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Help Pls: Steering wheel shaking/vibrating on braking at high speed

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Old 06-04-09, 01:43 PM   #16
richesmoua
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try checking your control arms. They can be warned out. I had a similar probelm with my sc400 when driving at high speeds the steering wheel will start to shake. I had the lower control arm on both side replaced with new bushings and now it drives just like a new car. I paid 800 bucks for the parts and installed it myself.
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Old 06-04-09, 02:36 PM   #17
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Originally Posted by stiles_s View Post
guys, seriously, try the procedure I outlined above -- it's free and might even raise your pulse a few ticks.

I've "warped" my rotors at least 3 times in the 40k miles on my GX, and cured them each time w/the procedure above.
YMMV.
That really wasn't a cure was it, if it reoccurred 2 more times within 40k miles?

Yes, there is some merrit to this technique, but only in cases of pad deposits and only if it is caught in the early stages. Otherwise, it will not only NOT work, but it is likely to worsen the problem.

Last edited by cssnms; 06-04-09 at 04:43 PM..
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Old 06-04-09, 02:43 PM   #18
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Originally Posted by richesmoua View Post
They can be warned out. .
Do you mean "worn out?"

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Originally Posted by richesmoua View Post
try checking your control arms. I had a similar probelm with my sc400 when driving at high speeds the steering wheel will start to shake. I had the lower control arm on both side replaced with new bushings and now it drives just like a new car. I paid 800 bucks for the parts and installed it myself.
Unlikely this is the cause since the poster stated "I had a vibration in the steering wheel when braking at high speeds.." All indicators point to the rotors.

And for anyone who is suffering from run-out, DON'T waste your money having your rotors resurfaced unless you like putting good money after bad. In most cases, it only serves as a short-lived fix.
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Old 06-14-09, 10:52 PM   #19
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Originally Posted by cssnms View Post
That really wasn't a cure was it, if it reoccurred 2 more times within 40k miles?

Yes, there is some merrit to this technique, but only in cases of pad deposits and only if it is caught in the early stages. Otherwise, it will not only NOT work, but it is likely to worsen the problem.
Well, I'd call it a cure for me. i'd much rather "fix" it myself than have to take few hours out of my day, and spend $$, to have the dealer "fix" it. Based on all the comments on the board, I think the pads on our trucks are pretty soft, and tend to transfer material to the rotor when hot (especially if you've stopped "hard" and keep on teh brakes @ a light).

Net: my method is working great for me. When I end up replacing the pads+rotors, I'll probably go with a harder/semi-metallic pad to lessen the issue.
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Old 06-14-09, 11:26 PM   #20
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Lexus SUVs seem to be a little 'under braked' - my RX repeatedly had this problem before a TSB with new brake pad part numbers seemed to fix the problem - it re occurred every 9,000 miles like clockwork until they came out with different pads. It cost $300 to turn the rotors and new pads on the front axle.

Seems like people are having similar trouble with their GXs, though it hasn't been a problem with mine so far.

I finally bought an infra red thermometer so I could measure the disc temps for all of my cars, and see if the Lexus' really are hotter - my Dodge PU gets much hotter, but the discs are massive when compared to the RX or GX, so I concluded it's a combination of temp, and disc construction.

Another thing is to get a dial indicator and check the run out on the discs yourself - it's not very expensive, and you can check your own discs for warpage if you are able to R & R a wheel. More than .002" run out (I will double check this number to make sure I'm remembering it right) and the disc needs to be resurfaced or replaced. Many people believe there is little value in resurfacing them - the problem is they are not thick enough to begin with (to handle the high temps), and resurfacing them only makes them thinner.

I'd try a Toyota or independent shop, and consider going with aftermarket parts to avoid the high charges the Lexus dealers get. Changing rotors and pads yourself is not a hard job, if you have the time, some tools, and the mechanical ability.

Frustrating - for a premium car, I would expect lots of design margin in the brakes, instead of skimping - my Dodge hauls very heavy loads and the brakes get much hotter, and no trouble at all with discs warping (rant over....)
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Old 06-15-09, 07:44 AM   #21
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- the problem is they are not thick enough to begin with (to handle the high temps), and resurfacing them only makes them thinner.
Bingo However I would add that in the case of the GX it has less to do with the thickness then it does with the diameter.

