Spec Miata Community   
search | help | calendar | games | forum home

  next oldest topic   next newest topic
» Hello Spec Miata Community » Spec Miata Archives » Garage 2002-2009 » Camber, Toyos, & Slip Angle

 - Email this page to someone! | Subscribe To Topic  
Author Topic: Camber, Toyos, & Slip Angle
Little Bill Verified Driver
Member

Region: Colorado
Car #: 03
Year : 90
Posts: 411
Status: Offline
Icon 1 posted  Profile for Little Bill     Edit/Delete Post  Report this post to a Moderator

The camber rule thread is the reason I am starting this topic. There are alot of guys claming that you want as much camber as possible and I am kind of confused by this philosophy.

The Toyo's that we are required to run are a high slip angle tire right? To me this means that there is less mechnical grip or that the tire works better when slipping slightly, rather than being completely planted.

Does higher slip angle mean that the tire has less grip, and because of this less ability to roll over to the side wall? Because that has been my thought process. Am I wrong in my thinking?

To me more slip means I should go with as little camber as possible since the tire is sliding across its footprint, not gripping and rolling the camber into max footprint. Is this wrong?

I have paid closs attention to photographs of my car, grease pencil across the tire to check tire roll, pyrometer and wear patterns. I run 1.5 in the front and 1.8 to 2.0 in the rear and have found that I have good wear, braking, handeling, and temps.

The car is fast and predictable not to mention forgiving with no abnormal wear to the shoulder of the tire.

If Im not rolling over to the side wall and my temps are good it seems to reason that more camber equates to a smaller footprint, less grip and slower cornering speeds than my current setup.

Just to stop those that will say that im just not driving hard enough to see different results from my set up. I have won races with this set up against some stout competition. So I don't think saying the pace the car is being driven at is a valid point here. Although I know at times that can be a valid point.

All ideas and opinions are welcome. [thumbsup]

--------------------
Bill Hingston
SM#03
RM_Div

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

One thing that might tweak your thought process a little is that "slip angle" is not a measure of "slip". It might even be better called "grip angle" -- that is, it takes more grip to create more slip angle (for a given tire).

Slip angle is a function of deformation of the tire in the process of providing grip. In fact, when the tires finally break loose, the slip angle goes back to zero.

I admit your cambers sound low, particularly in front. The car must push terribly.

jim

--------------------
Just a clown

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

What Jim said, and think of slip angle as the difference between the direction the tread is pointed and the direction the wheel/rim is pointed. So again like Jim said, more grip generates higher slip angles, all else being equal, though I don't think it falls nearly to zero as you loose grip in a slide. Different tires work "best" at different slip angles.

All that said, your data surprises me. What ride height do you run? I think that could make a significant difference given how things change as you get beyond horizontal on the control arms and start using the bump stops.

Jay Lutz
Member

Region: Indy
Car #: 33
Year : 1994
Posts: 422
Status: Offline
Icon 1 posted  Profile for Jay Lutz     Edit/Delete Post  Report this post to a Moderator

Slip angle is the angle between the tire's actual direction of motion and the direction it would freely roll. When you are sliding sideways with the wheels pointing straight ahead the slip angle is 90 degrees....clearly a goofy by technically accurate case!

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

Jay, I don't think that's the accepted definition of slip angle for a tire (as opposed to the car), though I could be wrong. See my description above. Compare the plane of the wheel rim to the direction the tire tread is “pointing” at the contact patch. I don’t think the direction of travel, as such, is really part of the equation.

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

Jay's description works only if you think of the "tire's actual direction" as the direction the contact patch is rolling. No, slip angle doesn't go to 90 degrees when sliding sideways.

jim

--------------------
Just a clown

Dwayne Hoover Verified Driver Made Donation to Website
Veteran Member

Posts: 3138
Status: Offline
Icon 1 posted  Profile for Dwayne Hoover     Edit/Delete Post  Report this post to a Moderator

You're both right. Jay described vehicle slip angle and Steve described tire slip angle. As for "accepted definitions", the geeks that breathe it every day will *probably* call it "alpha" (Steve's def )or "beta" (Jay's def) to avoid the SIX posts you guys just spent arguing about "slip angle". [Roll Eyes]

Thoughts:
1. Caster changes camber as a function of steer angle. Unless you go through corners with the steering wheel straight, static camber is only 1/3 the story. (Bushing compliance etc. could be another 1/3 of the story).

