Spit rear disc conversion

[juppy]

In May 2015 a member was talking to me and send pictures of their MGF rear disc conversion, I have however managed to lose the email and contact details. If anyone recognises the pictures as theirs or know who it is, could you be so kind as to get in touch with me at the club shop.

Thanks.

[GT6M]

I think ye will find that the rears are no braking as weel as the drums.

and, will probly fin ott that yer brake pedal is going along way doon,

 

If so, there are fixes. for both.

 

 

M

[JohnD]

I went the whole hog and fitted MGF uprights, with the MGF disc brake assembly.

I was ready for major changes in the braking profile, and to fit a different master cylinder, or a pressure limiting valve to the rear circuit but in fact the car remains in good balance without any mods.

 

Is your comment the result of experience, Marcus?

I'm surprised that you are so critical of rear disc brakes, which are inherently better at heat loss and at shedding water than drums, and just as effective at braking.

 

John

[GT6M]

Yes on me own MK1 version John

the discs too small, so did,nt really bite much.

 

Which was aboot the same size, or slightly bigger than the MGF ones

this why I said they be a few wee probs.

both braking, and pedal travel

 

I changed discs to 30 mm bigger,, thats 15 mm a side extra

so had to move caliper ootwards, to get onto edge of disc,

much better.braking noo.

 

Butt, the bit aboot the long brake travel,

OE rear pistionee,s are v small,  15 mm !!!  compared to a 33 mm piston x2

this meks yer pedal move along way on initail press,

sep if ye got a small MC fitted.

{ bigger MC will give less movement, Butt, also less power at the disc }

 

spot on after this, bigger disc for braking power

butt, leave it for a few mins,or next brake, and same agen, pedal goes along way doon.

 

A wee  add on mod to MC, and pedals solid all the time noo.

 

would nae go back to drums,

and as ye say, well balanced for my tastes too.

 

M

[krissto2015]

I would also be very keen to find out more regarding the conversion/photos at the top of this thread.  Does anyone out there know who did this?

Chris

[krissto2015]

_{Trying to keep this thread alive, as I think it would be useful to so many who wish to upgrade to a rear disc setup.  Can anyone confirm that the rear calipers used in the photos are indeed MGF/MGTF?  If so, which year and specific model?  Also, are the discs in the photos also MGF?  I can design my own steel bracketry, along the lines of the images, but getting the right stuff from the MG parts bin would help.}

[Clive]

Yes, that is mgf callipers and discs.

I believe they were the same throughout production.

I did my own conversion, be aware it is tricky to get the ideal position on the car, lots of stuff is in the way, and clearance to the 13 wheels is very tight.

No real reason to use mgf calipers either. If doing again I would look at golf alloy calipers as lighted. I know somebody be used sack versions too.

 

I deed many people like the idea of a disc conversion, but few are prepared to make the bits themselves. And fewer would want to make them for others!

[mrjpgray]

Hi All,

 

I converted my GT6 to have rear discs about 5 yrs ago and I would recommend the upgrade but only if you have already upgraded the fronts calipers as the bulk of the stopping power needs to come from the front. I used the MGF calipers and handbrake cables and having a proper handbrake is one of the best things about the upgrade!

 

After looking at different ways of mounting the capilers and reading about using MK2 Escort brackets I decided to get a local engineering firm to manufacture a pair of brackets in engineering quality aluminium.

 

I remember posting this on the old forum but not sure what I've done with the photos now.

 

Cheers, Jason.

[krissto2015]

Hello Jason,

Thanks for your response.  In reply, I already have a Caterham vented disc conversion for the front brakes -  and that is combined with a Tilton pedal box, with balance bar.  So, I have all manner of possibilities regarding master cylinder sizes/ratios and setup of the front/rear bias.  Before I finalise the spec of the car, a disc setup at the rear would be great.  My car has all the mods for a lightweight GT6 lower wishbone system, CV driveshafts etc., so my vertical links are of that type.  This is why I was so intrigued by the article that Garth posted, at the top of this thread.  Those pictures show a GT6 rear system.  Is your own conversion based on GT6 rear uprights?  My reason for asking all these favours is that I am running out of time and effort to try and develop all the bracketry myself - and it will speed things up if I can get hold of ideas/drawings/patterns from others.  My car already has a Toyota 16V engine/gearbox (my own work), competition Quaife ATB diff, rollcage and much more.  I just need help in easy ideas for the rear disc conversion.  Phew!

Chris

[Fasterandfuriouser]

Looks an interesting and worthwhile upgrade.

[krissto2015]

Yes, lots of work put into this car, but please may I make one more polite request that somebody out there supplies me with the patterns/drawings/sketches for the GT6 vertical link caliper brackets - to suit the MGF rear disc arrangement?  If not, I guess I will have to do it myself, using cardboard templates and all the trials and tribulations associated with getting them made.  I am now on the phase of getting the body prepped for paint and I am running out of time to build it up over the Winter for (hopefully) a few test days and hillclimbs in 2017, so every little helps.  Thanks in advance...

