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Vibration at 50 to 60 mph coasting in neutral after rear brake shoes



 
 
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  #11  
Old February 13th 18, 07:12 PM posted to alt.home.repair,rec.autos.tech,ca.driving
ultred ragnusen
external usenet poster
 
Posts: 54
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

wrote:

> On some it does - but then you need to manually adjust the handbrake
> (e-brake) linkage AFTER the shoes have adjusted - and this
> meansbacking off the e-brake adjustment first.


Thank you for helping me understand what went wrong where I realize it's
hard for you to help given the little information I know about it.

On this vehicle, braking in referse does not adjust the rear brakes.
The continual adjustment of the rear brakes is only by the parking brake.

> Youstill have not said what vehicle this is - and sincethere areSO
> MANY differentsetups for brakes, this is important information.


It's a 2002 Toyota Tacoma.

Mainly I ass-u-med that the parking brake would adjust the brake shoes,
since that's what it does every day.

What I mostly want to understand is WHY the parking brake adjustment didn't
work.

My main assumption was that the parking brake adjustment is the same as the
manual star adjustment.

If that's correct, then I don't see how the parking brake adjustment is any
different than twisting the star adjuster, but it apparently is (somehow).

That's my main confusion which I hope someone can help me better
understand.
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  #12  
Old February 14th 18, 03:38 AM posted to alt.home.repair,rec.autos.tech,ca.driving
Clare Snyder
external usenet poster
 
Posts: 70
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

On Tue, 13 Feb 2018 11:12:46 -0800, ultred ragnusen
> wrote:

> wrote:
>
>> On some it does - but then you need to manually adjust the handbrake
>> (e-brake) linkage AFTER the shoes have adjusted - and this
>> meansbacking off the e-brake adjustment first.

>
>Thank you for helping me understand what went wrong where I realize it's
>hard for you to help given the little information I know about it.
>
>On this vehicle, braking in referse does not adjust the rear brakes.
>The continual adjustment of the rear brakes is only by the parking brake.
>
>> Youstill have not said what vehicle this is - and sincethere areSO
>> MANY differentsetups for brakes, this is important information.

>
>It's a 2002 Toyota Tacoma.


Look at http://www.tacomahq.com/wp-content/u...drum_brake.gif

Note ther pin at the top. If the adjuster at the bottomis not
adjusted long enough and the handbrake cable is too tight, the cable
will hold the shoes out close tothe drum, giving a good pedal but the
ends of the shoes are not in contact with the pin. One might br, or
the other, but not both.

When the adjuster is properly adjusted and the cable is NOT too tight,
both ends are against the pin untill the cyl expands, causing the
leading shoe to contact the drum, and the friction of the liniung
against the drum caused the shoe to rotate with the drum, carrying
through the adjuster, and firmly wedging the rear shoe into the drum.
>
>Mainly I ass-u-med that the parking brake would adjust the brake shoes,
>since that's what it does every day.
>


If the cable is too short it cannot adjust the shoes out far enough
because the cable "false adjusts" the shoes.
>What I mostly want to understand is WHY the parking brake adjustment didn't
>work.


The cable was too tight
>
>My main assumption was that the parking brake adjustment is the same as the
>manual star adjustment.


It is
>
>If that's correct, then I don't see how the parking brake adjustment is any
>different than twisting the star adjuster, but it apparently is (somehow).


The cable was too tight
>
>That's my main confusion which I hope someone can help me better
>understand.



I hope this helps

And the automatic adkusters on a Taco are actuated by firmly applying
the brakes in reverse. With the ebrake cables loose.
  #13  
Old February 14th 18, 04:31 AM posted to alt.home.repair,rec.autos.tech,ca.driving
ultred ragnusen
external usenet poster
 
Posts: 54
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

wrote:

> The cable was too tight


That's basically the net effect.
Thanks.

It's a lesson well learned to follow the factory procedure.

I don't know how people do this job without the large calipers though.
  #14  
Old February 14th 18, 06:24 AM posted to alt.home.repair,rec.autos.tech,ca.driving
Clare Snyder
external usenet poster
 
Posts: 70
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

On Tue, 13 Feb 2018 20:31:06 -0800, ultred ragnusen
> wrote:

> wrote:
>
>> The cable was too tight

>
>That's basically the net effect.
>Thanks.
>
>It's a lesson well learned to follow the factory procedure.
>
>I don't know how people do this job without the large calipers though.

