Mechanical Disc Brakes

For discussions about bikes and equipment.
PH
Posts: 13099
Joined: 21 Jan 2007, 12:31am
Location: Derby
Contact:

Re: Mechanical Disc Brakes

Post by PH »

I've never used mechanical discs with the wrong cable pull, I've never had modern drop bar STI's, I've read differing opinions about how much difference it makes, that's maybe because the riders happy with new Shimano have stronger hands.
I've been through a few with the intended levers - Clarkes, BB5, BB7 (Road and MTB), TRP Spyke, Paul Components Klamper, Shimano hydraulics (Deore and Alivio) - As long as they're well set up and adjusted, the stopping ability is dependent on the pads, I can't stop any quicker on the dearest as I can of the cheapest. The differences are in the feel, adjusting and servicing, the hydraulics win, hands down, for flat bars they even win on cost, that isn't the case for drop bars, though prices are falling. Of the mechanicals, the Klampers are well ahead, they're basically a better made BB7, easier to adjust, really simple to strip and service, and the mechanism is bigger and smoother so just feels nicer. The TRP Spyke (Or Spyre for drops) also feel nice and are fairly simple to use, but they easily corrode, then the adjustment doesn't hold and having stripped one it isn't something I'd want to repeat. The Clarkes and BB5's were not kept long, both seemed fine for the price.
That just leaves the BB7's, IMO bang for buck the best of the bunch, as long as the cable pull works for you. If you want to splash out go for hydraulics, if you want to splash out and stay mechanical, the Klamper/s (I just have one on the front of my folder)

Compressionless cable - Paul Components tested a range of available cable and recommend using bog standard coiled outer. That may not hold true of lesser brakes...
User avatar
CJ
Posts: 3405
Joined: 15 Jan 2007, 9:55pm

Re: Mechanical Disc Brakes

Post by CJ »

I'm very impressed with the TRP Hy-Road that I fitted to my 'new' carbon gravel/road bike a few years ago, because I wanted to use the Ultegra 10-speed STI upgrade off the old audax bike. They feel just as good as the full-hydraulic XT to 105 flat-mount system on my wife's flat-bar tourer, seeming to have all the advantages of hydraulic without any of the bother, since the fluid is a totally closed system in the caliper itself. I've taken the lid off one to see if any more oil needed adding, but decided it didn't.

Recently I've replaced the ordinary spiral-wound brake outer casings with Jagwire KEB SL compressionless brake casing; and that's what brought the performance up to just as good as full hydraulic. But they were already so very nearly as good that it's taken me three years to get around to making this upgrade. I originally used the ordinary stuff because I have a whole reel of it and was impatient to build up the bike - not having read the instructions until I unpacked the brakes!

What prompted me was the gear casings. The indexing has never been absolutely perfect on this bike, just good enough to live with, despite careful fitting and re-fitting of the casings. A bit of old Jagwire slick liner under the bottom-bracket helped, but only a bit. So I concluded that - in addtion to the under-bracket guide being of a not-slippery-enough plastic - the internally routed cable was probably dragging on random projections of fibrous resin inside the frame, most certainly in the snakey chainstay! So I bought some Jagwire Slick-Lube Liner Inner Cable Cover plus Jagwire LEX SL Shift Cable Housing, reasoning that the original casings were also now three years old and probably contaminated with impossible-to-remove wear debris. So whilst i was at it, with the handlebars half un-taped anyway for the brake casings, I did a proper job of it. (As these casings are half a mm fatter than Shimano it was quite a job too, scraping a mere skim of plastic off some of the casing ends so they'd fit my in-line adjusters!) The result, with new casing on the exposed cables and Slick Liner inside the frame, is perfect shifting both front and rear.

The brake and gear cables, by the way, are all still original. Why people just replace cables I do not know, I guess because it's cheap and easy. But cables are also easy to clean, casings not so much! So new casings are more likely to improve things.
Chris Juden
One lady owner, never raced or jumped.
maximus meridius
Posts: 791
Joined: 14 Feb 2023, 10:55pm

Re: Mechanical Disc Brakes

Post by maximus meridius »

I have BB7 on a road bike (drop bars) and am perfectly happy with then. Now.

Yes, they work with 160mm rotors. In fact mine were supplied with them.

Extensive research, mainly here, suggested that they were the "best". If "best" is a combination of braking effectiveness, durability and price.

But, as others have said, they aren't as good as they can be with current (post 2008) STI levers. Which is fine, as I use Ultegra triple nine speed.

Initially I built the bike with current Sora STIs. I didn't think the brakes were terrible, at all. Certainly no worse than the cantilever brakes on one of my other bikes. But not quite what I was hoping for, this being my first bike with disc brakes.

Then I found out about the NSSLR change of cable pull thing. Bought a dirt cheap really rough pair of Ultegra ST-6510 levers (pre NSSLR). There was an immediate and clear improvement. So since then I have been laying in stock lots of spare levers. I've bought most of the NOS ST-6510s that have become available world wide in the past couple of years. There's hardly any left. Because I've got them all. There's a pair in the states going for $750, if memory serves. It's a good area to invest in, as 9 speed triple Ultegra, 105, and Tiagra are all the same, so there's tons of used ones kicking about, if you wanted to go that way.

