Brake pedal travel after pad change

nevetsg · 01-09-2016, 04:37 PM

Hello

Last week we had dropped the MC off at a local mechanic to have the Front brakes and fluid change. They machined the rotors and changed the pads/fluid.

When we got the car back the brake peddle feel has gone from just needing a light touch and you are stopped. To now I have to push it nearly to the floor. If I pump it it comes up but is down again the next time I stop. After a week of seeing if it just needed to bed in it is still the same.

We took it back to the shop today and they re-bled the fluid and took it for a test drive. As far as they are concerned it is fine... I mean, it does stop. it just feels like I am stopping my old Kombi...

So, can anyone think of what the issue may be? I feel that I am about to waste a Saturday tinkering under my car.

cobrin · 01-09-2016, 06:18 PM

Worst case scenario, (no leaks either) it's possible their technique in bleeding or retracting the piston may have caused it, or hard to believe but the flexible brake lines are soft/stretched from a hanging the caliper (again far fetched).

did they do the whole system bleed or just the fronts?

what pads were used? some just don't bite like OE and can explain it

.:4:. · 01-09-2016, 06:50 PM

It doesn't sound right to me. Old brakes stopped, new ones don't. Did they say anything about bedding the new pads? I had a crappy Mitsubishi van as a work car a while ago, and it didn't stop on a good day, but on every round of brakes I was told to take it easy for the first 100 kilometres to bed them in. Most times it happened reasonably quick from absolutely no stopping power, back to regular terrible brakes (I challenge anyone to tell me about an express van with good brakes). One set took almost 500 kilometers before the van stopped actively trying to kill me. Most cars have predominantly front brake bias, so if the fronts don't do the job, the rears don't really pick up the work load.

allanv6gt · 01-09-2016, 09:07 PM

Mondeos have rear brake first (i'm told by my mechanic). But bedding in new pads sounds good advice. Tho almost to floor does sound very suspect.

rondeo · 01-09-2016, 09:25 PM

If the discs were not machined true to the face another possibility is excessive runout pushing the pads and piston back. This could result in a fast long travel on first pressing the pedal. The pedal could then be pumped up. To test this theory you could see if the same thing happens re pedal travel in Park (with the engine running). Or check the runout with a dial gauge.

cobrin · 01-09-2016, 09:47 PM

disc runout would be felt in the pedal and in severe cases the steering wheel, in some cases with particular brake pad material it can show signs of variable braking similar to pulsing in braking when even foot pressure is applied. Close to that of a pad slipping across a hard hot spot and gripping on a normal surface.

I'll wait till nevetsg comes back with pad make. Bendix General CT are great for low dust but require far more input that the dusty softer Euro spec pad and I only did the rears.

I think I got hung up on the mechanical side of things than actual symptom - Increased input. Not surprising given a pad change.

nevetsg · 01-09-2016, 10:23 PM

Thanks for the responses.

I am a bit vague because my wife got it done whilst I was at work.

We don't know the brand of pads. Or the new fluid. Could it be that they have just used the brake fluid in stock and not the special spec stuff?

Don't think they re-bled the rears today. Just the fronts.

The brakes definitely work. It just feels like a 30y/o car now.

rondeo · 02-09-2016, 09:13 AM

Quote:

Originally Posted by cobrin

disc runout would be felt in the pedal and in severe cases the steering wheel, in some cases with particular brake pad material it can show signs of variable braking similar to pulsing in braking when even foot pressure is applied. Close to that of a pad slipping across a hard hot spot and gripping on a normal surface.

I'll wait till nevetsg comes back with pad make. Bendix General CT are great for low dust but require far more input that the dusty softer Euro spec pad and I only did the rears.

I think I got hung up on the mechanical side of things than actual symptom - Increased input. Not surprising given a pad change.

Not necessarily. The sliding caliper is designed to allow for variation in disc position, which is what runout is. Another cause is play in the wheel bearing.

Variation in disc thickness is another situation.

Apart from comparatively poor friction performance the Op was concerned about excessive initial travel, runout is one possible cause, along with unbedded pads, brake master cylinder, air in the system etc etc. Since excessive travel suddenly appeared after removal and machining of discs it seems reasonable to suspect as a possible cause.

Poor friction caused by pads would be grease, being a different composition or not bedded in ie not completely in contact.

cobrin · 02-09-2016, 10:01 AM

Quote:

Originally Posted by rondeo

The sliding caliper is designed to allow for variation in disc position, which is what runout is. Another cause is play in the wheel bearing.

Variation in disc thickness is another situation.

Apart from comparatively poor friction performance the Op was concerned about excessive initial travel, runout is one possible cause, along with unbedded pads, brake master cylinder, air in the system etc etc. Since excessive travel suddenly appeared after removal and machining of discs it seems reasonable to suspect as a possible cause.

Poor friction caused by pads would be grease, being a different composition or not bedded in ie not completely in contact.

Of course the caliper allows for it, it allows for lots of things by design, it wouldn't be issue cause they've just been skimmed though. Same for the wheel bearing it'd be as noisy as and any sloppiness will be heard/felt.

