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Discussion Starter #1
when changing front tire size is there any way to recalibrate the speedometer like american cars can do
 

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Hi Mr. Robinson. I asked the question on the forum a while back as to which of the 4 tires the computer took it's reading from for the speedometer. I found that my speedometer was off by a whopping 4 mph. I checked this with a GPS app on my phone, I checked it with the Garmin Nav, and I also chjecked it by the speed radar the DOT places on the interstate at the beginning of a construction site to get you to slow down. I have to run the speedo up to 74 mph to actually be doing 70. So I was asking the question because I wanted to go a couple of sizes taller if I could, and was wondering about how critical the smaller size in the front was to the size on the back. Well to make a long story short RustedWrench stated that the computer takes readings from all 4 tires at once and uses that data to run the speedometer. So I guess the back axle gives the same reading for the back two and the front two would have the same unison reading, but different from the back. I guess of the readings get too far out of whack it can throw the Smart into "limp mode" which severely limits your power and speed until you shut down the vehicle and start it again.I know alot of people on this forum run the same size tires front and back by buying 2 more back rims for the front, so I know you can get by with that. By as to calibration, I don't kow if that can be adjusted electronically or not. DCO
 

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Again talking 2 different systems here, speed id electronically calculated and for some reason is set about 4 or 5 miles faster than the actual speed of the car.

The sensors at each wheel are there to check axle rotation speed and if one axle, or more spins noticeably faster than the others, the Traction Control or the ABS steps in and starts shutting things down to compensate for the car sliding. A good thing when you hit a patch of black ice, but darn annoying when you are stuck in some snow and trying to get out. I have had the traction control kick in when doing 60 down the highway and come across some slippery stuff. It does keep you going straight as it will kick in before you realize it is slick out.

I have also got stuck on a level driveway when trying to back out of a 3 inch hole of ice too. It would be nice to have a button to shut off the traction control when you need to. I did the 2 handed button-key thing with a couple of pencils and was able to get back in the driveway. Then I went back inside and stayed home.

I have had all 4 wheels (and rims) the same size on a few smarts now ith no problems with ABS or TC.

I don't believe a dealership will adjust the speedometer calibration unless it is off by a lot more than 4 MPH. Most law officials allow a certain +- of the speed limit to allow for speedometer inaccuracies and I believe 10% is about the norm. If they want to pull you over, they have a number of ambiguous reasons and speed is just one of them. Lately their favorite has been license plate light not working. but that is a different story.
 

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Discussion Starter #5
please excuse my denseness rustedwrench i'm still in a learning curve on this little car. who would have thought this little car could be so intricate compared to american cars. seems they have a different engineering logic then we do.

but what is number 541?

and talking about ambiguous reasons to pull people over here in Florida if you have a license plate bracket around the plate they can ticket you if you get a snotty john wayne cop with a bad hair day

with all that being said you have just about convinced me to get two more rims and run 185/60 tires on all corners
 

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When I finally ended up with worn out snow tires, AND worn summer tires, I went with the all 4 tires setup and I should have done it a long time before that! makes a big difference. I went with the General Altima as they were designed to smooth out the bumps, and they do!
 

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Hi Mr. Robinson. I asked the question on the forum a while back as to which of the 4 tires the computer took it's reading from for the speedometer. I found that my speedometer was off by a whopping 4 mph. I checked this with a GPS app on my phone, I checked it with the Garmin Nav, and I also chjecked it by the speed radar the DOT places on the interstate at the beginning of a construction site to get you to slow down. I have to run the speedo up to 74 mph to actually be doing 70. So I was asking the question because I wanted to go a couple of sizes taller if I could, and was wondering about how critical the smaller size in the front was to the size on the back. Well to make a long story short RustedWrench stated that the computer takes readings from all 4 tires at once and uses that data to run the speedometer. So I guess the back axle gives the same reading for the back two and the front two would have the same unison reading, but different from the back. I guess of the readings get too far out of whack it can throw the Smart into "limp mode" which severely limits your power and speed until you shut down the vehicle and start it again.I know alot of people on this forum run the same size tires front and back by buying 2 more back rims for the front, so I know you can get by with that. By as to calibration, I don't kow if that can be adjusted electronically or not. DCO
In 1994 my father in law bought me my first GPS upper right the Lowrance
As you see, I have aquired a few more.

I have used these GPS units to check the speed on every car my wife and I have owned since 1994. I have never found any of our cars to off more than 1 MPH at 60 MPH, as a matter of fact, our 20 year old 1996 Chrysler minivans speedometer is and always has been DEAD ON, regardless of tire wear or which GPS unit I'm using and yes I have had ALL of them running at the same time and all displayed the same speed.
Our 2016 Ford Escape displays 61 MPH fast at a true 60 MPH. My 2009 Toyota is dead on.
On the other hand my 2009 Smart Fortwo cabro is 5 mph optimistic at 70 mph, means I'm only doing 65 mph.
I believe as consumers we have a right to properly functioning equipment.
A gauge that doesn't display the correct information and can't be adjusted to display the correct information is malfunctioning and useless.
To be set intentionally any percent off is ridiculous.
We the consumers need to demand accurate and correct gauges.

