cruise control speed reading compared to speedometer

[jschmank]

2011 platinum. I notice that the mph indicated in the message box when cruise in engaged is not consistent with the speedometer. For example, if I engage on highway when speedometer needle is showing 75 the indicator will show 77. just wondering if others have noticed a difference or if there is any adjustment for this.
thanks

[AmazinglySmooth]

I noticed this too. I also compared the speedometer to my GPS. I think the speedometer is 2MPH faster than the GPS and the cruise speed is 4MPH faster than the GPS. Who is right?

[DNA Dan]

Good to know I'm not the only one. I originally posted about this over a year ago here: 2010 Platinum issues - Does yours do this? at which time some members felt I was just "nit-picking". The 2mph difference is real, and who knows which one is correct. Toyota can't tell me. I personally think they did not re-program the computer in these models for the larger tires on the platinum. (unless someone has a limited or SR5 that does this?). It's worse with the DLCC because you can only jump by 5 mph at a time. So if you want to go 65 and set it for that, you're stuck going 63. If you set it for 70, you're going 68. PITA! or Should be a simple fix, but Toyota doens't give a **** now that they have your money.

[AmazinglySmooth]

Good to know I'm not the only one. I originally posted about this over a year ago here: 2010 Platinum issues - Does yours do this? at which time some members felt I was just "nit-picking". The 2mph difference is real, and who knows which one is correct. Toyota can't tell me. I personally think they did not re-program the computer in these models for the larger tires on the platinum. (unless someone has a limited or SR5 that does this?). It's worse with the DLCC because you can only jump by 5 mph at a time. So if you want to go 65 and set it for that, you're stuck going 63. If you set it for 70, you're going 68. PITA! or Should be a simple fix, but Toyota doens't give a **** now that they have your money.

The only speed that matters is the one the police officer's radar says. I think that a slower speed serves two purposes: 1) it slows you down unless you know the real delta so Toyota's safety ratings go up, and 2) Toyota owners will get less speeding tickets.

[srock]

There is another issue. The warranty is not accurate or the resale mileage. Multiply this over the number of vehicles sold it is very significant...a 3-4% reduction in warranty claims.

[robbyvaughn]

You know there is no right answer for a designer when it comes to the laws, customer expectation and actual conditions. In the US, speedometers are allowed +/-5mph at 50mph and that's the only speedo regulation there is. This means one car can be traveling 45 when it reads 50 and a second car can be going 55 when the speedo reads 50 and both are perfectly "legal". That's a big allowed +/-10% error.

Obviously customers expect better so designers have to make some hard calls. On a typical set of Dueler HL's on a Plat Sequoia, Bridgestone claims a dead nuts 32" diameter at 32psi. Tread depth when new is 12/32". US laws also place the legal lower limit on tread depth at 1.6mm. So, brand new these tires are 32" in diameter and when worn they are 31.375" in diameter. You drop that much in diameter over the tread life of the tire. Assuming you keep your tires at 32 psi ever day and they never heat up or get driven in cold weather, your speedometer is automatically going to change 1.95% from the time you drive off the lot until you need to pull your wallet out and spring for new shoes. That's a 1.95% INCREASE in indicated speed. Now throw in the fact that MOST people will only check their tire pressure when the TPMS goes off or someone else does it for them during oil changes and the fact that it gets pretty cold in the northern part of the US and Canada and there has to be fudge factors/assumptions made for these "real world" conditions.

Remember also, tires have tolerances as well. That 275/55/20 Dueler might really be 32.1 or 31.9 at 35psi or if you opt for the higher quality Michelin LTX 275/55/20, they like to set final diameter at 31.9" so there's another error to deal with.

If you were a designer, where would you put the calibration sweet spot? Make the thing perfect with a 32" tire at 32 psi on a 70F San Diego afternoon? You made yourself open to some heavy liability from the customer with 60K on the clock in Alberta on January 23rd when he gets his first speeding ticket at the end of his street in the morning.

On top of all this, throw in the odometer accuracy issue. Basically the odometer is way more accurate than the speedo needle due to ever so friendly lawyers and the whole Honda lawsuit of a few years back (2004 maybe) even though the existing official 1972 FOA has no provisions for accuracy. The Sequoia's odometer gets and processes the raw speed signal and there's some nice software in there making all kinds of allowances. The speedo needle on the other hand is subject to error from the stepper motor translation and view angle. The trucks are designed to be viewed by a 50th percentile male driver. I'm 6'5" so I would observe a different speed from my seating position than Mr. 50 and yet even more different from my 4'11" wife with her seat full forward. Set your cruise on 65 and move around in your seat while looking at the needle. Again, the designers MUST make certain assumptions. Another reason your laser cruise might look different than the needle. The cruise control ECU is pulling raw speed data from the engine ECU and displaying the results in the MID which does not have the needle issues to deal with.

