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Grooved discs.

Big Dave

Big Dave

New member
Hi Folks
I might get shot down in flames about this ,, but here goes..

My car has M030 / 928S4 front discs + callipers on.

Im trying to assist the cooling of the discs BUT dont want to fit the EXPENSIVE drilled M030 discs , which are also prone to cracking...... SO is it feasable to get a brand new pair of plain 928S4 discs + have some grooves machined in them , as nobody seems to sell grooved discs "off the shelf"...

Will putting the grooves in the discs make them brittle .??

Has anybody else done this.With any success.???

Im open to suggestions.[;)][;)][;)]
 
No experience of grooved discs but a machine shop may be able to offer advice. What do you have in the way of ducting? I got some universal ducts from demon tweeks and ran some hoses back to point at the disc area. The 968 air deflectors are also supposed to be a good alternative but need some fabrication to mount to a '44
Tony
 
I agree - get some ducting. Merlin Motorsport are good. I wouldn't expect grooved discs to do much for cooling, but more airflow will [:D]. If you're using sticky tyres I think they are almost essential. (didn't you say you nearly went into the back of me at Rockingham because your brakes went ?)

I have just lashed up a temporary arrangement (it'll probably be there for years[;)] ) using some ducts & pipework I used on another car. There's a very simple route to the back of the hubs. I'm firing my ducting at the plates fitted to the hubs - I'm assuming they are there to funnel air into the centre of the discs

I've cable tied the ducts to the lower intakes on the PU. 944 racers seem to all fit ducting into the fog light/driving light area. if mine works well, I'll probably transfer the ducting up there & lose the lights, or find some more permanent way of mounting the ducts behind the PU.


 
Yes I used tie wraps to attach the ducts in the spaces behind the PU, its tight on the drivers side because of the oil cooler and the power steering loop, I think I obscured the PS coil a bit but not noticed it having an effect.
I did have my pipe going to the disc centre but the tyre caught it, I now run it to the arb mount and point it at the disc.
Tony
 
I think I may rub the tyre on one side - will have to see. I think I cut the hose a bit too short.

I drilled a small hole in the bottom corner of the deflector plate & used some stiff wire to attach the hose to it. - I knew I should have taken some pics when I did it!

I think on my last car I attched them to the struts


 
I didn't think that grooves and holes in discs were for cooling but for allowing an escape path for gasses that build up between the pads and disc.

However grinding grooves into your discs would be a simple job for someone with a well kitted out machine shop. You will need to choose the cross-sectional shape of your groove carefully though - if you choose something too sharp, like a true vee groove, you will be introducing features into the disc that will make it more prone to cracking along the length of the groove. You want the vee to be as blunt as possible - ideally a semi-circular shape. I would have thought that grooved discs you buy will be slightly thicker so a sharp true vee groove feature can be used. Also the groove shouldn't extend all the way to the edge of the disc - it should stop 3 - 5mm short of the disc rim - similarly at the inside edge of the disc.
 
EDH
Yes that was me that almost "collected" you . I think it was a combination of you braking earlier that i had anticipated + my brakes "going" off slightly....I was a tad concerened at the time...[;)][:)][:)].
Yes i had been thinking about some kind of ducting , but thats about where it had stopped, at the thought stage..[;)][;)][8|][8|].
The other reason for "grooving" the discs was to help pad material / gasses escape as has also been mentioned....[;)]

Anybody fancy a day at Rockingham later this month or next month.????
 
That's right - I wasn't at all happy with my brakes at Rockingham - not confident they were going to stop me at the last minute, so was being over cautious.
- your corner speed was probably 10mph over mine with your sticky tyres as well :)

I think they may have glazed on my first session when my instructor brought me in & had me sat in the pit lane for 10 mins without givng the pads any chance to cool off.

I've picked up some Pirelli pzero-C tyres now, so definitely need some more cooling.

Ducts are one of the cheapest and easiest jobs you can do - and for a track car like yours, well worth it.

I didn't like Rockingham that much - hoping to fit in another Donington trackday soon + a trip to Cadwell
 
I thought Rockingham was great. Even though i had some probs with one of my CV joints/driveshafts that ended my day early.[:mad:][:mad:] Also what with the occasional downpours..Aided by my over zealous right foot into drift style cornering.[;)][;)][;)][;)].It made for quite an eventfull day...[:D][:D][:D]
So i want to make another trip to the Rock to make a full day of it....

Hope the P-Zeros do you well.????
If you aint done Cadwell already , Im sure youl defo enjoy it. When are you thinking of visiting the Lincolnshire circuit.????
 
Big Dave. I had cooling issues with my car and I put the 968 deflectors on + s/steel braided lines and use some expen$ive racing brake oil. This has helped a lot although I'd like to decrease my overall pedal travel. I'm going to follow Fen's advice and get some Performance Friction pads as I think they will be better suited than my EBC's. I've heard that drilling or grooving discs is not such a good idea. Better to buy ready made ones if that's what you're after. I imagine that with the KW's adding more grip/traction than the Mo30's this would increase speed and therefore put brakes under greater load as well?
 
When you put the 968 deflectors on,, how did you attatch them to the wishbones.?? OR do you have 968 wishbones.??

Ive got the 968 deflectors that attatch to the strut but just need the wishbone ones aswell.

I would by ready grooved discs ,, if i could,, but I cant seem to find anybody that makes them for the M030 disc....Thats why i was going to get some grooved....
 
Slightly OT ...

To fit 968 wishbone ducts on 944 wishbones you can make U-shaped brackets that attach to the top of sway bar drop links, above the wishbone.

Here is picture of my S2 with these - a poor picture, but you get the idea.

968brakeducts.jpg


Some 944 turbo had air ducts in the front bumper which later ones (90, 91) don't seem to have, although they're listed as stock 944 turbo parts. Perhaps they were M030-only.

951brakeducts.jpg

 
ORIGINAL: TTM

Some 944 turbo had air ducts in the front bumper which later ones (90, 91) don't seem to have, although they're listed as stock 944 turbo parts. Perhaps they were M030-only.
Click to expand...

I have only seen them on original M030 cars. They are hefty ducts straight from the front PU at around 6" by 3" and point at the standard 944 deflector plates on the strut. I have removed my deflector plates and attached a flexible hose from the back of the duct to the plate bolts pointing at the centre of the brake disk and believe it is the main reason I have never had brake problems.
 
there were some possible Cadwell dates floated on Titanic - can't quite remember when. It's probably my favourite track & haven't been there with the 944 yet.
 
Those 944 turbo air ducts are not m030 only, I have them on my 1987 turbo.
Whats there on other cars? is it closed off, as there is a hole in the wheel arch liner for them to poke through
 
TTM.
Ta for those pics..Very helpfull..

Just out of interet.
The ducts fitted to turbos, are they fitted to both side of the car.??
Im thinking the drivers side will be missing as the oil cooler sits where the cooling ducts go.??? OR is the turbo oil cooler sited somewhere else.???
 
I'm not sure exactly what the S2 cooler is like, but the Turbo one is only a little square thing mounted against the outside edge of the rib between the middle slats and the end ones.
 
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