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MG MGB GT V8 Factory Originals Technical - Brakes - Revisited

I know vented discs for the front has been discussed before, but I was curious if anyone had tried the slotted discs available from the MGOC.

Are they better than stock ('67 GTV8)? Would they be considered an intermediate way of improving braking (assuming the rest of the system is in top shape)?

If they work well, $99 is cheap for an upgrade.

Thanks in advance.

D Atherton


A good web site is - If you look at Wilwood there is lots of tech info.

You may also want to consider change of pads first, even cheaper, and how you want to develop car.

I use wilwood 4 pot vented so cannot answer question directly- but at least a reply.


Did you buy a kit or "do your own thing"? The Wilwood calipers supplied in these kits are available in the US for approx $US100 each, so it is rather frustrating to see how expensive UK kits are. It may be possible to make a worthwhile saving, but only if a suitable disc can be identified and sourced. Having looked at Wilwood's product line, I suspect that the discs in these kits are not Wilwood items and that they may even be off the shelf items? Does anyone know the identity and/or source of the discs used in the Wilwood kits?
Pete Green


I use my car everyday for work so I usually go for off the shelf items that can be fitted in a weekend.

I would suggest you speak to Rally Design, Cambridge Motorsport, Hi Spec and Wilwood for identity/source and fitment.

Going direct to US is a good idea as I've just bought one off uprated halfshafts from US for £400, Quaife wanted over a grand.



I take it your Willwood system bolted on without mods? How much uprated are you over standard V8 discs and pads and did you find a significant improvement?



The only modification I made was to use a M spring to hold pads in place. The callipers are very light but have only 1 split pin and no retaining springs.

I'm not a heavy brake user (discs plain vented) and I've only tried a few tests and they are impressive.

I doubt there is a significant improvement but would give pad stability and more effective stopping, which is needed with the 4.6.

I use Wilwood pads and these squeal so I will change to greenstuff.


The Wilwood kits in the UK are put together in the UK using Peugeot 404 rotors with a adapter to bolt the 5.25 inch caliper mounting spacing.
Bigger and vented rotors does not improve your braking, I know that it's a wild statement, what does your stopping is the tires (tyres) Bigger rotors minimize and dissipates heat faster therefore improving the effectiveness of the brakes.
A solid rotor is OK for normal street driving, the area to improve is the area of the pads, pad quality, and compound to minimize heat and fade on the brakes.

Four pots equalize the clamping on the rotor thus improving pad contact area and wear.
Improve your braking by buying good quality tires with ratings of A and A, tread wear of no more than 200 with good compounds and resins. Tyres like Pirelli p-7, Toyo’s R1, Kumhos Victor R 700, etc. these tyres will improve your braking but will not last more than 20K miles. To improve pedal feel replace brake lines with Gunston brake lines, these lines will give you a harder pedal thus given the idea of a better brake and improving clamping pressure by eliminating flex on the rubber hoses.
Brake bias can then be adjusted by using different pad compounds between front and rear, or using smaller wheel cylinders, and also by adjusting tire pressure combine with weight distribution. If all of this fails then install a brake bias and conduct several stops to adjust properly.
If the easy way out is chosen then change brake pads only with the best money can buy. I use Ceramic pads or Blackhawk; black mix with a set of greens gives a good bias. Ceramic pads are easy on rotors.

Rotors with holes minimizes the braking area and must be inspected for cracks, groove rotors are more desirable. Lighter rotors are better for the suspension it does eliminate usnprung weight.
The best would be alloy rotors but they are very expensive.

Sorry for the long reply.

Bill Guzman

beg to differ - in practise bigger rotors CAN improve the braking - if you use adapter brackets to move the calipers further out to the edge of the new bigger disc then the turning moment is bigger and stopping power is also bigger, even if everything else is the same. Then you may find the next weakest link which may well be tyre grip and you find you can lock up when you couldn't before. Please correct me if I'm wrong - this came up in a previous thread and the logic looks good to me.

If you are buying a new brake kit for your V8 tell the supplier your precise wheel set up.

The first kit I bought for my factory V8 with (then) standard wheels fouled the rivetheads on the inside of the wheel rim.

The supplier suggested grinding the rivet heads down, and was only prepared to refund the purchase price when I got VERY nasty.

