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MG MGF Technical - Big Brakes......more thoughts

I have looked at all the archives on this matter and would like to sound the experts out on the following potential conversion.

The "new" Cooper S has what seems to be the perfect change over disc. It is 22mm thick, 44mm offset and 276mm diameter. The 22mm and 44mm are the same as MGF. This would increse the diameter by 36mm. The PCD of the bolts is unknown but since they have a 4 bolt fixing it would not be hard to drill 4 new holes at the correct PCD (95.25mm) indexed around from the existing holes. The centre hole for location purposes is 64mm which would machine out to the required 66mm. This would give a good disc for our cars.

The rear disc have the same advantages.......the diameter is 276, it is solid and 10mm thick with a 44mm offset.

For front calipers I am looking at Mazda RX7 series 4. They are 4 piston and woul;d mount very easily on an adapter plate that requires no offset machined therein. It is designed for a 22mm disc with a diameter of 276mm! so all the swept areas etc would be fine.

The rear calipers would be the MGF rears suitable spaced with an offset machined plate.

This combination would seem to fit the bill in terms of increasing the braking all round not just at the front. The discs are available new at moderate cost and the Calipers are available s/h for next to nothing (at least here down under)compared to AP/MS/etc. It just requires a little machining by the local engineering shop.

Any thoughts..............?

d mottram

Sounds good, need to be a bit careful with the design of the spacer though - it needs to be able to handle a lot of force. Have a look at Mike Satur's website, he does some spacers and you may be able to get some ideas from there as to the design of your custom made ones.

Very interested in the results. :-)

SF
Scarlet Fever

Great research there David - perhaps the similarity between the Mini's brakes and those found on the MGF should not be surprising given who engineered the car (Rover ;o))

One question: why opt for Mazda brakes when presumably the Cooper S brake calipers could be used (especially at the rear?)Okay - the 4-pot design is a good answer to that question (LOL!) but perhaps use Mini rear calipers? We may find that the calipers might mount to the MGF rear hub without the need to resort to spacers/adpaters...

Will definitely be looking at this option as well now!

Cheers David :oD
Rob Bell


Will look tonight. :)

P.
Paul Nothard

sounds interesting
particlularly if you can get the bigger discs off the shelf...which is what I thught we could do all along and not go for heavily re-engineered VR6 discs etc...
Neil

I accessed a front caliper last night and offered it up to the existing mount and with a very simple flat adapter (no offset required) it looks OK at this stage.

I have ordered a Cooper S disc and when it arrives I will modify and fit it and will then know more clearly if the front will work.

I have not as yet addressed the rear. It will be interesting to hear from Neil as to the similarity or otherwise of the two rear calipers. I will probably stick to the MGF one with a suitable adapter if possible as I already have them and would not need to incur additional expense.

I will keep the BBS informed.

Regards.....David
david mottram

david,

what thickness is the plate? is it mounted in front or behind the current caliper fixation points? probably behind.

What is the price for these mazda calipers. I once was quoted for subaru 4-pot calipers. I don´t recall the price as it was excessively high,

cheer,
david
David Peters

Dave do you have any idea how much the Mazda caliper weighs? Are they alloy.
Ken Waring

David Peters..............I have not made a plate yet but it will not need any offset. It will be threaded and mount exactly where the MGF calipers was located (ie it would replace the caliper). Because the RX7 caliper has more offset in the caliper ears and it is normally bolted to a pair of lugs rather than having the threads in it like the MGF, the RX7 can simply be bolted the flat plate and the disc envelope will be in exaclty the same plane. The polate thickness will probably be 10-12mm or thereabouts. Don't get too excited until I have the actual disc in my hand and have actually mounted them all on the car. As we all know there is a long way between theory and practice. I am pursuing it vigorously. Just waiting for the discs to arrive.

Ken Waring............the calipers are alloy. I will weigh them in due course and let you know. They do not "feel" much heavier than the MGF caliper but will certainly be heavier when you include the larger pads as well.
d mottram

Ken,
Contrary to my earlier thoughts I have just weighed the calipers (albeit without the pads, pins, shims etc) and the RX7 alloy one is 2.5kg and the cast iron MGF one is 3kg.
d mottram

D Australia,
Interesting research but giving the fact that the MGF hubs are metro this would not be surprising.
If you want better braking without the hassle and hit and miss of drilling etc go to Brakes Australia and fit some E B C Green pads, braking problems forgotton ! you could also fit E B C Turbo grooved discs.
Look this up on your local web site.
Robert
R J Hemphill

