Comin' in hot!

[hotrodsurplus]

...increasing the tire's slip angle invertedly decreases the rim's fractional width ratio to the bead of the tire versus the swept area of the brake pad caliper shoe.

You're just going off on a tangent (get it? the tangent across the tire in a slip angle? Nevermind. It wasn't that funny anyway).

This then transmits the inertia's momentum to the backbone unibody structure of the front leaf torsion beam and affects the tire's contact patch with the road surface, causing further loss of gription.

Oh now you're just being oblique. You can be so obtuse at times. 

As you can now see, the simple act of discussing reduced tire pressures affects the entire characteristic of the car's handling, and most importantly that the keeping of ... an amphibious mammal for ... domestic ... yeah, that ain't legal, either.

bwaaahaahaahaa!

[mg]

fyi...less air not always better.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=2

The next test was run on our test course to confirm the influence of tire pressure on the tire's performance at its limit. While the drivers thought that the properly inflated tires provided responsiveness and predictable handling, they quickly realized that the same tires in an underinflated state left a lot to be desired. The underinflated tires required more steering input to initiate maneuvers and were slower to respond. The underinflated tires also felt out of sync during transitions; instead of moving in unison, the rear tires' reactions lagged behind the front tires, resulting in a detached sensation being transmitted to the drivers.

The underinflated tires delivered acceptable steady-state cornering force once they stabilized on our test track's skid pad, but the car was uncooperative anytime it was asked to change directions. It proved to be over 2 seconds slower around our test course (2 seconds represents about a 7% loss of handling performance).

In other words, the performance that tire manufacturers build in, low tire pressures can take away.

[TexasTom]

Just goes to show there's always a compromise, especially with these old cars. Lord knows they're not built to go 'round corners at speed!
Though somewhat futile, it would be interesting and maybe a little scary to take a 'Cal-Look' bug to a skidpad ... especially one with 135s!

Perhaps even arrange a comparison between say 135s, 145s, 175/65s ... even if they were all different cars.

I'll give Road&Track a call ...

TxT

[lawrence]

The most important sentences in that review: "Adjust your tire pressures as indicated on the vehicle tire placard or in the owner's manual. Check your inflation pressures at least once a month and before highway trips."

[hotrodsurplus]

fyi...less air not always better.

In other words, the performance that tire manufacturers build in, low tire pressures can take away.

Okay, I promise you that I'm not being a smart ass but it's sort of a given that an underinflated tire will not perform as well as a properly inflated tire will. I don't want to presume that you mean that we should overinflate our tires but I have to throw that out there so people don't get the idea that an overinflated tire will perform any better. Because no tire will achieve its best performance when overinflated.

A tire that maintains the most surface contact with the road achieves its greatest traction. But not even that can be taken at face value: a grossly underinflated tire (like a dragster slick) will achieve the most surface area...until it enters a corner. Laterally loading a grossly underinflated tire will cause the tire to deflect. The tread surface of a deflecting tire loses contact area with the road and therefore loses traction.

Conversely, a grossly overinflated tire will not achieve sufficient contact area with the road in any situation. You see physical evidence of that on 3/4-ton trucks. The vehicle manufacturer specifies only one tire pressure, the one that lets the tires bear the most weight. However, without the weight bearing upon them (empty truck) the tires will not comply sufficiently to maintain contact area. The middle of the tread wears prematurely which indicates that the tire does not achieve sufficient surface contact area.

I know that people have a hard time believing it but the seemingly low tire-pressure settings that Volkswagen recommended are within the range that lets the tires achieve the greatest contact area in most situations. Remember, tire pressure and load capacity are intimately related. Also remember that an ACVW is uncannily light--the front especially. So you can't draw any comparisons to the pressure settings that 'normal' cars have.

Sure, you can usually alter a vehicle's performance by manipulating its tire pressures but take care. For example, increasing front tire pressure makes a car turn in harder because it induces oversteer...which is a death sentence for a swing-axle car. And whatever you do, resist the urge to inflate tires to the maximum pressure indicated on the sidewall. That's merely the pressure required to make a tire bear its maximum load which is often greater than the weight of the entire vehicle.

[hotrodsurplus]

Though somewhat futile, it would be interesting and maybe a little scary to take a 'Cal-Look' bug to a skidpad ... especially one with 135s!

That would be so awesome. Most enthusiasts live in blissful ignorance as to how poorly cal-look cars really handle. Volkswagens are already prone to oversteer and swing-axle Volkswagens really prone to WICKED oversteer. Lowering the nose induces even more oversteer. Eliminating the front antiroll bar induces even more oversteer. The stiff torsion bars and dampers that some racers favor induce even more oversteer.

