280mm Front Brake Conversion - Opinions invited

2927 Views 25 Replies 12 Participants Last post by MGB281, 8 d ago

EllisoJo

Discussion Starter · Mar 3, 2022

I am still not happy with the mediocre braking effect of the standard 240mm brakes on my 2002 TF135. This is NOT a question of excessive pedal travel, just low braking effect, unless I use very considerable pedal force. I have standard 6-"Squarespoke" 15" wheels, and do not wish to do the "obvious" but expensive mod of switching to AP brakes, which would need the correct 16" wheels, new tyres as well as the cost of the 304 dia discs and callipers.

I am therefore considering buying a 280mm diameter disc conversion kit, as described in Roger Parker's excellent "Everyday Modifications for your MGF & TF". I see that MGFandTFmania, sell a kit for this upgrade, but I see (from a Tbar posting by "cairnsys" over 7 years ago)

Wheel Tire Automotive tire Motor vehicle Locking hubs

, that there is no mention of the spacer rings described by Roger Parker. These fit between the reference dia. on the MG hub and the larger hole on the VW Golf/Corrado disc. "cairnsys" also mentions that the hole(s) for the securing screws "were in the wrong place" Does anyone have recent experience with this kit, or any other upgrade to 280mm front discs? A picture from the excellent cairnsys "how to" is attached, this should explain what I am wittering about!

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Chris T

· #2 · Mar 3, 2022

First of all, when you brake do you feel that the fount brakes seem overwhelmed? If you do then the issue is often with the rear callipers are not working to full effect. I don’t know if you have ABS or not but this seems to be more the case F/TF’s without ABS.

No experience with the brake kit, however I wouldn't worry about things like the lack retaining screws.

Reactions: 1

EllisoJo

Discussion Starter · #3 · Mar 3, 2022

First thing I did was to have the whole braking system checked by my local garage (who I trust). They gave me the printout of the brake test which all looked O.K. I do not have the figures to hand, but I seem to remember that the rears were slightly more efficient than the fronts.

I do have ABS. When I did a brake test on a suitable quiet, straight road, it took MASSIVE pedal load to get ABS to cut-in, even on a slightly damp road! Rear discs were replaced about 4000 miles ago, and what looks like "Green Stuff" pads fitted. I have replaced front discs and pads recently, so still using brakes gently, butt they feel no more reassuring.

Man in the Car

· #4 · Mar 3, 2022

EllisoJo said:
.... "cairnsys" also mentions that the hole(s) for the securing screws "were in the wrong place"

cairnsys is correct with regard to the wheel stud holes - the VW Golf/Corrado have a wheel stud spacing of 4 x 100, so you would need to modify the holes to allow for the F/TFs closer PCD of 4 x 95.25. If done correctly (ie. only grinding the metal out where the wheel studs require it, and not simply drilling the entire hole out larger), there shouldn't be any problem once the wheels are on and tightened to clamp the disc in place.

Reactions: 1

david.c

· #5 · Mar 3, 2022

I fitted new calipers std pads discs & braided hoses, Bedded them in. Brakes were still crap. So I invested in the 280 conversion from Mike Sature bedded those in and was well impressed with them. I left the spacer rings for the disc centre off. The discs were OK with the 2 securing screws.

rogrover38

· #6 · Mar 3, 2022

EllisoJo said:
I am still not happy with the mediocre braking effect of the standard 240mm brakes on my 2002 TF135. This is NOT a question of excessive pedal travel, just low braking effect, unless I use very considerable pedal force. I have standard 6-"Squarespoke" 15" wheels, and do not wish to do the "obvious" but expensive mod of switching to AP brakes, which would need the correct 16" wheels, new tyres as well as the cost of the 304 dia discs and callipers.

I am therefore considering buying a 280mm diameter disc conversion kit, as described in Roger Parker's excellent "Everyday Modifications for your MGF & TF". I see that MGFandTFmania, sell a kit for this upgrade, but I see (from a Tbar posting by "cairnsys" over 7 years ago) View attachment 137763
, that there is no mention of the spacer rings described by Roger Parker. These fit between the reference dia. on the MG hub and the larger hole on the VW Golf/Corrado disc. "cairnsys" also mentions that the hole(s) for the securing screws "were in the wrong place" Does anyone have recent experience with this kit, or any other upgrade to 280mm front discs? A picture from the excellent cairnsys "how to" is attached, this should explain what I am wittering about!

