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Triumph TR6 - Brake fade
| Hi Guys, I was out driving my TR6 yesterday and found that after I had been driving awhile without using the brakes that I have to pump them up to get pressure all the way back to the top of the pedal (when you first push on it). I have brakes but the pedal has to be pushed down quite a bit before I can feel resistance. If I pump them twice the pressure comes right back. Either way I still have the same amount of braking but is this normal? I had to replace the master cylinder last fall and bled the brakes..... Any input would be appreciated. Shelley |
| S.A. Neill |
| Hi Shelley Assuming the fluid level is constant it sounds to me like you need to adjust the rear brakes,they can fool you when you adjust that 1/4 square nut at the back plate...it feels like they are snug when you turn the wheel/drum but they will turn once more for a final adjustment. When adjusted properly ..(with the wheel off the ground) it should be almost impossible to turn the wheel by hand..I prefer the wheel rather than the drum as you get more leverage. Charlie |
| Charlie Ballard |
| Hi Charlie, Thanks for the info. When the car is up on jacks is there anything else brake related that I should check?Thanks again, Shelley |
| S.A. Neill |
| Hi Shelley, Take the drums off and tap them on the ground (away from your breathing)..brake dust is hard on the linings and your lungs, also clean the brake shoes and area with an air line or a stiff brush. Check for scoring /thickness on the drum and shoes, if you don't want to remove the brakes ect leave that to your local trusty mechanic, not sure of your level of job tackling !haha Cheers Charlie |
| Charlie Ballard |
| Charlie - You adjust the rear wheels to where they're "almost impossible to turn by hand"? Have you done a touch test where you feel how hot the drum is after a period of normal driving? That adjustment sounds too tight for me. I don't even like to hear much intermittent drag when I adjust them.... BB |
| Brent B |
| Charlie, As you suspected I am no mechanic...and even though my neighbor has a lift, I do require "supervision". However I am always willing to learn something new about my precious TR6. I am going to put her up on the rack and see if I can tighten the bolt. Were you talking about crazing on the brake drum when you said to check the drum? (Wouldn't that be from wearing through the brake pad down to the drum?) I'm still learning the lingo...and I'm not sure if that's what would happen... I haven't had the brake system rebuilt yet but maybe it's time? Thanks for your patience, Shelley p.s. I was reading about the windblockers in the thread and built one for my TR and it works great! I even bent the Lexan so that it went forward on the bend of the roll bar...was that you? |
| S.A. Neill |
| Actually one of the safest and best ways to clean rear brakes is with a garden hose. Probably best to do it on the driveway. When I first heard about doing it like that, it just seemed wrong to use water, but it works great and contains all the dust. Afterwards you can dry them out with air and a rag with no risk from brake dust. Doug |
| Doug Campbell |
| Hi Doug, I'm a bit confused...are you jacking the car up in the driveway and then taking the hose to the drums? I think I'll tighten the bolt first then if it doesn't fix it I'll go to the hose...Would the brakes still fade if they were dirty? They don't squeal at all...but something isn't quite right... Thanks Shelley |
| S.A. Neill |
| I think the common understanding of brake fade is the lessening of braking power after repeated use (they get real hot) or like from running them too much while going down a mountain. Charlie has your problem solved in his first reply, I think. If you feel up to it, taking the drums off and inspecting and cleaning is a good idea, if you don't know what's going on in there. You might see the start of a leak not noticed outside yet, check the thickness of the friction material, maybe put a little grease where the wheel cylinder slides in the backing plate and the adjusting screw, hose and blow off the dust (or use brake clean spray, letting it drip into a rag), and wirebrush and paint the outside of the drums. Or just run up the adjusting screws a little more, it should bring your pedal back. |
| Tom |
| Hi Brent, Sorry I did not make myself more clear...what I mean is when I hold the wheel with both hands I can turn it fairly easy but you should feel resistance and the wheel will not spin free once you let go..you will also hear the shoes rub against the drum..this is normal...that indicates the shoes are just touching the drum and give the max brake adjustment..at this point your emergency brake will have a nice snug and positive feel to it and hold the car well. When driving on a deserted area try slowing down from about 20 or so mph with the emegency brake only...it should be smooth and steady stopping if you can feel and hear a thumpimg type sound your drums are probably out of round and need to be turned at your local shop. The following is another way which I have tried and works although I don't agree that there is no adjustment on the front shoe..as I remember the adjusting nut pushes the cone shaped adjuster which in turn pushes both shoes outward..sorry I can't recall where I cut and paste this next bit of info.. The traditional method is to have the car on jack stands and spin the wheel as you are tightening the brake adjuster. This, however, does not take into consideration the front shoe (which adjusting has no effect), nor the proper vertical placement of the shoes relative to the drum. An alternate way to adjust the rear brakes is to pull the emergency brake handle up until you hear three or four clicks. On each rear wheel, tighten each adjuster until snug. Pulling the hand lever up three clicks sets the handle where you want it and it also positions the front shoe so it is even with the rear one you are adjusting. My mechanic tells me both methods are ok and still do the job fine. whew !! Cheers Charlie |
| Charlie Ballard |
