Rear Disc Brakes

[literarymadness]

Europa TC Thanks for posting that!!! I screenshot the Consumer Reports Chart from that link. Those numbers reiterate my concerns with "How good are the driver in front of me's  brakes?

[Pfreen]

I wonder how much the improvement is due to anti-lock braking.  I suspect a lot.

[TurboFource]

Wow!

[GavinT]

You can't just bolt on the larger rotor (GT6) to the europa, its all larger bits.....bearings, etc.  IIRC that is.  [...]

That's what I recall, too.
Have you offered up a GT6 disc to a Europa hub? Some one must have done it.

I took my infrared temp gun to a track day at PIR and measured 320F front and 300F rear after a 15 minute session. [...]

Those are pretty low temps for a track event, aren't they?

[GavinT]

[...] If Lotus in 1995 had felt the 1972 Twin Cam Special brake set-up was a better setup, the 1650 lb Elise (same weight as Fed-spec TCS) would have had that setup.

Well, Lotus produced the Elite (Type 14) in 1957 and the Elan in 1962, both of which had four wheel discs.
Sometimes it not 'what's better' that makes it through to the final product.

I am not a trained driver nor do I race. But I do drive for long periods of time at fairly high speeds in semi-dense traffic, where other drivers occasionally do really stupid maneuvers usually at night (Hey it's South Florida).  In a panic stop, a few feet can make a huge difference and not the time to find out how I should have braked. I'll take any advantage I can get.

Me either. I'd be a play racer at best.
Back in the early days, a group of us attended what was then known as an 'advanced driving course' conducted by a quite successful local racer. These courses were aimed at drivers needing to qualify for a race licence from an accredited organisation. There was an assessment as part of the course.

Apart from the more intuitive stuff like regulations, theory, cornering lines & apexes etc., the most helpful practical exercise by far was learning brake control.

The setup they used was simple. They hosed down the car park, and placed cones which represented the back of a stationary vehicle. As you drove by at a constant 60kph (35mph), the instructor would clap his hands and you'd hit the brakes and hopefully not hit the cones.
Later variations included a scenario where you'd need to swerve into the next lane and stop behind an imaginary vehicle placed one car length further forward. Needless to say, just slamming on the brakes doesn't really work.
I reckon brake control is something we can't readily practice on our own. Probably the best money I ever spent, so highly recommended.

If there's nothing like this in South Florida, perhaps this is a business opportunity ripe for the picking. 

[EuropaTC]

I wonder how much the improvement is due to anti-lock braking.  I suspect a lot.

For the average, non-enthusiast driver, your typical mom taking kids to school, flooded roads, etc, I suspect it's a life saver. But I think the main advance is that virtually every car has a brake servo to reduce effort & thus can use higher pressures/clamping forces and harder pads more resistant to fade. Plus the trend for bigger wheels which allows bigger discs with more leverage, that makes a big difference to the maths.

On the topic of driver skill regarding braking, there was a DVD produced in the early days of the Elise by Andy Walsh called "Bending the Rules". He covers braking and shows how you could drastically reduce the stopping distance of the Elise, (no servo, no abs) with your style of cadence braking and what he terms as "threshold braking". (basically something very similar but clearly more effective)

I've taken a screenshot which is a bit blurry (old TV format) but does show the results in terms of car lengths stopping distances.  Well worth a view if you can find it on Amazon, etc.

Brian

[Chuck Nukem]

In the interest of science I may sacrifice some tires to the gods of brake testing once my discs are in...

[buzzer]

Got that dvd. Did some driver training with Andy Walsh a few years ago in my Westfield. Made me realise the skill a good driver has in the whole feel of the car including braking. He got in my Westfield and first time did a perfect high speed stop. I couldn’t get anywhere near 

[jbcollier]

Braking on cars with light front ends is an interesting problem.  This is the same with EVERY rear and mid engined car out there, not just Europas.  If you mash the brakes hard, the fronts lock and you slide with no steering control.  A locked sliding wheel does not slow you down anywhere nearly as quickly as a wheel held close to the point of locking but not quite locking (threshold braking).  You might think increasing the rear brake force is therefore the answer.  Not really, weight transfers to the front under braking.  Just increasing the rear brake force may lead to the rear brakes locking first as this weight transfer occurs.  As any fan of 70s cop shows can tell you, this leads to loss of control due to the rear of the car slewing around.

