Brakes, couple of questions

[harrylime]

I have a couple of questions for you knowledgeable folk. I've had my front wheel off my 99 LS 400, to check the brakes. They work fine, except that I suspect the pedal travel may be excessive. I'm concerned it may fail the MOT on this , which is imminent. I found it difficult to check the thickness of the pads, but they were last changed, I believe in 2006, 22000 miles ago (now on 70,000 miles). The disc seemed in good condition, with very little scoring and not much of a lip. I measured the thickness of the disc at 28mm. 

At Lexus Parts direct a kit with discs and pads seems better value than pads alone, although obviously it will cost a fair bit more in labour. My first question is

How long to your front pads tend to last?. My second question is:

Would new pads, or new discs and pads be likely to reduce the level of brake travel, or is there likely to be a different cause elsewhere?

I had the brakes flushed and brake fluid replaced a few weeks ago to try and resolve this issue. Thanks in advance for any advice/experience  you can offer

 

[Howplum]

I would say it's difficult to answer your first question with any accuracy because the wear rate will depend on a number of factors, especially driving style.

When you inspected the discs were you able to check the inside as well? Also, it would be worth checking the rear discs and pads. It's possible than one or more piston might be seized in the caliper, especially in the rear calipers, which don't work as hard as the front ones.  I believe in theory new pads and discs should not affect the pedal travel, only the efficiency, assuming that the rest of the system is working correctly. After all, the system is 22 years old, so not all of the components may be working as the manufacturers intended.

[Malc]

definitely down to the driver ....  my Mrs is amazingly HEAVY on the brakes and I'm so light footed it's unbelievable

her Honda Legend brakes last half the time of mine on the Ls400 and I just know if she was the main user on my car they would only last about 15k miles ..  with me it's approaching 30/40k

it's a huge factor in the wearing out of your pads I'm sure ....  driving style

Malc

[Barry14UK]

also doesn't help if your road is punctuated with road humps along its length!

[Tinonline]

I thought I was a heavy braker but missus slams em on …. 
 

For what it’s worth: front discs can go to 90k but just worth doing before if your pads are ready or you’re getting shimmy or they’re plain thin.

Rears about same but will have less pad changes. Pads go for 30 to 40k miles and you’ll have the warning light on when they’ve gone beyond useful life. Pretty good until the end…

The pneumatics usually compensates for wear.

If you’re not happy you may want to get your master cylinder and servo checked out.

Or use the MOT as the diagnostics. That’ll give you very exact braking efficiency stats. And hopefully faults.

 

[BigBoomer]

Brake pad/disk wear is more down to how long you brake for, rather than how hard you hit initially the brakes.
I often shout at other road users that there are 3 positions for their right foot.
1- On Throttle pedal
2- On Brake pedal
3- On NEITHER!!
Use engine braking for smooth gentle braking. You will NOT add any appreciable wear to your engine. It is designed for it.
If you brake constantly whilst going downhill, you will eat brake pads like there is no tomorrow, and when you go to hit the brakes hard because that child ran out into the road, you may hit the child because you may have glazed your pads with your constant braking so your brakes will fail to perform as they should.

Hydraulic brake systems automatically compensate for the pad wear, so even totally worn out pads will have the same pedal bite point as new pads.
If you have a long pedal problem, and if the system has been bled fully and has no air in it, then the problem is in the master cylinder and I would recommend getting a new one fitted. 
The most common feeling with a master cylinder failure is that you get the initial bite but then the pedal keeps on moving if you keep up the pressure.
If the servo fails, then it will get much harder to brake as you won't have the vacuum-servo assistance, but that will not change the bite point either.

[ambermarine]

The brakes  components will deteriorate through time and all factors such as pad wear disc wear the age of the brake fluid the freedom of the pistons to move and added together can have a significant effect on the brakes.

I always change the pads out at 50% wear the fluid as been changed out at 30k and the brake are including pistons cleaned out with an air tool and brake cleaner. This will bring the system back to 100% accounting for tolerances within wear margins.

If these maintenance practices do not achieve the performance required then there is something amiss in the braking system.

 

[harrylime]

7 hours ago, BigBoomer said:

Brake pad/disk wear is more down to how long you brake for, rather than how hard you hit initially the brakes.
I often shout at other road users that there are 3 positions for their right foot.
1- On Throttle pedal
2- On Brake pedal
3- On NEITHER!!
Use engine braking for smooth gentle braking. You will NOT add any appreciable wear to your engine. It is designed for it.
If you brake constantly whilst going downhill, you will eat brake pads like there is no tomorrow, and when you go to hit the brakes hard because that child ran out into the road, you may hit the child because you may have glazed your pads with your constant braking so your brakes will fail to perform as they should.

Hydraulic brake systems automatically compensate for the pad wear, so even totally worn out pads will have the same pedal bite point as new pads.
If you have a long pedal problem, and if the system has been bled fully and has no air in it, then the problem is in the master cylinder and I would recommend getting a new one fitted. 
The most common feeling with a master cylinder failure is that you get the initial bite but then the pedal keeps on moving if you keep up the pressure.
If the servo fails, then it will get much harder to brake as you won't have the vacuum-servo assistance, but that will not change the bite point either.

Thanks George, that makes sense. I was hoping it isn't the master cylinder because just a set of  replacement seals costs more than a pair of front discs, even if I can get hold of them.

[Tinonline]

35 minutes ago, harrylime said:

Thanks George, that makes sense. I was hoping it isn't the master cylinder because just a set of  replacement seals costs more than a pair of front discs, even if I can get hold of them.

Feel for you…in worse case you can source a recon unit or new from one of the big global suppliers that source OE so it will be well priced even with tax and shipping, then get a friendly garage to fit.

I’d use mot as a diagnostic point.

You can go for non OE but it’s work ensuring it is still quality.

I faced similar dilemma with a £300 -£500 quotes for a wheel bearing. I wanted to buy OE bearing for 70 quid from Arayama or whatever they’re called but sourced an SKF quality kit (made in Japan) and got a known Lexus savvy garage to fit: complete price to fix £105. 
 

You are on 70k miles? I’d be surprised to see major failures generally…