| Author | Message | ||
     Brian (Bthaxton) Member Username: Bthaxton Post Number: 77 Registered: 02-2003 |
I have read the archives. However, I still have a problem. I have a '97 D1 and recently overhauled the brakes on all four corners: 1. Rotors, stock type (DAP Inc.) 2. Pads (Ferodo - DAP Inc.) 3. Flex Hoses (Rubber - DAP Inc.) 4. Master Cylinder - (Replaced all seals and reservoir) 5. Replaced hub seals, repacked bearings, adjusted swivel preload, etc. etc. etc. Now, I have a shimmy when the brakes are applied, usually at a higher speed (like on an interstate exit ramp). It sometimes lessens when the brakes are warmer. I am going to go into detail because I want someone to relate experience(s) to me. I am not quite a repair novice, and I think I know what it is, but I want educated opinions. Here goes: On the front, as I said, I replaced the rotors. I disassembled the hubs (done it 5 times before at least) and separated the old rotors from the hub flange assembly. I cleaned the 14mm 12-sided bolts with a wire brush on my air angle grinder, and I cleaned the bolt holes. I took the new rotors and put them in my vise and ground/roughed them with a medium-grit disk in my angle grinder. I then ground the area around the bolt holes on the hub flange to improve the flange/rotor mating surface (I made it shiny again). I then replaced the grease seal at 4mm, installed the new rotors on the hub flange, and torqued the 14mm bolts equally in a star pattern (73nm I think). I used Loctite red (high temp), and was very careful about equal torque all around. I then cleaned the stub axle, checked the swivel housing bolts torque, set swivel preload, repacked the bearings with grease, and installed the hub/rotor assembly. The outer bearing was installed, and I followed the hub nut torque procedure (new Tech Bulletin version) to set the "play" in the hub. I then cleaned the rotors with brake parts spray and installed the old calipers with pads. The back was pretty much the same procedure, with the exception of the ABS ring on the hub flange. I was not able to actually torque the 10mm ring nuts because of their position, but was careful to tighten them in a star pattern, not to overtighten, and apply equal torque all around. During the test drive I noticed the shimmy. So, I disassembled the front hubs, detached the rotors, cleaned the bolts again, and repositioned the rotors in relation to the hub flange assembly. I reinstalled and retorqued everything. This lessened the problem slightly, I think (?????), but the shimmy is still there. I did not disassemble and reposition the rear rotor/hub assembly. What is causing this shimmy? I had my tires rotated and balanced and aligned my toe-out. The best I can describe the shimmy is more of a "shudder" in the steering wheel and brake pedal when the pedal is depressed, not either exclusively up/down or side-to-side. I am not trying to present a riddle, but I have my ideas and would like suggestions. Again, I have read the archives (there were 2716 results found). What is causing this???? | ||
| Ryan Graham (Ryangraham) Member Username: Ryangraham Post Number: 45 Registered: 01-2004 |
Sounds like you got some warped rotors out of the box. Doesnt happen often, but is possible. On the side of the rotor box it will say "Stock flat, not on edge" or something to that effect. If rotors get stocked on their edge, they will warp eventually. I know it sounds ridiculous, but I have seen it before. Sounds like you were careful to keep the rotor mating surfaces clean, don't know what else it could be. | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 768 Registered: 04-2001 |
I would say either the hubs are not tight enough or you have a bad rotor. Once again I will express my disdain for crap aftermarket parts. I can't see why something like rotors anyone would not go with Genuine or some known good brand. Ron | ||
| Brian (Bthaxton) Member Username: Bthaxton Post Number: 81 Registered: 02-2003 |
Ron and Ryan, Since you both tend to concur (and you are not the only ones--including myself), here is what I thought almost immediately: 1. Warped rotors out of the box - that is why I listed where I bought them. 2. I might have accidentally ground a concave portion in the rotor(s) with my angle grinder, but I seriously doubt that a reasonable person could do THAT much damage, especially since my angle grinder tends to tax my compressor capacity. 3. Bad caliper(s) which cause uneven pad contact. However, front calipers were rebuilt about 20K miles ago. 4. Very small possibility of over-grinding the hub flange/rotor contact area. But, again, I doubt it. One telltale sign that I see is the "ridge" that has formed around the edge of the rotor from pad wear is eneven. In my defense, I planned to use these rotors until I bought some DBA rotors from EE. I tried to show in my initial thread post that I am extremely careful and detailed in my work (it is pretty much a hobby), and hopefully my problem was not my own fault. Which leads me to a question: How adequately should a new rotor be ground/"roughed up" prior to installation, and by what method? Thanks for the answers. Brian | ||