Hi there ,
I too feel my braking is poor tho it passes the mot . A guy I bought a part for my rover 75 off told me that I should get someone to look under the bonnet of my tf while I press the brake hard to see if there is flexing where the brake unit is , he said it’s a common thing and that you can buy a kit to reinforce this and braking is much improved . I hoping to fit this when I get time , I’m sure the other members have ideas on this

EllisoJo

Discussion Starter · #7 · Mar 3, 2022

david.c said:
I fitted new calipers std pads discs & braided hoses, Bedded them in. Brakes were still crap. So I invested in the 280 conversion from Mike Sature bedded those in and was well impressed with them. I left the spacer rings for the disc centre off. The discs were OK with the 2 securing screws.

Thanks for this information David. Are you saying that Mike Satur still sells this 280mm conversion kit? How recently did you buy??

As regards the spacer rings, my thoughts are (for what they are worth!): Without the spacer rings, the discs are only located on the 4 studs (for the wheel attachment bolts) + from what you say, the 2 securing screws which locate into countersunk holes. I was trained (in engineering design) that locating on threaded studs or screws was bad practice, and every brake disc I have ever fitted has located onto a central spigot or ground "shoulder", so I think the spacer rings should be used, unless you believe they are not concentric or faulty in some way. Having said that, removing that spacer ring from the hub, if you ever decide to fit Standard discs 240 or 304mm, could be difficult once it has rusted-on.

EllisoJo

Discussion Starter · #8 · Mar 3, 2022

david.c said:
I left the spacer rings for the disc centre off. The discs were OK with the 2 securing screws.

Postscript to my previous comment: I have checked the Mike Satur site again and he no longer shows any FRONT 280mm conversion kit, but does list a different one for the rears. MGF Mania list a kit for the Fronts, but their picture shows disc with only one securing screw hole, which may be "left over" from the VW application, as it is in the wrong position relative to the new bolt holes on 3.75" PCD for the MG application. They do not list any spacer rings on the list of what comes with the kit, and do not mention fitting this spacer on their fitting instructions. Think I might be borrowing Father-in-Law's Myford Lathe and turning-up a couple of spacer rings!

david.c

· #9 · Mar 4, 2022

EllisoJo said:
Postscript to my previous comment: I have checked the Mike Satur site again and he no longer shows any FRONT 280mm conversion kit, but does list a different one for the rears. MGF Mania list a kit for the Fronts, but their picture shows disc with only one securing screw hole, which may be "left over" from the VW application, as it is in the wrong position relative to the new bolt holes on 3.75" PCD for the MG application. They do not list any spacer rings on the list of what comes with the kit, and do not mention fitting this spacer on their fitting instructions. Think I might be borrowing Father-in-Law's Myford Lathe and turning-up a couple of spacer rings!

Mg mania redrills the discs between the original holes locating the disc exactly. No spacer rings or locating screws required. As to when I got the 280 conversion, About 6/7 years ago

CabinetEnforcer

· #10 · Mar 4, 2022

EllisoJo said:
Postscript to my previous comment: I have checked the Mike Satur site again and he no longer shows any FRONT 280mm conversion kit, but does list a different one for the rears. MGF Mania list a kit for the Fronts, but their picture shows disc with only one securing screw hole, which may be "left over" from the VW application, as it is in the wrong position relative to the new bolt holes on 3.75" PCD for the MG application. They do not list any spacer rings on the list of what comes with the kit, and do not mention fitting this spacer on their fitting instructions. Think I might be borrowing Father-in-Law's Myford Lathe and turning-up a couple of spacer rings!

Yes, locating on the studs is bad practice. The disc locating screws are no more likely to be accurate however so I would not worry about those. Spigot rings do seem the obvious choice, though the standard discs don't use the central boss so it would be wise to check the spigots for concentricity before making any adaptor rings.

Don't be duped into thinking the 4pots and 304 discs are an upgrade, they may improve feel and fade resistance but provide no meaningful increase in power. The 280 conversion does actually increase braking power, you should consider doing the rears as well as the fronts to maintain balance.

The main issue with the brakes is that they have a very old fashioned weighting, requiring a lot of shove, most modern cars are massively over-servo'd which highlights this a lot. I found putting nice sticky trackday tyres on made the brakes feel an awful lot better.

