Big Brake Upgrade

Skipton01

Admin Team
Well, as many of you may know, I'm planning what could be the final mod for Tank, a brake upgrade to 312mm rotors, using effectively a set of TT front brakes.

The project has been prompted by the massive amount of brake fade I (and Grim Reaper, who nearly lived up to his name!) experienced at last years Castle Combe social.

This thread will be updated as things progress and eventually are finished and as I've not made great inroads until now, that's why I've not posted anything.

Until now!

Pending the purchase of a new pair of hubs/bearings and housings (knuckles), all the other parts are now in place.

The calipers were secured in early December last year:

DSCF0627.jpg


As you can see, they needed some TLC and so a complete strip and rebuild went ahead over the Xmas period, which showed that the pistons were shot and the other mild steel fittings were past their best too.

So, I sourced some stainless bleed nipples and braided brake lines with stainless fittings (Hel if you're interested, not Goodridge) and whist stripped, I had the calipers and carriers blasted and powder coated.

Finding new pistons was impossible and I asked a workmate if he could turn me a pair, as he was an experienced metal worker. He couldn't get stainless bar in suffucuently large diameter, but used his links at Ferranti to secure some weapons-grade titanium!

However, it wasn't all plain sailing and he just couldn't turn the stuff with his tool steel bits. So, I asked our very own A2sumo for advice, as I knew he worked with metal in the aerospace industry. He did one better than this and actually fabricated a new pair of pistons, again from titanium and to say they are a work of art is an understatement:

DSC_1270.jpg


DSC_1273.jpg


DSC_1274.jpg


As you can see, the old pistons were past their sell by date, with massive corrosion around the exposed top section and even starting to go at the base.

The new ones will not suffer this, as titanium is far more inert and less prone to rotting than steel, even stainless. It also has a lower expansion coefficient, so will be more stable at high temperatures. It is a lot lighter than steel and also about twice as hard, so the perfect material for pistons.

Here you can see one installed in the newly coated and refurbished caliper, together with the cleaned rubber.

DSC_1281.jpg


And finally for now, a photo of the assembled, refurbed calipers, carriers and pistons:

DSC_1277.jpg


That's all for now. The next step is to get the housings and hubs/bearings bought and then the swap over can commence.

As I will have a pair of nearly new discs and pads, calipers and housings and bearings all in good condition after the operation, if anyone wants them, please PM for prices.

Cheers,

Mike
 
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Excellent workmanship as always Mike - you're a true craftsman.

There will be no stopping you at Castle Combe this year or should that be there will now... :p

As for the final mod... that'll be the day!!

Nice to see that you are keeping busy mate - hope life is treating you and Ange very well indeed despite recent events.

Darren
 
Will certainly make interesting reading Mike!

Can you shrink the pics as they're HUGE and introduce large horizontal scrollbars in my browser! ;)
 
wow, they look amazing in comparison to the before photo.

Hat off to you for your patience and persistance and credit where credit is due. Hope you manage to source the rest of the parts needed in time for the next installment at Castle Coombe so that we can witness Tank in action after this upgrade. :D ;)
 
Sorry chaps, been fiddling with photos whilst the post was up, but can't get a clickable thumbnail in there.

They're more reasonable now Ian, but I can shrink further if you like.

Darren, Carl is still the one to beat (new Stig anyone?) and Humps has now shown a Banzai attitude that beggars belief (and mows grass too!).

I may not be the fastest out of a corner, but I sure as heck will be the latest braker into them!

Cheers

Mike
 
Mike - just wondered why you went for a stock Audi TT 2-piston floating caliper and not an after-market Brembo/AP (or Audi branded Brembo) 4/6 pot fixed caliper which would offer additional clamping forces/ better braking potential?

What pads will you use?

Again, are you using stock TT 312mm rotors, or an after-market application? Please don't be tempted to cross-drill - I have made many a rant about that particular non-upgrade!
 
