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Garage / Re: front brake lockup
« Last post by 314159td on Today at 10:39:28 PM »Reviving a thread that's already on track of what I'm poking around.
I intend to toss type 14 calipers onto my Series 1 Europa*, which of course started life with type 12 units.
Some napkin math says that swap would be a 25% increase in piston force for the same line pressure, further increasing the potential of a front lockup.
My car would have the same line pressure on the front and rear with a single circuit MC**, so I think a larger rear cylinder would help bring things back into balance. S1 was originally 3/4" rear, so a 7/8" unit may be suitable, but I can't seem to find these, only 7/8" in the TR style.***
With that issue and reading over some threads, it seems like an adjustable proportioning valve installed backwards would work. I.e. rear output plumbed to the front brakes. Reading through Willwood's excellent writeup here: https://shop.wilwood.com/blogs/news/how-does-a-proportioning-valve-work, it seems that installing the valve backwards would allow the rears to receive full line pressure, then taper off the fronts after a certain adjustable point is reached. This would work in panic stopping events, and I think generally appropriate for how people have described the Europa's braking.
I've never had a proportioning valve in a car with mixed drums and discs****, so I'm unsure how the delay and self-energizing of the drums would play into this, but on paper it seems like it would work?
*Type 12 cost more for new units, parts to rebuild old ones are tricky to find (pistons have been OOS for years), and my other car also uses 14 so may as well share a single spare pair. BPNW currently has 12s in stock, but I'm not going to rely on those always being there in the future.
**tried to fit a few different dual units, didn't work. Series 1 is much worse than 2 in that regard.
***Ex: https://bpnorthwest.com/triumph/wheel-cylinder-875-trw-morgan-large-bore-tr4-to-tr6/
****yes, I know about rear disc conversions for the Europa. Later problem.
I intend to toss type 14 calipers onto my Series 1 Europa*, which of course started life with type 12 units.
Some napkin math says that swap would be a 25% increase in piston force for the same line pressure, further increasing the potential of a front lockup.
My car would have the same line pressure on the front and rear with a single circuit MC**, so I think a larger rear cylinder would help bring things back into balance. S1 was originally 3/4" rear, so a 7/8" unit may be suitable, but I can't seem to find these, only 7/8" in the TR style.***
With that issue and reading over some threads, it seems like an adjustable proportioning valve installed backwards would work. I.e. rear output plumbed to the front brakes. Reading through Willwood's excellent writeup here: https://shop.wilwood.com/blogs/news/how-does-a-proportioning-valve-work, it seems that installing the valve backwards would allow the rears to receive full line pressure, then taper off the fronts after a certain adjustable point is reached. This would work in panic stopping events, and I think generally appropriate for how people have described the Europa's braking.
I've never had a proportioning valve in a car with mixed drums and discs****, so I'm unsure how the delay and self-energizing of the drums would play into this, but on paper it seems like it would work?
*Type 12 cost more for new units, parts to rebuild old ones are tricky to find (pistons have been OOS for years), and my other car also uses 14 so may as well share a single spare pair. BPNW currently has 12s in stock, but I'm not going to rely on those always being there in the future.
**tried to fit a few different dual units, didn't work. Series 1 is much worse than 2 in that regard.
***Ex: https://bpnorthwest.com/triumph/wheel-cylinder-875-trw-morgan-large-bore-tr4-to-tr6/
****yes, I know about rear disc conversions for the Europa. Later problem.