Slow Speed Surging

[houndman]

I call it Chugging, but at low speeds the car isn't smooth. I read
that the variable valve timing could be the cause, or the drive by
wire throttle. Seems like being in a lower gear which would get the
revs up might help, but haven't tried it yet. I've seen the revs go up
right after stoping, which looks like the car has a mind of its own.((

VF

 

[Carl 1 Lucky Texan]

I call it Chugging, but at low speeds the car isn't smooth. I read
that the variable valve timing could be the cause, or the drive by
wire throttle. Seems like being in a lower gear which would get the
revs up might help, but haven't tried it yet. I've seen the revs go up
right after stoping, which looks like the car has a mind of its own.((

VF

TRy sliding the seat one notch back. It might help. Took me a while to
get the right seat position to be able to get the clutch to the floor
without being 'early' on the release. I dunno.

While i don't quite rev the sube like I did my '81 civic wagon, I
frequently got to 4 k in everyday driving and will go to redline without
hesitaion if I need (or 'want') to.

One problem carmakers have nowadays is marketing. We seem to be stuck
with 0-60mph as a 'benchmark' and sometimes an engine/tranny/final ratio
is tailored to get that number low - regardless if a different
combination would be easier to actually drive! Try using first to near
redline, then a little lower rpm shift in second (second is 'TALL' in
my WRX - though my old 69 Datsun 2000 was worse. I was doing 70 at the
top of 2nd in it!) even lower in third - like that. Sometimes I will use
second to 90% of intended cruising speed then skip to 4th or even 5th.
You know - just depends on the road and your 'style' I guess.

My wrx has plenty of torque but the curve is 'peaky' and comes on quick.
So I will accelerate using a high enough rpm to use that torque most of
the time. Lugging an engine can be bad I guess (overheating, carbon
buildup ????) and lower gears help it work easy.

Carl

 

[houndman]

TRy sliding the seat one notch back. It might help. Took me a while to
get the right seat position to be able to get the clutch to the floor
without being 'early' on the release. I dunno.

While i don't quite rev the sube like I did my '81 civic wagon, I
frequently got to 4 k in everyday driving and will go to redline without
hesitaion if I need (or 'want') to.

One problem carmakers have nowadays is marketing. We seem to be stuck
with 0-60mph as a 'benchmark' and sometimes an engine/tranny/final ratio
is tailored to get that number low - regardless if a different
combination would be easier to actually drive! Try using first to near
redline, then a little lower rpm shift in second (second is 'TALL' in
my WRX - though my old 69 Datsun 2000 was worse. I was doing 70 at the
top of 2nd in it!) even lower in third - like that. Sometimes I will use
second to 90% of intended cruising speed then skip to 4th or even 5th.
You know - just depends on the road and your 'style' I guess.

My wrx has plenty of torque but the curve is 'peaky' and comes on quick.
So I will accelerate using a high enough rpm to use that torque most of
the time. Lugging an engine can be bad I guess (overheating, carbon
buildup ????) and lower gears help it work easy.

Carl

I'm trying a lot of different things, like seating position. The
clutch grabs a bit low for comfort. Feel like I'm gona grind the gears
not disengaging it completely, but haven't yet. Have to get my left
leg to hang in the air more, to release the clutch smoothly. Guess
I'll get it right soon. I'm practicing enough.

Trying not to rev it too high just yet with only 200mi on it, though
I probably have.

Playing with tire pressures, and getting the ride better. It was
bumpy feeling. I dropped them all down to the high 20's, and the
fronts looked too low. I wound up pumping the fronts up to 34, and
dropped the rears to 24, and they Look right, and feel a Lot better.
I'm figuring the weight distribution of the car is about 60/40 and a
rough calc looks like those pressures are the same.

It's taking more time than I imagined, but things are coming together

VF

 

[Carl 1 Lucky Texan]

I'm trying a lot of different things, like seating position. The
clutch grabs a bit low for comfort. Feel like I'm gona grind the gears
not disengaging it completely, but haven't yet. Have to get my left
leg to hang in the air more, to release the clutch smoothly. Guess
I'll get it right soon. I'm practicing enough.

Trying not to rev it too high just yet with only 200mi on it, though
I probably have.