The key here is needing more foot input, so either the pads are harder and material not having the same level of grip, needing more input which is resulting in further pedal travel or, air in the system still. That sounds more plausible than my initial thoughts.

rondeo · 02-09-2016, 12:44 PM

Quote:

Originally Posted by cobrin

Of course the caliper allows for it, it allows for lots of things by design, it wouldn't be issue cause they've just been skimmed though.

Not quite 100 percent of the time. Removal of the disc, its placement on the brake lathe, the condition of the lathe, the skill of the operator, the presence of swarf etc on the lathe face, the installation of the disc on the wheel hub, the condition or presence of swarf etc on the hub and disc surfaces are factors which come into play. If all else failed I'd be checking installed runout. Max: 0.1mm. Pulsing pedal or not.

NZ XR6 · 02-09-2016, 07:32 PM

I'm surprised that they machined the discs. The OE pads and discs wear at about the same rate, so you'd expect them to be replaced together.

It sounds to me like there is something badly wrong to cause poor stopping and excessive pedal travel. Typical aftermarket pads are unlikely to stop as well as the OE ones, but that doesn't explain the pedal travel.

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rondeo · 02-09-2016, 08:14 PM

That's my experience. I just replaced front pads and rotors. The rotors were at 26.2mm (min: 26mm) while the original factory pads were at 4mm (min 2mm). I used pads from Ford (motorcraft), which were cheaper than bendix and braking performance hasn't noticeably changed.

**aussiblue** · 02-09-2016, 08:36 PM

It's probably unlikely but check they haven't got the inner and outer pads mixed up; they'd have to be very stupid to do it, but I have seen it done on other cars and the result is compression of the retaining tabs on the pad causing an overly soft peddle.

nevetsg · 03-09-2016, 02:33 PM

Ok so I bought myself some fathersday jack stands and have the tires off.

The brand of the pads is Hi-Q.

I can't see anything like the pads being drawn away from the rotors. there is minimal movement between brake off and brake on. How do you tell the difference between inner and outer pads?

I can't see any evidence of fluid leakage.

I was going to take the caliper off but I don't have a #7 allan key (I'v got 6&8...). I did take the long spring clip off and it all got loose. Put it back on and everything was firm again.

I think I have hit the limit of my skillz.

Again, the brakes are working fine. They just feel worse.

rondeo · 03-09-2016, 03:32 PM

Hi-Q brake pads are ceramic and according to this:

http://www.sangsin.com.au/main/sub2/sub2-3.htm

they have that 'soft brake feeling' which I take to mean something like they don't grab. Maybe that's the difference.

**aussiblue** · 03-09-2016, 08:45 PM

It does appear ceramic pads have a softer feel that some driver prefer as the braking action then seems more progressive rather than "on" "off"..

See http://auto.howstuffworks.com/auto-p...under-foot.htm

Quote:

Ceramic and Kevlar-composite pads are softer and will feel as such while semi-metallics will feel a bit firmer [source: Consumer Reports]. As long as you have a consistent brake pedal, you're fine either way.

But to counter this http://brakeperformance.com/seven-brake-myths.php :

Quote:

MYTH: There are �Soft� and �Hard� Brake Pads

The average driver thinks of a �hard� brake pad as semi-metallic and a �soft� pad as typically an organic or ceramic. Both of types of friction materials can be the same in terms of compressibility. Calling one material soft and one hard is not accurate. Compressibility can influence pedal feel, but usually only when the brake pad is defective. What really influences pedal feel is the pad's coefficient of friction. Engineers measure compressibility as a quality control measurement and not as a performance measurement and it has very little to do with noise or rotor wear.

NZ XR6 · 04-09-2016, 07:21 AM

Hmm. Excuse me being blunt, but based on your posts and the link, I'd say they fitted **** brake pads. If you have the old ones, I'd expect that refitting them would restore the performance.

Many years ago, I foolishly believed the guy at the Repco parts counter when he told me how good Silverline pads were. At least they gave me a full refund when I took them back a couple of months later ...

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cobrin · 04-09-2016, 06:03 PM

Quote:

Originally Posted by rondeo

Hi-Q brake pads are ceramic and according to this:

http://www.sangsin.com.au/main/sub2/sub2-3.htm

they have that 'soft brake feeling' which I take to mean something like they don't grab. Maybe that's the difference.

I think that's it right there...

NZ XR6 · 04-09-2016, 06:31 PM

What is said in the link is BS. Here's a post about some German ATE pads that another member fitted:
https://r.tapatalk.com/shareLink?url...re_pid=5601175

Hi-Q (LOL) may be acceptable in their country of origin, but not as replacement pads in a Mondeo.

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nevetsg · 05-09-2016, 11:15 AM

Hi-Q made with pride in Korea.

I thank you all for your help!

SO I think we have come to the consensus that the pads are just different to what I am used to. My subconscious has adapted to the new breaking style anyway. What I have found with this 'soft feel' is that I can work it with the gear down changes and slow to a stop with very little brake pressure.

The wife still doesn't like it...

NZ XR6 · 05-09-2016, 12:12 PM

Just curious, how much were the Hi-Q pads?

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