warped disc's - maybe not such a myth

[Spen]

Hey all,

 

Well I bought my 2005 350z GT back in november from a nissan dealer and have 2 years extended warranty on it.

 

When viewing the car the salesman was telling me how it has "upgraded" brembo brakes on that were fitted by the previous owner, obviously the GT models have brembos anyway but then I realised he meant the discs have been swapped for some grooved one's although I'm unsure of the make.

 

You can see them here:

 

I noticed some vibration when braking from over 40 mph but he assured me they were new and he kept telling me to take it easy with them for a while.

 

I don't really do any long journeys but the odd time I've took the car out for a run I've really noticed this juddering and so this weekend I had the front wheel off and noticed when turning the disc by hand there's an area where the pad looks like it touches the disc where as the rest of the rotation there is about a 1mm gap between the pad.

 

So in other words theiy are pretty badly warped!

 

 

 

Now as far as I'm concerned it's been like this since I bought it from them and so I would think they would swap the discs for me under warranty. Does that sound fair enough to you???

 

 

Obviously I won't know until I ring them but I'll keep you posted on the service I recieve and the outcome.

 

 

I was just quite shocked as a lot of people will say its very rare for discs these days to warp. But there are so many people that you see on the roads who will brake heavly from say 70mph upto a roundabout or sliproad and then sit there with their foot on the brake!

[DavidS14]

I'd check the disc mating surfaces with the hub to make sure everything is clean and free from surface contamination as a first step.

 

It could be DTV but 1mm sounds like a lot, is there any surface discolouration on the swept area of the disc cant really tell from the pic ?

 

Are the grooves in pairs and not all evenly spaced again can't really tell from the pic ?

 

I don't normally like too many grooves as the testing we did on the dynos showed that there were diminishing returns after about 8.

[Stew]

Probably the £50 discs off ebay!

[bernmc]

The dealer was talking tat - new discs should not judder - but he's probably achieved his aim of getting you out of the showroom with a problem car, and 5 months down the line where he can claim the problem is due to you. Discs wont be covered by warranty as they are wear & tear items. So you'll be relying on their 'goodwill' and desire to keep you as a customer - something that is not a strong point of UK Nissan Dealerships .

 

It may be worth having a go at 'scrubbing' the discs with a session of hard braking. Find a clear road, do a few stops of 4 seconds at 50% max brake pressure, starting from 30mph to gradually build up heat, and finishing with 3 to four 70mph stops. Stop on a level area and have a quick look (don't put the handbrake on) - the discs should be blue if you've done it right. Don't worry about the smoke . Drive a few miles gently to let things cool down.

 

That should sort out any deposits on the disc surface. If it's still juddering, then it may well be the disc. 1mm does sound like a huge amount - it's possible that the discs weren't installed properly - a bit of grime or rust on the hub surface etc may have meant the disc does not sit true....

[Spen]

Wow, thanks for the replys!

 

 

The grooves are evenly spaced but they are quite large grooves compared to most discs I've seen. Here's another picture:

 

 

There isn't a deep groove around the edge of the disc and the surface colour seems ok and there didn't seem to be too much rubbish on them/around the caliper or in the vented part of the disc. They looked very clean. The only thing I would say is they seem to have very slight ridges/scratches when I ran my finger down them. You can just about see them in that picture ^.

 

I didn't actually take the disc off to inspect the rear where it mates to the hub but thats something to consider if I dont get anywhere with the stealers.

 

 

I did try "scrubbing" the discs with some hard braking a couple of months after buying the car and at first I thought it had made it better but then found it was actually just as bad.

It causes the steering wheel to actually shake.

 

 

I suppose its bad on my part because I should have taken the car back as soon as I could but I just thought I would see if they settled down. I only really use the car for short journeys most of the time on roads that are only 30-40mph anyway and it is only noticeable over 40 so I never really thought too much of it.

[M13KYF]

try a brake pad bedding in procedure. A member last week was having similar problems and this rectified his vibration.

[DavidS14]

If you can see by eye that the disc is not running true then I would check it's fit to the hub before any thing else.

 

If it's all fitted correctly and it's still vibrating then there are a few causes but making sure the pads are properly bedded in

is a good first step. That should remove the top layer of pad material and condition the new pad surface (i.e carbonise the

binders) and insure full pad/disc contact.