You are going to have some unenlightened people who say civilian GPS is as accurate as the military's.
They are only somewhat correct.
During the 1990s, GPS employed a feature called Selective Availability that degraded civilian accuracy on a global basis.
In May 2000, at the direction of President Bill Clinton, the U.S. government ended its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
The United States has no intent to ever use Selective Availability again.

Is Military GPS More Accurate Than Civilian GPS to pinpoint a spot on the ground? Yes
and this is why.
The accuracy of the GPS signal in space is actually the same for both the civilian GPS service (SPS) and the military GPS service (PPS). However, SPS broadcasts on one frequency, while PPS uses two. This means military users can perform ionospheric correction, a technique that reduces radio degradation caused by the Earth's atmosphere. With less degradation, PPS provides better accuracy than the basic SPS. That said, Current civilian GPS will get you to within 2.18 meters of a given spot 95% of the time.

GPS speed calculations are far more accurate than pinpointing a certain spot on the ground.

Generally most GPS manufacturers claim a 0.1MPH tolerance with speed readings, however will go as far to say a 0.5MPH inaccuracy is possible, to make allowances for any satellite signal variations beyond their control.

I don't think you need a Military grade GPS unit to prove the Smart ForTwo Speedometer readings Suck.


Since the year 2000 close to a dozen new improved GPS sat. have been put into service.
 

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There are people still crying and moaning about the analog speedometer in the smart. The speed from the CANbus is dead on if you are running factory tires, make use of that. If someone has a GPS in their car all the time why would they care what the analog speedometer says. Find something important to obsess over.
 

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You're right. We should all take our cars in to the dealers and demand a full refund! After all. it is inexcusable that the speedometer is not exactly correct. Even though the cars are made in a different country for most probably metric size tires and calibrated for Kilometers instead of Miles. There should be a total recall of all the smarts since day one and a complete return of both money paid and interest on loans. I mean if a Chrysler can be accurate, Oh wait, Daimler does own a portion of smart... and even Police cars need to have certified speedometers to be able to pull over speeders and most use radar guns which also need to be calibrated..

I guess the only choice is to have our cars brought in and have the speedometer certified and the calibration checked every 3 months. I am sure there will be a minimal cost of say... $500-$1000 for each check.

Come on now!! lets be realistic If the speedo is off a few miles per hour, and you know it, slow down or speed up.I am sure we have more important things to worry about.


How about a class action law suit for heater blower motors that would fail... oh yeah, that went away too. or rans that would shift into neutral at stop signs, also went away with a software fix...

I had a brand new 1971 Pontiac Firebird that the speedometer was off by 35 MPH going down the highway. it was back to the dealer 3 times before I finally bought the correct adapter to fix it myself. I could tell how fast I was going by the other cars and just the feel of the car.
 

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Sorry Sport, exactly how did the problem with broken blower motors 'just go away'? I'm sure the people who paid $200 for a new motor have a different opinion. How about current fuel tank problems? Speakers, subwoofers, sunroofs, ......
 

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Sport???

Lets see... my first 2008 caught on fire with 17,000 miles on it, 7 months old and I was driving down the road at the time... My second one (they replaced it with) a 2009 got stuck at a stop sign and wouldn't go into gear. I took it to the dealer and when they test drove it, it came back on a tow truck. then with no dealer in the state (after Penske pulled out and Mecedes couldn't figure out what to do) I spent 3 days troubleshooting why the car would start skipping gears after driving about 5 miles, ..
and of course during all this, the heater fan would stop working when it got below -15 degrees again which I fixed since there was no local dealer, The solid top (pure) also developed a bubble and peeled off most of the material, replacing the stock cooling fan with an aftermarket one, replacing numerous headlights, and losing the hold down clips, Replaced the exhaust due to broken flex pipe, a 2 year battle with a spark miss until it lost compression on a cylinder,..2 or 3 broken windshields, and well over 200,000 miles of driving, I can say I have seen just about everything.


Replacement heater fans are a lot cheaper than $200 on Ebay, and alternative sources. dealer prices are probably the most expensive place to get things and there are always alternatives if you want to spend the time to look. When all this stuff happened, this site was in it's infancy and there was very little information available anywhere about the 451.

