Rennteam 2.0 - EN - Forum - Unsprung mass and feeling - Page1

Dec 17, 2021 5:25:32 PM

HugoF: Newbie; Loc: Paris, France , France; Posts: 30, Gallery; Registered on: Nov 8, 2021

Unsprung mass and feeling

Hello everyone,

I have a very simple question.

We all heard about how keeping unsprung mass down was good for the handling, the feeling of the car, for the fuel economy... In a video of TheSmokingTire (https://www.youtube.com/watch?v=RiWQUfDYX8o at 7:30) he states that unsprung weight would have a ratio 6/1, meaning if you save 1kg of unsprung mass it is like saving 6kg.

So, now let's talk about brakes, an iron disc is about 16kg, a carbon one 7.5kg (let's round it up to 8). In conclusion you save 8kg per disc, now multiply this by x4 and then by x6 and you obtain: 144kg. So fitting carbon ceramic brakes would be like saving 144kg?

Now here is my question, if unsprung mass is that important (and I don't doubt it is), do you feel any difference when driving if you have carbon brakes and carbon wheels (for example)?

Thank you very much for your help and answer!

Hugo.

Next
Threads

Dec 17, 2021 5:50:34 PM

the-missile: Rennteam Master; Loc: The World , France; Posts: 3484, Gallery; Registered on: May 10, 2014; Reply to: HugoF

Re: Unsprung mass and feeling

PCCB against steel is like a 15kg saving. not 30+...

Yes you feel a difference in the steering wheel when you combine lighweight wheels and lightweight braking system. I had the chance to drive GT3RS.1 equipped with FI-R wheels and AP Skeleton racing brakes and it was incredibly light steering feel.

The only issue you will face with that strategy, every kg less after the easy stuff will add a 0s to the bill.

--

GT Lover, Porsche fan

991.2 GT3 manual

Cayenne GTS 2014

Next
Threads

Dec 17, 2021 5:59:11 PM

Mithras: Expert; Loc: Toronto, Canada , Canada; Posts: 1981, Gallery; Registered on: Mar 16, 2005; Reply to: the-missile

Re: Unsprung mass and feeling

I"ve found you can notice anything over about 1kg per corner and 5kg would be a significant difference in feel. Like walking around in super heavy winter boots vs thin driving moccasins.

--

Past-President, Porsche Club of America - Upper Canada Region

Next
Threads

Dec 17, 2021 6:26:10 PM

Leawood911: Rennteam VIP; Loc: Kansas, USA , United States; Posts: 6924, Gallery; Registered on: Aug 29, 2006; Reply to: Mithras

Re: Unsprung mass and feeling

Unsprung eight makes a big difference. That said, carbon fiber wheels are either super expensive or dangerously fragile.

Next
Threads

Dec 17, 2021 6:58:58 PM

Enmanuel: Rennteam VIP; Loc: Boston , United States; Posts: 8862, Gallery; Registered on: Mar 7, 2008; Reply to: Leawood911

Re: Unsprung mass and feeling

Leawood911:
Unsprung eight makes a big difference. That said, carbon fiber wheels are either super expensive or dangerously fragile.

Or both.

Next
Threads

Dec 17, 2021 7:13:17 PM

CGX car nut: Rennteam Master; Loc: NWI , United States; Posts: 5196, Gallery; Registered on: Aug 17, 2011; Reply to: Enmanuel

Re: Unsprung mass and feeling

With most cars one can feel the difference between winter and summer tires if the winters are smaller than the summers, meaning there is less mass per corner. At one time if your car had 18 inch wheels for the summer it was expected that you would have a 17 inch wheel with correspondingly smaller tires in the winter. That change is alway noticeable as the car will feel a bit quicker in acceleration as the rotational inertia is reduced.

Next
Threads

Dec 25, 2021 11:04:02 AM

DaveGordon: Rennteam Pro; Loc: Zürich , Switzerland; Posts: 2774, Gallery; Registered on: Aug 20, 2007; Reply to: CGX car nut

Re: Unsprung mass and feeling

I put a set of lightweight forged wheels on my Boxster once. Saved about 9KG in total I think. Felt the difference immediately and loved it. Steering felt more communicative, and the suspension seemed to work better - the tyres finding more grip on undulating surfaces. Worth every penny in my opinion. Also worth looking at the tyre weights as these can vary quite a bit. Michelins are usually on the lighter end of the scale.

