - bad idea?
« on: February 17, 2009, 10:54:04 am »
The Fujin is a lovely bike but the brakes leave a lot to be desired. Front is just about effective but the rear brake does not seem to actually do anything. I have tried recabling, noodles, and all manner of blocks.
I suspect that it is a basic issue of wheels size/speed/rider weight Vs fairly light caliper brakes designed for a road bike. At speed or on a hill the bike is not really stoppable without whiteknuckling the brakes and there is no emergency stop available.
In contrac=st the speedmachine with  Hope hydraulic brakes is completely stoppable at any speed.
I just got a new wheel from Challeneg and it has flange for a disc (as well as a braking rim). I am thus toying with the idea of replacing the rim brake with a Hope hydraulic rear disc.
BUT - will a good rear brake, with its own different lever and modulation etc be a liability? Anyone got experience?
Also - the rear dropouts are open and no lawyerlips present - does that make a disc a danger?

LittleWheelsandBig

  • Whimsy Rider
Re: Disc brakes - rear only - bad idea?
« Reply #1 on: February 17, 2009, 11:06:17 am »
Wheel size makes very little difference in rim brake performance, particularly with skinny tyres.
Wheel meet again, don't know where, don't know when...

Tiger

Re: Disc brakes - rear only - bad idea?
« Reply #2 on: February 17, 2009, 11:11:48 am »
It is also a longish cable run to the rear - and might be the lever doesn't generate a lot of pressure.  It is quite odd though - one can squeeze really hard but still not feel much braking effect. Have never actually skidded the rear - except on a slimy patch on a camber which had me off on a milisecond.

LittleWheelsandBig

  • Whimsy Rider
Re: Disc brakes - rear only - bad idea?
« Reply #3 on: February 17, 2009, 11:16:30 am »
Do you want a really good rear brake then?
Wheel meet again, don't know where, don't know when...

Tiger

Re: Disc brakes - rear only - bad idea?
« Reply #4 on: February 17, 2009, 11:37:33 am »
That was why I was asking the question - to see if any other darksiders had experience of a 'reare disk only' and if it was a good idea. Before I go and spend a load of cash on it.
The front can't take disc brakes otherwise I think I would have fitted them.
I have never heard of anyine having a really strong rear brake - and I can see it might actually be an issue. On the other hand some stronger drag at the back might be a useful safety feature.
As said - anyone out there got some useful experience on this?

bikenerd

Re: Disc brakes - rear only - bad idea?
« Reply #5 on: February 17, 2009, 12:05:00 pm »
How about a Magura Hydraulic rim brake?  Should cure the problem with friction in the long cable run.
I'm about to replace the brakes on my Moulton (also little wheels!) with Magura HS33s as the rear one has a very convoluted path and barely works at all.

Re: Disc brakes - rear only - bad idea?
« Reply #6 on: February 17, 2009, 12:13:01 pm »
As said - anyone out there got some useful experience on this?

Not exactly. My Fujin has only ever been used for racing and day rides, and I'm a lightweight. I find the caliper brakes OK (I did put Salmon pads in both). There's no getting away from the fact that the cable to the rear brake is long, though, particularly if you have the open cockpit.

Two points of anecdotal evidence:

1. Riders of fast machines (Burrows lowracers and the Wooden Fish streamliner, for example) in the BHPC often use only a front brake (and make sure it's a good one, like a Hope). Some consider an effective rear brake a liability.

2. The last time a rider on a lowracer applied a hydraulic rear brake in an "emergency stop" situation in a BHPC race, he ended up leaving quite a lot of skin on the tarmac.

I would look into the possibility of changing the fork for the aluminium disc-tab-equipped one before I would consider putting a disc brake on the back.
Profit or planet?

Jacomus

  • My favourite gender neutral pronoun is comrade
Re: Disc brakes - rear only - bad idea?
« Reply #7 on: February 17, 2009, 12:23:34 pm »
Disk brakes are not that much more powerful than a good rim brake, the difference is in the modulation.

I would say, getting a nice hydro disk on there and you will be able to make better use of it than any cable brake as the run of the hose doesn't have an effect on the force your lever squeeze delivers at the caliper.

"The most difficult thing is the decision to act, the rest is merely tenacity." Amelia Earhart

Tiger

Re: Disc brakes - rear only - bad idea?
« Reply #8 on: February 17, 2009, 01:09:05 pm »
As said - anyone out there got some useful experience on this?

