Top Trumps - Brakes

[Guest Gargoil]

790Kg with 304mm front and 4 pot calipers. Obviously the wrong brake ratio because they are crap.

I'm sure its the prayers that slow the car down.....

[maccavvy]

That's some serious available stopping power..

 

I've only got 350 mm and 4 pots on my 1.6 ton monaro and it's very good and stopping

[Guest 2b cruising]

Not wishing to start any argumentss but :- the vents that are between the dual sided discs are puposelyshaped and really do act as a pump, pressurising the air they are pumping inside the disc.

This gives it only one route to go and that is through the Holes.

Two other things to consider also.

If you know anything about carburettors, you will have the comon to realise that air passing over any hole causes a vacuum. This also aids the air escape from inside the disc through the drillings because of the vacuum effect.

Finally, if the air was just trapped inside the discs by the purposely shaped paddles, that air itself would get to the same temperature as the discs. Now where would be the aid to cooling be then, until of course the discs stops spinning.

Someone also stated that grooves shave off the pads. WRONG.

How long would a two stroke engine last if the piston was continually shaved by the ports let into the cylinder bores. Especially when you take into consideration the spring pressure from the extremely hard piston rings would be trying there upmost to nip away at the edges of the ports.

Accurate engineering and the pads having more surface area on the flat part of the disc at all times therefore nullify the shaving effect.

If shaving was to happen, the grooves would very quickly fill with hard compacted brake dust. Has anyone on the forum truthfully ever found this, because in my 67 year life I have never seen that effect.

Sizes.

Somebody mentioned about fitting a smaller bore master cylinder would give an increased pressure and brake effort. CORRECT.

That same person also stated bigger front discs would not help.

How could that possibly be if the first statement about smaller master cylinder bores and pistons giving greater applied pressure is correct.

Consider this.

If the discs are bigger, the pads are bigger and the system Ford uses, so would the size of the calipers and pistons.

This works down to the same amount of pressure would be felt between the friction surfaces as on the smaller discs set up.

However that friction surface would be far greater than the smaller discs set up.

Therefore, why would you not get greater braking effort.

If you are an experienced road driver, never mind an even better track driver, you will automatically get used to the brakes and required manual effort to get your required reaction from the braking system.

Unless of coarse it is impossible to create enough force on the actual brake surfaces.

This would be either through bad design, bad fitment, wrong choice of braking material or mechanical fault.

Personally. I feel Dino's fault lies in the lining pad selection being wrong for his around town driving. I don't feel he is getting the needed friction effort between the shoes and drums. His shoes are either to hard and not getting up to required temperature, or to soft and have burnt and glazed over.

It would not hurt to fit the 258mm discs and calipers at all as long as the rear drums were increased to 9" id drums and shoes.

Everything would then be matching and because of the greater effort required to apply the brakes without a servo, would be somewhat less due to the bigger caliper pistons and bigger wheel cylinders in the drums.

Dino, don't infer I'm a wuss again now I have done this you numpty. Alway bloody trouble causing you little imp.

 

[speedtripledan]

This is why my brakes are good, as said before i learnt my lesson on tbe 2b i spent out on bigger brakes mintex pads rear disc conversion and still had *bleep*e brakes. It was when i changed the pedal box that things improved. Hence fitting this to my stylus http://www.demon-tweeks.co.uk/Product.do?method=view&n=1723&g=731585&p=731589&d=124&c=4&l=2&utm_source=Google&utm_medium=Base&utm_campaign=Pedal%20Box%20Assemblies%20&%20Balance%20Bars&gclid=COjh-M_-qs0CFYEy0wodZ58Ngg

[Guest lotusPaul]

Someone also stated that grooves shave off the pads. WRONG.

 

I said that and its based on experience.

 

Back in mid 1990s several magazines almost encouraged the use of cross drilled grooved and ventilated disks for most people with an RS turbo, 205,Sapphire Cosworth ect.

 

It was very well documented that at low temps,these combinations DID glaze the pads and the groves DID fill up,along with the cross D rillings, to the point where the disk was smooth and these were therefore ineffective.

 

I was part of this scene for some time and built up a fwd 400hp turbo nutter car. Yes it had everything i could possibly do to it Inc uprated brakes in 18in wheels. I made it my point to fit bigger brakes then the current touring cars.

