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MG MGB GT V8 Factory Originals Technical - Brakes
| Has any one changed out the front brake assemblies for better performing and improved stoppimg power? These standard calipers just dont have the stopping power. This is for my 78 MGB with a 3.5 V8. Any help would be great!|
Check out www.classicconversionseng.com
Bill has a 10 3/4 vented rotor with wilwood calipers.
They should be a major upgrade. I am doing a 302 conversion and plan on using his brakes and coil over front end.
|I have designed a brake conversion that is very powerful. The kit uses Wilwood calipers and big ventilated discs. My MGBV8 stops very fast with very little peddle pressure. The only down side is that the brakes won't fit using 14" wheels. If you are keeping 14" wheels Jake has a nice smaller brake setup. My website link is http://rebornco.com/bigbrake.htm |
and Jake's is
|My opinion is VERY unpopular in this area, but I'll run it up the flagpole and see who salutes.|
The cars with a rover v8 weigh less than a 4 cylinder car... right?
No one really ever complains about 4 cylinder breaking power... right?
A car with 8 cylinders doing 50 mph requires no more stopping distance than a car with 4 cylinders doing 50 mph assuming the weights of the vehicles, and all the road conditions, etc match... right?
Does matter if it takes you 10 seconds, or 5 seconds to get to 60 mph. 60mph = 60 mph regardless of how long it took to get there... right?
Why do we fuss about the brakes on V8's and we don't fuss about them on 4 cylinder cars? If you ask me, they're the guys who should be pissing and moaning. Their cars weigh more than ours!
I will grant you this: the ability of our cars to accelerate more quickly can put us in a situation (more often) where we could need to use our brake pedal a little more judiciously, but how often is that a reality? Couldn't we use the same logic for a 4 cylinder with dual SU's vs a Zenith carb? What about cars with the O.D. trans: they weigh more right? Rubber bumpers vs chrome bumpers...
I know I'm playing the devils advocate here, and I am ONE HUNDRED PERCENT in favor of safety. But the idea of "oh well it has 8 cylinders it must need better brakes" is hog wash. The idea of "the factory brakes never worked as a 4 cylinder car, we should fix that now" is legitimate, but I've never heard anyone say that.
Am I arguing semantics? Am I missing a point somewhere?
|Justin, perhaps the cars are going faster. If what you are saying was true, then the MGB brakes would be good for any car including the GT3 Porche and Corvette, etc.|
The braking of the MGB for today standards SUCKS, the 4 cylinder to today standards SUCKS, you may put a blower and stills SUCKS. So why not upgrade.
People do not complain becouse they are purist, but wait...yes they do complain, you are just not paying attention.
End of discussion!
And yes, you missed the point Justin.
You ask for a salute, there you have it.
|front : 295mmx25.4mm AP racing rotor with AP four pots calliper Mintex 1144 pads|
rear : 270mmx8mm Brembo rotor with two pots calliper
pedal box with two AP racing MC and balance bar, AP racing screw type brake proportionning valve and hydraulic handbrake, Aeroquip hose. Good braking.
|I have heard some things about using porsche vented rotors and hubs (if also converting to 5 bolt pattern) But I haven't heard what year(s) porsche a person could find them off of. I believe they are from 911's 944's etc.. |
If anyone has info, the feedback would be much appreciated.
Try the volvo option, I have a kit that I bought. This is a set of volvo calipers and and nissan disks with a spacer. The volvo calipers have the holes redrilled, a little off centre to stop them moving. The Kit works very well with no detectable fade. They were from MG workshops in Melbourne Australia and were strongly recommeded by the engineeer who approved my engine upgrade.
There's nothing stopping you from taking a set of volvo caipers to a brake shop and asking them to recondition them, ppress some pluggs into the holes and redrill them and finally getting them to "cross drill" each caliper so that you have one line out instead of two. I was quoted about $300 australian for this job so it's not so pricy.
I believe Jake has been developing a variation of this with some success.
Actually, despite the severe rebuke, Justin has a point. You don't really NEED a brake upgrade any more than the 1800 guys do. However, the 1800 guys would probably benefit from modern brakes because when the car is being driven hard the disks WILL get very hot and subsequently the friction co-efficient will reduce dramatically. Enter the brake fade gremlin. I don't know the physics, but I would hazzard a guess that the air becomes super heated and possibly adsorbed more strongly onto the surface of the metal.
The most important thing about improving the brakes is to improve the heat radiating charactoristics of the disks so they stay cool longer. That means either drilling lots of little holes in them (as motor bikes do) and increasing the surface area availiable to radiate heat. OR directing cooling air onto the disks via air ducting from the front valance, or fitting ventilated disks from the nissan or Peugot or whatever.