| Joey (Joey4420) Senior Member Username: Joey4420 Post Number: 585 Registered: 04-2003 |
I am a back yard mechanic at best, but I have been taught be many brake mechanics, that it is always a good idea to have new rotors turn "out of box" in order to ensure that they are not warped. But take this a hear say, since I do not work on brakes for a living. I have always followed this advise and have never had a shimmy or shake yet with new brake rotor installs. | ||
| Ryan Graham (Ryangraham) Member Username: Ryangraham Post Number: 46 Registered: 01-2004 |
Brian, I still think that you have a problem with a bad rotor. Joey is right, back in the "olden days" they recommended that you turn rotors before installing them, but no one wanted to start with a rotor that had .020" ground off it (not to mention flat rate didn't pay for turning them) so they started flat stocking them, using different materials, and making them to more exacting standards from the factory. Generally unless you get the cheapest "white box" rotors (usually under $20) you shouldn't have a problem with rotor warpage out of the box, however, sometimes Land Rover rotors will sit on the shelf for longer periods of time than others, causing them to warp. Everything has a little warp in it, your hub, the new rotor, etc. and sometimes if you clock the rotor on the hub so that both the hubs high spot and the rotors high spot coincide, they may exceed the specs for runout, causing a pulsation. You can check this by puttin a dial gauge on your rotor and measuring the runout, then mark it, then clock it 180 degrees and measure it again. Can be a p.i.t.a. to take apart the hub every time though. Grinding a "non-directional" finish into your rotors before installation is ok, but doesn't really matter. It helps to seat your pads marginally faster, but doesn't help the overall performance as I'm sure you noticed after about 100 miles the rotors were smooth again. You would have to do quite a bit of grinding to give your rotors a noticeable thickness variation. It is unlikely your caliper caused your problem unless your pads werent moving at all, which is very unlikely with rebuilt calipers. I couldn't tell from your original post if you used a disc or a wire wheel on your hub, but either way it would be pretty hard to grind enough off to make a difference. It doesn't take much to cause pulsation at higher speeds, but judging by how careful you were with torquing and assembly I would still say you have a warped rotor. Most shops have an "on the car" lathe that turns the rotors on the hub so that the total runout comes to less than .002", usually its about $50 per rotor because they're a pain to set up, but may be the quickest/cheapest/easiest way to clean up your pulsation. | ||
| Brian (Bthaxton) Member Username: Bthaxton Post Number: 85 Registered: 02-2003 |
I think I'll reposition (reclock) the hubs one more time to "seal the deal". I have a grease pencil that I use for marking positions on the Disco. I don't have a runout gauge, and I haven't been able to find where to rent/borrow one. I have looked for one already to try and diagnose my problem. I almost feel like new front rotors (and new grade 8 bolts) would set me free. I got almost 100k miles out of my first rotors (I mic'd them periodically), so I am still ahead of the curve. I take good care of my vehicle. I just wish it was a NAS 110 (did I just say that?) Thanks for all of the posts. They confirmed what I thought. | ||
| Rick Clarke (Tugcap) Member Username: Tugcap Post Number: 47 Registered: 02-2002 |
Just curious Brian, was the pad wear even on the front rotors? I mean were the pads wearing evenly inside and out, about equal thickness? I just did pretty much same in the front of my 95, and both my calipers were needing rebuild: pistons were corroded, and working the inside pads much harder than the out. I used Brembo rotors, from Nathan crabtree and am happy sofar. | ||
| Brian (Bthaxton) Member Username: Bthaxton Post Number: 106 Registered: 02-2003 |
Rick, The pads were not worn enough to tell yet. I did check that, though. | ||
| Bazzle (Bazzle) Member Username: Bazzle Post Number: 109 Registered: 09-2003 |
I will back it in that the grinding with your angle grinder has caused minute damage. I always just clean new rotors with solvent only and put on. I dont like the idea of anything stronger than a wire brush. bazzle | ||
| Bazzle (Bazzle) Member Username: Bazzle Post Number: 110 Registered: 09-2003 |
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm Bazzle |
