Click to go to Forum Home Click to go to maXbimmer Home

Go Back   maXbimmer Forums > General > Track Junkies
User Name
Password


Welcome to Maxbimmer.com!

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

Reply
 
Thread Tools Rate Thread Display Modes
Old 04-03-2012, 01:17 PM   #31
Dinanstu
3rd Gear Member
 
Join Date: Dec 2011
Location: Toronto, Canada
Posts: 315
dcramer,

The ideal gas law is PV=nrT. Don't forget the 'T'!

All tires have different compounds and different optimal temperature ranges. The handling characteristics of all tires vary, but you know that....everybody knows that.

What exactly do you want to know?
Dinanstu is offline   Reply With Quote
Old 04-03-2012, 01:56 PM   #32
dcramer
5th Gear Member
 
Join Date: Nov 2010
Location: Orangeville
Posts: 1,103
Cut and paste, forgot the T

So is the difference between static and kinetic friction dramatically different for R-comp tires vs very good street tires ? Or stated another way do R-comps really break away faster than street tires ?
dcramer is offline   Reply With Quote
Old 04-03-2012, 02:24 PM   #33
T.Dot_E30
Classifieds Moderator
 
T.Dot_E30's Avatar
 
Join Date: Apr 2003
Location: T.Dot
Posts: 9,283
Quote:
Originally Posted by dcramer View Post
Or stated another way do R-comps really break away faster than street tires ?
I think you are getting what the others are saying about r-comps wrong. They don't 'break away' faster, it's that you are going much faster when they break loose, therefore making it harder for an unskilled driver to recover if they don't know what they are doing. Also they mask alot of driver mistakes since the limits are higher, so typically screwing up on r-comps has bigger consequences.

Also this is only one school of thought, which differs, everyone is different and learn differently, but this is a more cautious/safer approach to build up speed gradually.

It would probably be akin to jumping into an F1 car without and track or racing experience, you probably want to start off with something easier to learn on...
__________________
T.Dot_E30 is offline   Reply With Quote
Old 04-03-2012, 02:52 PM   #34
dcramer
5th Gear Member
 
Join Date: Nov 2010
Location: Orangeville
Posts: 1,103
Quote:
Originally Posted by T.Dot_E30 View Post
I think you are getting what the others are saying about r-comps wrong. They don't 'break away' faster, it's that you are going much faster when they break loose, therefore making it harder for an unskilled driver to recover if they don't know what they are doing. Also they mask alot of driver mistakes since the limits are higher, so typically screwing up on r-comps has bigger consequences.
Actually this is what I argued in the first place is that they break away the same, but at a faster speed. There is actually some evidence to the contrary, but I'd like to find more.

Quote:
Also this is only one school of thought, which differs, everyone is different and learn differently, but this is a more cautious/safer approach to build up speed gradually.
FWIW, my formative years of driving were spent driving mostly sideways, first in a field when I was 14, then on country roads. Recovering from slides is not a new concept.
dcramer is offline   Reply With Quote
Old 04-03-2012, 03:02 PM   #35
Dinanstu
3rd Gear Member
 
Join Date: Dec 2011
Location: Toronto, Canada
Posts: 315
Static and Kinetic friction is variable with all materials... Silk and sandpaper?

Instructors are giving you good solid advice at a starting point. You have a nice car, and you should be prepared to protect it and yourself and me if I'm on the track too.

There is always a point that the tire (any tire) will have grip to no grip and lose control. The R tires have much more grip, to a point, which will be a higher cornering speed, so when it goes, you go with it. Its very much akin to surface conditions and tire quality..ie snow, rain etc...hence the invention of anti-lock brakes that maximize the tire grip in adverse conditions. Poor tires squeal at the Timmy's drive-through, so you know what the limits are.
The problem here is Mosport can be very unforgiving and you woudn't want your car backed into the wall at turn 1!
Dinanstu is offline   Reply With Quote
Old 04-03-2012, 04:07 PM   #36
Aero
2nd Gear Member
 
Aero's Avatar
 
Join Date: Feb 2011
Location: Ottawa
Posts: 69
Quote:
Originally Posted by dcramer View Post
Cut and paste, forgot the T

So is the difference between static and kinetic friction dramatically different for R-comp tires vs very good street tires ? Or stated another way do R-comps really break away faster than street tires ?
The way pneumatic tires generate grip is much more complicated than the Coulomb or "dry" friction model, which involves static and kinetic friction coefficients. Almost any decent modern vehicle dynamics book will have a chapter or more devoted to the subject. Look at offerings from Carroll Smith and Milliken for race car focused discussion. Milliken is the much more technical of the two.

