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i'd be most grateful if some of the STS, STS2, or STX folks could comment on the range of data for lateral acceleration they see, and consider competitive

i'm a bit timid to ask, and searched as carefully as i could before risking a thread

posts in the ST* forums do contain some helpful numbers for STU based tire comparisons, indicating a range of 1.1x to 1.2x g - but that one data point was all i could find (and those tires were 245 or greater)

under good conditions (70-80 degree air, less than 100 degree track, dry) what is ok, what is good, and what is impressive?

i've only my own data with which to make tire comparison decisions, so i know what's faster on my setup - do NOT know what's fast enough in ST*

my data says

1.09 peak last year (225/45-15 RS2)

1.05 reliably last year - several events in this range

1.03 thus far on 195/55-15 Z1 Star Spec - poor but dry conditions (less than 50 deg air temp)

what i THINK i know is that > 1 is OK, 1.1 is good, and 1.2 is damned impressive

i've only seen 1.2 and greater on this chassis when running 205/50-15 Hoosiers

perhaps i am asking a sensitive question for the serious folks, and if so please excuse my ignorance

thanks very much

 

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

I think you're pretty close there. As I'm sure you know, the situation gets complicated very quickly and lateral G numbers are going to depend an many factors. Peak values are only part of the picture.

I would send you some datalogs of my own to compare, but the only ST data I have handy are from an STU car.

 donour

Depends so much on the surface it's hard to say. I only look at the G value as meaning a whole lot when it's in a long sweeper or there's too much noise usually. In my STS car on concrete on RE-01Rs I'm usually around 1.15G or so. Unless it's cold or dirty or raining or ...

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Brian Davis, 89 Civic Si, 158 STS

What are you using to measure g's with?

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Ryan K

redwhale240:

What are you using to measure g's with?

That probably matters a whole lot too. I trust all of the quality dataloggers to provide consistent numbers so that you can compare from run to run. But I don't really trust them to provide totally accurate numbers, so that you can compare between different dataloggers. I'm using MaxQ personally. 

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Brian Davis, 89 Civic Si, 158 STS

turbohappy:

redwhale240:

What are you using to measure g's with?

That probably matters a whole lot too. I trust all of the quality dataloggers to provide consistent numbers so that you can compare from run to run. But I don't really trust them to provide totally accurate numbers, so that you can compare between different dataloggers. I'm using MaxQ personally. 

 I also just got my maxQ.  Just curious what kind of g's do you pull in your civic?  I'm on stones driving on asphalt and my maxQ spit out a max of 1.15 with the data smoothing one click under max.
 

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Ryan K

This whole thread is like comparing dyno runs on different dynos in different cities on different days using different operators.  In short, useless.  The only real comparable data is same day, same test equipment, same driver, simple course (aka skidpad).  Even then, it takes good technique and test process (A-B-A) to generate decent data.

--Andy

Andy Hollis:

This whole thread is like comparing dyno runs on different dynos in different cities on different days using different operators.  In short, useless.  The only real comparable data is same day, same test equipment, same driver, simple course (aka skidpad).  Even then, it takes good technique and test process (A-B-A) to generate decent data.

--Andy

 

Andy I understand that kind sir - I didn't just fall off the melon truck.  I expect a range, not an answer.

With respect, it is useful to me - in the context of "ball park" only.

So I can understand your reticence regarding your own data, but I'm a bit disappointed with your characterization of the thread.

Cheers.

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

cmt52663:

Andy I understand that kind sir - I didn't just fall off the melon truck.  I expect a range, not an answer.

With respect, it is useful to me - in the context of "ball park" only.

So I can understand your reticence regarding your own data, but I'm a bit disappointed with your characterization of the thread.

Cheers.

I'm with Andy on this one, that's what I was trying to say above. I actually had a T&T at a site that was half concrete and half asphalt...pretty large difference in my max gs just from that. Add in difference between dataloggers (the dyno comment) and it's pretty impossible to judge. If you talk to someone using the same model of datalogger at the same event in a different car, then you might have useful info. 

