Long braking? Taycan Turbo (no PCCB)

[PorscheCH]

Until now, I had never had the opportunity to test the Taycan at high speed. Today I did several stretches of highway (maybe 15-20 km in total) between 200 and 250 km/h on an almost empty highway (in DE). 4 adult passengers. 5-6 degrees outside. asphalt in excellent condition but wet (no puddles).

I have a 20" aero wheel kit with new Pirelli P Zero Winter tires, 285/40 rear, 245/45 front. Speed index 240 km/h.

Fun but several times I had the unpleasant feeling of long braking when trying to reduce speed quickly. Not sensational. I had plenty of distance from cars ahead, so no problem. But I'm concerned about potential panic stops (maybe due to other cars maneuvering).

tried with both regen on and off. can't feel much difference.

At lower or city speeds the brakes/tires feel otherwise quite good and effective.

I've read a few posts here, also about the role of the tire. Could you give me your impressions of braking in winter conditions and at high speeds? Thanks!

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[wurzitup]

Until now, I had never had the opportunity to test the Taycan at high speed. Today I did several stretches of highway (maybe 15-20 km in total) between 200 and 250 km/h on an almost empty highway (in DE). 4 adult passengers. 5-6 degrees outside. asphalt in excellent condition but wet (no puddles).

I have a 20" aero wheel kit with new Pirelli P Zero Winter tires, 285/40 rear, 245/45 front. Speed index 240 km/h.

Fun but several times I had the unpleasant feeling of long braking when trying to reduce speed quickly. Not sensational. I had plenty of distance from cars ahead, so no problem. But I'm concerned about potential panic stops (maybe due to other cars maneuvering).

tried with both regen on and off. can't feel much difference.

At lower or city speeds the brakes/tires feel otherwise quite good and effective.

I've read a few posts here, also about the role of the tire. Could you give me your impressions of braking in winter conditions and at high speeds? Thanks!

There was a YouTube video of Out of Spec driving where he was driving a 4S on the Autobahn at upwards of 225kph, and remarked how long the braking distances were. With PCCBs. And that this was simply a function of a 5000lb. car at such high speed. Just takes some familiarity and recalibration due to the mass of the car.

Very cool vid- check out at 11:00 min mark.

 

[daveo4EV]

it's a big heavy car - you have a lot of inertia when at speed - braking distance is dictated by the tires and the level of grip - all seasons will have longer braking distances than summer tires - what you may have experienced could be normal - without any actual data there is very little to discuss.

PCCB's do not improve braking distance - all porsche brakes are tested to provide no brake fade after 25 successive trials from 80% of top speed - with NO brake fade - if your brakes are not fading (which for one or two trials would not be the case) - the stopping distance you experience is a result of tire grip and road adhesion characteristics.

5,100 lbs takes a long time to stop - physics - street tires have a maximum grip threshold of about 1.2 g's under ABS threshold braking conditions - slicks and high grip tires are 2.5 g's or higher - I'm pretty sure the math of 1.2 g's of maximum forward threshold braking vs. 5,100 lbs at 250 kph would equal stopping distances that you experienced and would surprise most people.

 

[daveo4EV]

PCCB's do not improve stopping distance in any meaningful statistically significant fashion - they are in fact un-necessary on the Taycan - since the Taycan lacks the stamina and battery power capacity to drive the car hard enough to thermally overwhelm the excellent Porsche steel brakes - if I order a future Taycan I will not be specifying PCCB"s since they are un-necessary.

PCCB"s are "better" in the following ways:

• lighter rotational mass
• no brake dust
• appearance and aesthetics
• greater thermal endurance under high demand applications under extended circumstances

tires and their grip level at ABS threshold braking normalize stopping distance since the vehicle can not decelerate any faster than ABS allows the tire to remain at maximum threshold grip for deceleration. Since both steel and PCCB brakes can achieve threshold/ABS braking (i.e. they have more grip than the tires and ABS keeps the tires from "locking") then stopping distance is dictated by tire grip level - not the brakes (unless they are overheated)

you will "run out" of the following capacities with a Taycan _BEFORE_ you can overheat the steel brakes:

• battery thermals - at 132F the battery will throttle maximum power (15 min of full capacity driving)
• actual battery power - high performance driving drains he battery - and the Taycan can't run for much more than 30 minutes at full pace
• street tire grip - the car is soo heavy I've found on track the tires get greasy after about 5 laps reducing maximum grip levels such that braking distances elongate

steel brake thermal saturation is way way way down the list vs. the physics of the issues listed above- and PCCB's are _ONLY_ better once you would have reached thermal saturation of steel brakes, you would expect PCCB's to perform better once steel brakes are thermally saturated - which for Porsche steel brakes actually takes quite a bit and IMHO exceeds other characteristics of the Taycan.

 

[daveo4EV]

here is the data from my 2020 Turbo at Laguna Seca in nearly ideal conditions - threshold braking - factory all season tires - continental - 68F - sunny - smooth and grippy track surface - and brake conditions with full abs braking

1.13 g's is the "maximum" limit of tire adhesion - stopping distances were in fact "long" but expected and repeatable given the car's mass and speed - after 6 laps teh battery overheated to prevent longer duration sessions.

