[T3] Brake Calipers

[Dave Hall]

I would have thought some sort of plate is essential in there, if only to
ensure the pad is pressed on evenly.  I suspect it's not necessary to have
the inner grip teeth.  A simple shape with a hole for the pad pin would be
enough, I'd have thought.

For the effect of bigger pistons:-
50mm instead of 42 is 8/42 times bigger diameter, which is about 19% extra.
When you square that up for area you double the %, so 50mm would be 38% MORE
braking force for the same pressure in the brake fluid.  

As you say, the braking balance would be very different.  With the 10%
difference of 40mm compared with 42mm diameter, the brake balance change
isn't all that problematic, particularly when it's quite hard to lock up the
rears anyway, and the fronts still tend to lock up under heavy braking.

The slightly smaller pistons generally just mean you need to press a bit
harder for the same braking force, as you would need to produce a bit more
fluid pressure.  Although sold as 311 parts, the thinking is that my
replacement calipers are smaller pistons.  I don't know if that's true, and
haven't pulled the piston out to check - nor will I.  They don't wear as
evenly as the original calipers did, but with the fairly low mileages I do
in the Type 3 (shame on me!) I'm not that bothered about that.  Usually they
will brake far better than calipers that need a rebuild!

Dave
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Adriel
Rowley
Sent: 12 August 2011 04:57
To: type3 at vwtype3.org
Subject: Re: [T3] Brake Calipers


Sorry did not get to this sooner: packing for the move is taking too long.

----------------------------------------
> From: jadney at vwtype3.org
> To: type3 at vwtype3.org
> Date: Wed, 10 Aug 2011 17:11:11 -0500
> Subject: Re: [T3] Brake Calipers
>
> On 10 Aug 2011 at 11:31, Adriel Rowley wrote:
>
> > Adney, how much would it cost for a rebuild with caliper cores 
> > without the plates?  How much would the plates cost by themselves?  
> > Starting to regret going the big business route and thinking I 
> > should not send my cores out.
>
> I am out of the larger late plates and they appear to be NLA. I will 
> no longer be able to supply them. I can align the pistons properly and 
> I'll look for a more permanent solution, but right now I have none. In 
> practice the pistons seem to stay in position even without the plates, 
> but I don't have much experience with this.
>
What is the purpose of the step?  So the plates are to keep the pistons
aligned?

> > Mind showing how you got the loss of 10 percent calculation for 40mm 
> > pistons?  I am curious of what affect 38mm, 39mm, 50mm have.
>
> It's based on the area of the pistons, so take the ratio of the 
> squares of the diameters, which for 40/42 comes out to .9070 or 90.7%, 
> which is not quite 10% less than 100%.
>
So then 50mm give about 20 percent increase, which would upset the balance
right?  Couriousity killed the cat... ;)

> Note that there's no change in braking between early and late Type 3 
> calipers since both use the same 42 mm pistons.
>
But the force is spread out more due to the larger pads, right?  I did try
the late calipers (going to do an update after this), and they feel a major
improvement over the 40mm pistons.

(Snipped)

Thank you,
Adriel
 		 	   		  
_______________________________________________
VWType3.Org mailing list - type3 at vwtype3.org
http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
Contact gregm at vwtype3.org if you need help with the list.