Vibration When Braking at High Speeds

Post by **rob1** » Fri Mar 17, 2006 4:10 pm

I have a 94Q with 129K. I have noticed vibration in the steering wheel and brake pedal when braking at freeway speeds, but not speeds lower than about 45 mph. Brake pads are relatively new but when the rotors were turned for the 3rd time, the shop stated this would be the last time they could turn the rotors. Any ideas?

Post by **irax** » Fri Mar 17, 2006 5:04 pm

sounds like the rotors are warped or too thin to be useable with out NEW pads...

Post by **jimmys G50** » Fri Mar 17, 2006 5:23 pm

not likely anything but the rotors.

Post by **maxnix** » Fri Mar 17, 2006 5:39 pm

rob1 wrote: Any ideas?

There are extensive threads on brakes. Try a search.

Post by **Jesda** » Fri Mar 17, 2006 6:41 pm

Dont get cheap ebay rotors. They'll work, but they'll warp much faster, making their low cost not very low in the real world.

Post by **jimmys G50** » Fri Mar 17, 2006 8:53 pm

i went to a local autozone and got rear rotors. they work just fine.

Post by **3Q Jay** » Fri Mar 17, 2006 9:00 pm

Hi Rob-I'll vote for rotors, too. did i mention that mine also does this when braking down from 85 and up?

I'm about due for brakes (2mm, and waiting for the indicator). As I mentioned, i'm doing the Y32 rear brake upgrade. If it helps, you can have my oem rotors (rear rotors replaced 45k ago and turned once). I have no record of the front rotors ever being replaced, last service on rear brakes (23k ago), fronts were reported at 70% pad, but rotors at service limit.

i have new brembo blanks for front ready to go on as well.....

Jay

Post by **DrewQ45** » Fri Mar 17, 2006 11:00 pm

irax wrote:sounds like the rotors are warped or too thin to be useable with out NEW pads...

I concur.. must be the rotors.

Post by **RAQ45t** » Sat Mar 18, 2006 2:08 am

According to the complete service records on my car,the OEM rotors warped constantly,and needed to be turned often.Try an outside brand for replacement,as turning the OEM ones hasn't seemed to help much.My own vibration is back again after less than 5K.I'd say they're just too damn soft to begin with.

Post by **Q45tech** » Sat Mar 18, 2006 3:42 am

Perfectly true high quality rotors will QUICKLY take a magnified warp from bolting them on to warped hubs [oem spec for hub is 0.0001"].

You must grind, sand, shim the hub to be perfect, otherwise the rotor just warps again.............why dealers use on the car lathe to mistrue the rotor to counter the hub error.

Post by **szh** » Sat Mar 18, 2006 4:54 am

Probably the rotors are done, like everyone else mentioned.

But, I would also recommend balancing your wheels/tires and see if that makes a difference! You may be surprised!

Z

Post by **Jeff Williams** » Sat Mar 18, 2006 6:08 am

Q45tech wrote:Perfectly true high quality rotors will QUICKLY take a magnified warp from bolting them on to warped hubs [oem spec for hub is 0.0001"].

You must grind, sand, shim the hub to be perfect, otherwise the rotor just warps again.............why dealers use on the car lathe to mistrue the rotor to counter the hub error.

Car Lathe = $140.00 at the dealership. I agree, if the hub is warped, then the rotors have no chance. BUT, if the hub was warped, perfectly turned rotors would vibrate instantly, not eventually.

Here is my advice:

Buy the cheapest drilled and slotted rotors on eBay. My $50 set NEVER warped. I put close to 75,000 miles on them. I also bought cheap pads at the local parts place, so they would not eat into the rotors. Metal or ceramic pads just kill rotors.

The slots and holes help dissipate heat and reduce the chance of rotor warpage.

SS lines and DOT4 fluid will make the car stop quicker, and more often, better. The brake pedal feel is much more sensitive, but WAY better than the soft pedal with old fluid and lines. It is a $150 investment, if you buy the speed bleeders with the fluid and lines. check out http://www.raceshopper.com

Post by **Jesda** » Sat Mar 18, 2006 6:17 am

Jeff Williams wrote:Here is my advice:

Buy the cheapest drilled and slotted rotors on eBay. My $50 set NEVER warped. I put close to 75,000 miles on them. I also bought cheap pads at the local parts place, so they would not eat into the rotors. Metal or ceramic pads just kill rotors.

