Monday, October 24, 2011

Kicking Back, Old School Style

Jacqueline, Crankset
When I wrote about the modern Sturmey Archer Duomatic hub last week, a reader pointed out that vintage coaster brake hubs have "more 'backlash' - so you have to rotate the pedals further before engaging the brake." I had noticed this as well after switching back and forth between bikes with modern coaster brake hubs (SA and Shimano) and vintage ones (SA and Sachs). 

My preference is for the older style. The position my legs tend to be in when braking with the older hubs feels more comfortable. And it is also more convenient to start from a stop: It is easier to arrange the pedals in the correct position when there is more "give" before the coaster brake is engaged.

I am sure there is a good reason why current coaster brake hubs are made so that they are quicker to engage. Anybody know what they are, and the history behind the change?

30 comments:

  1. Could it simply be wear and tear making them loser on vintage models you tried?

    When I tore apart my first Sturmey Archer to replace the two metal brake pads, they were so incredibly worn thin. It would take more rotation to get them to brake sufficiently. New pads, the rotation amount became slightly shorter.

    I've only owned one coaster brake from new (and quickly sold the bike) so I have no long term experience watching a hub from the beginning of it's life to the end of life. This is just a guess at the brake pad thickness. I could totally be wrong.

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  2. Hmm, I guess it's possible. Though I've tried one hub that was supposedly new-old-stock and it had the same generous travel distance as the used hubs I've tried.

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  3. I imagine it is so you can brake quicker. You can learn to brake with the pedals in almost any position.

    The old school method was to rotate backwards to get the pedals to around 45 degrees so you can easily modulate them This is great when you are coming up to a stop sign or something.

    But in an emergency braking situation this isn't going to fly. It would take too long. You want to be able to start braking immediately upon reverse peddaling.

    Of course, you really should use the front brake for fast stops, but in most "bike path" countries I've observed the bikes don't even have front brakes or people have stuff in their hands and can't use them.

    That's my theory at least.

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  4. Hi,

    I have both the 1960s and the 1970s models of the F&S Duomatics, both new-old-stock
    and they do have more backlash than the Sturmey model, even when new. The 1960s model has more backlash than the 1970s model, so
    there has been a progression of increasingly less backlash as time goes on.

    Here is my speculation on the reasoning behind this...

    The amount of backlash you feel at the pedals is affected by the gear ratio (size of the chainwheel and rear sprocket). Higher gears means you feel less backlash at the pedals.

    I think the older hubs were mainly used on small wheel bikes which have relatively high gears to make up for the small wheels.
    To provide enough backlash with the high gears, they built more backlash into the hub.
    Hope this make sense!

    Still I prefer the greater backlash on the older hubs, even when used on full-sized 700C wheels. I use a 38T chainring and 21T sprocket, so high gear is my normal cruise gear and I have the low gear for starting and climbing.

    John I

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  5. @Rona,

    You're right that the backlash increases as the brake pads wear, but in this case the old duomatics had more backlash built into them from new.

    I'm trying to figure out how I can increase the backlash on the new sturmey archer duomatic hub....

    John I

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  6. I recently built a bike around the "kick back". The jury is still out though as I find it curious that some light steady braking will cause the mechanism to (it seems) noisily cycle back and forth. The gears do shift but the "clacking" noise is worrisome. I even returned the first unit I purchased only to receive a replacement that behaved the same way. So, I suppose they all do this. Definitely not the same kind of braking feel as a regular coaster brake. V, have you had this same occurrence?

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  7. Things that contribute to more pedal backlash in no particular order.

    Larger cog on hub.

    Worn brake shoes.

    Finer thread pitch on driver. See: http://www.parktool.com/uploads/images/blog/repair_help/coaster30.jpg

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  8. My understanding is that other changes (no neutral in 3 speeds, lips on quick release forks) were made to avoid potential liability issues - if the brake engages faster, you'll (theoretically) stop faster if there is an emergency.

    The brake shoes on the coaster brakes I've seen have generally been fairly thick, and the engagement seemed to depend a lot more on the threading of the gear/clutch than on any wear on the brake shoes. I think it is design, not just wear.

    Angelo

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  9. All my low-miles Vintage SA, Bendix and New Departure coaster brakes require about the same degree of back-pedal travel to engage as the sloppy old used up ones of the same type in my hoard.

    I have a 2 speed, red stripe Bendix 2-speed that uses almost 80 degrees(46x18 cogs) before really digging in. I think it was made in '62 and was un-used in a box until I laced it up for a 26" Bamboo framed cruiser I'm building with vintage stuff. I haven't tried it on the bike yet(Maybe YEARS to go on that one).

    If you like coaster brakes, and I really do, than you find that moment of terror as your brain say's "IT SHOULD BE WORKING BY NOW WHAT THE..." endearing. It's not about stopping, it's about riding weird old stuff.

    Spindizzy

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  10. "The old school method was to rotate backwards to get the pedals to around 45 degrees so you can easily modulate them This is great when you are coming up to a stop sign or something. "

    Maybe that's why it especially feels better on the Vienna cycling paths.

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  11. How are your feet positioned when you engage the coaster brake?

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  12. Spindizzy - "Wow" on so many levels : )

    Velodog - I've experienced what you describe, and would consider that "broken" or at least not properly adjusted.

    Anon 3:03 - I brake by pushing back with the right one, and that way my right foot ends up being on top when I come to a stop. I just put the left one down, then push forward with the right when starting.

