How To Adjust Speedometer for Larger Tires?

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  • So, I figured out (was told) that the speed sensors are in the front wheels, not the transmission/rear. As such, ZZP was unable to reprogram the ECM for the larger wheels. I've been running my GPS and I can tell that my speedo is off by at least 10%. If it says 70, I'm doing at least 77. That's a little too much difference. Anyone know how to do it? And Yes, I searched. Both Sites. And Google. And YouTube. And Sam Owens. And I know the dealer can set it for base and SL. But what about custom sizes?

  • Nope. That's all the dealer has available is the two different factory wheel sizes. I used a kit on my Z1000 Kawasaki from Heal Tech Electronics called a Speedo Healer that was user friendly. You could tap into it for speedometer changes like -99.9% to +9999.9% in steps of 0.1%. I'm sure someone who is electrically knowledgeable MAY be able to find a way to make something like this work

    Never be held prisoner to your past. It was a life lesson - NOT a life SENTENCE

  • I have a custom size on mine. They are actually taller than the factory by over an inch for ride height. I am set up on the SL setting and the speedo is right on the money. I have checked it with GPS and the speedo matches the GPS speed. Not sure if the SL setting is a little more fluid than the Base settings.

    CO D12


    Hahn SST stage 2X PRP Seats Sparco Steering Wheel (Not SLR) w/ NRG 3.0 Quick release Canadian Headlight R-Shot Accessories Windscreen Rear Protection Plate by Slinglow NASCAR Windshield Kenwood Double DIN SSV head pods with Polk DB 6.5"s SSV Works Subwoofer enclosure w/10" JL Audio Kenwood Amps Slingshot Side Storage 11 Piece Mat Kit TD Canvas top TD lip spoiler 22" Asanti Wheels TD sway bar TD shifter boot cover & parking brake Graphics by AMR Racing QA1 front TrakHamr rear

  • ummm I haven't even worried about it lol. maybe I should? but then again if I drove the speed limit then that might be something to look at also lol. I never go the speed limit. I am always over. but I have the base slingshot which came with 17s on the front and now am running 20's. I have no idea how far off it is.

  • The best way to get accurate speedometer readings after installing larger wheels is to get a GPS HUD. I have this one purchased from Amazon for $35 and I think it is a great mod to boot :

    https://www.amazon.com/gp/prod…tle_o02_s00?ie=UTF8&psc=1


    It comes with a long enough USB cord to plug into the port in the glove box and routed along the firewall so installation was simple. I had to make some adjustments to mine out of the box but instructions are easy to understand and there is even a You Tube video. A simple and economical fix to the problem.

    Always be yourself unless you can be Batman.
    Then be Batman!

  • It is not, but it can be easily unplugged and thrown in the glove box when needed. The bottom of the unit has a type of sticky rubber that keeps it from sliding and is not permanently fixed to the dash using 3M tape or the like. Just make sure that the end of the cord is dry (usually by blowing on it) before you plug it back in. When the bottom loses it's stickiness I run it under the kitchen faucet on a low trickle being careful not to get the top or port wet. Just put your finger over the port. Let it air dry and the stickiness comes right back.

    Always be yourself unless you can be Batman.
    Then be Batman!

    Edited 2 times, last by Blaze ().

  • The best way to get accurate speedometer readings after installing larger wheels is to get a GPS HUD. I have this one purchased from Amazon for $35 and I think it is a great mod to boot :

    https://www.amazon.com/gp/prod…tle_o02_s00?ie=UTF8&psc=1


    It comes with a long enough USB cord to plug into the port in the glove box and routed along the firewall so installation was simple. I had to make some adjustments to mine out of the box but instructions are easy to understand and there is even a You Tube video. A simple and economical fix to the problem.

    did you need to buy the windshield film also or does it come with it?

  • I had three different gps HUD speed displays from Amazon that collectively lasted three months. Was running base model 18" rear, 17" fronts with all season tires for cold weather and 20/19 high performance summer tires and didn't want to pay $50 dollars or more to get the ECU reprogramed seasonally. I found a nice gps speedo with 52mm pod from Speedhut and mounted it just to the left of the driver side painted dash cover. Now running 19" all around and appreciate the accuracy. Had it a couple of years so don't remember how much it cost but as a SS mod it ranks fairly low $ wise. (To clarify, The Rock mounted it for me.)

  • General Comment about WillTheyFit's speedo calculations - I entered the stock Polaris rear tire/wheel info vs what I'm currently running on both WillTheyFit.com and Discount Tire's Tire Size and Conversion Calculator.The attached pic shows the info entered and the results each website produced. Both sites calculated the 305/30R18 tire to be approximately 2 mm shorter than the stock tire, yet WTF reports the new tire to run slightly faster while the DT site shows it to run slightly slower. A SHORTER tire will not turn as fast at the same engine rpms as a larger tire since the shorter tire will have a smaller circumference and will cover a shorter distance at the same rpm, resulting in a slower speed than indicated compared to the original tire. I like the WTF site since it provides a visualization of how the new tire/wheel will sit compared to the original tire/wheel, but the WTF speedo calculations are incorrect. The DT calculator provides a much better estimation of the impact of tire size vs speedo error.

    I will be try redoing the screen capture pic for easier reading. Redid the screen captures, but they may still be a little hard to read.

    Edited 2 times, last by BKL ().