2. Some tracks are camber hungry, some aren't. Some tracks are bumpy and some aren't. Stock radiators with no sealing work great in my area, how are they in Colorado? [Wink] What is the reluctance to giving everyone more camber range? Does anyone in SRF ever argue about whether they can get enough camber?

3. http://www.toyo.com.au/Pit%20Lane.htm
"Toyo motor sport radials will provide optimum cornering grip with camber settings between negative 3 and 6 degrees on steer axles"

Are they full of crap? Maybe.

4. RWD BMW on Toyo RA-1s <a http://www.turnermotorsport.com/html/raceimages/seb_06/aub_seb_start2_lg.jpg

Does this vehicle have any relevance to a Miata whatsoever. Who knows.

5. Does "optimum grip" mean fastest lap time? Camber can hurt braking and acceleration. There is no $4 trophy for most uniform tire wear or best pyro readings. The stopwatch and the final results are all that matter.

Wouldn't it be nice if you could crawl under your car, turn the bolt, and get -3.5 if you wanted? No prying, no sitting on the bumpstops, no sorting through parts, no blueprinting, in short no hassle at all?

--------------------
Visit the Midland City Arts Festival!

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

Hey Screw-Drive, can you describe the factors that make a track "camber-hungry" or not? Not picking a fight, interested in improving. And while the stopwatch may be the bottom line, it's tough to tune camber at each wheel at each track, purely by the watch. So what indicators do you use?

jim

PS: thanks for illuminating Jay's comments. "Tires" was the only context I was thinking about.

--------------------
Just a clown

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

1. Agreed. We talk about camber based on wheels straight ahead but also measure it at 20 degrees each direction as we check caster.

2. Agreed, but on the few tracks we've run I haven't found a huge variance. Would you say the biggest variable is the steering angle and duration required for the corners?

3. They are not full of crap IMO, and the Hoosiers liked even more camber.

4. Relevant enough to consider as a data point.

5. Agreed. We certainly have crossed the "optimum" point where the cost in stopping probably exceeded the gain in cornering, which is why we set caster to maximize front camber with the wheels turned. We don’t have enough power to have the equivalent problem at the rear under acceleration.

YES!!! It would be nice to focus on setup and driving rather than finding ways to get more camber.

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Jim Boemler:
...PS: thanks for illuminating Jay's comments. "Tires" was the only context I was thinking about.

Funny, I though I had already covered that. [Wink]

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

You did, Steve. And I'd know that, if I ever read your posts. [Razz]

jim

--------------------
Just a clown

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by MBennett:
You're both right. Jay described vehicle slip angle and Steve described tire slip angle. As for "accepted definitions", the geeks that breathe it every day will *probably* call it "alpha" (Steve's def )or "beta" (Jay's def) to avoid the SIX posts you guys just spent arguing about "slip angle". [Roll Eyes]

Thoughts:
1. Caster changes camber as a function of steer angle. Unless you go through corners with the steering wheel straight, static camber is only 1/3 the story. (Bushing compliance etc. could be another 1/3 of the story).

2. Some tracks are camber hungry, some aren't. Some tracks are bumpy and some aren't. Stock radiators with no sealing work great in my area, how are they in Colorado? [Wink] What is the reluctance to giving everyone more camber range? Does anyone in SRF ever argue about whether they can get enough camber?

3. <a href="http://www.toyo.com.au/Pit%20Lane.htm" target="_blank" style="text-decoration: underline">http://www.toyo.com.au/Pit%20Lane.htm</a>
"Toyo motor sport radials will provide optimum cornering grip with camber settings between negative 3 and 6 degrees on steer axles"

Are they full of crap? Maybe.

4. RWD BMW on Toyo RA-1s <a <a href="http://www.turnermotorsport.com/html/raceimages/seb_06/aub_seb_start2_lg.jpg" target="_blank" style="text-decoration: underline">http://www.turnermotorsport.com/html/raceimages/seb_06/aub_seb_start2_lg.jpg</a>

Does this vehicle have any relevance to a Miata whatsoever. Who knows.

5. Does "optimum grip" mean fastest lap time? Camber can hurt braking and acceleration. There is no $4 trophy for most uniform tire wear or best pyro readings. The stopwatch and the final results are all that matter.

Wouldn't it be nice if you could crawl under your car, turn the bolt, and get -3.5 if you wanted? No prying, no sitting on the bumpstops, no sorting through parts, no blueprinting, in short no hassle at all?