Playing with tire pressures, and getting the ride better. It was
bumpy feeling. I dropped them all down to the high 20's, and the
fronts looked too low. I wound up pumping the fronts up to 34, and
dropped the rears to 24, and they Look right, and feel a Lot better.
I'm figuring the weight distribution of the car is about 60/40 and a
rough calc looks like those pressures are the same.

It's taking more time than I imagined, but things are coming together

VF

Don't get TOO far away from the 'ratio' of F/R pressure as recommended
by Subaru - could lead to center diff problems.

Carl

 

[David]

I call it Chugging, but at low speeds the car isn't smooth. I read
that the variable valve timing could be the cause, or the drive by
wire throttle. Seems like being in a lower gear which would get the
revs up might help, but haven't tried it yet. I've seen the revs go up
right after stoping, which looks like the car has a mind of its own.((

VF

The valves don't change until you are cruising. If you are engine
braking and it surges add a little mechanical brake pressure, that
should smooth it out. The differentials like some steady bias.

 

[houndman]

The valves don't change until you are cruising. If you are engine
braking and it surges add a little mechanical brake pressure, that
should smooth it out. The differentials like some steady bias.

It Does feel like it or some of it is in the drive train. I feel a
little vibration when the clutch starts to grab mainly when just
letting it start to grab.
What about a Little hand brake applied?

Changing the tire pressures, lowering the rears seems to have
helped. Maybe it causes a bit of friction that smoothes or drags.

VF

 

[houndman]

Don't get TOO far away from the 'ratio' of F/R pressure as recommended
by Subaru - could lead to center diff problems.

Carl

OK, but would lowering pressure change the diameter of the tire and
distance it will cover? Seems like would have to go really low to do
that.

IF both Fr and Rr tires have the same shape/bulge, wouldn't they
cover the same ground, not making the center diff work like one axel
was slipping? I Think that is what you are talking about, like the
center diff is working all the time, and can burn it up or damage it.

What have you heard? I have heard that different sized tires Fr/Rr
will make the diff constantly work and damage it, like new and worn
tires on a Sube.

VF

 

[houndman]

It's symmetrical all-wheel drive, especially in the manual
transmission version. All tires should be within a pound of each
other.- Hide quoted text -

- Show quoted text -

sounds like I'm gona have a problem then, and I have the base model,
because the WRX suspension and or tires beat me up.

Why wouldn't the inflated shape of the tires being equal make them
cover the same distance in a rotation?

VF

 

[David]

It Does feel like it or some of it is in the drive train. I feel a
little vibration when the clutch starts to grab mainly when just
letting it start to grab.
What about a Little hand brake applied?

Changing the tire pressures, lowering the rears seems to have
helped. Maybe it causes a bit of friction that smoothes or drags.

VF

Either gently apply foot braking or shift to the next higher gear.
Don't worry about the automatic stuff doing its thing.

 

[David]

It Does feel like it or some of it is in the drive train. I feel a
little vibration when the clutch starts to grab mainly when just
letting it start to grab.
What about a Little hand brake applied?

Changing the tire pressures, lowering the rears seems to have
helped. Maybe it causes a bit of friction that smoothes or drags.

VF

It's symmetrical all-wheel drive, especially in the manual
transmission version. All tires should be within a pound of each
other.

 

[houndman]

It's symmetrical all-wheel drive, especially in the manual
transmission version. All tires should be within a pound of each
other.- Hide quoted text -

- Show quoted text -

the manual lists 1 lb difference in the 215 17" tires, 3 in the 16"
ones, and 6 in the 225 17"'s

VF.

 

[Carl 1 Lucky Texan]

OK, but would lowering pressure change the diameter of the tire and
distance it will cover? Seems like would have to go really low to do
that.

IF both Fr and Rr tires have the same shape/bulge, wouldn't they
cover the same ground, not making the center diff work like one axel
was slipping? I Think that is what you are talking about, like the
center diff is working all the time, and can burn it up or damage it.

What have you heard? I have heard that different sized tires Fr/Rr
will make the diff constantly work and damage it, like new and worn
tires on a Sube.

