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MG ZR ZS ZT Technical - ABS and upgrades

What changes can be made without making the ABS or EBD less efficient or how do you upgrade the ABS EDB systems.

Change tyres to sticky tyres
Change wheels lower profile altering Circumference
Increase brake disc diam
Increase Pots volume change
Increase piston diams
lower car
Stiffer springs


Paul Wiley

Within reason, you can make almost any change while keeping the ABS.

On my 'F I have uprated the front brakes to HiSpec 4 pot thangs and kept the ABS as it. It works without problem. I've not yet needed to uprate the master cylinder. One thing to watch is keeping the balance correct... if you do not the rears (for example) may lock up quickly and ABS will kick in way too early.

Personally, on the ZTT, I'd only go for better tyres and friction material. But then again, I find the brakes on the ZTT good enough for my purposes.

Soz I can't help more.

Paul Nothard


What was disc diam and piston diam increase over OE F brakes?

Thanks Paul
Paul Wiley


(Note that it was my MGF that has uprated brakes. We're on the Z forum here. :-) Ooops!)

Anyways, they've got 285mm disks and 4-pot calipers running Mintex 1155 material at the front. OEM disks are 240mm. No idea about dimensions of the OEM single pot callipers but the new ones are 4 x 38.6mm.
If you have 16" rims you can take the bigger disks. I prefer my 15" rims and am more than happy with the braking performance I get. Brakes are hammered on many a track day as others will testify.

Rears are standard but running 1177 material.

See for details and look at the "285/24 BILLET 4" kit.

Paul Nothard

I am not 100% sure but I think you will find that the original MGF caliper piston diameter is 54mm with the master being 23.8mm.

Changing brake components will have little effect on the operation of ABS as this system starts to operate when individual wheel speeds start to vary so that once a wheel is running around 20% slower than the others then this will be interpretted as a potential lock up about to happen on that slowest wheel. If modifications to the braking system are done with balance then the car should slow more effectively under braking during which time the wheels will still be turning quite evenly.

This of course means that you have to keep the balance between front and rear with tyre to road surface grip, plus consider aspects of increased weight transfer from rear to front. Fortunately most modern systems have variable rate control to adjust for this, so reducing the greater likelyhood of rear wheel lock up under conditions of greater weight transfer.

Quite how EBD may be affected I an not sure.

Roger Parker

As I understand ABS (not well at all) the system needs to calculate a reduction in pressure to prevent the wheel locking. This is based on the OE brake system. By increasing pressure volume and pressure torque of system these calculation may not be valid by releasing too much pressure and too much braking capability, the system although recalcultes it ends up so to speak 1 step behind.

Just wondering how far you can uprate brakes before hitting this sort of problem.

The increase in disc size adds say 20% more torque but ABS appears to cope OK

If Hi spec brakes are using 1.5 in diam pistons, this is about same as 54mm OE so P-V not effected.


Paul Wiley

This thread was discussed between 04/01/2004 and 14/01/2004

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