I initially used Black Hawk pads with the new kit,(this was five years ago, they were excellent but on the Basque Rally in 1996, they tore the disks (rotors) to shreds in under 2k miles. I now use softer pads, which squeal and are not quite as good - but at least the disks last much longer.

Safety Fast

Nigel Steward

I don't want to start telling tales, but if you go to HiSpec, be careful. Nice product but you are likely to find dealing with them a very difficult experience.

I recently researched tyre choice in the UK- some comments below

High Performance Tyres

1st) Bridgestone Potenza S02
Can offer low traction on rear axle on a wet surface
2nd) Goodyear Eagle F1
Best in wet but scored poorly for dry handling
3rd) Pirelli P7000
Did well in wet but scored poorly for dry handling

Toyo Proxies T1 Plus
Unimpressive in wet braking but good in dry braking

Kumho Powermax 769
Poor in wet and dry handling and worst in test for wet braking

Yoko AVS Sport
Generally average

I did not mention Michelin because you will need to see Bank Manager first.

Anyway, pays your money and takes your choice.

Just got soaked putting lid up.

Brake bias is an important point although so far for road use I have not found a problem with brake.


Thanks for your helpful info. You quoted the Peugeot 404 as being the rotor used by the Wilwood kit. I'm not aware of a 404 model...should it read 505? This would tie in with Roger Parker's solution which uses the Austin Princess 4 pot caliper with vented discs from the Peugeot 505 Turbo.
Pete Green

Yes, you are correct Pete it's 505 Peugeot rotors, which it's almost impossible to get here in the US.

David, yes, brakes work on leverage, starting with the pedal ratio down to the rotor size. The pads should be about 1/8 of inch from the outer portion of the rotor. But if you don't have traction no brake can stop the mass.
It's a combination; bigger brakes, better tyres, same as more engine torque, more traction needed.
The point is that, what stops the car are the tyres, sometimes by just having the best possible tires, and pads, that along can improve the braking distance of any vehicle.

An article that was just release by Grass roots Magazine Did a Miata (MX5) project in which they install a big brake kit, the braking distance was improve very little, in fact I don't think it warrants the cost of a big brake kit. In a racecar the mission is to have good brake modulation, control brake fade, brake bias, pad wear, leverage to avoid fatigue, and must of all dissipate heat.
A way to improve the braking on the MGB would be by:
1. Insuring that all brake components are in good working order.
2. Replace rubber hoses with braided brake hoses
3. Install ceramic pads
4. Install good traction tyres money can buy
5. Insuring suspension components are in good working order, shocks, bushings etc. front & rear.
6. And always make your braking with the front tyres straight


It's a shame we can't do a have access to inexpensive Wilwood calipers and we limeys can get vented Peugeot 505 rotors locally "over the counter". Having said that, I wouldn't want to pay the excess baggage charge on a suitcase full of brake rotors! Thanks for your advice. I will ask my parents to bring back a pair of calipers on their next US trip.
Pete Green

The Grassroots magazine article shows the Miata with big discs and new calipers taking 15 more feet to stop from 60 mph than stock. go figure??!!.
Do your brakes begin to smoke or fade? If not why upgrade. The new hi performance pads are the first step. They have much higher coeffecients of friction and much higher temperature tolerance before fade. You do need a first class hi temp grease in the wheel bearings to prevent a lube failure. The hi heat will migrate through to the axle and the bearings.
Barry Parkinson

Wilwood is just 2 miles from my house, If anyone is willing to pay for the freight I be willing to assist you in getting the Wilwood calipers.
Bill Guzman

Any thoughts on changing the rear wheel cylinder bore size or what shoe compositions are available? My brake balance is shifted about as far as it would go and I'd like to bring that back towards the center. I've got '70's mid size Ford single pot calipers on front and it skews things a bit.
Jim Blackwood

Jim, if I understand you correctly, you are saying that the rear brakes are braking loose before the fronts, therefore you want to change the bias balance between the front and rear brakes.
Yes! One of the solutions is to change the rear wheel cylinders; the must common is to replace them with smaller cylinders from a RD, in the area of brake shoes, replacing them with a organic material (non-metallic) some even cut the amount of shoe material thus this is not recommended. The brake bias you want is when the front tires can be locked before the rears
And the measure distance becomes the shorter recorded during the test you perform, do not go for feel only hence we all have different likes.
If you want to increase the braking of the rear then install bigger wheel cylinders. If you have Ford calipers then check the year and model of donor car and install the wheel cylinders that match the calipers, that would be a good starting point.
Next is to check with manufactures and check with them if they have a compound that it is gripier than what you are using, manufactures to contact Hawk, Brembo, they may not have shoes but they can give you a lead.
And the other option is to install a brake bias valve from Tilton or Wilwood.

