Disc v Rim brakes

General cycling advice ( NOT technical ! )
Brucey
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Re: Disc v Rim brakes

Postby Brucey » 27 Aug 2016, 8:07pm

Colin,
I can't see the STI model number that SPA currently use on their touring bike but it is listed as '9s sora', of which there are two types;

ST-3400 - which has 'old style' 1993-2008 cable pull as per the OP's machine or

ST3500 - which has 'new style' (New Super SLR) cable pull.

The latter sort are 'perfect' with mini-Vs but the former sort have a cable pull that is short for use with such brakes. I'm sure that stiffer arms on RX6 are of benefit but I do wonder if they alone are enough to make the difference. Which model levers do you use with RX6 brakes?

BTW the high bosses make the system MA higher, and can lead to spongy brake, low clearance, frequent adjustment etc. Lower bosses would be of more use for correcting the problems described...?

cheers
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andrewk
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Re: Disc v Rim brakes

Postby andrewk » 27 Aug 2016, 11:05pm

531colin wrote:Andrewk....are they perhaps like these?

Image

Thats a May 2012 photo.....we have learned a bit since then

These will be a straight bolt-on fix for your braking woes......

Image

Thats an October 2014 photo, the brakes are Tektro RX6, you need one of those for each wheel and a "noodle" with adjuster for each brake.
The brakes are £20 a wheel and the noodles with adjuster are £3 a wheel....if you would like to PM me your address, I wouldn't be at all surprised if I could talk Spa into sending you some proper brakes.

The problem with the mini-vees which we used early on appears to be a problem of "lost motion" due at least in part to the flexibility of the arms; the RX6 brakes (amongst others) have much more rigid arms so that (counter-intuitively) you can get better clearance with the longer-armed brake.
Spa's brake bosses tend to be positioned quite high in order to get maximum tyre clearance, but even so 37mm tyres with the shorter-armed brakes may be pushing it a bit....is it possible that the mudguards are pushing the brake cable upwards, causing more lost motion?

As Brucey says, you can get very good braking with Shimano CX70 cantilever brakes, but they do need setting up rather than just bolting on, and best results are obtained with straddles other than the ones Shimano supplies. I'm not a fan of CX50 brakes, because its a struggle to get decent aftermarket pads to fit.


Colin,

Yes, they are like the black ones in the first photo. Thank you for your kind offer to talk with Spa, I will PM you my address etc.

Mudguard clearance is very tight especially at the front but there is still free space (albeit minimal) between the mudguard and the noodle holder when operating the brakes. However mudguard to tyre clearance is also tight and frankly inadequate.
I originally asked for 35mm tyres, however the Marathons supplied are oversize at 37mm (and seem very large when compared to 35mm Vittoria Randonneurs) and too large for available clearances.

So new tyres are called for, preferably 35mm but certainly no smaller than 32mm. Would you consider 35mm Vittoria Randonneur Pros (which are considerably smaller than the nominally same sized Marathons) to be OK or would you consider that I really ought to drop a further size to 32mm ones?

Andrew

MikeF
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Re: Disc v Rim brakes

Postby MikeF » 28 Aug 2016, 9:17am

andrewk wrote:So new tyres are called for, preferably 35mm but certainly no smaller than 32mm. Would you consider 35mm Vittoria Randonneur Pros (which are considerably smaller than the nominally same sized Marathons) to be OK or would you consider that I really ought to drop a further size to 32mm ones?

Andrew
Vittoria Hypers 32mm £13 http://www.planetx.co.uk/i/q/TYVIVOHY/vittoria-voyager-hyper-folding-tyre. The 35s are 37-622 and considerably bigger, but at £13 you could "experiment" with one. These are the probably the fastest and most comfortable tyres around in this range of size. (thanks to Reohn for alerting us to these :) )
"It takes a genius to spot the obvious" - my old physics master

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tykeboy2003
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Re: Disc v Rim brakes

Postby tykeboy2003 » 28 Aug 2016, 10:15am

Having ridden bikes for donkey's years (I'm 60), lately on 2 bikes with cable disk brakes and I'd sum up my experience as follows