The rotors and pads are undersized for the weight of the GX coupled with the fact that it is my belief that the quality of the steel is sub par which greatly diminishes their ability to effectively absorb and dissipate heat. The rotor's job is to absorb and efficiently dissipate the heat that is created under braking. Anytime a rotor is turned it loses mass and the loss of mass adversely affects the thermal dynamics of the brake system.

BTW, Toyota has been plagued with similar issues with the Tundra and 4-runner.

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Old 06-15-09, 10:47 AM   #22
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I am wondering if we would drill the rotors, would they be more effective ?
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Old 06-15-09, 12:43 PM   #23
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I am wondering if we would drill the rotors, would they be more effective ?
That's about the worst thing anyone can do to a rotor. The problem therein lies that when you drill holes it compromises the integrity of the rotor and can lead to cracking around the hole - ask some of the IS-F owners about that! The benefits of drilled rotors are a thing of the past. Today's performance track cars use slotted rotors for improved heat disipation.
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Old 06-16-09, 02:32 AM   #24
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CS - ain't IS'F factory OEM installed with Brembo Calipers. the rotors are massive - 14.2 inches, crossed drilled. I remember seeing one at SEWELL display.
Currently I am just making a template for my LS for the cross drill design, should be up soon.
Yes I have heard stories about this drill stuff being done, but this is not where one you just goto a lathe and have the drill done. A lot more goes into doing this and you have to have a second forging done immediately after the drill, and this not done direct heat treatment, but via oil forging, where the oil is bought to a flash point and then the rotors are dipped for a period of not more than 7-8 minutes.
Remember this GX470 rotors are GCI - Grey cast iron and not steel. The quality and heat treatment of the steel probably has a lot to do with how well a given set of drilled rotors will hold up. GCI is incredibly resistant to heating and cooling cycling. Thats why it makes a good rotor material. (Its also the cheapest material to cast to Near Net shape, easy to machine, absorbs vibration, and holds dimension well when under differential heating)
All you have to ensure the holes are chamfered or radiused at the edges. Also x-drilling reduces the amount of surface area for the pad to act upon while also providing less material to hold heat.
There are various treatments and I think cryogenically treated rotors are somewhat the best that make a difference as that process does something to the molecules to make them more even and strong, without being brittle. I'm not a metallurgist but have had some experience with forging steel. I have had a friend who has a Yukon for the last two year had cross drills done, with many extended heavy braking sessions, and they have yet to crack.
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Old 06-16-09, 06:54 AM   #25
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Oh where to begin...

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Originally Posted by mann777 View Post
CS - ain't IS'F factory OEM installed with Brembo Calipers. the rotors are massive - 14.2 inches, crossed drilled. I remember seeing one at SEWELL display.
True, the ISF does sport brembo cross drilled rotors and calipers. However, that means nothing as it relates to demonstrating the benefits or lack there of as the case maybe of cross drilled rotors.

Take a read, start half way down the page w/Lance's (Lobuxracer) schematic...

http://www.clublexus.com/forums/is-f...-on-isf-7.html

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Currently I am just making a template for my LS for the cross drill design, should be up soon.
Yes I have heard stories about this drill stuff being done, but this is not where one you just goto a lathe and have the drill done. A lot more goes into doing this and you have to have a second forging done immediately after the drill, and this not done direct heat treatment, but via oil forging, where the oil is bought to a flash point and then the rotors are dipped for a period of not more than 7-8 minutes.
First let me ask you; what are you trying to accomplish by punching holes in your rotors? It might look cool, but that will be the only purpose it will serve.

Here's some more light reading for you. Written by James Walker Jr one of the leading engineers on brake systems. This is a summary article, his book goes into greater detail.

http://www.scirocco.org/faq/brakes/p...n/pfpage1.html

Here is his sidebar quote on cross drilling...

Those Poor Rotors
Let's look ot some common rotor "modification" and "performance" upgrades that you may have been exposed to. We'll try to separate the marketing from the engineering: Bigger rotors will make your friends think you are cool, bigger rotors look sexy, but bigger rotors do not stop the car. What a bigger rotor will do is lower the overall operating temperature of the brakes--which is a GREAT idea IF your temperatures are causing problems with other ports of the braking system.