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  13. A Berlin bike mechanic told me that Sachs was forced to improve the braking power of their classic 3spd coaster hubs at some point in the 1990s due to government (or EU) regulations. You can recognize these hubs with stronger braking power by the small gear chain moving a bit whilst back braking - he demonstrated this effect to me on a new bike he had in the showroom.
    I am still using the older models exclusively, and am completely satisfied with the braking power (and the amount of crank turning needed to engage the brake), although I am not on the light side of body weight and like to go fast ...
    But it holds true that some older Torpedo coaster hubs (that's the original design to all those Bendixes et al that copied it later ...) do require pretty much crank turning to engage the coaster brake, and some do even take a large degree of crank turning to engage the driving mechanism, which is something that I dislike strongly. This of course is caused by wear on the respective parts, and finally (but only after decades of use and zillions of kilometres on the roads) wearing out the forged steel hub shell. Those old hubs still remain useable, but they're no fun to ride anymore.

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  14. Velodog said...
    >some light steady braking will cause
    >the mechanism to (it seems) noisily cycle
    >back and forth.

    My Sturmey S2C does the same thing, although it does diminish as the hub wears in.
    The older hubs never did this.

    John I

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  15. Anon 3:13 - Oh right, I have a Torpedo hub on my Gazelle at home. There is indeed a bit of travel for the drivetrain to engage when starting to pedal forward from a stop; never thought about it until now.

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  16. If only Sheldon Brown were still with us, I'm sure he would know. We could always try asking Jim Langley, or the former members of the Morrow Dirt Club...

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  17. the old Bendix coaster breaks always stopped the wheel in the same position, so if you lock it up it always skids the same patch on the tire. could a change in design to increase tire wear possibly have resulted in a decrease in backpedal travel.

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  18. I've never tried a Benedix hub, would love to find a bike with one. Trying to imagine the mechanism of stopping the wheel in the same position. Is this something the cyclist is able to feel?

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  19. No you don't feel it . But if you are a typical 10 or 12 year old boy , skidding was great fun back then, when the back tire blows out it is plain to see the effects of the wheel stopping in the same position time after time

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  20. "I am sure there is a good reason why current coaster brake hubs are made so that they are quicker to engage."

    It flatters me that you believe product development to be such a rational process!

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  21. Hey Don, I never thought about that but my memory of piles of back tires with holes burned in them bears that out. Is it a function of the hub body being slightly oval due to manufacturing tolerances and the shoes getting wedged in the same spot maybe? Interesting insight...

    One of the nicest Coasters in my opinion(if a little fragile) is the old New Departures from the 30s and 40s with the multi-plate clutch pack. Very smooth and progressive. I've been trying to decide whether to use a like new ND model "D" I got from a rusted out barn bike, a Bendix red-stripe 2 speed CB or a SA 3 speed CB on my bamboo bike. I might just have to build 3 rear wheels and see which one I like best. None of them will probably stop that well but it wont be a fast bike anyway...

    Spindizzy

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  22. I am used to old school coaster brakes and rode a single speed with coaster brakes this summer and was constantly skidding the brakes on, accidently. I would back pedal just a skosh and ENGAGE, the breaks would hook up and stop me when I was not expecting that and it threw my cadence and my pace off. I thought it was just me and that I haden't rode one in many years but from the sounds of it manufacturers have left no margin for error. The slightest backpedal results in STOP when I am only trying to get my feet into a comfortable coasting pattern with my feet at the three and nine o'clock position. Sigh.

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  23. Don--Tire wear in the same position is more of an issue if the skid patches are low in number. I think a coaster brake hub could use the same calculation is a fixie setup to avoid too few stopping surfaces. Once the number gets high enough, 16 or more patches, I doubt it's a problem.

    I had a coaster brake as a young cyclist, abused it thoroughly and did tricks/skids until it started pushing through backwards with an awful click. That was unpleasant the first time I felt that.

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  24. MDI, Wow. I've never heard of that. It sounds like you abused yours even worse than we did. I would love to take one that does that apart and see what it looked like...

    Spindizzy

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  25. Yeah it should be impossible. Don't know. I was too young to look at things like reaction arm still attached, etc.

    All I recall was you had to kick it backwards hard and then it would push through. It would usually happen on trick/skid stops.

    I think a broken reaction arm bolt would cause regular beating against the chainstay that I would notice. It slowed down the bike before the kick-through so I don't think the shoe was necessarily worn through. I just don't know.

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  26. "But if you are a typical 10 or 12 year old boy..."

    Ah. That would explain why I can't relate to all the things you're talking about here!

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  27. MDI, If it got so worn in the hub that the shoes on an old Bendix had room to over-ride the "dogs" on the driver cone that forces them out than I could believe it could happen just like you said. I'd expect to see a hub swollen or split between the flanges or one that looked like a grenade went off inside.
    Either would be sorta' inspirational to a fellow 12 year old in much the same way that Pete Townshends smashed guitars made me want to learn to smas, er, play guitars.. BRAVO!

    Spindizzy

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  28. MDI the coaster brake phenomenon I am referring to involves what appeared to be one skid patch, a pretty low number I think you will agree, well under 16.

    V come on surely you skid on a coaster brake bike the odd time just for fun, its not just boys is it? seriously I don't relate to such carry on much anymore either but I have a fabulous memory

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  29. I almost flew off the Pilen the first time I tried to adjust my coasting position, the coaster was surprisingly strong + instant. :)

    I think it varies hub-to-hub, too. They "feel" might also depend on how well the chain tension is adjusted, etc.

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  30. MDI - I think you push the coasterbrake harder than I do. I thought the Pilen's brake was good, but not unusually strong. On the other hand, I find V-brakes hard to deal with, and they do almost throw me off the bike if I'm not careful.

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