Brake Proportioning Valve Limiter O-rings

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Brake Proportioning Valve Limiter O-rings

Postby TorqueHorse » Thu 13.08.2020, 19:05

Disclaimer: Lotus workshop manual specifically states that the rear proportioning valves shouldn't be serviced and if one is weeping or in doubt, you should replace them all. However, if you are interested in taking on the risk of trying to fix these yourself, as the parts become harder to come by to replace, then read on.

Project Status: Gauging interest

Project Brief: (draft) The rear brake proportioning (or limiting) valves play an important role in balancing stopping power across the front and rear wheels to prevent the rear wheels from locking up before the front wheels. There is a write-up in the wiki and a history of threads on the site of people attempting to recondition the valves by replacing the o-rings, however the specific o-rings used don't seem readily available. This group buy would be for best guess appropriately sized and chemically compatible replacement o-rings for your existing valves.

Estimated Cost: (working target) 1/4 the price of a pair of replacement valves, ~$50 or less, before postage.

Working Group: Interested in contributing your time, money, and potentially your parts to research what is needed, and where to source the items from, and put together the final proposal for the group buy? Then sign up to join the working group. Money and parts donated will be tracked and (hopefully) reimbursed through the final group-buy cost.

Group Buy: Want to buy, at your own risk, what the group comes up with? Then signup and indicate how many sets you want in (parentheses) after your name. Assume 1 set will include pieces for both the left and right valves. Also, if you know it, list what proportion your valves are: either 3/15 or 2/15
Last edited by TorqueHorse on Thu 13.08.2020, 19:08, edited 1 time in total.
'90 FED M100 -mid resto
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Re: Brake Proportioning Valve Limiter O-rings

Postby TorqueHorse » Thu 13.08.2020, 19:07

Working group signup:

TorqueHorse



Group buy signup:

TorqueHorse (1) 2/15
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Re: Brake Proportioning Valve Limiter O-rings

Postby steve matthews » Thu 13.08.2020, 19:38

When I rebuilt mine the springs were eaten up. What about the springs also.

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Re: Brake Proportioning Valve Limiter O-rings

Postby TorqueHorse » Thu 13.08.2020, 20:37

Great idea! I'll leave it to the working group to determine the final bits to be included. If it seems like a common problem, and we can source one and get it under the target budget, then let's assume its in for now. Be sure to add your name to the list.
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Re: Brake Proportioning Valve Limiter O-rings

Postby marvic » Sat 15.08.2020, 02:55

My car came with two of these in place of the original.

https://www.wilwood.com/MasterCylinders ... =260-12627

Previous owner replaced them when installing bigger front brakes so the adjustability probably allowed balance to be more adjustable. Easily available if no original parts available.
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Re: Brake Proportioning Valve Limiter O-rings

Postby 378S2 » Tue 29.09.2020, 00:36

Reciepts with the car indicate that the n/s proportioning valve on my S2 was recently fitted with new o-rings and the previous owner was kind enough to tell me about the problem. It seems absolutely fine, no leaks and no unusual performance under braking. Would you like me to contact the garage and see if they can tell me where they sourced the o-rings? They don’t seem to have had any trouble sourcing them.

Now the WM and common sense tells me I need to also do the o/s, and I am mulling over replacing both with new units.

What is the verdict on the SJS replacements? SJS Proportioning Valve Kit?
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Re: Brake Proportioning Valve Limiter O-rings

Postby TorqueHorse » Thu 01.10.2020, 16:56

378S2 wrote:Would you like me to contact the garage and see if they can tell me where they sourced the o-rings?

Sure, having that info is never a bad thing. Potentially we could update or append to the BPV info in the wiki or this rebuild writeup.
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Re: Brake Proportioning Valve Limiter O-rings

Postby esprit888 » Thu 01.10.2020, 19:13

All of the pics I have seen of the UK valves are different from the Fed valves, not sure if this is due to the switch from 3/15 to 2/15 or they used a different valve for other reasons (During the production of the M100 3 various combinations were fitted) so i would first check that the valve is the same (hexagonal not circular) I have tried 6 pairs of O rings in various combinations so far and cant get them to hold pressure or not leak past the seal and then past the threads. Its either the ID is correct and the OD is too small at the valve end or vice-versa at the spring end. As far as I can tell its due to the fact that the standard sizes of everything I have received has a CS of 1.7 while the OEM O ring is 1.8. Bleeding them each attempt is time consuming and frustrating, even with an Eazi-bleeder. I have tried to build a bench tester but I cant get to the 1,250 PSI needed for the input level to test the 390 to 463 PSI output level (2/15) I may throw in the towel and see if anyone in the U.S. can take a look as i know there is a company in California who overhaul 'anything' (or so the ad says :lol: )
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Re: Brake Proportioning Valve Limiter O-rings

Postby TorqueHorse » Thu 01.10.2020, 22:51

Thanks esprit888 :goodposting:
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