brake discs - Tar Ox any good?

[Guest]

I stupidly replaced my old worn OEM front discs with Zimmerman cross drilled items. After a couple of trackdays I'm getting a horrible judder through the steering wheel when braking hard after a couple of laps.
My extensive scientific research (running my finger over the surface of the disc when cold) showed that the disc surface does seem bumpy or contoured.

I'm guessing the cheap discs are the culprit and was thinking of trying the Tar Ox grooved discs. I'm not sure about cross drilled items as I've heard they do crack too (mine already have some small cracks)

Anybody any views on the Tar Ox discs?

I just want something that will last a year's road driving with about 6 trackdays.
There must a solution.

Please help

 

[Jamie Summers]

Kristian,
I'm also trying the Zimmerman cross-drilled on my car for the first time, and I'm getting the same juddering. The discs look in perfectly good shape to me so I'm pretty sure that the juddering is just being caused by a build up of pad material on the discs which is unevenly distributed across the discs. The simple solution is to give the brakes a really good thrashing and get them properly hot and see if that improves matters - my guess is that it will. Try them for one more track day and see how they are then.
No opinion on the Tar-ox discs - wasn't aware they did 964 sizes (they certainly don't seem to do the 928 S4 size that I use)

Jamie

 

[Guest]

Hi Jamie,

Yep I think it is a probably a build up of pad material which is causing it but weirdly it only really happens after a couple of laps. The first few laps are fine then all of a sudden the wheel starts jumping out of my hands when braking hard for a hairpin. It stops ok but feels more than a little disconcerting.

I always do the recomended cool down lap etc. so it's frustrating when I'm at a trackday and haven't got the confidence to really push the car after a couple of laps.

Have you noticed how the drilled holes get bunged up solid with brake dust after a few sessions? I 'm sure that doesn't help the judder either.

The 20 groove Tar Ox discs look like they will stay cleaner. Not sure why...

 

[Jamie Summers]

I know what your talking about, you just need to get the brakes hot enough to lay down a new layer of material onto the discs. Just keep stamping on them through the course of the day and it should improve - I've had similar problems on solid discs too. I don't think the holes really help matters, I get the impression that they are more for 'show' than 'go' on these particular Zimmermans. I've still not really used them in anger (two very wet days at Spa aside) so I can't really comment on them in terms of longevity and cracking etc, but I suspect that when these ones are trashed I will go to OEM 964 RS discs for the rears (same size as C2/4) - the fronts are more tricky as I don't believe there is an OEM drilled disc in C2 size. There is one in 928 S4 size (it's the 968 MO30 disc), but they are something crazy like nearly £200 each !!!! I think the only long term solution is either to go back to OEM solid discs or to upgrade to 964 RS calipers or Big Reds - both allow the use of the OEM RS/Turbo drilled disc. If you go for the Tar-ox discs I'd be interested to hear how they work for you - although I have absolutely no foundation to make the judgement, I've always thought they were a bit Max Power and probably a triumph of style over substance - I look forward to being found wrong ! The other cause of the problem could be teh pads themselves - which Pagids are you running ? Could be you need to try a more or less aggressive pad ????
(Out of interest / nerd value, whilst the 964 RS caliper and the 993 caliper that I use is essentially the same part, the 964 RS version has slightly bigger mounting lugs which moves the caliper a tiny bit further away from the hub and allows you to use the slightly bigger diameter RS / Turbo disc. It took me ages to figure out why I couldn't use this bigger disc even though my calipers look identical to the RS ones ......................)

Jamie

 

[944psi]

ORIGINAL: Jamie Summers

I've always thought they were a bit Max Power and probably a triumph of style over substance - I look forward to being found wrong !

Not quite Max Power - I have Tar Ox x-drilled discs on my 944 S2 - The previous owner had them fitted when he worked for Fast Car magazine! I've not driven on them yet as I've been sorting out some other problems - but they look the part!

Phil

 

[Melv]

Keep to OEM drilled and just drill out the brake dust before each track day.

 

[Guest]

the problem is they don't make OEM drilled discs for the standard 964 C2.....

Looks like I need to upgrade to 993 calipers and discs all round.

 

[964rh]

I suffered from this at Donnington yesterday, but with oem discs + pagid blues.
Fine for the first few laps then severe shaking wheel.
Under hard braking it disapeared but on those occasions when you don't need to stamp on the brakes it was back with a vengence.
On inspecting the discs they have fine grooves (and a couple of bigs ones) on the surface and sh1teloads of residue brake pad build up. Also got a slightly warped nsf disc, even after being anal about colloing down.
On advice of others yesterday, I'm going to gice the cross drilled ones a try as the oem discs have only been on for two trackdays and 4k road miles.

Who's the best/cheapest place to get the discs from?

Rob

 

[964rh]

Slider

The pedal stayed where it started! no change in height, no fading just a judder when not hard braking.

So if the pads are getting too hot, would cross drilled disks help the cooling? or is it worth having a look at a properly plumbed in set of foglight ducts?