EllisoJo

Discussion Starter · #11 · Mar 4, 2022

CabinetEnforcer said:
Yes, locating on the studs is bad practice. The disc locating screws are no more likely to be accurate however so I would not worry about those.

The only reason I would prefer to have the countersunk screws is that I want to check disc run-out as soon as I have the new discs fitted. I am pretty confident that the discs themselves will be "true", but any dirt, rust or any other damage on the hub mating surface will cause run-out. I have already "appropriated" the dial gauge and magnetic clamp from my Father-in-law's model engineering workshop, so I might as well do this check.
CAN ANYONE ADVISE WHAT THE THREAD IS ON THE WHEEL STUDS??

Once I know the thread, I could (obviously) use 4 plain bolts on these studs to hold the discs in place before the wheel is fitted. I have previously used the closed-end, standard wheel bolts, tightened just hand-tight, because I was not sure if the studs were bottoming-out on the blind inside end of the wheel nuts, or genuinely clamping the new disc surface. Plain nuts + washers, if I can find suitable sizes, would leave no doubt.

Hobby

· #12 · Mar 5, 2022

I fitted the 304mm with the 4 pot calipers and there was a massive difference in the braking. I have a lot more confidence now when going fast. She sticks to the road now on braking

Geoff11

· #13 · Mar 5, 2022

I just fitted a replacement set of rear oversize discs from MG Mania, they are from a ford st focus redrilled to suit mg hub , problem is there is no
Spacer ring to centre the disc on the hub , the discs are drilled so tight on the studs you will damage the threads if you hammered disc on ! I turned up a couple of spacer rings on my myford and drilled the holes to provide clearance over the studs,

Reactions: 1

EllisoJo

Discussion Starter · #14 · Mar 5, 2022

Geoff11 said:
I just fitted a replacement set of rear oversize discs from MG Mania, they are from a ford st focus redrilled to suit mg hub , problem is there is no
Spacer ring to centre the disc on the hub , the discs are drilled so tight on the studs you will damage the threads if you hammered disc on ! I turned up a couple of spacer rings on my myford and drilled the holes to provide clearance over the studs,

Yes, I am not surprised. There will always be some tolerance on the positioning of the 4 studs relative to each other. Different batches from the hub supplier may vary within (or maybe outside!) the allowed tolerance, so however accurately MG Mania drill those 4 stud holes, problems fitting on somebodies studs are inevitable.

EllisoJo

Discussion Starter · #15 · 2 mo ago

4

I have finally found, fitted and can report on the 280mm Front Disc conversion.

Tire Wheel Car Vehicle Automotive tire

Comparing the image of the 280mm discs with the 240mm std set-up below illustrates the difference in appearance, at least:

Tire Wheel Car Vehicle Automotive tire

The supplier I found (neither Mike Satur NOR MGFMania do the FRONT kit any more) was:

www.ebay.co.uk

MGF MGTF BIG FRONT BRAKE KIT 280,MM | eBay

Find many great new & used options and get the best deals for MGF MGTF BIG FRONT BRAKE KIT 280,MM at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

I am pleased with the fit & function of the kit. The brakes seem to give much more deceleration for a given pedal force, though as the weather has been so awful lately, I have driven the TF very little since fitting the kit.

Others considering this mod. need to know the following:
1. The standard 14" steel spare wheel DOES NOT FIT OVER THIS LARGER DISC & RE-POSITIONED CALLIPER! I ma in the process of finding & buying a good 15" square spoke wheel as a spare.

2. Despite what I said on earlier posts, I have not manufactured locating rings. When i measured the ID of the original 240mm discs, which I am (almost) certain were the O.E. Rover discs (only 22,00 miles when I removed them, and they were well-worn) I found that the disc ID was about 2mm larger than the diameter of the spigot on the hub, so the O.E. disc are NOT located by the spigot.

3. A few extra M12 steel washers are useful, probably essential to make the calliper carrier align perfectly (seem my comments to the supplier below).

Gas Auto part Composite material Nickel Metal

4 off M12 x 1.5 nuts are useful to hold the disc tightly against the hub face to check calliper carrier alignment and, if you want to check it, for disc run-out.

