Front axle brake shoes wear out faster than rear axle brake shoes?

[porkysplace]

Assuming the rear wheels don't lock every time you step on the brakes... then all wheels will do (almost) identical number of revolutions during a deceleration from speed X down to speed Y. That, while the pressure applied to every single of all 12 brake shoes is exactly the same. Why should they wear differently?


G.

In the cicy world there is a primary brake shoe ( front ) and a secondary brake shoe ( rear ) . the primary has a longer pad than the secondary because it does more braking. The military uses the same size shoes for inventory purposes. Somewhere I have the old Raybestos manuals from the 70's that explain it in detail .

 

[DieselBob]

In the cicy world there is a primary brake shoe ( front ) and a secondary brake shoe ( rear ) . the primary has a longer pad than the secondary because it does more braking. The military uses the same size shoes for inventory purposes. Somewhere I have the old Raybestos manuals from the 70's that explain it in detail .

Not exactly correct in my experience. That is true for passenger cars and light trucks but not medium and heavy trucks of the same period. All the heavy trucks of the 70‘s, 80‘s I worked on did not use the “primary” “secondary” shoe arrangement. They had same size shoes in both positions except they had smaller shoes on the front axle if they had any at all.

 

[welldigger]

This is why when you stand up on the brake pedal in an all drum brake equipped 383 Road Runner or 396 Chevelle, the front rolls and the rear smokes!

This is easily explained by the fact that the rear of the car is lighter than the front already. Then when you stand on the brakes the weight shifts forward even more. This situation would easily lead to accelerated front brake wear since the front brakes are still turning and the back is locked (not turning).

I have yet to service any vehicle with front and rear brakes where the fronts didn't wear faster than the rears. With one exception. My dad's Harley trike. Only because he likes using the rear brakes almost exclusively for whatever strange reason.

All of my trucks, cars, motorcycles (that I ride), atvs, etc. go through front pads/ shoes at almost double the rate of the rears. It's just physics.

 

[welldigger]

Assuming the rear wheels don't lock every time you step on the brakes... then all wheels will do (almost) identical number of revolutions during a deceleration from speed X down to speed Y. That, while the pressure applied to every single of all 12 brake shoes is exactly the same. Why should they wear differently?


G.

Because the tires change diameter. When you apply the brakes the weight shifts forward. This "squishes" the front tires and shrinks their radius. The rears being "relieved" so to speak, of some of the vehicle weight can actually have their radius increased. This can lead to a difference in rpms of each axle.

 

[rustystud]

Not exactly correct in my experience. That is true for passenger cars and light trucks but not medium and heavy trucks of the same period. All the heavy trucks of the 70‘s, 80‘s I worked on did not use the “primary” “secondary” shoe arrangement. They had same size shoes in both positions except they had smaller shoes on the front axle if they had any at all.

That is true but, the pad material is usually different from front to rear shoe. In fact some shoes I have rebuilt the top pad was different then the bottom pad. For those wondering what I'm talking about, in big rigs the brake shoe has two parts, the top pad and the bottom pad. They are usually bolted on.

 

[gringeltaube]

Because the tires change diameter. When you apply the brakes the weight shifts forward. This "squishes" the front tires and shrinks their radius. The rears being "relieved" so to speak, of some of the vehicle weight can actually have their radius increased. This can lead to a difference in rpms of each axle.

Agreed. That's what I meant with "almost" identical revs. - when braking normally.
I can imagine though, that during extreme braking the loaded radius for the (9.00-20's) fronts would change from say 19" down to 18", maybe. And the rears, from 19.5" to 20". That would explain a 8-10%-difference in wear, at most... and only for that kind of braking maneuvers. It does not explain why front brake shoes from a Deuce would wear twice as fast...


G.

 

[quickfarms]

Do you know if all of the brakes were adjusted properly/the same? Maybe the rear brakes aren't adjusted up as tight as the front?

This is probably the reason.

The brakes probably have never been adjusted correctly or this is the first time the brakes have been inspected.

On the big trucks we set the rear brakes tighter than the front.

 

[Wildchild467]

I don’t drive my truck like a race car so I don’t think that has a huge factor in brake shoe wear. Valid points though! I have always kept by brake shoes in adjustment and they have always worked very well I think. It is going to be a while until I get to changing the brake shoes. I know I have enough meat on them to get me into early summer. I plan on picking up a set of brake shoes at the Findlay Rally. Again, I know I have enough brakes and I will be fine until then. When I change my brake shoes, I will measure the diameter of my wheel cylinders in the front.

Now that I think about it, I think I remember getting higher brake drum temperatures in the front than the rear.

