Cycling UK Forum

BigFoz wrote:If discs are the panacea for wet weather braking on a bicycle, why did I used to have to spend as much time drying out the discs on my motorbike as I do the rim brakes on my bicycle or suffer the dreaded wet weather brake syndrome?

I remain unconvinced

Have you used disc brakes on a bicycle?

I have three bikes with cable disc brakes(two solos with 160mm rotors and one tandem with 203mm rotors all BB7 road).All three work exactly the same if not better in wet weather and far,far better than rim brakes whether they be caliper,V's or Cantis all of which I either have on other bikes or have used in the past.

Brucey wrote:.........However bicycle brakes still are not there in every case, not when they are really wet. Some bicycle disc brakes need drying out about once every 30 seconds if you want to be able to stop in a hurry first time; such brakes are just not suitable for commuting IMHO....

I've tried this on numerous occasions in soaking wet conditions and even squirted a water bottle on the front disc caliper and rotor the stopping power and modulation doesn't alter,in fact the wetter and muckier the weather the better discs stop,or at least BB7 cable discs do,IMHO.

I have been using the hydraulic disc brakes as I have been commuting on the mtb. I don't know if they are different but I love the fact I dont have to think about stopping, lots of feel and can stop if need be on a sixpence.

reohn2 wrote:

Brucey wrote:.........However bicycle brakes still are not there in every case, not when they are really wet. Some bicycle disc brakes need drying out about once every 30 seconds if you want to be able to stop in a hurry first time; such brakes are just not suitable for commuting IMHO....

I've tried this on numerous occasions in soaking wet conditions and even squirted a water bottle on the front disc caliper and rotor the stopping power and modulation doesn't alter,in fact the wetter and muckier the weather the better discs stop,or at least BB7 cable discs do,IMHO.

It is a shame they are not all like that. IIRC the BB7s are usually shipped with sintered pads. This makes for a good cable-operated brake IME.

However some discs are made of softer material (and say 'use organic pads only' on them) so you can't use sintered pads on those.

I like hydro discs for their improved modulation (which is very confidence inspiring when it is a bit slape, as it often is, offroad). Sintered pads offer good power (including in the wet) and long life here too BUT they transfer heat into the brake fluid too readily, so hard use on long descents with sintered pads in hydro systems is not a good combination. If the system is open, the brakes can go away, and if it is closed, they can come on by themselves; not good either way.

If you are stuck with organic pads or similar (for whatever reason) then you may also be stuck with the possibility of a wet brake first application delay too. This is no real bother when riding offroad because you usually know ahead of time when you need the brakes to be 100% and can drag them a little before you need them to be full on; it doesn't take much to overwhelm the tyre grip, either. But on-road, commuting, it can be a killer. For commuting now with hydro discs, I'd probably stick sintered pads in and accept that the brake might go away on a long descent; you just can't have a brake that does nothing when you first use it, and some discs are worse than even mediocre rim brakes on first application when they are wet through.

BB7s with sintered pads make a lot of sense for road use if they avoid this. Asides from the obvious (i.e. that they weigh and cost something rather than nothing) the only moans I hear about these brakes are that the brake is sometimes a bit noisy, and that the fixed pad adjuster can bind up if it sees enough road salt.

cheers

Brucey
I've tried sintered and organic pads and find them both good in the BB7's.
I do ride off road quite a bit on my solos(probably around 30% of my riding)some of which can get quite mucky,not MTB mudplugging,though I do ride some singletrack.
I've never yet had a problem stopping whatever the conditions and never experience brake lag like I'd get with rim brakes in the wet.

What sold me on discs was the Cannondale road tandem,with 203mm rotors the stopping power is truly awesome,whatever the weather,and we've used it on some longish UK descents without problem.
I've no need or want for hydros for my type riding,BB7 road calipers have everything I want in a bicycle brake for the kind of riding I do.

Hi - can anyone confirm the stack and reach for the frame in a 51cm please? I calculate the stack to 555mm and the reach to 406mm from bb center. Reason I ask is because from here I can measure and then compare dimensions with an existing frame set up I have which works for me.

Thanks Gordon

re discs; I honestly thought one set of disc brakes I had was the dog's danglers (even when wet) until I rode in torrential rain; then the scales fell from my eyes, big time. They went from brillant to rubbish with just a bit more water added; wet to soaking more or less.

I have often wondered if part of the trouble isn't just the water, but the other stuff that comes off the road surface when it is wet and there is heavy spray; it doesn't take much oil or diesel to make anything wet super-slippy.

If there are 'known good' combinations of pad, caliper and rotor I think it would be worth recording these for the benefit of others.

