# [EVDL] What a difference tire pressure makes!



## EVDL List (Jul 27, 2007)

I was getting more and more concerned about what 
seemed to be a dropping range on my truck, no matter
what I did the consumption did not want to go down
much and I could barely maintain 55 on the freeway.
I had inflated the tires a month ago when I started
driving this truck but at that time they were warm
so I had slightly over-inflated them (35 PSI max
cold pressure so I had put a little over 40 in them
as Light Truck tires are required by law to allow
at least 5 PSI over max sidewall cold pressure)
and when I checked both rear tires now they were 
indeed still close to 40 (I did put a few extra PSI 
in them anyway) but the front tires had lost more, 
one was down close to only 25 PSI, so I pumped all 
of them to around 42 (this EV is never going to 
heat up its tires like an ICE truck that can do 
max speed for hours at a time).

Now it easily maintains 55 on the freeway except on
one long overpass and I arrived at work with the
consumption meter showing 63% SoC while earlier it
usually showed between 55 and 58% depending on the
number of times I would have to stop for a light.

The truck is still taking too much power to drive a
constant 55, at least to my liking the 200A draw at
110V or approx 22kW is still relatively high when
compared to the 15kW that I would like to see for
this type of trip. But at least the 400Wh per mile
is more acceptable than the 500+Wh that I saw earlier
when running in lower gear (more loss in the automatic)
and too low tire pressure.

Eventually I may bring the tire pressure up to 50 PSI
cold so it is equal to the pressure in my S10
(which also had tires that had max 35 on the sidewall
but needed 50 to avoid rolling over the tire thread
and drive on the sidewall in a quick turn).

Then I may need to see if I can do something about the
tranny - both the occasional leak from the fill tube
as well as putting synthetic oil in to see if that
will further reduce the losses.
And of course, avoid the more than 2" overfill that
my transmission has today. That can't be good for
efficiency either.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

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## EVDL List (Jul 27, 2007)

It's worth noting that the range in coefficient of rolling resistance in
properly inflated passenger car tires goes from .006 to .014. That means
that some cause twice the drag of others. At 55, rr is still a fairly large
part of the total drag, although typically rolling and areo drag are apt to
cross over at about 40 mph or maybe a little lower on a boxy shape. 




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## EVDL List (Jul 27, 2007)

Hello Cor,

To maintain the lowest deflection resistance of the face of the tire, it is 
best to stay between 3/8 to 1/2 inch deflection of the side wall of the 
tire.

I learn this from master mechanics that work on long haul trucks and the 
following method of how to adjust the tires air pressure for the best 
performance.

You first weigh the front and rear axle of the vehicle. In my case I have 
about 2200 lbs on each wheel and tire on the rear and 1200 lbs on each wheel 
and tire on the front.

I use Michelin Low Rolling Resistance tires that are rated for 2200 lbs at 
50 psi which are mounted on 17 inch forge aluminum wheels that is also rated 
for 2200 lbs.

The face of the tire has 2 plies of polyester, 1 ply of steel and 1 ply of 
nylon which keeps the tire face very stiff and rounded. The side way is a 
very soft 2 ply polyester which picks up most of the deflection and does not 
transfer the to the face like the older tires did.

To adjust the tire air pressure, you first jack the tire off grade and air 
it up to the maximum PSI as listed on the side of the tire. Now we than 
measure the side wall width by lowing the tire until it just touches the 
floor.

Measure from the floor to the lower edge of the wheel rim. Lets say this 
reads 5 inches. Now we lower the vehicle until the entire weight of the 
vehicle is on grade. Lets say it reads 4.5 inches which will be ok for a 
0.5 inch side wall deflection.

For my rear tires, it becomes 50 psi at 2200 lbs for a 0.5 inch deflection. 
The same 2200 lb load rating at 50 psi tires are also on the front, but I 
have to reduce the air pressure to 35 lbs get a 0.5 inch side wall 
deflection for 1200 lb load.

This initial adjustments is normally done at about 70F. As it get warmer, 
the side wall deflection may decrease to about 3/8 in. which is still ok.

If you have more than 0.5 inch deflection, then the maximum load rating of 
the tire is not correct for the vehicle.

Using the correct tires and wheels made a big difference for me. The first 
tires that were use were all nylon and steel with a very stiff side wall 
which transmitted the side wall deflection to the face of the tire. As the 
temperature drop while the EV was setting outside, the face would develop as 
flat spot which took about two miles of driving to round them out.

With the older tires at very cold temperature, it would take between 4.5 to 
5 ah per mile. With the correct tires at the correct air pressure, this 
became 3.8 to 3.9 ah per mile. At 80F it became 3.3 to 3.5 ah per mile or 
about 380 wh/m.

Roland










----- Original Message ----- 
From: "Cor van de Water" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, June 28, 2012 2:03 PM
Subject: [EVDL] What a difference tire pressure makes!


