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"Flaoting" rear brake for single pivot

SplottboySplottboy Posts: 3,695
edited July 2010 in MTB buying advice
Hi, lI'm looking for info on a Floating Rear Brake for a single pivot frame.

I know theres a US company doing a long-rod type system the runs along the swingarm etc.
Can't recall who did it.
Any advice welcomed.

Also, is a floating brake gonna make a great deal of difference?
I've had 3-4 single pivot bikes before, and they "seem" ok, but maybe the floating bits will improve overall rear braking?!

Rear braking stiffening up the rear is my main concern, which I'd like to lessen/eliminate.

Thanks..
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Posts

  • ride_wheneverride_whenever Posts: 13,279
    If you're not noticing the brake jack then i wouldn't worry too much.

    IIRC the best aftermarket one required a v-boss to mount the other end onto.
  • nicklousenicklouse Posts: 81,520 Lives Here
    brake therapy.

    a total waste of money.

    all it does is make the brake move the same way as a 4 bar.

    they do not fit all frames as many are not wide enough and dont have suitable hubs.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • SplottboySplottboy Posts: 3,695
    Ok, thats the one. Brake Therapy.

    If I get the frame, I'll give it afew thrashes and re-assess if I need it. TA!
  • yoohoo999yoohoo999 Posts: 940
    Why do people always think that the issue with single pivots is brake jack?

    Is arguable that brake jack doesn't even exist at all.

    What does exist is brake squat, which isn't even necessarily bad (in the right doses).

    Single pivots often have more brake squat than other suspension systems, which people often mistake for brake jack.

    I used to get much more squat than I was used to on other bikes which I found irritating and I didn't like how the bike handled at times. I stuck a floating caliper on and now it handles/brakes how I like it.


    Ride your bike, if you don't like how it brakes, buy a floating caliper kit. Or brake less.
  • supersonicsupersonic Posts: 82,708 Lives Here
    Depends on the location of the instant centre.
  • yoohoo999yoohoo999 Posts: 940
    yeah, so if a bike has a linkage instant centre, then it will be less squat than a single pivot bike (which it's pretty safe to assume won't have anywhere near the same instant centre. I'm trying to think of single pivots that do, but none spring to mind at the moment).

    I'm certainly not saying that squat is an issue, it's just a characteristic that either bothers you or it doesn't. Some people won't even notice it at all.

    one thing that does concern me is whether i'm taking away some of the single pivot's advantages in respect of weight transfer by sticking on the floating caliper (since it mucks around with the brake squat). Not that I'm too bothered about it though, I've got the bike to handle exactly how I want it to now. I'm quite fussy, but I don't think I'm unreasonable or compulsive about it.
  • supersonicsupersonic Posts: 82,708 Lives Here
    If you have Linkage software, you can calculate braking squat.

    With a single pivot the IC is the main pivot of the frame. The braking force vector is a line from the rear tyre contact patch through the IC.

    WIth a four bar or flationg linkage bike, the upper and lower links can be used to find the IC: can actually make things worse, not better, if not implemented right.
  • nicklousenicklouse Posts: 81,520 Lives Here
    yoohoo999 wrote:
    yeah, so if a bike has a linkage instant centre, then it will be less squat than a single pivot bike (which it's pretty safe to assume won't have anywhere near the same instant centre. I'm trying to think of single pivots that do, but none spring to mind at the moment).
    Ohhhhh so unsafe ground.....
    I'm certainly not saying that squat is an issue, it's just a characteristic that either bothers you or it doesn't. Some people won't even notice it at all.

    one thing that does concern me is whether i'm taking away some of the single pivot's advantages in respect of weight transfer by sticking on the floating caliper (since it mucks around with the brake squat). Not that I'm too bothered about it though, I've got the bike to handle exactly how I want it to now. I'm quite fussy, but I don't think I'm unreasonable or compulsive about it.

    but how much braking is done at the rear? very little with the weight transfer to the front, front brake for braking and rear for steering.

    there used to be a great document on it on a site linked from the old linkage site but it has long since gone. I wonder if i still have it in paper form.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • SplottboySplottboy Posts: 3,695
    Ok, never mind the Tech Talk - I'm just jealous - how bout a "Real World" example:
    Coed y Brenin, "Snap, Crackle, Pop" section comes to mind.

