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Super Heavy 13B Clutch

Started by _Viper_ , Apr 25 2011 01:19 PM

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7 replies to this topic

#1 _Viper_

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Posted 25 April 2011 - 01:19 PM

Hey guys, I did a 13B conversion in my friends Gemini, got it all finished, We had bought a conversion peice to convert it from Hydraulic to Cable but it was super heavy and you had to press the pedal all the way to the floor and could only just change gear even with the cable adjusted to the max...

So we decided to convert the car to Hydraulic clutch.... The stock 13B 3/4" Slave cylinder and a Wilwood 3/4" Master cylinder fitted it all bled it up and still super heavy :( remove the slave from the gearbox and it works perfect pushes in and out with ease.

So we thought maybe we had used the wrong throwout bearing or something else was wrong so pulled the motor/box out and separated and well I dont really know much about clutches but dont know what to look for... But noticed the fingers on the pressure plate are like flat (vertical) and I think there supposed to be sticking out towards the gearbox a little?

I had this problem once a couple of years ago on another Exedy gemini clutch and we had to put washers between the pressure plate and flywheel to the fingers were at the right angle otherwise there wasnt enough throw to get the clutch to dis-engage, But I dont remember it making the pedal extra hard?

Here's a couple of pics of the pressure plate as is... anyone got any ideas? can also see the wear marks on the fingers are a little bit back from the tips... are they supposed to be right on the end?

Posted Image

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#2 dattoman

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Name:Neil
Location:Perth Western Australia
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Posted 25 April 2011 - 06:24 PM

Looks fine
But... 3/4 master will make it heavier than it should be... it should have a 5/8
And check your pedal ratio
A bearing thats slightly smaller to push toward the end of the fingers would lighten it up alittle too

Is that a heavy duty clutch ?
On the RX7's if you go too heavy they break the pedalbox away from the firewall

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#3 _Viper_

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Posted 25 April 2011 - 09:48 PM

Oh really? it said 3/4" on the slave so we thought the master should be the same? Guess not.

I thought a larger Master would be easier to push as its pushing a larger volume for the less travel distance? or is it the other way round and because its smaller and your not pushing as much its easier? does that mean you need more travel distance tho?

Pretty sure its just a Exedy HD Organic.

If I bought the clutch in and the bearing carrier could you match up a smaller bearing?

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#4 _Bomber Watson_

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Posted 25 April 2011 - 10:01 PM

Very basic Hydraulics.

3/4 master pushing on 3/4 slave will move the slave the same distance as the master and you will have no mechanical advantage bar your pedal ratio.

5/8 master is smaller than the 3/4 slave so you will feel less pedal effort but will require to move the master further to move the slave the same distance assuming the pedal ratio remains constant, this is hydraulic advantage.

Same way a 7/8 master will require a lot less movement with a 3/4 slave but the effort will be increased.

Basically i you have a 10mm2 master moving a 100mm2 slave it will require 1/10th the effort on the master but the slave will only move 1/10th the distance of the master.

If you have a 100mm2 master and a 10mm2 slave it is opposite, you will have to exert 10x the pressure on the master but the slave will move 10x further.

I think??

Cheers.

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#5 dattoman

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Name:Neil
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Car:LX SS , 76 Cadillac , 3 x dattos
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Posted 25 April 2011 - 11:42 PM

Unfortunatly I don't have a swag of thrust bearings I can draw on to match up
But if you give me some measurements I'll make some calls

And yes a 5/8 will lighten it up but require more travel

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#6 _Viper_

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Posted 26 April 2011 - 01:14 AM

Ahhk makes sense now. But we still think something is wrong with the clutch somehow? as the guy who sold us the cable conversion kit says he has used it on a few cars before and used the stock Gemini cable and pedals and its fine...

I actually welded a extension on to his pivot point to give more leverage and this helped a decent amount but was still heavy.

Ive fitted a Hydraulic system to another Gemini in the same way altho we used the Stock Rodeo Master and Slave cylinders and it all worked sweet... From factory do they usually use a smaller master to get the hydraulic assistance.... Maybe we should just change to a 5/8ths... But can we expect much difference? atm Your seriously have to press with all your strength (impossible to drive) and I had to weld in extra braces to stop it master cylinder mount from flexing

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#7 _hutch_

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Posted 26 April 2011 - 09:03 AM

using a 5/8 master and a 3/4 slave will give you a mechanical advantage of 1.2,in other words for every 10 kg thrust you apply to your clutch peddle you will get 12kg on the lever,the other thing might be what throw out lever you have,is there a difference ?
Phillip