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Any reason you can't run single braided brake hose from MC to calipers

mads - 3/9/19 at 06:08 AM

As the subject says really.

In the process of mapping out the brake pipes to place order for braided hose and couldn't find on here where there has been single runs from the master cylinder to each of the calipers without any breaks (rear would need a splitter and also need to put a sensor switch inline).

Has anyone done this? If so, what did you do for the front section coming out of the panel work to stop it rubbing or moving in/out?

Cheers,

russbost - 3/9/19 at 07:11 AM

Can certainly be done, depending on how many outlets from the master cylinder you may need a T piece to split at each end.

In terms of stopping things rubbing, I run my hoses thro' a rubber grommet anywhere they go thro' panel work & if there is a possibility of contact anywhere with suspension etc simply place a section of split rubber tube secured neatly with cable ties over the offending section

Talk to Ollie at Furore Products info@furoreproducts.co.uk is usually better than ringing or take a look at the "hose builder" on their website
Linky
to see what they'd cost you - Ollie can usually offer a small discount if you're dealing direct rather than thro' Ebay or website

Sam_68 - 3/9/19 at 07:20 AM

I had a Raffo Tipo 12 where the builder had done this.

Worked fine, and passed several MOT's in my hands. I was surprised that over long runs, the small amount of flex in even braided hoses didn't result in a slightly spongey pedal, but it seemed OK.

Still seemed a strange thing to do, though, and I can't see any benefit over rigid lines, unless it's a very short run from your m/cyl to front brakes.

russbost - 3/9/19 at 07:30 AM

The reason there is no spongy pedal is that there is no more "give" in a braided line than there is in copper

3 reasons for doing it :-

it looks a lot prettier than copper & looks neater when fitted - available in multiple colours/finishes

it's easier to route around obstacles, particularly for an inexperienced builder that might kink a copper line

the less joins you have, the less potential leak/failure points you have

reasons for not doing it :-

it's a little more expensive

it's a fraction heavier

Sam_68 - 3/9/19 at 07:39 AM

quote:
Originally posted by russbost
The reason there is no spongy pedal is that there is no more "give" in a braided line than there is in copper

That genuinely surprises me.

Logic suggests that there should be some slight give in the weave (or they wouldn't be flexible, for a start - if you bend them, the inside radius is obviously going to be shorter than the outside radius).

But yes, the actual evidence was that they were acceptable.

russbost - 3/9/19 at 08:01 AM

quote:
Originally posted by Sam_68

quote:
Originally posted by russbost
The reason there is no spongy pedal is that there is no more "give" in a braided line than there is in copper

That genuinely surprises me.

Logic suggests that there should be some slight give in the weave (or they wouldn't be flexible, for a start - if you bend them, the inside radius is obviously going to be shorter than the outside radius).

But yes, the actual evidence was that they were acceptable.

Not gonna argue with you Sam, if you don't believe me talk to HEL who used to supply me & where the info comes from. Part of the answer is that inside the braid is a rigid PTFE liner. I don't follow the logic of the bending/radius argument if you bend a copper line is the inside radius not shorter than the outside? Therefore the metal is flexible & can stretch, simple answer is the combination of PTFE/stainless braid has no more "give" in it than copper, certainly not in terms of any practical difference & totally unlike rubber flexy hoses, which most certainly have some give in

Sam_68 - 3/9/19 at 08:08 AM

quote:
Originally posted by russbost
Not gonna argue with you Sam...

Not arguing Russ - just expressing, as I said, genuine surprise.

But, as I said, yes, I've owned and driven a car with all-braided lines, and it was fine.

The difference with a rigid line is the difference between elastic and plastic deformation.

Sam_68 - 3/9/19 at 08:45 AM

To add:

Out of interest, a bit of Googling provides some numbers, if anybody cares:

Kunifer rigid brake lines expand to the extent of 0.15mm3/Mpa.m

Braided hoses expand to the extent of approximately 2mm3/Mpa.m (so are roughly 13 times worse than Kunifer).

Fabric reinforced rubber hoses expand to the extent of approximate 30mm3/Mpa.m, so are roughly 200 times worse than Kunifer and, coincidentally, roughly 13 times worse than a braided hose).