 

[daveo4EV]

I've read a few posts here, also about the role of the tire. Could you give me your impressions of braking in winter conditions and at high speeds? Thanks!

cold will also elongate braking distances - tires have less grip if they are cold & harder…

 

[PorscheCH]

Thanks for the *very* informative posts. I was referring to yours (in an earlier thread) and learnt a lot thanks to those about max g limit, tires and the substantial indifference between ceramic and non ceramic for most use cases.

I don‘t have any data point unfortunately (I was out with other people and could not pay attention to g forces etc. and I guess they are not stored anywhere for ex-post analysis). My vague comparison is with an Audi rs6 from a couple of years ago (non ceramic) which felt a bit readier to breake.

Still, I was a bit surprised at how much time it takes to break the car on winter tires and the feeling that there‘s no much bite on the pedal (if I can express it like that). It‘s not a big issue in a controllable environment, I am more worried about panic stops if another car does something stupid…

here is the data from my 2020 Turbo at Laguna Seca in nearly ideal conditions - threshold braking - factory all season tires - continental - 68F - sunny - smooth and grippy track surface - and brake conditions with full abs braking

1.13 g's is the "maximum" limit of tire adhesion - stopping distances were in fact "long" but expected and repeatable given the car's mass and speed - after 6 laps teh battery overheated to prevent longer duration sessions.

 

[daveo4EV]

Thanks for the *very* informative posts. I was referring to yours (in an earlier thread) and learnt a lot thanks to those about max g limit, tires and the substantial indifference between ceramic and non ceramic for most use cases.

I don‘t have any data point unfortunately (I was out with other people and could not pay attention to g forces etc. and I guess they are not stored anywhere for ex-post analysis). My vague comparison is with an Audi rs6 from a couple of years ago (non ceramic) which felt a bit readier to breake.

Still, I was a bit surprised at how much time it takes to break the car on winter tires and the feeling that there‘s no much bite on the pedal (if I can express it like that). It‘s not a big issue in a controllable environment, I am more worried about panic stops if another car does something stupid…

normal porsche steel brakes or PCSB’s (low dust) steel brakes?

PCSB’s have for years had the reputation for lacking initial “bite” under braking - Porsche’s “blended” braking where regen is first used and friction blended in only later also contributes to this feel - ultimately the tires will dictate stopping distance under threshold/panic conditions - but I agree the lack of “bite” from the pedal can be disconcerting - as I‘ve evolved in my understanding of braking from my track hobby - my following distances during street driving have elongated - cause street tires, street cars, and street brakes, and variable street conditions, are just so wimpy - the only solution is to always attempt to manage your following distance to avoid the need for optimal braking - I know this isn’t always possible, but it’s my personal goal while driving on the street.

brake pads and the compounds they are made out of have a lot to do with brake feel and swapping pads can improve various characteristics of braking - but always have a trades offs…more dust, worse low temp behavior, increased pad wear, increased rotor wear, etc…

porsche does an excellent job of balancing all the characteristics and options and ships a quality product in a quality configuration designed for minimal trade offs - and while their brakes are industry leading and perhaps the best brakes "off lot" you can buy - they are not perfect - I've personally never liked the "feel" of PCSB's - but on track while the feel was not to my liking the actual stopping distances were mostly on par with other brakes I've experienced…

 

[Mike in CA]

Car and Driver tested the braking of a 2020 Taycan 4S equipped with Pirelli P Zero PZ4 summer tires and PCCB's. The result:

70-0 MPH in 147 ft
100-0 MPH in 289 ft

By comparison, C&D's results for a 2021 BMW M3 Competition (on Michelin Pilot Sport 4), which weighs about 1300lbs less than the Taycan were:

70-0 MPH in 150 ft
100-0 MPH in 297 ft

Also, a 2020 Porsche 911 Carrera (on Pirelli P Zero PZ4) which weighs 1800 lbs less than the Taycan:

70-0 MPH 139 ft
100-0 MPH 277 ft

The point is that, even taking into account variations in test conditions, the Taycan's brakes (PCCB or otherwise as our forum mate @daveo4EV will remind us ) can hold their own despite the weight disadvantage, as the numbers above indicate.

The long stopping distances you experienced can certainly be attributed to narrower winter tires, cold temperatures and wet pavement. I'm going to assume you braked hard enough to engage ABS or were right at the edge of engagement. In either case, under the conditions you described, that ABS threshold would be a lot lower than it would be on dry pavement with wider performance rubber, and stopping distances would be quite a bit longer.

 

[f1eng]

Until now, I had never had the opportunity to test the Taycan at high speed. Today I did several stretches of highway (maybe 15-20 km in total) between 200 and 250 km/h on an almost empty highway (in DE). 4 adult passengers. 5-6 degrees outside. asphalt in excellent condition but wet (no puddles).

