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MG MGF Technical - Big Brake Conversion

Anyone tried the big brake disc conversion kit from Mike Satur ? Not really happy with the current brakes on the 'F'. I've put on EBC greens but they still dont have that initial bite that I'm looking for. I've asked the dealer about the AP racing setup on the Trophy but they say they're nearly 900 !!. Thing is though they're a four piston caliper setup I've heard. Anyone any ideas where to source these or other bigger calipers than standard. Mines a 2000MY if it makes any difference.
Kieron

Also if you have 15" wheels you better make sure that the larger disk an caliper will fit. For the B&G and Mike Satur options the old VVC wheels and all MGF 16" wheels are OK, but the old MPi 15" wheels are not. I have no idea if these brakes will fit the 2000MY 15" wheels.
Tony Smith

Another question on a similar thread...

With a 98 VVC with orignal VVC alloy, if I fit the B&G upgrades, do I lose the ABS as with the trophy?

Paul
Paul

OK all of this is in the archive as it is a subject that crops up quite regularly.

Remember that the standard 240mm front vented disc was originally fitted to the Maestro and Montego 2.0 litre petrol cars. When I created 230 to 250bhp 16 valve Turbo conversions the braking needs were far more severe than any F. Partly due to the power. but mostly due to the FWD layout meaning that most of the weight was already on the front.

To counter the problem I and a friend created an alternative 280mm disc conversion that reused the standard caliper on a spacer bracket. The disc used was one from the G60 engined Golf and Corrado range as this is a 4 stud fixing whereby the same size disc on the VR6 range are 5 stud. The other reason for going up 40mm was to take into account the material thickness of the special caliper spacer, and ensure there was adequate material.

The effect on the FWD MGs was very, very significant and with so much commonality on the MGF it was obvious that this would be a far bigger market. I know most of the sources who offer a similar conversion for the MGF and confirm that the conversion follows the same basic pattern. I also have been operating with a 280mm disc conversion on my F for well over 12 months, along with green stuff pads.

The improvement was not as marked as the FWD, mainly due to the fact that the standard MGF has a wheel design that allows considerable airflow to pass through the wheel and so provides cooling. Additionally the greater weight on the rear of the F, plus the better brakes allows the rear brakes to actually do some productive work. Unlike the FWD rear brakes that are almost along for a ride.

Changing to the 280mm disc and retaining the original caliper means that the actual clamping of the disc remains the same, but the work generated is greater since the 20mm greater distance from the hub centre provides a longer lever. This means that the same pedal pressure actually provides greater work and stopping power. The next main advantage is that by having a disc that is so much larger you have a much greater mass for heat to be transferred through and then there is a much greater surface area for that heat to be dissipated.

This puts off the need for using such serious performance pads as some get by with when using the standard disc. It must be advised that whilst some do find the brake performance of pads such as Mintex 1177 and Red Stuff perfectly safe with the standard discs when cold, the use of the larger disc will almost certainly push this performance below what is legally and sensibly required.

The move to this size of disc does not upset the balance of the braking to such an extent that ABS functions are impaired. Certainly of the cars including mine, that have been running with this conversion, nothing other than normal (non intrusion) operation of the ABS has been seen and I have done some specirfic testing on mixed surfaces to confirm this.

Remember that the Trophy front brakes have increased by another 24mm to 304mm and also use 4 pot calipers with a much larger clamping area and pad contact. These calipers also have pistons either side of the disc so the clamping loads are better and sharper with less caliper distortion. The final point is that in none of the several press releases and other information released on the car is there any mention of matching changes to the rear brakes to provide a balance.

If the absence of ABS was said to be due to an imbalance then this would also be the case for normal braking with premature lock up of wheels at the front or rear, depending on the individual vehicle characterstics. No such imbalance exists and in any case ABS would actually be a more efficient way of controlling it rather than leave it with the driver. No I feel that the lack of ABS on the Trophy is firstly a specific engineering decision with marketing connections with the MacLaren F1, and secondly a usefull way of keeping the costs down.

As a comparison I have had over the last 9 months contact with a Rover 218iS converted into a concept that did actually precede the MG ZR160. However the brakes on this car retain a fully functioning ABS using massive 325mm front discs with equally large AP Racing 4 pots. The rears were increased to 280mm with standard calipers retained on spacers. 17" wheels were needed to clear these front brakes and as can be imagined the braking of this car was/is truelly awesome, with no imbalance whatsoever, and difficulty in cauing the ABS to activate. (Gravel paths confirm operation)

Finally the wheel choice. The main issue is the caliper outer bridge casting contacting the inner face of the wheel. There is enough room for the 280mm conversion under a 15" diameter wheel. VVC 5 spoke wheels have a more pronounced sculptured inner wheel shape that provides extra clearance closer to the outer rim section, just where you move the caliper into. The original 1.8i 6 spoke needs a spacer of about 6mm to clear.

All of the 16" wheels have enough room to drive a bus throught the gap, whilst the later 8 spoke and Steptronic (now called Stepspeed) 6 square spoke 15" wheels are an unknown, but believed to be OK.

If the AP Racing route is still desired then visit www.apracing.com and follow the links to Rover where you will find conversions for the MGF and Rover 200. For pricing you have to go to one of their approved dealers.

Rog
Roger Parker

I gather that there may be problems fitting the new 304mm AP racing brakes inside current MG wheel designs- the new wheels are sculptured to fit around the new larger disc and 4 pot caliper...

Rog is right about the smaller disc size and harder pads- paradoxically this works to our advantage as it ensures that there is a more rapid build up of heat. This means more efficient braking despite the use of competition pads. I have no doubt that Rog is spot on regarding the potential pit-falls of blindly fitting larger discs and harder pad materials- but the 280mm conversions appear to work well with EBC green stuff pads.

