Do you swap your brake shoes?

[jstoezel]

Hi:

A long time ago I read on this forum that some people swap the brake shoes top/bottom (at the front) between race week-ends (can't find the thread anymore).

Is this something that is recommended, even after the shoes have been bedded?

Jean

[FV80]

Jean,
Many of the top drivers swap shoes "occasionally". Not EVERY weekend (I think), but the purpose of the swap is simply to equalize the wear. The leading shoe wears something over twice as fast as the trailing shoe. For MY purposes, I just let the leading shoe wear until it's "pretty close" to the limit (based on my imminent racing plans) and I then swap the 'better looking' shoe to the 'worn out' position and put a NEW shoe in the trailing spot. That way, I don't have to worry about bedding in the new shoe (at least I DON'T worry about it) and I always (ALMOST always <g>) have good brakes when I need them. There is a very minor performance issue, but the COST and effort issues are most important to me

Steve, FV80

[brian]

I prefer to swap every other weekend. Wait too long and the shoes wear lopsidedly and won't work as well. Doing it more often will mean less bed in time as well.

[hojo]

for clarification would the leading shoe on the Front left be the top shoe since the brake cylinder is pushing upward there and the rotation of the tire is upward at that point (rolling forward)

thanks

[jstoezel]

Hi Steve and Brian:

Thanks for the replies.

I had asked the same question to the people who manufacture the brake shoes, and they had advised not to swap them... I'm not sure they are very interested in getting the brake shoes to last longer though.

Will swap mine then.

Jean

Jean,
Many of the top drivers swap shoes "occasionally". Not EVERY weekend (I think), but the purpose of the swap is simply to equalize the wear. The leading shoe wears something over twice as fast as the trailing shoe. For MY purposes, I just let the leading shoe wear until it's "pretty close" to the limit (based on my imminent racing plans) and I then swap the 'better looking' shoe to the 'worn out' position and put a NEW shoe in the trailing spot. That way, I don't have to worry about bedding in the new shoe (at least I DON'T worry about it) and I always (ALMOST always <g>) have good brakes when I need them. There is a very minor performance issue, but the COST and effort issues are most important to me

Steve, FV80

[brian]

The way I was taught to recognize the leading shoe is that the wheel cylinder, or activating force, is on the front end of the shoe relative to the rotation of the wheel. That means that on the left front the leading shoe is on the bottom and top on the right side. Frankly, I don't think the Carbo tech folks really understand our situation in vees. Since all shoe brake systems rely on some flexing of the shoes to provide full contact, it requires a fair amount of hydraulic pressure. Since the coefficient of friction or drag is so high on newer shoe friction materials, the wheels will lock up before the shoe is flexed properly. When I prep high grip shoes, I look to reduce the arc clearances and minimize the requirement for the shoe to flex. The next time you get new shoes, lay the shoe in the drum and pinch down on one end. Measure the clearance at the other end of the shoe I like to see a space that's under .050. If the space is greater, not only will the shoe wear poorly, it won't stop as well. If the appears to be no space, check the center of the shoe with a feeler gauge to see if the shoe is too large for the drum diameter. Arching of shoes is a forbidden art according to OSHA, but some folks will still do it. I still have my old AAMCO machine. Carbo tech makes an over size shoe that must be used if your drums have been turned. We learned that torquing a straight wheel on the drum before turning it will produce superior results on track. Hope this helps...... no charge.

[hojo]

thanks so i had it backwards as far as what i thought leading shoe was then.

i have stock pads anyway but i can see how radiusing them and checking the clearances will make a big difference in overall stopping power vs just locking them up.

more surface area = more heat generation and dissipation per square inch = better stopping power.

[cendiv37]

The way I was taught to recognize the leading shoe is that the wheel cylinder, or activating force, is on the front end of the shoe relative to the rotation of the wheel. That means that on the left front the leading shoe is on the bottom and top on the right side.

Brian, I think you have it mostly right. The term "leading" shoe probably was substituted for "primary" shoe somewhere along the line. The "primary" shoe is the one that is "self energized" by the forces and geometry of wheel cylinder, friction of drum against the shoe and the pivot point on the far end of the shoe. If the wheel cylinder is at the top, above the axle, which I believe is common, then the "primary" shoe is the "leading" shoe: in front of the axle in the direction of travel.

For VW shoe layout, on the rear brakes, the term leading is appropriate as defined above. On the fronts, the "leading" shoe is the top shoe - on both sides.

