For a little while now I have been experiencing a knock (mostly of the front wheels) when I first hit the brakes either going forward or in reverse. It was not that big of a deal, but seems to be getting worse. So, when i back out of my garage, they "knock"/"click" on first brake engagement. The again when moving forward on first brake engagement. It sounds to me like the pads are not fitting properly so there is some play. They are Hawk HPS pads. Anyone got any thoughts on this? Is it just the pads? Can this be fixed? Or, could it be something else? Thanks,
This is the nature of the brembos because of the way they work with those slide pins. I think its literally termed 'knockback' as in track situations i've read mentions of a light tap on the brake to re-seat the pads on the rotors before an actual braking point. By brembos do this everytime i first start moving the car and especially upon direction change. However, I would think to play it safe and also double check that the caliper bolts are torqued down properly so there isn't any wiggle from the caliper to the hub ( i had that happen on my 6pot recently)
Thanks for the info. Does it have to do with the aftermarket pads too? I can't remember if it happens or not with my track pads (Hawk HP+) or if it was happening with the stock pads
When i bought my car being the 3rd owner but only at 19k miles, i still had the OEM brembo pads and they knocked from day one, but mostly in that reverse to forward situation that you mentioned. I've have 3 sets of HP+ on my car and to me the knock is the same 'loudness' as when i had the OEM pads. Just as you know, the HP+ will squeal a bit when its out of temp.
Not specific to STI's, but usually there's a metal "spring" clip at each end of the pad. They're there to hold the pad snug & account for thermal expansion differences between the pad & the caliper. Are all your clips still there? If not, a replacement pad set should also come with new clips.
I doubled up on shims up front and it went away. This was on a WRX. Might be that Hawk expects more heat as they're being used primarily as a motorsport pad.
I think i know what clips you are referring to, and I was told in the past they don't really do anything...these guys?
i believe what you have circled are the wear indicator's they squeal from rotor contact when your pads are low. I think superdude is mentioning the whole thin metal shim over most of the pad that is visible in that pic also edit: or well some caliper styles do have this bent metal shape that the pads pop into and holds them in tension. From how the brembos use those guide pins, I guess its not really there on a STI to that extent
My stock 2014 STi with 11K miles does it too. I wouldn't worry about it, personally. I find the squealing more annoying than the knocking, but such is the nature of the beast.
"knockback" is in reference to the floating caliper and fixed rotor with a dash of wheel bearing play. About the only way to explain it is like the ABS pump pulsing the brake pedal. The 02-05 WRX model is notorious for this with the old 2-pot calipers on front. If running the old 2-pots, make sure to pull the boots and pins for a cleaning and relube when changing pads. The 4-pot WRX and Brembo calipers will chatter when changing direction by design. If it's frequent and you have some uneven wear on the pads, then it may be time for new dust boots and piston seals along with a fluid flush. Next time you change pads, take the time to clean the boots and check for tears and cracks. Scotchbrite the pins before installing them. Add a little moly grease but make sure to wipe off any excess. Some lube on the back of the pads will help matters too. Shims will help with the noise, there is a rubber coated style or you can go baller with titanium