The key to safe short stops is squeezing the brakes to the threshold braking point.  Squeezing allows time for the weight transfer to occur.  Once the weight has transferred to the front, you can apply a lot of force before the brakes will lock.

This same issue arises with motorcycles and bicycles.  Nail the front brake hard and the front locks every time.  Squeeze, get the weight transferred, and stopping distances can be very short.

Yes, today's vehicles have phenomenal brakes, but that's not the reason modern cars stop so quickly.  Your average driver would simply lock the wheels and slide out of control with just giving them "better" brakes.  The difference is ABS.  Now your average idiot driver can still know nothing and stop within fractions of foot as quickly as the best race drivers.  Worse, the wee b@st@rds, who can't normally find their way out of a bathroom if you spin them round twice, somehow "know" their brakes are good and follow so #$%& close there is zero (or less) margin for error.

What can we do?  Same as old school racers, motorcyclists and cyclists.  We have to practise threshold braking until it becomes instinctive.  Not once and pat yourself on the back.  Practise repeatedly until you're good and then maintain weekly brush-ups so you do it automatically.  Also:

- leave a little more room in front of you than you do in your modern car.  That extra room is for the idiot behind you so you have the space to brake a little less hard and give the be-hinders more time to not do the wrong thing.

- look ahead!  If you can anticipate things, you can react slower and improve your chances of getting out unscathed.

Brake improvements are useless, and probably counter-productive, without practising threshold braking and being more aware of your driving environment.

If you want to improve your brakes, great!  Nothing wrong with that.  Make sure you improve the whole brake system in a balanced way, not just one end and not the other.  Then practise threshold braking as you will still get into trouble no matter how good your brakes are unless you practise!

[Clifton]

If you want to improve your brakes, great!  Nothing wrong with that.  Make sure you improve the whole brake system in a balanced way, not just one end and not the other.  Then practise threshold braking as you will still get into trouble no matter how good your brakes are unless you practise!

Great advise. I mash the brakes in every new car I drive to find what I can get away with and find where they lock or don't and to get the feel.

[Kendo]

I just tried looking for bending the rules by andrew walsh. Found one in the UK. But Amazon.UK wouldn't ship it to California. It's probably the wrong DVD zone anyway. One in Canada was ~$130. Seemed a bit pricy.

Does anyone know where I can get a copy in the USA?

[literarymadness]

My main issue was never with the rear drums and dry weather braking. But more with wet weather braking in South Florida. Anyone in Florida will tell you that it go from clear blue skies to torrential downpours in a very short time.  We are in the Sub-tropic Zone.  When I said I had no training, I didn't mean I wasn't experienced. I have done heavy driving in 40+ states from the North to South, the East Coast to West Coast in all four seasons of weather and every type of terrain. I have pretty much driven in every country in Central and South America, from jungle roads in Colombia to mountain roads in the Andes of Ecuador and Chile. You can include some of Europe and a little in Japan. There are just certain things that you can't practice for.

The straw proverbial straw that broke the camel's back in wanting rear disc brakes happened a few months ago. I was driving back in my TCS from the other side of Florida on I-75 when I caught in a heavy rain storm with very poor visibility (100 ft at best). People in their big SUVs and pickup trucks somehow feel that it is still safe to drive fast in heavy rain. By the time I could see all the tail lights of twenty or so cars completely stopped on the interstate due to an accident, I had no choice other than to panic stop. My rear drums were no doubt water soaked-and completely useless at this point. My front brakes locked and the tail of my car was not behaving very well at all weaving in and out of the lane. The car hydroplaned for about 20 feet but somehow managed to stop about a foot or so from the next vehicle. 

