Laing: Thanks for this detailed and informing overview; I have read it through and will read it again slowly, but I think I get it: 90* to brake arm pivots + as flat as possible at straddle, as little toe-in as you can get by with to prevent squeal, and make sure that the pads meet the rim brake tracks squarely. I've already done the last 2, must go back and look at the first 2. The single rear rack strut to seatstay bridge may limit my options in the rear. My pads are old Kool Stop salmons, the short, blocky sort. I did make various shim tools for toe in, must seek those out again.
Thanks again! On Tue, Feb 28, 2023 at 3:52 PM lconley <lcon...@brph.com> wrote: > Geometry is all important with cantilevers. I will use Paul models for > reference. Note that at a certain level, V-brakes are just optimized > cantilevers, so much so that they have too much braking force that must be > reduced at the levers. If maximizing braking force is the be-all, end all > of braking, then why use levers that reduce the braking force? But there is > something to be said for V-brakes having less tension (and therefore > stretch) on the brake cable. > > 1. You want the straddle cable operating at, or as close as possible to a > 90 degree angle to a line drawn from the brake arm pivot axis (the post > brazed/welded to the frame) to the straddle cable connection to the arm. > This is much easier on a Paul Touring than a Paul Neo-Retro. Motolites are > basically taking the progression to it's conclusion (Neo-Retro -> Touring > -> Motolite). Note that when working with Neo-Retros, this generally means > rotating the arms as far towards the rim as possible, using the fewest, > narrowest spacers between the pad and arm as possible (and that is allowed > by your tires). This is where some "experts" get it all wrong, they seem to > think that the rotation of the arm changes the direct of travel of the pad > at the rim - i.e. the arm carrying the pad should be straight up, which is > untrue. The direction of travel of the pad at the rim is fixed by where the > relative location of the pivot is to the rim-pad interface - only a welder > can be used to adjust this. The pivot is below and outside the rim -> the > pad will ALWAYS be traveling in a downward arc relative to the rim. Note > that because V-brakes use the same pivots as cantilevers, the cheapest POS > cantilevers that you can find vs. Paul Motolites - on a given bike, the > pads are traveling in exactly the same arc, this is a function of the frame > and wheel, not the brakes nor the brake adjustment. > > 2. Ideally, you want the straddle cable as close to straight as possible > where it goes through straddle cable carrier -> the straddle cable as short > as possible. This is a very unappreciated part of the equation. When you > apply a perpendicular pressure at the center of a straight cable, you would > actually get an infinite tension in the cable if it did not stretch. This a > very handy thing to use in many instances - you can move a car with only a > rope and this principal. The cosine of 90 degrees is 0. When you divide by > 0, you get infinity. If you want to prove this to yourself - make a > straddle cable between the ends of a V-brake and use a straddle cable > hanger connected to the brake cable cantilever/centerpull style. > > 3. There is an interaction between 1 and 2 - as you make the straddle > cable straighter (#2), you lose the 90 degree angle (#1). On top of that as > the cables, straddle hanger, and brake arms move, and the cables stretch; > the geometry changes. With Neo-Retros, getting the arm as close to the rim > as possible also raises the straddle cable arm interface up, getting the > arm-cable angle closer to 90 degrees. Note that means having your wheels > extremely true and minimizing the pad gap and toe-in. As the brake arm > rotates under application of the brake, this angle improves - gets closer > to 90 degrees again. As the straddle hanger rises under brake application, > this also gets the brake arm - straddle cable angle closer to 90 degrees > and increasing your braking force. But as all of this is going on, the > straddle cable at the straddle hanger is getting less straight, reducing > your braking force. With precise measurements of the actual relative > geometries on your bike, you can calculate all of this, or you can > experiment with lengthening and shortening the straddle cable. > > 4. I think that a far bigger item with braking is the pad interface with > the rim. Getting the pad centered on the rim, or actually just a little bit > above centerline of the braking surface is advised (remember that the pad > is traveling in a downward arc with the pivot below the rim with > cantilevers - with centerpulls, the pad is traveling in an upward arc). You > also want the pad flat to the rim (up-down flat when it contacts). If you > don't want squealing brakes, you must toe them in. The better your pads, > the more you must toe them in. The more you toe your pads in, the worse > your braking is because less of your pad is is touching the rim. I think > the long pads in fashion at the moment make this worse. I prefer shorter > pads with less toe-in. I have not experimented with cutting/filing/grinding > a bevel on the leading edge of the brake pads, yet, but I think that hold > promise. > > I spend a lot more time adjusting brake pads than anything else in the > braking system (that goes for discs also). The location of the brakes makes > it hard to observe the pad-rim interface which is where everything > important happens. > > I use bent pieces of old credit and business cards of different > thicknesses at the leading edge of the pads to set toe-in (this does not > apply to the Rene Herse centerpulls). A velcro strap at the brake lever on > non-Paul brakes to apply tension. My almost half-century old 3rd hand brake > tool is too narrow for todays brakes - still works on the Campagnolo side > pulls though. > > Laing > > On Tuesday, February 28, 2023 at 4:04:46 PM UTC-5 Patrick Moore wrote: > >> 1. Cantilevers too work better with tires no more than about 60 +/- mm >> wide; getting a 3" knobby between the canti bosses (unused; the Monocog >> 29er has disc brakes and is set up for both) is a hassle, even when they >> are soft at 13-15 psi. >> >> 2. While I can get decent (my definition may not be yours) braking from >> good cantilevers, at least I personally have found it much harder to get >> "powerful" -- = strong retardation with moderate hand pressure -- braking >> with cantis than with V brakes. I do like other things -- adjustability, >> modulation, looks -- better about cantis than Vs. >> >> I recall the miserable power from Mafac cantis, both single-bike >> shorter-arm version and longer-arm tandem version, on my Herse, pulled by >> Mafac levers. I daresay I could have shortened the straddle cables, but >> sold the bike before I got around to doing so (sold, not because of the >> brakes). >> >> Laing: How do you get strong cantilever braking, particularly with drop >> bar levers? I guess that one preliminary factor is to match the pull of >> your lever to the needs of the cantilever; my Dura Ace 7410-era drop levers >> probably don't have as much MA as my Paul Neo Retros and Touring cantis >> need for best operation, but I love the shape of those levers. >> >> I'd be interested in others' *apercus *about this. >> >> >> >> On Tuesday, 28 February 2023 at 05:29:32 UTC-8 lconley wrote: >> > Big tires, big fenders with clearance to the tires and V-brakes tend >> not to play well together. I have V-brakes on several of my bikes and I >> don't really >> > see any real advantage to them over cantilevers, unless you consider >> ugly an advantage. The cantilevers work just as well and have all the fender >> > clearance that you could want. I am waiting for Rene Herse to get their >> cable hangers back in stock to get one for the Bombadil. >> >> Laing >> >> > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to rbw-owners-bunch+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/rbw-owners-bunch/be53cfff-12c4-47bc-9f24-05a63dee80bfn%40googlegroups.com > <https://groups.google.com/d/msgid/rbw-owners-bunch/be53cfff-12c4-47bc-9f24-05a63dee80bfn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- ----------------------------------------------------------------------- Patrick Moore Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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