Saab/Vectra Front Brake Upgrade

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Re: Saab/Vectra Front Brake Upgrade

Postby bobbrown » Sat 02.10.2010, 09:42

nitroman wrote:
(2) Larger piston in your caliper means your piston moves more slowly for a given amount of fluid. It is only the piston moving forward against the pads which causes the car to stop. Now you must move the brake-pedal/master-cylinder farther to accomplish this, thus you are spreading the same amount of force (moving piston towards pad) as before over a longer master-cylinder stroke, which results in a lighter pedal feel, which begats greater pedal feedback/sensitivity. This reduces the former mushy/"dead" pedal feeling, instead returning a sensation of responsive, fine, direct control.


I assume you ment to say "moves less for a given amount of fluid" speed of movement is dependant on the speed you press the pedal. in this instance it will take approx 16% more pedal movement to move the pads by the same amount when compared to the standard brakes.
The amount of actual pedal movement is also dependant on other factors like how flexable the caliper is and how far off the disc the pads run when the brakes are off.
Also the increase in brake force at the contact patch, the bit where the tyre meets the road, is around 35% more for the same line pressure hence the lighter pedal and more feel with these calipers and discs.

Nitroman, what was your previous post about, do you need a new cotter pin? or are you after the bits to fit this conversion?

Bob
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Re: Saab/Vectra Front Brake Upgrade

Postby racerstev » Sat 02.10.2010, 16:02

It would seem with 16% more travel needed but less pressure needed to stop the car like the 2 would offset each other.

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Re: Saab/Vectra Front Brake Upgrade

Postby tweetdriver63 » Sat 02.10.2010, 17:33

Well, all technical BS aside, the pedal still has a lot of travel (though not really noticably more than before), it's still soft until after braking action starts (normal, I think), but once you start getting braking action the feel is quite a bit better than before and the improved stopping power is obvious. That's all I really care about. The feel and travel of the pedal is something you just get used to. I know that if I put my foot to the floor, my car is going to stop, and it's going to stop quickly. That confidence in the ability to make an emergency stop is something I never had in this car before.

I recommend this upgrade for anybody who just doesn't have the dinero sitting around to buy one of the more expensive kits.
Chris
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Re: Saab/Vectra Front Brake Upgrade

Postby racerstev » Mon 04.10.2010, 14:19

Hmmm, I wonder if now would be the time to upgrade the master clyinder to a 1inch unit..

This would cut down on the travel and the larger brakes would offset the higher force you need
with the larger master.

Just a thought!

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Re: Saab/Vectra Front Brake Upgrade

Postby bobbrown » Mon 04.10.2010, 16:30

I think moving to a larger master cylinder would be a step backwards as the differance in caliper piston size is not as much as the change would be going to a 1" master cylinder; for example the 1" cylinder will give 30% less pressure for the same pedal input when compared to the standard master cylinder, where as the Vectra/Saab conversion is only a 16% change in caliper piston area. In terms of volumetric change on the calipers then this is only 11% so a 30% change at the master cylinder is the wrong way to go.

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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Mon 04.10.2010, 17:28

I've been delaying the brake upgrade due to price ... how much would those bits you supply run me, Bob? We could probably muster up a few orders of them to reduce on shipping cost.
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Re: Saab/Vectra Front Brake Upgrade

Postby nsr250 » Mon 04.10.2010, 17:33

I'd be interested in this too.
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Re: Saab/Vectra Front Brake Upgrade

Postby bobbrown » Mon 04.10.2010, 17:49

I can do all the bits I supplied to tweetdriver63 for £37.00 including postage to the USA.

Note: You will need to get the discs redrilled to a 4 bolt pattern but they do not have to be that accurate as the holes are a clearance size for a 12mm bolt I drill them 1/2" (12.7mm) (5 holes are 12.8mm ) and the holes on the original disc are 14.2mm as it is the clamp load that holds them in place not the bolts.


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Re: Saab/Vectra Front Brake Upgrade

Postby racerstev » Mon 04.10.2010, 19:57

Thanks Bob, got it!

I'd be in on this as well.

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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Mon 04.10.2010, 20:32

Why don't we setup a list then, I'll be happy to collect and re-ship out here in the states.

1) lotos
2) nsr250
3) racerstev
4)

Bob - let me know if you'd prefer we not do it this way.
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Re: Saab/Vectra Front Brake Upgrade

Postby tweetdriver63 » Mon 04.10.2010, 20:45

So this thread can stay informational, I'm going to set up a group buy thread.
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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Mon 04.10.2010, 20:59

:cheers:
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Re: Saab/Vectra Front Brake Upgrade

Postby dunnlor » Tue 05.10.2010, 03:04

Chris,

What is the purpose of the hub-centric rings?
Do they move the wheels out, and if so, have you notice any difference in handling?

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Re: Saab/Vectra Front Brake Upgrade

Postby tweetdriver63 » Tue 05.10.2010, 03:16

dunnlor wrote:Chris,

What is the purpose of the hub-centric rings?
Do they move the wheels out, and if so, have you notice any difference in handling?

Tom


The discs have to be held exactly centered. The oem discs are centered by the interior diameter of the rotor hat fitting snugly around the hub. The subaru discs have a bigger interior diameter, so they are centered by the center bore. It is just slightly larger than the hub center it sits around, so the rings fill the gap to keep them perfectly centered. The wheel position is unaffected.
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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Tue 05.10.2010, 17:04

Did you use Bob's template to drill out the bolt pattern on the rotors?
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Re: Saab/Vectra Front Brake Upgrade

Postby bobbrown » Tue 05.10.2010, 17:29

I think Chris may have used the old discs as a guide.
If it is required I can make up a drilling jig or two which could be passed about which fits the new disc bolts through one of the existing holes and allows you to drill a pilot hole and then open that up and drill the hole for the keep screw and finally counter sink that one.
When I do them I use my milling machine and a rotary table with a jig to locate the disc, so it is just a case of using one hole as a datum and work from that only pain is changing the tools.

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Re: Saab/Vectra Front Brake Upgrade

Postby tweetdriver63 » Tue 05.10.2010, 18:16

Bob is correct. I had the discs that were on the car when I bought it in my garage. I took one of those, along with the subaru discs, to a local machine shop. They used it as a template and I could hold them responsible if they messed it up. I thought that was worth the $15 they charged since if I did it myself and f**ked up a disc I'd be S.O.L.
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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Tue 05.10.2010, 20:00

Hmm - that might be the route I take then. Seems cheap enough!
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Re: Saab/Vectra Front Brake Upgrade

Postby superbad » Tue 05.10.2010, 21:21

lotos wrote:Hmm - that might be the route I take then. Seems cheap enough!


If you want to combine with mine, that would make sense.
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Re: Saab/Vectra Front Brake Upgrade

Postby lotos » Tue 05.10.2010, 21:48

Works for me! I'm up for combining the trip to the machine shop too if you're game. And if you have the means to install this stuff... I'm there for that as well. I've got no room, no tools, and no talent :banana:
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