Brake disc condition - front offside only

[Wolvesboy]

Hi All,
I noticed and was quite shocked at my front offside brake disc condition. The photo shows the inside of the disc and has obvious bits missing from the inside edge to the nearest drilled hole in a few places.
I also noticed that a few of the small bolts holding the bell(?) were missing as well. Is this dangerous as the disc is really tight to the bell still and the car was stopping like a train as usual. The near side is fine but I have not checked the disc thickness.
The diameter is 320mm and disc thickness is 28mm. There are no other marks or gouges and apart from the stated points. Any ideas where I should get replacements or should I just get the solid discs on offer at Racetech at the moment?
I have also included an image of my caliper as I'm not sure if this is an upgrade or not.

[MoonMonkey]

I got mine from Reyland Motorsports. You can get AP racing discs, or Reylands own. 322mm rotors are not available any more but 330mm (either 28 or 30mm) fit with no modification

[Supateg]

Reyland here also. Very good quality discs.
Just need a aluminium spacer to fit the 330's

[MoonMonkey]

Supateg said:

Just need a aluminium spacer to fit the 330's

Sorry, your right. I was thinking about the calliper clearance and forgot that you need the 4mm spacer under the calliper radial mounting

[FarmyardPants]

You should also check the vanes between the two disc surfaces, they can rust through and collapse under the clamping pressure of the caliper. The 330mm conversion is great!

[Wolvesboy]

Thanks for the quick replies replies. I will get onto Reylands as nothing better than recommendations!
Cheers.

[QBee]

My TVR expert won't fit drilled discs for exactly this reason.
He says he has seen too many explode under pressure, with the inevitable consequences of complete loss of braking.
He uses grooved ones for track cars.

Anyone else have any opinions or practical experience on this?

[RobXjcoupe]

Drilling weakens the rotor, it creates stress points when the rotor heats up and cools rapidly ie driving through a puddle after heavy braking. Tiny cracks will appear and then the rotor is useless and of course dangerous. Spot faced and or grooves is the best for fast road. Grooved do make a noise unlike a drilled disc but rather that than fractured rotors.

[QBee]

RobXjcoupe said:

Drilling weakens the rotor, it creates stress points when the rotor heats up and cools rapidly ie driving through a puddle after heavy braking. Tiny cracks will appear and then the rotor is useless and of course dangerous. Spot faced and or grooves is the best for fast road. Grooved do make a noise unlike a drilled disc but rather that than fractured rotors.

Good post, that is pretty much what my expert says, though I would add the word "some" at the start of the last sentence. Mine don't make a noise, but you do feel the grooves biting under heavy braking from high speed.

[RobXjcoupe]

I've found from my experience a 6 to 8 groove rotor with the grooves facing forward or rotating backwards seem to help the pads bite better and hence make a bit of noise as the iron gets hot. Run the grooves the other way and they are quiet. I've had 40 groove versions before and tbh I think so much of the face had been removed the braking seemed worse than a standard plain rotor. Just my experience and I'm not a track driver but love a bit of out braking up to roundabouts

[ukkid35]

Wolvesboy said:

Hi All,
I also noticed that a few of the small bolts holding the bell(?) were missing as well. Is this dangerous

Yes, that has to be dangerous.

I believe the mounting bolts should be replaced as a set, and the torque and tightening order is as critical as it is with a head gasket.

[Incognegro]

QBee said:

RobXjcoupe said:

Drilling weakens the rotor, it creates stress points when the rotor heats up and cools rapidly ie driving through a puddle after heavy braking. Tiny cracks will appear and then the rotor is useless and of course dangerous. Spot faced and or grooves is the best for fast road. Grooved do make a noise unlike a drilled disc but rather that than fractured rotors.

Good post, that is pretty much what my expert says, though I would add the word "some" at the start of the last sentence. Mine don't make a noise, but you do feel the grooves biting under heavy braking from high speed.

All spot on. Ive been using Reyland for a while now Martin is a top lad and my most recent 350mm discs (CP6600 callipers) came in a Pagid box (as they all did I think from memory).

To negate the vibe from the curved groves I had them done right through to off the edge thus keeping air pressure consistent. definite improvement in feel over the 304mm J hooked I had before (which in themselves were brilliant). One scary moment on emergency stop today the back got very light then a slight wiggle my rears are drilled at standard 306mm but using CL pads.

[Wolvesboy]

I'm getting some new rotors. Probably 330s with a 4 mm extension - grooved not drilled.
However, the more I think about the missing bolts, the more I wonder where they went. Or, if the previous owner just didn't replace them once taken off? The remaining bolts are very tight and I don't think they would have come undone too easily by themselves. Surely they would have rattled about if they had? The other side is complete. Odd?

[Incognegro]

Ooh my OCD would say get new bolts to keep all symmetrical (you don't want to be driving in a big circle lol). I know Reyland recommend always changing bolts when changing rotors? Also tightening to 16nmt

[gruffalo]

Wolvesboy said:

I'm getting some new rotors. Probably 330s with a 4 mm extension - grooved not drilled.
However, the more I think about the missing bolts, the more I wonder where they went. Or, if the previous owner just didn't replace them once taken off? The remaining bolts are very tight and I don't think they would have come undone too easily by themselves. Surely they would have rattled about if they had? The other side is complete. Odd?

I would just like to point out that you need a 2mm spacer not a 4mm spacer and yes do replace the bolts fixing the bell to the disc.

I used ap 330mm discs and experienced no vibrating at all, I use Pagid RS14 pads as a rule.

[MoonMonkey]

gruffalo said:

I would just like to point out that you need a 2mm spacer not a 4mm spacer and yes do replace the bolts fixing the bell to the disc

Hi Gruffalo, I don't understand why you recommend a 2mm spacer?

If the new discs are 330mm diameter, and the original discs are 322mm, the difference is 8mm. So the caliper radius has to move 4mm further out, or am I missing something?

[gruffalo]

MoonMonkey said:

gruffalo said:

I would just like to point out that you need a 2mm spacer not a 4mm spacer and yes do replace the bolts fixing the bell to the disc

Hi Gruffalo, I don't understand why you recommend a 2mm spacer?

If the new discs are 330mm diameter, and the original discs are 322mm, the difference is 8mm. So the caliper radius has to move 4mm further out, or am I missing something?

Sorry you are of course correct, for some reason I was thinking the originals were 326mm.

Sorry for confusing things.

[Incognegro]

Gruff Im going on your recommendation of the Pads but will need to get them in 55mm pad depth for the 6600 calliper so gonna find out if thats possible.

How was Snetts?

gruffalo said:

I would just like to point out that you need a 2mm spacer not a 4mm spacer and yes do replace the bolts fixing the bell to the disc.

I used ap 330mm discs and experienced no vibrating at all, I use Pagid RS14 pads as a rule.

[gruffalo]

Snetts was epic, car ran faultlessly all day and had some good runs with a Corvette, Lambo Aventador, GT40 and a couple of others, came away grinning and knackered.

Front tyres now a little second hand looking.