2CV Brake upgrade

DoubleChevron said:
The brakes don't circulate on any Citroen I know of. Bleed the brakes!!!! I bet you get black, moisture filled "stuff" come out (I have no doubt a 2cv is worse as moisture will just drop to the lowest point. In a hydraulic car it may well get boiled off as the hydraulic system heats up :unsure:

When I bleed the hydraulic cars, I usually bleed into a glass jar ... until I get bright green fluid through. I'm not bleeding air out, I'm bleeding the probably 50year old fluid out of the brake lines!

You could change the cars LHM annually .... but if you have never bled the brakes.... You still have 50+ year old LHM in them :eek:
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Hi Shane,

I didn't suggest the brakes circulate. Back to tinkering with the dyane :)

Cheers,
Andrew
 
DoubleChevron said:
Can you boil LHM? I have never experianced such a thing. I've "heard" you can brake a Citroen CX from well over 200km/h ... and not boil the LHM in the lines. :whistle: , er, "apparently" it brakes hard and straight from 220km/h easily. Here is the thing though, pick a spot you think you will stop easily by .... and watch as it flashed by well your still way into 3 digit speeds :eek:

if you have good clean, bright green LHM in the 2CV, I can't imagine a scenario where you would boil them. I know someone with a very "hot" CX turbo with a diesel gearbox fitted. From "high" speed, he says the brake pads melt and the warning wires fall out and the discs crack. Fancy aftermarket slotted brake rotor explode :eek: ... He has never mentioned the LHM boiling though (I can't imagine your trying to brake a 2cv from "exteme" speeds like him) :)

seeya,
shane L.
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I can assure you Shane there are many stories of disc brakes 2cv having failed brakes on long down hill runs. They are famous for it. The dot 4 drum brake models not. Because the engine is so small you don’t get all the engine braking you might expect. But it is a consequence of overheating the brakes. With a 2 cv the amount of lhm in the circuit is very small

The only big cits I have seen with this problem have oddly been SMs
 
PeterMol said:
I can assure you Shane there are many stories of disc brakes 2cv having failed brakes on long down hill runs. They are famous for it. The dot 4 drum brake models not. Because the engine is so small you don’t get all the engine braking you might expect. But it is a consequence of overheating the brakes. With a 2 cv the amount of lhm in the circuit is very small

The only big cits I have seen with this problem have oddly been SMs
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The is really interesting. Even with fresh LHM they still boil? I find it strange, because even race cars haven't boiled the LHM!
 
DoubleChevron said:
The is really interesting. Even with fresh LHM they still boil? I find it strange, because even race cars haven't boiled the LHM!
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It’s pretty scary when it happens. I suspect more sophisticated cars have effective brake coolers and much larger quantities of lhm. Perhaps even better callipers. 2cv callipers are very small
 
The bigger Cits are OK with LHM brakes because they have a virtually unlimited supply of LHM at very high pressure to squash any gas and get pressure back down on those caliper pistons.

Cheers, Ken
 
Ken W said:
The bigger Cits are OK with LHM brakes because they have a virtually unlimited supply of LHM at very high pressure to squash any gas and get pressure back down on those caliper pistons.

Cheers, Ken
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nah, air still really affects them. I still thinking hte LHM 2cv's have all just never had the fluid changed, so moisture is sitting at the lowest point. Even the tiniest bit of air in a hydraulic cars brakes causes a very obvious braking delay. I'd be keen to try a 2cv that's known to have had the brakes fade away. I'd change the fluid and drive the exact same bit of road, and see if they faded again.

Wasn't LHM even used in one of the fighter jets australia used to have. I'm still thinking the cars have just boiled moisture that is sitting at the lowest point (ie: the front brake calipers).
 
The big difference between a DS and 2CV brake system is as Ken said, the DS has a pump constantly generating pressure where the 2CV only has the small master cylinder. An air bubble creates a delay in the DS brakes but will quickly be squashed and kept compressed by the umlimited supply of LHM at 150bar. I don't think the 2CV system would have anywhere near the same amount of pressure behind it so as the LHM vaporises there's nothing to keep the gas/LHM mix compressed.

DS brake calipers are huge lumps of cast aluminium bolted to the gearbox with a tonne of air moving past. There's a lot of mass to soak up and dissipate the heat compared to the 2CV calipers.

Never let anyone convince you that LHM doesn't boil and isn't flammable. According to the Total MSDS it boils at 100°C with a flashpoint at 105°C which is surprising low.
 
faulksy said:
The big difference between a DS and 2CV brake system is as Ken said, the DS has a pump constantly generating pressure where the 2CV only has the small master cylinder. An air bubble creates a delay in the DS brakes but will quickly be squashed and kept compressed by the umlimited supply of LHM at 150bar. I don't think the 2CV system would have anywhere near the same amount of pressure behind it so as the LHM vaporises there's nothing to keep the gas/LHM mix compressed.

