Author |
Message |
Trevor Tai
Tinkerer NSW Soarer GT-TL
Posts: 86 Reg: 07-2005
| Hi Guys, Has this happened to anyone? This happens once in a while, and when it does, it happens in hairy situations! My brakes work great when the road is smooth, the Lucas pads I changed over to does wonders. But whenever I'm on a very bumpy road and slam on the brakes when a stupid taxi pulls out in front, the brakes feel like they are only working at 20%. The pedal doesn't feel firm, and the brakes sound like brakes on a stopping semi-trailer. Don't know if these thing contribute to it. My car has been lowered, the front lower bushes need changing and when slowing down, after pressing the pedal for a second time, it feels firmer (brake booster problem?). But the pads are new and have been run in, have done a brake fluid flush. Help... someone?! |
Peter Nitschke
JunkFilterer South Australia GT4.0 V8
Posts: 5499 Reg: 11-2004
| Got TRC or vacuum booster? |
Dave Hart
DieHard Waikato UZZ32
Posts: 765 Reg: 08-2005
| No alarms on your dash? |
Trevor Tai
Tinkerer NSW Soarer GT-TL
Posts: 87 Reg: 07-2005
| No TRC or vacuum booster or alarms. I have ABS though, but I don't brake hard enough to set it off. Any other thoughts? |
Peter Nitschke
JunkFilterer South Australia GT4.0 V8
Posts: 5504 Reg: 11-2004
| Without TRC, it is a vacuum assisted power booster, you can't have NO booster. Not that it helps at this point other to eliminate issues involved with the TRC system. The noise, is it a Psssshhht! type noise? Usually you don't hear the booster working over the general road noise. Suggest have the car parked, with bonnet up, have a friend press on the brakes while you listen to the noise to get a better idea of what it is. General good advice however, is with any unknown brake issue, get it looked at by a brake specialist and fast. |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2281 Reg: 07-2005
| If you do not brake hard enough to trigger the ABS when you are about to crash into another car ("it happens in hairy situations") then WTF are you doing? |
Peter Nitschke
JunkFilterer South Australia GT4.0 V8
Posts: 5510 Reg: 11-2004
| Trying to? |
Jeff Smith
DieHard NSW TT Limited :-) equiped toyota torsen diff
Posts: 505 Reg: 07-2005
| Trevor! Get your pots checked! I had the same drama and found that one of my front pot on the caliper's was jamed,almost fused.Thank's to niell bond he discovered it,He said it is common for the TT. |
Matthew Sharpe
Goo Roo North Island JZZ31
Posts: 1398 Reg: 10-2005
|
Peter Nitschke wrote on Wednesday, August 16, 2006 - 04:50 pm:General good advice however, is with any unknown brake issue, get it looked at by a brake specialist and fast.
Damn straight! Most important part of the car along with steering. Don't muck around, get it looked at by an expert. |
Trevor Tai
Tinkerer NSW Soarer GT-TL
Posts: 88 Reg: 07-2005
| Oh, so mines a vacuum boost. Thanks for clearing that up Peter. The sound is that of a semi-trailer's braking, the low screech before the psssht. Semi-trailer's version of squeaky brakes? ha...ha..., very funny David/Peter! Jeff, I was able to push the pots back when I changed my brakes. So it doesn't seem to be fused. I just had another thought, I have very low and hard springs. Could the wheels just be skimming the top of the very very bumpy road from the rebound rate? This could happen by the ABS kicking in when the wheel has stopped spinning (between bumps). And when the ABS lets go, the wheel just happens to make contact with the ground again, and the car would then keep rolling forward. I have tested my ABS, and compared to other cars, the intervals between the braking and letting go are longer. Can we shorten this interval somehow? or is it a computer controlled thing? |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2285 Reg: 07-2005
| So, your springs are too hard for good traction. |
Trevor Tai
Tinkerer NSW Soarer GT-TL
Posts: 90 Reg: 07-2005
| springs are ok all the other times, just wondering if the ABS could be confused? |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2292 Reg: 07-2005
| If the ABS is "confused" in the manner you described in your earlier post then what I said stands (although perhaps I should have said "suspension" rather than "springs"). Perhaps the damping ratio is wrong. Too soft will allow harder springs to chatter the wheels without control, while too hard will prevent them following small road variations quickly. When you lowered it what work was put in to the damping? I would look at the changes you have made before I worried too much about possible user-tuning of the ABS. |