Basically, the issue of "driveability" involves much more than rubber compound alone. Everything from the tire width, sidewall profile, carcass construction, wheel diameter, wheel width, and of course tire compound will affect driveability.

For learning to control a car at its limits, I would think a tire with a low cornering stiffness (makes grip at high slip angles) and one that makes near peak grip over a broad range of slip angles would be best. This points towards a relatively narrow tire with soft carcass/sidewall construction, on a relatively narrow wheel. I don't think this necessarily excludes r-compound rubber, rather that tires using r-compounds typically do not fit the rest of the description.

Alternatively, the approach taken in Karting (very high cornering stiffness and very narrow 'optimal' slip angle range) to learn how to control a car seems to have worked well for most F1 drivers.

Food for thought.

And back on topic: my advice would be to get a set of star specs, RS3's, XS's, or similar and spend the rest of your money on registration fees and consumables for track days.
__________________
1996 328is Track Toy
2005 RSX Daily Driver


My Youtube Channel
Aero is offline   Reply With Quote
Old 04-03-2012, 05:56 PM   #37
Dinanstu
3rd Gear Member
 
Join Date: Dec 2011
Location: Toronto, Canada
Posts: 315
Ya, thats what I meant....
Dinanstu is offline   Reply With Quote
Old 04-04-2012, 07:15 AM   #38
dcramer
5th Gear Member
 
Join Date: Nov 2010
Location: Orangeville
Posts: 1,103
Quote:
Originally Posted by Aero View Post
The way pneumatic tires generate grip is much more complicated than the Coulomb or "dry" friction model, which involves static and kinetic friction coefficients. Almost any decent modern vehicle dynamics book will have a chapter or more devoted to the subject. Look at offerings from Carroll Smith and Milliken for race car focused discussion. Milliken is the much more technical of the two.
So which book did you prefer. Milliken's book is considerably more expensive.

Would you recommend one over the other ?

Dave
dcramer is offline   Reply With Quote
Old 04-04-2012, 11:03 AM   #39
SiR
Vtec just kicked in
 
Join Date: Apr 2002
Location: TO
Posts: 2,722
milliken book is excellent.

Doesnt hurt to have both if you are into that sort of thing.
__________________
-||Old Crayons||-
SiR is offline   Reply With Quote
Old 04-04-2012, 02:46 PM   #40
Aero
2nd Gear Member
 
Aero's Avatar
 
Join Date: Feb 2011
Location: Ottawa
Posts: 69
It's tough to recommend one over the other. The authors have very different style.

Smith is much less technical/mathematical and tends to speak from his wealth of experience. Tune to Win is a great book for someone who may not be an engineer, but still wants to learn a bit about vehicle dynamics and car setup.

Race Car Vehicle Dynamics by Milliken is the bible of, well, race car vehicle dynamics. It's much more technical, and is presented with an engineering audience in mind. That said, it is much more thorough and comprehensive. I like it since it presents the fundamental dynamics of the various vehicle systems and builds the analysis from there to arrive at meaningfull conclusions.

So, it really depends what you want to get out of the read. Yup, a typical "It depends" answer from an engineer.
__________________
1996 328is Track Toy
2005 RSX Daily Driver


My Youtube Channel
Aero is offline   Reply With Quote
Old 04-25-2012, 08:25 PM   #41
E30S54
Banned
 
Join Date: Dec 2011
Location: Canada
Posts: 27
n54
E30S54 is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 02:59 AM.


Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.