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Brian Davis, 89 Civic Si, 158 STS

I do quite take your point Brian, and thank all for their responses - editorial and otherwise.

 

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

cmt52663:

Andy Hollis:

This whole thread is like comparing dyno runs on different dynos in different cities on different days using different operators.  In short, useless.  The only real comparable data is same day, same test equipment, same driver, simple course (aka skidpad).  Even then, it takes good technique and test process (A-B-A) to generate decent data.

--Andy

 

Andy I understand that kind sir - I didn't just fall off the melon truck.  I expect a range, not an answer.

With respect, it is useful to me - in the context of "ball park" only.

So I can understand your reticence regarding your own data, but I'm a bit disappointed with your characterization of the thread.

Cheers.

Andy has been more than willing to share data. I have some of his logs from last years Milwaukee tour. I am certain he has been more than willing to share data with others as well.

I have seen anywhere from 1.05g on Falkens on asphalt all the way up to 1.25g on Bridgestones on both asphalt and concrete on my STS2 Miata. Brian and I usually run on the same sites often on the same days. We both use MaxQData. We have quite a few data logs from this weekend that are on the same site on the same day on two different cars but we have yet to compare them. I will try to send them to Brian so that he can compare and then maybe he will post his findings.

 

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90 Miata/89 CRX - STS2 #90/190

thanks very much for that range

i must have been thin skinned yesterday to use that "reticence" phrase - i have read much of what Andy has shared in public domain, and he's been one of the best teachers i've had, that i have never met

sincerely,

charlie

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

From what I've seen of MaxQ data is that the numbers collected are higher then the numbers collected with my DL1. Chang's MaxQ seems to read consistently .1g's higher then my DL1 does for both peak and sustained. At Devens, my DL1 in the STS car would read ~1.1g's on 'Stones in good weather. Colder, it would fall off a little. It is very important to note that accelerometers are extremely sensitive to being mounted level. Off by even small amounts can artificially inflate your numbers (or deflate them) by a considerable amount. GPS based loggers that don't use accelerometers are less sensitive to this, but then you have the compensation for satellite drift and so on. IIRC, the MaxQ combines accelerometer and GPS data. That is good, but the compensation factor for mounting offsets could be set differently.

Charlie, contact Chang and see if he can send you some of his ST MaxQ data. I can send you some DL1 data, but you'll have to grab the software from RaceTechnology to process it.

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Nate Whipple
NER
188/88 DSP ITR

solo-x:

IIRC, the MaxQ combines accelerometer and GPS data. That is good, but the compensation factor for mounting offsets could be set differently.

MaxQGPS doesn't use an actual accelerometer, so it doesn't need to be level. It uses an advanced GPS feature to determine velocity vector (speed & direction) and interprets from changes in that as I understand.

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Brian Davis, 89 Civic Si, 158 STS

solo-x:

From what I've seen of MaxQ data is that the numbers collected are higher then the numbers collected with my DL1. Chang's MaxQ seems to read consistently .1g's higher then my DL1 does for both peak and sustained. At Devens, my DL1 in the STS car would read ~1.1g's on 'Stones in good weather. Colder, it would fall off a little. It is very important to note that accelerometers are extremely sensitive to being mounted level. Off by even small amounts can artificially inflate your numbers (or deflate them) by a considerable amount. GPS based loggers that don't use accelerometers are less sensitive to this, but then you have the compensation for satellite drift and so on. IIRC, the MaxQ combines accelerometer and GPS data. That is good, but the compensation factor for mounting offsets could be set differently.

Charlie, contact Chang and see if he can send you some of his ST MaxQ data. I can send you some DL1 data, but you'll have to grab the software from RaceTechnology to process it.

 

You rule - thanks!  I'll inquire this weekend.