As for improving inital bite of the brakes, an alternative solution is to remove the damping of the pressure rise in the hydraulic system wrought by the flex of the rubber brake hoses: fit braided items, and consider the servo-stay braket. These, IMO, will bring more to improve pedal feel than would more expensive mods to brake discs... Unless, ofcourse, aesthetics are also a primary concern!

Rob
Rob Bell

Just a mention about Mike's Large disk conversion, he is currently getting a new design manufactured at a lower cost that the current 275 version. He said that they should fit in to the (old) standard 1.8i alloys, if they don't then a spacer of about 2mm is required to get the clearance required.

I'll be having this done as soon as its ready as my discs are knackered.

Just a question though, would there be any reason why the Larger front discs couldn't replace the rear disks also?

HTH


Steve.
Steve Childs

None that immediately spring to mind Steve- but there are a couple of considerations:

1. Brake balance. If one set of wheels lock up prematurely, then this is bad for braking performance- undoing the good work intended by the fitment of larger discs.

2. Glazing. The rear brakes are comparatively underused as the weight transfer from rear to front under braking means that most of the braking load is transfered to the front wheels. The MGF has a rear biased weight distribution that means that this is not such a significant issue- and those rear pads do get used. Of importance is the way that you drive. Gentle town driving can lead to seizure of the rear calipers and/or glazing of the discs/pads.

Porsches have large discs all round- admittedly marginally smaller at the rear, so it is possible to engineer a solution. However, as no kit has been engineered, you'll have to do this yourself- and I'm affraid that splapping front discs on the rear hub may not be the ideal solution :o/

Thinking aloud here, I would have thought that the rear discs would work better with less cooling than the fronts- so if the fronts are vented and cross drilled, the rear should be solid. An interesting combo would be the 304mm Trophy front discs/ AP racing 4 pot calipers with solid 280mm rear discs with standard sliding calipers... (need to keep the hand brake!)

just a thought

Rob
Rob Bell

Thanks guys, especially to Rog for that most comprehensive of postings. I think I'm going to inquire about the AP Racing Calipers and discs. I've heard that you can simply take calipers and discs off other Rovers such as the 600 because the measurement between the studs is 96mm rather than the standard 100mm ? Is this true ?
Kieron Sykes

Kieron,

Parts from 'Honda' Rovers such as the 200, 400, 600 and 800 will not fit the MGF because they have 100mm PCD.

Make sure you are sitting down when you enquire about the price of the AP brake kit!.

I've been trying to get decent brakes on my F for a few years now. I currently have the same set up as Roger, which looks good, but as Roger says is not really the solution.

The AP kit is too expensive to justify. I've been hoping that the Trophy brakes would finally be the answer - just have to hope that they fit behind the 16 inch six spoke wheels.

Paul
P9 VLS
Paul

What's the difference betwen the AP kit on the trophy and the AP kit that motobuild sell? I assume they where one and the same.


Steve.
Steve Childs

The kit available from AP has a 3 part disc/hub assembly whereas the disc on the Trophy is a one piece cast item - ie cheaper.

I believe (but I'm not 100% certain) that the calipers are the same on both.

Paul
P9 VLS
Paul

Having driven the Trophy and specifically tried the brakes in various test circumstances I can say that the resiult is stunningly good. The bite is a mite sharp for the first couple of applications but once your aware of this the brake performance and more importantly the increasing reserve is probably the most powerful aspect of the car.

In looking at the set up through the wheels I have a reasonable confidence that the currently available 16" wheels should leave enough clearance for the Trophy brakes to be fitted on other F's.

The concept of big front matched with big rears is quite feasible and used to good effect on the MG25 Concept that has been referred to before on this BBS. In this case the fronts use AP Racing calipers gripping a 325mm front disc and the rears are 280mm with the original standard rear caliper retained and spaced out. ABS is retained and unnafected. Apart from being yet another car with brakes and braking to drool over, the normal day to day traffic driving is perfectly normal until you want to stop quickly, then you have to look behind at the drips with normal brakes who won't be able to stop!!

Rog
Roger Parker

So can anybody confirm or deny that the Trophy Brakes will fit under non Trophy 16" wheels and whether they can be used with ABS? Somebody must know by now, the cars have been in Rover Showrooms for a couple of weeks...

Kieron "wanting big Red AP brakes" Lacey
Kier

Kier,

Not a 100% confirm or deny as I am also only going on hearsay but I am told by Techspeed that the AP calipers will not fit under standard 16" wheels and that the Trophy wheels are sculpted for that purpose. You can call Roy at Techspeed for more info or the source of his understanding to be absolutely sure.

Dave
Dave

From what Dave has found out, no, teh T160 brakes will not fit under 16" abby-style wheels. He's had T160 wheels fitted to his car in preparation for the later fitment of these discs/calipers- which are, apparently, available from B&G.

As to whether they'd work with ABS- why not? There should be no problems with ABS. The only potential problem I can foresee is that the larger brakes may cause premature activation of the system because they are not calibrated to work with such powerful front rotors. I guess that MG left ABS off the T160 as a marketing thing and to save money by leaving this equipment off the car.

Rob
Rob Bell

Sorry Dave- looks like you just beat me to it! ;o)
Rob Bell

Right, I'm off to find a quiet little corner to cry in! Only bought the Abby/Cup 16"ers last year. I don't think I can justify buying another set of wheels just to then go and spend even more wedge on brakes, to my wife, or to myself for that matter. Sniff, wail, sob etc. Oh well...

Thanks for the info' Guys, even if it wasn't what I wanted to hear.

Cheers

Kieron
Kier

This thread was discussed between 01/04/2001 and 10/04/2001

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.