Will going to a 190/55 rear help bring my speedo a little closer to reality?

[mikeames]

I know a lot of guys run 190/55 rears instead of the stock 180.

My speedometer is about 4-5 mph fast at freeway speeds.

I'm wondering if the the larger 190/55 tire would bring my speedo much closer to reality?

Anyone else have experince with this?

 

[Spud]

Yes, it moves it down to w/in 1-2mph at highway speed.

 

[NBB]

The last change I put on PR 2 190 and I'm now within 1 to 2 mile an hour of GPS indicated speed on the highway

 

[Cav47]

Ditto to what the above 2 guys said. I think in "marginally helps" with a couple other things. Wrong thread for that conversation.......might derail your question.

I honestly do not look at my speedo much anymore.

Just a guess is good enough most of the time

 

[Jer]

My speedometer and Garmin read identical speeds with the 190's.

 

[RaYzerman19]

Not perfect, but I ignore and use Garmin.......

 

[Poolboytoo]

I just rode a bun burner gold and I noticed that in 1642 miles my bike showed two more miles than the zumo 665. I just went down to verify that I infact have a 190/55 on the back. Interesting...

 

[RaYzerman19]

A GPS will never agree with an odometer or speedo exactly, due to the way GPS calculates distances...... you were lucky it was that close.....

 

[fjrob1300]

Who cares!!!!! I'm putting on a 190 because it was cheaper. if you're that concerned with speeding , or not, sit on your couch!

 

[escapefjrtist]

My speedometer and Garmin read identical speeds with the 190's.

GEN II vs GEN III speedo error Jer. Our superior GEN III's [

] are only a couple mph off with stock 180.

--G

 

[Cyclepath]

This seems weird to me.

Every time I've checked my old Garmin [or 7" tablet I now use instead] at a variety of highway speeds on my 2004 FJR, its already within 1 or 2 MPH - and that is with a regular 180x55zr17 Pirelli Angel on the back.

???

 

[mikeames]

At a speedo reading of 80 I'm actually doing 76.

It's not a big deal...just an annoyance...or a little OCD maybe.

But, I need tires and this will be one of many factors in my decision about whether to order the stock size or a 190.

Thanks all!

 

[escapefjrtist]

This seems weird to me. Every time I've checked my old Garmin [or 7" tablet I now use instead] at a variety of highway speeds on my 2004 FJR, its already within 1 or 2 MPH - and that is with a regular 180x55zr17 Pirelli Angel on the back.

???

@Cyclepath, you are correct sir, GEN I speedometers are very accurate as well. It's the red-headed stepchild we call the GEN II where the speedo's went all haywire.

--G

 

[SkooterG]

A GPS will never agree with an odometer or speedo exactly, due to the way GPS calculates distances...... you were lucky it was that close.....

Ok. I give. How does a GPS calculate distance that makes it inaccurate?

 

[MrZappo]

<blockquote class='ipsBlockquote'data-author="SkooterG" data-cid="1272844" data-time="1448431150"><p>

<blockquote class='ipsBlockquote'data-author="RaYzerman19" data-cid="1272813" data-time="1448419343"><p>A GPS will never agree with an odometer or speedo exactly, due to the way GPS calculates distances...... you were lucky it was that close.....</p></blockquote>

<br />

<br />

Ok. I give. How does a GPS calculate distance that makes it inaccurate?</p></blockquote>

GPS is not inaccurate. Maybe not 100% perfect but still very accurate.

 

[mikeames]

Sometimes a GPS will tend to straighten the curves a bit due to signal loss or poor signal. This can effect the distance traveled it records verses time resulting in a sightly inaccurate speed displayed.

 

[SkooterG]

GPS is not inaccurate. Maybe not 100% perfect but still very accurate.

That is my opinion too. Which is why I asked for more clarification.

Sometimes a GPS will tend to straighten the curves a bit due to signal loss or poor signal. This can effect the distance traveled it records verses time resulting in a sightly inaccurate speed displayed.

Not very often at all based on my experience.

 

[RossKean]

GPS does not (directly) measure speed. It is taking a bunch of position measurements along with time and is calculating the speed between them. Works perfectly on a straight, flat stretch. On a curve, the series of straight line segments will be slightly less than the actual curve so it will underestimate speed. The extent of the error depends upon the frequency of the position updates. The effective update rate will be lower if the GPS signal is poor. Also, the GPS works off an XY coordinate without (as far as I know) figuring elevation changes. If, for example, you have a 10 mile stretch at 10% slope, the GPS might consider this as 10 miles while the road surface distance is 10.05 miles. Pretty small error in an extreme situation.

Between any odometer and GPS, I'll believe the GPS.

 

[ionbeam]

...without (as far as I know) figuring elevation changes...

That information is available for a Zumo 550 to use. On the ferry out to Long Island I could watch our 'altitude' change as the ship rolled on the waves, one day the GPS showed that we were going up and down between 4 - 6 feet, another trip showed basically flat seas. When I go through a trip log, the 550 can produce an altitude map of the trip showing the elevation change every time it took a 'bread crumb' reading. The 550 also has an altitude 'gauge' which I do watch in mountainous areas just out of curiosity. Sometimes it agrees with road side signs and other times it can be off by 50-100 feet at an altitude of 10k feet.