However a note of caution is that there are very many flavours of parts and even more combinations/use conditions; in addition manufacturers have a nasty habit of making changes to specifications without any notification. When I've tried to compile similar info for motorcycle and car brakes it has been a total nightmare and any good info ( a very rare commodity...) is soon out of date.

cheers

Re disc components:-
On three of the four disc spec wheel sets three are Avid G2CS the other have the now defunct ones on the Kona in the fork thread.
All calipers are BB7 road.
I've used Avid sintered pads,Fibrax Sintered and Organic,Superstar Organic.

I find they're much of a muchness with Organic probably having the edge on sintered for outright stopping wet or dry.
One set of sintered pads that came fitted to a new caliper when building my Vaya never seemed to run in,the stopping power didn't reach optimum,so I replaced with S/Star organic and things improved dramatically.
I don't know if those pads were contaminated in some way ,I've still got them and keep promising myself I'll fit them to the rear of the Kona(winter bike)and see if they'll improve,I know the story on contaminated pads but it may be worth a try

As I said before BB7's are the only disc brakes I've used and fulfil all my needs and wants for a dropbar disc brake, I really can't see how I can improve my stopping power/modulation.

One other thing is that Shimano STI's need the pads set closer to the rotor than the Tektro RL340's I use with Kelly Take Off's.The RL340's must pull more cable.

Brucey wrote:re discs; I honestly thought one set of disc brakes I had was the dog's danglers (even when wet) until I rode in torrential rain; then the scales fell from my eyes, big time. They went from brillant to rubbish with just a bit more water added; wet to soaking more or less.

I haven't ridden a pushbike with discs so in that sense can't comment.

However I do recall riding my first disc braked motorcycle, a single disked Triumph Bonneville (1970's?) in very wet conditions coming home from work one night. I can only describe the wet braking performance as non existent for several long seconds until the water was born away and pad met metal again. It was early days technology for motorbikes back then (but disc brakes had been used in cars for some time already with no wet fade problems).

I managed to steer between the cars I had been trying to slow down for (brakes just weren't working in the wet) and I still remember the feeling of nothing, nothing, nothing, then tyres biting then skidding as the brakes "came one" again with my right hand now wringing the front brake lever. Not pleasant.

Fast forward to now and I don't think its quite the problem it used to be - in the motorcycle world at least.

I share your caution though. I think part of the problem may be the variety of sources of parts (pads and discs) from manufacturers who may not have felt the need to test and warrant their brake parts under these conditions. Another part of the problem may be the assumption that " we know disc brakes from motorbikes and cars" and therefore assume its just doing to work fine on a smaller scale on cycles. Thats probably what they thought when transposing car disc technology to motorbikes in those early days. Maybe its the same sort of problem with bicycle discs?

Regards Gordon

It sounds to me like we may still be in the pioneering days of discs for cycles.

A single front disc on my 1975 Honda 400/4. No problems, stopped just fine.

2wheeler wrote:Hi - can anyone confirm the stack and reach for the frame in a 51cm please? I calculate the stack to 555mm and the reach to 406mm from bb center. Reason I ask is because from here I can measure and then compare dimensions with an existing frame set up I have which works for me.

Thanks Gordon

Can I just confirm that stack and reach are the vertical and horizontal distances (respectively) of the top of the head tube from the BB ?
If that is the case, then you can get much the same information as "stack" from the seat tube length and the top tube slope, and much the same information as "reach" from the top tube length and seat tube angle.
Its readily possible that the shops bike Cad will calculate reach and stack, so if you confirm they are what I think they are, I will bring this to the attention of the shop.
There are test bikes in all the sizes at the shop.

pete75 wrote:I've never had a sloping top tube bike - mainly on aesthetic grounds. Do they come smaller than a normal frame for teh same size - if you know what I mean...

I dont like sloping TT's either for the same reason. Not that that's anything to do with your question.

531colin wrote:Can I just confirm that stack and reach are the vertical and horizontal distances (respectively) of the top of the head tube from the BB ?

Yep - those are they, thanks, Gordon

Ok the computer is telling me the stack would be 555mm but the reach would be 383mm.

Measuring this in the real world is a tad tricky.

Ook.

The Computer Monkey wrote:Ok the computer is telling me the stack would be 555mm but the reach would be 383mm.

Measuring this in the real world is a tad tricky.

Ook.

Rightio thanks.. I'll look at my reach calculations again!

Hmm, we do trickiness! Couresty a plank o' wood, spirit level and plumb line! Are you the librarian??

Cheers Gordon.

Are you the librarian??

No, but I am aware of his work.