Bedding in VR disc brakes problem

[kswenson]

I have just replaced all four rotors and pads on my VR executive, but they just don't seem to be bedding in. I ftted DBA standard rotors and Bendix Stealth pads, but the car just doesn't want to stop. All have been fitted properly and the calipers etc are working properly. I have now done over 220 kilometers over the past three days trying to bed them in, but the brakes are still lousy. I have no emergency stopping power at all. I have removed the front calipers since and cleaned them and gave them a rub with sandpaper but still no better. Three brake companies I spoke to didn't seem surprised that the brakes don't work too good after changing all four brakes, but can only advise me to keep beeding them in. (brake accelerate brake etc).

If they don't come good by the weekend I'll change the pads again for a different brand and see what happens. However, is there any way of telling whether the master cylinder is applying the correct pressure to the wheels? There is no air in the hydraulic line because they don't actually pump up harder when pumping the pedal.

Has anyone else experienced this sort of problem when changing all for wheels at the same time?

[Brett_jjj]

They can take time to bed in.Id have thought they would have bedded in by now though after that amount of k's..Try to do some heavy stops from around 70 km/h.Dont come to a complete stop though,keep the car moving.Do this a few times in succession or until you can smell the pads getting hot.Then drive slowly(40k's),trying not to brake until they have had a chance to cool right down again.They should start to come good after this.

[kswenson]

Thanks Brett. I have just been out on a quiet road again and tried bedding them in. The road was wet and i'm starting to get one front wheel trying to lock up and there's a slight improvement. I would have thought the back wheels would have locked up at some stage, but that hasn't happenned yet. When I got back home I could smell all the brakes on all four wheels, so they are working. I'll let them cool down and go out on the road again to see if there's an improvement. I didn't think it would take this long. The reason I asked about the master cylinder is because I bought the car new in 1993 so I know the master cylinder is original. Is there any advantage in changing the brake fluid perhaps?

[RX25SE]

Did you clean the protective coating from the discs? With a non mineral based cleaner?

It is not uncommon to have poor braking when replacing all rotors and pads. After 200+km they should be near OK.

Did the brakes feel OK before the job? Chances are the hydraulic/booster systems are fine.

TBH Im not a fan of Bendix.
It would be interesting to see if a pad change solves the problem.

[kswenson]

Yeah, I cleaned them all down with CRC brake cleaner. I know I did everything right, I'm just concerned about how long it's taking to get decent brakes. I did notice that the Bendix Stealth pads have large bevelled edges at both ends and in the middle, which is obviously their solution for quiet brakes. However, the pads I pulled out (which have now gone in the rubbish) had a lot more flat surface against the disc. Maybe getting another brand of pads is the solution. After this I think my opinion of Bendix is going to be reduced somewhat. Before I did the brake change the brakes were OK, just that the pads were worn. The rotors weren't too bad, but I decided to renew the lot just bring it all back to new.

[James39]

Perhaps giving the brake system a flush and a bleed will help matters?

[delcowizzid]

depends on the pads a lot i allways used to run metal kings in all my cars bad in town had to push the pedal hard but when in the windy stuff hard on the brakes and getting heat in they are great opposite goes for the cheapo pads i run now good when cold bad when hot

[kswenson]

Hi James. I really don't think the hydraulic side of it is the problem, but it's something to consider. The fluid was last changed about 8 years ago, so it wouldn't do any harm. Thanks for your help.

[kswenson]

If I decide to change the pads for a different kind, what would you suggest. About 80% of my driving is at 100ks and 20% suburban traffic. I don't care what they cost, just so long as I can have good stopping power when needed. They are standard rotors.

[tezza]

Whats your brake pedal travel like?
Cant hurt to change the brake fluid especially if it 8 years old.

[kswenson]

The pedal goes about 3/4s of the way down. There's no soft feel at all. The pedal just feels loose until it gets firm them I have to apply pressure. A lot more pressure than my wife's VT.

[James39]

It took a run from Newcastle to Sydney and back to bed my pads in. Next pad change I am going to get the brake system pressure flushed.
The brake system on a VT would be more responive than a VR.