The four pot calipers are supposed to grip more evenly, however the main reason for fitting them is that you can't adapt the MG ones to allow a wider caliper. They aren't symetrical (like the Rover princess/RV8)and therefor no spacer is possible. Since you have to go out and buy other calipers anyway then people figure they may as well get those that are just possibly a very little bit better. However the big improvement is to be found in the disks, not the calipers.
The air ducting is probably the easiest/cheapest thing to do. This is why the wire wheels actually give better braking than minilites, rostyles or alloys, better air circulation and cooling.
You know I've just realized that I think about these things too much, I've got to get a life!!
|Just remembered ,to help cooling you could also remove the brake splash shield from behind the disk, I had to in order to fit the thicker ventilated disks.|
Agree with your logic and in fact the reverse is true upgrade front only and you can increase stopping distance.
At road speeds the stopping distance is about tyre grip, if you want to improve braking feel try some Mintex 1177 cof of 0.61 reducing to 0.55 at 700deg.
Heat is the problem with say 4 stops from 60moh generating 500deg of heat but 1 stop from 140 say 700deg. If brakes and being used in these circumstances then pad choice and cooling become issues so changing to a vented disc will help.
Increasing weight of car increases heat generation hence larger discs for heavier cars, and with a small disc there may not be sufficient braking force to overcome tyre grip.
If you change to slick tyres then more grip more weight transfer and you therefore need more front braking to rear.
To improve pedal feel then compliance needs to be taken out of system as much as possible so braided hoses, but the fronts discs can be increased but with smaller piston areas to maintain front rear balance.
whats the piston spec of your set up?
I do not remember. I find the figures and I give them to you. But the brake pedal is very hard. Too.
|I agree with Justin: the mere fact of adding more horsepower doesn't, in and of itself, create a need for better brakes. If the brakes are not good enough for the V8, then they weren't good enough for the stock engine either. Were they good enough for the stock engine? It depends on your driving style.|
Backing your car out of the garage onto a trailer to take it to a car show, the handbrake is good enough. Coming down the mountain from Newfound Gap to Gatlinburg, with the engine off and the transmission in neutral, you can very easily outdrive your brakes. In a VERY short time! Having a more powerful engine doesn't change any of this.
Do you NEED better brakes? It depends on your driving style. Just because you CAN go faster, does that mean you will?
Nevertheless, better braking is more gooder than not so better braking, regardless of your driving style.
Notice I said "braking," not "brakes." Brakes don't stop your car, the tires do. The brakes stop the tires. Improving your brakes may very well result in increased stopping distances if the tires don't have enough grip to keep the wheels from locking up. A sliding tire has very little stopping power.
If you can lock up your wheels, your tires aren't good enough. If you can't get better tires, then your brakes are overpowered.
At front I have AP 5100 calliper four pots 38.1mmx4, the MC is AP CP2623 short travel 7/8" (22.2mm).
At rear two pots calliper 41.3mmx2, MC is also CP2623 3/4" (19.1mm).
To Dan Masters
I agree with you, braking, not brakes
I have BGT with 1950 daily use, the braking is only just. The small road here in Provence (South of France) corner on corner kill off the braking. You imagine my MGV8, 200hp env, the braking is non-existent.
Your logic holds, the reason I put together a 4 pot setup with vented discs was mainly because I had the calipers, with the parts to rebuild them for nothing, plus I knew what disc to get and I had a spare front end setup with which to experiment. Plus my GT has brakes that are not that great and I didnt want that on my V8 but regardless, I put the stock brakes on and if they don't hold up, Ill swap them out for the 4 pot vented setup. You really didn't deserve that reply from know it all steve, obviously he didn't think it through or he would have realized that a corvette with MGB brakes would not perform as well in stopping simply because its heavier. Some people just dont get things.
Ever come with pricing for the spacers, drawings, etc??
Your statement makes no sense, you are talking abotu a vehicle with vastly different suspension, weight, tire size, wheel size. One brake does not fit ALL CARS. That is just the point. The MGB brakes for MOST of us are plenty sufficient unless driven very hard. If you plan to race, whether you have a elect motor, stock 4cyl or a supercharged Hemi in your MGB you will want better brakes. If you put around like an old lady then you could probably be ok with just the front brakes.
WELL PUT! I know on my car I can get all 4 to lock up woth a completely stock system. so obviously better brakes will not help anything unless I have better tires.
Better brakes can improve stopping distance with the same tyres, if you can reach the 10% slip point a fraction earlier, as at high speed that fraction of a second will start to have an effect.