I just completed a wet pavement pressure test session (after re-reading Andy's Falken/Bridgestone test in the GRM Miata series as an example of good method).

Results are in Word, here (very sorry but enclosures in this forum thus far escape me).  http://www.northamericanmotoring.com/forums/attachment.php?attachmentid=31817&d=1209485928

The bottom line is that (1) the Z1s work better than any prior tire, and (2) I'd NEVER have guessed the tire pressures that delivered best balance and overall grip without the dedicated session and due care.

The other bottom line is that it sure would be nice to have a clock - but my "under the radar" test site does not permit marking or elapsed time measurement.

Consistantly over a g in the wet with forgiving breakaway - just right for my fairly numb hands!

 

 

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

What pressures did you end up with?  That forum requires membership to view.

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Paul Przyborski

Currently running a 1996 BMW 318ti in STS.
Also now building a CP 1981 Camaro.

http://www.mewhiney.org
http://www.teamziptie.com

JCW Cooper - Wet Pressure Testing - Dunlop Direzza Star Spec Z1 195/55-15      
      
Run Front Rear Right g Max Left g Max    Balance Comments             Test Comments
1     35     42       0.94             0.98          understeer everywhere         baseline - just a SWAG from other tires
2     35     46       0.00             0.00          less understeer lost data -   go higher in back to search for balance
3     37     46       1.01             0.98          not bad, car wants to turn    go higher in front to search for max grip
4     37     48       1.00             1.05          not bad, car wants to turn    go higher in back to search for balance
5     34     48       1.01             1.01          not bad, car wants to turn    go lower in front to sanity check
6     40     48       1.05             1.03          good, on demand oversteer  go higher in front to search for max grip

Run 1 left, run 6 right - manouvre is a low speed oval, unwind a bit on exit roll on throttle, wind into next turn lift throttle - no brakes speed range is 30-40mpg (noisy rpm signal from the mini, but in 2nd 2k rpm = 20, 3k = 30 etc.)

One of several images - this one happens to be clockwise...

i set front tyre pressures for max grip, and rear pressures to dial out understeer

i'd have bet money that best wet grip was a LOT lower than where i found it

mind you these are 195/55-15 on a 15x7 so there is plenty of support from the rim for the contact patch, and the bead is wide, not pinched a bit as would be the case with a 225

Andy's approach is far more sophisticated - I have no marked course, no clock, and a lot less experience.

the test results doc has a sincere disclaimer for beginner's method - YMMV

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Charlie Thompson
'04 JCW Cooper [STX]
NER Cannon Fodder

solo-x:

From what I've seen of MaxQ data is that the numbers collected are higher then the numbers collected with my DL1. Chang's MaxQ seems to read consistently .1g's higher then my DL1 does for both peak and sustained. At Devens, my DL1 in the STS car would read ~1.1g's on 'Stones in good weather. Colder, it would fall off a little. It is very important to note that accelerometers are extremely sensitive to being mounted level. Off by even small amounts can artificially inflate your numbers (or deflate them) by a considerable amount. GPS based loggers that don't use accelerometers are less sensitive to this, but then you have the compensation for satellite drift and so on. IIRC, the MaxQ combines accelerometer and GPS data. That is good, but the compensation factor for mounting offsets could be set differently.

A coupla points on this:

1) The baseline (i.e. inexpensive) MaxQData setup is GPS-only and suffers from the software indirection imprecision that Nate mentions above.  Their more expensive models with built-in hi-res accelerometers are similar to the DL1 setup, in accuracy, precision, and price.

2) A three-axis accelerometer does not have the leveling issue as does a two-axis unit, since it can be "zero-leveled" to any plane prior to data collection.  This assumes the software is written to accomodate.

3) Another thing which affects the actual output of GPS-based systems is the smoothing function used to deal with both noise and data spikes.  If you go back and turn the smoothing down to zero, you can see some really bizarre raw data, particularly for five-Hz units. 

--Andy