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MG ZR ZS ZT Technical - Brake Upgrades

Front Only Brake Upgrades Increases Stopping Distance!

Double Dutch or not?

Paul
Paul Wiley

Sounds like gibberish to me too, surely a brake upgrade should REDUCE stopping distances!

:-)

SF
Scarlet Fever

Paul has obviously been on the pop again..........
Eric

Sounds like someone has been talking out of their rear caliper.
I've put some 309.7mm rotors and Wilwood 4 pots onto the front of my 220 GTi turbo and I can assure you that the braking distances have been dramatically reduced.
Gary
Gary Boxall


I suspect there is one theory that, in isolation, will prove that braking distances are increased wth front only upgrades.

Cannot comment myself as I (on my 'F) upgraded front callipers/pads *and* upgraded the rear pads. There was a significant improvement in stopping distances.
However, I suspect that there are plenty that will step forwad and say that the theory is pants. This will most probably because there are so many influencing factors coming into play.

My gut feeling is that any front only upgrade will *feel* better.... but that the distances are not reduced by nearly as much as people would think.

P.
Paul Nothard

>>My gut feeling is that any front only upgrade will *feel* better.... but that the distances are not reduced by nearly as much as people would think.<<

Paul
That will really depend on how much of an upgrade you do. On a front engined car the rear brakes are only really along for the ride and contribute probably only around 15 - 20% of the overall braking. Having gone up from 260mm with single sliding piston calipesr to my Wilwood set-up I can assure you that does not just 'feel better'. I have recorded -1g braking and am sure that on race tyres overall braking distances have been reduced by at least 40 odd %. When I fit my recently arrived adjustable AVO coilovers, I expect braking distances to be reduced even further :o)
Gary
Gary Boxall


Gary,
I've got HiSpec Billet 4s and believe in using them. :) I too have found a massive decrease in braking distances and cannot recommend a front calliper upgrade enough. I did 'balance' it by using 1177 pads at the rear though.
I suspect that I could improve the distance more if I were to balance more scientifically... but, for now, for me, I'm very happy with the upgrades as is.

I think my comment was more aimed at pad changers.
The "feel" will be improved... but the braking distance may not be improved as much as they might expect.

P.


Paul Nothard

Paul

>>I think my comment was more aimed at pad changers.
The "feel" will be improved... but the braking distance may not be improved as much as they might expect.<<

Agreed :o)


Have to admit that I did increase the rear discs by 10mm purely as an exercise as it had never been done before. 310mm rotors and twin pots are on my 'to do' list at a later date. Quaife close ratio straight gears and ATB diff are more of a priority at the moment though ;o)
Gary
Gary Boxall

Paul,

Interested in Pad specs and reasoning behind recommendation. As piston diams of Hi Spec callipers are same effective area as OE for F, it is effective radius increase at front and pads at rear.

Just considering the following numbers game based loosely on F.

OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear

Maximum front tyre grip at point just before lock up 1500lbs

So OE Front 1500 rear 1000 total 2500lb of stopping force

Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!

The assumptions are on the limit braking and a matched properly working system to start.

Paul
Paul Wiley

Hi Paul,

Interesting debate going on about brakes. :-)

Although my experience is with my 'F... the ideas equally apply to Z cars.

I can see the logic behind stopping distances *increasing* with certain combinations.

The order of my upgrades was interesting and to a certain extent explains my choices:
o Of course, I started with OEM all round
o I wanted to upgrade the brakes but due to MSA regs I could only the pads were free. I upgraded straight to 1177 pads all round.
This drastically improved the braking when on-track. Braking distances were roughly measured and they decreased. The balance seemed (to my untrained eye) to be fine.
o I broke the front calliper (going into Quary at Castle Coombe at full tilt!!!) and needed to fix my brakes.
I chose the HiSpec route as they were a reasonable price and fitted under 15" rims. I kept my 1177s at the rear and moved to 1155s at the front on the advice of the guys at HiSpec - to try to keep the balance.

Anyways... having got to the situation where I've upgraded both fronts and rears in some way, I find that the stopping distance "feels" at least as good as having 1177s all round... and I'd personally say it feels better.

Unfortunatly I've no facts either way. But from braking alongside Rob (with his 1177s all round) on track it certainly seemed that I was able to scrub off speed faster.

So whilst I can see where you're coming from with your rough and ready calculations... I can only go on what I have found.

(This of course completely excluded the improvements that I have found with pedal feel using the HiSpec fronts.)

Can you explain my findings through the calculations?
Would I get even better braking if I were to downgrade the pads at the rear and upgraded the disk size and/or calliper?
Should this thread move to the F technical BBS? :-)

Cheers,
Paul
Paul Nothard

Paul,

There are lots of variables so theory is non car specific.

On F board Rob has been running specific F calculations.

With classic cars it could be drums all round!

Paul
Paul

This thread was discussed between 19/01/2004 and 25/01/2004

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