I have used the simplest and cheapest upgrade possible Dan and even that is going to cost in the region of £600, once the bearings and housings are replaced!

True, a larger caliper with more pistons would give better clamping forces, especially if they are opposed, but in the case of such a light car like the A2, that would be overkill.

Also, having had lots of experience of motorcycle 4 piston calipers, I know from experience just how easily they can sieze and how tricky they are to clean and re-condition.

I'll be using a Mintex setup, exactly as per the ones on Tank now, but 312mm as opposed to 256mm. I don't intend going down the drilling or grooved rotor path and to be honest, I think that just the increase of 56mm diameter will have a dramatic enough effect.

Cheers,

mike
 
Oh I wouldn't say overkill, Lotus did an AP-based multi-pot caliper for the Elise and that's 250kg lighter than the A2 (ok I know that's comparing apples and pears, it's a much faster car, but still...).

I agree though, with a 56mm increase in rotor diameter you'll see a significant increase in stopping force anyway, even if you kept the clamping force and pads the same. Are the new discs thicker too - that's also an area where you get better braking (and cooling if they're well-ventilated internally).

What will be the overall increase in un-sprung weight - always an important consideration.

Can you get the Ferodo DS2500 pad in your caliper fitment - they are the best pad I have ever used (and I've been through a few on my various brake upgrades in the past).
 
Oh I wouldn't say overkill, Lotus did an AP-based multi-pot caliper for the Elise and that's 250kg lighter than the A2 (ok I know that's comparing apples and pears, it's a much faster car, but still...).

I agree though, with a 56mm increase in rotor diameter you'll see a significant increase in stopping force anyway, even if you kept the clamping force and pads the same. Are the new discs thicker too - that's also an area where you get better braking (and cooling if they're well-ventilated internally).

What will be the overall increase in un-sprung weight - always an important consideration.

Can you get the Ferodo DS2500 pad in your caliper fitment - they are the best pad I have ever used (and I've been through a few on my various brake upgrades in the past).

I'll be able to judge the unsprung weight issue when I've done the swap - I'm taking notes as I go and will only be able to weigh the old parts when they're off the car.

As to the DS2500 pads, we've had this discussion before. I agree, all the reviews by owners say they are a superb pad, but I can't justify £130 for a pair!

I'll stick with Mintex for the time being, that way, I can compare like with like, the only difference being the increased size.

The new discs are a couple of mm thicker and are internally ventilated, as per the A2 discs, so heat build bup shouldbn't be an issue.

Cheers,

Mike
 
Cool, keep us all updated anyway!

I paid £180 for my DS2500s on my S2 - they were worth every penny in my mind as at least they worked, unlike the EBC Reds I had on there previous which actually cracked and sheared off the backing plate during a track day :eek:

Superb pads but yes they are pricey.
 
I think that just the increase of 56mm diameter will have a dramatic enough effect.
"dramatic", maybe not, but the effect will be very noticeable.
On my previous MGF I had upgraded the front discs from 240mm (!) to 280mm using the same calipers (with a spacer, then), and the improvement was immediate, although not as huge as with the later optionnal factory brake setup (304mm discs + AP 4 pots).

Something to take into account is the front-rear brake bias.
That bias is determined and set for the standard system and if you upgrade only one end, the braking power ratio doesn't match anymore the brake bias.
BUT I would only worry IF a significant REAR brakes upgrade were carried out (and no front upgrade), because that could lead to rear wheels blocking, what is very dangerous when not wanted.
I wouldn't worry at all for an increase of front braking power on a front engined & wheel drive car.

