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Hub Centering Screws.


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Recently suggested that Lexus service somewhere in the past had replaced the rear disk/drums and centering machine screws. The heads on the screws were too small so the disc assembly had rotated semi-shearing the centering screws.

I went to Lexus to get the parts fully expecting to find the correct ones would locate snugly into the holes in the assy.

They were exactly the same as the ones I had removed.

Lexus parts countered straight out that I must have pattern disc/drums.

I said show us an original as I have a complete service history stamped by Lexus up the time I bought the car. The disc was changed by you if at all.

Sure enough the screw was floating around in its location with approx. 2 mm to spare O/A

The spares boss was not impressed as he had had experience of Vauxhall spares before working with Lexus and was sure that there should never be any float at all.

He suggested that I wrote to Lexus outlining a design fault.

While it may not be very dangerous if all the studs are sound and the disc is positioned carefully but the disc on mine had rotated the 2mm and was jammed onto the bent and sheared postioning screws.

I strongly advise you to take a look at yours ASAP just to reassure yourselves.

Perhaps you could reply on here so that I get some support if I do take the time to complain to Lexus.

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Hi,

As far as I know the UCF20 LS400s (both the 1995 - 1997 Mark 3 and the 1998 - 2000 Mark 4) share the same front and rear brakes. That is 315mm discs with 4 piston calipers at the front and 305mm discs and single piston calipers at the back.

Which part numbers do you have for the disc and retaining screw ?

In the summer I replaced both front and rear pads and discs on my mark 4 LS and I bought all the parts from Lexus. The front discs were part number 43512-50152 and the rear discs were part number 42431-40080. I also purchased 8 new retaining screws (2 per disc), and the part number for both the front and rear disc retaining screws is 90155-60002. The screws were supplied in a small bag and had the above part number labeled on the packet.

The old screws that came off were exactly the same as the new ones. The screws had a good size flange with plenty of surface area to keep the disc mated to the hub and they fitted very nicely in the recess with out any problems. The flange (screw head) was bigger than the hole and there is no way I could see that with the parts I fitted that I could encounter the problem you have mentioned above.

I stand corrected but I am pretty sure that the Mark 3 cars have the same discs and hence the part numbers should be the same.

The retaining screws are made of quite a soft metal and it is very easy to round off the head while taking them off since they are often siezed on and hence somebody just used non-OEM replacements. (this is why i purchased new ones to make future removal of the disc easier).

Although your car has full Lexus service history, it is quite possible that the previous owners got all the servicing done from Lexus, apart from the discs and pads (since this is a very costly job from the main dealer). Do you have the receipts from the previous owner for the brake job to support that this was done by Lexus ? Without this its difficult to prove it was done by Lexus.

I might have the old retaining screws i took off laying around somewhere in my garage and I will post a photo of them if i can find them.

What are your thoughts ?

Thanks :)

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Well the screws were offered up to a brand new disk in the Lexus store at the time hence our surprise. I checked the parts screen on the computer to ensure that I had got the right ones. The screen was related to my registration which is logged to Lexus database.

Screws were

L90155-60002 @ 0.93 the pair.

The thread is naturally smaller than the hole to avoid an interference fit.

On other cars I have had, the head of the screw fits exactly into the recess on the disc/drum to locate it. These supplied screws allow a 2mm movement and do not act as locators but simply hold the drum in whatever position until the wheel is bolted on. This is not an exact machined solution but allows for the drum to be out of centre.

I have not driven fast enough to see whether there is any vibration. I hope I located the drum well enough, but as I say its approximate rather than a certainty.

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Hmm, thats a little odd.

Often you don't need to rely on the screws to centre the disc to the hub. When the new disc is placed on the hub, before mounting the screws I put the wheel nuts on to the studs and thightend them gently to the disc so that the tapered ends of the wheel nuts centre the disc, and then i put the screws on and tighened them. Its the studs which provide the 'true' centre of rotation. After that provided the wheel nuts are evenly torqued on when the wheel it put back on it should be more than enough to keep the disc centred.

I've not experienced even a tiny bit of vibration. Just silky smooth and quiet braking even from motorway speeds.

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The GS and IS do not have any retaining screws on the disk so I would imagine that the screw is only there to hold the disk in place when the wheel is off. If the wheel is on and torque'd correctly, they actually serve no purpose and are not something to worry about from a safety perspective.

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