Remember that flat at the straddle and 90 deg at the arms fight each other - it is always a compromise.
Laing On Tuesday, February 28, 2023 at 8:41:13 PM UTC-5 Patrick Moore wrote: > 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 <lco...@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-bun...@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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