Robert H

Thanks for that info re. EBC etc. I use the turbo discs and the green pads on both my wifes MGF and my Elise. They make a very good road combination. This exercise however is for my MGF Race car. I find that the braking with that combination is not really up to the standard I need to race. After a couple of really hard laps they start to go off and having also tried the other colours have decided that what I really need is to take a major step and increase both the disc diameter and move to 4 spots to try and get rid of the taper pad wear and caliper flex. Like everybody I want to do all this at minimal cost hence my need to use proprietory items and S/H ones as well where possible. It is also an interesting technical exercise for me which I enjoy. This weekend I am fabricating a pedal box with balance bar so that I can rid of the booster and strange cross-car actuation shaft. Apart from the weight saving it will hopefully get rid of some more flex and the boosted lack of feel that plagues all such systems. The original booster bracket still flexed too much more my liking even with the reinforcement bracket fitted by Techspeed when the car was built for the Japanese MG Race series.

Regards...............David
dmottram

How's the project coming along David? Have you had the Cooper discs offered up to the MGF hubs yet?

Robert - remember that the New Mini is not Metro based at all ;o) So the fact that so many of the dimensions are correct is actually quite surprising.
Rob Bell

Rob, all being well I pick up the discs in about 30 minutes from now. I am getting them through the back door from the manufacturer here (DBA.Disc Brakes Australia). Like you I am always surprised if things go as hoped. I have an expression I use a lot....."Time will tell". I will keep you posted. At this stage I am just finalising the design an fabrication of the pedal box and balance bar.

Regards....David
d mottram

Fingers crossed then David!

>>DBA.Disc Brakes Australia<<

Are these guys the OEM for the discs - or manufacturers of replacement discs for the local market? I wonder if they're prepared to drill out the correct PCD for you too? Probably not - but any machine shop should be able to help out :o)
Rob Bell

Rob nice to see you back

David please keep us all informed with this

Cheers

Neil
Neil W

Cheers Neil :o)

BTW spoke to Roy @ Techspeed - he spotted this thread too :o) Spoke briefly about calipers - and I wonder if the Mini Cooper S calipers will mount to the MGF hub carriers? In which case, this could prove to be quite an easy conversion... (which probably means that they won't! LOL)
Rob Bell

Well things have not gone as well as I would have hoped.

1. The discs fit easily. The PCD of the wheel studs is 100mm vs 92.25mm for the MGF. To mount the sample disc I drilled out the existing holes so that the disc just slips onto the studs and made a small annular ring to fit inside the disc and on the hab extension to ensure concentricity. So far so good.

2. The caliper was next fitted with a flat adapter plate so that it was located correctly over the disc. Getting a good feeling at this stage!

3. Offer up the 15" whell , not expecting it to fit and it didn't.

4. Offer up the 16" MGF Cup wheel, expecting it to fit and it didn't. The caliper fouled the spokes.....exactly what I was trying to avoid. The disc needs to be bigger so as to place the caliper further out at a larger radius so that it will fit inside the curve of the spoke of the wheel.

So where to from here? For the moment I will run the Cooper disc with the original MGF Caliper mounted on an adapter plate the same as Mike Satur does. This will at least give me a larger disc at the front which is a good thing but the slider caliper is always going to be problematic. I will go back to research the disc catalogue to see if I can find a 300mm or thereabouts disc of the correct offset etc. Otherwise I will have to have a pair of custom discs made for the front and perhaps transfer the Cooper discs to the rear (no hand brake........it is a race car after all ?)

Ah the joys of racing on a budget. Actually it is more the joy of experimenting and doing things oneself.

That's all for now folks. I will report on the next stage in the not to distant future,

Regards........David Mottram

d mottram

David,

were you able to measure the availabe spacing at 300mm diameter?

If the 16" wheels are cup ones, the spokes are well curved and at 300mm you could end up with an in more... I guess,

good luck.

David.
David Peters

better what the available spacing would be at 300mm
David Peters

Davi M,

how about this conversion. The problem is getting the genuine disks and machining fitting conversion brackets, though.
http://netcity3.web.hinet.net/UserData/donliang/300mmBrakeDisc.htm
Dieter K.

Dieter,
Already investigated this route on an earlier occasion. I got qouted 400 € per caliper from my local Subaru shop. So, this is no longer an option:-(

David

David Peters

ohhh ....poo!
Neil

>I got qouted 400 € per caliper

Yeeks !! :(
sounds like a second hand buy option only.
Dieter K.

David, how about the 282mm discs fitted to the MG ZR (and also ZS)? Not sure about the offset dimensions or disc thickness (is this info on the EPC?) - but perhaps your parts catalogue will contain the answers?

Good luck David - following your progress with much interest! :o)
Rob Bell

This thread was discussed between 04/12/2003 and 15/12/2003

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