Drilled rotors with alloy hubs ?

[Violet Elizabeth]

Any reason, in the interests of weight saving, why I couldn't get some standard discs drilled to go along with my alloy hubs and Ultralite calipers at the front ?

 

Don't think it is worth the expense of going all the way for Ali bells as well.

 

 

The (slow) birth of the Gixxerham : pics here drivel here

[Luke Beaumont]

I think the worry with drilling discs is the risk of cracking, but I don't know how likely that is. As long as you keep an eye on the discs to catch it before it became catastrophic. Each 6mm hole in a 10mm thick disc will remove about 2g, so the weight saving isn't going to be that huge when a virgin disc is around 2800g (assuming you mean the standard Herald 232mm disc). The ali bell idea is nice, but with such a small disc it doesn't save that much weight either.

[Violet Elizabeth]

I was looking at the Fluke drilling and thinning service. Seems they do more than just drill a few (random) holes, and suggest they can save a fair amount.

 

The (slow) birth of the Gixxerham : pics here drivel here

[wonkey eyed barmaid]

i drilled my standard discs. [99 1.6vx classic]

about 20 holes [maybe 25], in 5 sets of 4 [or 5], from memory...

in a spiral pattern that i measured up myself and drew onto a card template.

 

been that way for best part of 18 months, and 11k miles. no problems. done 3 or 4 track days in that time. i use greenstuff pads.

 

easy enough to drill yourself, just time consuming. each hole needed centre punching using the template, then drilling three times. 1st with a 2mm pilot drill, then again with a 5mm bit. then finished off with a 15mm bit just to remove the burrs.

 

finished results are good, and as mentioned, no cracking.

[Bare]

Drilling is 'Not Recomended' on Vented discs.. Real Rotors have Cast in holes... Solids could be OK drilled, don't forget the required chamfer.. But the question is WHY??

To save weight ?? some one actually believes that?

In the very least Drilled rotors Do eat pads at a prodigious rate.. in case you didn't know :-)

[Sheds Moderator]

Eating pads might indicate more friction, which is generally regarded as A Good Thing with brakes. Do drilled discs give more bite? Discuss.

[wonkey eyed barmaid]

my drilled discs dont EAT pads..

grooved discs are more likely to eat the pad, as the grooves are left sharp for the purpose of deglazing the pad surface.

 

i drilled my discs to avoid pads overheating, glazing, and gas build up. not to save weight.

 

my standard discs are solid, so maybe chances of cracking were lessened?

[wonkey eyed barmaid]

boss,

i dont see how drilling can cause more friction

 

as i wrote above, i think eating pads is down to having sharp edges around the grooves, or holes.

 

but as i also mentioned, i chamfered the holes in my discs with a large dia bit.

[Sheds Moderator]

IF drilled discs eat pads (and I accept that yours may not Grant as the sharp edges are removed) then they must, all other things being equal (question - are they?) in any given situation generate more friction for any given push. Why? Because removing pad material involves doing work, which means consuming energy, and the only energy available is by slowing the car. This is all simple law of conservation of energy stuff. Whether it makes a real difference is up for debate.

[wonkey eyed barmaid]

boss,

i agree.

pads being eaten means more friction. which in braking terms = good. but why?

 

could it be that plain solid discs form a layer of gas (due to heat build up) under the pad surface, reducing friction. drilled discs dont suffer this because the gas has somewhere to go (through the holes), so full friction is retained, and pad wear increased...

 

 

perhaps an email to EBC, brembo or tarox or someone will get the full technical explanation as to why holes are good...

[Violet Elizabeth]

The fluke site reckons they saved 1.2 kg a front corner for a Westfield on Cortina discs.

 

The (slow) birth of the Gixxerham : pics here drivel here

[elie boone]

I think that grooves are better than drilling holes in the disc, a drilled disc always tend to crack in between the holes.

My disc's have 6 grooves on them but on request you can have 12 ( Red Dot )

The main purpose for drilling or grooving disc's is to provide an escape for the gasses that build up in between the rotor and pad providing more effective braking at higher temp.

[gee_fin]

The thinned disks we sell (sold, will come to that later) were thinned, crossdrilled and chamfered. When doing this to an existing solid disc (I would only recommend using new discs) it has to be done to a certain pattern. The edges are chamfered and further steps are taken to ensure that cracking will not occur.

 

The final results were that the discs were significiantly lighter than the standard item having had weight removed from many non-critical areas (have a quick look at brake_discs_01.jpg for an idea of the machining involved. On all four disks, in the vast majority of applications, this resulted in a 4kg+ weight saving in total (all unsprung of course). This service was only available on solid discs.

 

We have since stopped selling the discs, nothing to do with the quality of the product, I actually still use a set myself and have been on the same set with no problems for the last two years, purely due to supplier issues - with lead times varying from one week to four months it became impossible to keep to deadlines and as such we had to drop the supplier.

 

Hopefully we'll pick up the service again in the near future when we find a suitably gifted source. If interested in a set, I can send you direct to the previous supplier, as said, I have absolutely no issues with the quality of the work, just with the variable lead times!

 

Graeme.

 

________________________________________________________

graeme finlayson / tyre warmer / fluke motorsport

graeme@fluke-motorsport.co.uk / www.fluke-motorsport.co.uk

 

Edited by - gee_fin on 8 Mar 2005 21:33:01

[Violet Elizabeth]

Thats the perenial promblem with the niche end of the market, when I was talking to James Whiting about the Fireblade a few years ago he was saying much the same thing, just couldn't guarantee lead times from the quality suppliers.

 

Would be interested in your person Graeme, I think I have found someone locally, but always good to have a backup.

 

The (slow) birth of the Gixxerham : pics here drivel here

[Taran Las]

I've been running drilled discs on ali hubs for over two years (and a few track days). No cracking - only disadvantage is they are slightly noisier than standard.

*thumbup*