Neil Smalley

Seems an odd question. But is there any difference in the braking distances for an uprated 4 pot kit, as opposed to the standard 4 pot kit?

I realise that uprated 4 pot kits will have minimal fade, but for average use(I.e motorway and a few A roads) is there that much difference in the braking distances required?

Anyone done any comparisons?

When cold

E.g Std 4 pot 60-0=x metres
AP 4 Pot kit..60-0=y metres
AP 6 Pot kit..60-0=z metres

When warm

E.g Std 4 pot 60-0=x metres
AP 4 Pot kit..60-0=y metres
AP 6 Pot kit..60-0=z metres

When on a mission

E.g Std 4 pot 60-0=x metres
AP 4 Pot kit..60-0=y metres
AP 6 Pot kit..60-0=z metres

Simplistic question, but I don't want to spend 1500 quid on something that will make minimal difference in sensible road driving conditions.

Hoppy

Neil, I too thought the main benefit of big brake upgrades was repeated stopping ability.

My APR 6-pots certainly do that, but they also have stupendous power, great feel and control. Hit them at 100mph and the ABS bangs away immediately - ie they have more bite than the tyres have grip.

I can't answer your braking distance questions, but I can tell you that I've done 100-0 in 3.25 seconds, and they'll do 3.3 or 3.4 sec stops for as long as you can hold on.

I did those tests at Bruntingthorpe. For God's sake don't try it on the road as it is incredibly violent, and way beyond the car's designed performance limit. About 1.4g, I think.

Absolutely brilliant brakes.

Richard

PS Cue AndyMc...

Final comment. Everyone talks about 4-pot this and 6-pot that as if it is the calipers that make all the difference, or simply fitting up-rated pads will transform the car. Great brakes have a balanced package of calipers, pads and especially the DISCS for big stopping power.

[This message has been edited by Hoppy (edited 04 May 2001).]

SteveB

iTrader: (1)

Nail,

Can't comment on AP kit as I decided on the Prodrive/Alcon set up. These brakes really are fantastic, when i first had them fitted there was a specific bed in procedure - 10 stops from 60 to just rolling and then 10 from 70. Well, so chuffed was I after the first ten stops, I went back home to give the wife a demo - after 3 stops from 70mph we had return home because she was complaining of a headache because all the blood was rushing to her head !!

Steve.

AndyMc

Hello Neil

I can't answer your questions about stopping distances but I have compared my MY98 fitted with the 304mm AP kit with my mates Corrado VR6.The Corrado has 280mm discs and 1 pot calipers.
We both hit the brakes side by side at about 80 mph and each time I stopped about one car length before him,even after about six attempts the results were still the same.So the AP kit was better but not significantly so under conditions similar to those that you mention.I'm sure that from higher speeds and with prolonged use they would be much better.

The AP's do have a better pedal feel but still need a hefty shove to do a big stop!

Like Hoppy I have tried some 100-0 Mph tests and average about 3.9 seconds with a best of 3.6.

We are not too sure why his car (MY00) stops quicker than mine but he does have better rear pads and maybe a later version of ABS.His Pagid Blue pads may also develop full braking power sooner than my Jap ZX's.

Andy

GEJL

Digging up some very old basic engineering stuff, but won't one of the key factors here be the tyres? Assuming you're braking hard enough to trigger the ABS right from the start, then the only variable left is the friction between the tyre and the road?

I guess the flaw in that assumption is that the pressure required to get the wheels to the point of locking (i.e. to trigger the ABS) is what changes with different calipers and pad materials. Less pressure required with more pots etc.?

Hoppy, what tyres are you on? Pulling -1.4g is pretty impressive, given -1g is meant to be the maximum possible (though I do remember something about dynamic friction being greater than static friction - i.e. a locked vs. a decelerating wheel). I'm not arguing with your figures (I did the maths to check), just wondered how you got them!

And isn't fade due to overheating of the discs and/or pads? Therefore I'd have thought the size and material of the disks and pads was more important than the calipers - but I presume that your typical 6-pot set-up uses larger disks and larger pads...

Going round in circles here; should probably get back to work!

TRIGGER

Tyres obviously have a huge impact - so does suspension and the general setup of the car. Provided brakes arent overheated all our brakes will lock the wheels up - so then it comes down to transfering that force to the road - just look at Stef braking last year with slicks on !!

Hoppy

Yeah, 1.4g is good. Well chuffed. And I'm sure the brakes have still more to give. The limiting factor is the tyre/road grip, which triggers the ABS immediately.

The reason that Andy Mc and I have these comparitive figures is that he bought my 4-pot kit when I upgraded to 6-pots. Andy is also a bit of a wizard in the physics department and he's done all the g-force calculations. In fact, he's come up with a load of fascinating (but completely useless!) kinetic energy data to further illustrate the absolutely massive power of these brakes. I just love that nerdy stuff! It's all in the ScoobyNews CD which, when it's finally finished, has got so much great info on it.

Andy and I have pondered as to why my 6-pot set up consistently performs better than his 4-pots. And it's not just that my brakes are bigger, given that the tyre/road grip and therefore the ABS appears to be the limiting factor. Andy has given a few possibilities above. Personally, I think it's the improved ABS on my UK00 car that makes the most difference. Both cars are fitted with Bridgestone S0-2 pp tyres (mine 17in, Andy's 16in).

I'm fairly certain that I could get my 100-0 time down to 3 secs dead with a) slicks, and b) using the mega-high-friction road test surface at MIRA. Maybe some carbon-metalic pads. But those kind of stops cannot be good for the car, and are obviously irrelevant for road driving. It is hard to describe how violent the experience is.

I doubt very much that any standard Scoob could get anywhere near those figures, given that Evo mag tested the MY01 Impreza at 4.8 sec 100-0mph. Standard brakes do not have the power, and they'll be fading badly towards the end of the stop with a pedal feeling like it's stuck in rice pudding. APR's big discs (for leverage) and width (for cooling) offer maximum fade resistance time after time.

To anyone thinking of seriously upgrading their brakes, I'd say Go For It! My APR kit has added a whole new dimension of driving enjoyment, and skill. The power and fade resistance, especially on track days, coupled with quite a light pedal on my 6-pots, means that I (the driver) am the limiting factor in how well the car stops. It's great fun testing yourself against the ABS - how hard can I brake before the ABS bales me out of trouble?

Jeez, can I waffle. Sorry

Richard.