Trevor Tai
Tinkerer NSW Soarer GT-TL
Posts: 92 Reg: 07-2005
| Thanks for that David, that's probably why. I only changed the springs and the shocks are stock. Time to get coilovers I guess! |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2311 Reg: 07-2005
| Sounds like the go. |
Matthew Sharpe
Goo Roo North Island JZZ31
Posts: 1416 Reg: 10-2005
| There is an advert on TV here at the moment for Mag & Turbo warehouse giving away king spring kits with wheel & tyre combo's - the guy claims "improves your cars handling by up to 30%" - makes me mad as its just as likely to f*ck your handing up by 30% or more if you don't also match it up to the dampers, correctly align everything etc! The number of badly lowered cars you see around bouncing up and down like pogo sticks... |
Dan McColl
Goo Roo Victoria UZZ-32 V8 Soarer #138
Posts: 1234 Reg: 07-2005
| Agree with Matthew, And Trevor, It sounds as though you've hit the nail on the head, The combination of stiff spring and worn bushes allows the wheel to bounce off the ground on rough roads, (notice it's fine on smooth roads), Obviously you're not going to have effective braking if the tyre is only in contact with the road half the time. Get your suspension sorted pronto. |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2407 Reg: 07-2005
| It is the damping which is the key, Dan. Stiffer springs are fine if you also set damping to suit. The identified problem is that springs were stiffened without other compensating changes. Worn bushes would certainly exacerbate the problem. |
Justin Hughes
DieHard VIC TT
Posts: 870 Reg: 07-2005
| Ahhhhhhhhhhh HA !!!!!!!!!! That explains a lot then - Hmmmmmmmmmmmmmmmmmm I've had this car screeching and scrabbling for brakes trying every trick in the book to stop the thing a few times. ABS just not responding at all - very scary when you're used to it AND expecting it to be there It's taken me a few years to get my head around Full Tilt driving WITH ABS after years and years and years of driving Full Tilt with NO ABS |
Dan McColl
Goo Roo Victoria UZZ-32 V8 Soarer #138
Posts: 1246 Reg: 07-2005
| You need to try it with A-Sus and A-4ws, Juzza, You'll love it. David, The problem with stiffer springs is that you need stiffer dampers to control them. (dampers control the springs, springs control the car) this in turn means that the spring can't react quickly enough to follow the road with the stiff damper restricting it. Vicious circle and all that. Without the correct damper the spring will just bounce and that will be even worse. |
Trevor Tai
TryHard NSW Soarer GT-TL
Posts: 104 Reg: 07-2005
| Well, got my bushes done, steering and braking is slightly more predictable now! The braking problem doesn't come as often, something that supra brakes and HKS Hipermax II coilovers will fix! |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2411 Reg: 07-2005
| Dan, can you read? WTF did you think I was saying?? Any more eggs you would like to teach me to suck? Edit: Excuse my considerable exasperation but if you go back to the beginning of the thread, after various people talked about the ABS and brakes I was the first to identify precisely that problem, that his dampers were not matched to his spring hardness. This thought you then attributed to Trevor himself before going on to lecture me monosyllabically on exactly the point I had made, not only here but in this thread from yesterday: http://soarercentral.com/sc-forum/messages/292/97655.html?1157887646#POST130177 I have noticed quite a bit recently that people are paying no attention to what has been written above them before throwing in their 2c worth. I had not expected you to join them. |
Peter Nitschke
JunkFilterer South Australia GT4.0 V8
Posts: 5772 Reg: 11-2004
| Drop something sport?
Seriously though, it can be a common problem |
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2413 Reg: 07-2005
| That's an insult peter. I reckon it hit the other wall |
Peter Nitschke
JunkFilterer South Australia GT4.0 V8
Posts: 5777 Reg: 11-2004
| And bounced back |
Dan McColl
Goo Roo Victoria UZZ-32 V8 Soarer #138
Posts: 1256 Reg: 07-2005
| I was trying to say that irrespective of whether the damping is correct or not, too stiff a suspension will cause the tyres to lose contact with the road if it's bumpy. I apologise if I was hard to understand, I have been in America for 2 months and may still be speaking their language a bit.
|
David Vaughan
Goo Roo ACT V8 Ltd manual
Posts: 2420 Reg: 07-2005
| Subject change there. |
Dan McColl
Goo Roo Victoria UZZ-32 V8 Soarer #138
Posts: 1257 Reg: 07-2005
| Not really. |