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Discussion Starter · #1 ·
So Chevy just released the Order guide for the 2019 Bolt.


http://www.chevybolt.org/forum/9-20...t-online-order-reference-guide-available.html


Among the options is the "Rear Seat Delete" option for fleet purchasers. This is designed mostly for companies who want to use their Bolt as a delivery van.

Among the changes included in this option are 16" Steel Wheels and 205/55R16 tires.

Now this makes perfect sense for fleet/delivery vehicles because steel wheels are much cheaper and are generally more durable (at least they bend before they break).

Interesting to see an "official" steel wheel option.

I was originally thinking this might be a good semi-official spare tire or winter wheels set but it looks like 205/55-16 has a 2.4% smaller diameter (as well as being 4.8% narrower) than the stock 215/50-17 size. Not dramatically off but not as good as a 15" wheel and a 205/65-15 tire which is on paper identical in diameter to the stock tire size.

I wonder if GM is going to adjust the speedometer calibration for the "Incomplete" Bolts, if they don't these cars speedometers will run fast and that means the odometer will be inaccurate, your car's odometer will read 100,000 miles (when your battery warranty expires) after only 97,600 miles of driving. Of course fleet purchasers generally don't have he same kind of warranties that retail purchases do so I don't know if a fleet Bolt has the same 8 year/100,000 mile warranty on the battery that we do.
 

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Discussion Starter · #4 · (Edited)
According to http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator the speed difference from 215/50R17 to 205/55R16 is ~2%. When going from OEM size to 205/60R16, it's ~1%. At 100mph, that's only 2mph or 1mph respectively. Would a speedo recal really be needed?
Define "needed". Most cars I've owned have actually had their speedometers run 2-3% fast. I know in my Mazda is was over 2% and in fact I upsized my tires from 205/50-17 to 215/50-17 (1.6% larger) and the speedometer STILL reads fast when measured against every GPS device I've ever used.

2.4% may not sound like much but even small amounts of error add up over time and using the warranty example you could end up having your warranty expire months before it is supposed to..



If you drive ~1042 miles per month on average you will reach 8 years and 100,000 miles at almost exactly the same time. If your speedometer is reading 2.4% fast your warranty will expire nearly 2 months sooner (94 months and change instead of 96 months). Now the odds that you'll have a serious battery or powertrain issue in the last 2 months of your warranty period are very low but they aren't zero and I would not want to be the person who had that happen to them.

The cynic in me also suspects that this is the primary reason why when speedometers are off they almost always run a little bit fast (actually never seen the vehicle where the speedometer runs slow from the factory) because over tens of thousands of cars sold having all your warranties expire 2-3% sooner than they are supposed to adds up to real savings for an auto manufacturer.

Edit: Also, in modern cars with electronic speed sensors (any car with a digitial odometer reading) it's super easy for the factory to calibrate the speedometer because it just requires a minor software update with new values for converting transmission output shaft revolutions (usually) to miles.

For car owners it's usually not that difficult to adjust the speedometer calibration by inserting a box between the speed sensor and the cars computer which introduces a multiplier on the speed sensor pulses. - https://www.roadandtrack.com/car-cu...nce/a33371/how-to-fix-misreading-speedometer/

Of course the Bolt is a pretty different animal from most cars so this method may not work on it. Luckily the Bolt speedometer seems to be pretty accurate. I was planning on doing a calibration check on my car before I replaced tires the first time (mainly to see if it made sense to upsize) but I ended up having to (choosing to) replace my tires at 500 miles before I had the chance to do that.
 

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Discussion Starter · #6 ·
I wasn't able to detect any error in the Bolt's odometer/speedometer. I'm sure if I had sensitive enough measuring tools I'd detect some error, but for my purposes it's negligible.
Yeah ~1% or less I'm not going to sweat.

What I did when I was checking things in my Mazda was plug in a Bluetooth OBD reader and use Torque to read the digital speedometer reading directly from the ECU (The Mazda has an analog speedometer display) and compare it to the GPS speed. Did this with multiple phones from multiple manufacturers and got consistent results in each case.

Eventually I'll get around to doing the same thing with the Bolt but I'm not in a hurry because it seems to be pretty accurate.
 

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Define "needed". Most cars I've owned have actually had their speedometers run 2-3% fast. I know in my Mazda is was over 2% and in fact I upsized my tires from 205/50-17 to 215/50-17 (1.6% larger) and the speedometer STILL reads fast when measured against every GPS device I've ever used.

2.4% may not sound like much but even small amounts of error add up over time and using the warranty example you could end up having your warranty expire months before it is supposed to..



If you drive ~1042 miles per month on average you will reach 8 years and 100,000 miles at almost exactly the same time. If your speedometer is reading 2.4% fast your warranty will expire nearly 2 months sooner (94 months and change instead of 96 months). Now the odds that you'll have a serious battery or powertrain issue in the last 2 months of your warranty period are very low but they aren't zero and I would not want to be the person who had that happen to them.

The cynic in me also suspects that this is the primary reason why when speedometers are off they almost always run a little bit fast (actually never seen the vehicle where the speedometer runs slow from the factory) because over tens of thousands of cars sold having all your warranties expire 2-3% sooner than they are supposed to adds up to real savings for an auto manufacturer.

