[s-cars] abs purge procedure

[Mark Strangways]

Right, volumes are irrelevant aren't they.
I guess I should have made that point as well, but it was assumed... yes my 
bad.

Ofcourse the G60's are 2 piston. It's been many a year since I have seen 
one, and I was also thinking that it was a combined 60mm.

Mark
----- Original Message ----- 
From: "Eric Renneisen" <racingiron at comcast.net>
To: "'Robert Rossato'" <bob.rossato_af at cox.net>; "'Mark Strangways'" 
<StrangConst at rogers.com>; "'Mike Fitton'" <rfitton at vt.edu>; 
<keith at maddock.com>
Cc: "'S Car List'" <s-car-list at audifans.com>
Sent: Sunday, December 17, 2006 6:50 PM
Subject: Re: [s-cars] abs purge procedure


> First, I assume we're talking piston diameter here, as fluid volume is
> really meaningless in this context.
>
> I don't have the Porsche numbers handy, but virtually ALL Porsche
> calipers anyone has put on these cars have a LOWER effective piston
> diameter than the G60s.  The G60 piston diameters are equivalent to a
> single-piston of 60mm (hence the name).  The 993tt, 996t, 996, Boxster
> S, etc. all have single-piston equivalents in the mid to upper 50s.  You
> can expect slightly less pedal travel when upgrading.  Also, I don't see
> a good reason to go for a larger MC when you'll have less caliper piston
> area.
>
> Now, as for proportioning, you've got to consider more than just piston
> diameter.  You're also likely changing rotor diameter and pad material,
> both of which will effect the braking force applied by a given pedal
> force.  I'm no expert here, but I'd say do your upgrade then test (with
> ABS disabled) to see if the balance is off.
>
> Eric R.
> '86 urq - Boxster brakes (under 15" Ronals)
> '93 urS - Stock G60s, but not for long...
>
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Robert Rossato
> Sent: Sunday, December 17, 2006 6:19 PM
> To: 'Mark Strangways'; 'Mike Fitton'; keith at maddock.com
> Cc: 'S Car List'
> Subject: Re: [s-cars] abs purge procedure
>
>
> G60s are 2 piston calipers, but you knew that so I'll assume it was just
> a typo ;-)
>
> I don't know what the relative piston diameters, and depth of the piston
> cavities, are for the G60 and 993tt calipers, but my understanding was
> that there was a larger volume in the Porsche calipers.
>
>> -----Original Message-----
>> From: s-car-list-bounces at audifans.com
>> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Mark Strangways
>> Sent: Sunday, December 17, 2006 6:03 PM
>> To: Mike Fitton; keith at maddock.com
>> Cc: Robert Rossato; S Car List
>> Subject: Re: [s-cars] abs purge procedure
>>
>>
>> I don't actually think the Porsche calipers are have any less
>> fluid then the
>> G60's.
>> Remember that the Porsche are 4 piston and the g 60 is 1 piston.
>>
>> The proportioning valve works on pressure principals not flow. You may
>
>> find that if the front NEW calipers contain less volume than the OLD
>> calipers, you will get a firmer pedal due to the higher force
>> required to
>> exert the same pressure and you will also find that they react faster.
>> The reverse would be true for the rears if the NEW calipers
>> where large
>> volume.
>>
>> Either way I don't expect you will have any problems.
>>
>> As Robert beat me to it... you will find there is a ton of
>> pedal firmness to
>> be had by servicing and adjusting the rear calipers properly.
>> Many factors
>> can lead to the pads being way to far away from the rotors,
>> this adds the
>> need for more fluid volume to the caliper before it starts to
>> build force.
>>
>> Mark
>
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