1. Can't see any difference in ride quality
2. Braking is better than most rim brakes - it depends a lot on which pads/blocks you use.
3. Disks are obviously better in the wet.
4. The Avid BB5s on my tourer are fiddly to setup until you know the secret.
5. The Shimano brakes on my Giant Hybrid are better than the Avids.
6. A decent rim brake isn't that far behind disks (dual pivot caliper and V-brakes are the best I've used).
7. Wheel dishing seems to make little if any difference, after all the rear wheel on a bike with derailleur gears is already substantially dished (90+% of bikes), the disk just evens it up on the rear wheel.
8. No experience of hydraulic disks so I can't comment except to say that all cars and motor bikes use them so I suppose they must be better.

reohn2
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Re: Disc v Rim brakes

Postby reohn2 » 28 Aug 2016, 11:09am

tykeboy2003 wrote:Having ridden bikes for donkey's years (I'm 60), lately on 2 bikes with cable disk brakes and I'd sum up my experience as follows

1. Can't see any difference in ride quality
2. Braking is better than most rim brakes - it depends a lot on which pads/blocks you use.
3. Disks are obviously better in the wet.
4. The Avid BB5s on my tourer are fiddly to setup until you know the secret.
5. The Shimano brakes on my Giant Hybrid are better than the Avids.
6. A decent rim brake isn't that far behind disks (dual pivot caliper and V-brakes are the best I've used).
7. Wheel dishing seems to make little if any difference, after all the rear wheel on a bike with derailleur gears is already substantially dished (90+% of bikes), the disk just evens it up on the rear wheel.
8. No experience of hydraulic disks so I can't comment except to say that all cars and motor bikes use them so I suppose they must be better.


A couple of points:-
I agree about a decent rim brake being as good as discs,but not in wet and mucky conditions where the disc brake wins hands down.
Wheel dishing on rear Shimano hubs is no different for disc and non disc hubs,the non drive side flange is in the same place for both types.
The front is a different story,with the disc hub having a 14mm dish on the disc rotor side,IME this is to no detriment to wheel strength in practical terms as we've been riding a tandem with discs front and rear for 7+years without issue,so with the correspondingly less stress of solo use it's no problem at all,also worth considering is the amount of stress MTB riders put on disc wheels and we don't hear of their wheels collapsing under them.

The only minus to disc brakes AFAICT is a harsher fork to compensate for the forces imposed by a disc brake,that is subject to personal preferences and IME a big supple tyre such as Vittoria Hypers can nullify any short comings.
For my money an all weather machine ridden on crap UK roads(which seemingly worsen by the week with no signs of change anytime soon),all the other pluses of discs outweigh any negatives compared to rim brakes.
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531colin
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Re: Disc v Rim brakes

Postby 531colin » 28 Aug 2016, 11:43am

I have done a bit of digging, and the tyres in my photos are Marathon HS368, rather confusingly both 700x35 and 700x37 are marked on my HS 368 tyres. http://forum.cyclinguk.org/viewtopic.php?f=5&t=63112&start=60.....clearance looks OK to me?
By the time CJ reviewed the bike (June/July 2011 CTC magazine http://www.spacycles.co.uk/info/TiTourerreview.pdf) mini-vees were the "usual" brake set-up......when we changed the test bikes in the shop from CR720 cantilevers to mini-vees we pretty much stopped selling bikes with cantilevers, however cantis are still an option in 2016, and cantis were what CJ wanted, so cantis he got.
I guess we must have sold a lot of bikes with the old black mini-vees, and if they are all coming winging their way back to the shop with poor brakes, then I'm not hearing about it. Andrew's brake problem still sounds to me like lost motion somewhere, the brake arms need to return fully to get proper rim clearance; draggy cables and sticky brake pivots can prevent this.
It will be Tuesday before the shop opens, and I'll see where we go from there.
(In my digging around, I noticed that in 2012 we were looking forward to STIs that were compatible with Vee brakes.....some chance! http://forum.cyclinguk.org/viewtopic.php?f=5&t=62204&hilit=mini+vee&start=15

reohn2
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Re: Disc v Rim brakes