| Shelly - You are living in Washington where I guess you have some really twisty TR roads. All TR race drivers have the problem you describe. When they drive through a series of fast twisty corners and then take a long straight-away, they always have to tap once or twice on the brake pedal before they get to their normal braking point. This is to put the pads back onto the rotors. Have you been drivng any twisty high speed curvy roads ? What happens is that during the twisty high speed curves where they don't need their brakes, the front axle spindle is bending. Yes - Bending enought that the rotor forces the rotor linings and pistons back off the rotors. Tapping the brakes re-sets the linings back onto the rotors. The race drivers have just come up with a high strength tubular modification that they fit onto each front spindle to seat on the inner race between both the wheel bearings in each of the front wheels. They uses shim-spacers to finalise the end play to a minimum. The tubular parts strengthen the front wheel spindles and these prevent the spindle from bending and this eliminates the need for tapping the brakes to re-set the front linings. Naturally, the drivers who have done this in the past few months are getting better lap times than before and better than others who have not yet added this mod. Don Elliott, original Owner, 1958 TR3A http://www.zen21606.zen.co.uk/Forum%20Gallery/don3a2_big.jpg Just back from USA (3,408 miles with no cell phone or CB and no AAA) where I watched 3 days of TR's racing at Virginia Int'l Raceway, (a Brit who had shipped his red TR6 over won again) then I drove to TRA in Ohio where I took 2nd in my concours class with 86.1 points and over 81,000 miles on "TRusty" since I finished my restoration in 1990. By the way, I drove home from western Ohio in one day (794 miles). |
| Don Elliott |
| Interesting, Don. Since Shelley said after driving awhile, your theory makes a lot of sense. And reminds me of another post somewhere that said replacing the spindles because the races were worn slightly was also a fix. But the tubes are new to me. Thanks. |
| Tom |
| Hi Shelley, Sorry I wasn't more clear. I wasn't really offering you a solution to your brake fade problem but just a hint for a safe way to clean out the brakes for anyone doing a brake job. Pull the drums off on the driveway and wash out the drums and brakes with a garden hose. The water contains all the dust and washes it away so you don't breath it in. Dry every thing off with an air hose and a rag. Then put the drums and wheels back on temporarily to roll the car back into the garage to do your work. An old mechanic told me about this. Doug |
| Doug Campbell |
| Hi Guys, Thanks for all the input. I was driving down a great twisty and bending road and that is exactly when it happens. I wasn't using the brakes because I wanted to be cautious of the "fade" as I call it. I think I'll look into the racing modification...that was mentioned...it sounds like what I'm looking for. I did adjust the nut like Charlie said and the brakes are tighter, but I'm still having to pump for pressure a bit...it's enough to make me grit my teeth sometimes. You guys are a wealth of information and I really appreciate all the help! Shelley |
| S.A. Neill |
| Like they said - doesn't sound like "fade" - sounds like you need to bleed the system again. Check around the PDWA (I think that's it) actuator for leaks - it's the 'H' shaped piece below the Master Cylinder. Brent |
| Brent B |
| Shelley, Just a couple of questions....have you noticed any puddles under the car? Is the level on the master cylinder topped up, or are you having to add fluid? Answers to these two questions might help pinpoint the problem. Or raise more questions?!?!? Rod |
| Rod Nichols |
| If you can drive without the rear brakes coming on while you have the handbrake set on the first click, and the pedal stays up, you might need to go just a bit farther with the adjustment. Isn't there some kind of worthless valve in the system that could be hanging up, too? (Like down on the frame under the carbs on the junction.) I thought I'd seen that somewhere. Is there a kit for the spindle tube mod yet, Don? |
| Tom |
| Shelley Another consideration is age of the system. Are the pads and shoes new? Are the rotors and drums within thickness spec.? The calliper pistons (and the rear brake cylinder) are designed to " retract" the pads and shoes after brake use. Use them again and the first pump gets the pads and shoes near the metal, next pump gives you brakes. I also agree with Brent that there could be air in the system....or water. Under normal driving conditions (i.e. not racing her) you should not need to pump the brakes. Brake fade ( constant brake use)and having to "pump up" ( stopping at a traffic light) the brakes IMHO are 2 different things. Tom also has a point. If the PDWA is not centered, you will get more brake action to either front or back depending on which way the PDWA plunger has moved ( fluid is shut off to either front or back). After bleeding brakes, the PDWA should ALWAYS be checked for " center". Rick C |
| Rick Crawford |
| Hi, The pads and brake shoes aren't new. As for drips on the garage floor, nothing brake related so far.. I don't know the specs for the rotor and drum thickness so I can't tell if they're within specs. I am going to bleed the brakes again. Now that you mention it I did have the brake light on the dash for a while before this whole brake thing started but after the master cylinder change and bleeding of the brakes the light went out. I will check to see if the PDWA plunger goes back to center...that is a definite possibility! Shelley |
| S.A. Neill |
| S.A. and Rick C., Just a small observation at this point in this discussion, the PDWA does not shut off the hydraulic line after it has been "activated" as in a "leak" in the system. The shuttle in the PDWA, merely slides to one side or the other, and grounds the warning light, causing it to illuminate. This is further explained on the Buckeye Triumph web site. Sorry I do not have any suggestions for the "fade" issue, except to say it more than likely is not caused by the PDWA. Mark Riddle |
