Shaking while braking, maybe not the discs ?

Hi,

since a few days, our steering is shaking when braking. I can also feel the shaking the pedal. Stronger at high speed, moderate at normal speed, and almost unnoticeable at slow speed (below20mph).

It's like this since 3 days, but it's getting worst every day.
Last job at the garage was a full inspection of the brake system and front pads replacement and one wheel stud replacement.

Removing the front wheels, I pressed the pads against the discs to notice any gap while rotating the disc.
On one side, the disc seems the get closer to the pad (by maybe half a millimeter, no more). Is that enough to call it warped and to cause the shaking ? Or should we check something else in the front train, or steering unit ?
On a side note, after a long drive and barely using the brakes to stop, I checked the temperature on the disc, and none of them were too hot. Maybe a sticky piston could heat the disc with the new pads but I would expect a super hot disc on one side to explain a disc warping....
Jeez I hope we are gonna fix it, we have to sell the vehicle before going home !
cheers and happy new year every one !

David

Remove, copper slip the pads and replace. Ensure the spring seats at each end of the pad are seated correctly and that the shims have been fitted the right way round. Also ensure the caliper slides in and out easy on the upper shaft.

Hi Clive,
pads only have 2000kms and I noticed some streaks.
I did a full clean up of the springs and seats. They are in good position, shims also properly fitted.

Checking the disc carefuly on one side, the disc appears to be warped by less than half a millimeter. That's really small, but I don't know what is the tolerance for the in-out.
Now thanks for pointing the shaft, on this same side, I realized the lower shaft is not moving the same way. It comes in and out very easily, behaves a bit like a shot shockabsorber. Almost seems a bit loose. Others are smooth, bit spongy.
Could that be the explanation ?

We're gonna check tomorrow for a garage in town, I just hope we won't have to replace the disc as they don't have these vehicles in Argentina and the van is shaking too much at the moment to go any further.

Thanks again Clive !

here is a pic of both pads on the right disc
1mm deep streak on top left and bottom right

To follow on this, we went to about 12 places in town, including toyota. They don't have new discs in the country, and they all said our disc are warped.
I cannot understand how can we warp the disc during our last 1200kms cruises on the flat and straight roads in south patagonia....... We cruises at 55mph, and we barely need the brakes to stop at the gas station. Could make sense while going down the altiplano above 4000m, with super steep roads, but on the flat, it just doesn't make sense to me.

Our last option seems to machine the disc to make them flat again, does any one have any experience with that ???
cheers

Using this setup, in different places, I checked for any run on and off in the wheel, hub and disc.
I use the caliper as my reference object.

here is the disc, wheel nut is clamped to the caliper :


and here is the hub (on the right), the screwdrivers is clamped to the caliper :


They all run off by some distance, at the same moment during one revolution.
The variation occurs on a half revolution, and since I've got this on at least 3 elements (wheel, hub and disc), I'm wondering if the whole hub unit is simply not in place.
The gap on the disc is about 1-1.2mm, that's huge ! That cannot be heat distortion ?!

Last time we serviced the van, we had to replace a wheel stud on that wheel, and it requires to extract the entire 4wd manual lock hub + front rotor to finally extract the broken stud. We don't have tools to open it again, but is it possible to mount back the rotor with maybe some dust or something else giving a slight angle to the entire disc-hub-wheel bloc ?

thanks

I'm sorry I've no expertise with the 4WD system.

The new pads may highlight any problem, were the old pads worn unevenly?

As for refitting incorrect seated hub, well that may be the answer, but would be a big job to find out.

I'd try a new set of pads as the first and cheapest option.

Old pads were looking nice and flat, not a scratch, the 4 of them looking the same !
We have other pads in the trunk and we will try this tomorrow.

Also, 2 days ago, the shaking was very strong when braking around 40mph, but yesterday, at any speed, even over 60mph, it was only a small vibration in the pedal. Today, it's like enjoying an earthquake when touching the brakes at 30mph....
Something has to move.

I tried going down hill and only using hand brake to check the rear drums, no shaking. We balanced the front wheel just in case, but they broke one more wheel stud on the same wheel. So we managed to bargain a price to have them remove the entire wheel hub assembly, check the rotor, and replace all the wheel studs.
Good thing is we can stay all day in the garage to monitor everything. We'll do that next friday.

Fingers crossed..... since this is the end of the trip and our bank account is running low, we have to make careful choices there !

Let's hope it is a quick fix. Be real bad to end on a sour note.

Going to the shop was not a so good idea....
We had an argument with the boss because we spent too much time inspecting how the guys were working on our wheel. Remember they use the sledgehammer very often in south american shops.....
And while talking to the boss, the other guys had the brilliant idea to use a clamp to hold the rotor while using a long wrench to unbolt the hub. Obviously, the disc popped out of the clamp and we now have deep streaks on the surface......
At least we now have our disc running straight ! Yeaaah ! But after a test road, still shaking

I checked again all wheel studs, I changed all brake pads with new one, still shaking ! It's more subtle now, and more consistent, but feels like driving on rumbling stripes when touching the brakes around 60mph....
We did an inspection of the steering system with other friendly mechanic, and everything looks good on this side.
Ok, since our disc was running with an angle, maybe it went too hot, and warped..... I'm thinking about going to a shop to machine the disc, but that means extracting the hub again..... and no way here to find the proper tool.

It took weeks in town to finally find a decent place to repair our van ! We found a very small garage operated by 2 guys only working with toyota.
After inspection, our rotor and hub went to a lathe machine, that's where the guy told us our disc was warped, but also the mounting part of the rotor, and the hub as well. The whole thing was also sitting with an angle on the axis..... Because of the angle, and the damaged hub, the rotor was always hitting the pads and warped....
Our rotor and hub machined in the lathe, back in position, grease, and proper tightening of every part, the shaking is gone !!! Final bill from these friendly guys is 70euros (20e for labor, and 50e for the lathe).
They even replaced a few parts and washers in the process, since the old ones were worn with all the sledgehammer hits from previous mechanics......

It all started with a broken wheel stud, and we didn't realize the job was so complex. So if you have a 4wd van, with the hub lockers in front, always tighten the studs yourself !
Broken wheel stud are very common in south america, and someone told us this is because they spray wd40 or other lubs on the studs before tightening, is it possible ?