I took a further step with the next one and put PCCBs on it. Didn't feel the same incremental improvement, was more subtle - I think as the weight saved is closer to the rotational centre.

--

2019 911 GT3 RS,1964 Type 1

Next
Threads

Dec 25, 2021 11:39:55 AM

TB993tt: Rennteam Pro; Loc: manchester , United Kingdom; Posts: 2280, Gallery; Registered on: Jul 22, 2002; Reply to: DaveGordon

Re: Unsprung mass and feeling

I don't subscribe to these kinds of calculations leading to statements like "8kg per disc unsprung worth 144kg sprung" but I think this is engineers trying to explain the concept.

I had a set of carbon Dymag wheels on my GT2 which weigh around 9 to 10kg each they proved difficult to maintain ie any slight curbing was a PIA and the carbon finish was not durable. I swapped the Dymags for my current BBS Fi aluminium wheels, the total weight of the Dymags was ~38kg, the total weight of the BBS Fi is 33kg so the BBS must have felt lighter right ?

Well the answer is an emphatic NO and as I'm sure everyone has surmised by now the Carbon rims felt noticeably lighter particularly in the steering, it is of course the rotating mass at the outer edge of the wheel being CF has less rotational inertia (is that the correct term ?) it was quite interesting to feel the difference !

Recently I put some new wheels on my Merc V van, same size 9X20 and weight ~13.5kg as what they replaced but the new wheels boasted they were made by a new process called "Rotary Forging" which makes the outer rim much lighter than a conventional alloy wheel. I thought this was marketing blurb but I was amazed that YES the steering felt immediately noticeably lighter and the handling just feels that little bit lighter....

Lastly I have a little project car, a K20 engined Mugen Honda Civic yes I know, yuck, but think 260 NA hp and 9000rpm without going to jail for 150mph Smiley , this wore 19" rims at 11.8kg a piece, I swapped for 18" Mugen GP wheels at 7.3kg also special Spoon monoblock calipers together with floating discs saving ~4kg and Fightex aluminium suspension saving Xkg and the handling transformation is superb, much better tyre contact and big improvement in ride kiss

--

997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar

993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.

Next
Threads

Dec 26, 2021 1:32:59 PM

BjoernB: Rennteam Master; Loc: Switzerland , Switzerland; Posts: 4100, Gallery; Registered on: Oct 19, 2004; Reply to: TB993tt

Re: Unsprung mass and feeling

Porsche's with 'no" weight in the front have a unique turn in anyway - and I only felt the difference on PCCB's with their top breaking point compared to steel but I could not feel the difference between PCCB and Steel Rotor from a turn in prospective. To me a 812 or F12 has way to aggressive (fast) front steering - 812 being surely much better than the F12 - but I think Porsche has perfected steering feel in any 911 - nothing comes close in my view.

Next
Threads

Dec 26, 2021 5:22:28 PM

Whoopsy: Rennteam Moderator; Loc: Vancouver,BC , Canada; Posts: 16151, Gallery; Registered on: Sep 19, 2006; Reply to: BjoernB

Re: Unsprung mass and feeling

I have tracked both brakes on a GT3RS on the same day. I'd be lying if I say I felt a difference in steering feel.

I think the electric steering boost masked the differences. Both cars pretty much offer the same feel on the steering wheel. About the only difference I can feel would be over curbs. The oscillation is slightly different but can't say I prefer one over another.

--

Next
Threads

Dec 27, 2021 10:02:20 AM

TB993tt: Rennteam Pro; Loc: manchester , United Kingdom; Posts: 2280, Gallery; Registered on: Jul 22, 2002; Reply to: BjoernB

Re: Unsprung mass and feeling

BjoernB:
Porsche's with 'no" weight in the front have a unique turn in anyway - and I only felt the difference on PCCB's with their top breaking point compared to steel but I could not feel the difference between PCCB and Steel Rotor from a turn in prospective. To me a 812 or F12 has way to aggressive (fast) front steering - 812 being surely much better than the F12 - but I think Porsche has perfected steering feel in any 911 - nothing comes close in my view.

Have you tried a Mclaren ?

--

997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar

993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.