DS brake calipers are huge lumps of cast aluminium bolted to the gearbox with a tonne of air moving past. There's a lot of mass to soak up and dissipate the heat compared to the 2CV calipers.

Never let anyone convince you that LHM doesn't boil and isn't flammable. According to the Total MSDS it boils at 100°C with a flashpoint at 105°C which is surprising low.
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So has anyone actually tried changing the fluid in one of these 2cvs that suffers brake fade? I'm just interested. As it still sounds very strange to me that LHM would boil only in a 2cv, not in race cars, not in fighter jets, not in high performance cars etc.... I'm not saying its impossible, just it sounds very strange to me :)

of course LHM will burn and boil. But your talking when its not under pressure. The boiling point raises tremedously with pressure. Look at what temperature a cars cooling system boils at if its pressurised to only 20psi :)

Think how hot a Citroen BX brakes are after its done its 100th crash stop from 220+km/h down conrod straight in a row ... that after its done how many dozen crash stops at every other corner of the race track ? They would be literally glowing red hot ... I bet if you watch the bathurst race night time footage you an see the brake glowing red hot at the turn at the end of conrod straight ... time and time again. without the LHM boiling :)
 
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to come back to the original question, having driven a brake fluid Dyane for many thousands of KM, and driven a disc 2cv, I would not be in a rush to change the drum brakes, and in many ways prefer the drum brakes. Even after seldom driving the car between raids, the brake fluid brakes worked fine. If someone was really worried about moisture you could use dot 5 silicone fluid.
 
Thanks for all the response's, the reason for the enquiry is due to a possible EV conversion for a client. Having spoken to the engineer now and will be happy with the split circuit brake system and passing a plate brake test.

Happy to hear the drum brakes work well, same with some of the early kombi's that I work on, the disc upgrades don't achieve a lot.
 
PeteB said:
Thanks for all the response's, the reason for the enquiry is due to a possible EV conversion for a client. Having spoken to the engineer now and will be happy with the split circuit brake system and passing a plate brake test.

Happy to hear the drum brakes work well, same with some of the early kombi's that I work on, the disc upgrades don't achieve a lot.
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does the engineer understand the brakes are inboard? unless you keep the gearbox and driveshafts, there is no front brakes ..... :)
 
PeteB said:
Thanks for all the response's, the reason for the enquiry is due to a possible EV conversion for a client. Having spoken to the engineer now and will be happy with the split circuit brake system and passing a plate brake test.

Happy to hear the drum brakes work well, same with some of the early kombi's that I work on, the disc upgrades don't achieve a lot.
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DoubleChevron said:
does the engineer understand the brakes are inboard? unless you keep the gearbox and driveshafts, there is no front brakes ..... :)
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Hi Pete,

Sounds very interesting. What are you thinking for batteries and motor, if you ok to share?

Cheers,
Andrew
 
DoubleChevron said:
does the engineer understand the brakes are inboard? unless you keep the gearbox and driveshafts, there is no front brakes ..... :)
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andrewj said:
Hi Pete,

Sounds very interesting. What are you thinking for batteries and motor, if you ok to share?

Cheers,
Andrew
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If it goes ahead, I am just prepping the body and mechanicals. The actual conversion will be done by Australian EVS, they are based in Newcastle, using Tesla modules and a Hyper 9 motor.
Original gearbox is retained. Helped them do the VW beetle a little while ago.

Will start a project thread if it goes ahead
 
PeteB said:
If it goes ahead, I am just prepping the body and mechanicals. The actual conversion will be done by Australian EVS, they are based in Newcastle, using Tesla modules and a Hyper 9 motor.
Original gearbox is retained. Helped them do the VW beetle a little while ago.

Will start a project thread if it goes ahead
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Hi Pete,
Very much looking forward to seeing the thread.
Would I be right in assuming the Hyper 9 has substantially more torque than the original motor- If so, is a GS gearbox worth considering? I would be a lot more messing around with mounts, drive shafts, brake compatibility etc. But given the GS was roughly twice as powerful as the 2CV, the end result would be very zippy!

Cheers,
Andrew
 
PeteB said:
If it goes ahead, I am just prepping the body and mechanicals. The actual conversion will be done by Australian EVS, they are based in Newcastle, using Tesla modules and a Hyper 9 motor.
Original gearbox is retained. Helped them do the VW beetle a little while ago.

Will start a project thread if it goes ahead
Click to expand...
This will be exciting for those of us that will probably never attempt such a thing to watch :dance:
 
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