to turn the rotors or not (1 Viewer)

[tirewater]

If your pads & rotors are within tolerance, simply leave them alone for now.

When you do your knuckle, couple of tips:

-ensure the bottom four studs on the knuckle are tight prior to reassembling.
-don't over pack the back part of the birfield joint with grease. this will help prevent getting too much grease sucked into the axle housing

 

[Ebag333]

Huh?

Please explain.

It's simple. If your brakes can lock up the tires (assuming ABS is disabled), then "improving" your brakes won't improve your braking performance. And you can easily lock up tires on dry pavement in an 80 if your brakes are even in halfway decent condition, I've done it more than once.

Brakes can't stop a tire from spinning any more than not spinning at all.

Once you reach that point, improvements on your braking system is a waste, it doesn't give any additional benefit. At that point, the only benefit you will see is increasing the friction between the pavement and the vehicle...in other words your tires.

Tires have a huge impact on braking performance, yet I see people go through all sorts of gyrations to try and improving braking performance...and ignore the tire.

 

[rolliges]

So you're saying 'brakes either work or they do not.' And that there is no in-between working and not working.

So if brake pads were reduced down to 5% of original then they would still work as new. And putting on new pads would not improve on brake performance?

Risky logic.

 

[Ebag333]

So you're saying 'brakes either work or they do not.' And that there is no in-between working and not working.

So if brake pads were reduced down to 5% of original then they would still work as new. And putting on new pads would not improve on brake performance?

Risky logic.

Nope.

I even said if you're replacing old and worn components, you'll see an improvement, even with crappy/cheap aftermarket parts. Those crappy/cheap parts won't function as well as new OEM (or equivalent parts).

My point is, if your braking system is maintained (in other words not old and worn out), it can lock up the tire no problem. There's a whole range of "in-between working and not working", with the best being able to lock up the tires and the worst doing nothing. If your brakes are old and not maintained, then you'll fall somewhere in that in between area (hopefully not so much that you can't stop!). But if your braking system is in good shape, then stopping is no issue.

To put it another way, the whole idea of the brakes are to stop the tire from spinning (the ABS system actually degrades braking performance, but that's a different topic). If the brakes are in good shape they'll easily stop it from spinning completely. This isn't true on all vehicles, lots of vehicles have trouble locking the tires, which is why putting on premium/performance parts improves braking performance, the OEM system isn't performing at the peak. You can lock up the tires even with 35's or 37's in an 80, which says a lot about how much overhead there is in the braking system. I've driven trucks that roll 28's that have trouble locking them up on dry pavement....with larger tires the brakes wouldn't have a chance.

Long story short, 80's have top of the line brakes that are over sized for the application. Like a lot of other components on an 80.

 

[KliersLC]

Nope.

I even said if you're replacing old and worn components, you'll see an improvement, even with crappy/cheap aftermarket parts. Those crappy/cheap parts won't function as well as new OEM (or equivalent parts).

My point is, if your braking system is maintained (in other words not old and worn out), it can lock up the tire no problem. There's a whole range of "in-between working and not working", with the best being able to lock up the tires and the worst doing nothing. If your brakes are old and not maintained, then you'll fall somewhere in that in between area (hopefully not so much that you can't stop!). But if your braking system is in good shape, then stopping is no issue.

To put it another way, the whole idea of the brakes are to stop the tire from spinning (the ABS system actually degrades braking performance, but that's a different topic). If the brakes are in good shape they'll easily stop it from spinning completely. This isn't true on all vehicles, lots of vehicles have trouble locking the tires, which is why putting on premium/performance parts improves braking performance, the OEM system isn't performing at the peak. You can lock up the tires even with 35's or 37's in an 80, which says a lot about how much overhead there is in the braking system. I've driven trucks that roll 28's that have trouble locking them up on dry pavement....with larger tires the brakes wouldn't have a chance.

Long story short, 80's have top of the line brakes that are over sized for the application. Like a lot of other components on an 80.

Not quite true. Many of the performance upgrades for brakes focus on longevity under stress. If you are driving a heavily loaded rig in the mountains you may find yourself a victim of brake fade. (The 80 is slow enough that I don't think brake fade could he acomplished anywhere else...) there are two ways to combat brake fade (other than driving carefully). First is to increase the thermal mass of the rotor (i.e. bigger rotors and spreading the heat out via a correspondingly larger pad) This results in the rotor taking longer to heat up and fade--hopefully you will have a chance to rest/cool the brakes before they fade. The second method is to improve the rotor cooling during use ( drilled, slotted and the like). this can help, but you also reduce the thermal mass and those rotors tend to crack if they get overheated.

So, brakes are brakes, but there is a little more to the story.

 

[Ebag333]

Not quite true. Many of the performance upgrades for brakes focus on longevity under stress. If you are driving a heavily loaded rig in the mountains you may find yourself a victim of brake fade. (The 80 is slow enough that I don't think brake fade could he acomplished anywhere else...) there are two ways to combat brake fade (other than driving carefully). First is to increase the thermal mass of the rotor (i.e. bigger rotors and spreading the heat out via a correspondingly larger pad) This results in the rotor taking longer to heat up and fade--hopefully you will have a chance to rest/cool the brakes before they fade. The second method is to improve the rotor cooling during use ( drilled, slotted and the like). this can help, but you also reduce the thermal mass and those rotors tend to crack if they get overheated.

So, brakes are brakes, but there is a little more to the story.

All that is true. But part of it is given the 80's rotors are truly massive, they don't tend to heat up very much unless you're pushing it far too hard. The 100 series pads can help some in this area, and is a good upgrade if you're doing anything that might cause brake fade. They're in the truck as we tow a 3k lb boat up and down some very steep hills....despite this I've never experienced brake fade in either of my 80's, even with stock pads.

 

[Stylo07]

I thought that if one is going to upgrade to 100 series pads, the rotor should be turned to provide a fresh, smooth surface to which the larger pad can become acclimated?

 

[gotmud]

Turning a rotor before installing new pads falls under "best practices". Personally, I rarely turn rotors unless it is to simply have a fresh surface for a new set of pads.
While I'm sure there is room to improve on an 80's braking system, I'm quite satisfied with how well they work in the first place (assuming every component is in top shape).

 

[86tuning]

the problem is that 80's rotors are difficult to turn. It can be done on-the-car but off the car it would be a huge amount of work to remove, etc. Might as well just replace it at that point.

 

[rhyary]

Brakes can't stop a tire from spinning any more than not spinning at all.

.

no exactly.
Brakes are not only about one stop.
Imagine driving in to Denver on that long long down hill. Repeated use of the brakes will generate heat that a single stop does not. Heat deteriorate braking. How well the brakes dissipate heat is part of the brake system performance.

Rami

Sent from my iPhone using IH8MUD

 

['74 UA FJ]

Geez, people. They're brakes.

I wouldn't turn or replace the rotors if they weren't warped or excessively worn.