toyota Posted June 29, 2011 Author Share Posted June 29, 2011 sorry the word i used or should have used is "worn", but not below legal limit. I'm asking if i swap front (worn) to back (good), will it affect anything? Link to comment Share on other sites More sharing options...
terminator Posted June 29, 2011 Share Posted June 29, 2011 rootsbooster - so shall i take the 2 front wheels off and swap them with the 2 back wheels? Since the 2 front wheels have worn tyres, will it make any difference to the back or driving?Whack it upto high speed you may find its hard to break and pedal will feel if its pumping up n down will also get shakes on steering.Symtems will decrease at low speeds.Make sure there,s nowt in front of ya lol. Link to comment Share on other sites More sharing options...
Obelix Posted June 29, 2011 Share Posted June 29, 2011 We'll have to agree to differ on the basis of our own experiences then. Hang on - you firstly say that the wheel wobbling wont cause puslation but then the disc being warped will casue pulsation? That makes no sense. What causes pulsation is thickness variation on the disc - that's caused either by cementation causing high spots, or run out and surface polishing causes a thin spot. Link to comment Share on other sites More sharing options...
terminator Posted June 29, 2011 Share Posted June 29, 2011 Hang on - you firstly say that the wheel wobbling wont cause puslation but then the disc being warped will casue pulsation? That makes no sense. What causes pulsation is thickness variation on the disc - that's caused either by cementation causing high spots, or run out and surface polishing causes a thin spot. You should not get pulsation on break pedal if its wheel but will if its disk You will get it on steering though if wheel. Link to comment Share on other sites More sharing options...
RootsBooster Posted June 29, 2011 Share Posted June 29, 2011 Hang on - you firstly say that the wheel wobbling wont cause puslation but then the disc being warped will casue pulsation? That makes no sense. What doesn't make sense about it? The wheel isn't the disc. What causes pulsation is thickness variation on the disc... Or disc warping ....that's caused either by cementation causing high spots, or run out and surface polishing causes a thin spot. All usually easily visible. If the disc was mounted incorrectly, the pulsing would have been there since day one. If disc thickness variation was due to surface deposits, you would see evidence of this on the disc itself. If it was due to a thin spot, a vernier calliper will show this. If neither of the previous two are present, and there is disc run-out, it is most likely warped discs. If it is the hub or bearing itself, then it will feel no different after fitting new discs. Link to comment Share on other sites More sharing options...
RootsBooster Posted June 29, 2011 Share Posted June 29, 2011 sorry the word i used or should have used is "worn", but not below legal limit. I'm asking if i swap front (worn) to back (good), will it affect anything? In what way are they worn? is it on one edge only, both edges, central area, evenly worn? Link to comment Share on other sites More sharing options...
Obelix Posted June 29, 2011 Share Posted June 29, 2011 What doesn't make sense about it? The wheel isn't the disc. Or disc warping All usually easily visible. If the disc was mounted incorrectly, the pulsing would have been there since day one. If disc thickness variation was due to surface deposits, you would see evidence of this on the disc itself. If it was due to a thin spot, a vernier calliper will show this. If neither of the previous two are present, and there is disc run-out, it is most likely warped discs. If it is the hub or bearing itself, then it will feel no different after fitting new discs. The wheel is generally bolted directly to the disc though. If the wheel is wobbling or rather showing run out so will the disc. If you get cementation forming on the disc surface there is no certainty at all it will be visible. I've seen some where the only way you could tell was with a brinell gauge to measure the surface hardness. Disc warping doesn't cause a pulsation in the pedals, nor a shake in the wheels. It has no effect noticeable as there is not a sudden step change on the surface (unlike a crack which would) and there is no change in thickness which affects clamping force. A disc mounted with excessive run out, or one where the rotor is not true to the mounting plane on the assembly will also not cause any problems even though the disc is moving back and forth inside the caliper. It's only when they surface wears preferentially on the high spot due to passing and touching the pads that you get a thickness variation and notice the effects on steering and pedal feel. IF the theory about warped discs was correct you would notice it immediately on fitting a disc with excess run out. You don't - ergo the problem cannot be related to small axial displacements of the disc, and it has to be related to thickness variation. Link to comment Share on other sites More sharing options...
