Brake Pipe Unions

[ArthurH 7]

We are just about to make a new set of brake pipes for the 205GTI.  I have a flare tool; I'll buy some tubing and a bag of unions.  The championship rules constrain us to use the standard calipers and rear cylinders.  To save me checking each one individually, are all the OEM brake threads 'standerdised' across the car (including the master cylinder)?  E.g., M8 everywhere?

Any good tips before I start?

[welshpug 1,666]

Mostly M10x1.0, a 1.9 will have a pair of 12x1.0 into one side of the brake pressure limters

[petert 599]

Can you manage a double flare though? I single flare would surely be illegal? I've approached this a bit differently and changed to 3AN hose where appropriate/possible. Here are some Speedflow part numbers you might find useful:

 

T200-C03 200 series -3 hose Teflon® Stainless Steel Braided Hose

260-03 life saver

380-03 1/8 NPT adaptor

344-03 dual seat

201-03 straight hose ends

https://www.speedflowdirect.com.au/

You probably have a similar supplier in the UK. And if you do it stainless fittings, hose and lines, you'll have no issues with corrosion.

Edited January 30 by petert

[ArthurH 7]

Thanks Peter, just for the avoidance of doubt :-), you are using the braided hose throughout the braking system, i.e., no rigid pipe at all?  If so, the brake pedal feel is not more spongy? 

[petert 599]

No, I use hard lines on the straight parts, but around the difficult to bend parts, I'm using the stainless teflon hose. Even just changing to stainless teflon hose, replacing rubber hoses will improve the pedal feel. I did that on my road 306. I have a friend who did his entire 206 GTi180 in stainless teflon hose and the pedal feel is magnificent.

[ArthurH 7]

I think we may follow your lead and go for a hybrid solution. Picking up from Mei, I think we will have M10x1 throughout - except for the two sides of the Willwood bias valve (1/8NPT?)

[ArthurH 7]

Now I am looking at this in more detail, I am uncertain what sort of 'flare' we need.  Just using these two listings from the same seller as a convenient example, one says "convex" flare, and the other (a different price)  "straight", but I am struggling to see the difference.

 

https://www.ebay.co.uk/itm/146306095109

 

https://www.ebay.co.uk/itm/146103209481

[welshpug 1,666]

Those two fittings look the same to me

 

The typical flare on european cars is a DIN single flare, mushroom shaped, rather than the american SAE bubble flare.

 

You wouldn't buy those fittings to connect to the hard lines anyway, the car side of flexible lines are female fittings with a groove for a clip, the rear lines from body to axle is female both ends other than the left side on a 1.6 that had  a male fitting screwing directly onto a Tee secured to the body on a stud.

 

[ArthurH 7]

Thanks Mei, I was considering following Peter's suggestion above of dispensing with the hard lines altogether, but I'm still undecided.  Can I infer from what you say that they would be suitable to join braided PTFE hose to the calipers, master cylinder and slave cylinders?

[Bremar 5]

I thought double flared brake pipes were the American standard and are the safest, the European standard is bubble flares and single flared are just not safe enough for brake systems. Flaring steel brake pipes is too difficult to DIY in steel so next best IMHO is copper nickel pipes which are harder than copper (which I cant imagine are acceptable in racing but maybe they are ) but still easily bendable. Just buy a flaring tool and practice until you get the double flare right. There are plenty of YouTube vids on making up brake pipes with double flares.

Bremar  
 

Edited February 5 by Bremar

[Bremar 5]

From left to right. Single flare,  double flare and bubble glare. 

[petert 599]

12 hours ago, ArthurH said:

Thanks Mei, I was considering following Peter's suggestion above of dispensing with the hard lines altogether, but I'm still undecided.  Can I infer from what you say that they would be suitable to join braided PTFE hose to the calipers, master cylinder and slave cylinders?

There's a few different ways to connect to the caliper. You could use an M10x1.0 - 3AN flare adaptor. Or direct with a 3AN hose to an M10x1.0 hose end. That hose needs to end at the body fitting. I posted the part numbers above for that.