Take, for exomple, a Formula 500 racer, a small 800-pound, single-seat formula car. While the brakes are certainly much smaller than those found on a 3000-pound GT1 Camaro, that does not necessarily mean that they need to be made larger. In fact, installing o GT1 brake package onto our formula car would probably do more harm than good. That's a lot of steel hanging on the wheel that needs to accelerate each time the gas pedal is pushed. So the motto of this story is bigger is better until your temperatures are under control. After that point, you are doing more harm than good, unless you really like the look. (And hey, some of us do.)

Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.

The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life, at the expense of higher weight. It's all about tradeoffs.


Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)



Quote:
Originally Posted by mann777 View Post
Remember this GX470 rotors are GCI - Grey cast iron and not steel. The quality and heat treatment of the steel probably has a lot to do with how well a given set of drilled rotors will hold up. GCI is incredibly resistant to heating and cooling cycling. Thats why it makes a good rotor material. (Its also the cheapest material to cast to Near Net shape, easy to machine, absorbs vibration, and holds dimension well when under differential heating)
All you have to ensure the holes are chamfered or radiused at the edges. Also x-drilling reduces the amount of surface area for the pad to act upon while also providing less material to hold heat.
Okay you got me there yes, the GX rotors are "cast iron." Now back to the matter at hand....

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Originally Posted by mann777 View Post
x-drilling reduces the amount of surface area for the pad to act upon while also providing less material to hold heat.
You are right about that... cross drilling rotors does reduce the contact area, which is NOT a good thing. It also reduces the mass of the rotor. If you reduce the mass of the rotor you adversely impact the thermal dynamics of the brake system. In other words, the thermal capacity of the rotor is reduced and as such it CANNOT absorb as much heat, which means your brake system cannot as efficiently dissipate the heat, which is why they CRACK, it can also lead to brake fade.

Show me an F1 car that is in use today that uses cross drilled rotors.

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Originally Posted by mann777 View Post
There are various treatments and I think cryogenically treated rotors are somewhat the best that make a difference as that process does something to the molecules to make them more even and strong, without being brittle. .
Conceptually the technology sounds good, but I have yet to see any "independent" testing that proves all of the claims. However, I have some real world results... I have rear cryo treated slotted rotors (PowerSlots) on my GX and they developed run-out within 3 weeks of install. This only means that the cryo rotors were no better at dissipating heat and I would argue they were less effective. Quality of the metal? Maybe. Certainly the cryo treatment was of no benefit here.

Quote:
Originally Posted by mann777 View Post
I'm not a metallurgist but have had some experience with forging steel. I have had a friend who has a Yukon for the last two year had cross drills done, with many extended heavy braking sessions, and they have yet to crack.
Unless your friend is routinely tracking his Yukon, which I doubt or his truck is constantly under a heavy towing load performing high speed stops I am not sure this demonstrates anything. The point being, punching holes in rotors will not only reduce the life of the rotor, but it will not improve the performance and to the contrary it can negatively impact performance. Stick with blanks or slotted.

If you really want to improve braking performance, start by installing some stainless steel brake lines and using a good synthetic brake fluid.

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Old 05-06-14, 04:45 AM   #26
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Believe it or not...I had a vibration in the steering wheel when braking at high speeds, and it turned out to be the rear rotors and pads needed replacement. The front set was fine!
Hi,

Is it possible to explain why/how this happens? Mine is an RX but have similar steering vibration at high speed when braking. Replaced front brake pad and disc already. Mine is an AWD. Rear discs are a bit old.
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Old 05-06-14, 07:15 AM   #27
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Hi,

Is it possible to explain why/how this happens? Mine is an RX but have similar steering vibration at high speed when braking. Replaced front brake pad and disc already. Mine is an AWD. Rear discs are a bit old.
Google rotor runout. Deposits left behind from the brake pads on the rotor can cause steering wheel shakes. Get a micrometer and measure your rear rotors at several different spots.
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Old 08-14-14, 07:11 AM   #28
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Just need to get away from OEM Rotors and pads...had this problem with my 07 4runner and on my 09 GX ...they use the same exact rotor and pads...went with EBC ultramax slotted rotors and Hawk LTS pads all the way around...smooth as silk at all speeds after proper bed-in and wheel torque.
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Old 08-14-14, 08:50 AM   #29
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good choice on the Hawk pads, I've run the EBC greenstuff pads and they were too spongy feeling and wore quick!
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Old 08-14-14, 09:04 AM   #30
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yeah...thanks...run them on my F-150 and they are awesome.
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Old 08-14-14, 09:04 AM
 
 
 
 
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