Third wishe for 2016 forlfiled: Yam TD rear brake

yves norton seeley · Dec 26, 2016

Hi there,
I had three wishes for 2016:
An Yam TD/TZ 260mm 4ls front brake: Done
An Ceriani GP front fork: Done
An Yam TD/TZ 200mm rear brake: Just done

LIke I say in a previous topic, I gat power enough, and now the most important to me is the look of my Seeley.
I did't not like the look of the disc brakes and Roadholder fork, thats why I change the front disc for a Yam TD/TZ 260mm 4ls front brake and the fork for a Ceriani GP
So far so good, but the rear disc was still there and don't match the front of my Seeley so I start searching for a Yam TD/TZ rear brake.
And I found one: an original, not a replica, I paid 650 Euros for the complete weel includind DID rim
The weel and brake where in good condition, but still need a lot of work to make it near perfect and to fit it in the Seeley.
If you think that this work can be done in two days, you are dreaming, it take me 14 days of labour to do the job:
First problem: The shaft from the Yam is 20mm and the one from the Seeley is 17mm, So I put a sleeve in the brake plate to reduce it to 17mm and change the three berarings to 17mm ID.
Second problem: The cosmetic, after 40 years you can imagine that everithing was not very shiny, I dismanteld the weel and aquablast the drum, polish the brake plate and rim, the rim give me a lot of work to polish becouse a DID rim is anodized, and this is hard to remove, and i am not satisfied with the result so I will probably change the DID frim for a Borrani later...
After I respoke the weel with stainless spokes with the rim in the middel, no offset.
The most difficult was to align the rear weel whit the front, I make different bushes and use shim washers to have it nearly perfect.
So when the weels are in line, the next job was to put the rear sprocket in line with the front sprocket, i have to put the weel in the lathe and remove 6mm from the side of the drum where the rear sprocket is fit, so job done and checked with a Lazer beam.
The anchor bar from the disc caliper was to short, so I make a longer one
The last problem was the cable, I treceive the original one with the weel, but it was make for a right hand brake pedal, and i have a left hand pedal, so I make a new cabel.
Dont ask me how the drum is working, they put salt on the roads, this will be for later, I keep you posted
Yves

Fast Eddie · Dec 26, 2016

Very nice Yves!

You must surely be running out of things to do on this bike ?!?

yves norton seeley · Dec 26, 2016

Fast Eddie said:
Very nice Yves!

You must surely be running out of things to do on this bike ?!?

Not at all, the Seeley is still " works in progress " my wishes for 2017 : I find the tank hugly, I still have the original Seeley tank,but the capacity of the original is to low, thats why I use the IOM tank at the moment but my dream is to ask a belgiam tank shop to do a kind of replica of the MV 750S tank
Yves

nortonspeed · Dec 26, 2016

yves norton seeley said:
Very nice however as far as I can see the brake plate rod is attached to the fixed frame. This is wrong the rod should be connected to the swing arm to follow the exact circular movement of the swing arm.

lcrken · Dec 26, 2016

Maybe not. Moving the brake stay mounting point up or down on the frame lets you change the amount of squat (or anti-squat) you get under rear wheel braking. Normally that's only of concern to racers, but there's no reason you can't do it that way on a street bike too.

Ken

acotrel · Dec 26, 2016

On my bike the other end of the brake stay is attached to the engine plate below the pivot, making a parallelogram. I cannot remember even using the rear brake, although it must happen. Have you fitted a bearing inside where the TD backing plate fits onto the axle ?

yves norton seeley · Dec 26, 2016

nortonspeed said:
yves norton seeley said:

Very nice however as far as I can see the brake plate rod is attached to the fixed frame. This is wrong the rod should be connected to the swing arm to follow the exact circular movement of the swing arm.

Click to expand...

You can be right
The caliper of my disc braque was fit the same way, of course the caliper was floating on the shaft, in the case of the braque plate it's sandwiched in the swing arm
Yves

yves norton seeley · Dec 26, 2016

acotrel said:
On my bike the other end of the brake stay is attached to the engine plate below the pivot, making a parallelogram. I cannot remember even using the rear brake, although it must happen. Have you fitted a bearing inside where the TD backing plate fits onto the axle ?

No, just a bush to reduce the ID to 17mm, originaly there is no bearing
Yves

yves norton seeley · Dec 26, 2016

lcrken said:
Maybe not. Moving the brake stay mounting point up or down on the frame lets you change the amount of squat (or anti-squat) you get under rear wheel braking. Normally that's only of concern to racers, but there's no reason you can't do it that way on a street bike too.

Ken

Sorry for my poor english, but what do you mean with squat or anti-squat?

yves norton seeley · Dec 26, 2016

nortonspeed said:
yves norton seeley said:

Very nice however as far as I can see the brake plate rod is attached to the fixed frame. This is wrong the rod should be connected to the swing arm to follow the exact circular movement of the swing arm.