> I was getting more and more concerned about what
> seemed to be a dropping range on my truck, no matter
> what I did the consumption did not want to go down
> much and I could barely maintain 55 on the freeway.
> I had inflated the tires a month ago when I started
> driving this truck but at that time they were warm
> so I had slightly over-inflated them (35 PSI max
> cold pressure so I had put a little over 40 in them
> as Light Truck tires are required by law to allow
> at least 5 PSI over max sidewall cold pressure)
> and when I checked both rear tires now they were
> indeed still close to 40 (I did put a few extra PSI
> in them anyway) but the front tires had lost more,
> one was down close to only 25 PSI, so I pumped all
> of them to around 42 (this EV is never going to
> heat up its tires like an ICE truck that can do
> max speed for hours at a time).
>
> Now it easily maintains 55 on the freeway except on
> one long overpass and I arrived at work with the
> consumption meter showing 63% SoC while earlier it
> usually showed between 55 and 58% depending on the
> number of times I would have to stop for a light.
>
> The truck is still taking too much power to drive a
> constant 55, at least to my liking the 200A draw at
> 110V or approx 22kW is still relatively high when
> compared to the 15kW that I would like to see for
> this type of trip. But at least the 400Wh per mile
> is more acceptable than the 500+Wh that I saw earlier
> when running in lower gear (more loss in the automatic)
> and too low tire pressure.
>
> Eventually I may bring the tire pressure up to 50 PSI
> cold so it is equal to the pressure in my S10
> (which also had tires that had max 35 on the sidewall
> but needed 50 to avoid rolling over the tire thread
> and drive on the sidewall in a quick turn).
>
> Then I may need to see if I can do something about the
> tranny - both the occasional leak from the fill tube
> as well as putting synthetic oil in to see if that
> will further reduce the losses.
> And of course, avoid the more than 2" overfill that
> my transmission has today. That can't be good for
> efficiency either.
>
> Cor van de Water
> Chief Scientist
> Proxim Wireless Corporation http://www.proxim.com
> Email: [email protected] Private: http://www.cvandewater.com
> Skype: cor_van_de_water XoIP: +31877841130
> Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
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> 

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## EVDL List (Jul 27, 2007)

Brake drag can also be a watt guzzler. Checking caliper temp should be a
quick diagnosis. An IR thermometer would be useful for that and other areas
that overheat.

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## EVDL List (Jul 27, 2007)

True, this is typically one of my first suspicions,
together with mis-aligned wheels.
Both are extremely easy to check after a longer drive:

1. Lay your hand in quick succession on all tires,
if they differ in temp then there must be a reason!
Well inflated tires that are not driven hard should
be cool to the touch, relative to ambient temp, sun and
road temperature.

2. touch the wheel nuts/bolts. Be aware that they can be
*hot* if the vehicle is driven hard or a brake is dragging.
all wheel nuts should be cool to the touch - approx same
temp as the rim. If they are hotter then you have detected
a source of heat/waste, find out where it comes from.

My truck rolls very easily. I tested this today by only
accelerating until halfway the street from where I turn
into the sidestreet that has the driveway for my office
and park in the back of the building - all the while not
touching the accelerator again!
That means from doing 30 MPH I was able to coast almost
half a mile and take 4 turns before coming to a stop
in my parking slot. I don't think I have dragging brakes.
(The elevation does not change over this distance. Google
Earth says that from the moment I released the accelerator
the road goes down 1ft to the next turn, then rises 2 ft.)

My main concern wrt energy loss is still the transmission
which may have its pump working too hard due to it being
overfilled. I think there is no fill hole, it is filled
through the check tube, so the only way to drain fluid
to the right level is to loosen the pan for some time or
to disconnect the oil cooler return line and let the
motor idle, then the oil should come squirting out the line.

The motor itself seems to be running well - when I put the
transmission in Park and turn the controller off, then I
heard the idling motor make a dozen or so more turns (it is
idling a an approx 300 RPM so only 5 turns per sec)
And I hear it stop with a soft high pitched screetch.
I was at first concerned that it had a dry bearing until
I remembered that this is a brushed motor, so the brush
on the comm will constantly rub when it is turning slow 
(at speed it seems to float on a thin layer of ionised air, 
or so I heard) so that will be the soft screetching sound.

Of course the diff will also have its losses and at some point
I may drain it and replace the fluid, but that is not my
concern at this moment - it stays relatively cool and my S10
also had no special fluid in the diff as far as I know.

Slowly I start to learn how to get the best performance out of
this unique truck. For example I found that the transmission
does have a kick down, but it works only if you put the
accelerator to the floor. In the last 1/2" of travel it will
engage the kick down on the transmission and instead of going
into 2nd gear just under 15 MPH it will hold 1st until over 
25 MPH and the shift to 2nd gear is also noticeably moved up 
to give better take-off torque from the default 25 MPH switch 
point.
I am not concerned about the constant vacuum on the transmission
which causes lower pressure, since the power into this automatic
is very low and therefor it makes no sense to prepare the
transmission for a large torque input when only power is
available to barely maintain freeway speed.
I did notice that shifts are quite hard (noticeable) which may
be an indication that the transmission is suffering from the
overfilled oil. It could also reduce loss if the parts are not
constantly running though a high oil bath, so I will try to
remove oil and see what difference it makes.
One step at a time...