All things being equal, the leading shoe does more work than the trailing shoe so if the shoes are identical, the leading shoe will be the one that wears faster.

This should agree with what people see in terms of wear rate.
I searched the house for an old text book to confirm all this but I cannot find one

The tapered adjuster screws are undoubtedly VW's attempt to tweak the balance between the two shoes.

[BLS]

I searched the house for an old text book to confirm all this but I cannot find one

I'm not a text book, but wife says I'm old. You're explanation is correct.

[hojo]

ok so now i see i contradiction here!
according to bruce my original thought was correct about which shoe is the leading shoe. but brians comments suggested otherwise. anyway i'm not losing sleep over it.

how about the leading shoe is the one that crosses the start/finish line first! hehe

[Rickydel]

Put your finger on the drum, right about where the wheel cylinder is.
Rotate the drum in the direction of travel. That first shoe is the "leading" or "Primary" shoe, regardless of it being front/back, left/right.

[hojo]

cheers,

i had it right the first time

[brian]

sounds like we all have heard different explanations. If the primary or leading shoe is the top shoe on both sides, why do they wear differently side to side? I always thought it was because the wheel cylinder either pushes into the direction of wheel travel (primary) or with the direction of wheel travel( secondary).

[cendiv37]

They wear differently side to side due to differences in shoe materials, drums materials and stiffness, fit to drum, fit to backing plate, friction to backing plate and adjusters, drum finish, etc., etc., not due to flipping primary shoe from top to bottom.

Backing plate side, inside vs. outside of drum, left or right side of car all don't matter. The only thing that matters is the direction of FORWARD rotation of the drum relative to the shoe face and shoe contact points (wheel cyl. vs. adjuster). When thinking about this, imagine the backing plates aren't there and look at left and right brakes simultaneously from the same side of the car and you will see that the shoes don't car whether they are on the left or right side. When trying to slow the car as it is moving forward, relative to the wheel cylinders, they see the same forces in the same directions on both left and right sides.

My guess is that you are subconsciously thinking about rotating the wheel "forward" the same direction relative to YOU when standing on opposite sides of the car. I know I do this when spinning the wheels while adjusting the brakes. When facing the wheel from the right side, "forward" is CW. Forward is CCW from the left. Obvious when you actually think about it, yet when I first kneel down in front of the second wheel to adjust it's brake, I inevitably spin it first the same way I was spinning the previous wheel and have to consciously remind myself to spin it FORWARD.

[BLS]

What is called the leading shoe is the top one on both sides of the VW. I have often heard people refer to the leading shoe as the front shoe when the shoes are oriented vertically, sometimes incorrectly. The leading shoe will always tighten itself due to the forces pushing the shoe into the drum while the trailing shoe is strictly the force from the wheel cylinder. Backing up will reverse the situation.

[Rolling Stone]

What is called the leading shoe is the top one on both sides of the VW. I have often heard people refer to the leading shoe as the front shoe when the shoes are oriented vertically, sometimes incorrectly. The leading shoe will always tighten itself due to the forces pushing the shoe into the drum while the trailing shoe is strictly the force from the wheel cylinder. Backing up will reverse the situation.

I agree..................I always drive around at the track before racing and hit the brakes going forward then I reverse at a fair rate and hit the brakes,I do it a few times,works for me.

[smsazzy]

Once your brakes start to wear, you can also just pull of an axle tube and flip the ring and pinion. Then you can try the courses with rear steering. The brake wear will even out this way.

[brian]

I think Stephen's been smoking something! I've been really straining to understand what everyone's saying here and once again, Bruce has cleaned up my thinking a bit. Ah, dyslexia at it's best. Remember, the VW has a fixed adjustment system that isolates the shoes from one another. The classic example of primary/secondary shoe system has a floating adjuster that allows force transfer to the lower portion of the primary shoe. Our brakes can not do this. Can they Bruce? That, combined with the tapered adjusters add some other activities to our shoes. I believe the VW upgraded, tapered adjusters help by keeping the shoe centered in the drum. If you find that your shoes free up when you back up,and you are running tapered adjusters, there may be something making your shoes stick. Just like hitting the pedal over and over while adjusting the brakes. Check your backing plates for grooves under the shoe on the pads. Grind them smooth, and if the backing plate is getting thin, weld some material on it and regrind. Shoes that have worn lopsidedly, will stick as well.