Clutch Master Upgrade Options for Elise/Exige? - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 35 (permalink) Old 03-18-2019, 01:25 PM
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I'm using the OE slave but what I mean about the bigger transmission is that it's also got a larger diameter clutch that I assume develops more clamping force thus more spring force.

I used to run the C61 and an HDSS and the pedal was still light enough for daily duty. After the switch to the E153, I don't think I'd like to daily that clutch pedal. It's stiff.
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post #22 of 35 (permalink) Old 03-18-2019, 02:08 PM
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No, it's not a pedal box at all. It just replaces the booster with a bracket that holds a balance bar. It also replaces the bar from the pedal to the booster. That is it.
My balance bar setup also replaced the clutch master to an AP master so I can size it to whatever I want.

Later,
Eldon
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post #23 of 35 (permalink) Old 03-18-2019, 02:11 PM
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Originally Posted by glagola1 View Post
I'm using the OE slave but what I mean about the bigger transmission is that it's also got a larger diameter clutch that I assume develops more clamping force thus more spring force.

I used to run the C61 and an HDSS and the pedal was still light enough for daily duty. After the switch to the E153, I don't think I'd like to daily that clutch pedal. It's stiff.
If you switch to the Pilbeam brake setup, you can size the clutch master to whatever you want. It is an expensive option but would let you balance front to rear brake bias. Kill two birds with one stone.

Can you change out the brake master in the class that you are running?

Later,
Eldon
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post #24 of 35 (permalink) Old 03-18-2019, 03:00 PM
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Originally Posted by glagola1 View Post
I'm using the OE slave but what I mean about the bigger transmission is that it's also got a larger diameter clutch that I assume develops more clamping force thus more spring force.

I used to run the C61 and an HDSS and the pedal was still light enough for daily duty. After the switch to the E153, I don't think I'd like to daily that clutch pedal. It's stiff.
Im just trying to go through the diagnosis here, not arguing.

Are you sure that the clutch for the E-153 is actually stiffer then the C6X? If its the same clutch, and just larger, that doesn't necessarily mean that there is more spring force on the pressure plate, just that it is over a bigger area and further from center on the actual clutch.

That said yeah can you just change slaves to reduce system pressure?

2007 Exige S with almost every track mod...
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post #25 of 35 (permalink) Old 03-19-2019, 05:08 AM
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I gotcha. I've been through two master cylinders in 4 years with the last one lasting only 1 year almost to the day. The first one broke the body and fluid squirted out of the side of it. The second one, as I learned last night, tore the piston seal. See below.

I'm in the process of installing the BOE bias cage and I've got the parts to install the Honda master coming in the mail. So whatever the case is, I'm on the path to a possible fix. I'll bump this thread when ever the Honda part dies but I'm hoping that doesn't happen.

Sidenote: system pressures are not affected by slave or master changes. System pressures are a product of the spring force of the pressure plate and lever length of the throwout arm. You can change pedal feel by altering the ratios of bore sizes between master and slave but the throws will also change.

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post #26 of 35 (permalink) Old 03-19-2019, 05:25 AM
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Sidenote: system pressures are not affected by slave or master changes. System pressures are a product of the spring force of the pressure plate and lever length of the throwout arm. You can change pedal feel by altering the ratios of bore sizes between master and slave but the throws will also change.
That isn't right. If i put in a larger ID slave, the system pressure will go down at the expense of pedal travel. Same as how brake pistons work.

2007 Exige S with almost every track mod...
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post #27 of 35 (permalink) Old 03-19-2019, 05:44 AM
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That isn't right. If i put in a larger ID slave, the system pressure will go down at the expense of pedal travel. Same as how brake pistons work.
Hmmm, the forces at the pedal change but I don't think the pressures inside the system change since the force applied by the spring and lever of the clutch are constant. I could be wrong. This is interesting. I'll have to do some fundamental research. I'm only an architect.
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post #28 of 35 (permalink) Old 03-19-2019, 06:08 AM
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Hmmm, the forces at the pedal change but I don't think the pressures inside the system change since the force applied by the spring and lever of the clutch are constant. I could be wrong. This is interesting. I'll have to do some fundamental research. I'm only an architect.
You are both right but not looking at the "Complete" picture. The pressure plate and throwout arm will set the force required at the slave unit. The combination/ratio of the bore sizes of the master and the slave will set the pressure in the line. The system pressure to the master bore size will set the force required at the master. The pedal ratio will set the required force at your foot.

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Eldon
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post #29 of 35 (permalink) Old 03-19-2019, 06:34 AM
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You are both right but not looking at the "Complete" picture. The pressure plate and throwout arm will set the force required at the slave unit. The combination/ratio of the bore sizes of the master and the slave will set the pressure in the line. The system pressure to the master bore size will set the force required at the master. The pedal ratio will set the required force at your foot.

Later,
Eldon
I think we all understand the mechanics of levers and force/area. The issue of hydraulic system pressure is where I'm less confident. My instinct says that system pressures will remain constant as long as at least one of the forces remains constant. In this case that force is the clutch system.
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post #30 of 35 (permalink) Old 03-19-2019, 07:08 AM
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I think we all understand the mechanics of levers and force/area. The issue of hydraulic system pressure is where I'm less confident. My instinct says that system pressures will remain constant as long as at least one of the forces remains constant. In this case that force is the clutch system.
No, that is where Kevin is correct. The slave bore size will set the pressure in the line. The slave has to generate "X" amount of force. Take the "X" amount of force needed and divide that by the area of the slave piston, Pounds per square inch (PSI). This is how much pressure that needs to be generated in the lines.

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Eldon
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post #31 of 35 (permalink) Old 03-19-2019, 07:11 AM
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Got it! Kevin was kind enough to walk me through it offline. Lowering line pressure in this manner would result in having to source a new slave that bolts up and reconfiguring my clutch pedal pivot. That's a bit of work.

Still gonna try the metal master first.
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post #32 of 35 (permalink) Old 03-19-2019, 08:51 AM
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Originally Posted by glagola1 View Post
Got it! Kevin was kind enough to walk me through it offline. Lowering line pressure in this manner would result in having to source a new slave that bolts up and reconfiguring my clutch pedal pivot. That's a bit of work.

Still gonna try the metal master first.
Yes, getting a master with a smaller piston size will create less pedal force required. The area of concern is that the smaller piston now displaces less volume. Thus the master has to move farther to create the same distance of travel of the slave. This can some times be compensated by using a longer shaft on the slave unit as long as it still allows total release of the throwout bearing.

Later,
Eldon
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post #33 of 35 (permalink) Old 05-12-2019, 06:34 AM Thread Starter
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Bumping once again, think my clutch master might be close to going out again. Im very close to seeing if I can get one custom machined if there is no other option? The Pilbeam option sounds really invasive/expensive...?

Formerly Wes (RIP : ( ) -- Now Brendon
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post #34 of 35 (permalink) Old 05-12-2019, 06:41 AM
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Best place to order a stock master? All this talk makes me think I should have a spare sitting around.
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post #35 of 35 (permalink) Old 05-12-2019, 06:52 AM Thread Starter
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Best place to order a stock master? All this talk makes me think I should have a spare sitting around.
Whatever you do don't go to Lotus Garage (just got ripped off by them, see the other complaints too). I got my last one from Monkey Wrench

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