Of course this all became blown up when GPS set the stage for real time side by side comparison. Every one seems to assume GPS sets the standard, but remember, GPS has tolerances too and they are not as good as TomTom and Garmin would have you think. Just as the higher placement accuracy is reserved for the military, so are the tolerances on speed. Manufactures use different signal processors, look at a different number of reference sats (channels) and have different algorithms for averaging speed. Do you display instant speed, average over 5 seconds, 10 second, RMS output, etc. And then there is the effect from elevation. It has an affect and will differ if you're in Tampa or Denver. I've personally done an evaluation using seven different GPS units and they gave an eye opening result. Max difference, 9 mph from the slowest indication to the fastest.

So, that 2 mph difference still seem so bad?

[jschmank]

Interesting discussion, never really thought about it much before. However, I must say I have never had another vehicle that had this discrepancy before either.

[DNA Dan]

I think you're missing the point. Sure speeds will vary in practice from what a speedometer is set to. I completely understand where you're coming from. The issue we're seeing is if you set the CRUISE CONTROL to 60, it actually locks the speedo at 58. In other words, there is a discrepancy in the design of the car where the cruise control is either not properly calibrated or the speedometer doesn't stop upon initiating the cruise control. So the question becomes, is the cruise control lying to me? or is the speedometer?


By your 2% variation analysis (very well done I might add.) that means we are +/- 4% based on the cruise control, and probably +/- 2% based on the speedometer since that more accurately tracks the speed of the vehicle. I don't know where the cruise control speed setting comes from.

[paulyd44]

My 2011 Platinum speedometer and Laser Cruise are not in sync. I was told by the dealer it was in tolerance. Definitely a design flaw. I just deal with but I don't like it.

[txpackers]

I noticed the same thing. The digital reading for the cruise control is always 2 - 3 MPH faster than what the needle indicates. The other day my wife and I drove to San Antonio separately (she followed me in our Honda). Interstate speed limit was 70 MPH so I set the digital reading for 74 MPH (didn't use the laser cruise). She was always lagging way behind me which is not typical since she usually drives about 3 - 4 MPH over the speed limit. When we got there she asked me why I was going so fast. She had the cruise in the Honda also set at 74 MPH and I was pulling away from her. So the Sequoia's 74 was faster than the Honda's. So I'd say both vehicles may be showing a different speed from actual, but are definitely within their tolerances.

I've always found the best way to check your speedometer is to find one of those highway "check your speed" signs where a radar gun is set up with a digital display to show your actual speed. Set your cruise at your desired speed and drive by one of those to see what it says. I did it recently with the Sequoia and it was within 1-2 MPH of the display. I don't remember which one was higher, but it was so close that the mental note I made was that the digital reading on the speedometer is accurate.

[lvrouter]

On my 2012 Platinum, the laser cruise control, when set anywhere from 65 to 80, matches EXACTLY with multiple GPS units I have compared it to, it's spot on almost all the time (hills excluded). However, the speedometer needle always appears 2-3 mph lower than the set speed. I understand the parallax error but I really have to sit in a strange, wierd place to get the needle to match. I don't think it's set properly for ANY person of any height. The good news is that the cruise control is accurate (although like all Toyotas I've owned much to aggressive) the needle variance is just annoying to an OCD individual like myself.

[DNA Dan]

Any of you guys talk to toyota about it? This seems like a straightforward fix if they would just issue the TSB and reprogram the computer on these cars. Every other car I have driven "locks" the cruise control where you stop it. Yet Toyota can't get this right on a 60,000 dollar vehicle? \

Mine drops the needle back 2 mph just like other have stated. The nuissance for me is using the DLCC. If I want to toggle the speed up or down, it only moves by 5 mph increments. If you bump it to 65, speedo is 63. If you bump it to 70, speedo is 68. I either constantly gain on people, or have them gain on me. Annoying.

[sks1127]

Only thing positive about it is that I can bump the cruise up to 80 and it has me going 78, which happens to be the speed I like to cruise at. I just feel less likely to get stopped on long road trips going 78 rather than 80+. Perhaps it's stupid to think that but several other people I travel with all have the same mentality.

[Ali_q8t]

Only thing positive about it is that I can bump the cruise up to 80 and it has me going 78, which happens to be the speed I like to cruise at. I just feel less likely to get stopped on long road trips going 78 rather than 80+. Perhaps it's stupid to think that but several other people I travel with all have the same mentality.

I think your actually going the cruise control speed. The speedometer shows a lower speed than actuall speed so of your showing 78 on speedo your actually going 80 or more. On 20 in rims Toyota specialist told me could be a +5mph variance. So double check your actual speed with a gps or those speed monitors another member was talking about.

Specialist also told me it can't be adjusted.

A bit weak for a 55k ride.

[sks1127]

Well that's good to know, I'll have to check that out.