I couldn't find a definitive figure for copper (possibly because it work hardens, so will be variable in any case?). Possibly not much different from braided steel, though?

So the theoretical answer is that braided hoses are a lot worse than (Kunifer) rigid lines, but still massively better than flexible hoses, and (from personal experience) not detectably worse than rigid lines over the lengths and pressures typically used in a braking system.

mads - 3/9/19 at 11:54 AM

Thanks Russ. Got 3 outlets on the MC - presuming 2 for front and 1 for rear.

I was looking at Furore website in terms of sourcing them so will give Ollie a shout. Cheers.

quote:
Originally posted by russbost
Can certainly be done, depending on how many outlets from the master cylinder you may need a T piece to split at each end.

In terms of stopping things rubbing, I run my hoses thro' a rubber grommet anywhere they go thro' panel work & if there is a possibility of contact anywhere with suspension etc simply place a section of split rubber tube secured neatly with cable ties over the offending section

Talk to Ollie at Furore Products info@furoreproducts.co.uk is usually better than ringing or take a look at the "hose builder" on their website
Linky
to see what they'd cost you - Ollie can usually offer a small discount if you're dealing direct rather than thro' Ebay or website

loggyboy - 3/9/19 at 01:15 PM

Just to add my 2p - I would also expect rubber/braided to degrade quicker than kunifer/copper. Similar (but not as bad) as fuel lines. Most say hard lines for as much as you can, and rubber to do the flexible jointing areas.

russbost - 3/9/19 at 04:07 PM

quote:
Originally posted by loggyboy
Just to add my 2p - I would also expect rubber/braided to degrade quicker than kunifer/copper. Similar (but not as bad) as fuel lines. Most say hard lines for as much as you can, and rubber to do the flexible jointing areas.

The Furore Products braided lines (HEL) are guaranteed for life! Never been sure if that means the life of the vehicle or the life of the owner, but either way I'd be fairly surprised if copper or kunifer could outlast that!

rodgling - 3/9/19 at 05:23 PM

As an experiment, I once disconnected all my callipers, blocked off the braided hoses and bled the system. Pressing the brake pedal was like pressing directly on the bulkhead - I could feel no give whatsoever in the pedal.

MikeRJ - 4/9/19 at 05:09 PM

Dad used to work in a garage dealing with classic MGs and a customer brought a Midget in that he had plumbed throughout with aeroquip hosing for the brakes. He couldn't get a decent pedal despite extensive bleeding, and neither could my dad, despite all the usual tricks. Replacing all the relevant parts with cupro-nickel hard line fixed the problem immediately.

russbost - 4/9/19 at 05:58 PM

quote:
Originally posted by MikeRJ
Dad used to work in a garage dealing with classic MGs and a customer brought a Midget in that he had plumbed throughout with aeroquip hosing for the brakes. He couldn't get a decent pedal despite extensive bleeding, and neither could my dad, despite all the usual tricks. Replacing all the relevant parts with cupro-nickel hard line fixed the problem immediately.

I don't know what the problem was, but I can assure you it had nothing to do with the braided line per se, there may of course have been a faulty/damaged line bulging under pressure, but otherwise there is no way flexy braided hose could have that effect. I've built several Furore's with flexy lines all thro & brake pedal has about 1cm of movement!

peter030371 - 5/9/19 at 11:05 AM

Don't some race cars use flexi all through and is often quoted, rightly or wrongly, as a positive selling point?

loggyboy - 5/9/19 at 12:39 PM

quote:
Originally posted by peter030371
Don't some race cars use flexi all through and is often quoted, rightly or wrongly, as a positive selling point?

But they are wrapped in cotton wool when away from track, do limited millage and are stripped and rebuilt on a semi regular basis, certainly at high levels, which are generally levels where the and regs would allow complete brake systems to be replaced and cost/benefit level would be acceptable.

peter030371 - 5/9/19 at 01:48 PM

quote:
Originally posted by loggyboy
But they are wrapped in cotton wool when away from track, do limited millage and are stripped and rebuilt on a semi regular basis, certainly at high levels, which are generally levels where the and regs would allow complete brake systems to be replaced and cost/benefit level would be acceptable.

