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MG MGF Technical - A.P. 4 pot calipers

Came back from MS yesterday with my tail between my legs.Had gone to have 304mm discs and AP calipers fitted on my TF135.Car has 16" square spoke alloys.Was told they would fit by using a 4mm spacer,and, I've also seen 2mm spacer mentioned in previous threads.THEY WON'T. Mike tried a 7mm spacer,no joy.Reckoned it would need at least 10mm.IMO 20mm on the front track is OTT.So, unless I get a set of 160/Trophy ally's,I'm not going to get my 4 pots.I wish people wouldn't throw figures about when they havn't actually done the job. Regards.
H.R. Bridge

Will be Trying to fit my MGF Centre 1st prize Trophy 4 pot's and 305mm disc's tommorrow,will be touch and go as have 16" 7.5 TSW's, may also have to get Trophy alloys,will soon find out,Still Staggered by this Prize,in B & G catalogue this set is priced at 695 Wow :-)
DC Morris T6 DCM

Update, just finished fitting my prize 4pots over TSW alloys,and just one tiny prob had to take off lead strip balance weight as wouldn't clear caliper,took off and now great,will get wheels rebalanced tommorrow and they can reposition new weights,and they look brill ,what a job to get old discs off though, Dave :-))
DC Morris T6 DCM

Great news Dave! :o))Look forward to seeing your wheel/brake combination! :o)

Roy - thanks for the confirmation regarding the square spoke alloys. Tim and I were playing with these, and reckon that the Abingdon style 16" 6-spoke alloys are a no-no with these calipers as well. The only ones that will with that 4mm spacer are tbe Multispokes (Nik and Anita's car) - and I gather that the caliper needed a 'little adjustment' to fit too... ;o)
Rob Bell

Lucky you, Dave. You can go off people you know.Now I'm thinking do I go for 280mm discs with std calipers.Is it worth it? I'll still have the same pad contact won't I?. Must say I'm horrified at the disc wear at 16k, what do MGR use, Jelly?! Regards.
H.R. Bridge


But which pads to use with the 4 pot calipers ?
After my service said the dealer said there was
about 3mm left on the pads and they would need
to be replaced soon.

Which pads do I go for ?

Standard from MG (ap ???) or something exotic from
Mike's range ?

Paul Waine

Well,when mine are to be replaced,prob well before due, i think i will be going for green stuff,not only a big reduction in brake dust on wheels but increase stopping power by appox 20%,cost about
DC Morris T6 DCM

>>Now I'm thinking do I go for 280mm discs with std calipers.Is it worth it? I'll still have the same pad contact won't I?<<

No - the pad contact with standard calipers on a 280mm disc is NOT the same: because the standard caliper is designed for a smaller disc, it doesn't have the depth between the calipers to fit over the larger disc: result is the pad overlies the discs, and the contact surface reduced. :o(

Good news is that the leverage effect is greater - which may compensate for the reduced contact surface - and you have a much larger cooling surface = good news for cooling on track work: much less likely to suffer pad fade.

Worth it? Debateable, as there are some superb pad materials that work very well with the standard discs and calipers. But if you were to upgrade the calipers (no one has tried the AP racing calipers with the 280mm discs yet), then the conversion would be much more worth while.
Rob Bell

Thanks, Rob.So AP, calipers would go with 280mm discs,burning question is, would they go behind my 6 spokes?! Ironically, I could have bought a pair of new AP'S and pads today for 250, at the north west classic car show.In hindsight, the MGR sportspack (A.P's,big discs,A.B.S.,11 spoke ally's)is exellent value.Unfortunately I much prefer the looks of the 6 spokes,just need a way of fitting those big juicy 4 pots. Regards.
H.R. Bridge

<No - the pad contact with standard calipers on a 280mm disc is NOT the same: because the standard caliper is designed for a smaller disc, it doesn't have the depth between the calipers to fit over the larger disc: result is the pad overlies the discs, and the contact surface reduced. :o(>
Would disagree with that statement Rob, at least with the kit I manufacture the brake pad contact does not overlie the disc, in fact the contact surface on the standard disc is inbord and leaves a lip on the edge of the disc, not so good when fitting new pads.
No point in trying to fit AP calipers to 280 discs as they are designed for a 304mm disc and still would not fit behind 6 spoke alloys.
For no fade use the ceramic or carbon ceramic pads in AP calipers, am trying to get some ceramic pads made for the standard calipers which would cure track day fade on the usual pad choices.
Roy if it is just looks your are after put some spacers on to clear the calipers or get a Merc or similar;-)

Now I'm thinking do I go for 280mm discs with std calipers.Is it worth it?

I have these on my car.

For asthetics - yes, for improvement to braking performance - no.


Question for Mike. Can you confirm that your kit will allow the use of 280 disks, with standard calipers under 15" wheels. (Sorry if I'v got the wrong end of the stick).

If this is this case, how much is your kit.

I would have thought that the 280 disk would provide greated leverage and therefore be an improvement.