Next
Threads

Dec 27, 2021 4:30:45 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12588, Gallery; Registered on: Aug 21, 2002; Reply to: TB993tt

Re: Unsprung mass and feeling

When I put big 4-piston 930 Turbo brakes on my 911 with way bigger rotors (replacing the tiny original 2-piston calipers and small/light rotors), it made the steering feel very different (it increased the effort of the manual rack and also added a sense of more straight-ahead stability from the much larger gyroscopic effect).

--

22 GT3 Manual, 73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 18 GT3 Manual, 16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550, 79 635CSi

Next
Threads

Dec 28, 2021 12:23:38 AM

TB993tt: Rennteam Pro; Loc: manchester , United Kingdom; Posts: 2280, Gallery; Registered on: Jul 22, 2002; Reply to: Grant

Re: Unsprung mass and feeling

Grant:
When I put big 4-piston 930 Turbo brakes on my 911 with way bigger rotors (replacing the tiny original 2-piston calipers and small/light rotors), it made the steering feel very different (it increased the effort of the manual rack and also added a sense of more straight-ahead stability from the much larger gyroscopic effect).

This was Alois Ruf's reasoning to why their original Ruf 17" wheels were so heavy on the Yellowbird, he said it gave extra stability at 213mph !

--

997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar

993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.

Next
Threads

Dec 28, 2021 6:02:58 AM

BjoernB: Rennteam Master; Loc: Switzerland , Switzerland; Posts: 4100, Gallery; Registered on: Oct 19, 2004; Reply to: TB993tt

Re: Unsprung mass and feeling

TB993tt:
BjoernB:
Porsche's with 'no" weight in the front have a unique turn in anyway - and I only felt the difference on PCCB's with their top breaking point compared to steel but I could not feel the difference between PCCB and Steel Rotor from a turn in prospective. To me a 812 or F12 has way to aggressive (fast) front steering - 812 being surely much better than the F12 - but I think Porsche has perfected steering feel in any 911 - nothing comes close in my view.

Have you tried a Mclaren ?

Good point ~ the 675 LT was special too but i would say because of the carbon tub and the unique damper system.

Next
Threads

Dec 28, 2021 7:37:25 AM

Whoopsy: Rennteam Moderator; Loc: Vancouver,BC , Canada; Posts: 16151, Gallery; Registered on: Sep 19, 2006; Reply to: BjoernB

Re: Unsprung mass and feeling

BjoernB:
TB993tt:
BjoernB:
Porsche's with 'no" weight in the front have a unique turn in anyway - and I only felt the difference on PCCB's with their top breaking point compared to steel but I could not feel the difference between PCCB and Steel Rotor from a turn in prospective. To me a 812 or F12 has way to aggressive (fast) front steering - 812 being surely much better than the F12 - but I think Porsche has perfected steering feel in any 911 - nothing comes close in my view.

Have you tried a Mclaren ?

Good point ~ the 675 LT was special too but i would say because of the carbon tub and the unique damper system.

Yeah well the 12C was already ahead way back then, that 12C platform is truly world class. It was the best car to drive but the worst car to own, just like any other McLaren

--

Next
Threads

Dec 28, 2021 11:12:24 AM

TB993tt: Rennteam Pro; Loc: manchester , United Kingdom; Posts: 2280, Gallery; Registered on: Jul 22, 2002; Reply to: BjoernB

Re: Unsprung mass and feeling

BjoernB:
TB993tt:
BjoernB:
Porsche's with 'no" weight in the front have a unique turn in anyway - and I only felt the difference on PCCB's with their top breaking point compared to steel but I could not feel the difference between PCCB and Steel Rotor from a turn in prospective. To me a 812 or F12 has way to aggressive (fast) front steering - 812 being surely much better than the F12 - but I think Porsche has perfected steering feel in any 911 - nothing comes close in my view.

Have you tried a Mclaren ?

Good point ~ the 675 LT was special too but i would say because of the carbon tub and the unique damper system.

Weirdly I found the 570S to have the nicest steering compared to my 720S and probably on a par with the 765LT - go figure broken heart

--

997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar

993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.