Chris

[Clive]

I made mine without templates. I used 6mm steel, cut into a square, and used a holesaw to cut a hole so it would fit snugly onto the VL. Drilled the holes to match the VL (ie make it like a brake backplate)

I then fitted the brake disc to the hub, and clamped the brake calliper into position. That took some time as location is difficult to get once you think about brake cables and so on.

Next, make a plate to bolt to the calliper, then measured out how much I needed space the calliper plate from the plate on the VL. I then cut a couple of bits of steel and welded into place in a stepped sort of structure, enabling good welds.

 

Think I have said this before, I would look for a light alloy calliper if doing this now.The MGF callipers are heavy, and are getting a bit thin on the ground if you want new. Look at the VW ones, or browse the internet to find something suitable. It doesn't matter what they come from as long as you can get a cable and that the calliper will fit. So choose something that uses a disc size similar to the MGF.

[krissto2015]

Thanks Clive.  In order to get the car on the road/track for next year, the quickest solution is the MGF rear setup.  The PCD for the disc/hub is the good-old-fashioned 95.25mm (3-3/4") as per all our small chassisTriumphs, so that helps.  I will also machine the VL to use the MGF wheel bearing, as I am fed up with fiddling around with shims/spacers in order to get the end-float correct.  Yes, the OE MGF calipers are not light, but they will do for now.  I also own a mid-engined Ginetta G32 1.9i, which uses O/E Sierra/Scorpio/Granada rear calipers and discs.  There are upgrades available from Hi-Spec to make the unsprung mass much more lightweight.  See http://www.hispeccalipers.co.uk/svault2si.html

In the longer term, this is probably what I will use on my G32 and also adapt to suit the MGF discs on my Spitfire/GT6.

Chris

[Clive]

My point is that there is nothing special or easier about using the MGF calipers. If you are making brackets, you can use any calioer that fits. And as you will need to make brake cables anyway, the ends should be fine. 

 

I have the Nick Jones setup on my spitfire. Very happy with it, and in fact the r100 driveshafts canbe used with a subaru diff and CV's should you decide to gown that route at a later date.

[hugh]

We have two cars with rear discs, one is mgf callipers with mgf discs this worked well with homemade brackets and shortened mgf cables, it did however need a bias valve on the rear to rebalance the system as it has hispec 4pot ultralites on the front with Capri 2.8 discs and lotus Elise 1144 pads . The second has the same front brakes but Willwood 4 pot hand brake type callipers on the back with willwood cables again shortened to fit and again on mgf discs, again a bias valve is essential to rebalance the breaking. Both have a 2.5-1 servo, advantage of the wilwoods is they will fit 13" wheels but are considerably more money to buy, wheel size is not an issue as both run 15" mgf wheels on freelander studs, basically you payes your money and its your choice

[Clive]

I got the MGF calipers under the 13" wheels (std spit type, and the wider 5 1/2j ones, BUT I had a set of 5 1/2j steels that used round head rivets where he rivets JUST fouled the calipers. Some alloys may well be tricky too)

[Alickross]

I have been on with a converion myself for a while now and as i had a doner mx5 most of the parts are mx5 but as in previous posts i have also used the mgf back disks as thay are a good fit and with the mx5 calipers and a slite modification to the hand brake lever there was no need to replace the original handbrake cable and the bracket is a simple box section 16 mm deep by 72mm internal size with a 4mm plate over it and apropreat holes then welded a 10mm back plate to that and hay presto bolts in to origonal location of old back plate .i have photos if any one intrested but dont know how to put them on hear.

[GT6M]

How have ye solved the problemo of the cable rubb,n on the spring tunnel.

at the bottom forward corner.

Most cars that use the calipers wid the arm at the side will ev this problemo

 

And, if yer using standard size MX5  discs, then im afraid to tell ye, that yer braking wont be much good.

and go bigger disc, which is of the Sport model, 30 mm bigger, then the cable will wear its self away quite fast, as it rubs even moer ont tunnel  Wid the Akibono calipers, I recon I could go upto 320 MM

then wheel is limiting factor

Been there fun it oot.

 

the ones t,use are the Akibono type, thee,s pull frae the center

so give alott moer room for the cable

 

And, wot ye gonna doo aboot the lonnnng brake pedal travel on initial take up,

got that covered !!

if not, then its not a v v nice symptom of a v v spongey like  brake , at brake on moments

 

M

[JohnD]

I cut off the corner, Matt - and welded in a patch.

This pic is a bit close to be clear - does it help?

 

John

[Clive]

Same sort of thing here John....

Do some people put the caliper behind the disc?