I was driving in the rain the other day and when i slammed on the brakes to keep from hitting someone, the vehicle came to a screeching halt. When i tried to drive again, it wouldnt move. It was to the point where i could floor the accelerator and the one of the rear tires would spin so i thought one of the drums had seized allowing the other to spin. It turns out that both of the front had locked up on me. I was right by a brake shop with free inspectuon when it happened so they put it on the lift and did not even want to take my money to figure it out. So i left it there and came back with a trailer 10 hours later expecting to have to winch it on. When i got in it just drove onto the trailer without issue. I wrote it off as the abs freeking out on me and a ssumed it had reset itself and drove it again today. It was fine till i about 10 miles and the brakes had been given a chance to warm up at wich point they started grabbing but not enough to immobilize it again. Anyway im stuck downtown till the brakes cool trying to decide if the problem is simply old calipers or a problem with the abs. I replaced the rotors and pads a couple weeks ago and the calipers didnt seem abnormal but the truck does have 255k on it. Is it possible i could have disturbed one of the abs sensors when i took the caliper off and that is the issue? Thanks for any input.

think about what you are asking here... ABS really, the whole point of ABS is to not lock the brakes... you have bad calipers, nothing to do with ABS, you need to get new calipers and with the mileage you have on the truck id be willing to bet those are the original calipers and they have just taken a poop on you. replace you brakes -look into the tundra brake upgrade being as though you have to get new calipers now

I definitely think it's a caliper issue, but I'd be really surprised if both calipers went bad at the same time. Next time it's locked up, jack it up and try spinning each front wheel. The one that doesn't spin is your bad one.

When you did the pads and rotors, what did you use to compress the piston in the caliper when you installed the new pads?

If you have the money, the Tundra brake upgrade is pretty nice. I have the Tundra 199 on mine and it's a very nice improvement.

The reason I thought it may be the abs is because some abs systems have the ability to trigger breaking in accordance with traction control to stabilize the vehicle. My range rover was like that. I also thought it may be an electrical problem because both wheels lock at the same time and I find that very unlikely, especially how they did it with out any kind of warning. Anyway, thanks for the input and I'll look into replacing them.

Out of curiosity, what makes the tundra breaks better? I thought that the calipers were already designed fairly well with the break apart design and 4 piston system. I thought they were trying to make up for the piss poor handling lol.

oh and I forgot to mention that I used a C-clamp to compress them and did not break apart the caliper to do it. After re installation, I bleed all 4 brakes in the order described on this forum.

Hmm, sounds like you did everything right. I'm stumped. Are you certain both are locked up?

I would think new calipers would cure whatever is wrong but I'd hate to see you just throw parts at it too.

The Tundra kit is wider. The rotors are thicker and of course the calipers are wider to fit the rotors. They don;t warp like the tiny 4Runner brakes do.

well the stock 4runner brakes are marginal at best, by upgrading to the tundra braking system(fronts only) you get thicker rotors that can handle and dissipate heat better for increased braking power/performance. there are two different calipers available for the tundras, one is a 199mm and the other is a 231mm. to run the larger caliper you might need a wheel spacer or different wheels. but the 199s should be fine with any stock 4runner wheel(excluding the 15" wheels). if you do not tow of haul heavy loads with your 4runner the 199s will be just fine.

Are they rebuildable? If I can just order a caliper rebuild kit, then that would be a cheap way to rule it out. And I might end up doing the conversion but since I would have to buy new rims and tires it might be a while.

Yes they are rebuildable. Did it on my Tacoma. Get some fine point needle nose pliers. And for whatever reason I want to say one o ring didn't come with the kit. It has been 6 years and many beers though...

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just trying to revive this thread. I'm having a very similar issue on my 97 4x4. just wondering if the calipers fixed your issue

I had a sticky caliper and would lock up, but unlock when I put it in reverse. I was a few blocks form a brake shop so took it in for a free inspection, and of course they said it was a bad caliper on the front driver side, they gave me a quote for them to do the work, which was nice, but I was going to do the work myself, It did not stick again till I got home and I purposely panic stopped it, that's when it stuck again
but for what they were going to charge me for rebuilt calipers, pads and turn the rotors I was able to buy all the parts to do the TBU.

Just a reminder when pushing in the caliper pistons back into the caliper...open the bleeder screw while compressing the caliper pistons so you don't push all the floating junk in the old caliper brake fluid back up the circuit.

The original post is 5 1/2 years old so I don't think you'll get a response.

The only thing that can make the front disk brakes seize up is the calipers, it's just tricky trying to figure out which one it is unless you can put the vehicle on a lift, shift to neutral and spin the tires by hand.

Have seen this happen on other trucks from old brake rubber lines and/or trash in the line. Replaced caliper, same problem, replaced brake line, problem solved.

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