Not exactly. My Fujin has only ever been used for racing and day rides, and I'm a lightweight. I find the caliper brakes OK (I did put Salmon pads in both). There's no getting away from the fact that the cable to the rear brake is long, though, particularly if you have the open cockpit.

Two points of anecdotal evidence:

1. Riders of fast machines (Burrows lowracers and the Wooden Fish streamliner, for example) in the BHPC often use only a front brake (and make sure it's a good one, like a Hope). Some consider an effective rear brake a liability.

2. The last time a rider on a lowracer applied a hydraulic rear brake in an "emergency stop" situation in a BHPC race, he ended up leaving quite a lot of skin on the tarmac.

I would look into the possibility of changing the fork for the aluminium disc-tab-equipped one before I would consider putting a disc brake on the back.

Thanks - I recall the 'front brakes only'  thing from BHPC races, and the bloodied arse at Reading.. My fujin is essentially an all season audax ride so very different conditions - pushing the bike a bit beyond ts original design I think. 
Salmon pads - the only ones I don't think I have tried yet. I am using MTB pads at the moment - gert big long-uns. Off to wiggel for Salmons then.   

Charlotte

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Re: Disc brakes - rear only - bad idea?
« Reply #9 on: February 17, 2009, 01:15:54 pm »
As said - anyone out there got some useful experience on this?

The rear (only) disc on our tandem is cable operated with a lengthy distance 'twixt lever and caliper.  It's got to deal with the weight of two riders, one of whom is a decidedly sturdy gel.

It is awesomely good.  So good that I rarely use the front, in fact.  If I ever build a dedicated, full-on heavy touring bike, I intend to use the same setup.
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Jacomus

  • My favourite gender neutral pronoun is comrade
Re: Disc brakes - rear only - bad idea?
« Reply #10 on: February 17, 2009, 02:36:10 pm »
As said - anyone out there got some useful experience on this?

The rear (only) disc on our tandem is cable operated with a lengthy distance 'twixt lever and caliper.  It's got to deal with the weight of two riders, one of whom is a decidedly sturdy gel.

It is awesomely good.  So good that I rarely use the front, in fact.  If I ever build a dedicated, full-on heavy touring bike, I intend to use the same setup.

Yebbut isn't it the case that the rear brake onna tandem is only so effective because of the weight distribution of the bike? Or am I mixing that up with something else???

Disks rule, rim-brakes drool :P ;D
"The most difficult thing is the decision to act, the rest is merely tenacity." Amelia Earhart

Re: Disc brakes - rear only - bad idea?
« Reply #11 on: February 17, 2009, 02:50:22 pm »
As said - anyone out there got some useful experience on this?

The rear (only) disc on our tandem is cable operated with a lengthy distance 'twixt lever and caliper.  It's got to deal with the weight of two riders, one of whom is a decidedly sturdy gel.

It is awesomely good.  So good that I rarely use the front, in fact.  If I ever build a dedicated, full-on heavy touring bike, I intend to use the same setup.

Yebbut isn't it the case that the rear brake onna tandem is only so effective because of the weight distribution of the bike?

Or because the length of outer is kept to a minimum - cos that's where all the friction and most of the sponginess is.

If you're stuck with a long enclosed run then upgrading the cables might be worth the cash - something like Sram Flak/Full Metal Jackets, if you can get them to fit caliper brakes.

Re: Disc brakes - rear only - bad idea?
« Reply #12 on: February 19, 2009, 02:30:05 am »
My Toxy has a rear hydraulic disk but only a botched mini-V setup on the front as there is only clearance for caliper blocks.  It's not normally a problem to stop safely,  but more than once I've locked the back wheel when doing unplanned emergency stops - one time was when I was blasting down a hill in the lanes outside Redditch to meet a 4x4 roughing it out; the road was muddy and I came off in fact but not underneath said vehicle.  You know which is the brake which "works" and it's hard to avoid using it instinctively.
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Tiger

Re: Disc brakes - rear only - bad idea?
« Reply #13 on: February 19, 2009, 12:08:13 pm »
My Toxy has a rear hydraulic disk but only a botched mini-V setup on the front as there is only clearance for caliper blocks.  It's not normally a problem to stop safely,  but more than once I've locked the back wheel when doing unplanned emergency stops - one time was when I was blasting down a hill in the lanes outside Redditch to meet a 4x4 roughing it out; the road was muddy and I came off in fact but not underneath said vehicle.  You know which is the brake which "works" and it's hard to avoid using it instinctively.

