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MG MGF Technical - 280mm disc conversion

HJW Motorsport are pleased to announce the launch of our new 280mm front disc conversion kit for the MGF.

Developed in conjunction with Roger Parker, this kit is now available, to order, at £199 plus p&p.
Kit comprises; pair of cross-drilled front discs, machined aluminium caliper brackets, nuts bolts & washers.

EBC discs & uprated pads also available.

For further information or to order, please contact HJW Motorsport either by e-mail ( ) or phone (01838 200443).
HJW Motorsport.

Hurray! Nice one Hector!

Having ordered pads from Hector in the past, I can vouch for his excellent levels of customer care.

Incidently, Hector also retails 16" wheels for a smidge less than B&G... ;o)

Rob Bell

That's good news ...
"Developed by Roger Parker" is a top quality label !
I add that on my shopping list. Maybe in a few months ...
Do HJW offer credit card services ?

'Do HJW offer credit card services ?' - YES!
David Smith

Hector's web site is at

Mostly for FWD MGs at present...

Rob Bell

I'm biased - but they are very effective.

Roger Parker

Hi all ,

Have been "offline" quite some time for a specific reason but now both me and the F is on the road again... Regarding front disc upgrade to 280 mm I think this is the best spent 200 quids ever ! Althou I "rolled my own" due to acess to all needed tools/machinery I can only praise the feel when using the upgrade. There was really nothing wrong with my original brakes,first set of pads behaved great - even during trackevents. When they were repaced with same Rover made pads later on I got really worse brakes ! This leads me to belive that Rover as any other manufact. has several contractors for brakepads, all up to their standard but some better than others.
Together with PU-bushings , a 82 deg. C thermostat, decent tyres and some other changes the car gets better and better.

Finally a question for Rog; As the 280 mm dia discs can´t get as deep into the caliper as the 240mm ones what kind of pads should be used to get the sweept area a bit further from the rim and closer to the center ? No big problem but have noticed that my original pads are all the way out to the rim of discs and may perform a notch in the pads after some use.

Best regards , Carl.

Yes Carl that is a waste of potential swept area which at the moment I don't have an answer for. It was the same for the Maestro/Montego 280mm kit but there the caliper is slightly different and the pads slightly deeper. I will be looking at some pad options in the future but subject to a special batch of pads being made with deeper backings I think that we may end up having to live with this or consider a different caliper.

For those following this thread I would add that the loss of this small area of the disc doesn't detract from the benefits of the conversion. It just leaves room for further improvement before you change to a 305x28mm disc, four pot caliper conversion that just fits under the 16" wheel. No that isn't a current special kit it's one 'waiting in the wings'.


Roger Parker

If I understand well, this is due to the bigger radius of 280 discs that can't match the inner radius of the calipper (240 mm).
Won't the notch whose Carl's speaking about damage or make round the disc rim ?

And, question for Rog, which pads would you choose for the 280 conversion ? EBC green stuff ?


The potential pad problem we are talking about here is 'overhang'. This where the pads actually reach beyond the edge of the disc and as the pad wears there is a slither of pad which is left overhanging.

The first point I would make is that I don't like that situation, yet there are others as well placed as me who don't see that as a problem. I dislike that for two reasons. 1, the exposed lip is likely to break away sometime and this may break away some of the pad that is in the contact area of the disc and 2, I think it looks unprofessional and unfinished.

The main problem that anyone will have with a 280mm conversion is the adaption of the original caliper bridge piece, which is a casting machined to cater for the 240x22mm standard disc, bolts to the hub and carries the caliper. The machining leaves an appropriate radius to match the disc and when you go to a 280mm disc you also change the radius to one with a much flatter profile.

The tighter radius machined in the bridge means that without modification the bridge has to sit slightly further out to provide that extra couple of mm of clearance. This then places the pad friction material in a slightly overlapping position.

In my well proven 280mm conversion for the Maestro/Montego the spacer dimensions were done on the basis of the caliper sitting in nearly the same relative position as it was with the original disc. In fact we did move it very slightly closer to the disc edge as in standard form there was a 2mm or so unswept area between the pad contact area and the edge of the disc.

In the MGF kit this principle has been continued which means that the same principle of altering the machined radius in the caliper bridge also applies. This is best done by a machine, but at the other end of the scale a sharp file and patience achieves the same result.

