Shuddering while braking..any thoughts, inputs?

[htheduck]

Hello fellow members, just seeking thoughts/inputs/recommendations to my persistent situation: upon braking the (brakes or rods?) seem to shudder in a mild and annoying way : usually 30mph-10mph stops.

What's been done so far: new tires, alignment, re-cut rotors...I can't determine where to go next? Or what to look for...any thoughts?

Thanks in advance.

 

[rangerj]

You had the rotors cut, but did you replace the brake pads? Was the shudder present before all the work was done? Wheels (lug nuts)that are not properly torqued on will cause brake rotor warping. If the rotors were warped before they were cut then the pads are worn unevenly and should have been replaced.

Another possibility is the wheel bearings and/or the lower control arm and stabilizer bar bushings. What is the condition of the sub-frame bushings?

Inner and/or outer tie rod ends can also cause the problem you describe. However any of the suspension and/or steering problems should have been noticed when you had the car aligned.

Just a few thoughts, rangerj

 

[TankII]

Strut-Rod bushings. Fixes this problem almost every time.

TankII

 

[revhardSHO]

I always replace rotors they are so cheap why not just go new?

 

[sdpatt]

It's likely still the rotors. The accuracy of the resurfacing depends upon how well they were mounted in the lathe. You should also check your hubs for uneven rust at the rotor mounting face. Even a new rotor won't spin true if the hub face is not square.

 

[SonicRiot]

Just because the rotors were recut does NOT mean they are not warped. Check the runout.

Also, check the rears. If it is occuring during light braking, it may be the rear rotors and not the front. Front rotors will cause more amplified problems under harder braking.

As for the rotors being cheap, just what do you consider cheap? I bought front rotors to the tune of $45 a piece. Forget the made in Taiwain crap!

 

[38SHO]

I got mine for 12....

 

[sdpatt]

$19.99 and they have made it through two road race course runs and one spirited Lone Star SHO Club drive in addition to about 50,000 miles of "regular' driving. Do you think I got my money's worth?

 

[SonicRiot]

You must be running some soft pads!!!

I'm running Moroso calipers and rotors with ceramic pads. The pads are so tough that I had to remachine the rotors after 10K miles because they blued and lost bite and increased my stopping distance.

If I was to do it again, I'd spend my money on fixed calipers or at least multipiston calipers. Single piston floating calipers suck and fade with heat (mechanical) and are a waste of time, though it was a considerable upgrade over stock.

As for the pads, they have to be warm to work well, so it's not great on a wet, cool morning when I first pull out of the driveway or if I've been cruising without braking for a long period of time and need to suddenly stop. I wouldn't recommend them for most drivers unless the car is driven in a "sporting mannor" on the street on a regular basis . I'd go with a Bendix hi-performance semi-met in the future.


SO! The reason I bought such pricey rotors was because they are tough and have a lot of material on them to enable a future regrind and not warp from the super tough pads. In the future, I'd get slotted and/or crossdrilled rotors to help ventilation, but were talking big dough then...

Cheap rotors or thin rotors warp, very easily. The last place that did my sister's 1998 Contour's front rotors machined them to just above discard spec. They blued and warped in 500 miles and I ended up replacing them for her because the vibration was ridiculous on the highway.


An alternative possibility is unbalanced wheels, but *most* of the time, it causes a vibration under many conditions, coast included.

 

[DHMag]

$19.99 and they have made it through two road race course runs and one spirited Lone Star SHO Club drive in addition to about 50,000 miles of "regular' driving. Do you think I got my money's worth?

Scott, the 3 month warranty rotors are now 17.99 and the 2 years are 28.99 each. if ya need some new rotors,or any other auto parts from da Zone, lemme know.

 

[DHMag]

You must be running some soft pads!!!

Scott, as well as myself, is running PFCM pads with stock rotors. i dont consider the PF pads to be soft by any means, unless compared to a race pad like EBC RedStuff. but then again, the PF pads arent considered race pads.

 

[k_mesaros]

You had the rotors cut, but did you replace the brake pads? If the rotors were warped before they were cut then the pads are worn unevenly and should have been replaced.

The pads CANNOT wear unevenly due to warped rotors. The warped rotors will just have high and low points on the face of them, so when they are rotating the piston will move in and out when the pad crosses from high to low. In and out movement will wear the pads nice and flat, you should just scuff up the pads to get the glaze off and ensure that they break in with the new rotor surface. You can check if it is the front or rears by applying your parking brake while driving. If the car still shudders while braking only with the parking brake it is your rear rotors.

Kevin

 

[Shoaz]

FWIW, "warped" rotors are almost always still mechanically flat. The pulsation in the pedal is feedback from uneven surface loading of the pad material onto the disk. There are a number of things that can cause this, but a hard stop to a dead stop with a few seconds holding the brake on is often a cause. This gets the pad and rotor hot and creates a section where a lot of pad material is imprinted onto the disk (more than in other areas).

The result is a disk with an uneven coefficient of friction as it rotates, which is what causes the vibration and feedback through the pedal.

Turning the rotor removes the surface layer that is unevenly loaded and exposes fresh metal. If you're careful and don't make any hard stops (e.g., drive like a sane person and just make normal, gentle brake applications for a while) the fresh disk face will load evenly with pad material and the vibration will stay away.

For track rotors there is a "bedding" process to make this happen quickly, but it isn't really necessary for a street car that sees normal use.

 

[TankII]

New rotors - Check.
New brake bads - Check.
New caliper pin kits - Check.
Bleed brakes - Check.
Get alignment - Check.
Still shaking badly - Replace Strut-rod bushings. Worked 100% of the time for me and others I have told about it.

TankII

 

[jessemachone]

I just replaced both lower control arms this past week end as preventitive maintenance and was suprised that a wheel vibration that I had associated with wheel balance had disappeared. My car has 179k on it and I'm pretty sure that they are the originals. I am whipping it into shape slowly but surely.
As for the discussion on the brake rotor vibration... why would you even thing about removing more metal from a warped rotor in order to get it true again? All that does is make the problem go away until you slam on the brakes again. Think about it ... when you machine a rotor, you are taking material away that would be used to dissapate (spell check) heat more effectively.

 

[htheduck]

Can someone post a diagram of where my strut rod bushings are; and cost, part numbers?

Thanks to everyone for all the input.