R12 rear brake bias

[Stuey]

Hi all,

I'm putting stiffer springs on the R12 Wagon tomorrow (I carry loads) and wondered if I'd need to adjust the brake compensation device on the back. Any ideas? And if so, is there a way without using a pressure gauge - say just trial and error testing?

Cheers

Stu

 

[JohnW]

Hi Stuey,

I'm guessing, or at least trying to be rational, and this is what occurs to me:

You'd still want about the same change in front/rear bias with change in rear load - i.e. getting more braking effort to the rear as the load goes up. But with the stiffer springs, you'd get less spring deflection for the same load. So the valve and its linkage will underestimate the need to feed more pressure to the back for a given load. This suggests to me that the mechanical advantage of the linkage needs to change in the direction of a shorter link from proportioning valve to suspension when you have the stiffer springs in place.

This all assumes that the valves did the job we thought they did!! I expect they did but don't know whether the changes you are making are really significant with respect to the precision of the pressure control.

I'd be interested to hear what you do.

Our Virage is on its orginal and seems to brake OK, generally without a rear load.

Cheers

JohnW

 

[Stuey]

Hi John, good point. I put a new valve on mine about a year ago, but have never really noticed if it does anything. I might test it in the wet or on gravel and keep adjusting it until the rear locks just after the front, without a load, since that's the way I drive it the most. Must admit, I hadn't thought about the change in rate too much, but what you say makes sense!

Cheers

Stu