Mike, let me know when std size ceramic pads are available, as you say, I'll probably still need new discs because of the lip on the rapidly disapearing MGR jelly one's.If you mean 10mm spacers for A.P's I still think it's OTT."looks only, Merc,!" didn't realise you had me down as a posing git,Mike.Two cars that will never appear on my list,Merc, and Bee-Emm(perhaps a 300sl Gull-Wing!),just a personal thing.Didn't realise when I bought my TF that I was signing up to MGR's R&D programme! perhaps we should all start sending them a bill. Regards.
H.R. Bridge

With regard to AP calipers and 280mm discs - I suspect that Mike is quite right Roy: the AP callipers really are very 'chunky' and wide, and may very well interfere with the inside of the wheel spokes. :o( I was hoping that by moving the callipers radially inward and away from the inner circumference of the alloy wheel that you'd free up sufficient space for them inside those lovely 6-spoke wheels... It *may* be possible, but I do not know for sure one way or the other :o( Mike may well have attempted this fitment, so he's "the man in the know." Mike's comment regarding a calliper designed for a 304mm disc on a 280mm disc is well made - and is much the same argument as I made regarding a calliper designed for a 240mm disc on a 280mm one...

Mike, good to hear that your kit functions as it should: certainly other kits from 'certain sources who'll remain nameless' are not so well designed :o(

Roy, the other option of course, is Mike's 280mm disc and 4-pot calliper kit that are designed to work together ( - halfway down the page). You don't get the MG logo, but the calliper still looks superb and doubtless functions superbly. Andy 'SF' Phillips is a fan!

Steve, Mike's 280mm disc conversion DOES fit under 15" wheels - I've seen both his car and others with this disc fitted. But in each case with standard callipers. To go for the 4-pot callipers as well, would probably require the wheel size to be upgraded - although Mike can confirm this for you.
Rob Bell

Rob, when I was at Mike's he couldn't get his own 4 pots to fit behind the 6 spokes, or I would have gone for that option. Regards.
H.R. Bridge

Ah. Sorry to hear that Roy: that IS a problem.

Time to change the wheels perhaps?
Rob Bell

Roy, just a thought. The Lucas Variety type sliding calliper is not a design that is exclusive to MGR - indeed, most cars manufactured in Europe use the same design of calliper.

What you want is a caliper is a larger pad surface. Obviously, having a 'multi-pot' design is best, but the single pot sliding caliper is an efficient enough design, and is packaged into a much smaller volume. So you want a calliper for a larger disc. Look at the MGZT (or Rover75) and you'll find a much larger disc/caliper arrangement. These could be used with a suitable bracket.

I was thinking along these lines for replacement rear calipers with a handbrake mechanism, but the same thing could apply to the fronts as well: an avenue worth exploring I think.
Rob Bell

A picture from the SF forever site of the MS 4 pot calipers and 280mm disc:

>> <<

For information.


This is a picture of the same set up, but from behind so you can see how they are attached to the hub. I am not sure, but I suspect the AP calipers attach in the same manner (i.e. utilising the same attachement points) and therefore fitting a smaller (280mm) disc will not move the caliper away from the rim as the caliper is attached to the hub - QED

>> <<

Scarlet Fever

Good pix Andy :o)

To fit the standard calliper over 280mm discs, there is an adapter that spaces out the caliper away from the standard mounting point that you've highlighted.

Point made though: the AP callipers bolt directly to the standard hub mounts (as I am sure that Dave Morris will tell us). My cunning plan with the AP callipers would only have worked if they were mounted on an adapter plate. If so, you could replace with something smaller to move the calliper into a position appropriate for a smaller disc.

Ho hum.

But some suitably sized sliding callipers would work - assuming that something of suitable size and offset could be found?
Rob Bell

Believe it or not ,Rob, I was sat next to a Rover 25 in traffic, a few days ago, and, with my now manic obsession with calipers etc. I thought ,"I'm sure those calipers and discs are larger than those fitted to the F/TF." Doesn't the F/TF use the same sub-frame, hub assy' or,as usual, is there something I'm missing.Can't understand why MGR would put smaller brakes on the F/TF than their "cooking" model. Will have to look at some MGR tech-specs. Regards.
H.R. Bridge

Roy, You're right: the MG ZR 160 uses much larger discs than either the MGF or non-sportspack TF!

Front diameter is 282mm, and rear is 260mm.

Calipers therefore made to suit.

Unfortunately, R200/25/ZR discs are not a straight swap: there's that old chestnut of PCD to consider: 100mm on the R200 derivatives versus 95.25mm on the F derivatives.

However, the discs can be taken to an engineering shop for new holes to be drilled in the bell of the disc to match the F PCD. The bell depth is another dimention that needs to be considered. I don't know this dimention, but given the similarity of a number of MGR group products to VAG in the braking department, there is a good chance that this dimention is suitable.

The calipers used on the ZR are of course mated to appropriately sized discs - complete with handbrake mechanism at the rear. Question is: can they be mated to the Metro-derived hubs on the F?

Having 282mm and 260mm discs front and rear is a useful improvement over 240mm all round.

In fact, if it were so easy, why hasn't MG done it??? There must be a pitfall somewhere...
Rob Bell

This thread was discussed between 22/08/2003 and 02/09/2003

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