Crankset Automotive tire Motor vehicle Vehicle brake Tire

For those still interested, I made the following comments to the supplier "Kezzermuldooney":

I had to use TWO washers between the Al Alloy adaptor and the hub, to get the calliper carrier to align correctly with the disc. This was true O/S and nearside. Total 3 thin washers, 3 of your thick washers +2 intermediate size, from my own stock.
Different thicknesses of washers were needed (top versus bottom bolts) to align the carrier with even spacing either side of the disc.
I had anticipated the need to hold the disc tightly against the hub, so I had purchased 4 off M12x1.5 nuts, and I already had plenty of M12 washers.

In the light of points 1 & 2 above, can I suggest that it would be helpful to provide 8 off (or at least 6 off) of each thickness of washer in the kit. I was fortunate in having plenty of left-over 12mm washers from a previous job, but many (most??) purchasers of the kit would not be so lucky.

I used threadlock when finally fixing the brackets to the hubs. As this adaptor should never need to be removed, this seemed a wise precaution, would you agree?

I used the same Torque (85Nm) as specified in the manual, to tighten the adaptor to hub, and the calliper-to-adaptor bolts.

The need to use different thicknesses of washers to make the calliper align correctly with the disc (point 2 above) indicates that the hub surfaces the Al. Alloy adaptor is attached to are not machined “accurately”. To be fair to MG-Rover, the Al Alloy adaptor is attached to (and effectively positioned by) the two surfaces MG spot-faced to accept the heads of the M12 bolts, NOT the normal reference face used by the callipers. I suspect the machining tolerance for the face the calliper is normally attached to is much tighter. Inaccuracy/inconsistency of the spot-facing only effects the depth of penetration of the attachment bolts, which would only become a problem if it was wrong by a couple of mm.

Hopefully this information will be helpful for anyone else contemplating the 280mm front brake conversion.

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Reactions: 2

D4KGP

· #16 · 2 mo ago

EllisoJo said:
I have finally found, fitted and can report on the 280mm Front Disc conversion.
View attachment 139571
Comparing the image of the 280mm discs with the 240mm std set-up below illustrates the difference in appearance, at least:
View attachment 139572

The supplier I found (neither Mike Satur NOR MGFMania do the FRONT kit any more) was:

MGF MGTF BIG FRONT BRAKE KIT 280,MM | eBay

Find many great new & used options and get the best deals for MGF MGTF BIG FRONT BRAKE KIT 280,MM at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

I am pleased with the fit & function of the kit. The brakes seem to give much more deceleration for a given pedal force, though as the weather has been so awful lately, I have driven the TF very little since fitting the kit.

Others considering this mod. need to know the following:
1. The standard 14" steel spare wheel DOES NOT FIT OVER THIS LARGER DISC & RE-POSITIONED CALLIPER! I ma in the process of finding & buying a good 15" square spoke wheel as a spare.

2. Despite what I said on earlier posts, I have not manufactured locating rings. When i measured the ID of the original 240mm discs, which I am (almost) certain were the O.E. Rover discs (only 22,00 miles when I removed them, and they were well-worn) I found that the disc ID was about 2mm larger than the diameter of the spigot on the hub, so the O.E. disc are NOT located by the spigot.

3. A few extra M12 steel washers are useful, probably essential to make the calliper carrier align perfectly (seem my comments to the supplier below).
View attachment 139570
4 off M12 x 1.5 nuts are useful to hold the disc tightly against the hub face to check calliper carrier alignment and, if you want to check it, for disc run-out.
View attachment 139569
For those still interested, I made the following comments to the supplier "Kezzermuldooney":

I had to use TWO washers between the Al Alloy adaptor and the hub, to get the calliper carrier to align correctly with the disc. This was true O/S and nearside. Total 3 thin washers, 3 of your thick washers +2 intermediate size, from my own stock.

Different thicknesses of washers were needed (top versus bottom bolts) to align the carrier with even spacing either side of the disc.

I had anticipated the need to hold the disc tightly against the hub, so I had purchased 4 off M12x1.5 nuts, and I already had plenty of M12 washers.

In the light of points 1 & 2 above, can I suggest that it would be helpful to provide 8 off (or at least 6 off) of each thickness of washer in the kit. I was fortunate in having plenty of left-over 12mm washers from a previous job, but many (most??) purchasers of the kit would not be so lucky.

I used threadlock when finally fixing the brackets to the hubs. As this adaptor should never need to be removed, this seemed a wise precaution, would you agree?

