Shock And Brake Questions

[comanche13]

Put a 8.8 in the rear to replace the dana 35 and upgrade to rear discs now the question I have about the bakes is can you bypass that load height sensor?

 

 

Secondly my question about shocks is I installed a 5.5 lift came out to about 6 inches wondering if bilstein 5125 10" travel shocks will work with my lift if not what did you guys use and with installing these new shocks will I need bar pin eliminators or any other shock mounts? Also any suggestions for weld on shock mounts for the rear?

 

Thanks

Tim

[sloride]

I took out the load sensor valve and replaced it with an adjustable proportioning valve just to be safe.

[onlyinajeep726]

You can bypass the load sensing valve, but if you do, I'd run a traditional braking system and replace the MJ distribution block up front with an XJ proportion valve.

[Eagle]

You can bypass the load sensing valve, but if you do, I'd run a traditional braking system and replace the MJ distribution block up front with an XJ proportion valve.

 

There are several threads here that describe how to eliminate the load-sensing proportioning valve.

 

As I posted just yesterday (or maybe the day before), IMHO replacing the MJ front metering block (it is not a proportioning valve on the MJ) with an XJ proportioning valve is a VERY bad idea. To understand why, you have to understand how the XJ proportioning valve works.

 

In the XJ proportioning valve, fluid to the rear brakes is routed through the forward part of the valve body. Inside that, there is a spring-loaded plunger with an o-ring seal on a piston. The spring is VERY strong, and until the brake fluid pressure gets high enough to overcome this spring, there is NO braking to the rear wheels. Once the pressure gets high, the plunger moves and the rear brakes come on. This is why XJ rear brakes typically last through two or three replacements of the front pads -- the rears never do any work in normal driving.

 

But the rear of an XJ has a full roof, rear seats, a lot of glass, and a tailgate hatch. There's a fair amount of weight on the back wheels. The rear wheel load in an empty MJ, by comparison, is very light. In normal conditions you won't notice a difference with the XJ proportioning valve because the rear wheels are doing anything, but under panic conditions the rear wheels could lock up unexpectedly. That's "not a good thing."

 

Of course, if you correctly bypass the MJ height sensing proportioning valve you'll have full braking power to the rear wheels all the time, and that can also lead to premature rear wheel lockup under panic conditions. Being an olde pharte who learned to drive decades before we had proportioning valves, I can live with this because at least it's predictable, where the operation of the XJ proportioning valve is not. (The XJ valves also clog up. My '88 XJ has had no rear brakes for four or five years, but it's driven only locally so I haven't made a priority of fixing it.) For those who can't handle that, the Wilwood adjustable proportioning valve for the rear wheels is the way to go.

 

Do NOT use an XJ proportioning valve. IMHO it's an exceptionally stupid design.

[Eagle]

 

 

 

Secondly my question about shocks is I installed a 5.5 lift came out to about 6 inches wondering if bilstein 5125 10" travel shocks will work with my lift if not what did you guys use and with installing these new shocks will I need bar pin eliminators or any other shock mounts? Also any suggestions for weld on shock mounts for the rear?

 

Thanks

Tim

 

Why would you need weld-on shock mounts? Did you remove the stock shock mount studs?

 

MJ shocks don't use bar pins, why would you need bar pin eliminators?

[jimoshel]

 

You can bypass the load sensing valve, but if you do, I'd run a traditional braking system and replace the MJ distribution block up front with an XJ proportion valve.

 

There are several threads here that describe how to eliminate the load-sensing proportioning valve.

 

As I posted just yesterday (or maybe the day before), IMHO replacing the MJ front metering block (it is not a proportioning valve on the MJ) with an XJ proportioning valve is a VERY bad idea. To understand why, you have to understand how the XJ proportioning valve works.

 

In the XJ proportioning valve, fluid to the rear brakes is routed through the forward part of the valve body. Inside that, there is a spring-loaded plunger with an o-ring seal on a piston. The spring is VERY strong, and until the brake fluid pressure gets high enough to overcome this spring, there is NO braking to the rear wheels. Once the pressure gets high, the plunger moves and the rear brakes come on. This is why XJ rear brakes typically last through two or three replacements of the front pads -- the rears never do any work in normal driving.

 

But the rear of an XJ has a full roof, rear seats, a lot of glass, and a tailgate hatch. There's a fair amount of weight on the back wheels. The rear wheel load in an empty MJ, by comparison, is very light. In normal conditions you won't notice a difference with the XJ proportioning valve because the rear wheels are doing anything, but under panic conditions the rear wheels could lock up unexpectedly. That's "not a good thing."

 

Of course, if you correctly bypass the MJ height sensing proportioning valve you'll have full braking power to the rear wheels all the time, and that can also lead to premature rear wheel lockup under panic conditions. Being an olde pharte who learned to drive decades before we had proportioning valves, I can live with this because at least it's predictable, where the operation of the XJ proportioning valve is not. (The XJ valves also clog up. My '88 XJ has had no rear brakes for four or five years, but it's driven only locally so I haven't made a priority of fixing it.) For those who can't handle that, the Wilwood adjustable proportioning valve for the rear wheels is the way to go.

 

Do NOT use an XJ proportioning valve. IMHO it's an exceptionally stupid design.

This is the most sensible thing on the rear brake subject I think I've read since joining CC.

[onlyinajeep726]

Well, perhaps I should have added that I plan to run ZJ rear disc brake in the future and plan to change out the spring and valve in the XJ block with one from an all disc brake ZJ.  Not sure if that helps or hurts my argument, but just putting that out there at least.

[Eagle]

Well, perhaps I should have added that I plan to run ZJ rear disc brake in the future and plan to change out the spring and valve in the XJ block with one from an all disc brake ZJ.  Not sure if that helps or hurts my argument, but just putting that out there at least.

 

I don't know, either. I haven't sawed a ZJ proportioning valve in half so I have no idea how it works.