terminator Posted June 29, 2011 Share Posted June 29, 2011 The wheel is generally bolted directly to the disc though. If the wheel is wobbling or rather showing run out so will the disc. If you get cementation forming on the disc surface there is no certainty at all it will be visible. I've seen some where the only way you could tell was with a brinell gauge to measure the surface hardness. Disc warping doesn't cause a pulsation in the pedals, nor a shake in the wheels. It has no effect noticeable as there is not a sudden step change on the surface (unlike a crack which would) and there is no change in thickness which affects clamping force. A disc mounted with excessive run out, or one where the rotor is not true to the mounting plane on the assembly will also not cause any problems even though the disc is moving back and forth inside the caliper. It's only when they surface wears preferentially on the high spot due to passing and touching the pads that you get a thickness variation and notice the effects on steering and pedal feel. IF the theory about warped discs was correct you would notice it immediately on fitting a disc with excess run out. You don't - ergo the problem cannot be related to small axial displacements of the disc, and it has to be related to thickness variation. :hihi::hihi: Link to comment Share on other sites More sharing options...
RootsBooster Posted June 29, 2011 Share Posted June 29, 2011 The wheel is generally bolted directly to the disc though. If the wheel is wobbling or rather showing run out so will the disc. The Calliper is also bolted to the hub body and will also wobble with the pads, discs and wheel in unison. This wouldn't produce pulsation in the pedal. If you get cementation forming on the disc surface there is no certainty at all it will be visible. I've seen some where the only way you could tell was with a brinell gauge to measure the surface hardness It would cause a disc thickness variation which you would be able to measure with a vernier calliper. Disc warping doesn't cause a pulsation in the pedals Yes it does. nor a shake in the wheels. It can do, which is felt through the steering wheel. It has no effect noticeable as there is not a sudden step change on the surface (unlike a crack which would) and there is no change in thickness which affects clamping force. The "wavy" shape of a warped disc pushes the pads in as you're trying to push them out, in, out, in out = pulsating. If you're not sure of what I mean by warped then think of the brim of a fedora hat, or an old wobbly record. Quite a few posts back I did say let's agree to differ but you don't seem to want to. I've had enough for tonight so that's probably all from me for now. Link to comment Share on other sites More sharing options...
Obelix Posted June 29, 2011 Share Posted June 29, 2011 The Calliper is also bolted to the hub body and will also wobble with the pads, discs and wheel in unison. This wouldn't produce pulsation in the pedal. It would cause a disc thickness variation which you would be able to measure with a vernier calliper. Yes it does. It can do, which is felt through the steering wheel. The "wavy" shape of a warped disc pushes the pads in as you're trying to push them out, in, out, in out = pulsating. If you're not sure of what I mean by warped then think of the brim of a fedora hat, or an old wobbly record. Quite a few posts back I did say let's agree to differ but you don't seem to want to. I've had enough for tonight so that's probably all from me for now. A disc mounted with excessive run out, or one where the rotor is not true to the mounting plane on the assembly will also not cause any problems even though the disc is moving back and forth inside the caliper. It's only when they surface wears preferentially on the high spot due to passing and touching the pads that you get a thickness variation and notice the effects on steering and pedal feel. IF the theory about warped discs was correct you would notice it immediately on fitting a disc with excess run out. You don't - ergo the problem cannot be related to small axial displacements of the disc, and it has to be related to thickness variation. The trouble is you are advising someone on braking systems when you clearly have flawed knowledge of how they work. This is not a good idea. It makes me wonder what else you don't know. I've worked on these systems. I build systems like this - it's what engineers do. Please, don;t assume that some folklore knowledge that gets handed down about warped discs is going to be true just because everyone says it is. To the OP - take it to a reputable garage and let them have a look at it. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.