For years I've done it by trial and error - adjust the shoes to what
I think is right, then dry-fit the drum - too loose, pull it off and
adjust up. Don't fit? back it off and try again. Usually only a few
minutes. Then fine adjust with the brake spoon. ALWAYS check the
ebrake cables - and REPLACE if they are sticky - or you'll just end up
doing the job again. Also make sure you have the wheel brake
adjustment right BEFORE applying the e-brake -particularly if there is
any chance it has a self adjusting e-brake linkage. Do it on a Ford
Aerostar and you'll find out why REAL fast!! You'll spend half an hour
backing off the cable adjuster - - - -
  #15  
Old February 14th 18, 07:37 PM posted to alt.home.repair,rec.autos.tech,ca.driving
ultred ragnusen
external usenet poster
 
Posts: 54
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

wrote:

> For years I've done it by trial and error - adjust the shoes to what
> I think is right, then dry-fit the drum - too loose, pull it off and
> adjust up. Don't fit? back it off and try again. Usually only a few
> minutes. Then fine adjust with the brake spoon. ALWAYS check the
> ebrake cables - and REPLACE if they are sticky - or you'll just end up
> doing the job again. Also make sure you have the wheel brake
> adjustment right BEFORE applying the e-brake -particularly if there is
> any chance it has a self adjusting e-brake linkage. Do it on a Ford
> Aerostar and you'll find out why REAL fast!! You'll spend half an hour
> backing off the cable adjuster - - - -


I am very glad you explained the error which I agree with you that it was a
big make for me to ass-u-me that since the daily automatic adjustment keeps
the shoes adjusted, that a manual adjustment would do the same.

I also agree with you that there seem to be three major methods of
determining the /initial/ adjustment, all of which use the manual star
adjuster (and each of which has a flaw for noobs like I am).

1. As you said, one method is to repeatedly dry fit the drum from far too
loose to just a teeny bit too tight, and then, as a final step, back off
the star adjuster a bit.

2. A similar method is to put the drum on the vehicle once, and adjust the
star adjuster until it just begins to feel friction.

3. The third method is to measure the width of the drum and the shoes to be
about 1/2 mm (20 thousandths of an inch) difference.

Each method works, but all three have noob flaws:
1. You have to know what to feel for.
2. Again, you have to know what to feel for.
3. You have to have the tools to measure drum width to reasonable accuracy.

I thank you for helping me understand what caused the vibration at speed,
which, as you said, I think it was that the shoes were too loose and the
brake cable too tight. I don't understand exactly how but that combination
caused a floating which caused the leading shoe to grab at speed which
caused the wobble.

It's a good thing this was found on a short test run, and not after long
term damage might have been incurred.

Thank you for your comprehensive explanation, where I apologize that I just
don't understand everything you said about why the shoes were floating but
that's my problem in comprehension and not yours in explanation.
  #16  
Old February 14th 18, 09:33 PM posted to alt.home.repair,rec.autos.tech,ca.driving
Clare Snyder
external usenet poster
 
Posts: 70
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

On Wed, 14 Feb 2018 11:37:48 -0800, ultred ragnusen
> wrote:

> wrote:
>
>> For years I've done it by trial and error - adjust the shoes to what
>> I think is right, then dry-fit the drum - too loose, pull it off and
>> adjust up. Don't fit? back it off and try again. Usually only a few
>> minutes. Then fine adjust with the brake spoon. ALWAYS check the
>> ebrake cables - and REPLACE if they are sticky - or you'll just end up
>> doing the job again. Also make sure you have the wheel brake
>> adjustment right BEFORE applying the e-brake -particularly if there is
>> any chance it has a self adjusting e-brake linkage. Do it on a Ford
>> Aerostar and you'll find out why REAL fast!! You'll spend half an hour
>> backing off the cable adjuster - - - -