Next
Threads

Dec 29, 2021 10:52:18 AM

crayphile: Rennteam Pro; Loc: England , United Kingdom; Posts: 2861, Gallery; Registered on: Jun 16, 2004; Reply to: TB993tt

Re: Unsprung mass and feeling

TB993tt:

Weirdly I found the 570S to have the nicest steering compared to my 720S and probably on a par with the 765LT - go figure

This was my experience too. I have written on several occasions that the 570 has the best steering feel of any modern production car I have driven.

Next
Threads

Dec 29, 2021 12:41:48 PM

TB993tt: Rennteam Pro; Loc: manchester , United Kingdom; Posts: 2280, Gallery; Registered on: Jul 22, 2002; Reply to: crayphile

Re: Unsprung mass and feeling

crayphile:
TB993tt:

Weirdly I found the 570S to have the nicest steering compared to my 720S and probably on a par with the 765LT - go figure

This was my experience too. I have written on several occasions that the 570 has the best steering feel of any modern production car I have driven.

Smiley

--

997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar

993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.

Top
Threads

Board	Subject	Last post	Views	Replies
Porsche	SUN'S LAST RUN TO WILSON, WY - 991 C2S CAB LIFE, END OF AN ERA (Part II)	5/15/24 8:44 AM art.italy	811368	1808
Porsche	Welcome to Rennteam: Cars and Coffee... (photos)	4/7/24 11:48 AM Boxster Coupe GTS	451380	565
Porsche	OFFICIAL: Porsche 911 (992) GT3 RS - 2022	3/12/24 8:28 AM DJM48	268851	323
Porsche	The new Macan: the first all-electric SUV from Porsche	1/30/24 9:18 AM RC	91552	45
Porsche	OFFICIAL: Taycan 2024 Facelift	3/15/24 1:23 PM CGX car nut	8369	50
Porsche	The moment I've been waiting for...	2/1/24 7:01 PM Pilot	890201	1364
Porsche	992 GT3	7/23/23 7:01 PM Grant	847527	3868
Porsche	GT4RS	4/21/24 11:50 AM mcdelaug	403894	1454
Porsche	Welcome to the new Taycan Forum!	2/10/24 4:43 PM nberry	400384	1526
Others	Tesla 2 the new thread	12/13/23 2:48 PM CGX car nut	387701	2401
Porsche	Donor vehicle for Singer Vehicle Design	7/3/23 12:30 PM Porker	372610	797
Porsche	Red Nipples 991.2 GT3 Touring on tour	5/12/24 6:23 PM blueflame	295001	669
Porsche	Collected my 997 GTS today	10/19/23 7:06 PM CGX car nut	269255	812
Lambo	Huracán EVO STO	7/30/23 6:59 PM mcdelaug	245124	346
Lotus	Lotus Emira	6/25/23 2:53 PM Enmanuel	239504	101
Others	Corvette C8	10/16/23 3:24 PM Enmanuel	223615	488
Others	Gordon Murray - T.50	11/22/23 10:27 AM mcdelaug	174165	387
Porsche	Back to basics - 996 GT3 RS	6/11/23 5:13 PM CGX car nut	145830	144
BMW M	2024 BMW M3 CS Official Now	12/29/23 9:04 AM RC	122399	303
Motor Sp.	2023 Formula One	12/19/23 5:38 AM Whoopsy	114375	685
Porsche	2022 992 Safari Model	3/7/24 4:22 PM Whoopsy	86730	239
AMG	Mercedes-Benz W124 500E aka Porsche typ 2758	2/23/24 10:03 PM blueflame	77013	297
Porsche	992 GT3 RS	3/3/24 7:22 PM Whoopsy	56171	314
Motor Sp.	Porsche 963	5/18/24 9:44 PM Wonderbar	27931	249
Ferrari	Ferrari 296 GTB (830PS, Hybrid V6)	1/21/24 4:29 PM GT-Boy	22570	103
BMW M	2022 BMW M5 CS	4/8/24 1:43 PM Ferdie	21318	140
AMG	G63 sold out	9/15/23 7:38 PM Nico997	17771	120
AMG	[2022] Mercedes-AMG SL	4/23/24 1:24 PM RC	15800	225
Porsche	Porsche Mission X Hypercar	12/3/23 8:52 AM 996FourEss	11702	63
Porsche	911 S/T	10/10/23 8:53 AM RC	11051	55

Crown

Forum - Thread

Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Re: Unsprung mass and feeling

Forum

Boards