Brake Bias Switch In Cabin?

[Lean Machine]

There is a brake bias switch fitted inside my 400se and I am thinking of having it removed. It was fitted by the previous owner, presumably because he used it on the track. I don't see much use for it and it's an eye sore in the cabin. Does anyone else have this contraption and is it worth keeping? I ask because the car is going in for some more repairs including the master cylinder and it may be a good time to have this switch removed from the cabin. Any ideas?

Tony. TCB.

[Jack Valiant]

If you remove it from the cabin you may need to replace the normal bias switch under the bonnet. You will need at least 65% on the front and 35% to the rears, if it were me I would put the current switch under the bonnet when you do the master cylinder and re plumb it at the same time. Once done get you friendly MoT station to put the car on the rollers and adjust to taste.

Chris

[Lean Machine]

Jack Valiant said:

If you remove it from the cabin you may need to replace the normal bias switch under the bonnet. You will need at least 65% on the front and 35% to the rears, if it were me I would put the current switch under the bonnet when you do the master cylinder and re plumb it at the same time. Once done get you friendly MoT station to put the car on the rollers and adjust to taste.

Chris

I don't understand. I didn't know there is another normal bias switch under the bonnet, at least none that I can see. All I can see is the one inside the cabin mounted on the lower section of the gear tunnel down by my leg. I want to remove it because it's not much use to me. Also the master cylinder is passing brake fluid from one reservoir to the other and that's the reason I want to replace it, maybe with the original twin reservoir rather than two remote ones. More information would be appreciated so as I make sense when I talk to the guy in the garage doing the job. Thanks.

Tony. TCB.

[Jack Valiant]

Tony,

Normally you would have a bias switch in the engine bay. This is usually located under the master cylinder bolted to the body. It has can be traced by following the brake lines from the MC. These are quite difficult to source now so and not state of the art ! So if they fail or the car is going to be used on the track they are sometimes replaced with after market alternatives..

Seems like you have the options I mentioned earlier as I am guessing that if it is missing yours has failed and been replaced.

PM me if you would like discuss further fella

Chris

[Mr Tank]

Hi Tony

Have you looked at the back of the switch in the car?

Does it have electrical conections or pipes?

Andy

[Lean Machine]

Thanks for your replies, Chris and Andy. I am a bit confused and I want to understand this properly before the car goes in for repairs on Tuesday so as I can instruct the guy to do the work.
I am pretty sure there are no electrical wires attached to the bias switch in the cabin. It just seems to be an in line switch from the pipe coming from the master cylinder to the back, though I haven,t really examined it thoroughly but I will over the weekend. What I want to know is this. If I have it removed completely are there any adverse effects or does this system have to have a bias switch somewhere in the line? My intention is to get the car back to original. What do you think?

Tony. TCB.

[Jack Valiant]

Tony, pm me a tel number and I will give you a call when convenient

Chris

[TOPTON]

The car needs a bias switch or valve. More brake pressure is required on the front wheels than on the back because of weight transfer when braking. With equal pressure, the back wheels would lock up very easily every time the brake is pushed any more than gently.

It is usually fitted somewhere near the servo on the bulkhead or inner wing. Obviously yours has been substituted for an adjustable valve fitted near the driver for ease of use while perhaps on a track. If you take that one out then a different one needs fitted.

Edited by TOPTON on Saturday 21st April 11:42

[Lean Machine]

Thanks everyone for the info. I am now clear on how it works and what needs doing. I looked under the bonnet today and underneath the servo bolted to the body I found the original Bias switch. It has been disconnected and a new adjustable Brake bias has been fitted in the cabin. I also understand that it is necessary to have one to balance out the brake pressure between back and front as more pressure is needed for the front. Knowing what I know now, I think I will leave the one already fitted inside the cabin in place, as it all looks in good condition and just have the master cylinder repaired or replaced. Chris, thanks for the offer of the phone call but it won't be necessary as I now understand the situation.

Tony. TCB.

[Jack Valiant]

Hi Tony no problem, i found a picture of the said item as fitted to my car for info anyway!




Cheers

Chris

[Lean Machine]

Thanks for the picture Chris. I have located my bias switch under the bonnet, exact same as in your picture except mine's painted black in under seal. The pipes are disconnected and new ones rerouted for the cabin bias. I get the idea now thanks to you all. Tuesday morning I shall instruct my mechanic to fix or replace the master cylinder and leave the cabin bias where it is. It may be bit of an eye sore but it looks in good condition, in fact it looks new. Thanks again for all the info.

Tony. TCB.

[njhucker]

Wedges don't have a bias valve as such. What they have is a deceleration valve in line going to the rear brakes only. There is a ball inside, that under deceleration moves forward to cover a hole and restrict the flow to the rear calipers. This stops the rears locking up. It is adjusted by altering the angle of it. It does not adjust the percentage front to back.

[Lean Machine]

njhucker said:

Wedges don't have a bias valve as such. What they have is a deceleration valve in line going to the rear brakes only. There is a ball inside, that under deceleration moves forward to cover a hole and restrict the flow to the rear calipers. This stops the rears locking up. It is adjusted by altering the angle of it. It does not adjust the percentage front to back.

Well. You live and learn. Before today, I didn't even know there was a need for such a device. In principal though it must do a similar job. One is set to a level and the other works on gravity to restrict the flow. Thanks for the info.

Tony. TCB.