Thanks for that - it would be the issue on the fujin. It is hard to recover from a rear wheel lock and I suspect that a strong back brake is going to be a liability. So I will carry on with sloppy brakes.

Re: Disc brakes - rear only - bad idea?
« Reply #14 on: February 19, 2009, 02:33:42 pm »
You should be able to lock the rear wheel on the Fujin with the std brakes.  If you can do that, then a disc brake isn't going to add anything useful.
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Jacomus

  • My favourite gender neutral pronoun is comrade
Re: Disc brakes - rear only - bad idea?
« Reply #15 on: February 19, 2009, 02:40:43 pm »
You should be able to lock the rear wheel on the Fujin with the std brakes.  If you can do that, then a disc brake isn't going to add anything useful.

Apart from control - if you fitted a small rotor and organic pads, you could have a very controllable, moderately powered brake.

Though, there seems to be not tat much point to go to the effort of doing that apart from that the brake will work the same in the wet or the dry.

 :-\
"The most difficult thing is the decision to act, the rest is merely tenacity." Amelia Earhart

Re: Disc brakes - rear only - bad idea?
« Reply #16 on: February 19, 2009, 02:49:12 pm »
Being a little more serious, that sort of level of control is not useful on a road bike.  If it was, then every road bike would have disc brakes, but they don't.
Your Royal Charles are belong to us.

bikenerd

Re: Disc brakes - rear only - bad idea?
« Reply #17 on: February 19, 2009, 03:03:09 pm »
Really, chaps, the Magura HS33s are the way forward.  Much more modulation than a disc brake, much more powerful than a V-brake.  Those are the reasons the Trials kids use them!  No issues from cable friction in a long or tortuous cable run.  I would have thought they'd be ideal for recumbents, especially as you don't have drop bars.

Re: Disc brakes - rear only - bad idea?
« Reply #18 on: February 19, 2009, 03:24:48 pm »
Really, chaps, the Magura HS33s are the way forward.  Much more modulation than a disc brake, much more powerful than a V-brake.  Those are the reasons the Trials kids use them!  No issues from cable friction in a long or tortuous cable run.  I would have thought they'd be ideal for recumbents, especially as you don't have drop bars.

Being a little more serious, that sort of level of control is not useful on a road bike.  If it was, then every road bike would have disc brakesHS33s, but they don't.

Having used HS33s, they don't have more modulation than disc brakes, rather less so in fact.
Your Royal Charles are belong to us.

Jacomus

  • My favourite gender neutral pronoun is comrade
Re: Disc brakes - rear only - bad idea?
« Reply #19 on: February 19, 2009, 04:10:26 pm »
Being a little more serious, that sort of level of control is not useful on a road bike.  If it was, then every road bike would have disc brakes, but they don't.

They aren't currently allowed... so who knows?

Having greater control over what your brakes are doing, on the twitchiest form of bicycle isn't a bad thing IMO.
"The most difficult thing is the decision to act, the rest is merely tenacity." Amelia Earhart

Re: Disc brakes - rear only - bad idea?
« Reply #20 on: February 20, 2009, 11:37:21 am »
Really, chaps, the Magura HS33s are the way forward...

But they require canti braze-ons, don't they? (unlike the older Magura rim brakes, which could be mounted on a "horseshoe").

If there is a horseshoe mounting system available, putting one on the front of an Audaxing Fujin might work well - cable/hose runs and frame clearance issues are often problematic on recumbents when using components not specifically designed for them. I'd say a rear one would be less useful.
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bikenerd

Re: Disc brakes - rear only - bad idea?
« Reply #21 on: February 20, 2009, 11:45:43 am »
But they require canti braze-ons, don't they?

They do.  I'd got it into my head that the Fujin had canti brake mounts, for some reason.  :-[

Mr Larrington

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Re: Disc brakes - rear only - bad idea?
« Reply #22 on: February 20, 2009, 02:09:46 pm »
Sadly Magura haven't done the horseshoe mount for years, and current models require your canti posts to be spaced 75 mm apart. 

Do not ask me how I know this >:(

Assuming you've got the disc mounting tabs on the frame, there's no reason other than the unpleasing assymmetry of the brake levers to preclude fitting an hydraulic disc on the back, though I think I'd be more inclined to go for a fork / front brake upgrade first.  I did half the 2007 Cambrian 600 without a rear brake and 1100 km of PBP / return to Larrington Towers without a front one, and know which I prefer...
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