Click to expand...

I look to a pic of a TD/TZ and the rod is attached to the rear of the footrest???

nortonspeed · Dec 26, 2016

If your brake plate is in fixed position (not being able to twist on the axle) then the brake stay mounting point must be fixed to the swing arm.

o0norton0o · Dec 26, 2016

I adapted a yamaha rear drum brake and hub to my commando last year, although I did it to use a cast aluminum yamaha wheel. Here's a picture below.

IF your brake drum face is NOT part of your wheel spacer assembly for the axl, then you CAN attach the torque arm of the brake to the frame... BUT if the drum face is part of the axl spacers which are under pressure from the axle nut, then the torque arm must be attached to the swingarm, so the drum face doesn't rotate when the bike squats...

In my case. I welded a tab on the bottom of the swingarm to attach the brake torque arm which you can't see in the picture because it's behind the Z plate.

There are 2 issues that must be addressed.

1)The obvious one is that you have to have a torque arm for the brake plate so it doesn't spin when you apply the brake.

2) You don't want the brake face plate to rotate when the bike squats, if it's face plate is under pressure as part of the axle spacer assembly, so it's torque arm has to be attached to the swingarm, NOT the frame.

*(IF the brake face plate isn't part of the axle spacer assembly under pressure from the axl nut, then the slight rotation induced into the plate by the torque arm when the bike squats wont be a problem)

yves norton seeley · Dec 27, 2016

o0norton0o said:
I adapted a yamaha rear drum brake and hub to my commando last year, although I did it to use a cast aluminum yamaha wheel. Here's a picture below.

IF your brake drum face is NOT part of your wheel spacer assembly for the axl, then you CAN attach the torque arm of the brake to the frame... BUT if the drum face is part of the axl spacers which are under pressure from the axle nut, then the torque arm must be attached to the swingarm, so the drum face doesn't rotate when the bike squats...

In my case. I welded a tab on the bottom of the swingarm to attach the brake torque arm which you can't see in the picture because it's behind the Z plate.

There are 2 issues that must be addressed.

1)The obvious one is that you have to have a torque arm for the brake plate so it doesn't spin when you apply the brake.

2) You don't want the brake face plate to rotate when the bike squats, if it's face plate is under pressure as part of the axle spacer assembly, so it's torque arm has to be attached to the swingarm, NOT the frame.

*(IF the brake face plate isn't part of the axle spacer assembly under pressure from the axl nut, then the slight rotation induced into the plate by the torque arm when the bike squats wont be a problem)

This is very clear, thanks
In my case the face plate is under pressure as part of the axle assembly, so I will fit the torque arm to the swingarm in the comming days, I must find a way to do this without welding becouse the swingarm is chromed
Yves

yves norton seeley · Dec 27, 2016

Shame on me that I did sutch a mistaque with the torque bar after 50 years working on motorcycles, a real shame!
I am very gratfull to the members of the forum that discover the mistake on the pic.
A lot of thanks
Yves

Nater_Potater · Dec 27, 2016

yves norton seeley said:
Shame on me that I did sutch a mistaque with the torque bar after 50 years working on motorcycles, a real shame!
I am very gratfull to the members of the forum that discover the mistake on the pic.
A lot of thanks
Yves

It's arguably better to have the backing plate floating on the axle and anchored to the frame, as this helps avoid having the rear wheel "hop" under heavy braking. Since you've done such a nice job with the drag link, how about boring the backing plate oversize, then lathing a bushing that lets the backing plate rotate while it takes the clamping force of the axle nut?

Nathan

lcrken · Dec 27, 2016

yves norton seeley said:
lcrken said:

Maybe not. Moving the brake stay mounting point up or down on the frame lets you change the amount of squat (or anti-squat) you get under rear wheel braking. Normally that's only of concern to racers, but there's no reason you can't do it that way on a street bike too.

Ken

Click to expand...

Sorry for my poor english, but what do you mean with squat or anti-squat?

Because your backing plate is fixed in positon by being clamped between the swinging arm ends, the squat and anti-squat question doesn't really apply to your bike, particularly now that you are going to change the brake stay mounting point to the swinging arm. I had assumed that the brake backing plate was floating on the axle, not clamped, when I made that comment.

