Tire size vs Speedometer

[Old Bear]

I've read multiple posts about Kawasaki speedometers being off. Yesterday I went through a "Your Speed Is" radar, and it said 57mph while my Vaquero speedometer said 61mph. I was not expecting that much difference, but okay, that's what it is. So, it is nearing time for new tires. I see a popular replacement size is the 180/65, close to the original but still 0.16" shorter, making the speedometer even farther off! I see that Avon Cobras are available in 180/70, which is 0.55" taller. My limited math skills tell me that still wouldn't make the speedometer right, but it would be closer.

So the questions to the jury is why have I not seen riders going to this size (of course not an option with Comm II)? Does the engine tuners also allow correcting the speedometer, or is there another method to fix the speedometer accuracy?

[jendesigner]

I have never had a bike that has been correct. Most of the bikes I have had were up to 10% off, I am just in the habit of riding 5mph over the marked speed limit (works out to a good average), never had a problem. (ok, on the highway I ride quite a bit over the 5mph over the marked limit :) Never thought of correcting with tires or the "speedo Healer." It's to much of a habit to break now.

[ringadingh]

Either get a taller tire which will help, or a Speedohealer which allows you to calibrate your speedo accurately.

[Old Bear]

Ya just learn something new every day! Never heard of a Speedohealer, but now I've already found them! I was hoping to get a "two-fer-one" deal, like the tuner for my truck also allows me to calibrate the speedometer. Who made that rule that we can't have it all, anyway? :tup:

Oh, and a couple of better-made searches resulted in lots of info about the tires in various sizes, just couldn't find them earlier. Thanks, guys!

[Top Cat]

I see that Avon Cobras are available in 180/70, which is 0.55" taller.
why have I not seen riders going to this size

There are a lot of members running that size rear tire, me included.

As far as speed goes, I use the speed readout on my Garmin.

[cactusjack]

A taller tire will correct your speedo somewhat, but as the tire wears the outside circumference decreases and the error increases. Just figure out how much you're off, usually it's 5% on these bikes and factor that into your speed, or use a GPS.

[Pretzel]

I see that Avon Cobras are available in 180/70, which is 0.55" taller. My limited math skills tell me that still wouldn't make the speedometer right, but it would be closer.


That's what I went with, and while it was still brand new and testing with a GPS, it put my speedo spot on. After a few thousand miles, it'll start to go south again, I'm sure...

[Rasta]

When I went with a bigger CT my mph was within a mile or two with what was showing on my GPS.

[cnc]

Off 4 mph @ 60 mph is not so bad. Be aware that most speedo errors increase as you speed rises, I bet it is not off 4mph all the way through the range. Mine was off 10km an hour @ 120kmh. I don't pay much attention, just flow with the traffic and or watch the GPS. Biggest issue I have is our Canadian speedos only have kilometers marked on them.
Now 100km = 62.2mph, so 50km = around 30 mph, try doing the #@*&%# math when driving back roads and suddenly you come into a small US town that has 35mph or 40mph limits and you have had have a State Trooper following you for the last several miles. Been there several times. Usually I end up driving slower than I need to.:tehe:

[trosco]

Norm, Buy the speedo face for a US nomad, they show both MPH and KPH. Or at least the one on my 07 does. The MPH is outside the ring of hash marks and the KPH is on the inside and just yesterday I was cruising along I-85 in 70 degree (F) weather at 120KPH. And thinking that I need to ride the Nomad to C-eh-N-eh-D-eh,,,,eh?

[MarkG]

A good rule for our bikes is 10% error, while some complain about it I look at it positively. Get into areas where bikes are specifically targeted and all you have to do is drive by the speedometer. A 35mph zone puts you 3mph under, at 55mph you are 50mph. Makes it difficult to justify giving you a speeding ticket. When the rear tire was replaced from a 170 to 180 the percentage dropped slightly, still gives a good safety margin. Many other manufacturers do the same thing. I use the GPS for true speed.

[Old Bear]

Wow, guess I'm the only rider here that DOESN'T use a GPS! But it's all good information, just the same!

[cnc]

Norm, Buy the speedo face for a US nomad, they show both MPH and KPH. Or at least the one on my 07 does. The MPH is outside the ring of hash marks and the KPH is on the inside and just yesterday I was cruising along I-85 in 70 degree (F) weather at 120KPH. And thinking that I need to ride the Nomad to C-eh-N-eh-D-eh,,,,eh?

Ross, Good thing you were only thinking that, if your cruising along up here at 120kph, you would freeze something off, it's about 30f right now and going down to about 20f tonight.:D
yeah I guess I could change the face, na maybe get Sly or Guy to ride in back as decoy, yeah thats the new plan.:lmao:

[blowndodge]

My victory can change it's speedometer mode from MPH to KPH at will. :yep: Not saying yours can't.... :hmm:

[blowndodge]

A taller tire will correct your speedo somewhat, but as the tire wears the outside circumference decreases and the error increases. Just figure out how much you're off, usually it's 5% on these bikes and factor that into your speed, or use a GPS.

OMG it's Einstein reicarnated!! "Wherever you go.... there you are!"

[cnc]

My victory can change it's speedometer mode from MPH to KPH at will. :yep: Not saying yours can't.... :hmm:

Does it have an ironing app too?:tehe:

[fudd]

Think all bikes I've ever owned have had speedometer error of 5-10%? The pessimist in me wants to believe the mfrs have them engineered that way? Why? Maybe to get out of warranty 10% quicker or to make me think my bike is nearing deaths door and entice me to trade in sooner? Surely not?

[markclark57]

I believe in safety through acceleration. If you're not passing the cagers, speed up! JK

My 205/60-16 CT took the speedo to a new level of "Whacked". A couple spins past the local radar check points and I figured out the % of off-set. In the Phoenix Metro that means if the speedo reads 81 mph in a 65 zone, no need to slow down in the presence of LEO's. :D

[davidhollinger]

This is depressing... I thought my Nomad would actually do 100 MPH...guess its on 91 or so!>:(

[cnc]

This is depressing... I thought my Nomad would actually do 100 MPH...guess its on 91 or so!>:(

:hmm:Go down hill.

[Stitch]

I do not use a GPS either, but borrowed one to check both my wife's 900 and my 1700. Both read fast by 5 MPH at 60. Link is for a chart to help see the difference tire size makes. Differs a little from brand to brand. Best way is to do a roll out measurement and figure the math. However you need the tire to do it.

http://www.discounttire.com/dtcs/infoTireMath.dos

[markclark57]

This is depressing... I thought my Nomad would actually do 100 MPH...guess its on 91 or so!>:(

How fast did you want? :hmm: I don't know anyone (Yet) that bought a Nomad for "raw power". I (and some others) have spent lots of $$$ to get a little more power out of a "known for comfort" Nomad, but they are still not big on power. :ohno:

Enjoy the ride . . . or buy a Hyabusa. :cheers:

[davidhollinger]

:hmm:Go down hill.
:tehe::lmao::lmao:

[bouson]

My limited math skills tell me that still wouldn't make the speedometer right, but it would be closer.


Try using this page set up by Gadget. (http://www.gadgetjq.com/drifter_speed_rpm.htm) I used it on my 900 which was off 10% and got back 5% faster change by going to 1 size smaller width but 1 size taller tire. If you need the Vaquero service manual it's HERE from VBA. (http://www.vulcanbagger.org/pdf/2011-2012KAMCVN1700VoyagerVaqueroHDS.pdf)