Bill Guzman

Bill, it's been long enough since I locked them up that I don't remember whether the fronts or rears lock first. Seems like on dry pavement it is balanced but in the wet the fronts go first. Can't use the bias valve as I have separate master cylinders for front and rear, with the balance bar almost all the way to the end of it's adjustment range. It's adjustable from the cockpit so more travel would be nice, that way I could back off the bias in the rain. I just upgraded the threaded rod and got a little more travel in the process, but I'd rather not be that far off center.

I think this means that I need larger wheel cylinders, but I don't know what is available that matches the MG backplate. I had originally planned to go to disks in the back but experience has demonstrated no real need to change them other than the lack of self-adjusters. Any thoughts on that?
Jim Blackwood

Jim, yes waht you need is larger wheel cylinders.
Also check the master cylinder size.
With a dual master cylinder you have to match the size properly. The master cylinder is now only feeding one axle. Larger wheel cylinders will also increase pedal travel.
If you want to replace the rear wheel cylinders on the B. this is possible due to the mounting style of the B which is a C clip must domestic cylinders are bolted therefore the backing plate of the B can be drill to match the wheel cylinder of your choice.

First check the master cylinder pressure, to increase the pressure to the rear wheels cyl. decrease the size of the master cylinder.

I am late and wife is calling, sorry for the spelling etc.
Bill guzman

Just a quick point on slotted/grooved discs. They are designed to 'clean' the pad surface and as a result the grooves tend to 'fill' with brake dust which solidifies. Over a period of time the grooves become less effective as the fill with dust. Every so often you will need to remove the wheel and use a small screwdriver or similar to clean the grooves to retain their usefulness.
IMHO, plain vented discs are more than suitable for normal and fast road applications. I have a turbocharged Rover which I occasionally take on the track and find no problems with plain vented discs and Mintex 1166 pads. Along with some Elf HTX racing brakle fluid, I have yet to experience brake fade - nor do I ever expect to. The local circuit has a very long back straight and I can reach speeds in excess of 200 kph before having to brake heavily for a hairpin and the brakes work faultlessly every time.
As someone earlier in the thread correctly pointed out, cross drilled discs are prone to cracking due to the uneven cooling across the disc surface because of the holes.
Stick to a plain vented disc with a set of decent pads and you can't go wrong. That set-up will do the same (if not better) than a more 'exotic' kit.
On another note, I too have had dealings with HiSpec which has led me to never want to go to them again. I have also heard of others who have suffered the same fate.
Gary Boxall

Gary - I'd be interested to her your HiSpec story if you are prepared to email me directly about it. I've heard of two other people besides myself who have had a pretty tough time with this company and who wouldn't go there again.

Check you inbox
Gary Boxall

Gary/ Marc

Can you copy me with any information re HiSpec, as I have recently been discussing a rear disc brake conversion with them.


Gary, Adrian Salisbury,
I've sent your email addresses to Paul and he will probably ask you what your HiSpec stories are.

Hi all you brake experts,
Is there an optimum caliper position on the rear IE.
12-3-6 or 9 o'clock?.I've been experimenting with a
rear disc conversion and it is obviously best to know where to put the caliper for best performance,
cheers, Kevin.

It is probably going to be dictated by the caliper you use. You need to have the bleed nipple so it is at the top - otherwise it will be nigh on impossible to bleed the rear brakes without removing the caliper.
Gary Boxall

Many configutrations are used, one thing for sure follow Gary's advice for the nipple position for ease of bleeding the air out of the brake system.