Postby reohn2 » 28 Aug 2016, 12:06pm

531colin wrote:(In my digging around, I noticed that in 2012 we were looking forward to STIs that were compatible with Vee brakes.....some chance! http://forum.cyclinguk.org/viewtopic.php?f=5&t=62204&hilit=mini+vee&start=15


FWIW,IMO it ain't going to happen because Shimano is a high volume manufacturer,with an ever narrower remit where integration is concerned,and STI's/V's(as a opposed to discs)being a particular(peculiar?)UK touring demand they ain't going to support it because the market is too small.
The answer to the problem is either a different gear changing system ie;Kelly's(:wink:),DT levers or b/ends,all three of which are niche,or a brake system that works well with STI's and big tyres.
Has Spa ever experimented with Travel Agents/full sized V's/STI's ?
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Brucey
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Re: Disc v Rim brakes

Postby Brucey » 28 Aug 2016, 5:44pm

I remember that too. I think something was lost in translation but we did get STIs that are compatible with mini-V's. All the 'new super SLR' compatible STis and levers will work OK with mini-Vs.

cheers
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531colin
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Re: Disc v Rim brakes

Postby 531colin » 28 Aug 2016, 6:58pm

reohn2 wrote:
531colin wrote:(In my digging around, I noticed that in 2012 we were looking forward to STIs that were compatible with Vee brakes.....some chance! http://forum.cyclinguk.org/viewtopic.php?f=5&t=62204&hilit=mini+vee&start=15


FWIW,IMO it ain't going to happen because Shimano is a high volume manufacturer,with an ever narrower remit where integration is concerned,and STI's/V's(as a opposed to discs)being a particular(peculiar?)UK touring demand they ain't going to support it because the market is too small.
The answer to the problem is either a different gear changing system ie;Kelly's(:wink:),DT levers or b/ends,all three of which are niche,or a brake system that works well with STI's and big tyres.
Has Spa ever experimented with Travel Agents/full sized V's/STI's ?


As the flat-earthers keep pointing out, its drops and touring that is a UK/America/Australia "peculiarity"......actually, put like that it sounds like a big enough market to interest Shimano?
What I'm NOT going to do is ditch my drops just because Shimano doesn't support STIs and Vee brakes.

As to Spa using Travel Agents, there are 2 things against them....cost....and keeping them working.......
Remember, I'm not talking about how you or I regard value for money on our bikes, or how we maintain them. I carry a spare gear cable these days, because people I ride with are fixated on STIs and seem to think the cables should last forever. (STI gear cables are the only cable failures I have seen in years.)
Likewise, I can get excellent results with CX70 cantilevers....but I ditch the fixed length straddle they come with and use an adjustable straddle, and then theres three(?) different spacers to contend with for different arm angles/rim widths.......

PH
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Re: Disc v Rim brakes

Postby PH » 28 Aug 2016, 7:29pm

531colin wrote:As the flat-earthers keep pointing out, its drops and touring that is a UK/America/Australia "peculiarity"......actually, put like that it sounds like a big enough market to interest Shimano?

Flat-earthers? You mean like CJ?
Flat bars are the future of touring, of that I'm certain. They're already the norm in all countries where cycling is mainstream, rather than something weird where you have to pretend to look like a racer to have any respectability. The fact that very few people use drops for touring, not that very few people tour, is the reason Shimano will never make road STIs for touring gears and brakes. In the countries where touring is big business they call it trekking of course.

Please, keep your insults to yourself, there's no reason we can't disagree without name calling.

reohn2
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Re: Disc v Rim brakes

Postby reohn2 » 28 Aug 2016, 9:33pm

531colin wrote:As the flat-earthers keep pointing out, its drops and touring that is a UK/America/Australia "peculiarity"......actually, put like that it sounds like a big enough market to interest Shimano?

In that case why haven't they done it?

What I'm NOT going to do is ditch my drops just because Shimano doesn't support STIs and Vee brakes.

I don't think anyone wants you to.
We've both got the same take how to cure that problem,Kelly's with DT levers,the correct Tektro levers for the preferred brake.
Other people have a different take on it.

