fitting big brakes ? read this first!!

[Clan]

the "small brakes " on the T5 would be completely shot after one stop from maximum speed ( 150 mph ) I guess its a compromise with the speed limits here so they cut costs and make them just adequate for 100 mph ..

The rear brakes of a big volvo still offer a lot of useful stopping power due to there still being some weight on them when braking ..

Volvos are extremely stable under hard braking from high speed .
On the other hand you have cars like a Citroen C1 which is over servoed and feels like it is pivoting on its front wheels and the rears doing absolutly nothing under the same circumstances , and feels unstable .
The best braking experience is in a light ( 600kg) rear engined car where brake balance idealy is 50-50 , you can brake with confidence hard into a corner when you need to and the size of the brakes are tiny in comparison ...... Braking is not an effort , its all over in a second or two what ever speed you are doing . Whilst in say a T5 you see people running down hill to a roundabout at 70 mph with their brake lights on for 100's of metres . I just think of the pads burning away , especialy if they do that every day!

[thebigv]

Originally Posted by Simon J

Hmmm....interesting idea.

But I think you'd better read the article first. You wouldn't want them to think you didn't know what you were talking about in your covering email, would you?

I haven't a clue what some people on here are talking about, why would it make a difference. Volvo and brake manufacturers spend millions on development of braking systems, do you honestly believe that laws would permit a manufacturer to sell goods that were unsafe and not fit for their purpose. The overall concern is about friction, laws of physics, brake balance etc. I'm sure that they test them on the applications they are designed for and don't just knock them up in a shed an flog them. Hence why some vehicles you cannot get uprated brakes, a lot is down to demand, mostly its down to such things as development and safety issues. After all why make something that wont sell, and why sell something thats unsafe.

For the applications that braking systems are designed for and lets face it its probably the most important feature on a car, they have to be safe, fit for purpose and designed accordingly to work.

[Simon J]

Now here I agree with you entirely. There are only two brake upgrade kits produced specifically by their manufacturers for the 70 series Volvo - one by Volvo themselves and the well known AP one. But both of these, as you rightly point out, are designed to replace the existing standard brakes and therefore maintain the correct piston area in order to ensure that the ABS isn't confused. Their improved braking power comes from pads with a higher coefficient of friction than standard, and larger diameter discs; and their improved fade resistance comes from bigger pads and bigger and thicker discs.

But can the same be said of the various bitsa kits put together from calipers from one car, discs from another, and brackets made up by a mate? I rather doubt it.

Now, where's my physics book!!!!

[thebigv]

I think you may have been a little confused as to my original comments on this thread, because i never said calipers off one car and discs off another etc I meant matched big brakes for the car. I do apologise if i never made myself clear enough. But I never suggested sticking any brake component on just so long as it was bigger. That would just be idiotic!!!!

My comments initially were like yours, on the amount of fluid. No matter how much fluid you put in a system it'll only hold a certain amount and that volume of fluid creates the pressure which is what i initially said. I then went on to say that bigger discs give a greater surface area etc etc and uprated components can turn more friction into heat to give the breaking effect blah blah. What you have just said in the last post is all I have been saying, but for some reason Physics got mentioned and big brake kits all of a sudden were no good. The laws of Physics basically in relation to brakes say the more heat you can generate and cope with the greater the braking efficiency will be, it will be less resistance to fade etc etc, but this is ony if all components are upgraded, no good with huge discs if the fluid is low or inadequate etc.

The bottom line i think we have all been saying though is if a brake kit was designed for your car,. whether its standard or an uprated version it'll work and is good and wont be worse. So in that respect some comments have been incorrect, However, if you stick veyron calipers on saxo discs your in for a shock. Can we all start a thread on candy floss or something now please cos i'm bored!!! haha No offence meant by this post or any others by the way Simon. I couldn't find a beer! haha

[Simon J]

No offence taken, Big V. I have the Volvo Performance Brakes on my C70 and get weary of the "four pot caliper" brigade waffling on about how single piston calipers are useless, etc., etc., and not really understanding how brakes actually work, i.e the basic physics of force, friction and torque.

But pizza is good!

Cheers,

[Clan]

The only reason Volvo used 4 piston calipers on 140 , 200 and 700 was so that they could have two independant hydraulic circuits . so that you could cut any brake pipe and loose only one rerr wheel .

[Simon J]

Originally Posted by Clan

The only reason Volvo used 4 piston calipers on 140 , 200 and 700 was so that they could have two independant hydraulic circuits . so that you could cut any brake pipe and loose only one rerr wheel .

And that's as it should be - choosing the most appropriate technical solution to a given problem. But that's not what I was referring to in my reference to the "four pot caliper " brigade who seem to value appearance over utility!

[thebigv]

Originally Posted by Clan

The only reason Volvo used 4 piston calipers on 140 , 200 and 700 was so that they could have two independant hydraulic circuits . so that you could cut any brake pipe and loose only one rerr wheel .

They do the same with linked brakes on Honda Pan European and VFR, although most braking systems are cross linked, i.e. Front right, rear left, Front Left, Rear right. Obviously you lose one front one rear but dont know if the 140, 200 and 700 would keep the fronts. But thinking about it they would, one circuit for front and rear, the other for fronts only.

[Clan]

The volvos had a triangle split system , thats why it had dual pistons on the front , the upper set of pistons are one circuit and the lower set the other ( twin brake hoses ) rear wheels are linked to each circuit so you will loose only one rear wheel which wont cause too much havok when you brake .. They also had a stepped bore master cylinder which , if one circuit failed would result in minimal extra travel , thats why they had a PDWV with a warning light , as you may not notice a circuit has failed if you drive gently ..