As for the 'Gas tank problem' every smart I have had does the same thing. If you fill it at a pump with the auto shut off at max, it will stop taking gas at least a notch below full no mater how many times you try to top it off. Once you stop, the check engine light will go on as it would flood the vapor canister and require a dealer visit to clear the canister and reset the light. The fix was to add the 'Do not to off" warning on the car. I found that if you fill the tank at the lowest setting, then proceeded to wash all the windows, then topped off the tank maybe twice, it would always register full. If you were in a hurry and it was full but didn't show it in the gauge, at times it would show full after a short drive. Checking the MPG I would consistently get the same MPG and use the same amount of gas whether it said full or not. Lots of owners went back to the dealer with the problem and usually it didn't change with reprogramming.

I can't answer for any of the 453 problems as I don't own one and can only assume that the technology has improved as reports of handling , ride and such are quite a bit more favorable. The original stereos, speakers and sub woofers were nothing to write home about and most owners opted for aftermarket units Personally I was not enough of an audiophile to really care much either way. And with such a small area inside a smart, I don't know if here is a lot you can do with it.

Maybe I will pick up a new 453 someday but I am more than happy with the 2008 I picked up that needed some attention, including a heater motor and a few other things here and there, but it drives just fine and I plan on putting lots more miles on it.

If that makes me a 'Sport', then I wear it proudly!!
 

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Sorry Sport, exactly how did the problem with broken blower motors 'just go away'? I'm sure the people who paid $200 for a new motor have a different opinion. How about current fuel tank problems? Speakers, subwoofers, sunroofs, ......
- The blower motor issues were pretty much resolved in the 451 2011+ facelifts.

- Speedometers are legally able to be off by a few mph under the speed limit. Many manufacturers do this to account for a variety of factory tyre sizes and global speed limit regulations. Some manufacturers will fine tune the speedometer to each country and each tyre size, some won't. Having 100% perfection would likely raise the price, not worth it for a trivial issue like that, especially in the USA where smarts are already seen as 'too expensive'.

Many American cars don't come with many tyre sizes and aren't sold in 40 countries like a smart is, it's unequal to compare the two.

- Speakers and subwoofers blow in every car. That said, broken smart speakers don't seem to be a widespread issue either. My first speaker blew at 90k, and it took me maxing out the volume for 90k to do that (I like loud music).

- The panoramic roofs changed formulations in 2013. This was supposedly the solution. Seeing as we haven't seen reports of a 2013+ crazing, I think we have a success!

The fuel tank issue is a whole 'nuther animal, ugh. Seems smart USA is taking those "Alternative Facts" a little too literally.

Point is, all cars will have some bugs, and like most products with a multi-year run (operating systems, phones, computers, TVs, aircraft, RVs, boats, etc), those bugs often get ironed out over time with updates and or newer models. And outside the gosh darn awful fuel tank issue in the 453s, there's nothing surprising or unlawful about the 451/453 of the smart fortwo.
 

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I've pretty much ignored the speedo problem with smarts, never had an accurate speedo in any car I've driven so what's new? I've even had a '68 Ford station wagon that picked up 1 mph for each 10 mph of speed! Showing 60 when actually doing 66, glad I noticed that before a cop with a radar gun did.
 

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please excuse my denseness rustedwrench i'm still in a learning curve on this little car. who would have thought this little car could be so intricate compared to american cars. seems they have a different engineering logic then we do.

but what is number 541?
Intelligence test. Everybody failed.

Question number 541. :laugh:
 

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Discussion Starter #17
here in Orlando there are several places that will recalibrate speedometers. in fact the highway patrol goes there to have their speedos calibrated. i just didn't know if the Smart could be or not without asking the consensus so i 'd know whether to go there or not.

guess that's one thing the Germans overlooked (at least older american cars could do that cause they were driven off the tranny).
 

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nAnother extremely useful (to me) feature of the UltraGauge is that it can be calibrated to provide true distance and speed for a given vehicle/wheel/tire combination. The instructions are pretty clear, but the UG factors the distance the car thinks it went against a measured distance, i.e. a series of mile markers. By applying the correction factor, the correct speed and distance are displayed on the UG. That also plays into accurate MPG measurements.

Also, I think I'm speaking for a lot of us when I say that juvenile, demeaning, or passive-agressive name calling isn't really appeciated here. Whaddaya think, Sport?
 

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Ill ask "sport" next time I see him He is taking a nap as PT after knee surgery is a bit tough. Won't be much in the way of sports for quite awhile and he gets crabby when he is reminded about it.....


The best way to handle the passive-aggressive juvenile demeaning name calling is off line via a personal message. If that doesn't work, there are other ways to handle it or let a moderator know. but try to handle it with a PM first. There is a provision against name calling in the TOS . Repeated name calling and insults will not be tolerated. which could be invoked if needed...

I used that feature on my Scangauge when I had it on my Land Rover and it worked quite well. It did get confused about a 3 cyl 1L until I changed it to a 8 cyl 4L and a larger gas tank... There was talk about using it to program the AreA451 cruise, but that all got sidelined when smart started making cruise an option (Good idea on their part)
 
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