Question about disk brakes post track day

[jackb_ms]

Hello All

I was checking my car post track day when I noticed some discoloration on my front disk brakes.

I cannot feel any lip on the brakes and there is plenty of "meat" on the pads.

Is this discoloration normal? 

Did I "cook" something?

Jack

 

[SM25T]

That looks like you have worn a lot off the face of the disc, and you can see where each hollow is in the vented construction.

[7 wonders of the world]

can just be the variation in material and the associated heat build up on the finned sections - normal

If your unsure about disc wear pop a micrometer over the disc and measure its thickness, the min thickness will be stamped on the edge to the disc should still be visable

[7 wonders of the world]

Front vented discs 18mm new, 16.4mm min

[SM25T]

I suspect that may be the problem

[jackb_ms]

Thanks

I'll measure them later on this week.

What is the best / cost effective option to replaces the disk?

The pads have are barely worn, is it ok to re use them with new disk?

Jack

[garybee]

Hard to tell from that picture, does the pad contact the disc right to the edge?  It isn't that unusual for that to be the case with aftermarket calipers and if so you won't get a lip.  It's easy to miss how much a disc has worn if that is the case.

[SM25T]

You can use the pads with the new discs. Just go carefully at first while they bed in to the flatness of the new disc surface.

[Doctor]

Those discs are ready for replacement. Probably flirting with minimal thickness with the discolorations over the "air" chambers where the thickness reduced. 

[7 wonders of the world]

Igor,

Discolouration of that nature is normal after hard applications, once used normally this will disappear.

If worn below or very close to minimum, radially cracked or there's excessive variation then replacement is unnecessary.

Fine heat cracks in the surface are also common in high load applications

 

Regards reusing the pads, yes providing there's no contamination, uneven wear (wedge) or signs of delamination between friction material and backplate, they should be prepped by flatting them on 80 grit on a flat surface, sheet of glass for instance this abrades the surface, removes glaze and aids bedding in

[Doctor]

Yes father. Still wouldn't want them on my car. 

[7 wonders of the world]

 

[jackb_ms]

Cheers All

I've ordered a new set from Canley Classic.

Should be arriving tomorrow.

I assume the only way to get the bolt of is the old mix of brut force, heat and penetrating liquid?

Any other tips?

Jack

 

[SM25T]

If someone used loads of loctite thread sealant on the disc bolts you might need to apply heat the the hub by the bolts to soften it. Put the studs of the hub into a wheel that is laying on the floor and grip the wheel with your knees while using a long bar for leverage on the socket, or a good impact wrench. Preferably with hexagon socket, not 12 point

[dikko]

Keeping the brakes on after a few hot laps may tend to do that however thick the discs. Easily done in the excitement of it all.

Back in the paddock keep off the brakes.   

[aerobod - near CYYC]

I'm not sure on the protocols at tracks in the UK these days, but here in Canada they will flag the session as over and you then have a full cool-down lap before coming in. During that lap no passing is allowed, the aim is to complete the whole lap without touching the brakes at all, so easing off to take the slowest corners at 50-60km/h and cruising along at 100 to 120km/h around the rest of the track. The brakes are usually down to normal road temperatures after 3km of no brake usage on the tracks I go to.

[jackb_ms]

On the track I was careful to take a "slow" lap before going for a rest.

The lap at Abingdon is short, so maybe I didn't allow enough time for them to cool down enough.

I knew not to put the handbrake on

It was my first proper track day, all part of the learning curve

Jack

[JonT]

On sessioned days a cool down lap would be normal after the chequered flag - on an open pit lane day, it's up to you (it's certainly something I try and do, but you need to be even more attentive to mirrors!). The difficultly can be a red flag, particularly if it's near the end of the lap - but there's nothing you can do about it, other than maybe drive slowly down the track access roads? 

[jackb_ms]

I've received the disk and the near side was done within 1/2 hours not issue at all.

But the off side is much more problematic. It's not the four bolts holding the disk on it's the vertical link which is not moving.

Anyone around OXford has a press?

Jack

[OldAndrewE]

What are you trying to do with the vertical link?  Are you not undoing the wheel bearing and pulling the hub off the stub axle?

[7 wonders of the world]

Caliper bolts out, support caliper.

Hub nut off, remover bub with disc,

Remove 4 bolts, knock the hub thro the old disc

The upright and stub axle remain on the car

[jackb_ms]

Note quite all sorted.

I managed to kick the tray where I had all the nut and bolts.

I found most of them apart from one nut from the track rod end.

Does someone know what size it is so I can get one localy?

Cheers

Jack

[OldAndrewE]

Probably M10 but could be 3/8 UNF depending on which track rod ends are fitted

[andy_harries]

"I managed to kick the tray where I had all the nut and bolts."

Sounds like the kind of thing I do.  Turn a simple job in to a longer one through clumsiness!