Front brake pads & discs change info + fitment

[Speedbird]

I am looking to change my front brake discs and pads on my 184 TDI FR ST soon.

I have done a quick search and couldn't find anything, does anyone have a guide or a link to a manual, including bolt torque settings?

I have found this helpful video on youtube, but it is all in a foreign language, so of limited use:

In the video, one of the pads has an electric cable that he removes and discards. I assume this is a brake pad wear indicator, which is an option? Does anyone know for definite which cars this is fitted to?

Also, on Euro car parts, there seems to be 2 disc size options, 288mm or 312mm. Does anyone know the correct item for a 184 FR estate front brakes?

Thanks in advance.

 

[Nojbik]

The 184TDI has the bigger 312mm brakes, but unfortunately I can't help you with those torques, maybe try checking your service manual.

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[RUM4MO]

There is or was a link to a genuine workshop manual for this model of Leon, I grabbed that years ago, very handy to have for lots of tasks.

Edit:- look in the guides section for this model of Leon - the title of the thread is something like “link to workshop manual”.

Page 2 for the thread and page 1 in that thread for link to manual.

 

[Speedbird]

There is or was a link to a genuine workshop manual for this model of Leon, I grabbed that years ago, very handy to have for lots of tasks.

Edit:- look in the guides section for this model of Leon - the title of the thread is something like “link to workshop manual”.

Page 2 for the thread and page 1 in that thread for link to manual.

Edit: Found it, thanks!

 

[SuperV8]

Some brake fitment tips:

• They are torque to yield caliper mounting bolts - so really should be replaced - i'm sure many wont replace caliper mounting bolts (even Seat/VW) so if your not going to at the very least put the bolts in by hand with your fingers, if you feel any tightness then you really should fit new bolts as the threads have been elongated.
• Brake discs are very accurately machined for a reason, spend time cleaning the wheel hub, it needs to be spotless - flicking a wire brush over it probably isn't good enough, use a wire brush in a drill (and eye protection!).
• You really should measure the installed disc run-out with a DTI - mounted securely, pointed about 10mm from the disc outer edge & bolting the disc to the hub evenly with wheel bolts & washers.
• Ideally installed disc runout should be less than 50 microns (0.05mm).
• If runout is high it WILL cause disc thickness variation (DTV) in a few hundred to a thousand miles where the high points of the disc rub the pads it will wear the disc thin which will cause brake judder and you'll need new discs.
• If runout is high look for the cause - wheel hub/bearing/new disc manufacturing issue? Clocking the disc - moving it around to the next holes, and then re-measuring can help reduce tolerance stack up.
• Don't use cheap pads.
• Pads need to be free to slide smoothly - any binding/stiffness of the piston/slider pins/pad in carrier needs to be resolved - otherwise your pads won't be free to release from the discs which can cause noise/performance/wear issues.
• Bedding in your brakes is important - Perform 10x 60mph-20mph stops at about 50% braking effort (100% being an ABS stop) Most importantly do NOT allow the brakes to come to a complete stop with your foot on the brake while preforming this bedding in sequence as you can get uneven friction material transfer - which can also cause judder)

 

[Speedbird]

Some brake fitment tips:

• They are torque to yield caliper mounting bolts - so really should be replaced - i'm sure many wont replace caliper mounting bolts (even Seat/VW) so if your not going to at the very least put the bolts in by hand with your fingers, if you feel any tightness then you really should fit new bolts as the threads have been elongated.
• Brake discs are very accurately machined for a reason, spend time cleaning the wheel hub, it needs to be spotless - flicking a wire brush over it probably isn't good enough, use a wire brush in a drill (and eye protection!).
• You really should measure the installed disc run-out with a DTI - mounted securely, pointed about 10mm from the disc outer edge & bolting the disc to the hub evenly with wheel bolts & washers.
• Ideally installed disc runout should be less than 50 microns (0.05mm).
• If runout is high it WILL cause disc thickness variation (DTV) in a few hundred to a thousand miles where the high points of the disc rub the pads it will wear the disc thin which will cause brake judder and you'll need new discs.
• If runout is high look for the cause - wheel hub/bearing/new disc manufacturing issue? Clocking the disc - moving it around to the next holes, and then re-measuring can help reduce tolerance stack up.
• Don't use cheap pads.
• Pads need to be free to slide smoothly - any binding/stiffness of the piston/slider pins/pad in carrier needs to be resolved - otherwise your pads won't be free to release from the discs which can cause noise/performance/wear issues.
• Bedding in your brakes is important - Perform 10x 60mph-20mph stops at about 50% braking effort (100% being an ABS stop) Most importantly do NOT allow the brakes to come to a complete stop with your foot on the brake while preforming this bedding in sequence as you can get uneven friction material transfer - which can also cause judder)

Can you please link to where it says they are TTY bolts? The Seat manual does not mention this, just to refit the bolts that are removed.

Also, unless the disc is on an engineers table and you run a DTI over it, I can't really see how you can accurately check a disc to within 0.05mm, especially with it fitted to a car. Digital calipers would be no good as you could only check the edges.

Thanks for the other tips though. I have changed brakes on cars before, and also serviced/stripped/rebuilt Typhoon carbon brake units. I just don't like doing things without a manual and all the torque settings to hand, OCD is a bitch

 

[SuperV8]

Can you please link to where it says they are TTY bolts? The Seat manual does not mention this, just to refit the bolts that are removed.

