31 replies to this topic

[red300zx99]

Just wondered if they are allowed to change brakes during the course of the race, and if they do does it ever happen?

[Chevy II Nova]

During the race? I suppose they could if they desired to but the car would never be classified after that much time in the pits.

[Keith Young]

Are you proposing they find a way to change wheel assemblies rather than tires, or just asking if this is allowed?

[red300zx99]

Yep, doesn't seem to hard of a challenge to engineer

[McGuire]

Originally posted by rough_wood
Are you proposing they find a way to change wheel assemblies rather than tires, or just asking if this is allowed?

Sorry, you've totally lost me. On pit stops the mounted tire and wheel are swapped as an assembly. By "wheel assembly" do you mean also the hub, bearings, brake rotor and caliper as well?

I can visualize how this could possibly be done, though I don't see any particular advantage, and I do see a few problems. The main thing that comes to mind is the brake hydraulic circuit would then require bleeding.

[Greg Locock]

I'm guessing this is asked by an Ozzie, our V8 Supercars have a compulsory brake pad change (boo) on our best circuit.

No bleeding required, just some long handled pliers, and a bit of clever design.

[McGuire]

Originally posted by Greg Locock
I'm guessing this is asked by an Ozzie, our V8 Supercars have a compulsory brake pad change (boo) on our best circuit.

No bleeding required, just some long handled pliers, and a bit of clever design.

Sure, pads (and rotors) are often changed in endurance racing as well. I am trying to visualize how the entire rotating assembly could be changed without disturbing the hydrualic system...can't see how it's possible.

[Greg Locock]

Unbolt the calliper from the strut, hook it out the way.

I've known mechanics to weld up half-pipe into the jaws of Vise grips so they can clamp the hoses and obviate the need for a bleed op, as well. I close my eyes to this sort of thing.

[McGuire]

Originally posted by Greg Locock
Unbolt the calliper from the strut, hook it out the way.

I've known mechanics to weld up half-pipe into the jaws of Vise grips so they can clamp the hoses and obviate the need for a bleed op, as well. I close my eyes to this sort of thing.

LOL you are simply describing typical brake repairs in the field, and also essentially how it's done in endurance racing, which would hardly be fast enough for an F1-style pitstop. There is no clearance to remove the caliper from the rotor unless the wheel is removed first. Then to replace the rotor you need to a) remove the caliper first and b) make the rotor/hat assembly a slip fit on the hub. That is several steps, not the one step envisioned here. Again, I see no way to replace the entire assembly as a unit in the course of a tire change, which I believe was rough_wood's question.

[dancin stu]

Originally posted by McGuire


Sure, pads (and rotors) are often changed in endurance racing as well. I am trying to visualize how the entire rotating assembly could be changed without disturbing the hydrualic system...can't see how it's possible.

It is possible to buy no loss connectors for hydraulic lines. Bike racers use them, so that they can change front wheels, and the old ITC cars use to use no loss connectors on all of their hydraulics - this is how they managed to change engines in 8 minutes or so....

I would have thought also that this is how Audi, amongst others are able to change their gearbox assemblies so easily

[red300zx99]

I've seen quick disconnect brake line hoses that claim rebleeding afterwards isn't nessecary. The advantages of having such a system are nice such as the option to run without a cooling scoop, and lighter weight materials as the lifetime expectance would decrease.

[McGuire]

Hmmm... so if we can key or peg the caliper to the upright so it absolutely cannot flex whlie still making it removable without threaded fasteners (perhaps by making the caliper mount concentric with the spindle)...and fix the hub bearing preload...then we can change out the the entire rotating assembly and brakes at the center nut. I still don't think there's any particular advantage in F1, but the concept could be useful in endurance racing...if it's not already illegal.

....this sort of reminds me of the Bugatti T35 and a few others: the brake drum and wheel were cast as one.

[dosco]

Originally posted by McGuire
Hmmm... so if we can key or peg the caliper to the upright so it absolutely cannot flex whlie still making it removable without threaded fasteners (perhaps by making the caliper mount concentric with the spindle)...and fix the hub bearing preload...then we can change out the the entire rotating assembly and brakes at the center nut. I still don't think there's any particular advantage in F1, but the concept could be useful in endurance racing...if it's not already illegal.

....this sort of reminds me of the Bugatti T35 and a few others: the brake drum and wheel were cast as one.

To make the caliper quickly removable, use pins to locate it (and also to react the brake load to the suspension), and perhaps 1 bolt to hold it in place.

Another possible solution would be spring loaded quick-disconnect pins.

Piece of cake.

The problem, IMO, is making the system redundant enough to ensure the pins remain in place under vibrational loads......

[Yelnats]

Designing fast change brake assemblies is an interesting technical challenge but redundant in a sport that deliberatly sacrifices brake durability for a few percent gains in downforce. Using the correct sized brake cooling intakes insures reliable brakes and there will always be misjudgements due to changing conditions and just plain screwups. I don't see the need for fast change assemblies unless this can be done with no time, weight or reliability penalties which is unlikely and probably would be banned by the FIA as soon as it is achieved.

[cozworth]

I remember seeing some component in the braking system being changed during the BATHRUST
1000 race. AFAIK it must be the brake pads?

[McGuire]

Originally posted by dosco


To make the caliper quickly removable, use pins to locate it (and also to react the brake load to the suspension), and perhaps 1 bolt to hold it in place.

Another possible solution would be spring loaded quick-disconnect pins.

Piece of cake.

The problem, IMO, is making the system redundant enough to ensure the pins remain in place under vibrational loads......

To me the better solution would be to make the caliper mount or bracket concentric with the hub carrier, with a large key or splines to prevent rotation. Wheel/tire, rotor, bearings and caliper come off as an assembly when the outer center lock nut is removed. With your system multiple steps would be required, if I am visualizing it correctly.