 

That's why I asked about the disc surface as if new discs are fitted with old pads or new pads are not correctly bedded

you can have problems as you will not get full contact between the pad and the disc. This can lead to hot spotting/banding

which can cause surface deposits and DTV (disk thickness variation) as the structure of the disc surface can change in

these hot spots causing them to become harder than the surrounding material (usually by the formation of martensite).

These hard areas wear down more slowly than the surrounding material so you end up with some areas of the disc that

are thicker than others which can lead to vibration when the brakes are applied.

 

This problem can also be caused if the callipers are not releasing fully and so you have a pad(s) dragging on the disc

all the time which again can lead to hot spotting/banding even though it might only be a light contact.

 

There are other issues as well like the stiffness of the pad material and it's ability to conform to the disc surface but

that get a bit involved

 

If the discs are newish when this happens a quick fix is to have them lightly skimmed which will remove the thin areas

of martensite and true the disc up again, you can then fit new pads and bed them in correctly. The good thing about this

is that using your original discs they have already been thermally cycled when originally on the car so should be more stable

(structure wise) than new discs. We used to do this all the time on the dynos when we were developing pad materials.

 

The grooves are there to "sweep" the pad surface clean and also to dissipate gas build up at the pad surface during

high temperature applications.

 

Sorry to waffle on but I'm bored

[Spen]

Thanks for the informative post David, very useful info!.

 

 

I had been a little busy with work after my first post on here so only got round to ringing the dealers (Sunwin Nissan Derby) yesterday morning and this is kind of how it went:

 

I call the service department and explain the problem and I'm told that the salesman who told me they needed to settle down etc etc has now left. The chap then tells me I would need to speak to the sales manager and he would get him to ring me when he gets in this morning (saturday)

 

I waited for a bit but he didn't call so I rang him..he hadn't had the message to call me.

He told me they are going to obviously have to look at the car first before anything else..fair enough fairly obvious so why I couldnt have booked it in yesterday I do not know??? The sales manager left it that the guy in services (not the same guy I spoke to on Friday) will ring me this morning to book the car in. (he wouldn't put me through because the service department is "too busy" because of the bank holiday.

 

I waited and had no call so called back and the person at the other end just picked up the phone then hung up instantly so I left it a good hour and half

 

 

Well the guy in services didnt ring me back and the time was getting on and I know service is only open until mid day on a saturday so I call services direct. Start explaining the situation to him and that I need to book the car in. before I could say any more he says "hold on a min" and puts me back through to the sales manager...... His excuse was that they are just way too busy this morning and he will get him to ring me on Tuesday......right......

 

 

 

 

This is my first experience with a dealer as I've always had older cars and done the work myself and so far I'm not impressed at all!

[Maccaman]

It's all well & good them treating customers like this now while they are busy. Don't they realise, that before long business will drop off, due to them not selling the same numbers of new cars? When the servicing numbers are lower they will probably just blame it on the "global credit crunch". Hopefully the dealers who treat their customers properly will benefit in these times.

[M13KYF]

shocking service. I would ask to speak to the manager of the dealership and make a complaint

[Spen]

Just some more info on this if anyones interested!

 

I couldn't get the car booked in for a couple of weeks but finally did for this weekend. (they were fully booked until now)

 

Dropped the car off this saturday to be looked at today (Monday). Waited for the dreaded call after they'd looked at it and have not long come off the phone to them.

 

 

Apparantly the discs are warped (as I already knew) and to replace the discs and pads it's a £600 job

 

The manager said he was willing to go halves with me on it - what a joke since its probably just slightly over an hours labour lets say 2 and parts will probably only set them back 200 so clearly If I were to "go halves" I'm paying full wack anyway.

 

Typically the guy I was speaking to wasn't the manager. He's just the guy on the service desk and when I started going into the fact I bought the car putting my trust in the salesman who said the brakes would settle down he said he understood me and would need to have a chat with the manager again and get him to ring me.

 

 

 

The other laugh was when he said I had done 10,000 miles since buying it in november (I bought it with 49k on the clocks) and apparently the techinican has wrote down the mileage as 57K instead of 51.5k which it actually is......

 

 

Now I'm playing the waiting game again and I think all I'm going to get is "well we're doing you a favour since brakes aren't usually covered under warranty etc etc". If they've not rang me in a couple of hours I'll be ringing them back again as I'm without a car now.

 

I'm not settling for it anyway and I will fight it to the point of threatening to report them to trading standards if needs be. Sunwin is really quite big and owned by the co-op and so far the service I've recieved from them is really shoddy as you can see.

 

 

wish me luck