Wow...OK who took Bennett's login while he's on vacation? That post has been up 5 hrs and it hasn't been deleted yet.

OK something else you guys haven't mentioned...rolling resistance. When highly cambered, the Toyo RA1 seems to deform quite a bit on the contact side. I'm guessing by the stopwatch only, SM might be best compromised while cars with traction limit or other limit other than HP might benefit more from the extra camber. Just guessing here but whomever is impersonation MB...please comment on this please. [Smile]

Also....the GTR (yep the race sim) manual mentions optiming spread of something like 12-15 between center and both edges, with the hottest being on the outside, coolest on the inside. Care to comment on that?

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Antonio Garza:
... Also....the GTR (yep the race sim) manual mentions optiming spread of something like 12-15 between center and both edges, with the hottest being on the outside, coolest on the inside. Care to comment on that?

While we're waiting for Bennett, I think it depends a bunch on the track, including how long the straights are compared to the time spent in turns, and whether you can check temps immediately after a turn.

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

So if you could come up with a 3 spot instant IR reading while driving...you'd want those to be equal then (for a given turn)?

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Little Bill Verified Driver
Member

Region: Colorado
Car #: 03
Year : 90
Posts: 411
Status: Offline
Icon 1 posted  Profile for Little Bill     Edit/Delete Post  Report this post to a Moderator

Jim I run straight up in the front for toe and an 1/8 total on the rear, caster is 5 degrees. The car is planted and doesn't push.

Ive beaten the likes of Rivera, Boileau, and Ott with this setup.

Maybe this is what works best for my driving style; maybe it's just what this chassis likes right now? Im kicking around some different ideas, I plan on making a radical change before my test test day to see how I like it.

I can't explain why the car is fast with these numbers. Most everyone that looks at them thinks they shouldn't work, but they do.

--------------------
Bill Hingston
SM#03
RM_Div

TillerTech
Member

Region: SoPac
Car #: na
Year : 89
Posts: 441
Status: Offline
Icon 1 posted  Profile for TillerTech     Edit/Delete Post  Report this post to a Moderator

I used to think that I had a pretty good idea what a race tire is actually doing. That was until I picked up Rowley's Race Car Engineering book. The first 4 chapters are all about tires, only. Contact patch and the effects of suspension settings. This book is not full of "if this, then that" it is written for the engineer who needs to understand the dynamics. Also included is a demo version of the WinGeo3 software and some usefull excel spread sheets.

Oh, and by the way, it has been done. 3 point IR temps on the tires while driving with DA.

J

--------------------
Miata Race glass and CF from Legacy Molds. 4 1/2# CF Hood
http://www.jnent.net

B Wilson Verified Driver Series Champ
Gold Member

Region: Oregon
Car #: 68
Year : 91
Posts: 2359
Status: Offline
Icon 1 posted  Profile for B Wilson   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Bill,

What caster settings and hot tire pressures do you run? I would guess you run max caster and the top end of hot pressures to make that setup work for you.

-Bruce

--------------------
Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

Little Bill Verified Driver
Member

Region: Colorado
Car #: 03
Year : 90
Posts: 411
Status: Offline
Icon 1 posted  Profile for Little Bill     Edit/Delete Post  Report this post to a Moderator

Steve,

I will have to measure that to tell you.

I can tell you that I don't get on the bump stops. I am of the opinion that the shocks are on the car for a reason. If Im on the stops in a corner I have found that the car seems unsettled. Why take a perfectly good shock out of the equation when going through a corner?

--------------------
Bill Hingston
SM#03
RM_Div

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

When I used to race RC cars, we used to put less camber when we had less grip. Think about that one for a little bit....

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

TC Motorsports Verified Driver
www.tcmotorsports.net

Posts: 796
Status: Offline
Icon 1 posted  Profile for TC Motorsports   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Antonio is on it. If a track has poor grip, the tires will roll less, so you need less camber. The main reason for adding camber is so when the tire deflects (rolls), you are keeping the tire patch on the ground.

Camber selection is also influenced by tire pressure. Some guys like to run a lot of pressure, some like to run less. There is no magic pressure that works for everyone... same with camber.

With that, if our cars where 800 lbs lighter, would ya'll still want to run 3+ degrees camber?