Edited February 5 by petert

[welshpug 1,666]

Steel is easy enough to work with, you just need a decent flaring tool which are not expensive now chinese clones of the sykes pickavant tool are around.    And to shape it nicely a cheap bending tool helps.

 

Never heard of the european DIN flare not being safe, more than half the world uses it!

[ArthurH 7]

8 hours ago, Bremar said:

I thought double flared brake pipes were the American standard and are the safest, the European standard is bubble flares and single flared are just not safe enough for brake systems. Flaring steel brake pipes is too difficult to DIY in steel so next best IMHO is copper nickel pipes which are harder than copper (which I cant imagine are acceptable in racing but maybe they are ) but still easily bendable. Just buy a flaring tool and practice until you get the double flare right. There are plenty of YouTube vids on making up brake pipes with double flares.

Bremar  
 

Thanks Brett.  I have been flaring rigid pipes for some years, I don't have a problem with that aspect (at least, they don't leak), but my runs of rigid pipe always look very scruffy.  I had always simply copied the flare that was on the pipe I was replacing, so had never worried about names or standards.

 

8 hours ago, Bremar said:

From left to right. Single flare,  double flare and bubble glare. 

This photo is great, not only can I see why each type is named as such, but why they are ranked in 'safety' as you described.  I'm still keen to pursue the 100% hose approach.  Not only will it be smarter, but it will reduce the number of union-to-union joins and be inherently be less prone to any vibration fatigue and give me some flexibility with my bias valve (dash?) mounting. 

 

44 minutes ago, petert said:

There's a few different ways to connect to the caliper. You could use an M10x1.0 - 3AN flare adaptor. Or direct with a 3AN hose to an M10x1.0 hose end. That hose needs to end at the body fitting. I posted the part numbers above for that.

 

I'm sorry Peter, I'm being a bit dense here.  I'm getting more confused than ever with the introduction of "washer seals" which I didn't think I had anywhere at the moment.  To keep it simple, if we just focus on the short Master Cylinder to RH caliper connection.  If that were to be a single hose, would that be a M10 x 1.0 Convex flare at both ends?

[Tom Fenton 1,547]

It takes some thought and planning to work out what fittings you need when doing the whole car

 

To keep it simple. Why not just buy an off the shelf braided flexi line kit, and just pipe the rest in Kunifer.

 

To make the job neater, buy yourself a pipe straightening tool to turn the coil into straight lengths that you can then bend to suit.

[Bremar 5]

1 hour ago, welshpug said:

Steel is easy enough to work with, you just need a decent flaring tool which are not expensive now chinese clones of the sykes pickavant tool are around.    And to shape it nicely a cheap bending tool helps.

 

Never heard of the european DIN flare not being safe, more than half the world uses it!

Hi welshpug

I think the “European din flare” is what the Americans originally had as the double flare. The safest flare. Don’t think it’s a single flare. But it is all a bit confusing and quite a while since I flared my last car. 

[petert 599]

I haven’t found the part to go direct into the master cylinder yet. ie mc-3AN. That doesn’t mean it doesn’t exist. 

[ArthurH 7]

On 2/5/2025 at 8:21 AM, Tom Fenton said:

To keep it simple. Why not just buy an off the shelf braided flexi line kit, and just pipe the rest in Kunifer.

Thats where we are with the current car, the four brakes are on Goodrich braided hoses.  It was my repeated inability to do a decent looking job with Kunifer that had me intrigued by Peter's comment above: "I have a friend who did his entire 206 GTi180 in stainless teflon hose and the pedal feel is magnificent."

On 2/5/2025 at 8:21 AM, Tom Fenton said:

To make the job neater, buy yourself a pipe straightening tool to turn the coil into straight lengths that you can then bend to suit.

I wasn't aware this was even a thing (shows how out of date I am).  I have watched some of the YouTube videos and am Impressed.