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 Post subject: Bigger Slave Cylinder?
PostPosted: Mon Sep 21, 2009 8:38 pm 
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I drove a starlet the other day with a custom slave cylinder from another car adapted to suit and even with a heavy duty clutch the pedal was nice and easy.

Can someone tell me if i got a larger slave how that would affect the standard mini master?

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PostPosted: Mon Sep 21, 2009 8:43 pm 
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A bigger slave bore diameter will use more fluid to cover the same distance, which basically means your pedal effort is magnified at the clutch. This gives you a lighter pedal, although you need more pedal travel to give the same amount of clutch actuation.

With a race or button clutch this is a good thing, it gives you more control over the take up point. It won't affect the master at all.

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PostPosted: Mon Sep 21, 2009 9:32 pm 
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I actually saw one of the Mini's at Gannons on the weekend with a small one made by PBR

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PostPosted: Tue Sep 22, 2009 6:42 pm 
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I have been thinking about doing this to reduce pedal effort but I don't know if I will have enough pedal travel.
Was thinking of using a 7/8"mini slave seal kit and making a new cylinder instead of the 13\16 one I have now.

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PostPosted: Thu Sep 24, 2009 3:13 pm 
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Let me know if you want to give it a go Ben, i need a new slave so i'm happy to try and see how it goes.

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PostPosted: Fri Sep 25, 2009 11:23 am 
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Mini Clutch Master .75inch bore (3/4")/19.05mm
Standard EP82 Master is 0.625inch bore (5/8")/15.875mm
Standard EP82 Slave is 0.8125inch (13/16")/20.6375mm

Mini Clutch Slave 0.875 inch bore 5/8"/22.225mm

So I think a 5/8 Cylinder would be about right Ben even a 23 or 24mm bore as there seems to be around 5mm difference between master and slave on the toyota as standard, and that would mean we can go to 24mm or around that? does that sound right?

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PostPosted: Fri Sep 25, 2009 7:09 pm 
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It depends a bit on the pedal ratio as well cylinder ratio.
But the 7/8 slave will definitely help it is a couple of mm bigger than standard,
How far do you have to push your clutch pedal before the clutch releases? I had to bend my pedal upward so it would release at about half pedal travel so am a bit worried by increasing the travel with a larger slave.

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PostPosted: Tue Mar 16, 2010 1:55 pm 
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To answer your question Ben, my clutch was fully released in the first 1/3 of travel.

A bit of an update, my slave started to leak and i pulled the car apart and took the slave in to get fixed with the hope to re-sleeve it larger.

To my surprise the slave on the car measured 3/4" - i thought the standard was meant to be 13/16"? Explains why my pedal was so damn hard!!

I'm going to try a standard one and see how that goes as it's about 17% improvement (1.5875mm larger bore) over the 3/4. Will check pedal travel and effort and might try a 7/8 bore later.

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PostPosted: Wed Mar 17, 2010 1:14 pm 
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I got a call from B&R brakes who have been very helpful and they got me in a 7/8 bore clutch slave with the exact same dimensions so i'm going to give that a go, will update once i try it.

I think it's off an EP91 aussie starlet part no. 31470-10021 7/8" bore
I believe the EP82GT used 31470-10040 which is 13/16" bore

can anyone confirm as it's hard to find the bore sizes based on part no.

I thought the gearbox was the same for EP82/EP91?

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PostPosted: Fri Mar 19, 2010 3:42 pm 
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I put the slave in last night and it's much better, standard off the shelf EP91 slave is 7/8" and bolts straight on, a little bigger and was a tighter fit around the turbo water feed lines that are next to it but works well.

Will post up some pics, good mod for those with a HD clutch and want a bit more feel.

Clutch engages just a tad under half way now so a bit lower but no worse than a good mini clutch 8)

Cost me $66 for the new slave.

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PostPosted: Fri Mar 19, 2010 8:43 pm 
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That's good the heavy clutch on mine is starting to anoy me so I might have to fit one of these. :)

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