[pagrey]

Yeah but still

Laser beams, sharks with laser beams? Throw me a bone here.

 

[GregBrew]

GPS calculates distance from the satellites using dopler shift of the RF, you can't calculate the shift unless you know your exact speed. Speed is used to calculate position, not the other way around. Calculating speed from changes in position is possible but not necessary, GPS chips output speed and heading/bearing data directly and most start sending this data before a position fix.

Nope.

You're describing a Doppler Positioning System.

GPS uses...well...the Global Positioning System, that wants the receiver to "see" four satellites for a good fix, using timing delays between sending satellites. The sent time is embedded in the signals. They don't use frequency shifts due to motion.

From the NIST website:

"Multiple satellites beam signals at the speed of light toward Earth, and your device receives the signals at slightly different times, based on how far away each satellite is from your location. These times can be used to calculate the differences in distance from each satellite to determine your location on Earth."

How Do You Measure Your Location Using GPS?

Satellites beam signals at the speed of light toward Earth, and your device receives the signals at slightly different times, based on how far away each satellite is from your location. These times can be used to determine your location on Earth

www.nist.gov

 

[mrrobertosir]

Laser beams, sharks with laser beams? Throw me a bone here.

An evil petting zoo? 1...MILLION dollars!

 

[Left Coast Geek]

Why are big wheels still cool when everyone has them? I want fat tires, no more scratched or broken wagon wheels.

totally with you there. I bought a Ford Expedition to tow my small camp trailer... silly thing came with 22" wheels, I think they were 285/45R22 ... insane size on a big truck. I 'downgraded' them to the base model's 18" wheels, 245/65R18, dropping the pressure from 39 PSI to 35 PSI. way nicer ride.

 

[pagrey]

Nope.

You're describing a Doppler Positioning System.

GPS uses...well...the Global Positioning System, that wants the receiver to "see" four satellites for a good fix, using timing delays between sending satellites. The sent time is embedded in the signals. They don't use frequency shifts due to motion.

From the NIST website:

"Multiple satellites beam signals at the speed of light toward Earth, and your device receives the signals at slightly different times, based on how far away each satellite is from your location. These times can be used to calculate the differences in distance from each satellite to determine your location on Earth."

How Do You Measure Your Location Using GPS?

Satellites beam signals at the speed of light toward Earth, and your device receives the signals at slightly different times, based on how far away each satellite is from your location. These times can be used to determine your location on Earth

www.nist.gov

I forget how difficult science is for most people, sorry. If you ever have the chance to look at the NEMA output of a GPS receiver you'll see what I'm talking about. Let's just call it magic and be done with it.

 

[mrrobertosir]

totally with you there. I bought a Ford Expedition to tow my small camp trailer... silly thing came with 22" wheels, I think they were 285/45R22 ... insane size on a big truck. I 'downgraded' them to the base model's 18" wheels, 245/65R18, dropping the pressure from 39 PSI to 35 PSI. way nicer ride.

Cheaper tires too, if you're into money

 

[Left Coast Geek]

Cheaper tires too, if you're into money

well, the KO3's I'll be putting on there won't be cheap. when I got the 18" wheels, they had brand new wranglers on them so I've been trying to wear them out.

 

[Toyotiac]

Looking forward to hearing your assessment! Even though mine is a 2020 EV, the ride is pretty stiff. Dealer told me that a rattle I hear after having the battery replacement was the rear shocks (even though it sounds like the back seat doesn't latch as tight) so have been looking for recommendations for replacement shocks to smooth out the ride, however so many folks say it is the tires. I don't like the idea of lowering the air pressure because I know what kind of hit you can take on range. I remember just changing tires on my Leaf to non-EV tires cost me over 20% of range and I think helped to wear out the battery quicker.

Best to you. 🤞for good results!

It’s too early for any broad conclusions, but I am encouraged by the consumption numbers on the DIC. With the OE tires and rims, in town driving occasionally went to 5-5.1mi/kWh. I am now seeing 5.5-5.6, numbers I have never seen in 3 years of ownership.

 

[CanAmSteve]

Speedometers aren't accurately calibrated, plus or minus 5 is pretty common and +-5mph at 50mph (10% as mentioned) is what I think the current law is in the US. They aren't set high or low on purpose and I didn't see any reference to high or low in the rules.

On older cars with an analog needle, even an electronically controlled needle, the speedometer and odometer don't always agree. The analog needle often points to a different value from what the ECU is reading due to the gauge aging or just starting out poorly. If the vehicle is new enough to have OBD2 you can check the speed with that.