Edit: Also, in modern cars with electronic speed sensors (any car with a digitial odometer reading) it's super easy for the factory to calibrate the speedometer because it just requires a minor software update with new values for converting transmission output shaft revolutions (usually) to miles.

For car owners it's usually not that difficult to adjust the speedometer calibration by inserting a box between the speed sensor and the cars computer which introduces a multiplier on the speed sensor pulses. - https://www.roadandtrack.com/car-cu...nce/a33371/how-to-fix-misreading-speedometer/

Of course the Bolt is a pretty different animal from most cars so this method may not work on it. Luckily the Bolt speedometer seems to be pretty accurate. I was planning on doing a calibration check on my car before I replaced tires the first time (mainly to see if it made sense to upsize) but I ended up having to (choosing to) replace my tires at 500 miles before I had the chance to do that.
An added "benefit" to having a speedo read faster than the vehicle is actually going is that the automaker can't be (successfully) sued by an owner for their speeding ticket.

Pretty much every car I've owned in the last couple of decades had speedos that read a couple of percent too fast.
 

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Define "needed". Most cars I've owned have actually had their speedometers run 2-3% fast. I know in my Mazda is was over 2% and in fact I upsized my tires from 205/50-17 to 215/50-17 (1.6% larger) and the speedometer STILL reads fast when measured against every GPS device I've ever used.

2.4% may not sound like much but even small amounts of error add up over time and using the warranty example you could end up having your warranty expire months before it is supposed to..



If you drive ~1042 miles per month on average you will reach 8 years and 100,000 miles at almost exactly the same time. If your speedometer is reading 2.4% fast your warranty will expire nearly 2 months sooner (94 months and change instead of 96 months). Now the odds that you'll have a serious battery or powertrain issue in the last 2 months of your warranty period are very low but they aren't zero and I would not want to be the person who had that happen to them.
<snip>
That'd be pretty rotten of the reason for making our speedometers read faster. I'm going to test now with my Bolt. I'm assuming to minimize error we'd have to leverage dry, flat, straight, long, traffic-free roads to use with cruise control, but please point out any other errors I can easily account for. Though, couldn't you compare the Bolt's trip meter to google maps? Say I start/stop the Bolt's trip meter for my commute and compare it to what Google Maps calculated. Given a 100 mile route, that's large enough to minimize any wiggling of my steering wheel, right? I could also avoid changing lanes too to minimize additional distance from diagonal movements.

An added "benefit" to having a speedo read faster than the vehicle is actually going is that the automaker can't be (successfully) sued by an owner for their speeding ticket.

Pretty much every car I've owned in the last couple of decades had speedos that read a couple of percent too fast.
People do this? Sue the manufacturer for their speeding ticket?
 

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People do this? Sue the manufacturer for their speeding ticket?
The speedometer on my Plymouth Voyager reads about 10% fast at 50 km/h (it shows 55km/h). If the error was the other way and I got a ticket from some overzealous officer for going 55km/h when my speedo clearly showed 50 then I could see why someone might think a suit would be fair game.
 

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My Ampera E shows 106 km/h when doing 100 km/h. (At least over here) it is a legal requirement for car manufacturers to overstate speed.
 

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That'd be pretty rotten of the reason for making our speedometers read faster. I'm going to test now with my Bolt. I'm assuming to minimize error we'd have to leverage dry, flat, straight, long, traffic-free roads to use with cruise control, but please point out any other errors I can easily account for. Though, couldn't you compare the Bolt's trip meter to google maps? Say I start/stop the Bolt's trip meter for my commute and compare it to what Google Maps calculated. Given a 100 mile route, that's large enough to minimize any wiggling of my steering wheel, right? I could also avoid changing lanes too to minimize additional distance from diagonal movements.


People do this? Sue the manufacturer for their speeding ticket?
Yup. It's the reason I added "(successfully)" to my post. In the good ol' US of A, we sue each other for pretty much anything you can imagine.
 

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After I returned my Honda Civic a number of years ago I received a letter stating that I had become part of a class action lawsuit against Honda because their odometers were all running fast. Turns out my odometer reading at the end of my lease was 5% higher than it should have been. I received a check for about $700 rebating me the fee I had to pay for over mileage. The odometer and speedometer both use tire size and gear ratios in calculation so if one is wrong the other probably is as well. I suspect this may also account for why the speedometer is always fast and never slow.
 

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Discussion Starter · #13 ·
After I returned my Honda Civic a number of years ago I received a letter stating that I had become part of a class action lawsuit against Honda because their odometers were all running fast. Turns out my odometer reading at the end of my lease was 5% higher than it should have been. I received a check for about $700 rebating me the fee I had to pay for over mileage. The odometer and speedometer both use tire size and gear ratios in calculation so if one is wrong the other probably is as well. I suspect this may also account for why the speedometer is always fast and never slow.
Yeah I didn't even think about leases. If you've got a leased vehicle those over-mileage fees can add up quick. Would hate to pay hundreds of dollars at lease turn in solely because the manufacturer deliberately calibrated the speedometer to read fast.
 