Had I not been going much slower prior than the other vehicles and keeping my distance, the ending would have been a little different. On the rest of the drive home, I made the decision to put disc brakes in the rear. The decision to get the new front kits came after speaking to Richard at Banks who told me the front and rear kits worked with each other very well and were time tested on the track for balance.

[EuropaTC]

^^  that's all too true. No matter how good we are, how far we look ahead or how often we practice, there will always be an element of human error when we react to an emergency.

I accept this is a personal hobby horse but anything that reduces my margin for error in modern day traffic is a good thing IMO. Increasing the rear braking effort will reduce my margin for driver error in locking up the front if only because it starts weight transfer earlier. The trick is not to get too much rear brake of course, we want them improved but not to the point of locking up first.

Using the same spreadsheet maths for the Elise S1 as the Europa, it works out that they decided 41% @ 1G was a good number for the rear brakes, which on that car has them locking up fractionally after the front at 1G. The S1 weighs around the same as the TC Europa but uses the 282mm (yes, 282) diameter discs F & R balanced by caliper piston diameter. 

In comparison the Europa rear drum is around 23-25% which means the fronts can lock around 0.7-0.8G and when everyone else is 0.9G or better, we have a problem. It might feel like we're stopping quickly but the reality is that we're not as good as that shopping trolley driven by someone who only uses the mirror to put makeup on. (apologies for the MCP analogy    ). 

But that's what we're up against in modern traffic.

Brian

[GavinT]

I hear ya, Literary.
I also live in a sub-tropical region and sometimes those downpours can be pretty intense.
I've been in lines of traffic where half the cars simply pull over and wait. Usually the really heavy part of the downpour only lasts a minute or two.

But also, the number of SUV's has increased markedly over the years . . and I suspect the sheer size of them is bigger in the US than here. The Toyota Hilux was announced as the outright best selling vehicle in Oz - for the last four years straight - crazy.

So, probably the danger has increased for little cars.
The eye level for the average Europa driver is probably three feet off the deck. By comparison, the big SUV's / trucks have a commanding view from perhaps six feet.
Add to that the 'confidence inspiring' ABS brakes means they probably aren't even looking for us, let alone seeing us.

[GavinT]

In the interest of science I may sacrifice some tires to the gods of brake testing once my discs are in...

I'd be really interested if you do that.
While I think it's no surprise that pretty much everyone is satisfied with their rear disc conversion, I don't recall any actual tests.
G-meters are cheap enough and you can even get free G-meter apps for a phone.

I accept this is a personal hobby horse but anything that reduces my margin for error in modern day traffic is a good thing IMO. Increasing the rear braking effort will reduce my margin for driver error in locking up the front if only because it starts weight transfer earlier. The trick is not to get too much rear brake of course, we want them improved but not to the point of locking up first.

Using the same spreadsheet maths for the Elise S1 as the Europa, it works out that they decided 41% @ 1G was a good number for the rear brakes, which on that car has them locking up fractionally after the front at 1G. The S1 weighs around the same as the TC Europa but uses the 282mm (yes, 282) diameter discs F & R balanced by caliper piston diameter. 

In comparison the Europa rear drum is around 23-25% which means the fronts can lock around 0.7-0.8G and when everyone else is 0.9G or better, we have a problem. It might feel like we're stopping quickly but the reality is that we're not as good as that shopping trolley driven by someone who only uses the mirror to put makeup on. (apologies for the MCP analogy    ).

It's all a bit of a conundrum in some ways.

Presumably we agree the ability to lock the front brakes indicates they're satisfactory*. Basically this is because they've overcome the limitation of tyre traction.
If the rear conversions work well, do we know how well? . . . or how far they are from locking?

If I recall, the spreadsheet for the Europa suggests that a stock front disc is best paired with a 34mm rear calliper.
I've been tempted to go for a 36mm calliper and use an adjustable proportioning valve to trim the rears. One other advantage of this is that one could open the valve further for a wet track.

* with caveats of course.


https://race.parts/Catalogue/Braking/Proportioning-Valves/AP-Proportioning-Valves/AP-Racing-Lever-Type-Single-Bore-Proportioning-Valve