Many trucks like Ram/Dodge have tire size adjustments in the ECU that can be changed with the factory scan tool. It makes sense, many full size trucks have different diameter tire options from the factory.

As far as I know there are no vehicles that use GPS to calibrate the speedometer. You don't want vehicle speedometers going crazy when you drive in low traction situations like snow and dirt and then transitioning back days later under normal conditions. Chrysler navigation radios at some point did calibrate their internal speed with GPS and use dead reckoning when the GPS signal is lost like when driving through a tunnel but that information was not relayed back to the ECU. It's possible some vehicles do this, I've just never seen it done.

EU requirements are more strict than the USA. But I suppose they can just make "sloppy" speedos for the US and UK (only countries using MPH)


"European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers[9][10][11] are similar to the UNECE regulation in that they specify that:

• The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
• The indicated speed must not be more than 110 percent of the true speed plus 4 km/h (2.5 mph) at specified test speeds. For example, at 80 km/h (50 mph), the indicated speed must be no more than 92 km/h (57 mph)." [Wiki]

 

[pauln1960]

It’s too early for any broad conclusions, but I am encouraged by the consumption numbers on the DIC. With the OE tires and rims, in town driving occasionally went to 5-5.1mi/kWh. I am now seeing 5.5-5.6, numbers I have never seen in 3 years of ownership.

Thanks...that sounds promising. I've been thinking about going to a tire and wheel specialist to get the whole rough ride thing looked in to...but Sounds like I found a better one here.

Thanks again Toyotiac (assuming that is like a Pontiac made by Toyota or vise versa)...it is very thoughtful to provide follow up info and not a lot of folks do. I definitely have a watch on this post!

 

[mrrobertosir]

It’s too early for any broad conclusions, but I am encouraged by the consumption numbers on the DIC. With the OE tires and rims, in town driving occasionally went to 5-5.1mi/kWh. I am now seeing 5.5-5.6, numbers I have never seen in 3 years of ownership.

I appreciate you reserving judgment, it's too easy to jump to conclusions. One thing is not living in fear of curbs.

 

[GregBrew]

I forget how difficult science is for most people, sorry. If you ever have the chance to look at the NEMA output of a GPS receiver you'll see what I'm talking about. Let's just call it magic and be done with it.

I'm a freaking Electrical Engineer, and also taught Physics for twenty years. I know what I'm talking about. There's no "magic" involved.

I cited my source, and you come back with condescending bullsh*t, rather than speaking to the subject.

We can all see who the one is that finds science to be "difficult".

Good to see you're cutting your losses and moving on.

Good day, sir.

 

[bkwanab]

With about 56k miles on my Bolt, I just replaced my original tires with the same Michelin A/S tires from Costco. I felt a noticeable improvement in ride quality with the new tires. I don't know if that's just an emotional thing, or whether it's the due to the deeper tread on new tires vs old, or whether there is some difference between the OEM tires and the replacements. Back when I changed the oil in my ICE car, I remember feeling the engine ran smoother with the new oil - which I have a hard time believing to be really true. So maybe we all just want to feel an improvement after changing tires.

Tires are like people. As they age they get stiffer (in all the wrong places. ;-))

It's not the walls, it is the tread. When I was racing back around the birth of radial tires I discovered by accident that tires that were almost worn out gripped better but rode harder. You notice things like that when your ass is only an inch above the track surface.

I was racing a Formula Ford and scrounging used G800 tires from my local Goodyear dealer. He would mount them for me and turn them down to around 3/16" to smooth the existing worn tread and ensure they spun concentrically and were balanced perfectly. I put his dealership name on the car and he found four used tires for me every week. He'd take my 'old' old ones back and swap them for 'fresh' old ones. Free!

I could always lap faster on these reused turned down tires than I could on new ones. I found they were even quicker when turned down even more but the regulations defined the minimum tread depth at 3/16", which they checked during scrutineering before we were allowed on track. This was good, because they were always nearly bald following the races. The new tires with full tread felt more 'comfortable' but squirmy in the corners. And were definitely slower, which I presume is from higher grip creating greater drag.

FYI, I replaced the OEM supplied 20" Pirellis on our 2006 Range Rover SC with sticky Kumho tires. The fuel mileage cruising on the interstate instantly dropped from 20 mpg down to 16 mpg!