re drilling brake discs

[davidcupra]

Hi all . After a little advise . I'm currently doing the 312mm tt brake upgrade on my mk3 Ibiza cupra I'm at the point where I need to re-drill the discs to 4x100 . Basically I ordered A a set of discs after asking if they'd be multi fit ,they said they wouldn't be turns out they are . Just weighing up whether its possible to drill multi fit discs or rather if its safe as you can use 2 holes but have to mate the other two or whether cut my losses and find other discs. I did try a search but found no definitive answer

Thanks in advance david

 

[chris_200120vt]

i put a s4/tt rear brake conversion on mine , tt discs where 5 stud had to re drill 3 holes

when i was happy where the holes would be bolted the old to the new disc fit perfect

 

[davidcupra]

thanks for that , the problem i have is drilling multifit discs and whether its safe to merge two of the holes. looking at your disc it would look similar

thanks david

 

[Danturbo225]

Just get Ibiza Cupra r discs 312mm then no drilling I think?

 

[davidcupra]

Thought cupra R had 305mm discs

 

[lexyy]

Cupra r discs are 305mm i had my 312mm redrilled in the way the discs shown above are and also had my carriers milled down but just need to get it all on hopefully this weekend or next!

 

[davidcupra]

yep done all the required bits and bobs , was just wondering if its possible to re drill multi fit holes or if someones done it as the discs already have alot of holes in to start of with . lexy what discs and pads did you go for in the end

 

[CatB1]

Please tell me that you are going to weld the redundant holes up.


Pete

 

[davidcupra]

no as you can't weld brake discs as it might alter the properties of the disc you could make interference fit plugs out of steel , could be wrong also its not the bolts that stop the discs moving its pressure and friction applied by the wheel against the hub. having said that it does look scary drilling multiple holes in a disc esspecially a multi fit disc also another worry is less material to transfer pressure from wheel to hub resulting in possible cracking

 

[CatB1]

You could weld the holes up by using a series of spot welds & gradually build up the weld (similar to when welding bodywork, so as not to cause rippling to thin sheet material due to limited heat application). Would advise against an interference plug due to the heat cycles of the brakes (expansion & contraction & the fact that the holes are close together(area of influence)). Guessing you've never seen a disc failure before, my son's Cupra front brake exploded 5 years ago, a quarter of the disc was completely missing. The clamping action of the wheel did'nt stop it, the bit that was missing had cracked & separated through two of the bolt holes. Just a bit of cautionary advise, make sure you do it properly.

 

[davidcupra]

Thanks for the advice . Although I think you mean tack welding as spot welding adds no material to the weld pool also would be similar to an inference plug as they'd be dissimilar metals and would expand at different rates . Tack weld still requires alot if heat and would be difficult to do on a cast iron brake disc not to mention extremely hard to make sure the disc is still balanced . Welding a brake disc is near to impossible . You maybe right about the interference fit plugs and you guess wrong I have seen a brake disc fail not the area you described though

 

[CatB1]

I wish you luck. I also think your disc will already be out of balance due to material already being removed.


Pete

 

[davidcupra]

how will the disc be out of balance if the holes i drill are opposite each other and are equal in size

 

[F2 Stu]

ran 312's on my cordoba, drilled out out to 4 stud and gave them serious abuse, never had an issue in vibration or weakening the disc by drilling 2 extra holes.

 

[davidcupra]

ran 312's on my cordoba, drilled out out to 4 stud and gave them serious abuse, never had an issue in vibration or weakening the disc by drilling 2 extra holes.

thats great reassurance i needed. what discs were you running if you don't mind me asking

 

[F2 Stu]

initially ATE discs, when I wore those out I had EBC, both grooved flavour.

drilling them out couldent be easier if you got a spare drive flange to drill through as a guide and a piller drill - enlarge the retaining screw hole to 13mm +, bolt up the flange using 2 bolts then do the other two through the flange, take it easy at this stage as your real close to the other holes but you shouldent break through on a 13/14mm clearence hole.

 

[davidcupra]

I did something similar using a wheel spacer . Managed to not break through although it does look scary close to the other holes . Thanks for your advice

 

[F2 Stu]

I did something similar using a wheel spacer . Managed to not break through although it does look scary close to the other holes . Thanks for your advice

No problem, it might look scary but it isn't when you consider the disc is primarily held into place by the road wheel being clamped onto the hub by the wheel bolts, not solely relying on the bolts acting as dowels to prevent the disc rotating on the hub.

 

[davidcupra]

Yer that's what I thought . Was concerned that's there would less surface area on the mating face of the disc to cope with the heat cycles of the brakes and clamping force from the cars weight resulting in cracking not 100% sure though . Just urring on the side of caution being brakes and all. Think it'll be alright though