Rear brake torque arm, frame mount vs. swing arm mount.

[Firehawk068]

I am not familiar with the GSXR wheel swap.......
I have a question for you.
Does the caliper mounting bracket pivot on a bearing of some sort?
By torquing the axle nut tight you are locking it in place otherwise, and having the brake torque arm mounted to anything other than the swingarm will want to push the caliper backwards, and pull it forwards when the swingarm moves up and down.
Just want to make sure you are not about to embark on some sort of unsafe riding experience.

[Arnie]

I am not familiar with the GSXR wheel swap.......
I have a question for you.
Does the caliper mounting bracket pivot on a bearing of some sort?
By torquing the axle nut tight you are locking it in place otherwise, and having the brake torque arm mounted to anything other than the swingarm will want to push the caliper backwards, and pull it forwards when the swingarm moves up and down.
Just want to make sure you are not about to embark on some sort of unsafe riding experience.

There is a bush in the brake mounting bracket which allows movement.

Connecting the brake torque arm to a fixed part of the chassis allows the brake to not affect the suspension as the wheel moves up and down and for the braking force to be isolated from chassis movement.

Arnie

[Firehawk068]

Thanks Arnie......
I have never seen a GSXR caliper bracket. I was unaware that they are allowed to pivot........
But.....I still think mounting the torque arm to the frame, and not the swingarm would cause the braking force to load, and unload the suspension.......also, the torque arm would have to have some provision for pivoting up and down at each end as the swingarm moves up and down. Doesn't seem like you would be able to bolt it securely at each end.....
Maybe the suspension guru's can chime in.....I'm just curious

[ian.z9]

The suzuki torque arm is fitted with a bearing in the end attached to the frame,thus allowing movement with the swinging arm.I wanted to fit the torque arm to the swinging arm by welding a mounting lug on the underside of the arm.But by removing the right exhaust damper there was just enough room to use the footrest mounting hole.Much quicker and as I cant weld aluminium (or anything else!) it was the way to go for me.

[ian.z9]

Here's a pic to show the nicer line of the torque arm.It just fits above the exhaust damper and I used a 75mm M6 bolt to fix it through the footrest bracket hole.I couldn't find a cap head to match dammit!
The big plus is you keep the centrestand.

[Arnie]

Thanks Arnie......
I have never seen a GSXR caliper bracket. I was unaware that they are allowed to pivot........
But.....I still think mounting the torque arm to the frame, and not the swingarm would cause the braking force to load, and unload the suspension.......also, the torque arm would have to have some provision for pivoting up and down at each end as the swingarm moves up and down. Doesn't seem like you would be able to bolt it securely at each end.....
Maybe the suspension guru's can chime in.....I'm just curious

Alan,

Both ends of the torque arm are allowed to pivot.  The brake caliper bracket can also rotate on the axle.  This allows the brake and the suspension to operate independantly if the torque arm is attached to the frame.
If you attach the torque arm to the swingarm then the braking will impart some force into the suspension.  You could also key the brake directly to the swingarm to prevent it rotating, but again, this will affect suspension action.

In the picture you can just see the forked end of the torque arm.  The mount bolt goes through a bearing on the caliper.

Arnie

[SlowOldGuy]

I'm not sure that I understand what you're describing, Arnie.  If the rear caliper is mounted to the swingarm, all the force stays in the swingarm and should not affect suspension action (given that the swingarm is sufficiently stiff to not distort). 

Kind of like a single front brake doesn't torque the wheel one way or the other since all the force is applied to the fork slider.

Am I missing something?

DavidR.

[racerman_27410]

I'm not sure that I understand what you're describing, Arnie.  If the rear caliper is mounted to the swingarm, all the force stays in the swingarm and should not affect suspension action (given that the swingarm is sufficiently stiff to not distort). 

Kind of like a single front brake doesn't torque the wheel one way or the other since all the force is applied to the fork slider.

Am I missing something?

DavidR.

+1        IMO the brake torque arm should move in the same plane as the swingarm.... easiest way to accomplish that is have it attached to the swimgarm..

KOokaloo!
http://s47.photobucket.com/albums/f198/Racerman27410/ECFR%202010%20Birthday%20ride/?action=view&current=ECFR2010203.mp4

[Arnie]

I'm not sure that I understand what you're describing, Arnie.  If the rear caliper is mounted to the swingarm, all the force stays in the swingarm and should not affect suspension action (given that the swingarm is sufficiently stiff to not distort). 