As to pads I have specifically run with standard then Green Stuff before the change and I am in the process of completeing the same dual pad trials with the 280mm disc. With the 240bhp Maestro, where the weight was mainly forward and drums were hung at the back for the ride, most braking work was done by the front discs and so I settled then on a Mintex sport pad. (171 which have been replaced less well by 1144. I didn't try Green Stuff)

With the F the brakes are better to start with and there is far more weight at the rear so the back brakes do actually do some work. The fronts consequently work cooler than the same disc does on the Maestro. I have found so far that there is less advantage with the Green Stuff with the big disc, although there is an advantage with Green Stuff and the standard 240mm disc.

My feeling at the moment, and it is just a feeling at the moment, is that for road use the standard pad with the 280mm disc may well offer the better all round performance. Those like Rob who do a little Weekend Warrier work on the sports scene will probably be better with the Green Stuff.

I will be able to draw a better conclusion when I have covered more miles. The advantage is clear when you press the paedal and need less work to achieve the same stops. Then if you want more you just press that bit harder ands the brakes bite some more and the front dips more, then if you want even more you do the same again and it still responds all the way up to the limits of the tyres. It is the slightly reduced pedal effort and the greater depth of reserve that are the main advantages.

You derive real confidence in knowing that you have excellent retardation, and then some more in reserve. The only down side I have found is that on one specific occasion when someone did something stupid in front I was able to slow perfectly normally but I was worried about the car behind who was having a bit of front end twitch!!

Roger Parker

Just a word of caution about this kit.

Be aware that the cost saver 14 inch spare steel wheel wont fit over the enlarged disc and caliper, so you'll need to buy a proper alloy spare if you want a useable spare wheel.

Also the caliper is positioned very close to the wheel spokes on the pre YR2000 1.8i 15 inch wheel - in fact so close that you wouldn't want to fit the kit, unless the wheel can be moved 'outwards' somehow.

Pre YR2000 VVC owners and those with 16 inch wheels won't have a problem. Don't know about YR2000 15 inch wheels.

I presume this would also be the case with the big disc kits from Motobuild, Mike Satur, Moss and Brown & Gammon.

I've had this kit on my car for 300 miles, with standard pads. I have to say that I am not overly impressed by the improvement in performance. Having driven Robs car today with EBC Greens on standard discs I would say his car braked better than mine. So I'm putting the EBC Greens in my car next week.

Visually, however the larger discs look superb. Rob has taken some digital pictures today, hopefully they will appear on his website soon.

Well worth £200 for the improvement in looks - even if the improvement in performance turns out to be less than spectacular.


I can elaborate on the wheel issue some more now and conform that the PRE 2000 model year 6 spokes 1.8i wheels will need a spacer of 5mm otherwise the wheel WILL foul the caliper. (Alloy spacers of 3 and 5mm with universal PCD are widely available and cost about £8 per pair.

The 2000 model year 8 spokes have enough space to drive a bus between the wheel and caliper, and call me a synic, but I look at these and just wonder if the extra space was created to cater for a larger brake!!!

The 14" space saver can still be used for a spare, it's just that if you have a front puncture you have to swap a back wheel for the space saver then replace the front whith the wheel from the back. Somewhat inconvenient but quite practical.


Roger Parker

The 14" space saver can still be used for a spare, it's just that if you have a front puncture you have to swap a back wheel for the space saver then replace the front whith the wheel from the back. Somewhat inconvenient but quite practical.

Phew. I was begining to thisnk that all of a sudden the market for this conversion was going to disappear overnight. Thanks Roger for pointing out the obvious solution to the problem.


Pictures to be transfered onto a web site near you soon.

Aesthetically, these discs are awsome. See the pictures to make up your own mind...

Paul, I was thinking about why your brakes seemed so dissappointing. As you pointed out, the ABS cut prematurely every time the breaks were heavily applied (something thankfully absent with my new pads- EBC Green Stuff front, and EBC Kevlar rear). Intuitatively, I would have predicted that the new discs would be very much better than they were- but I suspect that you are still using the original pads already on the car? I wonder if these had glazed resulting in the poor and inconsistent braking performance? In which case, any new pad will be better... Just a thought.

Rog, on the subject of alternative sources of brake calipers, how about the four pot caliper from an Austin Princess/ Abassador? A very popular conversions for certain other British sports cars...

Rob Bell

This thread was discussed between 19/04/2000 and 24/04/2000

MG MGF Technical index

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