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of salty9
Sent: Thursday, June 28, 2012 3:42 PM
To: [email protected]
Subject: Re: [EVDL] What a difference tire pressure makes!

Brake drag can also be a watt guzzler. Checking caliper temp should be a
quick diagnosis. An IR thermometer would be useful for that and other
areas that overheat.

--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/What-a-diff
erence-tire-pressure-makes-tp4656132p4656139.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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## EVDL List (Jul 27, 2007)

Perhaps something similar would be useful

http://www.ebay.com/itm/500cc-CAR-SUMP-GEARBOX-OIL-SUCTION-HAND-GUN-PUMP-FOR-FILLING-GEAR-OIL-280mm-HOSE-/230815387087?pt=UK_Hand_Tools_Equipment&hash=item35bdab4dcf
GEARBOX-OIL-SUCTION-HAND-GUN-PUMP-FOR-FILLING-GEAR-OIL-280mm-HOSE-/230815387087?pt=UK_Hand_Tools_Equipment&hash=item35bdab4dcf 

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## EVDL List (Jul 27, 2007)

Tonight I returned home with the SoC displaying an unprecedented 70%
after more than 10 miles drive. But that had nothing to do with any
changes to the truck, just that the average speed on the freeway was
between 25 and 30 most of the way. Sometimes slower, sometimes faster
but constantly full so even though I lost some power in braking when
it slowed down more than I anticipated, mostly it was a matter of
looking ahead and a lot of rolling (coasting). I usually try to avoid 
the freeway at 6 PM. Apparently there are benefits to a full freeway...

My ODO is nearing 70k which means that in the last 3 weeks I have done
about 350 miles with this truck, alternating with my bicycle to commute.

My ICE has now sat unused for some weeks. Perfect.


Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Cor van de Water
Sent: Thursday, June 28, 2012 1:04 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] What a difference tire pressure makes!

I was getting more and more concerned about what seemed to be a dropping
range on my truck, no matter what I did the consumption did not want to
go down much and I could barely maintain 55 on the freeway.
I had inflated the tires a month ago when I started driving this truck
but at that time they were warm so I had slightly over-inflated them (35
PSI max cold pressure so I had put a little over 40 in them as Light
Truck tires are required by law to allow at least 5 PSI over max
sidewall cold pressure) and when I checked both rear tires now they were
indeed still close to 40 (I did put a few extra PSI in them anyway) but
the front tires had lost more, one was down close to only 25 PSI, so I
pumped all of them to around 42 (this EV is never going to heat up its
tires like an ICE truck that can do max speed for hours at a time).

Now it easily maintains 55 on the freeway except on one long overpass
and I arrived at work with the consumption meter showing 63% SoC while
earlier it usually showed between 55 and 58% depending on the number of
times I would have to stop for a light.

The truck is still taking too much power to drive a constant 55, at
least to my liking the 200A draw at 110V or approx 22kW is still
relatively high when compared to the 15kW that I would like to see for
this type of trip. But at least the 400Wh per mile is more acceptable
than the 500+Wh that I saw earlier when running in lower gear (more loss
in the automatic) and too low tire pressure.

Eventually I may bring the tire pressure up to 50 PSI cold so it is
equal to the pressure in my S10 (which also had tires that had max 35 on
the sidewall but needed 50 to avoid rolling over the tire thread and
drive on the sidewall in a quick turn).

Then I may need to see if I can do something about the tranny - both the
occasional leak from the fill tube as well as putting synthetic oil in
to see if that will further reduce the losses.
And of course, avoid the more than 2" overfill that my transmission has
today. That can't be good for efficiency either.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

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| Please take those discussions elsewhere. Thanks.
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## EVDL List (Jul 27, 2007)

> Cor van de Water wrote:
> 
> > My main concern wrt energy loss is still the transmission
> > which may have its pump working too hard due to it being
> ...


----------



## EVDL List (Jul 27, 2007)

You can go a step further and also feel the right edge of the tire vs. the left edge. Some misalignments can make the inside or outside shoulder of the tire hotter. Note that hard cornering can make the outside shoulders hot even if the car is perfectly aligned for rolling resistance, so don't do this test after fast cornering (unless you are optimizing for cornering, of course).



________________________________
From: Cor van de Water <[email protected]>
To: Electric Vehicle Discussion List <[email protected]> 
Sent: Thursday, June 28, 2012 5:47 PM
Subject: Re: [EVDL] What a difference tire pressure makes!

... 1. if they differ in temp then there must be a reason!
Well inflated tires that are not driven hard should
be cool to the touch, relative to ambient temp, sun and
road temperature.

2. touch the wheel nuts/bolts. Be aware that they can be
*hot* if the vehicle is driven hard or a brake is dragging.
all wheel nuts should be cool to the touch - approx same
temp as the rim. If they are hotter then you have detected
a source of heat/waste, find out where it comes from. ...
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