Shortening Brake Pedal Travel

[TonyD]

After taking the long way round to drop off the almost completed AK at the trimmers I have decided that the travel on my brake pedal is just a bit too long.

The brakes work great, its just the amount of travel I dont like. Funnily enough when the engine isnt running ( ie no servo) the pedal has exactly the right travel and feel.

The present set up uses a Peugeot 206 master cylinder and servo.

Am I correct in my thinking that to reduce pedal travel what I need to do is to increase the bore of the master cylinder which would then decrease the required amount of travel on the pedal to push the same amount of fluid through the system ? The overall effect would be a harder, more resistant pedal but with less travel.

Any comments on my simple logic appreciated.

Cheers,

Tony













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[TimH]

Tony,

The theory is correct, I did the reverse with my clutch master cylinder, making it a smaller bore to increase the pedal travel and make the clutch lighter.

I thought with brakes though, that they are always meant to rub slightly against the disc, and that you are not so much moving the pads towards the discs - rather increasing the pressure against the discs, so that there should be virtually no pedal travel in any case?

I'm no expert, so maybe someone else can correct me if i'm wrong.

Tim.

[callum]

Alternatively, instead of pushing more or less fluid (changed bore)you could adjust the length of the lever (foot pedal) by moving the point at which the master cylinder actuator rod engages with the pedal lever. Moving it up a smidgen towards the hinge will increase the effort(leverage) but reduce the travel. With a servo, the extra weight may actually improve feel if it is currently too sharp.

[Happy Jim]

Tony,

How about removing the Servo? GD's don't have them and I've got no complaints - bags of feel.

Cheers

Jim

[TonyD]

Me thinks that Peugeot has over-servoed the small bore master cylinder to get the desired pedal action in the original vehicle.

At the moment I have got the mounting point where the cylinder rod meets with the pedal and the cylinder itself on the same plane. To raise the pedal mounting point, and thereby increase the mechanical advantage, would cause the actuation rod to move out of the horizontal plane with possible resulting bending forces.......which in a hard braking situation is not really desirable.

I shall investigate the possibility of doing without a servo in total. What donor master cylinder does the GD use ? I only chose the present set up because it was the only servo and mc combination that would fit the Beemer pedal box I had and also fit into the space available.

In the meantime I shall be scouring the scrappies and internet to see if Peugeot ( or more precisely ATE their brake supplier) can provide me with a larger bore MC that can fit on the servo I already have.


And to think I had a complete Marina pedal box waiting to be installed before I decided to do my own thing!! Now I have altered my bulkhead even the Marina bits wont fit.........


Cheers,

Tony

[Happy Jim]

>in total. What donor master cylinder does the GD use ? >


Tony,

Hmmm got me there I used the cheque book approach and bought the recommended one from Andy to match the RV8 G'Box (.075 I think).

Cheers

Jim

[osgood]

Contrary Mary

Tony, I would not make any drastic changes until the pads which I assume are new have bedded in. I had the same problem with my Jaguar set up with reckon master cylinder which I did my self. Same systems loads of travel with engine running, purchased new unit (master cylinder) @ £120:00 trade. absolutely no difference!! Passed SVA with excessive travel, but pedal travel improved by 50% when got 1,500 on the clock, Eric.

[TonyD]

Yep,

I've got new pads all-round and new discs on the rear. Front discs were fine. Perhaps I do need to bed the pads in a bit.......

Cheers,

Tony.