Braking with combination of BB7 and those Ultegra levers is absolutely fine, as far as I'm concerned. I can brake hard enough to lock the rear wheel, even on a dry tarmac road surface. I can probably lock up the front wheel, but it's not really something I want to experiment with. I haven't experience with as many different braking systems as some here, but I'm happy with them.

Other suggestions for cable discs are the TRPs, and the Paul Klampers. A previous poster may have made a slightly misleading statement about the Paul Klampers. They can be specified with THREE different actuation arms, for MTB pull, "Short" for current Shimano pull, and "C" for Campagnolo. I think, that the last would actually suit old pre NSSLR levers, though I'd have to buy them to find out. I rang Paul but we couldn't quite establish if that was the case. Given how much I've spent on spare levers, it would have actually been cheaper for me to buy the Klampers, and stick with my Sora levers.

PS, I've not bothered fitting compressionless cable. Though I bought some a couple of years ago. I might fit it in this years annual service.
TheBomber
Posts: 520
Joined: 16 Feb 2020, 8:18pm

Re: Mechanical Disc Brakes

Post by TheBomber »

Maximus - I believe it was your discussions with Brucey that educated me to the NSSLR problem that I highlighted near the top of this thread, but your user name has changed since then?
maximus meridius wrote: 30 May 2023, 3:06pm I've bought most of the NOS ST-6510s that have become available world wide in the past couple of years. There's hardly any left. Because I've got them all.
This made my LOL! I was going to suggest you sell a pair to the OP, then remembered that that won’t work with their 11sp groupset. Alternatives to Avid BBs it is then.
iandusud
Posts: 1577
Joined: 26 Mar 2018, 1:35pm

Re: Mechanical Disc Brakes

Post by iandusud »

Interestingly Paul Klampers recommend NOT fitting compressionless cable housing. Not sure why.
User avatar
CJ
Posts: 3405
Joined: 15 Jan 2007, 9:55pm

Re: Mechanical Disc Brakes

Post by CJ »

iandusud wrote: 30 May 2023, 6:08pm Interestingly Paul Klampers recommend NOT fitting compressionless cable housing. Not sure why.
It does have a potentially fatal vulverability, to which spiral wound is immune. Any deep damage to the outer sheath renders the 'compressionless' longitudinal wires liable to buckle and explode outwards without warning, under the compressive over-load of emergency braking. So suddenly there may no brake at all, just when you need it most! This happens to worn compressionless gear casings quite often, with no greater consequence than reversion to smallest sprocket or chainring. So it's best to be aware of this danger and watch for casing damage, as I am and do. But I'm not too worried, because I've investigated the construction and seen how the sheathing is not 'just plastic', but plastic reinforced with a woven net of fine fibres. I guess they're Kevlar or some such wunderstoff! Whatever, they presumably confer the greater insurance against casing explosion that's warranted in the case of brakes.
Chris Juden
One lady owner, never raced or jumped.
PH
Posts: 13099
Joined: 21 Jan 2007, 12:31am
Location: Derby
Contact:

Re: Mechanical Disc Brakes

Post by PH »

iandusud wrote: 30 May 2023, 6:08pm Interestingly Paul Klampers recommend NOT fitting compressionless cable housing. Not sure why.
You can hear it from the man himself near the start of this video (2.00), pretty much what I said upthread.

User avatar
andrew_s
Posts: 5795
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Mechanical Disc Brakes

Post by andrew_s »

ehelifecycle wrote: 27 May 2023, 9:10pm Currently, the BB7 SL is on a fairly good deal, paired with 140mm rotors can this caliper be used with 160mm, as that is what I have already on the bike?
The BB7 usually comes with a Post to IS adapter sized for a 140 mm rear disc or a 160 mm front disc (same adapter for either end of the bike).
You can use a different sized disc by buying a different adapter to that supplied (I generally use a 180 front disc with one of these).

The limit with larger discs is the problem of the disc itself fouling the fork blade or chainstay/seatstay.
Some makers advise maximum disc sizes as though it's something to do with frame/fork strength, but that's not so.

For a given rate of deceleration, the load on the frame is the same regardless of disc size, and the rate of deceleration is limited to the point at which the rear wheel leaves the ground.
The difference between how you stop as fast as possible with a "more powerful" 180 mm disc vs a 160 mm disc is that, with the 160 mm disc, you have to squeeze the brake lever harder to achieve maximum braking.
The same point applies to cable vs hydraulic or rim vs disc - you can't stop faster, but you don't need to squeeze the lever so hard. You've also more leeway to overcome braking problems, such as lubricant on the rim or disc.
slowster
Moderator
Posts: 4612
Joined: 7 Jul 2017, 10:37am

Re: Mechanical Disc Brakes

Post by slowster »

In the Paul Components video above he says about Bowden cable:
We just think it works the best. It goes around corners very nice.
Evidently the flexibility of the cable is an important factor in their recommending Bowden cable. Compressionless brake cable is a lot stiffer and less flexible than Bowden cable and hydraulic hose. That is generally not a problem with externally routed cables, but a lot of new frames now have internal routing, which will put multiple small radius bends on a cable. The resulting increased friction losses might be more significant than losses due to compression of a Bowden cable. In that situation the best cable might be a high quality Bowden cable and low friction liner/inner cable.
Bmblbzzz
Posts: 6249
Joined: 18 May 2012, 7:56pm
Location: From here to there.

Re: Mechanical Disc Brakes

Post by Bmblbzzz »

The previous poster ^ wins the prize for most appropriate name to thread!
Post Reply