Measuring brake disc run-out

Veloce

Does anyone know of any garages in the Dublin area that have the necessary equipment to measure brake disc run-out / disc true-ness to the hub? I believe a sort of dial is needed to measure this?

mickdw

Veloce wrote: »

Does anyone know of any garages in the Dublin area that have the necessary equipment to measure brake disc run-out / disc true-ness to the hub? I believe a sort of dial is needed to measure this?

Surely any garage could do this.
I bought a gauge myself and cobled together bolts with washers etc to secure the disc tightly in place as if the wheel was fitted. Great bit of kit for sanity testing if nothing else.

mickdw

Veloce wrote: »

Does anyone know of any garages in the Dublin area that have the necessary equipment to measure brake disc run-out / disc true-ness to the hub? I believe a sort of dial is needed to measure this?

Surely any garage could do this.
I bought a gauge myself and cobled together bolts with washers etc to secure the disc tightly in place as if the wheel was fitted. Great bit of kit for sanity testing if nothing else.

Mech1

Just replace the discs if you have a problem. very cheap nowadays for most cars. no garage will have the time to check and report runout and then give you the car back with no repairs done if runout is within specs.

what make / model?

What symptoms?

my3cents

All you need is a dial gauge and a stand to hold it secure http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dial+gauge gives you an idea of cost.

Wheelnut

I think what you are looking for is a dial gauge, however you can measure it yourself without any special equipment. Remove the wheel and find an implement with a point such as a pencil. Support the pencil against something solid like the calliper with the point against the disc. Now rotate the disc. If the disc is warped it will push back the pencil at one point and a half turn later there will be a gap between the disc and the pencil. You can measure the gap with a feeler gauge if you wish, but it's a bit academic. If the disc is warped it's warped and needs to be replaced.

Veloce

It's a Nissan 350z.

I fitted new rotors myself less than 700-800 miles ago and I've developed the following issues within that timeframe (bearing in mind I replaced as a result of similar symptoms as below:

High speed braking: pulsation felt through the brake pedal
Slow speed braking: 'Wavy' or kangeroo effect when slowing down, like the disc is not completely parallel. Very noticeable.

Inspection last night - I jacked up the car and rotated the front wheel. The wheel rotates freely without resistance for about 75% of a complete turn. The final 25% of the turn the disc is catching / rubbing off the caliper and as a result the disc becomes more difficult to rotate for that portion of the turn. Would this indicate a warp?

As the discs are so new I am thinking down the line of having them skimmed for a start.

CJhaughey

Veloce wrote: »

It's a Nissan 350z.

I fitted new rotors myself less than 700-800 miles ago and I've developed the following issues within that timeframe (bearing in mind I replaced as a result of similar symptoms as below:

High speed braking: pulsation felt through the brake pedal
Slow speed braking: 'Wavy' or kangeroo effect when slowing down, like the disc is not completely parallel. Very noticeable.

Inspection last night - I jacked up the car and rotated the front wheel. The wheel rotates freely without resistance for about 75% of a complete turn. The final 25% of the turn the disc is catching / rubbing off the caliper and as a result the disc becomes more difficult to rotate for that portion of the turn. Would this indicate a warp?

As the discs are so new I am thinking down the line of having them skimmed for a start.

Start with the basics, are you absolutely sure the discs are mounted flush with the hub, no rust or anything else between the inner face and the hub?
Is the Hub true with no runout?
If you have already had this problem with previous discs it may be the hub thats the issue.
Is it both sides or just one?

Veloce

CJhaughey wrote: »

Start with the basics, are you absolutely sure the discs are mounted flush with the hub, no rust or anything else between the inner face and the hub?
Is the Hub true with no runout?
If you have already had this problem with previous discs it may be the hub thats the issue.
Is it both sides or just one?

1) I cleaned as much as I could from the hub flange prior to fitting the new disc.
2) The hub run-out I did not check. I used the caliper as a runout tool when the new discs were fitted - the discs rotated freely through 100% of the rotation at the time of fitting
3) It appears to be on both sides, but the driver's side being more affected. I can only feel one single repeated pulse through the pedal at high speed braking

challengemaster

Did you bed in the brakes properly?

Any signs of a sticky caliper?

CJhaughey

Are you checking with the wheel on or off?
If the disc is running into the pads then its either warped or mounted incorrectly /not perpendicular to the hub.
What does the disc surface look like at the point where it rubs?

Veloce

challengemaster wrote: »

Did you bed in the brakes properly?