GM Camero/Firebird uses the 11 o'clock on one side and 1 o'clock on the other. This eliminates some what the torque action on the axle during heavy breaking on a Positraction differential.
Bill Guzman


What front and rear brake specs are you using?


Front end is complete RV8 axle.Proposed rear end
(hopefully) VW Golf GTi calipers(non vented disc type).I chose the golf calipers because they have
the mounting flange quite a good way out and also
they have a cable operated hand brake.I haven't got as far as choosing discs yet because until I sort out the mounting position won't know the depth of the bell
or disc diameter I will need.I did try a Ford Sierra disc and it was quite close to what I think I will need
except it it was vented.Any other ideas are very welcome.

I am very interested in a rear disc conversion.
I think I read somewhere that Rover 800 rear discs will fit straight on to the hub and the calipers are rigged for a handbrake. All you need is a caliper bracket and special hand brake cable ( I think ).
Will you get better performance from rear discs or is it better to stay with the original setup?

Mark Rawlins


My reason for changing is that I find my drums a pain, rather than uprated performance.

Hi Spec (Mmmm) do a B conversion prob cost about £350.

I have asked Andy Robinson (Drag car builder) to give the conversion some thought. If enough people are interested it may become economical viable to put a kit together.

I still have one other lead to follow but please contact me if interested in above.


In answer to the original posting-if you want to consider an easy upgrade-i would have thought that one of the semi-metallic linings would give a better co-efficient of friction for greater stopping power. These linings wont fix brake durability over repeated stops-that comes from better heat dissapation through the use of vented discs....
Before spending any money on any Wilwood caliper for road use-I would examine the construction.The examples that I have seen do not have outer wiper seals to prevent road dirt becoming trapped in between the piston and bore above the fluid seal-OK for racing use but no good for the road.Wet (salty?) road dirt will score the ally caliper body trashing the ally protective coating and seizing the calipers......
I have done my own disc brake conversion for the rear. The std drum setup is very good-the drums are quite large-but they go out of adjustment so quickly giving a long pedal. This is cured by the discs with a good pedal feel and no reduction in performance when you really get to use them(on the Nurburgring for instance!)Try


John Bourke
John Bourke


What parts did you use?

Will the MGF rear discs fit?


A rear disc conversion for SD1 will be available in about 6 mths designed to fit B as well.

Also SD1 axle for B and 6 speed box should be available.


In effect a 6 speed is already available. Caterham have developed a 6 speed box that is designed to replace the sierra 5 speed that has been used in caterhams for 10 years now. With new boxes possibly being in limited supply in the future an alternative was required and 6 suited the k series which is the main engine currently. It has the same dimensions and pickups as the sierra box, hence would be an alternative if you had the rest of the kit to convert to the sierra box in an MGB. I'm sure others know of the company that do the conversion kits!?


The bits mentioned are specifically designed for Rover SD1 but they have found that about 50% of their customers are using SD1 set up in V8 B's. Consequently they are trying to accomodate both types of customer.


Regarding Bill's post up there somewhere, I would agree that the tires have a _great_ deal to do with it. I left the brakes dead stock in my GTV8 conversion, only adding drilled rotors and stainless-braid hoses. They aren't even servoed but the car comes to a halt with amazing alacrity ... it's the first thing anyone who drives the car notices and there is no fade at all even in extremely hard use. I believe the sticky 195/60/15 tires simply make a gigantic difference. I did re-route the lines near the M/C simply to get them out of the hot engine bay as soon as humanly possible, and I think that may help too.

Clearly you guys are in a different league altogether as far as brake systems, but IMHO the stock setup with very minor tweaks can be amazingly effective for those not wishing to go through all the heartache. I mean, I hear of all these Princess 4-pot caliper conversions and you need those metric-to-SAE adapter bolts and all kinds of wacky stuff that isn't readily available at least here in Podunk. You can get most B brake parts from any discount auto parts chain, and that's a comforting thought.



I do not have a problem with the stock system but some people tweak the engines. I hope to persuade better half that a K midget will be useful for trip to shops.
The 0-60 for a standard car is 16secs, for a K car 4.5secs luckily the uprated brakes give 60-0 in 4.5secs.


This thread was discussed between 30/06/2001 and 31/07/2001

MG MGB GT V8 Factory Originals Technical index

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