I probably should have used the terms rise and anti-rise instead. Squat and anti-squat refer to changes in the attitude (pitch and height) of the sprung part of the motorcycle under acceleration and braking forces (also described as load transfer). The terminology can get a bit confusing, because the terms dive and anti-dive, lift and anti-lift, and rise and anti-rise are also used. The most common use of squat is to describe the behavior of the rear under acceleration, but it has also been applied to behavior of the rear under rear brake use. Since we're only talking about the effect from the rear brake, and anti-rise seems to be the more common term, I will use that. When the brake stay is fixed to the swinging arm, the force from rear braking is transferred to the swinging arm and acts to compress the rear suspension. That's called anti-rise because it counters the normal tendency of the rear to rise under braking because of load transfer. Unfortunately, it can also produce too much anti-rise effect, which can act to reduce the load on the rear tire, and lead to less effective rear wheel braking. And, as Nathan pointed out, it is also more likely to have problems with rear wheel hop. If the brake backing plate is free to float on the axle, with the brake stay pivot mounted on the frame, the location of the pivot can be used to adjust the amount of anti-rise. In general, the design goal is to have enough anti-rise to cancel out the normal rear suspension reaction to rear wheel braking.

This issue was more important to race bikes in the past, because the rear brake was actually used to slow the bike down. I recall it still being discussed with some interest back in the early '70s. With modern bikes, the front brake design and modern tire compounds mean the rear brake really adds very little under heavy breaking. Modern bikes are more likely to use spring and damping rates to control the anti-rise effect, and just tie the rear caliper to the swinging arm. That seems to work just fine.

Ken

o0norton0o · Dec 27, 2016

Yves, IF the brake plate spacer is thick enough, you could also drill it out and put a bushing in there to carry the brake plate and allow it to rotate slightly when the bike squats when the swingarm moves. This way the bushing becomes part of the axle shim assembly, but not the brake plate. This would allow you to leave the torque arm where it is because the minor rotation of the brake plate doesn't harm anything so long as it's not part of the axle shims.... (hopefully that explanation is clearly stated)

The other really cool thing about moving the brake to the other side, is that you can get change the rear sprocket size easily. You can even buy a split rear sprocket so you can change gear ratio without removing the rear wheel.

I bought my custom sprocket from http://sprocketspecialists.com/rear-spr ... -patterns/ I chose the standard 40 tooth rear sprocket, so I am running a 21 front sprocket and a 40 rear sprocket. It cost about $80. I may buy another rear sprocket at some point in the 38 tooth range. The nice thing about changing the rear sprocket is the adjustment is twice as fine as changing the front sprocket since the front to rear tooth ratio is nearly 2 to 1.

Fantastic bike Yves....

Edited to add: Sorry for the redundant post... nater posted while I was writing my post...

yves norton seeley · Dec 28, 2016

o0norton0o said:
Yves, IF the brake plate spacer is thick enough, you could also drill it out and put a bushing in there to carry the brake plate and allow it to rotate slightly when the bike squats when the swingarm moves. This way the bushing becomes part of the axle shim assembly, but not the brake plate. This would allow you to leave the torque arm where it is because the minor rotation of the brake plate doesn't harm anything so long as it's not part of the axle shims.... (hopefully that explanation is clearly stated)

The other really cool thing about moving the brake to the other side, is that you can get change the rear sprocket size easily. You can even buy a split rear sprocket so you can change gear ratio without removing the rear wheel.

I bought my custom sprocket from http://sprocketspecialists.com/rear-spr ... -patterns/ I chose the standard 40 tooth rear sprocket, so I am running a 21 front sprocket and a 40 rear sprocket. It cost about $80. I may buy another rear sprocket at some point in the 38 tooth range. The nice thing about changing the rear sprocket is the adjustment is twice as fine as changing the front sprocket since the front to rear tooth ratio is nearly 2 to 1.

Fantastic bike Yves....

Edited to add: Sorry for the redundant post... nater posted while I was writing my post...

Thanks for the details, If I understand wel i gat two options:
1: fit the anchor bar to the swing arm
2: put a busch in the brake plate and keep the anchor bar on the frame
I think I will keep the second option, the plate from my disc caliper was also on a bronze busch, turning over a spacer busch and with the anchor bar on the frame and the bike was very neutral when braking.
Keep you posted
Yves

splatt · Dec 28, 2016

If you can bore the brake plate out about 6mm a steel or stainless sleeve as the spacer run straight on the alloy hub would work fine, not a lot of point running alloy on bronze, and the spacer would be stronger
You can also get thin walled tophat bushes that would stop the end faces wearing, normally 1mm thick

norsa1 · Dec 30, 2016

Does the Yam TD rear brake incorporate a cush drive?

Third wishe for 2016 forlfiled: Yam TD rear brake

yves norton seeley

Fast Eddie

yves norton seeley

nortonspeed

Guest

lcrken

acotrel

yves norton seeley

yves norton seeley

yves norton seeley

yves norton seeley

nortonspeed

Guest

o0norton0o

yves norton seeley

yves norton seeley

Nater_Potater

lcrken

o0norton0o

yves norton seeley

splatt

norsa1

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