Also, unless the disc is on an engineers table and you run a DTI over it, I can't really see how you can accurately check a disc to within 0.05mm, especially with it fitted to a car. Digital calipers would be no good as you could only check the edges.

Thanks for the other tips though. I have changed brakes on cars before, and also serviced/stripped/rebuilt Typhoon carbon brake units. I just don't like doing things without a manual and all the torque settings to hand, OCD is a bitch

Example of measuring brake disc runout:
Its a simple check to ensure you won't need to replace your discs in a thousand miles due to judder.

Extract from Seat manual:
Number 10: Renew bolts! 200nm
The rear caliper bolts use a torque & angle 90nm+90deg. Manual says to renew both.

 

[RUM4MO]

Ooooh, I like the picture with the disc and DTI, some years ago I managed to get hold of 5 big nuts and washers to fix the discs to the hub properly when the wheel was off - to check for excessive run-out. Using nuts from a bigger thread size than the wheel bolts allows the spherical taper to tighten down into the lead-in of the nuts.

As well as being obvious that some calliper carrier fixing bolts should be replaced due to extra 30 or 90 degrees tightening after reaching the correct torque, these fixings have a serrated inner surface to assist with locking, that surface gets smoothed off quite a bit when removing these bolts, plus the tool bearing/contacting surfaces get subjected to lots of nasty stuff and so rust badly - I've always replaced these bolts when replacing discs even when the car maker considers it unnecessary a lot better than having a problem next time round due to excessive rusting on the fastener's heads.

 

[martin j.]

Are these stretch bolts only on the rear-as per diagram- op is changing fronts.

 

[Alzak]

Example of measuring brake disc runout:
Its a simple check to ensure you won't need to replace your discs in a thousand miles due to judder.
View attachment 24432

Extract from Seat manual:
Number 10: Renew bolts! 200nm
The rear caliper bolts use a torque & angle 90nm+90deg. Manual says to renew both.
View attachment 24431
View attachment 24433

I've changed 100s of discs and never checked disc runout... Not even mentioning iam yet to see garage checking this.

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[noidea]

It also says on step 8 to renew the guide pins. Does everyone change the bolts and pins at every brake job?

 

[RUM4MO]

Guide pins and in other designs of disc brakes, bolts that screw into retained guide pins, tend to be coated with blue Loctite so the easy statement to make is "replace" most home car fixers will just scrub them up to clean off the blue Loctite, maybe even run a die over them, and recoat with blue Loctite.

 

[Jay280]

This is a good informative how to video. On the bigger 340mm brakes like on the cupra but shouldn't be too much different other than size.

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[SuperV8]

It also says on step 8 to renew the guide pins. Does everyone change the bolts and pins at every brake job?

Number 8 - guide pins - is actually the guide pin bolts - and yes these should also be renewed, usually come with your pads.

 

[SuperV8]

I've changed 100s of discs and never checked disc runout... Not even mentioning iam yet to see garage checking this.

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Even cheap aftermarket brake discs are machined to less than 15microns in disc thickness variation DTV (R90 for brake discs has improved this)!, and most I measure are less than 8 microns thickness variation (0.008mm)! this is precision CNC machining and for a reason. I wouldn't fit these precision discs to a rusty old hub without a simple/quick runout measurement to ensure its within tolerance.

If you are fitting new discs to new hubs with new bearings then no you don't need to measure disc runout as this is accounted for during the brake system tolerancing design stage.

If you are fitting new discs to rusty hubs you have introduced an unknown - the rusty hub, and this is completely dependent on how well you clean it - a simple runout check can confirm you're good to go - or if you need to spend more time cleaning - or if something else is wrong and needs fixing.

I agree regarding garages - I also don't see enough garages using DTI's to check installed disc runout - and they ALWAYS blame the brake discs when they have to do the job again in 1000 miles due to the customer complaining of brake judder!

 

[BigJase88]

This is a good informative how to video. On the bigger 340mm brakes like on the cupra but shouldn't be too much different other than size.

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Not great

He hasn't cleaned and greased the slider pins, nor did he clean out where the pads were running in the carrier
Also why is he using a big set of grips to get the piston back in to the caliper? that's just asking for a damaged seal, please use a caliper rewind tool (required on rear calipers in the VAG range anyways so worth getting)

Also not sure he even used Copper Slip on the rear of the pads / where they go into the carriers.

 

[martin j.]

I was advised not to use Copa Slip on brakes now since it can affect the abs senso performance,, now just have a tube of dedicated brake grease, it was explained at the time but I didn’t really take it in, I just nodded and agreed.

 

[BigJase88]

I was advised not to use Copa Slip on brakes now since it can affect the abs senso performance,, now just have a tube of dedicated brake grease, it was explained at the time but I didn’t really take it in, I just nodded and agreed.

Yeah i also heard that

I still use it and suffer no ill effects, whats the latest recommended product, is it not like a silver coloured grease?
I did attempt to find some at Halfrauds last year to replace my depleted cooper grease tub but couldn't find any alternative so just went with the old trusted copper grease again.

 

[martin j.]

I have a tube of brake grease I was given (freebie from a rep) and it’s a grey paste but I have seen other stuff that looks a red oxide colour.

 

[Johnny Leon]

Anyone know the part no. for the carrier bolts for FN III & 312mm - N90708504 M12x1.5x35 (also seen M14X1.5X55 quoted for same) ?