The tiny front tires induce understeer but as we've experienced that's at the expense of traction. The narrowed beams and spring-rate increase that result both induce understeer but certainly not enough to compensate for the stance and swingaxle issue.

I'm not knocking Cal Look. I just want people to understand the consequences of their actions. I giggle a little every time someone observes how well their cal look car handles.

[TexasTom]

This braking and handling situation, or to be more accurate: the LACK of Both ... is the exact reason I moved to the 175 & 185 width front tires on my car. I did not pick them to satisfy a 'look', but rather a need.
The sidewall height is the same as the skinnier tires in question here, but the handling and braking is Far Superior.
Granted, I do have a set of M&H front runners on my track wheels that do occasionally see some street miles, but those things brake and handle about as well as pencil erasers ... then again, I'm still running those 4-piston Brembos! LOL

I would HIGHLY recommend at least trying a set of 175s ... same size tire as on a new-style stock Mini when they came out (don't know if they're still the same or not). I know they do also make the 175s in a shorter 55% aspect ratio, but I just don't dig the look or the ride.

On the other side of the coin, When I used to autocross my '67 I was running 155s and 175s. Never had a problem with over or understeer and didn't use any aftermarket suspension "upgrades".
It's only problem was being overpowered!

TxT

[hotrodsurplus]

On the other side of the coin, When I used to autocross my '67 I was running 155s and 175s. Never had a problem with over or understeer and didn't use any aftermarket suspension "upgrades".
It's only problem was being overpowered!

I'm not knockin' it because in some cases oversteer is fun but your results suggest that your car did in fact suffer an oversteer problem. In that particular application it worked in your favor. Racecars usually work better with slight oversteer. They turn in harder. Cars that oversteer a lot tend to do better on tight AC tracks (remember when swingaxle Manx buggies slaughtered the competition in gymkhana?). It likely would've been a different story on a longer, faster track. You might've ended up looking from whence you came!

Most people usually translate excessive oversteer as 'too much power.' Oversteer is the result of the vehicle transferring too much weight to the outboard rear tire (jacking on a swingaxle) and causing the car to go 'loose' (another term for oversteer). That's why you can reduce oversteer by fitting a wider rear tire, bumping the rear pressure just a little bit to bear the greater lateral load, or as VW did in '67 widening the rear track. Lowering the rear and/or raising the nose so the car sat level or slightly nose high would've gone a long way to reducing the oversteer and converting more power to acceleration. Of course that wouldn't be very cal look but it underscores the mayhem that Cal Look creates.

I don't intend for this to get into a handling discussion but this information may help explain why these cars act this way when we do these things in the name of aesthetics. Hopefully reality will scare off some people so the scene doesn't get watered down with copycats who don't get it, so to speak. 

[TexasTom]

Although your discussion of the potential causes and effects are interesting, the problem in this case was the car simply had too much power and when abused, yes, it would oversteer. Did the same with 185s.
There's a line you must observe, cross it and you've gone too far. That's the difference between a good driver and a perhaps one that's fun to watch. I was neither, but did have an occasional glimpse of both

TxT

[wolfswest]

This braking and handling situation, or to be more accurate: the LACK of Both ... is the exact reason I moved to the 175 & 185 width front tires on my car. I did not pick them to satisfy a 'look', but rather a need.
The sidewall height is the same as the skinnier tires in question here, but the handling and braking is Far Superior.
Granted, I do have a set of M&H front runners on my track wheels that do occasionally see some street miles, but those things brake and handle about as well as pencil erasers ... then again, I'm still running those 4-piston Brembos! LOL

I would HIGHLY recommend at least trying a set of 175s ... same size tire as on a new-style stock Mini when they came out (don't know if they're still the same or not). I know they do also make the 175s in a shorter 55% aspect ratio, but I just don't dig the look or the ride.

On the other side of the coin, When I used to autocross my '67 I was running 155s and 175s. Never had a problem with over or understeer and didn't use any aftermarket suspension "upgrades".
It's only problem was being overpowered!

TxT

I've sent some pb's with Tom in the past and he really convinced me to try the 175/65's.  Like mentioned above: the sidewall height is exactly the same as a 145!!  Your car will become a REAL driver.  Try it, please!
I even like the look more, it's more in proportion now, when I look at photos of my previous "setup" : 135's and 205/70's it just looks silly and stupid.  Okay, start flaming now! 
My point is, it really creates a whole different car.  I'm a huuuuuge fan.