VF

There was a 'heated' discussion at www.ultimatesubaru.org about this
issue. The distance the axle hub is from the ground determines the
radius, regardless of 'bulge size' or tire wear. Since the fron to of
the car is heavier (as you say, 60/40 or 55/45 distribution) the tires
get more pressure to maintain the correct 'contact patch'. In my
experience, maunfacturers tend to suggest somewhat too low tire
pressures, this may have been more prevalent in the past. If the
front/rear pressure difference is 2 pounds, I doubt going up 2 or down 2
front and rear is gonna be a problem. But your post seemed to show a
difference of 10 lbs which just seemed a little excessive. Of course. if
the rear of a wagon is heavily loaded I'd feel boosting the pressure
would be a good idea. Also, too low pressures can lead to the bead
rolling off the rim in high speed cornering too. That could lead to
having a 'bad day'.

Carl

 

[houndman]

There was a 'heated' discussion atwww.ultimatesubaru.orgabout this
issue. The distance the axle hub is from the ground determines the
radius, regardless of 'bulge size' or tire wear. Since the fron to of
the car is heavier (as you say, 60/40 or 55/45 distribution) the tires
get more pressure to maintain the correct 'contact patch'. In my
experience, maunfacturers tend to suggest somewhat too low tire
pressures, this may have been more prevalent in the past. If the
front/rear pressure difference is 2 pounds, I doubt going up 2 or down 2
front and rear is gonna be a problem. But your post seemed to show a
difference of 10 lbs which just seemed a little excessive. Of course. if
the rear of a wagon is heavily loaded I'd feel boosting the pressure
would be a good idea. Also, too low pressures can lead to the bead
rolling off the rim in high speed cornering too. That could lead to
having a 'bad day'.

Carl

The axle hub distance to the ground determining the radius makes
sense. My idea and liking is to make the contact patch the same. I
like a little bulge in the sidewalls, but not so much it looks like it
is hanging over the side of the tread. When carrying a heavy load, the
pressures would be increased. I always looked at the load capacity of
the tire, and liked a nice margin where the tire was rated for more
than it was holding up. I didn't think cars that came through with a
tire sizes that were less than the car weight was very safe. Figure
the tire is being overly stressed in normal driving. Always liked
oversized tires.

Will have to give the tires a good look. Maybe after driving it
after the tires will look different, but wouldn't think so. I drove
home after changing the pressures, and looking out the window at them,
they look equal.

VF

 

[houndman]

I have 16s and my manual says 28 front 29 rear. I think it's
important to have equal rolling resistance on hard pavement.

Give the car a chance. My Forester has saved my life a few times
thanks to its incredible handling characteristics. The vehicle
behaves as though it's on tracks.- Hide quoted text -

- Show quoted text -

If the tire pressures were critical, I can't see how they can be so
different on different tire sizes or cars. The same tire shape from
inflation should have the same rolling resistance.

I'd like to have optimum handling, comfort, and tire wear. They
should all be related. I passed on getting a WRX because the ride was
too stiff, and the 2.5i power seemed adequite at least for now. With
the factory settinge the ride was unbearable on a certain road around
a park I frequent. Every ripple in the road even where it looked
smooth was felt, and made the car move up and down. Reminded me what a
nephew said his wife said about the 5sp car he bought, she said it
made her feel like she was going to upchuck, and wouldn't ride in it,
so he sold it. I figured the motions when shifting were the reason,
since that's what he implied, but I wonder if it was tire pressures or
a combo?

If the settings were mandatory, I wouldn't enjoy going to the park,
and having to drive the 2 1/2 mi one way road around it, inside it,
and only use my other car. The ride wasn't what I'd call comfortable
on many other roads. If it was the car might be exceptional. I perfer
a firm ride, and always bought cars with heavy duty suspensions, since
prefer feeling a bump and then it is over, as opposed to wallowing and
jiggling. What I was getting was, feeling the bumps, and jiggling on
smooth roads. It felt like the tires were lumpy.

VF

 

[David]

the manual lists 1 lb difference in the 215 17" tires, 3 in the 16"
ones, and 6 in the 225 17"'s

VF.

I have 16s and my manual says 28 front 29 rear. I think it's
important to have equal rolling resistance on hard pavement.

Give the car a chance. My Forester has saved my life a few times
thanks to its incredible handling characteristics. The vehicle
behaves as though it's on tracks.