I used the same Torque (85Nm) as specified in the manual, to tighten the adaptor to hub, and the calliper-to-adaptor bolts.

The need to use different thicknesses of washers to make the calliper align correctly with the disc (point 2 above) indicates that the hub surfaces the Al. Alloy adaptor is attached to are not machined “accurately”. To be fair to MG-Rover, the Al Alloy adaptor is attached to (and effectively positioned by) the two surfaces MG spot-faced to accept the heads of the M12 bolts, NOT the normal reference face used by the callipers. I suspect the machining tolerance for the face the calliper is normally attached to is much tighter. Inaccuracy/inconsistency of the spot-facing only effects the depth of penetration of the attachment bolts, which would only become a problem if it was wrong by a couple of mm.

Hopefully this information will be helpful for anyone else contemplating the 280mm front brake conversion.

Hi so have you managed to source a 15 inch square spoke wheel now? Because I see that you had two advertised on 22nd March for £80. Regards. D4KGP.

MGB281

· #17 · 2 mo ago

Cabinetenforcer hit the nail on the head, the AP304 combination is not an upgrade, yes they add a touch of bling but the piston area of those four tiny pistons (3526sqmm summer) is less than the area of the single pot piston ( 3620 summer) remember when calculating piston areas to double that of any single pot piston). They rely on a smaller clamping force on a larger OD brake disc to achieve a similar result. The 280mm discs are a great upgrade, buthe didn’t fully explain the need to push so heavily on the brake pedal though. The master cylinder bore on a MGF/TF is 23.8mm which is far greater than the more normal 19 or 22mm found on cars with 48mm caliper pistons so pedal travel is less but you need to push harder. Of course you could alter the ratio of pedal to master cylinder travel to get a similar effect.

MGB281

· #18 · 2 mo ago

Using a brake efficiency calculator like this one; Brake Bias Calculator | Master Cylinder Calculator You can see the effects of the changes that you have made or contemplating making. Whether doing it for real or to see what could be achieved I would suggest that you print out the results, ie original setup, big fronts and big front and rear. What you will see from the results each time is the absolute stopping power does not change but what changes is lower pedal pressure for the same braking effort. If you search the internet you will find that the typical FWD car (55/45 weight distribution) has bigger front discs than rears but mid and rear engined cars (45/55 weight distribution) tend to very close to equal sized discs front and rear which is exactly what MG did 28 years ago. It becomes clear that bigger rear brakes will better balance the braking.
One other factor to bear in mind is that the rear brake calipers were designed to work with 260 mm brake discs but the front ones were only for 240mm discs and depending on the mounting bracket may overhang the 280mm discs. For that reason I chose to use R53 Mini front calipers, they were used on the 295mm discs. It’s a very simple bracket to make, I used EN3b steel and even the brake pipes fit straight on.

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deepfat

· #19 · 2 mo ago

Ellisojo do you have the the locating screws fitted? I have all the bits to do this conversion but the locating screw holes don't line up and I'm not happy fitting them. I know people say they are not needed as the wheel clamps the disc but what happens if I'm changing the wheel in wet/cold conditions (it always is) a bit of muck gets trapped, when I pull away and brake I will think the wheels are falling off.

EllisoJo

Discussion Starter · #20 · 2 mo ago

deepfat said:
Ellisojo do you have the the locating screws fitted? I have all the bits to do this conversion but the locating screw holes don't line up and I'm not happy fitting them. I know people say they are not needed as the wheel clamps the disc but what happens if I'm changing the wheel in wet/cold conditions (it always is) a bit of muck gets trapped, when I pull away and brake I will think the wheels are falling off.

No, I did not fit any locating screws, in fact they cannot be fitted, because the new holes at 3.75" PCD were drilled at 90 degrees to the original 100mm PCD holes, so two of those original holes overlap where the locating screws need to go. IMO, the discs SHOULD be drilled with the "New" 3.75" PCD holes at 45 degrees to the original holes, so that proper , countersunk holes for the locating screws could also be drilled.

I had not thought about dirt potentially entering a gap between hub and disc while wheel-changing. Deepfat makes a good point. A possible "fix" might be to have someone hold the footbrake on before the wheel is unbolted. With a bit of luck, that MIGHT hold the disc in it's original position, and prevent a gap developing. Probably wishful thinking, and Murphy's law will mean that puncture WILL happen on the front tyre, AND I will be driving with no passenger at that time!

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