Brakes - 280 to 302mm

[mraldonnelly]

Afternoon all,

Question re brakes.

If soing the discs and pads all round and upgrading to 302mm at the front with stainless braided hoses, would it make any difference whether or not the rubber hoses at the back were changed too?

I don't mean in terms of hose length, the only thing changing at the rear is aftermarket disks and pads so the hose length isn't an issue. What I'm wondering is if braided hoses on the front would have any adverse effect on the rear rubber hoses because there would be less give in the front hoses.

I'd shouldn't imagine so but just thought I'd check opinions first. It's just that the upgrade kit from PFV contains front hoses but I don't think rears are available separately.

Cheers folks.

Andy

[Straker]

Shouldn't have an adverse affect but braided hoses give you a more solid brake feel because the hoses don't expant so much under pressure.

only replacing 1/2 the hoses will only give you half the benefit. System will work fine though.

[mraldonnelly]

Shouldn't have an adverse affect but braided hoses give you a more solid brake feel because the hoses don't expant so much under pressure.

only replacing 1/2 the hoses will only give you half the benefit. System will work fine though.

That's what I thought but wondered whether or not the lack of expansion of the front hoses would put additional strain on the rear hoses thus causing them to fail. I shouldn't imagine it does, as I reckon it will just increase the efficiency on the front brakes while the efficiency of the rear ones remains as normal.

I'm trying to think of a comparable example of what I'm trying to say but can't for the life of me think of one!

Regards

Andy

[Wobbly Dave]

The brake lines on the rear are all solid anyway. The lines run along the trailing arms and as such dont need to flex.

[Al115]

Mine weren't! There are 2 flexible lines at the rear of my V70 P1.

[racer]

Andy, You'll be fine. Lets simplify things here, imagine your brake callipers as four bicycle pumps, all connected by hoses to a fifth bike pump. Now imagine everything is full of hydraulic fluid (DOT5.1 is good!). To simulate pressing the brake you shove the fifth pump closed. All the other four open by a quarter of the amount as the fluid moves into them. Get the picture?

Right, now we add some resistance to things and wedge our four "calliper pumps" between say a wall and a large heavy block. You shove in your brake pedal pump and your calliper pumps exert pressure on the block. If you really shove hard, the block moves.

The pressure goes up the harder you push. Hold on, I am getting to the point. So, consider what happens if two of your calliper pumps are on expanding hoses and two not. The expanding hoses swell as the pressure goes up, but the pressure is the same throughout the system, so you are still putting the same amount of pressure on the block, evenly distributed through each calliper pump. All that happens as the pipes swell it that the volume of the system goes up, so you need to shove your brake pedal pump in further to reach the same pressure that you'd get if the hoses didn't swell.

This is the "feel" improvement that every one speaks of. If you stay with standard flexible hoses at the rear, you will get a bit over half the feel improvement (rear hoses are shorter), but everything will still work fine, as you see the same pressure throughout the whole system.

Hope that helps!

Right, now someone else can explain biasing valves.......

[BigJC]

Andy, the front's on mine are still the rubber ones coz I've not had chance to get into the garage yet so don't be worrying about me! ;)

I was gonna get the rears too before it goes in hopefully a week on Saturday!

They're soooo much better then before, cheers again!

[racer]

Oh, and Dave, He's on about the flexibles at the rear between the trailing arms and the chassis. (I think!)

[Engineer]

Right, now someone else can explain biasing valves.......Well explained Racer, but if Andy keeps his ABS he won't ever need to know lol.

[mraldonnelly]

Cheers folks,

Racer, that's one hell of an explanation. The outcome is what I expected, thanks. Basically what you're saying is that no additional pressure is exerted on the rears just because the fronts are more rigid (this is what I'd guessed but was slightly concerned that if more rigid hoses were used on the front then it would cause excess pressure at the rear and thus the possibility of bursting the rears.

Wobbly Dave, it's the flexible hoses between the trailing arm that I was concerned about, sorry, I didn't mean the copper pipes into the caliper.

BigJC, someone else has asked about brakes but are going to do all four (inc hoses) and it all of a sudden made me think "£££££, I DIDN'T THINK ABOUT THAT POSSIBILITY". Glad you're brakes are feeling better. Is the stopping power more noticeable than before?

Regards

Andy

[BigJC]

Glad you're brakes are feeling better. Is the stopping power more noticeable than before?


Yep, although I've not been making the jump to lightspeed until I get new rears and matching braided hoses! I have had a few occaisions to hit the middle pedal hard but all at less than 50mph and it certainly feels a lot better.

Heading back to lakes for half term so I'll be able to give some decent feedback then!