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Twin master cylinder sizes

 
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand
PostPosted: Wed Sep 22, 2010 2:40 pm    Post subject: Twin master cylinder sizes Reply with quote
I'm going to upgrade to a twin brake master cylinder pedal box, and need to specify what cylinder size I need. Anyone have any idea?

I have early 944 brakes all around, and I'm guessing I should be fine to go for the standard 924 or 944 master cylinder diameter (don't have the manual in front of me, but will check what it is when I get home).

I want to make sure I get it right, as the brakes will be hard work with out the booster!
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1977 RX924 race car
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www.race4-dcup.co.nz
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 1081
Location: The Netherlands
PostPosted: Wed Sep 22, 2010 5:28 pm    Post subject: Reply with quote
23mm front, 19mm rear
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Insane  



Joined: 20 Jun 2009
Posts: 65
Location: Kyiv
PostPosted: Fri Sep 24, 2010 8:24 pm    Post subject: Re: Twin master cylinder sizes Reply with quote
Andrew NZ wrote:

I have early 944 brakes all around, and I'm guessing I should be fine to go for the standard 924 or 944 master cylinder diameter
I want to make sure I get it right, as the brakes will be hard work with out the booster!


If you want your brakes to work without the booster std size is not what you really want as it will be really tough.
so you will need a smaller diameter with a longer travel then standard one.
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ideola  



Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
PostPosted: Fri Sep 24, 2010 8:35 pm    Post subject: Reply with quote
From my UWB Suspension Upgrades thread:
ideola wrote:
Tilton 600 series 3-pedal assembly



On top, we have a 15/16" master cylinder to be used for the clutch master; following we have 3/4", 7/10" and 5/8" cylinders, which will allow me to play around with the pairing and balance for the dual cylinder setup for the brakes.



ideola wrote:
Raceboy wrote:
Very, very nice! If it's not a secret, how much did this Tilton pedal assembly set you back?

Just over $1300.

bass gt is running one of these, and I selected the brake master cylinder sizes based on his feedback. The Tilton rep said to use 3/4" and 13/16" cylinders for the brake config. Steve is using two 3/4" cylinders and recommended going a size or two smaller because he felt that his setup was a bit too "wooden", and thought the smaller cylinders would help. Ultimately, it is all a matter of personal taste and driving style. Since the cylinders retail for only ~$100, I decided to get the range that I did in order to have some flexibility in sizing. Remember, this is a completely boosterless setup!

Also, I decided to pay a little more and get the cylinders and reservoir with -AN fittings instead of the OEM-style crimp-on fittings. It will cost a bit more to get all the stainless hose and fittings, but in the end, I think it will be better.

I had also debated long and hard on whether or not to get the accelerator. You can get the two-pedal assembly for less than half the cost of the three-pedal setup. However, because of the way these mount to the floor, and also because of the way the 924 floor slants up immediately behind the mount point of the stock accelerator pedal, I didn't want my accelerator and brake-clutch pedals to be that mis-aligned. I finally decided to "bite the bullet", paid the extra to get the three pedal setup. By the time you add in the extra for that, the throttle linkage assembly, the extra master cylinder, and the extra expense for -AN fittings, it ended up costing between $500-$600 more than the bare-bones basic two-pedal configuration. So you could get a two-pedal brake-clutch only in the $700-$800 range.

A footnote to the whole thing, EBS usually doesn't stock Tilton products but they can get them. I did some comparison price shopping between three major Tilton resellers, and EBS matched the pricing, so I was happy to give them the business.


Also, here's a discussion that led to my selection of the Tilton setup:
http://www.924board.org/viewtopic.php?t=27181
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand
PostPosted: Sat Sep 25, 2010 7:03 pm    Post subject: Reply with quote
Thanks very much everyone - some great info in there!!

I'll let you know what I end up going with.
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1977 RX924 race car
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