Bought a 2010 Prius at 55,000 mi. Brake pads were at 6mm front and 5mm rear. Car is now at 98,000 mi. Recent dealer maintenance showed brake pads at 3mm front and 4mm rear. Dealer service was pushing me to replace them, but considering I keep driving the same way, could I put off replacing them for another 20,000 mi., when front should be at about 1.5mm and rear 3.5mm?
With some cars, brake pad thickness of 3 mm won’t last until the next service (5,000 miles) so replacement is recommended.
Prius brakes wear slowly, you should be fine for a while, the brake pads might still measure 3 mm at the next two service visits.
Brake pads usually have a groove in them. When the pads get thin enough that this groove starts to disappear it’s time to replace. It sounds to me like you’re trying to get every last mile out of these pads. If the pads go to metal then you’ll be costing yourself more money replacing the rotors too.
That would be a very good example of false economy.
As glasspilot stated…
How many miles until your next service? Maybe the dealer is telling you that the pads won’t last until the next service.Usually,the rotors will be replaced at the same time adding extra cost to you. I would consider finding a good independant mechanic for this job because dealers are usually more expensive.
I’ve seen minimum brake pad thicknesses from 1 to 4 mm. FWIW, the minimum legal pad thickness in the UK is 1.5 mm. You lost 3 mm in 33,000 miles on the front brake pads. At this rate, you could go another 5500 miles before the wear indicator starts squealing, and 11,000 miles before dropping to 2 mm. This assumes that the brake thickness was measured at its low point and not the average wear. If you don’t need the car as much just now, it’s a good time to replace them. You could go a little longer, but not much.
If your pads have a wear indicator, or if you will also be replacing the rotors when you do the pads, then I would not worry about replacing the pads now.
I see some assumptions the wear rate is linear, is it?
Not from the limited experience I have witnessed but I have no scientific basis for it (just to head off the inevitable). My thoughts are as the pad gets thinner, it’s ability to absorb and transmit heat is diminished, resulting in faster wear. For people I know that try to eeek out every last bit of life, they seem to go from OK to gone really fast. And then, you’re potentially damaging the rotors as well. I change pads earlier rather than later and do far less rotor changes than most. Changing only pads is very easy, especially if the rotors are wearing evenly…
My thought is with thinner pad the heat conductive path is shorter from pad surface to backing plate, improving heat transfer.
However, the pad material that’s left gets older and older, and the binding material gets weakened by the heat over time.
And so the pad wears away faster because it’s old and “baked”.
A experiment would be to shave down a new set of pads to ~5mm and see how quickly they wear.
The OP should check the owners manual and see if there are pad wear indicators on the Prius. If there are, I’d trust them to tell me when to replace the pads.
I worded it poorly. Replace absorb with withstand. The path is shorter but the material has changed so it’s not equal to when it was new.
It might be interesting but it may not reflect real world exposure. As you noted, time and heat alter the material. All the while it is in service, it doing work and degrading, but if you purposely shave it down, you have virgin material to start with. Periodic inspection and recording thickness should reveal if it is linear but I don’t have the willpower to do that. I’m betting the manufacturer knows…
That’s often the nature of research.
That’s the point of the experiment: separate the effects of pad age vs thickness.
Unfortunately, it will not be definitive as there are multiple variables to consider. The risk is using the results as definitive conclusion. Multiple experiments would be needed and probably end up taking longer and with more uncertainty than just measuring pads as they age.
And why it often results in uncertain conclusions. Here, all that is needed is testing under real world conditions but I doubt anyone has enough desire to do it just to satisfy curiosity…
This is a casual automotive discussion, not a formal research proposal.
Perhaps the point of all the above is just to have the last word…
The brake pad wear indicators will make contact at the minimum recommended brake pad thickness, 1 mm. Brake pads on the Prius and most hybrid vehicles wear very slowly, these brake pads could last two more years.