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MG Midget and Sprite Technical - Flexible brake and fuel lines

Afternoon gents,

My mind has been wandering...

Is there anything in the MOT rules that prohibit you from using braided flexi hose for the entirity of your brake/fuel/clutch lines?

Or any other reason why this is not a good idea?

Cheers,
Malcolm
Malcolm Le Chevalier

Not sure if there is a rule, but the longer the pipe the greater oppourtunity for expansion.

Solid are just that, flexi are soft, and can expand. So I would say only use flexi in limited lenth runs for the brakes.

For the fuel, I would say it's ok as long as it is well protected.
Lawrence Slater

If it is braided hose it won't swell thought will it? (Based on the talk of everyone saying how hard their brake pedal feels after they put braided hoses on!)

Or is it just stupid because it is expensive?!

Malcolm
Malcolm Le Chevalier

I don't think I would use it Malcolm. It may be an improvement of normal rubber brake hoses - which is why people say it gives a firmer pedal, but it is also liable to abrasion and the braiding will damage if it is constantly rubbing against line clips and that sort of thing. I think cupro-nickel for fixed and braided for the flexible bits is the way to go. Braided may be OK for the shorter clutch pipe though. Main thing with the clutch is to add flexible pipe and remote bleed nipple though!
Guy

Yeah, I'd tend to agree with Guy on that one, also the cost might well be extreme.

How long does the cupro-nickel stuff lasts compared to flexi bits? I'd assume quite a bit longer. The braided might well expand less than rubber but probably more than cupro nickel

I used solid for the fuel for as much as possible, they have a nasty place to live under the car with bits of gravel and things knocking about.

Also not sure if flexi line the whole way down would count as a 'modification' I'm always a bit cautious when it comes to brakes...

Rob Armstrong

Why do you want to do this?
Daniel Thirteen-Twelve

Braided flexible pipes are better than non braided, because they help the rubber pipe resist the expanding forces of the fluid under pressure, and therefore improves the hardness of the pedal.

However, you are talking about replacing the entire length of the brake lines.

The ideal hydraulic brake system would use only hard tubing such as galvanized or stainless steel pipe, as this would prevent any expansion along the hydraulic fluid path, providing the most direct transfer of operator input force to the friction surfaces. The flexible pipes at the ends of the lines are there to allow for movement, so you can't have hard pipes for the whole length. The flexible is a compromise.

Replacing just the non braided rubber for braided is ok. But to replace the entire length on the brakes isn't a good idea, if only for the above reason, let alone any of the others described.

Lawrence Slater

The other issue with braided is not being able to see any degradation of the hose.
Dave O'Neill2

I am not "replacing" anything. I don't have any lines of any sorts! They got mangled/broken/chopped/binned when stripping the car.

The prompt for this thinking was that I saw the price of a fuel line kit from MGOC was around £50! In comparison flex hose is under £3 a metre.

The thought then turned to brake lines too.

Also the racer I built used all stainless braided hose so it is what I have used before.

Malcolm
Malcolm Le Chevalier

Wow, that sounds a bit pricey!

Try Stevson Motors...

http://www.stevsonmotors.co.uk/Fuel.html
Dave O'Neill2

Cheapest way is to buy a flaring tool, a coil of pipe and some end fittings.
Guy

and then spend a happy couple of hours flaring things without remembering to put the special nuts on first.
Rob Armstrong

haha LOL
Dave O'Neill2

Malcolm. I don't know about the MOT implications, but as mentioned above, braided lines are less likely to expand than ordinary rubber hoses, but they will still expand a little and over the great length involved in using them for the whole car I doubt very much that you would even get any kind of pedal and at the very best it would be horribly spongey. I'm afraid that even if there is no specific MOT rule regarding long braided brake lines, it would fail on excess pedal travel. Don't do it.

Bernie.
b higginson

Just how much does any sort of brake pipe expand when new? Hardly at all, regardless of it's type. It's only old(er) hoses that can balloon, new ones won't. The difference in pedal feel will be so minimal, assuming that's the only change, that you would have to now the car perfectly to notice even the smallest difference. There are some racers using SS braided end to end and if it didn't work it wouldn't be used.

The only MOT point as far as I know is that the pipes must be secure, of the correct type and of good condition. SS braided and copper/kunifer will be fine regardless of length.

However, proper braided hoses are expensive. The £3 a meter stuff almost certainly won't be the right stuff for brakes. To give an idea of price the MGOC want £33.25 for a car set of 3 braided hoses. To do the whole car will cost £100s. It's easy enough to fit so it won't rub, but you'll need quite a few rubber lined P clips to do it and need to be sensible about pipe routes and curves.

My choice would be kunifer piping for the main brake runs with SS braided for the flexis to the calipers and the axle. I'd probably use the same for the fuel lines, only a bigger bore pipe. There's no real need to use SS braided hose for the fuel lines, but it does look good if fitted neatly and will give you the correct ends for whatever parts you choose to fit. I'd go this way not because of any difference to pedal feel, but because it's much, much cheaper!
S Overy

Another shout here for cupro nickel lines.

Re MOT... not 100%... but I don't think you'd get away with it.

Re Safety... the rules are to use as long a section of rigid piping as you can (this is very strict on new builds)

Re Cost... other than tooling costs, it won't be any cheaper to go braided (plus I don't know how you attatch unions or other fittings to braided pipes - but you probably need a tool for that anyway)

My reccomendation is to get a roll of CU/N brake line from ebay - £15 (comes with 10 of the 3/8 unf unions you need) - buy a load of p clips (£2-£3). Bend it over your knee, or by hand (£0)... and get a good quality flaring tool (£expensive). Do not buy a Silverline corkscrew type one... the flares will be rubbish... I made this mistake... total waste of money. I borrowed a friends flaring tool (a Mo Prod easy flare) and it is genuinley fantastic. They come up on eBay every now and again and go for around £40... well worth it.

Making brake pipes, suprisingly is good fun.

C
C L Carter

Correct braided steel lines for an entire length of brake hose including replacing the rigid hose isn't 'horribly spongy'.

Nor do you need to use it.

Daniel Thirteen-Twelve

This thread was discussed between 24/02/2012 and 26/02/2012

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