[McGuire]

Originally posted by Yelnats
Designing fast change brake assemblies is an interesting technical challenge but redundant in a sport that deliberatly sacrifices brake durability for a few percent gains in downforce. Using the correct sized brake cooling intakes insures reliable brakes and there will always be misjudgements due to changing conditions and just plain screwups. I don't see the need for fast change assemblies unless this can be done with no time, weight or reliability penalties which is unlikely and probably would be banned by the FIA as soon as it is achieved.

That's how I see it as well -- no purpose to it F1 and it would quickly be banned in sports cars.

[McGuire]

Originally posted by cozworth
I remember seeing some component in the braking system being changed during the BATHRUST
1000 race. AFAIK it must be the brake pads?

Quite so. Pad and rotor replacements are common in long distance racing.

[dosco]

Originally posted by McGuire


To me the better solution would be to make the caliper mount or bracket concentric with the hub carrier, with a large key or splines to prevent rotation. Wheel/tire, rotor, bearings and caliper come off as an assembly when the outer center lock nut is removed. With your system multiple steps would be required, if I am visualizing it correctly.

Excellent idea.

My thought was 1 fastener, and then just slide the caliper off (or remove the fastener, slide the pins out and then remove the caliper).

Cool.

Yes, it would be banned......I could see it now - Ross Brawns' strategy to reduce weight by making the pads and discs thinner....factor it into the pit stop strategy.....ugh.

[Keith Young]

I wonder how much time it would add to the stop. You could have thinner parts and less ducting so there is an obviouse advantage. Currently stops take 7 seconds for good stops, but the tires are changed in 4. Do you guys think you could make a system that would work and could be changed in 10 seconds by a trained crew?

[Dmitriy_Guller]

Originally posted by rough_wood
I wonder how much time it would add to the stop. You could have thinner parts and less ducting so there is an obviouse advantage. Currently stops take 7 seconds for good stops, but the tires are changed in 4. Do you guys think you could make a system that would work and could be changed in 10 seconds by a trained crew?

It looks like this idea needs a couple of wheel detachments at top speed during braking to perfect. I don't think Luca Badoer would be thrilled to see his test shunt rate doubled.

[dosco]

Originally posted by rough_wood
I wonder how much time it would add to the stop. You could have thinner parts and less ducting so there is an obviouse advantage. Currently stops take 7 seconds for good stops, but the tires are changed in 4. Do you guys think you could make a system that would work and could be changed in 10 seconds by a trained crew?

Yup....reduce the unsprung mass too (maybe....reduction in disc/pads might be taken up by the "quick release" system)......could be quite a few benefits of such a system....

[Scoots]

Originally posted by dosco


Yup....reduce the unsprung mass too (maybe....reduction in disc/pads might be taken up by the "quick release" system)......could be quite a few benefits of such a system....

Reduce the ducting to zero and make the aero much cleaner over the front wing ... less rotational mass, less unsprung weight, smaller radiators because the air will be cooler and cleaner, cleaner air around the rear wing too. No reason, if done correctly that it would make the pitstops anylonger than they are now.

[Wuzak]

Originally posted by cozworth
I remember seeing some component in the braking system being changed during the BATHRUST
1000 race. AFAIK it must be the brake pads?

Yes, a brake pad change is compulsory in the Bathurst 1000.

[Patrice L'Rodent]

I am sure the big Ford GT40s, Mk 2s and Mk 4s changed the entire wheel and brake assembly at pit stops during the Le Mans 24 hour race. IIRC, they had dry break connections on the brake lines.
Stopping two ton cars from 220mph has a price.
Changing pads at Bathurst and other Aussie Taxicab races (I refuse to call them "V8 Supercars") is just a gimmick to spice up the racing. Many fast teams have shown it possible to do the entire 1000km without a pad change.
PDR

[RDV]

At Lemans we regularily change the entire brake disc rotor/caliper/pad assembly.
No bleeding is necessary as all lines with dry-break couplings.

This enables a- the use of monobloc calipers with solid bridges for extra stiffness, as does not need clearance to extract pads and b-piston seal degradation not a problem as you are fitting a fresh caliper full of fresh fluid. Fluid degradation due to high piston temperatures is thus corrected.

The concept of running without brake ducting in F1 not achievable, just consider power dissipation requirement if they accelerate at 1.3 G with 900hp, they will need 3 times the energy to brake at 4g.... if you disregard aero drag. Water cooled calipers are extensively used in GT amd sports cars, butr mainly to keep calipers at a reasonable temperature, and because of mass involved , they are all in the 900 to 1300 kg range, and obey the formula mv^2

[Keith Young]

RDV: care to discuss this WE is that you mention?

[RDV]

...mmm, ever heard of non-disclosure clauses in contracts?

[Keith Young]

unfortunately yes, does this also apply to years of the past technology you saw first hand?

[turby]

Hi RDV,

very interesting to get these infos first hand.

Please allow just one small remark: the energy required to accelerate a car with 1.3g (from speed a to speed b) is the same for braking the car at 4g (from speed b to speed a). It's the power, which is in this case a factor of 3 higher at braking than for acceleration.

[RDV]

turby

Please allow just one small remark: the energy required to accelerate a car with 1.3g (from speed a to speed b) is the same for braking the car at 4g (from speed b to speed a). It's the power, which is in this case a factor of 3 higher at braking than for acceleration.

Absolutely correct, my sloppy writing..... its what I complain all the time about other people.... hoist by my own petard...

rough_wood-unfortunately yes, does this also apply to years of the past technology you saw first hand?

..not if I keep it general and dont quote names.... but as at Lemans in a couple of weeks prefer not to expand....

[ferrarifan2000]

lemme guess, team goh.

bg