As to Spa using Travel Agents, there are 2 things against them....cost....and keeping them working.......
Remember, I'm not talking about how you or I regard value for money on our bikes, or how we maintain them.

I found that once set up TA's didn't need anymore maintenance than a squirt of TF2 or GT85 now and again.
They cost £20 per brake retail,which is a bit steep but once fitted provide the magic link between STI and V's without the need for pads to be close as,to get any kind useable lever travel with mini V's,full sized are out of the question without TA's.
I carry a spare gear cable these days, because people I ride with are fixated on STIs and seem to think the cables should last forever. (STI gear cables are the only cable failures I have seen in years.)

I'm of the opinion people should carry their own spares,it's all part of the learning process if they refuse to.

Likewise, I can get excellent results with CX70 cantilevers....but I ditch the fixed length straddle they come with and use an adjustable straddle, and then theres three(?) different spacers to contend with for different arm angles/rim widths.......

But that's pretty specialised fettling which needs more attention than full sized V's/TA's and STI's.
If that's your preference I've no complaints,but I'm convinced if people want STI's they'll mostly want no fiddle minimum maintenance brakes attached to them.IME road STI's,TA's and V's fill that need well,they did on our Santana tandem for the ten years we owned it,and with a minimum of fuss with good stopping power :) .
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531colin
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Re: Disc v Rim brakes

Postby 531colin » 29 Aug 2016, 7:18am

PH wrote:............
Flat-earthers? ..............
Please, keep your insults to yourself, there's no reason we can't disagree without name calling.


I'm sorry, you are absolutely right. The shape of one's handlebars is a subject of extreme gravitas, and I apologise unreservedly for attempting to inject a bit of light-heartedness into the discussion.

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531colin
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Re: Disc v Rim brakes

Postby 531colin » 29 Aug 2016, 7:22am

R2, I seem to remember you saying you replaced your cables periodically as part of routine maintenance, my point is that most people won't even do routine maintenance

reohn2
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Re: Disc v Rim brakes

Postby reohn2 » 29 Aug 2016, 9:54am

531colin wrote:R2, I seem to remember you saying you replaced your cables periodically as part of routine maintenance, my point is that most people won't even do routine maintenance


If people don't they'll be in trouble ranging from minor delays to full on safety critical failures,that's a given for anyone using a bike,or any other piece of machinery irrespective of type.
If,like cars these days,people choose not to or can't do their own bike servicing they can always take it to their LBS,but to neglecting servicing is folly as I'm sure you'll agree.
Anyone failing to check their brakes daily,a hard squeeze of the levers should be enough,and an inspection weekly for frayed cables worn pads,etc,especially in mucky weather,is a fool by any definition,there are a lot of fools about but that's not the fault of the bike dealer or design of bike kit.
BTW if you've ever bought a USA made bike they have more warnings of such things than enough in the handbook and small print stickers on the frame,from 'always wear a h*lm*t to check tyre pressures and brakes daily',there's no accounting for idiots,more so those daft enough to think bikes look after themselves.

When I first bought the Santana I checked up on TA's as I'd never used them before,there were stories about them at the time of them over stressing cables due to the tight bends around the pulley,so I kept my eye on them expecting trouble and replaced cables bi-annunally as a precautionary measure,I never found one frayed or a broken strand in all the ten years we had the bike,and brakes performed very well,especially with BBB Tristop pads.
As you know tandems put a lot more stress on a bike than solos especially brakes and it's that experience that gives me no hesitation in recommending them.
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Dave W
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Re: Disc v Rim brakes

Postby Dave W » 29 Aug 2016, 7:51pm

I had a problem yesterday on my mtb with Avid Elixr3's.

Went to use it after months of inactivity. I couldn't turn the back wheel, I've had this before with a stiff chain or siezed freehub. This time though, it seems the hot weather had caused the brake fluid to expand abd lock the pistons on. I had to release some fluid from the bleed screws on both brakes to release them. Went for a thirty mile ride with no major problems other than the rear feeling a tad spongy. I'm going to order a bleed kit and change the fluid this week I think.