Kind of like a single front brake doesn't torque the wheel one way or the other since all the force is applied to the fork slider.

Am I missing something?

DavidR.

Its not that the brake tries to twist the swingarm laterally, but affects it vertically.  I don't know if force is sufficient to make a noticable difference, but as with a shaft drive torque reaction, the brake forces try to compress or extend the suspension if the brake is fixed to the swingarm.  The closer to the swingarm axle or ideally to the chassis the torqe arm anchor is, the less the effect.

Arnie

[Firehawk068]

I think it should be the other way around.......
If you mount the brake torque arm to the swingarm, It does NOT produce torque to the suspension.....
If you mount it to the frame, it will introduce braking torque to the swingarm.....maybe not enough to feel in a striaght line, but if you were using rear brake in a corner, I think it would upset your suspension......

[SlowOldGuy]

Let me try this analogy:

I'm standing on one side of the swingarm and pulling up on it REALLY hard.  Am I affecting the suspension?  I don't think so.  All I'm doing is inducing stress in that arm of the swingarm which it resists beacuse it is much stronger than I am.

Now, If my feet are on the frame and I pull up on the swingarm, then I will induce movement into the suspension.

At least that's how I'm picturing it in my mind.

DavidR.

[Pat Conlon]

Arnie, David is correct.

Both ends of the torque arm are allowed to pivot......
Arnie

The above statement is Correct

 ".....The brake caliper bracket can also rotate on the axle....."  
Arnie

The above statement is correct.

"...... This allows the brake and the suspension to operate independantly if the torque arm is attached to the frame....."
Arnie

The above statement is incorrect. Reason: If the brake torque arm is connected to the frame, when the brake is applied and the torque arm is under tension, and the swing arm moves up and down, the tension load is transmitted to the frame which can interfere with the movement of the swingarm as well as the possibility of uneven loading on the caliper/rotor as it rotates caliper back and forth (when the swingarm moves)

".....If you attach the torque arm to the swingarm then the braking will impart some force into the suspension.
Arnie

This statement is incorrect. You WANT the torque arm attached to the swing arm. By doing so, the swing arm can travel thru it's full range of motion without any loading that would happen from a frame mounted torque arm.

 You could also key the brake directly to the swingarm to prevent it rotating, but again, this will affect suspension action.
Arnie

Correct:  Many bikes have no torque arm but the caliper mounting arm is keyed to the swing arm to transfer the tension loads.
Incorrect:  Again, by doing this (keying the caliper arm to the swing arm) you will not affect the suspension travel. The loads are transmitted to the swing arm.

[Harvy]

Quote from: Arnie on 21 September 2010, 01:01:21
".....The brake caliper bracket can also rotate on the axle....." 
Arnie

The above statement is correct.

Are you sure...........it will rotate on the axle if the axle is not torqued up, but it seems to me that there is no way it can rotate when torqued up, as it bares on the swingarm.

It seems to me that the calliper bracket torque arm must be attached to the swingarm (thus forming a triangle). If its bolted to the frame somewhere, you have a trapezium which, as the swingarm moves up and down, tries to increase/decrease the length of the lower side of the trap..... and as its a fixed length, the only way for it not to affect suspension travel would be to allow the calliper bracket to pivot on the axle..... and as I said above, this is not possible with the axle torqued up.


OR am I wrong about the bracket not pivoting?

Harvy

[Pat Conlon]

Quote from: Arnie on 21 September 2010, 01:01:21
".....The brake caliper bracket can also rotate on the axle....."  
Arnie

The above statement is correct.

Are you sure...........it will rotate on the axle if the axle is not torqued up, but it seems to me that there is no way it can rotate when torqued up, as it bares on the swingarm......OR am I wrong about the bracket not pivoting?

Harvy

Harvy, rest assured, even with the axle nut torqued and pressure squeezing against the caliper bracket, the UNRESTRAINED caliper bracket and caliper WILL rotate on the axle if you apply the rear brake.

Here's a test: Take off your torque arm, go out for a ride, step on the brake pedal and see what happens...

[Harvy]

Here's a test: Take off your torque arm, go out for a ride, step on the brake pedal and see what happens...

I will take your word for it Pat.......... but I would still rather have the stay arm bolted to the swingarm.   

Harvy