 

Yes it was wrong, yes it glazed the pads, yes I spent thousands on wasted kit and yes it was stupid and probably dangerous.

 

So, NO I don't want people to make mistakes I made and waste hard earned money.

 

Since those days I have a motorsport engineering degree and now working on a mechanical engineering degree. I have also spent most of my military career within the Army motorsports association and created the team that now races in Thundersport GB.

 

I don't believe in just bolting on something that someone else has, just because that bloke in the paddock has it, doesn't mean its correct for every purpose.

 

Motorsport and engineering mathematics do not lie.

[brumster]

Is this the full-blown argument, or just the 5 minute one

 

Not wishing to start any argumentss but :- the vents that are between the dual sided discs are puposely shaped and really do act as a pump, pressurising the air they are pumping inside the disc.
This gives it only one route to go and that is through the Holes.

 

I think you'll find this is incorrect. They draw air through the centre of the casting, on the back face (and also through the front if you have your bells machined to give some clearance around the holes) with the primary desire to push the air out the circumference of the disc, not through the holes. A fair portion of the disc (maybe 25% of each side?) is probably obscured by pads and calipers anyway! Well, put it like this, that's how people working at BG Developements, who I trust very much in terms of brakes, explained it to me, and it seems reasonable. And even a brief google search supports this. However I will concede I've not done flow analysis of air through discs personally, so I guess I could be talking utter crap

 

 

Someone also stated that grooves shave off the pads. WRONG.

 

You're paraphrasing somewhat, but they are a mechanism for deglazing the pads, for cleaning the surface. If you want to call that shaving, so be it, but shaving makes it sound rather harsh...!

 

 

Somebody mentioned about fitting a smaller bore master cylinder would give an increased pressure and brake effort. CORRECT.
That same person also stated bigger front discs would not help.
How could that possibly be if the first statement about smaller master cylinder bores and pistons giving greater applied pressure is correct.

Assuming we're talking calipers here and not drums, to keep it simple - go down a bore size on the m/c would increase the pressure at the caliper end.

Likewise going larger on the caliper piston would achieve the same thing.

Disk diameter is an entirely different thing. Disk diameter alone has got nothing to do with changing brake effort.

I was talking purely about upping the m/c size in isolation.

 

 

If the discs are bigger, the pads are bigger and the system Ford uses, so would the size of the calipers and pistons.
This works down to the same amount of pressure would be felt between the friction surfaces as on the smaller discs set up.
However that friction surface would be far greater than the smaller discs set up.
Therefore, why would you not get greater braking effort.

You're equating pad size, where you should be considering the total piston area at the caliper end. They are different things. You're making an assumption that bigger pads and discs means bigger calipers and means bigger pistons, which is *probably true*, I'll grant you, but it's an assumption. My point was disk size isn't the main thing to be worried about here. A bigger disk will give the pads a larger radius to clamp up on, basically increasing the leverage the caliper can enforce on the axle, so yes - bigger brakes can certainly give more braking force. But my point was, on cars like ours, you should be able to effect more than enough force on a 240mm disc to lock up a wheel with only 600-odd Kg of intertia behind it. Sticking 280mm discs on it is just overkill.

 

 

Unless of coarse it is impossible to create enough force on the actual brake surfaces.
This would be either through bad design, bad fitment, wrong choice of braking material or mechanical fault.

 

Absolutely, completely agreed! And that's my point; my old Exmo certainly weighed more than most Robin Hoods and it could easily lock up a wheel on completely standard 240mm Ford Sierra braking system all round; drums on the rear, standard pads, with the exception of the master cylinders, that were the aforementioned Girlings on an OBP pedal box.

[Guest 2b cruising]

I stand corrected on the air flow.

However I stated that changing to bigger discs that larger caliper,would be used.

Seeing that larger pads are then used the actual pressure on the friction surface would be the same, but the braking effort would then be greater that with smaller pads and pistons.

[brumster]

Sure, I see what you're saying. Forgive me for labouring the point , but I really wanted Dino to understand, but to go through the whole pain of bigger discs, bigger calipers and bigger pads (even if the piston area stayed the same) just to effect a greater braking force for the same pedal effort - while valid - was quite a long way to go about things. If all he wants to do is increase braking force for less pedal effort, there are other things he should look at first (IMHO), such as m/c size, caliper piston size (I think there are 2 Sierra sizes if memory serves me correctly?) and pedal pivot. I know you've mentioned that above, so I'm not disagreeing with you, just wanted to make sure the message to others was clear .

