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clutch pedal pressure reduction


Hanns Per

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in the Caterham CSR 260 I have the original AP Racing clutch cover with the red dot and the AP racing master cylinder with Dia 15mm and the SBD standard slave cylinder. The pressure needed to press the pedal is very very high. Has anyone a solution to reduce the pedal  pressure?

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Also remember that by simple conservation of energy, whatever you do, to get the same action at the clutch plate, force * distance at the pedal will remain constant. So reducing the force will require a longer travel. Unless of course you go power assisted, which I think is unlikely.
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I have the 14mm master cylinder and tried it but as mentioned by revilla I am stuck within the law of physics it does help a little  but results in longer pedal travel. For the clutch if I am not wrong I need 6-7mm travel minimum. One thing I have not checked yet would is the possibility to increase the diameter and to change the proportionof pedal length to master cylinder pushrod connection or would this accoridng to the law of physics have no impact on pedal pressure?

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Then altering the mechanical advantage on the pedal may be your only option....

unless you pull the engine and see if you can get a slave cylinder with and increase CSA therefore moving the hydraulic ratio back in your favour.

Guessing your slave is hidden in the bell tank in which case providing you can identify it and check this option before pulling the engine sure CC will know which model was fitted originally.

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I use the clutch slave cylinder from SBD :Hydraulic Clutch Slave Cylinder 40mm, I think its the one from Titan, they all look the same. I calculated with the surfaces and the stroke of the 0riginal 15mm dia  master cylinder  I get the required stroke with the this slave cylinder for the clutch. The pedal pressure is OK for the yellow dot clutch cover which I use now with a high tuned 2.1 duratec engine.  But its very hard with the red dot clutch cover which is necessary for the torque of the well tuned 2.4 engine I will put in for 2021 season. Anyone ever thought of some sort of hydraulic supporting device?

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you could add an indirect servo........

or keep the yellow dot cover and use a cerametallic centre plate which will increase the torque capacity of the clutch, naturally there's a trade off in 'feel' though, 

Guessing you will be looking at circa 220lb/ft for the 2.4

AP gave me the following figures based on the stock 5352 organic centre plate

Yellow dot (-1) cover 215 lb/ft

Red dot (-500) cover 280 lb/ft

Cerametallic v organic increases the torque capacity in the region of 80 lb/ft

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  • 3 weeks later...

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