The downside is having on/off brakes which are difficult to keep at maximum braking, without abs.
What pads are you using and I assume standard B axle
|IMHO you can never have too much HP or too much braking power, so what if you think you will never use it all, at least it is there if you need to use it.|
|Michael S. Domanowski|
Pads : Mintex M1144. Rear axle? : Quaife ATB diff, 3.7/1 (11/37)ratio (automatic model)
|Bracking is a balance between tires and clamping pressure from the caliper.|
Any vehicle with increase power has the potential of going faster, therefore needs to stop faster in case of an EMERGENCY at hwy speed (safety stuff). If a 370 hp Ford V8 or a 200 hp V6 is going to be driven conservative as the 4 cylinder, then why even bother putting a V6 or V8?
Everything on a car most have a blance.
Why put a 4v carb? why not a 2v, why do we install FI? Why not adapt the MGB trans to a Ford V8 or a V6
Car will not be driven hard so... why not
Like most peole that I know that have converted their cars, use better brakes on their cars, just for that day that may need that shorter distance while traveling faster than they would have on their original 4 cylinder.
I agree with Steve on one thing. faster cars have bigger brakes Why?
But... if you feel confortable with your stock brakes then why not, it's your car and your believes.
Two cars on ice, one with big brakes, which stops quicker?
F1 car (cart) brakes, not much larger than a B, can pull 4g why, because of sticky tyres which would wear out going to the shops on a road car.
The reason for bigger brakes is to deal with the heat from repeated and high speed stopping. If the brakes are cold - in an emergency stop situation the stopping distance will not be reduced because you have bigger than required brakes because in road situations its about tire grip and the road surface.
In a race situation on a light use brake circuit the brake set ups may be reduced to save weight.
In a Rally situation on loose gravel you may want smaller brakes to reduce tyre locking.
Big drilled brakes look cool!
You mention the Mintex M1177 pads, are they type approved for road use?
I ask because they are not listed on the Mintex website where the M1155 and M1166 materials are expressly stated to be unsuitable for road use.
I also notice that the perfomance graphs only show friction and wear performance from 100 C upwards.
I have not connection to Mintex other than being a satisfied customer.
|Paul, I think you forgot "leverage" Larger disc will help on heat and......|
Yea! I think I will put my discarted MGB brakes on my LT4 Corvette, that is for normanl driving, I don't think so.
Put it to the test Paul. Adquire a small disc with a bearing in the center apin the disc and stop it with your fingers as the pads would do. Now get a larger disc and do the same, which one could you stop sooner?
That combine with a good tire= shorter distance.
Then add vented rotors and cooler brakes, add better friction pads such as Ceramic pads. The result is great brakes that can be use in an emergency
I don't drive on ice, I drive the hwys in California were I have to slow down from 75/80 mph to a stop do to traffic, I don't like hitting the car in front of me.
The point is, if you feel good with your brakes, stay with them. I follow the auto manufatures logic. The logic is, being able to stop in a shorter distance during an emergency. On ice I would make sure my traction control and ABS is functioning correctly on my Vette.
Suggestion, drive a MG with stock brakes, then drive a MG with upgraded brakes, then draw your own conclusions.
A view from a Police driver
I have no problem with large discs as long as both ends of car are considered. If you just add them to Front without uprating tyres your stopping distance will increase.
When F1 changed to a grooved tyre the braking g force went from 6g to 4g with no change to brakes, they also have a 55/45 balance.
Not sure what to make of that article. I notice that it doesn't get many favourable reviews.
Also, you uprate your brakes because you are interested in performance. I doubt anyone out there with uprated brakes on their V8 is running standard size and compound tyres.
One other issue that I don't get is upgrading the front and rear brakes. I am not making an argument, I would like someone to explain it to me. I do fair few track days in my MGB GT which I hope to soon convert to a V8. The car is totally stripped out and has standard brakes bar V8 pads and braided hoses. I am using a softish compound road tyre so I have superior grip to an original MGB GT. On occasions when braking from high speed over a brow or downhill the rear wheels have a tendancy to lock. I have spoken to some MG tuners and they recommend using the roadster rear wheel cylinders to reduce the rear braking effect. So if I uprgrade my brakes to say a Wilwood 4 pot kit and use a proper trackday rubber I will experience even more weight shift to the front and the rear will be loaded less. In this situation why do people say that the braking effect will be reduced if the fronts are uprated only and that the rears should alos be uprated? Or have I got the wrong end of the stick?
A small bit about brakes is ok but the rest is crap.
Compound is important but most road tyres give about 1g.
If say a standard road car has 80/20 Front rear split under weight transfer with a road tyre, lowering car reduces weight transfer.