Any signs of a sticky caliper?

I can't say whether I bedded them in properly or not. I took it for a spirited drive once fitted and they were working perfectly with no noticeable wobble.

Sticky caliper is another avenue I should probably investigate, as I said both discs rotated freely when new pads fitted. Can't feel any stickyness when driving.

Veloce

CJhaughey wrote: »

Are you checking with the wheel on or off?
If the disc is running into the pads then its either warped or mounted incorrectly /not perpendicular to the hub.
What does the disc surface look like at the point where it rubs?

I checked with the wheel both on and off and even adjusted the torque of the bolts in the affected area to see if that could have been the cause.

The disc surface looks slightly more shiney in the affected / rubbing area. Therefore, if it the disc is not correctly fitted to the hub then I will most likely have a flat / lower spot which would mean replacing the disc. Or if the disc is warped then effectively I have a 'high spot'.

CJhaughey

Veloce wrote: »

I checked with the wheel both on and off and even adjusted the torque of the bolts in the affected area to see if that could have been the cause.

The disc surface looks slightly more shiney in the affected / rubbing area. Therefore, if it the disc is not correctly fitted to the hub then I will most likely have a flat / lower spot which would mean replacing the disc. Or if the disc is warped then effectively I have a 'high spot'.

Its a high spot if the disc is only rubbing in one spot.
Try taking them off and swapping them over to the other side.
What pads did you get with the new discs?

Veloce

CJhaughey wrote: »

Its a high spot if the disc is only rubbing in one spot.
Try taking them off and swapping them over to the other side.
What pads did you get with the new discs?

Pads were only about 50% worn so I retained existing ones. Probably should have changed them regardless or does that make a difference?

If a high spot will skimming the disc work?

CJhaughey

Veloce wrote: »

Pads were only about 50% worn so I retained existing ones. Probably should have changed them regardless or does that make a difference?

If a high spot will skimming the disc work?

More than likely its the pads causing the issue.
Always replace pads when you replace discs.
I'd get some new pads and while fitting them check the sliders are OK.
Brembo pads are good.

Veloce

Thanks for the replies. She's going in to the garage on monday. I'll keep ye posted.

PADRAIC.M

Who fits new discs without checking run out? And also I have seen some new discs warp from driving them too hard on the bedding in process, some people this to bed them in properly you need to roast them with hard braking! Crazy!

challengemaster

PADRAIC.M wrote: »

Who fits new discs without checking run out? And also I have seen some new discs warp from driving them too hard on the bedding in process, some people this to bed them in properly you need to roast them with hard braking! Crazy!

Depends on the discs and the application. Some manufacturers recommend a specific bedding in process.

jimgoose

CJhaughey wrote: »

More than likely its the pads causing the issue.
Always replace pads when you replace discs.
I'd get some new pads and while fitting them check the sliders are OK.
Brembo pads are good.

This. And avoid "pad imprinting", a major contributor to the disc-deforming problem, by not holding the brakes on hard after coming to a stop from speed. The heat and pressure of modern hydraulics causes pad material to transfer to the rotor. In this situation I always pull the handbrake and use the service brake pedal just enough to activate the brake lights.

Veloce

Update: discs have been skimmed. The drivers side was the particular offender but both discs affected as suspected.

Embedded is a video of the drivers side, there is still slight resistance in rotating the wheel but very minor. Listen to the pads catching on the wheel on a single point each rotation (ignore my hand slipping off!) This can not be felt under braking though and the resistance is fairly minor when rotating the wheel by hand. Is this acceptable?

Other video [ill post up later] is a close shot of the passenger side disc surface after skimming. I noticed quite a number of lines from skimmed high spots. This must be the poor pad transfer to the disc being scraped off, what do you think guys? I have new pads on the way to be fitted.

challengemaster

How much did it cost to get it skimmed?

Veloce

25 quid per disc

Veloce

Disc surface after skimming:


http://youtu.be/nkAbwm-I8Pc

visual

Skimming discs when new discs are so cheap and will last much longer.:(

challengemaster

visual wrote: »

Skimming discs when new discs are so cheap and will last much longer.:(

Read the thread. Less than 800 miles on the discs.

Usually I'd say the same tbh, but they're practically new discs.

Veloce

visual wrote: »

Skimming discs when new discs are so cheap and will last much longer.:(

Have you priced 324mm discs for a 350z? They are not cheap. If skimming doesn't work then I'll replace