If its good enough for Jeff, its good enough for me. I might try that myself.

Also, Duralast rotors with 2-year warranties can be had for $35 at Autozone.
Modified by Jesda at 10:29 AM 3/18/2006

Post by **qship96** » Sat Mar 18, 2006 6:27 am

any input on the cryogenic frozen rotors from tire rack listed for the 90-96q? does this process indeed stop/slow warping?

Post by **szh** » Sat Mar 18, 2006 8:31 am

I got irotors.com (from http://www.irotors.com) for my 1995 Q45 and they worked well. They offer cross-drilled, and slotted versions too (or combinations) and they may be other options.

Personally, I liked the cross-drilled and slotted ones that I got, but if you do not like the cross-drilling or slotting, you can do without either or both.

The blanks were Bradi (sister of Brembo) and worked well for the time I had the car (till I sold it some miles - more than 1500, as I recall - later) without any problems. Stopped well too!

Z

Post by **Q45tech** » Sat Mar 18, 2006 8:48 am

When the average owner feels vibrations THEY ARE REALLY WARPED compared to someone like me [looking for a reason to true rotors or rebalance tires............the slightest quiver is enough for me to start the process.

Everyone's sensitivity is different. I varies tremendously between drivers to the point where they don't know what you are talking about when you come back from a test drive.

I've tried: 2-oems, Brembos, Bradi, KVR, Chung Cho, 2-PowerStops..........by far the best have been PowerStops........just getting ready for my 8th set all around as much as I hate to spend they will be Power Stop drilled.

As to immediately feeling vibration with a warped hub and a newly cut rotor, it seems to take a few heat cycles for the rotor to react conform.

The only way to know for sure is to measure the runout when you install the rotor.

Post by **maxnix** » Sat Mar 18, 2006 9:20 am

Q45tech wrote:As to immediately feeling vibration with a warped hub and a newly cut rotor, it seems to take a few heat cycles for the rotor to react conform.

The only way to know for sure is to measure the runout when you install the rotor.

Absolutely true when all surfaces are new and unblemished and flat. It will take a little while for vibration to set it from uneven wear and brake material deposits to set in. Measure the hub and the rotor runout before installing if you want to be sure. Index the rotor to the hub if you are maniacal.

Haven't tried the others, but the drilled Stillen Brembos on the front have worked very well for me for 20K. Get them from Joe. Any rotor brake pad must be broken in correctly. And change to DOT4 when you do the new brake system.
Modified by maxnix at 11:40 PM 3/18/2006

Post by **rob1** » Sat Mar 18, 2006 4:50 pm

Jay, thanks for the offering. Since the problem was evident, I went ahead and bought a couple of made in the USA rotors from Autozone today and found a local guy to install them for $50. A short drive indicates that vibration problem seems resolved, but I know for sure in a few days.

Thanks to everyone for the input in resolving this problem.

Post by **Q45tech** » Sun Mar 19, 2006 1:56 am

You mean the box label or stickers or the original iron [from the ground] before the scraping and shipping overseas was made in USA.

Actually some exploding star made the iron.

http://www.autofieldguide.com/articles/109805.htmlA pictorial view of how rotors are made.

Vibration When Braking at High Speeds

Vibration When Braking at High Speeds

Re: Vibration When Braking at High Speeds (rob1)

Re: Vibration When Braking at High Speeds (rob1)

Re: Vibration When Braking at High Speeds (rob1)

Re: Vibration When Braking at High Speeds (irax)

Re: Vibration When Braking at High Speeds (rob1)

Re: Vibration When Braking at High Speeds (RAQ45t)

Re: Vibration When Braking at High Speeds (Q45tech)

Re: Vibration When Braking at High Speeds (Jeff Williams)

Re: (szhosain)

Re: (Q45tech)

Re: Vibration When Braking at High Speeds (GQ Jay)

Re: Vibration When Braking at High Speeds (rob1)

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