Big Torque Difference Between Front And Rear Caliper Installation Bolt

[Jim Johnson]

I'm replacing the front brake rotors/pads on my 2000 RX3000. The manual shows that the front caliper installation bolts require 87 ft-lbs torque and the rear ones only need 25 ft-lbs. Can I trust the numbers? If yes, does anybody know why the big difference?

Cheers,

Jim

[lenore]

Caliper mounting bolts front 25, rear upper bolt 20 rear lower 14

Caliper bracket mounting bolts front 77 rear 34 (this is the bracket that the caliper actually mounts to)

[lemon]

Front bolts are 25 ft/lb, rear are 32 ft/lb. These are the bolts that go through the caliper holding it to the caliper mounting bracket. The 87 you're talking about must be for the bracket that the caliper bolts to, although my diagram shows 77.

Have a look at these -

front_brake_component.pdf

rear_brake_component.pdf

If you're replacing the rotors, you'll have to remove the caliper mounting brackets (called Front Disc Brake Cylinder Mounting in the diagrams) as well as the caliper. Don't confuse the torque settings for the different bolts. I did this once, and snapped the head off of the caliper bolt.

Good Luck.

[PK_3]

Jim,

I can't open the pdf's, and lenores numbers sound good is close emough plus some. If you need to justify the difference in your head. Overall your front brakes take far more stress and strain than the back. Thats why they have bigger calipers, rotors etc.

Regards, PK

[mikey00]

Jim's first post was about a 2000 RX. His specs agree with the specs I have in a 1999/2000 manual. It's been a while since I have done my 01 brakes but I seem to remember that the front caliper bolts hold the caliper on directly but the rear ones are part of the sliding pin system. This would account for the front to rear torque difference. I could be wrong here, You need to check when you have it apart. Just be careful and make sure you know the difference between caliper bolts and support plate bolts.

Lenore, I am not sure where you got your specs from but they seem to agree with my 2003 manual. There was a design change in 2003 and I am not sure if these specs apply to 2000. I think this was the first year that the front caliper mounting bolt became part of the sliding pin system so the torque was lowered. And the front bracket was no longer part of the sliding pin system so its torque was raised.

The PDFs Lemon posted are from a 2004 RX330 which had another brake design change with different specs.

[lenore]

MY specs are from a Haynes manual for Lexus RX300 covers all years...Close enough, nothing to worry about.....

[lemon]

Jim's first post was about a 2000 RX. His specs agree with the specs I have in a 1999/2000 manual.

Ooops. My mistake and my apologies. I really think there should be a separate forum for the 300. The 330 and up to 2009 350 have more in common. The 2010 onwards 350 should be separate. Just a thought.

[beachlover]

So what will happen if I tighten these caliper bolts to say 85 ft/lb? Can't imagine that extra tight is a problem since mechanically they don't do anything except hold the caliper in place....

[mikey00]

So what will happen if I tighten these caliper bolts to say 85 ft/lb? Can't imagine that extra tight is a problem since mechanically they don't do anything except hold the caliper in place....

It looks like in lemon's post above he snapped the head off the caliper bolt. They are 2 different bolts with 2 different purposes. One is long and thin and is part of the sliding pin system. Other is short and just holds caliper or caliper mounting plate (depending on which year) firmly in place.