    Used to be that as soon as you've got over the one drop-off, then it's a few secs before the next etc.
    If the single-pivot rear end isn't feeling "right" 2nd, 3rd drops get a bit hairy, esp if very wet.
    ( Might be the trails changed, but it USED to be like this.)

    I've raced it on a hardtail, Lt wt XC full sus and San Andreas. Various degree of feel, never not cleared it though.)
    Q; In a series of drops like this, is single pivot, Beneficial or a Liability?

    Ta.
  • supersonicsupersonic Posts: 82,708 Lives Here
    It needs the tech talk to explain the differences. But as nick says, many don't feel them anyway.

    The floating arm defines an IC that is not the main pivot. So it depends where the single pivot was, and where the IC for the floating arm now is.

    Apart from that, all I can say is try one and see if makes things better or worse for you.
  • AnonymousAnonymous Posts: 79,678
    Splottboy wrote:
    Also, is a floating brake gonna make a great deal of difference?
    Nope, nothing at all. Brake "jack" isn't an issue on the vast majority of frames anyway. on a high single-pivot (Orange 5, old Marins, SC Bullit etc etc etc) the brake will actually cause the rear to squat a little under braking, whereas on low single-pivot (like Konas) it can cause the suspension to extend.

    Nothing will ever stop this.
    The effect is caused because during it's travel, the rear wheel either moves closer to or further away from the bike. When the brakes are used, the rear wheel is "pulled" rearwards, causing it to drive the suspension slightly in whichever way will allow it to more rearwards.
  • supersonicsupersonic Posts: 82,708 Lives Here
    In that regard, it can make a difference - if it was extending before a new set up might make it compress, which the rider might prefer. But does bvery much depend on the geometry. Fabien Barel used to have his linkgae set up for a lot of braking squat.
  • AnonymousAnonymous Posts: 79,678
    supersonic wrote:
    In that regard, it can make a difference - if it was extending before a new set up might make it compress, which the rider might prefer. But does bvery much depend on the geometry. Fabien Barel used to have his linkgae set up for a lot of braking squat.
    Wel, Fabien Barel is French, and all french cars have horrendous braking squat at the rear, so... :lol:

    In all seriousness though, I refuse to believe it can make any difference, since the force is still trying to pull the rear wheel rearwards, and that force will always be applied to the suspension at the rear axle.
  • supersonicsupersonic Posts: 82,708 Lives Here
    But the force is directed a different way.
  • AnonymousAnonymous Posts: 79,678
    Splottboy wrote:
    Ok, never mind the Tech Talk - I'm just jealous - how bout a "Real World" example:
    Coed y Brenin, "Snap, Crackle, Pop" section comes to mind.

    Used to be that as soon as you've got over the one drop-off, then it's a few secs before the next etc.
    If the single-pivot rear end isn't feeling "right" 2nd, 3rd drops get a bit hairy, esp if very wet.
    ( Might be the trails changed, but it USED to be like this.)

    I've raced it on a hardtail, Lt wt XC full sus and San Andreas. Various degree of feel, never not cleared it though.)
    Q; In a series of drops like this, is single pivot, Beneficial or a Liability?

    Ta.
    Single pivot is neither a benefit or a liability in this instance, it's just another way of attatching the wheel to the bike.
    Where single pivots can sometimes suffer is on square edged hits, (like riding up a square stone, or a kerb) since the action of your weight through the pedals, and the pedal kickback induced from the suspension movement can cause the system to become temporarily unresponsive - if both forces balance out.

    This was definitely noticeable on my old single pivot marin, which is why they were eventually superseeded. It wsn;t a problem, just one of the characteristics. Your legs still give you most of your suspension anyway.
  • AnonymousAnonymous Posts: 79,678
    supersonic wrote:
    But the force is directed a different way.
    I'd love it if you could convince me, but as I see it, the rear axle is still trying to pull the rear wheel rearwards (Do I get the award for using the word REAR the most times in a sentence?).
    It makes no difference where the calliper is attatched.
    I cannot visualise any way in which those kinematics could be changed.
  • SplottboySplottboy Posts: 3,695
    So, my 26INS MONSTER THIGHS are my suspension???

