Val Demar Posted October 6, 2008 Share Posted October 6, 2008 What can be the cause of knocking sound under braking? It seem to get one knock per wheel revolution, or at least it is related to rotation speed as knocking slows down with deceleration. Knock is more pronounced under heavy braking. A little history, not so long time ago I installed Hawk performance pads front and rear, and dba 4000 rotors front. Rear rotors are stock but were turned at the time of pad replacement. The sound seem to come from the right rear wheel, so it is a hawk pad against stock rotor. Sometimes the sound disappears for a short while but always come back. Even when there is no knocking I hear grinding sound under braking that seem to come from the same corner (but it is really hard to tell for sure). This doesn't seem to be ABS related as there is no pedal feedback. Any ideas? Link to comment Share on other sites More sharing options...
jim1969 Posted October 6, 2008 Share Posted October 6, 2008 check for loose endlinks. Link to comment Share on other sites More sharing options...
Val Demar Posted October 6, 2008 Author Share Posted October 6, 2008 Hmm, you think loose endlinks can cause knocks whose frequency seem to be directly related to wheel rotation speed? I'd expect them to be knocking on bumps or in turns. Link to comment Share on other sites More sharing options...
magnetic1 Posted October 7, 2008 Share Posted October 7, 2008 Check to make sure the pad is seated correctly in the clips. Also make sure the caliper guide pins are on tight. Free Sonax Cleaner Deal http://www.brakeswap.com Carbotech, Hawk, PFC, DBA Rotors, Motul, Wilwood, Castrol... Great service. No bumping required ! Link to comment Share on other sites More sharing options...
jim1969 Posted October 7, 2008 Share Posted October 7, 2008 Hmm, you think loose endlinks can cause knocks whose frequency seem to be directly related to wheel rotation speed? I'd expect them to be knocking on bumps or in turns. Happened to me a couple of months ago. Link to comment Share on other sites More sharing options...
Val Demar Posted October 7, 2008 Author Share Posted October 7, 2008 Checked pads, caliper guide pins, and endlinks, everything appears to be tight/properly aligned. Drove the car for 20 mins with multiple repeated slow downs from 40-50 to 5-10mph, the noise seem to go away as brakes heat up, which makes me think it is not coming from suspension. Stopping power is stong. I also noticed rear pads started to smell like they were burning during this exercise, is this normal? Stock pads were pretty much odorless. Perhaps the problem is looser tolerances for the pads and they "play" in the caliper seats, the play naturally goes away as things expand when heated. Another thing is I used this red stop-squick that comes with the pads between the pads and shims, as far as I can tell it is still viscous and in theory can make the pad to move easier back and forth as friction is reduced between the shim and the pad. Kinda thinking should probably go back to stock, at least on the rear axle... Link to comment Share on other sites More sharing options...
G mang T Posted October 8, 2008 Share Posted October 8, 2008 check to see your bolts are all correctly tightened.. my lugs were loose and i heard the same thing Link to comment Share on other sites More sharing options...
Val Demar Posted October 8, 2008 Author Share Posted October 8, 2008 check to see your bolts are all correctly tightened.. my lugs were loose and i heard the same thing This may well have been it. I noticed not all lugs were evenly tight. There was some initial knocking when I reinstalled the wheel and made sure everything was tight but it disappeared after a couple of spirited stops, which I attributed to brakes heating up. This is day 2 and no knocking since then, even when cold. Keeping my fingers crossed... Link to comment Share on other sites More sharing options...
Val Demar Posted October 23, 2008 Author Share Posted October 23, 2008 For those who are interested the noise was because of badly turned rotor on one side, had both redone today and so far so good (knocking on the wood). Link to comment Share on other sites More sharing options...
Val Demar Posted October 24, 2008 Author Share Posted October 24, 2008 While the knocking issue seem to be resolved I now get annoying scraping sound under very low speeds (like when starting to move) which goes away over 5ph. Any ideas why it can be? Link to comment Share on other sites More sharing options...
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