Who knows, maybe when Private Pyle changed my wheel cylinders he upgraded me to the A3 wheel cylinders in the front!

 

[gringeltaube]

....................................
Now that I think about it, I think I remember getting higher brake drum temperatures in the front than the rear.

Who knows, maybe when Private Pyle changed my wheel cylinders he upgraded me to the A3 wheel cylinders in the front!

I kind of hope that that's what happened... otherwise we have another mystery going on, here...

How does it stop when you really step on the pedal? Have you ever locked the rears? ... Or even the front tires??


G.

 

[frank8003]

This is just a wonder
This site is up there with Wikipedia
Thank you all

 

[Wildchild467]

On pavement, I think I have locked up one of the rears before, but not all of them when I hit the brakes hard. I have never locked up a front that I remember. It stops very well and will almost lift a passenger out of their seat. I have had no issue with feeling like I never had enough brakes for the truck. Obviously the truck is big and only has single circuit brakes, so I drive it appropriately. Again, I have always stayed on top of the PM on the truck so it has been good to me.

 

[gringeltaube]

I'm really tempted now to swap my front WC's, for a pair of A3's and see what it does. For a (nose-heavy) winch-truck which runs almost empty most of the time that could be a real upgrade, actually.
Someone on here has probably tried this out already...?


G.

 

[peashooter]

I'm really tempted now to swap my front WC's, for a pair of A3's and see what it does. For a (nose-heavy) winch-truck which runs almost empty most of the time that could be a real upgrade, actually.
Someone on here has probably tried this out already...?


G.

I'm doing this on my front axle. In fact I bought enough 1.5" diameter (A3) WC that I could potentially do all my wheels if I someday wanted..... (assuming my M/C and 2 airpacks had the available volume to do that safely).

I also found a 1.75" diameter bore front wheel cylinder that would fit!

 

[Flyingvan911]

My front and rear shoes seem to be pretty even. My '08 Ford E150 also wears the pads down evenly front vs rear. I think the key is to be gentle and slow down smoothly and with gentle pressure. The harder you stop the more weight/momentum shifts forward and wears the front pads. (I must say, with the van I think a properly adjusted proportioning valve helps also.)

 

[peashooter]

My front and rear shoes seem to be pretty even. My '08 Ford E150 also wears the pads down evenly front vs rear. I think the key is to be gentle and slow down smoothly and with gentle pressure. The harder you stop the more weight/momentum shifts forward and wears the front pads. (I must say, with the van I think a properly adjusted proportioning valve helps also.)

The van probably has larger pads in the front though?

 

[Wildchild467]

I'm really tempted now to swap my front WC's, for a pair of A3's and see what it does. For a (nose-heavy) winch-truck which runs almost empty most of the time that could be a real upgrade, actually.
Someone on here has probably tried this out already...?


G.

You are welcome to come over and test mine out if I have the 1.5" wheel cylinders!

Mine is also a winch truck. Like I said, I think all my brakes are working fine. I have put a lot of miles on it and have taken care of it, so I would think its normal. I would like to pull he rear duals and pack the wheel bearings on that side before I make my trip out here to Michigan. I should measure the other wheel cylinders to make sure they are the 1-3/8" bore just for kicks. I bet if I put the 1.5" bore wheel cylinders on the back it would make the backs lock up easier and not be as fun to drive, possibly more dangerous on slippery road. Im having visions of the 900 series test video of ABS vs. non ABS. Thoughts?

 

[gringeltaube]

Oh yes, I would gladly do a test drive there... regardless of what size the cylinders are!


G.

 

[wb9btz]

Recovery4x4's response in post #8 is right on. This information was provided to me (and the rest of my class) by our Basic Automotive Class instructor in in College in 1972. It is also why for many years disc brakes were applied only to the front wheels.

 

[JasonS]

I'm doing this on my front axle. In fact I bought enough 1.5" diameter (A3) WC that I could potentially do all my wheels if I someday wanted..... (assuming my M/C and 2 airpacks had the available volume to do that safely).

I also found a 1.75" diameter bore front wheel cylinder that would fit!

Part numbers and sources would be greatly appreciated.

 

[JasonS]

Recovery4x4's response in post #8 is right on. This information was provided to me (and the rest of my class) by our Basic Automotive Class instructor in in College in 1972. It is also why for many years disc brakes were applied only to the front wheels.

But, think about it. All brake shoes in a common hydraulic system press on the drum with the same force and all wheels turn at approximately the same speed. They will, then, wear out at the same rate. Weight transfer doesn't affect any of the aforementioned parameters.

Weight transfer ENABLES you to use more braking force at the front without causing a skid. In these types of vehicles, the front brakes wear out faster.