The two-week vacation driving around Southern B C and Northern Washington was good. Now it's back to work and wearing socks . Only one day with a rain storm.
Installed new vented rotors on the rear just before leaving-- no vibrations when braking.
Went down one mountain pass with up to 15% grades at 95F. No spectacular braking as the traffic was slow and almost continuous. Then coming down after a day of mt biking on Silver Star the old vibration came back.
Rear Rotors were from BrakePerformance.com
Not Pleased --will try the factory ones.
Subtle (normally aspirated engines suck):
05 Legacy GT Wagon with Cobb chip.
62 Alfa Romeo Spider- had a 1.6 L with 80 hp, now 2 L with 160 torque. Curb weight 2050 lbs.
93 Leg Twgn fmic, vf34, etc. ((sold))
Yeah, it would be strange for it to be the rears over the fronts. Not much power goes to the rear comparatively either. I warped non-cryo rotors in so that they'd pulse intermittently in weeks, badly enough to pulse strongly the majority of the time in a few months.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
I have crappy rotors and crappy pads and absolutely beat on my brakes sometimes. I was in a road rally in may and actually had smoke coming out of the wheels at a control. All my lugs are properly torqued and I bedded in my brakes according to stop tech. No vibration. One of these days I'll do that brake swap. I've had wrx calipers and pads and ss lines for over a year now.
I've never heard of anyone warping rear rotors. Are you sure it's the rears? Any way you can check with a gauge or something fixed to see if they have a wobble? Could it be pad residue built up on the rotors?
'94 Legacy Touring wagon. Quicksilver metallic. WRX rims, Whiteline ALK, SS brakelines, GR2s, alum. coolant tank. Gone, but not forgotten
'99 NSX, Alex Zanardi edition, #11/50. All stock & red 2 go
At hard braking from higher speeds the vibs are only minor.
However, on moderate braking at slow speeds it is getting worse and last night even noticed a slight shudder while turning at slow speeds with no accelerator or brakes.
Something wrong with the tie-rods or whatever
Subtle (normally aspirated engines suck):
05 Legacy GT Wagon with Cobb chip.
62 Alfa Romeo Spider- had a 1.6 L with 80 hp, now 2 L with 160 torque. Curb weight 2050 lbs.
93 Leg Twgn fmic, vf34, etc. ((sold))
It's uneven layers of pad material on the rotors that causes pulsing (slide-bite-slide-bite..etc.)
Resurface the rotors(very fine grit sandpaper?Scotchbrite pad?), and rebed(?) the pads.
My experience on this is that I bot the twgn 4 years ago and earlier in the year things were beginning to vibrate under hard braking.
In preparing for some track time, I put on the AP Racing front kit with new SS line to the backs as well. Pads are Ferodo DS 2500 front and back.
Both installs were properly bedded in.
Although diminished, vibs were still there. Put on new vented rear rotors and the moderate vibs went away.
Then, as in the initial post, they came back.
Going out to PDM Racing to have the ride height lowered to stock now that the back road season is over, and with redoing the alignment and all I'm sure we'll figure out the problem.---
We live in hope.
Subtle (normally aspirated engines suck):
05 Legacy GT Wagon with Cobb chip.
62 Alfa Romeo Spider- had a 1.6 L with 80 hp, now 2 L with 160 torque. Curb weight 2050 lbs.
93 Leg Twgn fmic, vf34, etc. ((sold))
earlier, you mentioned vibrations while turning, but without applying brakes. That my friend, is a wheel that is out of balance. it will also cause pulsations when braking. but 100%+ its your wheels and they need to be spin balanced. could be otherthings in addition, but vibrations whole turning and no brake useage=time to go to a tire shop to have a spin balance, or maybe even new tires.
91 Legacy Sport Sedan 4eat
91crx si 165k
91 Civic RT4WD manual trans 168k
91crx Si 40.5k
85 BRAT Gl 140
97 SVX 74k
It's uneven layers of pad material on the rotors that causes pulsing (slide-bite-slide-bite..etc.)
Resurface the rotors(very fine grit sandpaper?Scotchbrite pad?), and rebed(?) the pads.