    And I'm gonna pay someone £500 for a "suspension" frame?

    Do you think anyone would be willing to patent "Splott-spension ?" LOL!

    Cheers for the advice so far.
    Quite enlightening...
  • AnonymousAnonymous Posts: 79,678
    yeah, your legs are the main form of suspension, the frame really just takes the "edge" off things, and is usually the faster reacting of the two.
  • supersonicsupersonic Posts: 82,708 Lives Here
    supersonic wrote:
    But the force is directed a different way.
    I'd love it if you could convince me, but as I see it, the rear axle is still trying to pull the rear wheel rearwards (Do I get the award for using the word REAR the most times in a sentence?).
    It makes no difference where the calliper is attatched.
    I cannot visualise any way in which those kinematics could be changed.

    It is difficult to explain, and I probably didn't word that well - you have to look at the Instant Centre and forces generated when braking from the tyre contact patch. I shall try and think of an easy way to explain what I am getting at.
  • SplottboySplottboy Posts: 3,695
    If you do, remember, KISS, Keep it Simple Stupid, the studid being me!
  • AnonymousAnonymous Posts: 79,678
    but the suspension action from braking would occur no matter how the wheel is stopped, be it a disc brake, V-brakes, a shoe jammed in the chainstays, or a seized hub.
    It's just the wheel trying to pull the swingarm to it's most rearward position.
  • supersonicsupersonic Posts: 82,708 Lives Here
    The article says:

    'The braking force is applied to the tire's contact patch at the ground (where the majority of forces applied on the rear suspension are generated), opposite the direction of motion. This creates a force that acts on the pivot (or, on a linkage bike, on the instant center of the linkage). Depending on the placement of the pivot or linkage instant center, this will be either a compressive force or an extensive one.'

    If the brake caliper is placed on a further floating linkage, then the IC of that determines how the brake will react as the force will be directed towards that. You can place the caliper in any orientation you want on the floating link [as you said, the orientation makes no difference], the link still will have the same IC.
  • supersonicsupersonic Posts: 82,708 Lives Here
  • AnonymousAnonymous Posts: 79,678
    Still don't see it. I've read the links, and it doesn't seem to mention anywhere that brake jack or squat can be reduced by a floating calliper.
    The rear wheel is made to move as rearwards as it can under braking, that's pretty much all there is to it.
    Whether the suspension has to extend or squat in order for the wheel to travel rearwards from it's current position depends on the suspension design.
    A brake is a brake, it's position around the disc does not reduce the effect of drag on the rear wheel, if it did it would interfere with decelerating!
  • supersonicsupersonic Posts: 82,708 Lives Here
    I'll let nick try and explain.

    The second link says that the floating linkage will make the system behave like a four bar of the same linkage. And not how it was. Doesn't say whether would be 'better' or worse, but different.

    There is more to it because of the migration of the IC.
  • AnonymousAnonymous Posts: 79,678
    the IC does not change, the WHEEL path is the same.
  • supersonicsupersonic Posts: 82,708 Lives Here
    The IC of the floating linkage is not the same place as the centre of curvature.
  • supersonicsupersonic Posts: 82,708 Lives Here
    The article says the first bit here:
    Many claims are made for floating brakes (see the “False Claims for Floating Brakes.” section for an expose on some widely believed things that floating brakes do not do). However, the only thing that these mechanisms do is to give a bike the braking character of the brake mechanism's linkage system. For example, these mechanisms can give a mono-pivot the braking character of a 4-bar with suspension geometry identical to the brake mechanism's linkage geometry
  • nicklousenicklouse Posts: 81,520 Lives Here
    supersonic wrote:
    I believe this is the article nick was on about:

    http://raystrax.com/PathAnalysis/pa310.html

    nope this one

    http://raystrax.com/PathAnalysis/pa52.html#BISL
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
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