XJ6 & XJ12 Series I, II & III 1968-1992
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Rear brake help please

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Old 03-04-2017, 09:12 PM
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Default Rear brake help please

What size tube nuts for the front and rear calipers? also i was farting around the idea of getting rid of the cross over pipe and just having a tee that fed but sides simultaneously, a second bleeder per caliper would be required but has anyone done this? in theory it would seem that there would be more equal pressure applied to the rotor this way instead of the original way which one side got pressure and then the other side got it.

heres a rough example
 
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Old 03-05-2017, 11:11 AM
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no one has any thoughts on this???

I slept on the idea and i still think its a good idea
 
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Old 03-05-2017, 11:37 AM
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Makes sense in theory at least.

I have doubts about the real-world value/benefit of doing so, though; sounds a bit like a solution looking for a problem. I'm not aware that there actually is a discernable problem with unequal pressure.

Might be fun to do for the heck of it ...and I have full appreciation of that !

Cheers
DD
 
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Old 03-05-2017, 12:25 PM
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ya i think im going to do it just for fun and see what its like, ill make sure all the lines are the same lengths just to be certain everything is equal, maybe there will be a difference maybe not, guess ill just have to see
 
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Old 03-05-2017, 06:25 PM
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but what size are the tube nuts?
 
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Old 03-05-2017, 06:50 PM
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I dont know the sizes, BUT, it will depend on the year of the brale system.

Somewhere in the mid??70's, Jag starting using metric on the brkes, and my numerous S2 cars were a real mixed up bunch.

Your car details in the Sig would be a help.
 
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Old 03-05-2017, 06:52 PM
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At the rear, as I recall, it's 3/16 tube with 3/8-24 UNF fittings

The front calipers are metric. Lord knows why the two are mixed on the same car


Cheers
DD
 
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Old 03-05-2017, 07:01 PM
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I read your post lat night and found the concept interesting.

Whist I don't claim any expertise and this is just my opinion, I would have thought that given the current design there would be no discernible difference in pressure at the two rear brake calipers.

Your proposal would require twice the volume of fluid movement through the brake line to achieve the same pressure.

Potentially, you could actually decrease the pressure at each calipers.

I may be completely wrong but I do find this intriguing.

If you do go ahead please let us know how it went.

Malcolm
 
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Old 03-05-2017, 09:08 PM
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ill be mocking something up soon, i think i will go ahead with this and sorry its a 1984 xj6
 
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Old 03-06-2017, 09:02 AM
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I'm wit Malcolm. Intriguing. A hydraulic engineer, I sure am not. but, it seems that however plumbed the pressure in the line will be uniform, no matter where.


Carl
 
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Old 03-06-2017, 09:06 AM
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More. One of the things, I appreciated most back in the day, was moving from a mechanical braked car to one with hydraulics. No more fussing with adjusting to get even left to right brake application. And we Hot Rod guys salivated over coversions of early mechanical to "juice" brakes.


Carl
 
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Old 03-27-2017, 12:27 PM
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Originally Posted by sunchip
What size tube nuts for the front and rear calipers? also i was farting around the idea of getting rid of the cross over pipe and just having a tee that fed but sides simultaneously, a second bleeder per caliper would be required but has anyone done this? in theory it would seem that there would be more equal pressure applied to the rotor this way instead of the original way which one side got pressure and then the other side got it.

heres a rough example

Good answer to your question/idea.

When fresh, all brake fluids are virtually incompressible and the system works as well as its mechanical and hydraulic design allows.

Pascal's law (also Pascal's principle or the principle of transmission of fluid-pressure) is a principle in fluid mechanics that states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. The law was established by French mathematician Blaise Pascal.
 
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Old 03-27-2017, 01:00 PM
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Inboard brakes are flawed in many ways. But fluid transmission from side to side is not one of them. This idea is a waste of time and money. Better use of resources would be to upgrade outboard brakes. Outboard brakes are more effective, easier to service and more reliable. There's a reason why there are no modern vehicles with inboard brakes.
 
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