How quickly do you stop?

Anonymous · Post by **Anonymous** » Sun Jan 30, 05 9:35 am

Hi all, you all know my car and the setup I have. (discs on the front, drums on the rear and a manual master cylinder).

I had a scary experience a while back where I just pulled up in time in front of someone in a newer car who obviously had better brakes, even though I thought my distancing was good. The brakes on my car are pretty good but nothing compared to modern cars, this is probably the same for most of you too.

I was reading a few topics on the old message board and also looking at the recent topic posted by Mogwai about charger brake conversion. It looks like some of you have discs all round already.

So, I was wondering what type of setups some of you have. How much does it cost, whats it like etc etc?

I know there will be a difference if you are looking from a racing perspective, or an originality persective, but im not too bothered about either, I just want to know what setup will stop quickest. Although if you can put in a newer lighter more efficient part then why not?

Comments please people...

Anonymous · Post by **Anonymous** » Sun Jan 30, 05 10:09 am

Hi Steve, good to hear from you. The cars did have a servo once upon a time, but it was removed for weight reasons (i think). Are the old mopar servos heavy?

Kev · Post by **Kev** » Sun Jan 30, 05 11:02 am

Any weight saving is weight saving!

I've got a remote servo off the Valiant, but unsure of condition.

MrNorm · Post by **MrNorm** » Sun Jan 30, 05 1:13 pm

A servo will not improve the braking ability of your car at all - just make the pedal effort lighter. Assuming you are OK giving the pedal as much welly as necessary, I'd stick with the manual route. (I actually have a servo but will not be using it - I want manual discs for the improved feel).

you could change the calipers or the master cylinder for ones with a different bore size, but again all you'd really be doing would be changing the braking effort - not the capability.

My personal view is that rear discs are more for show than whoa (did you see what I did there

). They really don't do that much work and the Mopar rear drums should be fine unless you're doing some serious repeated braking (i.e. on the track - and even there they should be fine for most applications). If you want better brakes start at the front.

If you really want better brakes, the cheapest route is to upgrade to the larger front discs (11.75), this is well documented (e.g. Mopar Action website). That's what I'm using. Or there are plenty of aftermarket kits using Viper or Porsche calipers. But they are pricey!!

One other alternative is to use better pads. Can't recall who makes 'em but you can get carbon, or metallic etc pads. Try Firm Feel.

Dave-R · Post by **Dave-R** » Sun Jan 30, 05 1:44 pm

I think Gavin has covered everything I would say on this. But I would also add that you have to take into account just how heavy these cars are.

A train has very good brakes but it takes a mile to bring one to a standstill from 60mph. It is the mass of the car that is the problem. You have to allow a bit more space than usual and think ahead a bit more.

Plus braking distances on modern cars are much better than on older cars. It was just not a big deal back then.

Did any of your wheels lock up during this braking?
If they did that would make the car travel further. If they didn't they might not be working as well as they could.

If just the fronts or just the backs locked up you need to adjust the front/rear bias.

Kev · Post by **Kev** » Sun Jan 30, 05 2:27 pm

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Anonymous · Post by **Anonymous** » Sun Jan 30, 05 5:56 pm

Well no my wheels didnt lock up and I got no problem with giving the brake pedal welly. I understand about the weight of the cars, reson why I ask is that I have seen a few Muscle cars with discs all round and wondered if this would improve matters.

Kev may know this car himself, there is a really clean Orange Pontiac GTO near me that has discs all round. If rear discs do nothing for the car then why did anyone bother fitting them, is it like you say because of the constant on / off braking?

Maybe I'll just buy an anchor...

Holly · Post by **Holly** » Sun Jan 30, 05 7:55 pm

Rear discs can give more braking power, especially under circle track conditions of on off on off etc. In reality though on a RWD car 75% of the braking is done by the front, if you uprated the back without the front they'd just lock, and you'd have to adjust the front/rear proportions to 'detune' them anyway.

My '72 has the larger discs and a servo, and it stops very quickly. Remember your car came with drums all 'round, and has been driven for most of it's life like that without problems - Dave did the swap over to discs, so if you uprate the front just a bit more it should be able to anchor up in very respectable fashion

I'd say this Pontiac is probably after the 'Pro Touring' look, where rear discs are an essential fashion statement!

Dave-R · Post by **Dave-R** » Sun Jan 30, 05 8:32 pm

Rear discs are more trouble than they are worth on a street car. The harder you brake the less weight is on the rear wheels. Drums are fine. It is the front brakes that do all the stopping. The bigger the disc the better. Steel braided hose helps too.

When was the last time your brake fluid was changed or bled? Make sure there is no air trapped in the calipers.

MrNorm · Post by **MrNorm** » Sun Jan 30, 05 10:24 pm

Now Now Steve!!

Can't really say much more, the mechanical facts speak for themselves!
Do an proper emergency stop with a servo assisted car and a non-servo assisted and you will not stop quicker with the servo. Simple as that.

Maximum braking happens just before wheel lockup, and you should be able to get to that with or without a servo. In fact, I might argue (OK, I will then

), that since the quickest way to stop is to just sense the onset on wheel lockup, back off until it stops, and go back on the brakes (i.e. feather them around the point of lockup), you could actually get BETTER braking without the servo, cos trying to get any feedback with a servo is like doing brain surgery with welding gloves on!

Find any Mopar owner who likes a bit of roundy round handling and the vast majority are not using servo assist!
Regardless of all of that, non-servo assisted Mopars are not that firm of a pedal anyway

By all means fit a servo if you want to reduce braking effort, but don't expect an improvement in braking performance (unless you weren't using the brakes you already had in the first place)

Alex · Post by **Alex** » Sun Jan 30, 05 10:45 pm

After driving many Mopars with and without servo's I tend to agree with Steve, with non servo brakes the amount of pressure required to lock the wheels is hard to apply, with a servo the wheels can be locked reasonably easily, also as fade sets in the servo pressures can help overcome the loss of retardation.

rear discs on a road car can be detrimental as the pads take to long to get to temp (if at all under normal driving) where the drums will find bote, often in the case of Mopars, too much to soon leading to rear wheel lockup, a bias valve is a big plus on these cars.

Anonymous · Post by **Anonymous** » Mon Jan 31, 05 7:54 am

dont know if this is relevant for Markies car but if it had a servo when new that has been removed has it got the correct push rod fitted (i think my charger takes a different 1 for servo and non servo cars).