The "ultimate" brakes upgrade I have seen is the Golf R32 system on the 1.8T engined A2 belonging to that German chap :)
 
hi mike sure is looking good,glad you are pleased with the pistons-even more exclusivity. i have a question to dan b why not cross drilled? keep up the hard work and see you soon mikee
 
Cross-drilling - ok several reasons why not on a modern road car

1. it doesn't improve stopping distances
2. it doesn't increase cooling significantly
3. it introduces additional areas of stress into the disc, increasing chances cracking
4. it causes increased wear to the pads

X-drilling was introduced to racing cars in the 50/60s when pads were made of organic material and they produced significant quantities of gas when the pads heated up which actually prevented proper pad/disc contact - x-drilling was a means to allow the gas to escape. Modern pads produce no gas, so this is not an issue anymore.

X-drilling does not really improve ventilation and aid cooling either - you do not get significant cross-flow of air through the disc faces. In fact it can make the disc retain heat more - the face of the disc is now in effect smaller, so has a poorer surface from which to radiate away excess heat.

Lastly, a lot of x-drilled discs are just that - drilled - which introduces a lot of stress points leading to cracking and premature disc failure. Discs that have cast holes in them are better in this respect, but this is hugely more expensive.

I have a relative who works at Jaguar on air flow - brakes and cooling. They've done countless engineering tests on brake design and time and again they recommend not using x-drilled discs on their "sport models" as they have no effect on stopping distances, but x-drilled discs still appear on them -why? Showroom effect - the marketing boys put them on because they look more "sporty".

Slotting your discs is another arguement altogether - pads "glaze" with hard use (especially on track days) and slots can be beneficial here as the leading edge of the slot effectively "scrapes clean" away the glaze level. Again though, slots will lead to much more rapid pad and disc wear, and can also introduce lots of noise and vibrations under braking.
 
Don't worry Mike - yours are dimpled, not drilled. Interestingly though, virtually all performance motorcycles have drilled discs, for even heat dissipation more than anything else.

Cheers

Mike
 
well thanks for the info Dan b interesting reading. i have been a precision engineer for 24 years. over the first 11 years had some dealings with motor sport development and in that time drilled more disc's than i care to remember.(now aerospace/ f1)the only problems i am aware of in drilling disc's is related to vented disc's,in as much that the holes must enter the ventilation "vents" and not go through the walls of the vents. this allows cooling air/gasses to breath easily through the vents that lead from the center of the disk to the outer edge, without causing uneven stresses in the disk. as for causing points for cracks to appear i have to disagree ---- a proven repair for cracks is to drill a small hole at the end of the crack-thus stopping it spreading any further.
in a local car spares shop they have a large ventilated disk on show that the owner has obviously had his moneys worth out of as one side of the disk has completely worn away down to the vents! he hadn't noticed any problems apart from a slightly odd noise when he braked. it is very surprising the abuse a disk is capable of surviving. now whilst at college we were shown a test bed where they tested brake pad/disks. basically a great big motor that turned the disk with a conventional caliper attached. i have seen the test done until destruction of the disk. basically the braking force is applied constantly until it starts to glow----then it starts to spark and glow even brighter----then the disk starts to distort caused by expansion of the cast iron and the pads slowing the disk rotor down to a slower rpm than the hub---then a big bang and no more disk.

now please don't feel i am arguing with you as i am not and still interested in yours and your friends knowledge. and mike my ones are drilled through and grooved.no problems with fitting them-;) thanks.
 
mike my ones are drilled through and grooved.no problems with fitting them-;) thanks.

Oh, I though they were dimpled (or have you drilled them?;))

As to wearing down to the vents, I knew a courier once who would just replace pads until the discs gave him his 'ABS warning'! That was his way of saying they started to grip and not-grip in rapid succession as the vent fins were coming through the disc surface!

Cheers,

Mike
 
hi mike no i havent drilled them. dimpling is much easier to produce as you dont need to match them up to the vent slots as described in my last book(see above) and they are in my opinion just for show---oh no i'm off again:D
 
audi 1.8t brakes

hi guys just wondering if the A3 1.8t brakes caliper would work on the A2. ive got a full set front and rear. it looks the same as the tt.
 
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