With a Slick tyre you have more stopping power from the tyre which increase weight transfer to now say 90/10, hence the need to reduce the rears braking, as the fronts should lock before rears.
At this stage you really need to be able to balance the braking front and rear.
In the wet (less grip and weight transfer) you want more rear, also if you are using normal road tyres.
Maximum braking is achieved by using front and rear tyres to maximum, if not uprating tyres and grip, then simple uprating front with more braking power means the rears tyres are used less and maximum braking is not achieved. Tyres stop the car and the biggest braking system will have no effect on tyre grip, however if travelling a 66ft per second a responsive system may save a tenth of a second which is 6ft.
The objective of upgrading brakes is mainly heat, but can also be tuned to driver preference.
4 pots increase torque radius anyway, but you can have a bigger disc for heat purpose but reduce pistion diam to keep the same braking power front and rear.
I have not had chance to consider Michel's set up above but looks good.
The 1177's are not recommended for road use, but do work from cold but eat discs. They are also as far as I know outdated material and have been replaced, but not with a compound with such a high COF. A number of F's are using them. EBC ceramic prototypes have been tested recently "due to first corner last lap".
If using Wilwood then Hawk ferro carbon are available which will work from cold up to 800deg, as well as Wilwood selection.
M1177 is an obsolete material and has been replaced by F4. You will find F4 details on the Mintex Racing web site at www.mintexracing.com
Questmead at Rochdale are biggest stockists and still have supplies of M1177.
A few numbers ball park to illustrate what happens when tyre grip is not upgraded but front brakes are upgraded
OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear
Maximum front tyre grip at point just before lock up 1500lbs
So OE Front 1500 rear 1000 total 2500lb of stopping force
Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!
I understand, just have to see how my MGB brakes hold up on track when I have my V8. I have made my own ducting from the front valance about 2inch diameter and I will probably use V8 mintex pads, though not sure which ones yet and stick with the Castrol brake fluid that I am using as it seems to be quite good. As long as I can stop brake fade then they should be OK. I'm thinking of removing the servo to try and get a firmer brake pedal.
Do you have uprated brakes?
|Paul, you are correctly about the tires. I use Kumhos Victor racer tires on my race car Mazda Miata or Mx5 in the UK, these tires are soft compound for road racig purpose. Yes with the stock brakes and Black Hawck pads(Blue) the brakes improved. the brakes got better when the dia of the rotor was increase, I was able to go deeper on the turns thus increasing lap times.|
Brake bias can be adjusted by using different compound pads front to rear or by changing dia of the rear calipers pistons and also by installing a poprtioning valve (lever type) in the cockpit.
The larger disc helps in cooling and on leverage.
Larger rotors are use when softer compound tires are used, this is what improves the stoping distance.
Now, a solid disc for racing is not a very good idea, but if use, becareful where you install the cooling duck. On solid rotors should be install so that it cools both sides, this can be accoplish by placing the duck direcltly in front of the rotor. For vented rotors the duck can be placed on the center of the rotor. wheels are important in the cooling area so choose a wheel that is open.
Paul, I challange the fact about the morris minor and a new car with non-ABS.
There is some validity to that article, yes tires are factor. Beyond that, there is suspension, weight transfer,and weight of vehicle. All critical of the braking design of a vehicle.
I think we are saying the same thing Paul, tires are a big factor and a balance between tire, rotor dia, pad compound, and clamping pressure from the caliper. all of this go hand in hand.
Brakes on a race car are critical, they have to last and brake. They also require lots of maintanance.
On the street brakes have to be strong to last, brakes do not get check that often. A balance between the front and rear is also critical. Now the MGB can use more front brake with the stock rear brakes, either by changing pads (I would use Hawks)or by increasing the braking area of the rotor by imcreasing the pad area, yes this can be done by changing the calipers to a 4 piston.
BTW some race cars adjust the initial bias by changing to smaller rotors in the rear.
A front wheel requires a different set up.
Just bigger rotors do not do the job but combine with softer compound tires they do a great job when they are balance front to rear, and the pad matches the tire compound. This are just the basics for a solid design brake system, there is much more.
As you on a roll, perhaps the 2 Myths here deserve some comment
The Morris minor point is really only to illustrate that if the force of the brakes is more than tyre grip, the wheels lock which then provides less braking than at 10-15% slip (not mentioned in article).
In the UK the Top range performance cars have track use in mind and as such with road tyres, both front and rear are uprated for cooling, but still providing correct front and rear balance.
A short while ago (Topgear car TV prog ) had a BMW for road use with basically slicks, with a warning not to use in wet.
