Car starts to shake when braking down hill

[danielsl1999gsx]

Hey guys got a question that i cant seem find an answer to. This just started to happen now since i live up in the mountains. On the way down the mountains, say about 3 miles into it as i start braking the front suspension will start to shake. But it only shakes when i brake down hill, once im on flats or going up hill it wont happen at all. Can anyone point me in the right direction what could cause this? ABS, Blown struts, control arms, bearings?

 

[Calan]

But it only shakes when i brake down hill, once im on flats or going up hill it wont happen at all.

How often do you brake as hard going uphill as you do going down?

Get some speed up on a flat surface and brake hard, and see if it happens then.

Have you checked your pads and rotors? If you do a lot of braking on mountain roads (I'm guessing yes), you may just have some build-up on the rotors or your pads could be worn, and it only shows up once the brakes get some heat in them after heavy use.

It's also possible that you are boiling your brake fluid if it hasn't been changed in a while and has absorbed moisture or has air in the lines. When is the last time you changed the fluid and bled the brakes?

 

[98dsmkid]

Check your rotors they might be warped.

 

[Calan]

Check your rotors they might be warped.

Doubtful.

-Warped- Brake Disc and Other Myths

 

[danielsl1999gsx]

Haha well the braking on flat is certainly not as hard as the braking down hill. But my rotors are pretty new (drilled and slotted) ill check for build up on the rotors tomorrow. So this happens when they get too hot?

 

[Calan]

So this happens when they get too hot?

Yep. It's called "brake fade", and can be caused by a couple of things, including the ones I mentioned above. It can be felt as a general loss of braking grip (soft pedal), or shaking if the the pads/rotors are only partially gripping.

Spend some time absorbing this: StopTech Technical White Papers. Lots of really good info there, including some from one of the best car engineers of all time (Carroll Smith).

BTW - If you recently changed the rotors...did you bed the pads in? If not, that could explain your issue.

 

[98dsmkid]

Doubtful.

-Warped- Brake Disc and Other Myths

that's some good infomation to know

 

[danielsl1999gsx]

Nice, so what would be my best option to do here? Upgrade brakes? i been meaning to switch over to Evo Brembos or Stoptechs but i cant decide whether to do this or some JIC's/KoniGC

 

[norcal_drifter]

How old are your front tires?

 

[danielsl1999gsx]

All four tires are brand new

 

[Calan]

In case you missed it...

When is the last time you changed the fluid and bled the brakes?

BTW - If you recently changed the rotors...did you bed the pads in? If not, that could explain your issue.

 

[Calan]

Any updates OP?

 

[danielsl1999gsx]

Not much really to report, with school n all.. I check my fluid and it looks new, i was not the one who changed the rotors on the car. But i did see that my pads are pretty low, so my next move is going to buy some HAWK pads and see is this helps.

 

[eltitillo]

Your have bad rotors, do a run out test to see if they are out of spec and remember every time you replace rotor replace the pads too, if you don't do that you are going to mess up your new rotors. :thumbup: