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Re: Rain Sucks

Posted: Sun Sep 22, 2019 8:38 pm
by Flyct
I’m impressed with the efficiency you get. With my SL+ I normally only get 3.6-3.9 at 65 mph. Tires at 38 psi, AC set to 73 deg (OAT ~90 deg) and about 500 lbs in cabin between driver, passenger, dog and baggage.

I routinely do a 125 mile trip on sea level flat land between house and cabin across Florida. When I arrive after 125 miles I have about 80-90 miles of range remaining on the GOM and LeafSpy.

Re: Rain Sucks

Posted: Mon Sep 23, 2019 4:34 am
by DougWantsALeaf
I would be at that efficiency if I didn’t ride with a block of traffic. Even mild slipstream help can push you up a few tenths. If you drive 135 miles and have 85 left on the dash, you likely have another 20-30 in reserve which is pretty close to what I am seeing range wise.

I really want to find a weekend to try to replicate the 500km and 1000 challenges seen with next move and bjorn as I believe they can be done substantially faster if planned well and some luck with the EA chargers.

Re: Rain Sucks

Posted: Mon Sep 23, 2019 9:00 am
by frontrangeleaf
There seems to be some discrepancy with the Leaf reported air pressure and my digital gauges (plural). My gauges all report 40 psi on all tires. Car reports 36.

I trust my gauges. Particularly because they’re all consistent with each other as well as with my old school pen type gauge.

I’m not inclined to sweat a couple of pounds either way as long as I’m not running low. I routinely run 10% over car sticker on all of our vehicles because we have such large temp swings between daily high and low. That alone can trigger a 3# psi difference.

As always YMMV.

Re: Rain Sucks

Posted: Mon Sep 23, 2019 10:40 am
by goldbrick
I think the TPMS reports absolute pressure while a tire gauge will report relative pressure. Or something like that :?: I remember reading about the difference and it made sense at the time but I can't remember enough details to know if this could be the cause the discrepancy you are seeing.

My digital gauge is about 1 PSI off from the TPMS readings which I find to be acceptable error. The pressure varies quite a bit with temperature as well but I'm sure you know that.

Re: Rain Sucks

Posted: Sun Sep 29, 2019 2:33 pm
by GerryAZ
webeleafowners wrote:
Sun Sep 22, 2019 7:43 pm
Are the tires on the Eplus SL the same as the tires on the Eplus SV?
Yes, unfortunately they are Michelin Energy Saver A/S 215/50 R17 tires like my 2015 SL came with. I will be replacing them with much better tires as soon as they wear out. They actually seem to grip better in the rain than the one that came on the 2015, but they are still marginal at best. Tire pressure dash display in 2019 and reported by Leaf Spy for 2015 and 2011 have always matched my gauges (digital, dial, pencil, and outlet gauges on compressors). I generally run 44 psi cold on the OEM tires with 44 psi maximum shown on sidewalls. I tried up to 51 psi in the Continentals (sidewall maximum) I had on the 2015, but found that a bit harsh and settled on 48. I ran 46 psi in the Ecopia + tires which replaced the Continentals (215/55 R17 with 51 psi maximum pressure rating).

Re: Rain Sucks

Posted: Sun Sep 29, 2019 3:14 pm
by GRA
goldbrick wrote:
Mon Sep 23, 2019 10:40 am
I think the TPMS reports absolute pressure while a tire gauge will report relative pressure. Or something like that :?: I remember reading about the difference and it made sense at the time but I can't remember enough details to know if this could be the cause the discrepancy you are seeing.

Highly unlikely. The difference between psia (lbs. square inch absolute) and psig (lbs square inch gauge) is 14.7 PSI or one atmosphere. The gauge ignores that 14.7 psi, which is the pressure of the atmosphere at sea level, and only looks at the difference between that and the air pressure inside the tire.

Re: Rain Sucks

Posted: Sun Sep 29, 2019 6:58 pm
by goldbrick
I honestly don't know the details and actually I don't really care that much although I am a bit curious, but this article seems to indicate that the TPMS system takes the atmospheric pressure into account.

https://www.quora.com/What-type-of-pres ... l-pressure

This all assumes that the TPMS is using direct measurement. Apparently some systems measure the rotation speed of the tires somehow and use that to calculate the air pressure while some use a direct (absolute) pressure measurement.

https://en.wikipedia.org/wiki/Tire-pres ... ing_system

Re: Rain Sucks

Posted: Sun Sep 29, 2019 7:21 pm
by LeftieBiker
I've always assumed that the TPMS just measures the tire/wheel diameter via the rotation period, and then translates that to psi indirectly.

Re: Rain Sucks

Posted: Mon Sep 30, 2019 7:03 am
by GerryAZ
Some vehicles look at wheel rotational speed differences by using the ABS sensors to detect a tire going flat. Those vehicles will not indicate low tires due to temperature or altitude changes since all four tires will be soft, but still rotate at the same speed.

The LEAFs (at least all cars intended for USA market--2011 and 2012 made in Japan and 2013 through 2019 assembled in Smyrna) have a sensor in each wheel that directly measures pressure and periodically transmits data which includes sensor ID and pressure to a receiver in the car. I don't know if the sensors measure gauge pressure or absolute pressure (difference is 14.7 psi at sea level), but suspect they measure absolute pressure. If sensors measure absolute pressure, the car must somehow convert the readings to gauge pressure because the dash display on 2018 and 2019 (and CAN Bus data displayed by LEAF Spy on earlier models) is approximately equal to gauge pressure. If the conversion is simply to subtract 14.7 psi, then the displayed pressures will be lower than true gauge pressure at higher altitudes.

Re: Rain Sucks

Posted: Mon Sep 30, 2019 6:22 pm
by GRA
^^^What GerryAZ said. The tire pressure placard inside the door is in PSIG, so even if the TPMS measures absolute pressure it has to convert that to gauge, which is the difference between the ambient air and the air inside the tire, and is what a tire gauge measures. Otherwise, using a tire pressure gauge makes no sense at all, as you would have a reading varying by 14.7 PSI +- a bit depending on local air pressure.