 

[Bugalugs]

If the tire pressures were critical, I can't see how they can be so
different on different tire sizes or cars. The same tire shape from
inflation should have the same rolling resistance.

I'd like to have optimum handling, comfort, and tire wear. They
should all be related. I passed on getting a WRX because the ride was
too stiff, and the 2.5i power seemed adequite at least for now. With
the factory settinge the ride was unbearable on a certain road around
a park I frequent. Every ripple in the road even where it looked
smooth was felt, and made the car move up and down. Reminded me what a
nephew said his wife said about the 5sp car he bought, she said it
made her feel like she was going to upchuck, and wouldn't ride in it,
so he sold it. I figured the motions when shifting were the reason,
since that's what he implied, but I wonder if it was tire pressures or
a combo?

If the settings were mandatory, I wouldn't enjoy going to the park,
and having to drive the 2 1/2 mi one way road around it, inside it,
and only use my other car. The ride wasn't what I'd call comfortable
on many other roads. If it was the car might be exceptional. I perfer
a firm ride, and always bought cars with heavy duty suspensions, since
prefer feeling a bump and then it is over, as opposed to wallowing and
jiggling. What I was getting was, feeling the bumps, and jiggling on
smooth roads. It felt like the tires were lumpy.

VF

You aren't related to Amanda ....Are you????

 

[David]

The ride wasn't what I'd call comfortable
on many other roads. If it was the car might be exceptional. I perfer
a firm ride, and always bought cars with heavy duty suspensions, since
prefer feeling a bump and then it is over, as opposed to wallowing and
jiggling. What I was getting was, feeling the bumps, and jiggling on
smooth roads. It felt like the tires were lumpy.

VF

I find that very hard to believe. My suspension is exceptional in
that it is firmly planted on the road while being smooth to the
occupants.

 

[houndman]

I find that very hard to believe. My suspension is exceptional in
that it is firmly planted on the road while being smooth to the
occupants.

maybe i got an STI suspension in the car. Was driving on the
interstate today and one section that looked like smooth concrete
though the color had shadings, was causing a Clicking sound. Maybe I
have stuck shocks.

VF

 

[houndman]

There was a 'heated' discussion atwww.ultimatesubaru.orgabout this
issue. The distance the axle hub is from the ground determines the
radius, regardless of 'bulge size' or tire wear. Since the fron to of
the car is heavier (as you say, 60/40 or 55/45 distribution) the tires
get more pressure to maintain the correct 'contact patch'. In my
experience, maunfacturers tend to suggest somewhat too low tire
pressures, this may have been more prevalent in the past. If the
front/rear pressure difference is 2 pounds, I doubt going up 2 or down 2
front and rear is gonna be a problem. But your post seemed to show a
difference of 10 lbs which just seemed a little excessive. Of course. if
the rear of a wagon is heavily loaded I'd feel boosting the pressure
would be a good idea. Also, too low pressures can lead to the bead
rolling off the rim in high speed cornering too. That could lead to
having a 'bad day'.

Carl

I measured the distance from the bottom of the rims to the ground,
and the rears with the lower tire pressure were 1/4" higher than the
fronts. One concrete surface on the interstate created a Clicking
sound. It looked smoothe, but had shadings, so don't know what it
feels like.

 

[Carl 1 Lucky Texan]

I measured the distance from the bottom of the rims to the ground,
and the rears with the lower tire pressure were 1/4" higher than the
fronts. One concrete surface on the interstate created a Clicking
sound. It looked smoothe, but had shadings, so don't know what it
feels like.

Subaru wants the CIRCUMFERENCE of each tire to be within 1/4" of each
other. I THINK, by having those tires so much less inflated than the the
others, the center diff will detect it as slippage and may engage the
50/50 lock on dry pavement. That will lead to stress on the drivetrain
(since you are not actually on a slippery surface) possibly causing
damage. You should try to stay near the 'ratio' that is indicated in the
manual or on the door jamb. If you must, lower the pressure in all 4, or
raise the pressure in all 4(not above the max on the sidewall), but stay
near the 'differential' recommended.

You might get away with 10 lbs. difference for a short while - but
eventually the center diff or other component will fail.

Carl