--------------------
Carlo Sparacio
TC Motorsports, LLC
www.tcmotorsports.net

B Wilson Verified Driver Series Champ
Gold Member

Region: Oregon
Car #: 68
Year : 91
Posts: 2359
Status: Offline
Icon 1 posted  Profile for B Wilson   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Or what if we run 25 lbs heavier [Smile]

interesting what the Aussie link says about hot pressures for our weights. I'm guessing those pressures are assuming you have have unlimitted camber addjustments.

-Bruce

--------------------
Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

Little Bill Verified Driver
Member

Region: Colorado
Car #: 03
Year : 90
Posts: 411
Status: Offline
Icon 1 posted  Profile for Little Bill     Edit/Delete Post  Report this post to a Moderator

Bruce,

As much caster as posssible, I went out to the glove box of the race car (that sounds kind of funny) and looked at my setup sheets. Last race front was at zero toe, 1.5 camber, 5.1 caster. Rear was at 1/8th total toe (1/16th a side) and 1.9 for camber.

Car was within .5 of track record that weekend.

--------------------
Bill Hingston
SM#03
RM_Div

Rich Verified Driver
Oh, that's where that is.

Region: STL
Car #: 35
Year : #795 SRF
Posts: 1209
Status: Offline
Icon 1 posted  Profile for Rich   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Every track I ran on last year needed at least 2 degrees until I went to HPT for the first time. The first time I went to HPT after the repave was a pretty low-grip, high temperature situation. I was too lazy to do it but I bet a little less camber would have been faster there from my tire wear and temp data.

--------------------
Rich Wiese

Spec Wrecker Ford

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by TC Motorsports:
Antonio is on it. If a track has poor grip, the tires will roll less, so you need less camber. The main reason for adding camber is so when the tire deflects (rolls), you are keeping the tire patch on the ground....

Absolutely.

Rich, I'm surprised to hear that HPT needs less. I haven't driven there but thought the relatively slow tight turns would dictate more. Perhaps low overall grip at the time was enough to offset that.

Rich Verified Driver
Oh, that's where that is.

Region: STL
Car #: 35
Year : #795 SRF
Posts: 1209
Status: Offline
Icon 1 posted  Profile for Rich   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Steve Scheifler:
quote:
Originally posted by TC Motorsports:
Antonio is on it. If a track has poor grip, the tires will roll less, so you need less camber. The main reason for adding camber is so when the tire deflects (rolls), you are keeping the tire patch on the ground....

Absolutely.

Rich, I'm surprised to hear that HPT needs less. I haven't driven there but thought the relatively slow tight turns would dictate more. Perhaps low overall grip at the time was enough to offset that.

That's what I think it was, since the tight corners certainly ask a lot of the tires, but caster plays a bigger role in the tight ones too since the steering angle is likely bigger (no data to support this of course). If I could have gotten another degree in the right front and cut everything else to 2 I would have but I can barely get 2 degrees on the right front. Crap, I've revealed my kryptonite. Hey everybody, just wait until 3 or 6 to pass me next year at the Runoffs, I'll have no recourse because I can't get any right front camber! Jam your nose in there and you'll be home free. Oh well, I guess I'll wait for the clockwise track to be the host again in about 20 years...

--------------------
Rich Wiese

Spec Wrecker Ford

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

Rich, change the RFL control arm and quick making excuses. [Wink] We have spares if you want to see if it makes a difference.

Rich Verified Driver
Oh, that's where that is.

Region: STL
Car #: 35
Year : #795 SRF
Posts: 1209
Status: Offline
Icon 1 posted  Profile for Rich   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Steve Scheifler:
Rich, change the RFL control arm and quick making excuses. [Wink] We have spares if you want to see if it makes a difference.

I put new ones (the beefy superceded part numbers) on last year! I think the subframe or upright is the culprit at this point but I'm way too lazy. Then again, Burkett seems like a hard worker...

--------------------
Rich Wiese

Spec Wrecker Ford

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

Maybe you should stop running into stuff. [Wink]

Rich Verified Driver
Oh, that's where that is.

Region: STL
Car #: 35
Year : #795 SRF
Posts: 1209
Status: Offline
Icon 1 posted  Profile for Rich   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Stuff needs to stop running in to me! Everything last season was on the left side anyway. I think I'll just adjust the "tolerance" on the upper control arm.

--------------------
Rich Wiese

Spec Wrecker Ford

   

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic | Subscribe To Topic
Hop To: