25mm master cylinder on eBay

[jkarlsso@metabolex.com (Jonas K.)]

On 5/29/02 5:00 PM, "Runs With Scissors" <dan@angband.org> wrote:

> Why would it increase the range of force you can apply to the brake
> pedal?  If anything, it will decrease it, because you will have a lower
> maximum force available.

Well, if the maximum clamping force of the pads on the rotor is taken to be
the point of lockup, and the pedal force requred to achieve this clamping
force _increases_ when the MC inner diameter increases, then you've
_increased_ the range of force available. Right?

>> 3) I don't see any 16v people out there rushing to get 20mm MC's to beef up
>> their brake clamping forces.
> 
> Because: 
> 
> a) most people don't understand that a smaller diameter MC has higher
> output pressure.
> 
> b) people who do understand that realize that you will need to find a 20mm
> MC that has a long enough stroke so that you have enough displacement to
> operate the 10.1: calipers.  There is no 20mm MC that has the same or
> greater displacement as the stock MC, although there is one that comes
> very close (something like 3 percent less displacement than stock)
> 
> c) The stock 16v MC is enough to lock good tires in dry
> conditions. Upgrading to get a higher clamping force isn't needed, unless
> you want to be able to lock your brakes without pressing as hard.

Seems to me your points a) and c) are contradicting. How can the smaller one
both have higher output pressure and also require harder pedal pressing to
generate the same clamping force? That's a genuine question, not trying to
be a smart-ass. 

>> 4) I wouldn?t put this on a car with 9.4's up front and drums in rear, but
>> if you've got 11" dual pistons up front and discs in rear, you might find
>> this necessary to set up a good balance, along with a proportioning valve to
>> adjust for optimal brake balance.
> 
> If you're running 11" dual pistons in the front, , you'd probably need it
> for the extra displacement.  Changing to rear discs does not require any
> MC change, but does require different proportioning valves unless you like
> the rear end to fishtail in the rain.

On this we're in complete agreement. This was meant only for those with
-seriously- modified brakes, who need the added displacement. For stock
calipers the stock selection of MC's will work fine. This one is the largest
available VW/Audi unit that will bolt up to the stock brake booster. It is
also very expensive from the dealer, and it's rare to find a new one at this
price. Just looking out for my fella roccit owners.

Have a nice day, 
Jonas