Drilled and slotted brake disks

Technical MGB discussion
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Not_Anumber
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Forename: Chris
Surname: Silk

Drilled and slotted brake disks

Post by Not_Anumber » Tue Oct 20, 2020 7:17 pm

What is the thinking about drilled and slotted brake disks - are they a worthwhile upgrade. My solid disks would need an awful lot of wire brushing before i can get my 79 BGT back on the road so ive been wondering about replacing them in any event. Are the slotted disks as beneficial as they say and if so are there any makes to go for or to definitely avoid ?

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Charles Farran
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Re: Drilled and slotted brake disks

Post by Charles Farran » Tue Oct 20, 2020 8:10 pm

Hi Chris,
Some 6 or 7 years ago i replaced the original discs & calipers with drilled & slotted & discs , new calipers & green stuff pads as i felt it made sense (to me anyway) to upgrade the braking. I felt at the time there was an improvement for on road spirited driving. I got mine from MSC but am aware there are other providers .
I am sure others will have their observations & recommendations.
Cheers, Charles
1980 Roadster

Ian Fozzard
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Re: Drilled and slotted brake disks

Post by Ian Fozzard » Tue Oct 20, 2020 8:57 pm

When launched, the brakes on the MGB were given top ratings by motoring reviewers. I've never felt the need for anything more than standard brake components, even when using the MG in mild competition. I think if you were contemplating doing long circuit racing when the brakes might overheat, some improvement may be required.
Just my opinion of course😊!

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear

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Mnripley
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Re: Drilled and slotted brake disks

Post by Mnripley » Tue Oct 20, 2020 9:29 pm

Agree with Ian the brakes are normally good for energetic driving. A cheaper option would be to fit air ducts like the Sebring ducts to direct more air to the brakes.

Vic Butler
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Re: Drilled and slotted brake disks

Post by Vic Butler » Wed Oct 21, 2020 9:23 pm

The original discs on my 1977 BGT were worn and grooved so I fitted drilled discs and new standard pads recently. The brakes were a lot better but was it solely down to the fact that the old ones were worn or not?
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

Not_Anumber
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Re: Drilled and slotted brake disks

Post by Not_Anumber » Fri Oct 23, 2020 3:05 pm

I'l see how my original discs look when Ive wire brushed off the surface rust. If they are near perfect still I will leave them as they are until the rest of the car is finished and i get it back on the road.

But If they look a bit pitted or grooved I could be tempted to upgrade to the drilled discs and Yellowstuff pads Charles mentioned.

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Charles Farran
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Re: Drilled and slotted brake disks

Post by Charles Farran » Fri Oct 23, 2020 5:11 pm

Chris - i think you mean "green stuff"!
An alternative which some have tried is to try V8 pads which i understand fit standard MGB calipers but give a greater pad area on a standard disc.
Cheers,
Charles
1980 Roadster

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Peter Cresswell
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Re: Drilled and slotted brake disks

Post by Peter Cresswell » Fri Oct 23, 2020 9:48 pm

I use V8 pads which give about a 15% increase in pad area and fit without any modifications. Currently I'm using Mintex 1144 material which is a semi competition material which has good stopping 'grip' from cold so is good for sprints and hill climbs. They do go cold though around town and after a long motorway journey and then squeal badly. I don't use anti-squeal shims though. This is probably the best upgrade for the money unless you do some serious competition. The days of own branded 'cardboard' pads that didn't stop the car more than once have long gone and any 'standard' pad material will be just fine for all types of everyday driving.
Next upgrade I would suggest is to remove the disc shield/guard to allow more air to cool the disc. This is easily done but you do have to remove the hub and then the disc to do it. Might be something to think about when you need to replace the discs.
Better brakes really only come from using bigger diameter discs but this means going to larger diameter wheels (hence the MGC had 15 in wheels) which is a big £ outlay. Some improvement can be had for using a better quality disc that has a higher coefficient of friction and here price is a good indicator to the quality. A pair of standard quality OEM disc will cost around £25 to £30 per pair from any of our favoured suppliers. However you can buy better quality such as Brembro (about £50 per pair) or Black Diamond (£100 + per pair).
There is a whole range of pads available but beware as some are marked 'Competition' or 'Racing' and your insurer might not like this. Mintex 1144 are marked 'Competition' but EBC Green Stuff aren't. At the upper end of pads are Hawk Ceramic pads at around £200 per car set!
As to whether it is worth buying grooved or drilled (or both) is really a matter of choice, but if you do any sort of competition (particularly in Historic classes), then check they are allowed. All the FIA spec races use solid ungrooved discs and they don't have much trouble in stopping! Remember though that brakes work best when they are warm and grooves and drillings are there to cool them down. So if you go for these discs make sure you use them!
Pete
1969 MGB Roadster
2020 MG HS Exclusive
2007 Mercedes SLK
Plus 34 other cars since 1965

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