| Mark Riddle |
| Shelly - I think Don has nailed it. I had the same thing which was most noticeable after reversing the car out of the driveway and applying the brakes when the steering was at at (nearly) full lock. Close inspection showed that there was very slight wear on the front stub axles where the bearings contact the axle. The wear translated into lateral movement of the disc rotor which pushed the pads back, moving the pistons into the calipers slightly. The system then had to take up the extra distance for the pads to contact the disc, hence the extra travel in the pedal. Another tell tale sign was that the pads were squeaking. Replacing the stub axles improved it quite a lot but the idiosyncrasy is still there, particularly after hard cornering. As Don says, a solution is to put spacer 'tubes' between the inner and outer bearings. They work by increasing the effective diameter of the axle making the assembly less flexible. You can use Lotus vertical links and their larger diameter axles but this is not an option for most TR owners. It is not a job for the home mechanic. To do it, you need precise machining or it won't be effective. The tubes are tapered as the wheel bearings are different sizes and must be exactly the right length. They will probably be different lengths for each side and certainly will vary from car to car. They could be machined to a standard length and then use shims, but I prefer to to get them tailored in the first place (another on my 'to do' list). |
| Roger H |
| I am a member just login in on vacation I also have a concern about my brakes now that i am driving the car more seems like the is very little brake and i really have to push on them way at the bottom of the peddle travel. I don't think that pumping them makes a difference and have replaced or rebuilt most of the brake parts. Does anyone know of a simple test to tell if the servo is actually helping the brakes. The brakes feel like the old gocarts i used to build and the closer you got to the tree the harder you pressed on the and prayed Thanks dave |
| dave |
| Hi Dave, Make sure you have lots of lining front and rear, master cylinder is topped up and no leaks around the rotors and rear cylinders, does your handbrake come up real high ? if so you need to adjust the rear brakes and that will firm up the pedal maybe that's all you need to do. Not sure yet of a servo / booster test but will look into it now that you've posed the question. Cheers Charlie |
| Charlie Ballard |
| Shelly, If you still haven't got your problem repaired, remember to keep it simple. don't overlook the obvious. If you are having to "pump up" the brakes, you definately have air in the lines, or you are leaking in the master cylinder. If you have bled the brake system and removed all the air, and are still having the same result, I would question the master cylinder that you have installed, again assuming that you have properly bled the brake system. I for one finally got tired of the pucker factor when I hit the brakes and installed a Nissan Maxima power booster and master cylinder. No more pucker factor. When I want to stop, I stop. This has been the best modification that I have made. It doesn't matter how fast it goes if you can't stop when you need to. In case you're wondering why I changed, over a three year period I went through two master cylinders. Both started to leak internally causing the same behavior that apparently yours has. Good luck. |
| Arnold Newton |
| Arnold Actually not necessarily air in the lines. If the rear brakes are not set up properly you need to pump the brake to bring the shoes into contact with the drum. Doug |
| Doug Campbell |
| Doug, I certainly agree that if the rear brakes are not adjusted properly you could get a similar response. However, since Shelly said that his problem started after he had installed a new master cylinder, that would indicate that the rear brakes must be at least close to being adjusted correctly, therefore should not be a consideration. Hence the conclusion either air or a leaking master cylinder. I would not assume a leaking wheel cylinder since there was not an indication of leak under the car. You can and often do get leaks in the master cylinder which most often goes for some time before being detected as they leak into the power booster and eventially wind up leaking onto the carpet on the drivers side as well as down the firewall in the engine compartment. Been there done that. |
| Arnold Newton |
| Check out the article at the bottom of this page. http://www.team.net/www/morgan/tech/art010_2.html#ADD2 Maybe Morgans have a similar problem? Supposedly hardening the stub axle solved the problem here. ($6) Hope this helps someone. |
| Tom |
| Roger H--Help me understand your pad push-back observation. If the wheel bearings are adjusted for zero play, how can the hub/rotor move laterally? Rick O. |
| Rick Orthen |
| I've had what you must consider some type of fading on a couple of cars including the TR6 due to caliper pisons that was almost stuck and old brake fluid. Sympthom is a very low pedal and poor braking effect at first and second try before it started to get better. This is what happened: When installing new pads I had to FORCE back the pistons to a position they last saw many years ago but not much drag and brakes seems work fine so I assessed it good enough(Hah..). But the little drag generates heat expansion that makes the piston get firmly stuck (the longer I drive the more squeel I get in corners, ref earlier post). But the scary bit is that my old brake fluid had absorbed water which dramatically was lowering the boiling point of the brake fluid and when you get local boiling in a caliper you will get air EVEN if your system was properly bled. Cure is to either get new calipers or take them apart and polish up the pistons AND change the brake fluid. Just an idea.. Goran |
| G Wennergrund |
This thread was discussed between 02/07/2004 and 28/07/2004
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