Straddle cable lengths

[We_are_Stevo]

Why would I make this sh*t up?

Gospel according to SB...

Types of Cantilevers
Conventional cantilevers fall into three types, defined by their cantilever angle:

Wide-profile cantilevers have a cantilever angle much greater than 90 degrees. The best example of this type is the old Mafac cantilevers, in which the anchor arm actually sloped downward from the boss in some installations. This design is now pretty much obsolete. Wide-profile cantilevers have rather low mechanical advantage, and work well only with levers with a high mechanical advantage.

Medium-profile cantilevers have a cantilever angle of around 90 degrees. Most late-1980's cantilevers belong to this family. Medium-profile cantilevers are very forgiving and give excellent all-around performance with a wide range of set-ups.

Low-profile cantilevers have a cantilever angle of less than 90 degrees. The principal advantage of narrow profile cantilevers is that they don't stick out so far from the frame or fork, very desirable, because protruding cantilever arms can cause a multitude of problems, particularly in the rear, where a rider's feet may hit them. Narrow-profile cantilevers are also capable of excellent performance, but only if properly set up. A carelessly set-up low-profile cantilever may have very low braking power, even though it feels great on the workstand.

..BiTD I had a set of plastic Shimano workshop profiles for doing just that...

 

[We_are_Stevo]

I would be interested to see where the perfect 90° would run through - canti stud / canti to cable fixing / straddle ?

WD

It's called the 'Yoke Angle'

 

[FluffyChicken]

I would be interested to see where the perfect 90° would run through - canti stud / canti to cable fixing / straddle ?

WD

Buggered if I'm going to go through working, but distant memory puts it something like this, ... all lines and angles not to scale and maybe scribbled here or there.) probably plenty more I could scribble on there.

Somebody please feel free to tell it all properly rather than muse and scribble like me.

But basically the arms are set so when the cable is pulled you are not banding

Bad picture. But what stevo is, I think, actually saying (just a bad picture to use as an example) is at some point the '90 degree point at the canti arm, you are not pulling the canti arm 'up' away from the boss, or pulling it into the boss, however slight, meaning all the force gets transferred into the pads. Often in the middle of the bolt where you clamp it down in low profiles.
The XTR in the picture would need the pads further from the arms as they normally would be set up. Of course you then hit other factors like pad stud strength (they bend), rim design and clearance.
The straddle position is often at 90 degree's but really depends on you lever pull and what is practically possible, that and it looks nice.

look forward to others drawings when I wake up

 

[We_are_Stevo]

Actually that's quite good...

 

[michael franks]

Some Shimano straddles have 'A' or 'B' stamped on them - is there any significance in that? They're identical in every other way.

BTW Feetabix - you wrote:

I spent two hours on Sunday autosol'ing my stheno rims and spokes until I could brush my teeth in them.....a waste of time some may say but they look ace!....

I would call it time well spent - I have the same rims

 

[FluffyChicken]

Some Shimano straddles have 'A' or 'B' stamped on them - is there any significance in that? They're identical in every other way.

BTW Feetabix - you wrote:

I spent two hours on Sunday autosol'ing my stheno rims and spokes until I could brush my teeth in them.....a waste of time some may say but they look ace!....

I would call it time well spent - I have the same rims

The A and the B (and C, D, E, s ?) signifies it's length.
there will be a number after it.
They are used (well the older style proset) with er ProSet Setting tools, which I guess stevo had. They make it easier all around.
Newer style ones have markings on them to set them up.


http://www.retrobike.co.uk/gallery2/v/M ... ewsIndex=3
http://www.retrobike.co.uk/gallery2/v/M ... ewsIndex=3

 

[michael franks]

Thanks for all the info Fluffy - great job

 

[We_are_Stevo]

The A and the B (and C, D, E, s ?) signifies it's length.
there will be a number after it.
They are used (well the older style proset) with er ProSet Setting tools, which I guess stevo had. They make it easier all around.
Newer style ones have markings on them to set them up.

ProSet! D'you think I could bl**dy remember that last night? Could I b*ll*cks!

I am so glad you posted that!

 

[feetabix]

I would be interested to see where the perfect 90° would run through - canti stud / canti to cable fixing / straddle ?

WD

Buggered if I'm going to go through working, but distant memory puts it something like this, ... all lines and angles not to scale and maybe scribbled here or there.) probably plenty more I could scribble on there.

Somebody please feel free to tell it all properly rather than muse and scribble like me.

But basically the arms are set so when the cable is pulled you are not banding

Bad picture. But what stevo is, I think, actually saying (just a bad picture to use as an example) is at some point the '90 degree point at the canti arm, you are not pulling the canti arm 'up' away from the boss, or pulling it into the boss, however slight, meaning all the force gets transferred into the pads. Often in the middle of the bolt where you clamp it down in low profiles.
The XTR in the picture would need the pads further from the arms as they normally would be set up. Of course you then hit other factors like pad stud strength (they bend), rim design and clearance.
The straddle position is often at 90 degree's but really depends on you lever pull and what is practically possible, that and it looks nice.

look forward to others drawings when I wake up

that, i think, is what i was trying to say........the 90 degree angle on the pic of the shimano cantis looks good but due to the shape of the cantis the reality is that the canti is being pulled upward against the boss as well as inward toward the rim, thus losing efficiency......the outer pink lines on fluffy's diagram is where the forces should be applied.....

 

[RobMac]

Forget the length/angle, keep it as close as you dare to the tyre (without being silly) and keep the brake blocks set close to the rims.