That is very true

Doctor Derek Doctors - 5/9/19 at 02:49 PM

I have used flexi lines throughout on all of my car builds, there is absolutely no way you could feel a difference in the pedal if they are all bled properly. I tend to run a "pressure" pedal set up with very little movement (large) MC and they are always rock solid, no spongeyness at all.

We use the same stuff at work to for F1 throttle and waste gate actuation systems, if there was any spongeyness or response lag it wouldn't be used.

From experience working on many peoples cars the biggest cause of a spongey pedal is flexing of the bulkhead, pedal mounts and pedals themselves, you can't get a decent pedal feel when the master cylinder can move 5mm as the bulkhead flexes!

Russ made all the points of the advantages, there is one more advantage which is probably only relevebt to race cars; if doing a rebuild you can remove the entire brake system without having to brake and seals or release the fluid

JimSpencer - 5/9/19 at 04:21 PM

quote:
Originally posted by loggyboy

quote:
Originally posted by peter030371
Don't some race cars use flexi all through and is often quoted, rightly or wrongly, as a positive selling point?

But they are wrapped in cotton wool when away from track, do limited millage and are stripped and rebuilt on a semi regular basis, certainly at high levels, which are generally levels where the and regs would allow complete brake systems to be replaced and cost/benefit level would be acceptable.

The ones on my 88 Reynard are, as far as I can tell, the original ones.. they might not do a huge mileage but they get plenty of use when they are out there..

All the race cars I've had/worked upon across use(d) flexi throughout (that's not to say that there aren't loads that do mind..) I've never seen anybody change flexi pipes for any other reason than damage unless doing a complete, chassis up, rebuild.

Certainly pedal feel isn't an issue what-so-ever and I'd have no hesitation on using them for a road going installation, but it's an interesting question if there's actually any benefit (over copper) other than it's easier to do a neat job!

AdamR20 - 6/9/19 at 08:52 AM

quote:
Originally posted by Sam_68
Kunifer rigid brake lines expand to the extent of 0.15mm3/Mpa.m

Braided hoses expand to the extent of approximately 2mm3/Mpa.m (so are roughly 13 times worse than Kunifer).

My experience corresponds with this. Same car, same brake setup, only swapped the lines from hard (except the flexies to the calipers, obviously) to stainless throughout - brakes became very mushy.

Note this was an MX-5 with a brake servo, I have been able to get very solid brakes on my Westfield with stainless throughout - albeit with twin 1" master cylinders and no servo, of course.

[Edited on 6/9/19 by AdamR20]

Doctor Derek Doctors - 6/9/19 at 09:53 AM

quote:
- brakes became very mushy.

That will be air in the system then. Your brakes won't go "very mushy" just from different lines, likely the act of changing them introduced some air.

When I changed the lines on my truck (to new hardliners) they were appalling for ages, bleed after bleed after bleed until finally a pocket of air emerged and they were fine.

There needs to be some recognition of "correlation doesn't mean causation" a lot of the complaints seem to be (on multiple forums) "I changed to flexi and the brakes became rubbish so the flexi hoses must be rubbish" much more likely is that the act of changing the lines has filled the system with air that has not been bled out.

[Edited on 6/9/19 by Doctor Derek Doctors]

AdamR20 - 6/9/19 at 04:36 PM

I respectfully disagree.

phelpsa - 7/9/19 at 06:46 AM

Braided ptfe hoses are significantly less stiff than metallic hard line, however in your average kit car braking system the lines are only a small proportion of the compliance, most of it being in the calipers. Line pressures are so low that realistically most people wouldnt notice.

One of my first jobs as an engineer in motorsport was to measure the compliance of various parts of the braking system. That car ran extremely high line pressures and very stiff calipers which meant that most of the compliance was in the flexi hoses. We made a good improvement on hydraulic stiffness by putting hardline wherever possible.

Our westfield has hardline to the front and rear t-pieces then flexi out to each wheel and has no problem.

AdamR20 - 7/9/19 at 09:42 AM

Thanks for clearing that up Adam.

As I said, in my case, it was on an MX5 with a brake servo of ratio 7:1 and a tandem master cylinder - ie. much higher line pressures than our kit cars, especially with twin master cylinders. It was very noticeable.