Brake limiting valves

kev1.3s

So I'm starting to get myself together to fit my brakes on the fulvia, Ive got all the bits and pieces cleaned up But had a look at my brake limiting valve and the prognosis isn't great. It's very much corroded inside, I've disassembled cleaned and reassembled but I'm not overly optimistic however it is moving free now.
First off not all series 1 fulvia's have one ( seems to be on servo assisted cars ) so do I need one? And if I do and my one doesn't work can I get a modern replacement?

Type 17

You should be able to use one from another car, but you'd need to have a rough idea of the percentage of restriction that your car needs to make it work properly. Some research and/or testing would be required. Perhaps the Fulvia one came on other makes/models - see if you can see a part number and do some research into Fiats of the time.

The purpose of the valve is to restrict the action of the rear brakes when the rear axle drops relative to the car body (ie: the car body has dived at the front/lifted at the rear, due to heavy braking). If there is no restriction of the rear brakes in this scenario, the rear wheels may lock and, if the car is still moving fast when they lock, the rear may swing around and overtake the front…

On my first car, a 1.3 Mk1 Golf CL (no limiting valve), I upgraded the brakes and suspension to GTI spec (both the 1.6 & 1.8 GTI's and the 1.6 GL have a limiting valve). There were no issues until I drove up swiftly to a roundabout with three passengers and myself aboard; I'd thought that I'd make a gap on the roundabout, but then decided it was too close, and braked hard - the rears locked up, and we did a neat rear-end skid, swinging around a bit, due to the extra weight in the back, ending up with the two right-hand tyres on the stop line, rather than the two front tyres :eek:
The bigger discs and callipers from the GTI aided quicker stopping, but this also lifted the rear of the car enough to cause rear lock-up and some excitement. Fortunately, this only happened the once, and was relatively hard to provoke.

Assuming that Lancia put the valve on servo-assisted cars, then the front bakes must be powerful enough to cause the above scenario, if you drive aggressively or at high speed, but if you don't plan to drive aggressively, or at high speeds on motorways, then you might be ok, however if you end up in an emergency situation, your rear may overtake the front...

kev1.3s

Thanks for that, very insightful. I've had various feedback today some think it's crazy to proceed without it others think I should just bypass and move on. If you've ever seen the rear seats in a fulvia you'd know they won't be used for adults how and ever I don't think I feel right without fitting it, I'm going to try work with the one I have if that doesn't work I'll source a replacement.

MercMad

Buy a Motorsport spec one that is adjustable.

Kenny Logins

MercMad wrote: »

Buy a Motorsport spec one that is adjustable.

Would that work? It's an inertia valve, yeah? Aren't motorsport jobs (proportioning valves) manual...?

Type 17

They aren't inertia valves, they work by a lever connected to the rear axle being moved as the axle drops during heavy braking.

I don't know if there are adjustable motorsport ones that work on that principle - the ones I've seen are manually-adjusted from inside the car, and are described as brake bias valves, rather than brake limiting valves or brake compensating valves.

kev1.3s

Type 17 wrote: »

They aren't inertia valves, they work by a lever connected to the rear axle being moved as the axle drops during heavy braking.

I don't know if there are adjustable motorsport ones that work on that principle - the ones I've seen are manually-adjusted from inside the car, and are described as brake bias valves, rather than brake limiting valves or brake compensating valves.

No the ones on series 1 fulvias have no leaver attached to the axel so they must be the inertia type.

Type 17

kev1.3s wrote: »

No the ones on series 1 fulvias have no lever attached to the axle so they must be the inertia type.

Well, in that case, there may well be a motorsport one that would suit your needs.

kev1.3s

Type 17 wrote: »

Well, in that case, there may well be a motorsport one that would suit your needs.

It's actually located on the bulkhead at the front, inside there is a large ball bearing which I presume pushes against a rubber seal.

Kenny Logins

kev1.3s wrote: »

It's actually located on the bulkhead at the front, inside there is a large ball bearing which I presume pushes against a rubber seal.

http://what-when-how.com/automobile/hydraulic-braking-system-automobile/

Scroll down, scroll down, scroll.

It mentions front-wheel-drive vehicles but I had one on my VW Type2, and when it wasn't functioning the rear wheels would lock like back pedalling a Super Deluxe.

kev1.3s

Yeah I think it's best I use it or a replacement.