 

And again that's assuming everything in the system is in tip-top condition, of course!

 

Sorry for warbling on

[Dean Roberts]

Wow....light the fuse-wire and watch the fireworks....

 

That's a little bit heated, but a great debate....

 

All the information is extremely useful to myself and anybody who ventures onto this forum for help.

What can I say, you guys are funny, great and informative all rolled into a shiny RHOCaR tin that does exactly what it says on the label.

 

There's nothing better, than to read peoples views on 2 different products.

Amazing how much you guys have "been there, done that - worn the t-shirt" and being such informative, nice guys continue to help others and try to stop them from wasting money and making the same mistakes..

 

 

Quote - "Dino, don't infer I'm a wuss again now I have done this you numpty. Alway bloody trouble causing you little imp"

I try my best Ken , but don't worry, you DO NOT offend anybody personally, you just a have an opinion and your own personal experience that needs expressing.

This what makes a great forum....Debates and opinions on different ideas and products.

 

Thanks guys, I better keep my head below the parapet next time I start a Top Trumps War

[brumster]

Thanks guys, I better keep my head below the parapet next time I start a Top Trumps War

 

I can see it now.

 

[Dean Roberts]

Agree with Dan.....

various pedal ratios here between 5.1:1 and 7:1

 

http://www.rallydesign.co.uk/advanced_search_result.php?keywords=brake+pedal&x=11&y=12&osCsid=ua4pgpple2hq1a1ebrth19b253

 

I gather this is where the pedal ratio is important:

 

Formula for Pedal Ratio:

Pedal ratio is the ratio of leverage your clutch pedal applies to the master cylinder. To determine the pedal ratio you need to measure the height of the pedal to the pivot point then divided the measurement of the pivot point to the lower arm that controls your rod to the master cylinder.

 

A = height of pedal B = center to center measurement of the lower arm

 

C = pedal ratio A divided by B equals C Or example 9″ divided by 1.5″ equal 6 to 1 ratio.

Double Click Image for Full View.

 

If you apply 100 pounds of pressure to the clutch pedal, 100 pounds X (6 to 1) = 600 pounds of pressure. So, if the clutch pedal has been modified from its’ original design the pedal ratio is effected drastically. You can now see the pedal ratio is a “multiplier” of the pressure you apply with your foot, because this is the leverage that is applied to the master cylinder.

Now, take this same formula and substitute 2″ instead of 1.5″ you end up with a 4.5 to 1 ratio. Multiply 4.5 times the 100 pounds of applied pressure and you get 450 pounds instead of 600 pound. That half inch cost you 25 percent of your clutching power. The same thing applies when you shorten the upper measurement.

[brumster]

Yup, that's it. We could get pedantic about minor details but that's the gist of it . Obviously remember with an increased ratio comes more travel. So applying more pressure by shortening B, you'll be pressing the pedal further. As with all these things, it's sometimes a compromise/personal preference on feel.

Edited June 16, 2016 by brumster

[keith kelly]

get direct replacements for the existing and get the car back on the road and stop messing about!!! upgrade over winter!

Edited June 16, 2016 by unclechief

[Guest mower man]

There is a distinct smell around to much bull poo recon the brakes properly and you should not need any thing bigger than 268 rotors vented or not if it is road car ,if a super power full track you will have to spend the money . I ran for 10/11 years on 268's with hi-spec budget calipers, caravan rear linings and 9 inch drums fast runs across France in summer heat NOPROBS MICK

[Bob Tucker]

Rays corvette uses Capri front struts, standard Capri vented discs, Wilwood 4 pot calipers,

and a special compound brake pad & stops very well from about 140 to 20.

The pads need to be able to soak up a lot of heat in a very short time & to grab immediately

without needing to warm up first

 

From 190 to 140 is taken care of by a big red parachute........would that help, Dino?

 

Ignore the smoke.....thats £14,000 going up in smoke...hence the slow time & low speed

due to just 5 & 1/2 pistons, and one head

Edited June 16, 2016 by Bob Tucker