I have a 20" aero wheel kit with new Pirelli P Zero Winter tires, 285/40 rear, 245/45 front. Speed index 240 km/h.

Fun but several times I had the unpleasant feeling of long braking when trying to reduce speed quickly. Not sensational. I had plenty of distance from cars ahead, so no problem. But I'm concerned about potential panic stops (maybe due to other cars maneuvering).

tried with both regen on and off. can't feel much difference.

At lower or city speeds the brakes/tires feel otherwise quite good and effective.

I've read a few posts here, also about the role of the tire. Could you give me your impressions of braking in winter conditions and at high speeds? Thanks!

Were you feeling the ABS activating?

Winter tyres at 5 to 6 degrees are the best tyre for braking distance at that temperature.

The limit to braking will be tyre grip and if you weren't at the level where the ABS is kicking in you aren't on the limit.

If the car simply feels like it isn't slowing as much as you would like but you art not actually at the grip limit it is probably just that the car has less brake servo assistance than you are used to.

If you were on the grip limit you were going too fast for the road conditions

 

[PorscheCH]

thanks. I am not sure which brakes I have (definitely not the PCCB). here s a photo on 21" and summer tires. probably the standard ones?

normal porsche steel brakes or PCSB’s (low dust) steel brakes?

PCSB’s have for years had the reputation for lacking initial “bite” under braking - Porsche’s “blended” braking where regen is first used and friction blended in only later also contributes to this feel - ultimately the tires will dictate stopping distance under threshold/panic conditions - but I agree the lack of “bite” from the pedal can be disconcerting - as I‘ve evolved in my understanding of braking from my track hobby - my following distances during street driving have elongated - cause street tires, street cars, and street brakes, and variable street conditions, are just so wimpy - the only solution is to always attempt to manage your following distance to avoid the need for optimal braking - I know this isn’t always possible, but it’s my personal goal while driving on the street.

brake pads and the compounds they are made out of have a lot to do with brake feel and swapping pads can improve various characteristics of braking - but always have a trades offs…more dust, worse low temp behavior, increased pad wear, increased rotor wear, etc…

porsche does an excellent job of balancing all the characteristics and options and ships a quality product in a quality configuration designed for minimal trade offs - and while their brakes are industry leading and perhaps the best brakes "off lot" you can buy - they are not perfect - I've personally never liked the "feel" of PCSB's - but on track while the feel was not to my liking the actual stopping distances were mostly on par with other brakes I've experienced…

 

[PorscheCH]

I was definitely not at the grip limit no abs kicking in at any time) , I had 3 passengers, back from a day out, they just wanted to experience a bit of Porsche ev acceleration and speed. In the meantime I realised that those tires are labeled V for 240 km/h max I think.

Also, it was one of the first high speed run with the Taycan: in Switzerland, all forms of speeding are not only severely prosecuted, but are morally ranked among the worst crimes against humanity. It's really full of above average cars (lots of them). Everyone is going 40-80 km/h except for minor highway stretches at 100-120km/h (where tarmac is pristine). And everyone then takes it to more tolerant Germany or Italy ...

So I was not too aggressive even if the road was rather empty.

to be more accurate it was a feeling of pedal dullness, a certain initial lack of bite as elaborated by Daveo4EV.

Maybe it's me not modulating brakes properly. Occasionally a slower car would cut into the passing lane, I would start braking early, not stomping on the brakes rather braking firmly and managing but progressively reducing the following distance. 3-4 times though I ended up too close to the car ahead (by then doing 120-130 km/h).

not really risky but I got a less pleasant feeling vs. my G63 also on winters (275/40 I think, Michelin Alpin 5, at similar outside temps) and vs. a 2 year old audi RS6 (on P zero winters)

Were you feeling the ABS activating?

Winter tyres at 5 to 6 degrees are the best tyre for braking distance at that temperature.

The limit to braking will be tyre grip and if you weren't at the level where the ABS is kicking in you aren't on the limit.

If the car simply feels like it isn't slowing as much as you would like but you art not actually at the grip limit it is probably just that the car has less brake servo assistance than you are used to.

If you were on the grip limit you were going too fast for the road conditions

 

[Deleted member 1697]

130Km/h : 1-2 MJ
260Km/h : 5-10 MJ
350Km/h (rimac nevera) ? 10-15 MJ maybe
braking systems are awesome ! why it doesn't melt ? how that could handle so much energy in so little mass of metal

 

[Scandinavian]

130Km/h : 250 MJ
260Km/h : 1 GJ
350Km/h (rimac nevera) ? 2 GJ maybe
braking systems are awesome ! why it doesn't melt ? how that could handle so much energy in so little mass of metal

Don’t forget that the Taycan will recuperate at 270 kW also. So not just through the brake discs.

 

[ct-andy]

thanks. I am not sure which brakes I have (definitely not the PCCB). here s a photo on 21" and summer tires. probably the standard ones?

You have PSCB, upgraded one. I haven't got my 4s ct with PSCB yet, but I am surprised what you said about PSCB ?

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