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So, is my testing flawed some how? I measured my commute with the Bolt's trip meter and it's 102.1 miles, minimal lane changes. According to Google Maps, my commute is 102 miles. If the speedo was off, wouldn't the trip meter read different than Google Maps? Unless the speedometer had a non-linear behavior and my commute's unique collection of speed limits perfectly inversely compensated the non-linear behavior of the speedometer.

I'll dust off an old GPS and tablet and see if their GPS speedometers (and my phone's) all agree with the Bolt's or not.
 

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Discussion Starter · #15 ·
So, is my testing flawed some how?
I don't know how accurate Google Maps driving directions is at least when comparing to real-world conditions.

I'd say the most accurate way to gauge the accuracy of your speedometer (and odometer) is to find one of the repair shops that specializes in speedometer correction. There used to be a lot more of those back when speedometers were all mechanical and you needed to swap out gears or make other physical changes to fix any speedometer errors. These shops have a calibrated dynamometer so you can drive the car up to any speed (per the speedometer) and the dynamometer will show how fast you're actually driving.

Second most accurate is if you can find one of those stretches of road with speedometer check signage. Usually they have you drive 60MPH for several miles and the signs will tell you when you pass mile markers. Again I don't think these are as common as they once were.

GPS can be very accurate though, especially if you have a GPS unit that can pull from more than just the U.S. GPS constellation, if you can get more data from GLONASS and Galileo you'll have even more accuracy. I believe that most modern cell phones can utilize GLONASS and many can use Galileo as well.

If you use an app that gives you details about your GPS usage you should be able to tell just based on how many satellites your phone can see. You should never be able to see more than 8-12 GPS satellites at any point and time so if your phone says it can see 20+ it means it's also looking at GLONASS and/or Galileo. On Android I recommend GPS Status and Toolbox.
 

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So, is my testing flawed some how? I measured my commute with the Bolt's trip meter and it's 102.1 miles, minimal lane changes. According to Google Maps, my commute is 102 miles. If the speedo was off, wouldn't the trip meter read different than Google Maps?
I'll dust off an old GPS and tablet and see if their GPS speedometers (and my phone's) all agree with the Bolt's or not.
The odometer is independent of the speedometer. Most manufacturers over-represent speed from 2-6%, but dial in the odometer as accurately as possible. My motorcycle displays 6% faster than actual, and my Prius displays about 3% higher.

Good idea to test your speedo using a GPS.

find one of those stretches of road with speedometer check signage. Usually they have you drive 60MPH for several miles and the signs will tell you when you pass mile markers. Again I don't think these are as common as they once were.
Normal highway mile marker signs should be very close to accurate and could serve the same purpose as the speedo check signs. Mile marker signs are placed accurately unless there is an obstacle.
 

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The speedometer depends on the same distance information that the odometer uses. If the odometer is inaccurate, there's a pretty good chance the speedometer will be too.

I had a VW whose speedometer intentionally read fast (with stock tires), presumably due to a rule in some European country where the speedometer cannot read slow even if the largest possible tires that could fit in the wheel wells were installed.


However, since the speedometer was electronically controlled, I could see using an OBD-II reader that the speedometer was reading higher than the speed that the ECU was using and giving through the OBD-II port. When driving by radar speed signs (the ones put up on roads where people drive faster than the limit and show "your speed is ____"), the speed from the ECU matched the radar speed sign, while the speedometer showed a higher speed. Presumably, the odometer was programmed to use what the ECU believed was the true mileage.


Even with old mechanically connected speedometers and odometers, it is possible to design them so that the odometer read true (with stock tires) while the speedometer read fast.


Of course, it seems odd that VW made speedometers that read fast for US-market cars where the "cannot read slow even with the largest possible tires" rules is not present. The radar speed signs generally match exactly to the Bolt's speedometer, as they did to the speedometer in a Ford, even though both models are also sold in Europe, presumably with speedometers programmed to read fast.
 

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Okay, I'm going a little further! The suspension on my Bolt is stiff (typical) - so I'm adding a whole inch below my steel rims for extra "padding". The stock "low rolling resistance" tires spin too easy so I'm hoping softer winter tires also provides more "grab". Do you also find it annoying to spin your tires when you punch it to get out in front of an oncoming car? That low end torque is amazing, but give me some "claws" so I can MOVE!

I've heard people fuss over wheel weight like it matters. REALLY? I full "tank" is about $4! Maybe they are concerned about adversely affecting the 238 mile range. I use mine as a commuter. If you want range, buy a gas generator and add a rear hitch / platform so you can take advantage of your short length! (It'll keep BIG BULLY autos from riding your short tail!) Doubt you can charge while you're moving, but it will sure help you if you run "dry" (is electricity 'wet'?) in the desert!

I paid about $67 each for RTX 15X6.5, 5X105,56.6,39 inch black steel rims on Amazon. Not pretty, but functional and easy to clean in bad weather. I think I'm going to try some Michelin X-ICE X13 205/65R15 tires. The size comparison (tiresize.com/comparison/) shows no impact to my speedometer (matches original OD). I will let you know what I think.
 
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