Gs300 Mk 1 Brakes, Arghhh !

[andyb63]

.... well it seems, having read a number of posts, that my annoyance at having to put another set of discs on the front of the my 300 sport that it is a common problem. Cant understand how a car can wreck discs so quickly, there not exactly small are they Has anyone upgraded and solved the problem ? if so what have you used?

[jdmparts_guru]

Next time also try to change to a different brake pad manufacturer, certain combinations are less likely to warp...

[Dave-Ellen]

I can offer PAGID 16 groove fronts,Prolex_uk 8 groove fronts & DBA slotted & drilled fronts

All at prices lower than a snakes whatsits

[Scorpion]

What pads are they compatible with Dave.

[Mike246]

Just had my fourth set fitted in 77,000 mile Mk2. This is not good.

Had the garage give me the old ones back so I could get them checked for run-out. Whoever said that the problem is caused by pad material adhesion is talking rubbish. The disks have only worn 2mm from new and are warped.

Lexus have a heat and material problem with this design, not helped by the tendency to use the footbrake at lights, rather than the parking brake as the latter is foot-operated.

[ColinBarber]

It's not a material problem because people have the same problem with different makes of discs and pads.

I would say the cause of most peoples warped discs are due to the wheel nuts being overtightened. You need to tighten them up in the correct order and to the correct torque.

The other main problem is a sticking caliper/corroded sliding pins.

Warping the standard discs under normal road driving should be almost impossible.

[Mike246]

Colin,

Your advice appreciated but how can over-tightened wheels cause disk warp?

The five studs go through the 'hub' of the disk and any uneven pressure caused by over-tightening cannot impact on the disk itself.

Having said that, I'm going to get Lexus Hatfield to recheck the torques.

[ColinBarber]

Do a search on the web for wheel torque brake disc warp. You will find loads of people with the same problem on Fords, VWs, Dodge, Toyota, Honda, Saab, Subaru, BMW, Mini etc. all with disc warp problems and all with advise to torque the wheels correctly.

The back of the wheel directly tighens against the brake disc so it has a direct impact on the disc.

All people that make sure their wheels nuts are tightened correctly never seem to have problems with warped discs.

If you ever let somebody else change a wheel then at the first possible opportunity undo the nuts and tighten correctly.

If you don't believe me then here are some quotes for web sites:

The No. 1 cause of brake pedal pulsation is uneven lug nut torque. The usual reason is t hat some mechanic overtightened the wheel lug nuts with an impact wrench, distorting the brake disc.

Ever hit your brakes and the steering wheel starts to shake? This is the result of warped front rotors. The cause of the warp is having different torques on the wheel nuts. The rotor is a disc, which gets very hot when the brakes are applied. When the disc cools and you have inconsistent tension on the lug points around the disc, it will bend or warp. That's why you should always use a torque wrench -- if you make sure the wheel nuts are at the same torque, you'll avoid the shakes.

If there's anything that makes my teeth grind, it's watching a mechanic with an air wrench tightening lugs until they squeak and blow powder. This practice not only makes it difficult for the driver to remove them later (probably at the roadside in the rain and mud), but it overstresses the fasteners and could make them snap off, which has potentially disastrous consequences. It's also likely to warp the brake discs, leading to pedal pulsation, reduced brake life and increased stopping distances.

Brake discs can be warped by overheating the disc, a heavy impact, or incorrect torque on the wheel nuts. If pulsations are a problem, re-torque the wheel nuts (with a torque wrench!) first. This may correct brake pulsations in many vehicles without having to do any other work.

What causes a rotor to warp? Overtorquing or unevenly torquing the lug nuts with an impact wrench is a common cause. For this reason, most experts recommend using a torque wrench to tighten lug nuts when changing a wheel. There are also special torque-limiting extension sockets called "Torque Sticks" that can be safely used with an impact wrench to accurately tighten lug nuts. But a plain impact wrench should never be used for the final tightening of the lug nuts because most provide no control whatsoever over the amount of torque applied to the nuts.

They also can warp as a result of not following a proper tightening sequence of the lug nuts when installing the wheels. Another is improper torque or tightening of the lug nuts.

Once the rotor heats up during operation, if one lug is a little less tight that the others, the rotor will expand at that point and cause run-out

Too much torque can also warp the brake rottors.

Lug Nut Torque

Over-torque of wheel lug nuts is one of the prime causes of brake rotor distortion. This can lead to permanent warping of the rotors, uneven wear of the rotors and pads and lots of brake chatter (NVH).

With today's very stiff alloy wheels, like from BBS, SSR, Volk, etc., when you torque down the lug nuts the wheel-mounting surface will force what ever it contacts to take its shape. Which means whatever that surface looks like will be what the rotor looks like.

Get a torque wrench and check the torques on every lug nut and make sure they are within the specs (which you should be able to find in your owner's manual). And make sure that every lug nut is torqued down exactly the same. Even if all 5 on a wheel are within specs, not having all 5 be equal will introduce distortion.

And if you think that your light alloy wheel can't possibly be that stiff, you wrong they are MUCH stiffer than the brake rotor or even the hub.

Besides not being able to remove the wheel, over-tightening (torqueing) a lug nut is sure to warp the brake rotor

[andyb63]

Thanks Colin, I certainly have never considered incorrectly tightened wheel nuts to be a cause, though I guess logically it makes sense. However having had various cars, including TVR's and Lotus, and never using a torque wrench I have never exeprienced anything like what the lexus does to the brakes and I have hammered some rotors in the past. It seems such a common problem that i wonder if its some design issue.

I am wondering if it is a problem related ot the larger 'sport' alloys or does this probelm affect the smaller wheeled cars also, as the 245,40,18 rubber is a pretty hefty size for a front.

I'll certainly make sure the wheels are torqued properly next time ( actually had a nut missing last time ! ) and that I bed the brakes in.

[Dave-Ellen]

What pads are they compatible with Dave.

Thats a debate that can go on and on !

for the prolex brnded discs I'd say mintex pads as thats who makes the discs for me,,,,,same for the pagid's.

for DBA i've got EBC greenstuff pads and am well happy

[andyb63]

Bringing this back up.

Have now got my hands on some new discs as the problem no dount contributed to the need for 2 lower ball joint s and a top suspension arm and ball joint to pass the MOT. OUCH !! So I need the following:

1) Instruction on front disc changing for gs300 Mk 1

2) Torque settings for wheel nuts

3) and the clincher........ I need a wheel nut !

[ColinBarber]

103Nm (76 ft-lb) for wheel nut

[Tron20]

103Nm (76 ft-lb) for wheel nut

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Just got my lexus back from a lexus dealer, and they replaced the rear passenger side tyre, and put the wheel back on and it certainly felt like more than 76 ft-lbs of torque on those nuts, i had to get my 30" torque wrench out to undo them the wrench in the boot and my strength couldn't undo them. Do lexus even bother using torque wrenches, might ask to see them put my alloy back on when they find out why my new tyre is going flat