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  #121  
Old December 10th 2008, 06:18
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  #122  
Old September 24th 2015, 19:40
proudbugowner proudbugowner is offline
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Sorry to bring this thread back to life, but I researched and unfortunately a stepped bore master cylinder does not affect brake bias. :-( I hope I am wrong, but I think I'm not. They call those master cylinders (quick take up) and they are made to work together with low drag calipers..

Have a look here.

Last edited by proudbugowner; September 25th 2015 at 06:48. Reason: Added the link.
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  #123  
Old September 27th 2015, 03:26
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Originally Posted by proudbugowner View Post
Sorry to bring this thread back to life, but I researched and unfortunately a stepped bore master cylinder does not affect brake bias. :-(
WTIW, I think you're right. I 'feel' (pun intended) the size of the bore of the master cylinder is mainly meant to match the total size of the caliper pistons, so pedal travel remains acceptable.
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  #124  
Old October 7th 2015, 02:18
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Thats correct. The primary piston (23mm) fluid actuates the rear piston 19mm. They are not mechanically linked unless in event of one circuit failure, so equal pressure in both front and rear master cylinder pistons. The step is for volume not pressure.

I've built many bugs with 944na, 944t, 986, 986S/996 with stock beetle 19mm dual circuit mc with great results. Pedal feel is really good, except the 944na where it is slightly low... if that is unacceptable to customer then I put in the 944mc.

With split busses I typicaly build them (944na, 986, 996 etc) with early modified single circuit mc. Yup single circuit, works awesome. Due to pedal ratio the 944NA brake system on single mc works well without as low a pedal as beetle. Again for higher pedal I can use 944mc as option but typical isnt an exercised option by my customers. (Single bus is 22mm mc).
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  #125  
Old February 25th 2018, 14:42
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I think this thread will be revisited frequently over the years...like I'm doing now, because we all go through what this thread is trying to address. I talk to Flat all the time, trying to figure this all out. Basically, I've decided to run n/a 944 with their single 35.9mm pistons on the rear, and some variation of 42mm 2 pot calipers on the front. I chose this based upon word from two guys who's empirical data I totally respect (not that I don't respect others, but these two guys, we can mostly all agree have a lot of experience to base their opinions upon), Steve Carter, and Walter. Both of these guys whether recently or in the past have told me they had VERY balanced brake set ups with the above mentioned sizes. In Walter's case, he used 40mm stock Ghia type front brakes, and with Steve, he said it was late T3 front brakes (which are the same as early Porsche 914/VW T4). That's enough for me. Well, in reality, I was ok with what Steve told me a couple of years ago, and Walter recently confirmed it.

The rear is very easy on an IRS Beetle. I just bought the tubes and swans Lanner (aka Flat) sells and the set up is an easy and direct bolt on with factory VW parking brake cables.

The front is not quite as straight forward, but ultimately not super difficult. Right now, I've got the 944 front spindles on my car, due mainly to the fact I bought the damn Kerscher ball joints and would hate to throw that much money away. So I'm trying to work out how to attach early 914 front calipers to the 944 spindles. The bolt spacing for the caliper(s) is the same as the 944, however, when the caliper is set on the 944 rotor, the holes are about 1/2 a hole too far away to bolt up. Oddly enough, the offset is very close to right on. If you're wondering how I'm make calipers meant for solid rotors fit over 20mm wide vented rotors, I will tell you (per info gleened from Eric Shea of PMB Performance), the 10mm spacers and all hardware from a 70-83 Porsche 911 REAR M calipers can by used to make the calipers fit (width-wise). The rear M calipers is the exact same casting as the EARLY 914 front caliper (thus also use the same pads), with spacers added.