Brake rotors DO warp, I have turned them myself and seen more than .020 of thinkness variation (more than a .002 or so and you can feel it in the pedal).
But yes, pad imprinting can cause a vibe or pulse as well, most common cause is leaving the brake pads held against rotor after a hard stop.
In the case at hand I'd take a good look/feel of the axles, try slow figure eights with the wheels at full lock, listen for clicks and feel for ratcheting.
Gary
No matter how broke I am... I always seem to find two cents.
All_talk wrote:
Brake rotors DO warp, I have turned them myself and seen more than .020 of thinkness variation (more than a .002 or so and you can feel it in the pedal).Gary
It's uneven layers of pad material on the rotors that causes pulsing (slide-bite-slide-bite..etc.)
Resurface the rotors(very fine grit sandpaper?Scotchbrite pad?), and rebed(?) the pads.
they do warp. All you have to do is watch a rotor being turned on a brake lathe to see this. It is a more common thing in Mountainous states to get warping/and or "glazing", do to the constant braking on decents out on the highway. That article is written on a basis, but not on real automotive experience.
91 Legacy Sport Sedan 4eat
91crx si 165k
91 Civic RT4WD manual trans 168k
91crx Si 40.5k
85 BRAT Gl 140
97 SVX 74k
Ok....we need to clarify what warping and DTV are.
Warping would indicate that the brake rotor is not true based upon the centerline of the rotor. If this was the case, there is no amount of turning the rotor that will make it true again.
DTV or disc thickness variations means that the outer portions of the rotor are not true. When this occurs, you can turn them on a lathe or a mill, and get them true again.
Bheinen74 wrote:
That article is written on a basis, but not on real automotive experience.
Maybe everyone should read it again. Also all the other articles on there.
With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development programs in history - I have never seen a warped brake disc.
...In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
I'm sticking with their story. I guess a cheap rotor that's crooked out of the box would be another exception.
I have warped my share of fronts & it is definitely visible when they are on a brake lathe. The little tip of the lathe intermittently hits the disc until enough metal is gone to make it straight, then it hits constantly along the disc. Sort of like watching a warped record go around. Never seen someone warp a rear though. I guess it's time to get an Sti with those bigass Brembos. Or a Caddy CTS-V with even biggerass Brembos.
'94 Legacy Touring wagon. Quicksilver metallic. WRX rims, Whiteline ALK, SS brakelines, GR2s, alum. coolant tank. Gone, but not forgotten
'99 NSX, Alex Zanardi edition, #11/50. All stock & red 2 go
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
This is one of those automotive lore things that is just wrong. No matter how much you try to explain it to people or provide evidence, they won't believe it. Similar to detonation....but I won't get into that here...
You mean detonation vs. preignition? I know what you mean.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
sort of.....but even more so then that.....detonation is a pressure wave induced combustion/ignition of air & fuel. This doesn't happen. You're actually getting auto-ignition. All the gasses spontaneously ignite.
I just recently found that out at an engines class. It's one of those terminology things.
There's an NSX near me that I haven't seen move out of its spot in the driveway for about 6 years. I don't know if someone died and the parents won't part with it or what, but it's a shame. It's an early 3.0 model and I wonder if I could pick it up relatively cheap, but I wonder it to myself just in case they'd actually sell it cheap and then the sissy pragmatist in me would get his ass kicked.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
It can't hurt to ask, you may get a deal if they don't know what it's worth. Keep in mind if they do, used NSXs in good shape of that era are still $25K-$32K cars. You may want to get it checked out at mechanics direct (http://www.mechanicsdirect.com/) if it is for sale. Maintenance,especially if it is past due & neglected, is much more than any Subaru. This could also lower the price if it needs timing belt, water pump, clutch, hoses, etc.
'94 Legacy Touring wagon. Quicksilver metallic. WRX rims, Whiteline ALK, SS brakelines, GR2s, alum. coolant tank. Gone, but not forgotten
'99 NSX, Alex Zanardi edition, #11/50. All stock & red 2 go
. Only one day with a rain storm. 
--will try the factory ones.