[delcowizzid]

The pedal goes about 3/4s of the way down.

probably just needs a bleed by the sound of that may as well just fill it with new fluid and keep bleeding till its clean fluid coming out the bleeders while your at it

[kswenson]

Hi again James. There's no doubt the VT brakes are far more superior than VR-VS. There's no comparison really. I never thought it would take this long to get the brakes to bed in. Driving to work and back the last two days has been a worry because if the car in front stops suddenly i'm not gonna have a chance of pulling up in time. It is a worry. I suppose if you just do fronts or rears at a time you you don't notice it so much. I will just take it easy driving to work for the rest of the week and try and bed them in, and if there's no improvement I'll try a different brand of pad. (God, I hope the road's aren't wet!). I'll look at changing the fluid as well. Certainly can't do any harm, though I don't know if there's any difference in stopping power.

[kswenson]

Thanks delcowizid. I think that's the way I'll do it. Though I assume I will have to bleed all four calipers so all the fluid in each line gets pumped out.

[delcowizzid]

yip start at passenger rear bleeder the drivers rear then passenger front then drivers front

[kswenson]

Thanks mate. What you are describing is oviously the furthest from the master cylinder first. Makes perfect sense. Thanks for the advise. I'll do it on the weekend. Thanks again.

[RX25SE]

As above, flush the fluid as this should be done every two years. Im not sure how much this will help your problem though.

The VT brakes would feel better as they have a double diaphram booster to allow for the larger bore master cylinder.

May be worth giving the pads one more good scuffing and reinstall them. If you have no luck with that, replace them.

[Brett_jjj]

If the brake fliud is that old,then definitely change it,otherwise you will end up with seized calipers.My VS had seized up rear calipers when I first bought it.The brake fluid had not been changed for years.Four new calipers later,and I now change the brake fluid every 12 months.Also if your brake pedal "feel" is firm when its pressed,and not going to far down near the floor when the cars running,then the problem will not be to do with the fluid,but more to do with the pads.Id give it another 100k's (after changing that fluid) with some more heavy stopping.If theres no difference after that,then Id look at fitting some different brand pads.

[tezza]

Whats the pedal travel like on a normal Commodore with standard discs etc?
Ive just gone through a similar excercise changing all four brake pads and two new front rotors.

I seem to have a longer pedal travel than my other car, although I cant really compare the two because of differing brake systems etc.

[Brett_jjj]

The brake pedal travel should be short and firm when new pads fitted..Thats going on how my VS (non ABS) is when new pads are fitted.The pedal travel gradually gets longer as the pads wear down.Thats how I find mine anyway,mine is all standard VS brakes by the way..

[BlackVXGTS]

If your brake fluid is really eight years old (which if true, is nothing short of disgraceful not to mention unsafe) it will have absorbed a lot of water vapour which decreases the boiling point of the fluid. When the fluid gets hot it feels like you have a very hard pedal but you don't get any increase in braking effort no matter how hard you push the pedal. A brake pedal that goes 3/4 of the way down is completely unsatisfactory and indicates that you have a lot of air in the system. As other posts have indicated, you need to replace the brake fluid and bleed the brakes ASAP. Perhaps you should also be looking at all the other items that should have been regularly maintained on your car over the last eight years but are still outstanding.

[tezza]

From no pressure, to full firm pedal, the travel is about I'd guess half or so. No air in the lines as pu,[ing makes no difference, although I put two different sets of pads in the front and rear so I wonder if this has any effect.

[pjdm1980]

I was under the impression that new style pads didn't need to be bedded in as they are treated at the factory, I've always used Bendix (had different grades of pads as well) and had no issues i get good stopping power and they last a long time, not much brake dust and pretty quiet excluding the Street Road Track pads they squeal a bit when they are cold.

[Brett_jjj]

Id say theres air in the lines somewhere if the pedal travel is long.. rebleed them.Start at the furthermost wheel from the master cylinder.Usually the left rear wheel. Then the right rear wheel and so on.Get someone to keep the master cylinder topped up,as it can suck more air in if the brake fluid level gets below half way at any time during the bleeding process.3 people are ideal.One to top up the master cylinder,one to pump the brake pedal,and yourself doing the bleeding.And there a couple of ways to bleed the brakes.You can just pump and hold the pedal,and then release the bleeder nipple,but the best way Ive found is to get a clear piece of tube about a foot long, that will fit tightly over the bleeder nipple,then get a glass jar,put about an inch of clean fluid into the jar,loosen the bleeder nipple a tiny bit,attach the tube to the bleeder nipple, and immerse the other end of the tube into the fluid in the jar,so that it creates an airlock.Then slowly pump the brakes until all the air bubbles are gone from the clear tube and also until its just clean new fluid coming through.Make sure you tighten up the bleeder nipple a bit before removing the tube from the bleeder.Otherwise it will just end up with air back in the system .