>
>I am very glad you explained the error which I agree with you that it was a
>big make for me to ass-u-me that since the daily automatic adjustment keeps
>the shoes adjusted, that a manual adjustment would do the same.
>
>I also agree with you that there seem to be three major methods of
>determining the /initial/ adjustment, all of which use the manual star
>adjuster (and each of which has a flaw for noobs like I am).
>
>1. As you said, one method is to repeatedly dry fit the drum from far too
>loose to just a teeny bit too tight, and then, as a final step, back off
>the star adjuster a bit.
>
>2. A similar method is to put the drum on the vehicle once, and adjust the
>star adjuster until it just begins to feel friction.
>
>3. The third method is to measure the width of the drum and the shoes to be
>about 1/2 mm (20 thousandths of an inch) difference.
>
>Each method works, but all three have noob flaws:
>1. You have to know what to feel for.
>2. Again, you have to know what to feel for.
>3. You have to have the tools to measure drum width to reasonable accuracy.
>
>I thank you for helping me understand what caused the vibration at speed,
>which, as you said, I think it was that the shoes were too loose and the
>brake cable too tight. I don't understand exactly how but that combination
>caused a floating which caused the leading shoe to grab at speed which
>caused the wobble.
>
>It's a good thing this was found on a short test run, and not after long
>term damage might have been incurred.
>
>Thank you for your comprehensive explanation, where I apologize that I just
>don't understand everything you said about why the shoes were floating but
>that's my problem in comprehension and not yours in explanation.

When I was teaching the trade I would have had a brake unit in front
of me, and you face to face - which would make the "understanding" a
whole lot easier.

Next time you have a drum off, pull the emergency on part way and
then lookat what has happened to the position of the shoes. Check
closely before and after. then picture what would happen if the front
shoe was "picked up" by the drum and consider the e-brake cable to be
a spring. You'll get the picture.
  #17  
Old February 15th 18, 07:50 PM posted to alt.home.repair,rec.autos.tech,ca.driving
ultred ragnusen
external usenet poster
 
Posts: 54
Default Vibration at 50 to 60 mph coasting in neutral after rear brake shoes

wrote:

> When I was teaching the trade I would have had a brake unit in front
> of me, and you face to face - which would make the "understanding" a
> whole lot easier.


I agree with you that it must work the way you say, mechanically, but my
brain is having trouble visualizing how all the pieces work together in
that I know only how the pieces fit together, but I can't "touch" them and
"push" them and "wiggle" them in my brain to see how they affect each other
in real life.
http://i.cubeupload.com/Ktc8zF.jpg

> Next time you have a drum off, pull the emergency on part way and
> then lookat what has happened to the position of the shoes. Check
> closely before and after. then picture what would happen if the front
> shoe was "picked up" by the drum and consider the e-brake cable to be
> a spring. You'll get the picture.


Thanks for that explanation which is hard to write because you're
describing a moving system with springs and interactions.

The key I learned is that the star adjustment step just can't be skipped!

To try to give back to the group for the kind help, here is the tool I made
to make it easier to hold back the locking plate off the star adjuster. The
wire came out of a hot water heater I took apart to see how it works
inside, and it's about 6 to 8 inches long, where the critical part is the
painted area that starts 1-3/8" from the end, and is 3/8" long, which I
filed down to make an indent (since the whiteout paint wouldn't likely last
long).
http://i.cubeupload.com/LzvBps.jpg

The tool is to push away the plate which locks the star wheel he
http://i.cubeupload.com/Mgwt06.jpg

This is all you see from behind, if your head was as thin as a cellphone:
http://i.cubeupload.com/IQdwAl.jpg

The tool needs to go in deeper than a noob like me would think it needs to:
http://i.cubeupload.com/GuF7mL.jpg

Once it touches the plate, you need to push another 3/8" inward:
http://i.cubeupload.com/Hu4wpu.jpg

Then you have to hold it in that position while you get a chisel:
http://i.cubeupload.com/ALZOLp.jpg

This is what it looks like from the other side when its in position:
http://i.cubeupload.com/RyDEnN.jpg

You will have measured the drum diameter already at around 11-1/2 inches:
http://i.cubeupload.com/LMSp4y.jpg

You adjust shoes until they are 1/2mm (20 thousandths) less than drums:
http://i.cubeupload.com/RhPoYX.jpg
 




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