RCF is Faster than the M4 and Audi RS5 on a Closed Track
#46
Lexus Test Driver
RC-F was not faster in the MT testing. I say it's a driver''s race between the two on a track. That's because the RCF is slower technically but easier to drive and the M being faster but more difficult becuase of the oversteer.
Also, the type of track used will also factor in.
Also, the type of track used will also factor in.
Randy Pobst is a professional race car driver. He can extract more out of the car than 99% of the drivers on the road can. If can only get 3/10ths more out of a second out of the M4 on that specific track, majority of the drivers will not be able to do that. Also, remember the M4 had the optional $10K carbon ceramic brakes that made the difference. On standard steel brakes like the RC-F, RC-F would have been quicker.
Besides, the issue is not oversteer. The issue in the M4 is the power delivery. RT said, M4 has a very unpredictable and non-linear power curve (some of it could be attributed to boost lag where there is no power once the throttle is pressed and suddenly gobs of torque available upsetting the chassis resulting in the rear end breaking loose.
Last edited by 05RollaXRS; 11-13-14 at 03:50 PM.
#48
Tech Info Resource
iTrader: (2)
On what basis do you make this argument? It certainly isn't stopping power because carbon or steel makes no difference in stopping distance. Tires and available traction make all the difference in stopping power. So you are assuming the small difference in unsprung weight gave the M4 the advantage?
#49
Lexus Test Driver
On what basis do you make this argument? It certainly isn't stopping power because carbon or steel makes no difference in stopping distance. Tires and available traction make all the difference in stopping power. So you are assuming the small difference in unsprung weight gave the M4 the advantage?
I 100% believe the lighter weight (read 15 lbs per corner on Bimmer forums), having better late braking ability due to better clamping force design and less brake fade over multiple lap all contributed to the M4 lap time.
Last edited by 05RollaXRS; 11-15-14 at 11:19 AM.
#50
Tech Info Resource
iTrader: (2)
Randy does multiple laps in each car. The brake fade on the carbon ceramic over steel brakes would have been less giving Randy more ability to brake late in M4. Plus, as 4TehNguyen once posted the specs, M4 carbon ceramic brakes have superior design complete with more clamping force through more pistons (6 front, 6 back) than the steel brake version. The lighter weight (read 15 lbs per corner on Bimmer forums), having better late braking ability due to better clamping force design and less brake fade over multiple lap all contributed to the M4 lap time.
The only advantage is unsprung weight and overall car mass, and that is the big question mark on a track as smooth at Streets. If it were as hashed as the track they set up for the AMCI testing, I'd say there's more of a chance, but there is no inherent fade resistance difference anyone will notice on a track this short and this slow.
Last edited by lobuxracer; 11-15-14 at 11:26 AM.
#51
Lexus Test Driver
The simple facts that ceramic brakes stay cooler over the course of intense use will make them slightly more effective, but it's true that the benefits are marginal on anything but paper.
#52
Lexus Test Driver
The carbon ceramic brakes are 6 piston front and 6 piston rear. The standard steel brakes are 4 pistons front and 2 pistons back. I personally believe it makes a significant difference.
Last edited by 05RollaXRS; 11-15-14 at 11:44 AM.
#53
Well, many M4 owners have reported that stock brakes do fade after 5-6 laps... so maybe RC-F's dont (and all reviews said so far that they dont), but M4's sure do.
#55
Lexus Test Driver
I didnt realize that RC-F was faster than M4 on RT track:
http://www.roadandtrack.com/car-revi...he-motown-mile
Obviously RC-F is such a heavy, terrible car :-)))))
http://www.roadandtrack.com/car-revi...he-motown-mile
Obviously RC-F is such a heavy, terrible car :-)))))
Randy Pobst on Laguna Seca is much much superior to this shoddy effort. We have to wait till the end of the 2015 to see how RC-F does around Laguna Seca.
Last edited by 05RollaXRS; 11-15-14 at 12:26 PM.
#56
Liquid Bra Champion
Uh no! They don't stay cooler. CCB's work better under higher temps, whereas steel will fade. CCB's work at their optimal once they're brought up to temp.
#57
Tech Info Resource
iTrader: (2)
It has better design than the steel brake version installed on M4. According to BMW, it gives more clamping force than steel brakes so stronger braking abilities.
The carbon ceramic brakes are 6 piston front and 6 piston rear. The standard steel brakes are 4 pistons front and 2 pistons back. I personally believe it makes a significant difference.]
The carbon ceramic brakes are 6 piston front and 6 piston rear. The standard steel brakes are 4 pistons front and 2 pistons back. I personally believe it makes a significant difference.]
#58
Lexus Test Driver
James Walker, a senior stability and braking systems designer says calipers do not stop the car, and all this chatter about carbon brakes misses the whole reason they exist in racing - they drop unsprung weight dramatically. They have zero advantage in stopping power because the brakes don't stop the car. The tires do. You can believe anything you want, but it is not based in science or engineering, it's just belief.
Not only resistance to brake fade due to carbon ceramics, in the case of M4, if you think clamping force of 6 pistons front and 6 pistons back does not make a difference compared to 4 pistons front and 2 pistons back then that is laughably ridiculous.
I will leave it at that.
Last edited by 05RollaXRS; 11-15-14 at 01:55 PM.
#59
Tech Info Resource
iTrader: (2)
Marketing over science and engineering. Nice pick.
Here's a great primer written by a guy who has forgot more than the sum of Club Lexus knows about braking systems. He wrote it in 1991 for Grassroots Motorsports Magazine, but it is timeless.
http://www.scirocco.org/faq/brakes/p...n/pfpage1.html
Here's a great primer written by a guy who has forgot more than the sum of Club Lexus knows about braking systems. He wrote it in 1991 for Grassroots Motorsports Magazine, but it is timeless.
http://www.scirocco.org/faq/brakes/p...n/pfpage1.html
#60
Lexus Test Driver
This video illustrates it best.
LFA on cold brakes with ceramic brakes accelerated quicker, but braked 2 feet longer than the R8 V10 with steel brakes.
Then on the second run, LFA's brake now with some heat in them stopped shorter than its first run while R8 V10 with steel brakes stopped 17 feet longer than its first run.
Pro race car drivers also explaining why LFA was getting better on second run with carbon ceramics and why R8 V10 was getting worse with steel brakes suffering fade after just one run.
Irrefutable real world proof of how carbon ceramic brakes get better and better as they heat up while steel brakes (even as huge as the one's on the R8 V10) rapidly fade.
LFA on cold brakes with ceramic brakes accelerated quicker, but braked 2 feet longer than the R8 V10 with steel brakes.
Then on the second run, LFA's brake now with some heat in them stopped shorter than its first run while R8 V10 with steel brakes stopped 17 feet longer than its first run.
Pro race car drivers also explaining why LFA was getting better on second run with carbon ceramics and why R8 V10 was getting worse with steel brakes suffering fade after just one run.
Irrefutable real world proof of how carbon ceramic brakes get better and better as they heat up while steel brakes (even as huge as the one's on the R8 V10) rapidly fade.
Last edited by 05RollaXRS; 11-15-14 at 02:17 PM.