JoeMag

For those of you with data aq and run R6's, what sort of braking G's do you see on flat track?

SG_M3

1.01-1.17 at a quick glance.

bobt993

Joe, are you running ABS and what ABS system if you are? With a non-motorsport system I don't think you can get much more than 1.2gs. With your car I would expect much higher decell using an advanced ABS or non-ABS system.

Astroman

OT but Joe, that is one bad-*** looking car you have in your avatar.

KOAN

I see consistent 1.2 gs at VIR with older R6s, with ABS on the front straight, and the braking zone is a little down hill. Coming down from about 148 mph.

himself

I am seeing just a little under 1.2 (1.17 - 1.19).

Interestingly, I went back and looked at the Pat Long data for the last couple years, and he only hit 1.159 once, and the rest of his braking loads were a hair under 1.1. And the slope of his trail braking force (vs normal braking force) is pretty noticeable. It seems like he is braking slighly less on entry, and then trailing WAY better. Nets ~1 second in his favor. *sigh*

-td

DM993tt

I commonly see 1.3 (into the toe of the boot @ WGI) - I have seen spikes to 1.4+ (275's f 315's r on a 3000lb car). Stock "big red" brakes - with pagid yellows.


I was running consistent low 2:09's this pig, but pause @ 2:52 in this vid. Showing neg 1.42g's going into the bust stop & again @5:00 going into bus stop. -1.5 braking G's @ 148mph

Check 3:26 too meter showing neg 1.61 going into the toe of the boot. Next lap it hits @ 5:32 -1.72G. You can really drop anchor going into that uphill before heading uphill.

Call BS on the G-box, I do catch a lot of faster cars in the brake zones.

ProCoach

Depends on the car, but at VIR, an R6 equipped 09 Z06 is dependably -1.32 to -1.40g going into T1, an A6 equipped 07 F430C is at -1.20 to -1.27 and most properly braked (and functioning) cars wearing R6's between -1.16 to -1.22g

YMMV

JoeMag

Thanks guy... so it looks like ~1.2g's is a resonable number. Those 1.4's seem impressive.

Astroman -- thx for compliment... I built the car, took 2.5 yrs; did not do cage, final paint, trans, half of motor MoTeC harness. Turned every other bolt (including motor), stripped every wire, welded body panel mount points, fitted body, etc, etc.

rmag

1.4-1.5 with pagid yellows into T1 VIR,T1 and T5 at Summit Point

SG_M3

I would take the number with a grain of salt. Spiking or sensor differences will vary the numbers. It would be more valuable to see the data graph. As said above, getting peak braking g's doesn't mean you are braking in a way that would provide the fastest lap time.

ProCoach

No question, but when over 85% of the data I see doesn't ever get close to these numbers, it provides a useful performance benchmark for drivers to shoot for. These are numbers that can be influenced by the attitude off horizontal the logger is mounted in the car! Still, Buddy Fey has established that with some variances, longitudinal g's generated under braking should approach 90-95% of total cornering loads.

As a diagnostic tool to validate drivers concerns that all was not well on the equipment side, I've seen glazed pads, alternate and incorrectly sized hydraulics and crappy corner weights materially impact the measurement of deceleration.

And this is even more true...

bobt993

I think Peter gives you the best suggestion. Post a data graph and info on what system your using. Some of the inexpensive DAS system are really not any more than a video game display (cool looking, but the actual numbers can be way off). The sampling rate of the data and resonance of the sensors must be really good to depend on the data results. As example you will often see accelerometers on these units not any better than 4hz (or worse) while some units like actually use 100hz devices. Peter can elaborate on this much more with his vast experience in DAS work.

If your using the factory ABS system your limited to the parameters that it allowed for what was a street car. An inexpensive option would be an ABS delete switch on the dash so you can get some data on max threshold braking. If your seeing big differences then source out a proper motorsport ABS system. Several shops on this board can provide them and they range from: Motec, Porsche, to BMW based controllers.

Veloce Raptor

THIS is IMO the most valuable input in this thread. Yesterday i was coaching a couple of folks. When I saw their previous best laps data as I prepared for yesterday, I was struck by the suddenness of their braking spikes & the absence of significant trail braking. I could tell from the data that the car was getting unsettled & this was ultimately hurting corner entry & delaying throttle...and was slow.

We spent a bunch of time yesterday working on exactly what TD saw in Pat Long's data: softer braking on entry, and longer trail braking to get the car to point. PRESTO: just doing that picked up huge segment time yesterday! As SG said, peak braking is not really relevant info for determining the fastest way around a track.








Professional Racing and Driving Coach

ProCoach

This is turning into a great discussion. Always enjoy VR's posts, as they have real-world value.

Certainly, when people get their braking systems working well and their confidence up, they get "punch drunk" with braking power and become addicted to stabbing the pedal, generating that spike and feeling it as the forward resistance of their shoulder harnesses digs into their chest and shoulders. I know I did. To my detriment. The peak spike was not what was important, it was what came after!

What is much more important, IMO, is consistency and being able to sustain that deceleration level over the course of a longer braking zone. Then, of course, measuring the efficacy of trail braking by overlapping the longitudinal g (braking force) with the rise of lateral g (cornering force) to see how well the braking is melded into the beginning of the cornering phase. A gSum (combined g) will do that too. Any precipitous drop in gSum between the end of braking and mid-corner lateral loading is wasted traction circle. So really, it's two issues. Braking efficiency (losing speed in the shortest distance) and staying on the periphery of the friction circle (a goal we should ALL have! )

I look at data from Tom Long, Leh Keen or David Murry (as well as a lot of "normal" people I consider accomplished in the art of proper braking) and they're generating on the high side of the range, but for the shortest possible distance and MUCH closer to the cornering phase than the average joe.

Remember, the more the aero, the more you'll (or should see) a higher initial decel rate, trailing off 15-30% as the speeds come down through the longer brake zones. Also, uphill zones like T14 at VIR (and downhill with compression, like the Toe of the Boot at the Glen) can skew long g data. I've seen over -1.75 for the same car I'm seeing -1.32 on the flat.