I think we do agree that if you have a choice uprated brakes matched to tyre grip and intended use, is the right way to go. However for a road car perhaps only decent pads with perhaps a vented front rotor should be all that is required. In the UK there is a Wilwood kit which does just that but at a cost.
With regard to pad choice there is a good article from Grassroots, I will try to find link.
This site is well worth reading
|Just a note for those looking to register their cars. Here, if you have a 3.5 V8 in your MGB then you need to have similiar brakes to those in factory produced MGB GT V8's. If you have a 3.9 efiV8 then you need Brakes similiar to RV8's. It might just be beaurocractic idiocy, but there's no argueing with them, they'll just walk away; and so regrettably will you, cause you won't have anything legal to drive.|
Does that apply to rear as well as I think RV8 had smaller drums.
|Guys, i passed up most of what was wrote to just give a few basics of my own:|
*Too thin of tyre:
Not enough rubber on road- brakes will lock up easy.
*Too wide of tyre:
Too much rubber, not enough pressure per square inch. Tyres again will lock up.
*Too hard of rubber for given weight:
Tyres again will lock up easy.
*Too soft of rubber:
Tyres wear extremely fast and hve to be replaced more often.
Tyres lock up again.
Tyres get "greasy" and lock up NOTE Certain compounds and extremely hot days, but not as bad as some might say- Hot days usually increase grip of tyres by a long way.
GIVEN THE CORRECT TYRES--- for the way the car is built, then go for brakes:
*Little itty bitty calipers- lets say MG midget calipers on a Range Rover:
Have to work hard, if master cylinder is built according to caliper size so pedal pressure is not a problem, these will have a difficult time slowing the vehicle down. Once a certain amount of pressure has been applied, these will go from slowing the vehicle down to LOCK UP with not much in between the slow down and lock up.
WAY TOO BIG calipers with brake pads to match:
<A 3 ton truck caliper and pads on a MG Midget>
(assuming master cylinder is correct sizing for proper pedal pressure)
They are too heavy and not worth installation!
If the swept area is increased and the system has more control to the driver, then you should theoretically be able to slow down quicker BECAUSE you have more control to push the brakes closer to the edge before lock up...
Those big calipers are able to push evenly on the pads and the pads with more swept area are able to give more controlled friction... They are able to remove energy (speed) more at a time.
Now big rotors:
Larger calipers and pads are limited to the size of the rotor. Too large a rotor can just be extra weight and come to a decreasing gain on a light car pretty quickly. If the car could use more at higher speeds or due to extra weight or use, this would be good.
Also, bigger rotors can shed more heat. For 98.1% of street drivers, this works. Here in the USA, the only drivers that need that extra huge rotor on the street for an MGB would probably end up on the Television show "COPS" since they are racing from the police on city and highway streets with alot of stressful braking. I would go for big rotors if I could because I also plan a road (closed course) race every few years.
Conclusion for me:
Perfectly matched tyres. Bigger pads, bigger (and lighter) Calipers and rear brakes to match...
Did I mention the correct bore master cylinder for the given system?
Ask a Sprite owner that switched from Drum brakes to later discs without switching master cylinder bore sizes- he will say that the brakes got worse due and probably will not know why!
|BMC Brian McCullough|
If you check our wrc link above, one of myths is that a wide tyre has more rubber on road, also a wide tyre may increase stopping distance.
With smaller callipers/rotors/pistons, you have to apply more pressure but this can be controlled, as long as the driver can apply sufficient pressure, large callipers/rotors/pistons will be on or off. Moving between the two extremes will give the desired control to push brakes to edge.
4 pots should also control lift associated with outgassing especially with different piston sizes
Drums are self energising and use less fluid, so to change to large front and discs at rear to match also needs to consider m/c as per Michel above. Wilwoods are about half weight of OE calliper.
|Paul, Thats my point.|
Too big, or too small is bad for wheels, tyres, brake calipers, pads, and so on.
A bigger rotor gives you more control over getting the brakes to that "Knifes edge" control and when the tyres and wheels, suspension and all the rest match, it helps...
The biggest help:
LEARN HOW TO DRIVE!
|BMC Brian McCullough|
They don't care about the back ones, I asked. Close enough (for the back) is the answer.
Mind you there was some other weird stuff, like the brake lines. You arn't allowed to have braided stainless lines even though they are recognized to be better/safer, got to be just rubber, cause thats what they were first registered with. Later you can go change them.
However thers's a loop hole-if you can find a set with an ADR number on them (the legally required registration number,and almost impossible to get) thats's OK. The guys at MG workshops have found someone to make them, I'm not sure how they managed this.
This thread was discussed between 22/04/2004 and 04/05/2004
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.