Slotted/Heavy duty rotors?

[Kegan]

I am having an issue with severe front end vibration/shimmy, particularly after driving for several hours and typically going down hill (often at or near highway speeds). The problem is a somewhat intermittent. I have had the rotors checked earlier this month and the mechanic said they are fine; though they did replace the bushings. After some additional research, I am suspecting that I need to upgrade to a heavier duty/heat dispersing rotors (drilled slotted).

Thoughts, opinions or feedback? Anyone else have a similar problem and how did you resolve it? One such rotor suggested is posted below for reference. Thanks in advance
2008 Roadtrek Poplar 210.

https://www.summitracing.com/parts/PWR-K6561

[booster]

Originally Posted by Kegan

I am having an issue with severe front end vibration/shimmy, particularly after driving for several hours and typically going down hill (often at or near highway speeds). The problem is a somewhat intermittent. I have had the rotors checked earlier this month and the mechanic said they are fine; though they did replace the bushings. After some additional research, I am suspecting that I need to upgrade to a heavier duty/heat dispersing rotors (drilled slotted).

Thoughts, opinions or feedback? Anyone else have a similar problem and how did you resolve it? One such rotor suggested is posted below for reference. Thanks in advance
2008 Roadtrek Poplar 210.

https://www.summitracing.com/parts/PWR-K6561

Many people here and elsewhere have had that issue with the Chevies.


There are also many discussions of it on this forum so searching could bring up lots of reading. It is commonly called "brake juddering" on here but many terms should show up.



Bottom line is that the main part of the problem is the Chevy ceramic pads which don't work well in heavy vehicles. The rotors are a very minimal part of the problem and stock rotors will work as will any higher quality replacement rotors. Slotting and drilling are not conducive to heavy vehicle use and can cause more problems than they solve, so plain or very slightly grooved rotors work the best IMO.


For pads, you need to get away from ceramic and get to high end semi metallic pads. Counterintuitively, ceramic pads don't handle the heat as well and cause the issue. Many here, us included, use Hawk light truck heavy duty semi metallic pads with very good results. Others have used major brand "police", "heavy duty" pads successfully. Yes, they will make a lot of brake dust on the wheels, however, which isn't a great thing, but necessary.


The actual cause of the juddering when hot and goes away when cooled down is because of what is called a "transfer layer" of brake pad material that is transferred to and remains on the rotor surface. It needs to be smooth and uniformly the same thickness to work properly. The ceramic pads don't put on a good, uniform, layer so when the rotors get hot the transfer layer gets different amounts of friction at the various points around the rotors. The transfer layer itself changes friction with heat so thin and thick areas are hotter or cooler causing the pulsing.


Because of the above it is possible that your rotors are not bad at all. Just have them checked for runout and minimum thickness and if they pass those checks sand the faces down to clean cast iron. You can also have them turned to get cleaned, but that also makes them thinner and more prone to heating up faster.



Get the good pads, you should be able to find part numbers in the other discussions, and breake them in EXACTLY to the manufactured recommendations which are also contrary to common logic because it will be quite aggressive. This is needed to get the brakes hot enough to put a good transfer layer on the rotors and babying them early on won't be adequate. At the last step of break in, it is very likely you will be able to smell a bit of hot brake smell if you have windows open.

[peteco]

Originally Posted by booster

Many people here and elsewhere have had that issue with the Chevies.

There are also many discussions of it on this forum so searching could bring up lots of reading. It is commonly called "brake juddering" on here but many terms should show up.

Bottom line is that the main part of the problem is the Chevy ceramic pads which don't work well in heavy vehicles. The rotors are a very minimal part of the problem and stock rotors will work as will any higher quality replacement rotors. Slotting and drilling are not conducive to heavy vehicle use and can cause more problems than they solve, so plain or very slightly grooved rotors work the best IMO.

For pads, you need to get away from ceramic and get to high end semi metallic pads. Counterintuitively, ceramic pads don't handle the heat as well and cause the issue. Many here, us included, use Hawk light truck heavy duty semi metallic pads with very good results. Others have used major brand "police", "heavy duty" pads successfully. Yes, they will make a lot of brake dust on the wheels, however, which isn't a great thing, but necessary.

The actual cause of the juddering when hot and goes away when cooled down is because of what is called a "transfer layer" of brake pad material that is transferred to and remains on the rotor surface. It needs to be smooth and uniformly the same thickness to work properly. The ceramic pads don't put on a good, uniform, layer so when the rotors get hot the transfer layer gets different amounts of friction at the various points around the rotors. The transfer layer itself changes friction with heat so thin and thick areas are hotter or cooler causing the pulsing.

Because of the above it is possible that your rotors are not bad at all. Just have them checked for runout and minimum thickness and if they pass those checks sand the faces down to clean cast iron. You can also have them turned to get cleaned, but that also makes them thinner and more prone to heating up faster.

Get the good pads, you should be able to find part numbers in the other discussions, and breake them in EXACTLY to the manufactured recommendations which are also contrary to common logic because it will be quite aggressive. This is needed to get the brakes hot enough to put a good transfer layer on the rotors and babying them early on won't be adequate. At the last step of break in, it is very likely you will be able to smell a bit of hot brake smell if you have windows open.

Excellent summary. I would add that even the semi-metallic pads can end up with a non-uniform transfer layer over time. That happened to me over about 40-50,000 miles, where I started having some shudder while braking hard with my Hawk pads and rotors. I think it was caused by my tendency to brake as softly as possible by anticipating stops long in advance. What is needed is an occasional set of heavy braking events to heat the pads to maintain the transfer layer. I checked thickness and runout and all was good, so I sanded off the transfer layer (see my post about this) and rebedded the pads and have had no problems since. I now do a heavy braking occasionally to maintain.

[TX-Trek]

Following the comments above, I use ceramic pads in all of our vehicles except for our 210P.

I've had good luck with Wagner severe duty semi-metallic pads front and rear. They've seen some abuse on some of the grades we've encountered, even with engine braking. Seem to be doing OK and yes, they do dust up.

Additional suggestion, be sure all caliper pins are properly lubed with a non-petroleum based lube. I use Syl-Glyde. You want the calipers to apply evenly, sticking pins can cause uneven pad wear and pulsing.

[carlN]

I put a pair of Powerstop drilled slotted on front with hawk SUV pads and the stop like you throw out a anchor.. they are a semi metallic race type pad and do need to be hammered on every so often.. I try to break easy most of the time but every so often you gotta take it in deep and hit the brakes hard.. when you hit the brakes hard it take a sec for them to catch but when they do HOLD ON..

When doing down a long grade I will make sure it clear behind me and to keep speed under control stab the brakes HARD getting speed back under 50.. I usually only do about 60 to 62 then i brake hard.. get off the brakes to let them cool and if you need to control speed jab them hard again..

Highly recommend the powerstop and hawk SUV pads for superior braking and long life.

2003 ford f-250 7.3L diesel pull 30 ft 8400 lb airstream..

[Jfstang]

A brake fluid flush with fresh DOT 4, and perhaps a new set of flex lines to replace the originals that may be pushing 20-ish years old or more on some of our RV's, might be worthwhile ideas.