Perhaps a FAR easier way to approach this...and one I may fall back on, CSP from Germany sells a kit that has 20mm wide vented front rotohubs in the 5x130 PCD I need. These rotors go directly onto the stock 1303 spindle and the calipers have the same bolt spacing as your typical Ghia caliper (not sure the exact measurement, but it's less than the 3 inch bolt spacing of the Porsche 944 spindle). These calipers are made to bolt to any of the many Super Beetle caliper adapters needed for those of us who don't have Super Beetle disc brake spindles (pretty much everyone in the States) and give the correct offset over the rotors. The advantage of this: It's a bolt on solution and I'd be done with it. The disadvantage: The rotors are specialized (though I BELIEVE made by Sebro) and I have no idea the source of the calipers, in the event either has to be replaced in the future, who knows if CSP will still exist and thus the parts available. In reality, CSP has been around for many many years and will likely be around for many many more. That said, I REALLY like the idea I could walk into most any auto parts store in the States and buy either calipers or rotors if need be, should I choose to use the Porsche parts. I'm going to give the Porsche parts the good college try. Honestly, all I need is an adapter to mount the calipers and I'll be good to go. I'm going to try making a pattern from plexiglas.

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Last edited by H2OSB; February 25th 2018 at 15:47. Reason: mistakes
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  #126  
Old February 25th 2018, 15:10
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Hi John,

Very true indeed: stock front disks and 944 n/a rears on stock MC is what gave me rock hard pedal and awesome brake balance!
In fact, liked that so much that for my 'daily driver' project, I got a set of fresh stock sized disks in 5x130 from CB, because I liked the alu hub a lot. By now I have acuired parts for a rear 944 20mm disk set up (vented/drileld of course ) as we, so I'am close to the swap :-)



Here you can just see (through the rim) the also new, drilled, 944 n/a rotor bolted to the rear IRS hub:
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Last edited by Wally; February 25th 2018 at 15:16.
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  #127  
Old February 25th 2018, 15:17
H2OSB H2OSB is offline
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Wally--

Do you have any old n/a 944 rotors handy? I've often wondered how close those hubs are to working with 20mm wide 944 rotors

john
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  #128  
Old February 25th 2018, 15:27
H2OSB H2OSB is offline
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Here you can just see (through the rim) the also new, drilled, 944 n/a rotor bolted to the rear IRS hub:
These wheels make me break into a cold sweat. I want a set something fierce for autocross tires
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  #129  
Old February 25th 2018, 15:48
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You will even more if I tell you what they weigh (just 5,3 kg, similar to the magnesium gas burners iirc)
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  #130  
Old February 25th 2018, 15:50
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Originally Posted by H2OSB View Post
Wally--

Do you have any old n/a 944 rotors handy? I've often wondered how close those hubs are to working with 20mm wide 944 rotors

john
You mean trying to put a rear 944 n/a rotor onto one of these alu front type 1 hubs?
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  #131  
Old February 25th 2018, 15:50
H2OSB H2OSB is offline
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Don't think I don't know that. Flat has a set of the even LIGHTER ones he teases me with pictures of from time to time. Someday.....
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  #132  
Old February 25th 2018, 15:51
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Originally Posted by Wally View Post
You mean trying to put a rear 944 n/a rotor onto one of these alu front type 1 hubs?
No, the front. It attaches the same way as the CB rotor. I've also considered getting a set of those hubs/rotors, removing the rotor and turning the hub slightly to fit inside a late 944 rotors (the ones that fit OVER the hub).
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Last edited by H2OSB; February 25th 2018 at 15:57.
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  #133  
Old February 25th 2018, 15:56
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No, the front. It attaches the same way as the CB rotor
Ah! Now I see why you said used n/a rotor
But euh...no, sorry. Due to me trying to minimize parts hoarding a bit, I brought all old rusty rotors to the dump.. sorry.
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  #134  
Old February 25th 2018, 16:00
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Don't think I don't know that. Flat has a set of the even LIGHTER ones he teases me with pictures of from time to time. Someday.....
Oh, do tell! Are they also 5,5 x 15" ?
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  #135  
Old February 25th 2018, 16:00
H2OSB H2OSB is offline
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Ah! Now I see why you said used n/a rotor
But euh...no, sorry. Due to me trying to minimize parts hoarding a bit, I brought all old rusty rotors to the dump.. sorry.
It's all good. Can you please measure the bolt circle of the rotor attachment bolts? The 944 has a 126mm bolt circle.

I actually kinda got on the guy at CB who designed those hubs/rotors. I asked "why would you re-invent the wheel, so to speak, when Porsche rotors are readily available?" He had no answer.
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