Last time we had our digi tacho recalibrated I lost speed on the limiter, I often travel in a convoy of several trucks and this made me the slowest, sat nav said I’d dropped from 89/90 to 88, not much but on a 3 day trip through Europe it adds up. Now I’ve just had it done again and it’s dropped to 87 on the sat nav which means I’m going to be really popular the next time we’re all travelling together. My question is, am I within my rights to complain and ask for it doing again?
Good point Jay. Problem being if it is NOW perfectly calibrated and was reading wrong the previous times.
To the op I doubt (unless you’re prepared to pay for it yourself) that anything could be done now. Next time it’s due just make sure you take it with bald drive axle tyres. In the meantime maybe you should lead the convoy, less stressful for you chasing your arse, and it makes it easy for the ones following too.
tacho calibration is done with calibrated rollers which measure tyre diameter ,and a handset plugged in to the tacho which measures pulses from the sender …,It calculates the K & W factor and automatically sends it to the tacho head …The person calibrating just sits in the cab and presses the throttle,and has no control over the measurement of the tyre or the K & W if done legally…Tyre pressure and tyre wear affect the setting …I have heard of people who put part worn tyres on the vehicle then after calibration fit new tyres …Also a speed for speed check is carried out after calibration to check the vehicle and tacho calibration tool are the same …Also now the stoneridge tool can carry out a 1000m test ,which it must pass…Just because the sat nav says 85 ,doesn’t mean the vehicle says 85 ,like everything there are tolerances…My car doesn’t agree with the sat nav ,but I personally don’t know of any vehicles that do…
I cant really see the tacho centre being at fault …Everything is calibrated
if out of calibration they are in deep do do …as I mentioned earlier once calibrated they do a speed for speed check so if vehicle is showing 50kph for example ,then the stoneridge calibration tool should also show 50 kph ,and you also have the plus minus you are allowed…
I’ve had one vehicle I calibated and the K and W factor didn’t make sense…turned out it was right as the operator had changed the diff…Your K , W and L will be different on every 2yearly recal …if you do a vehicle tech data print out, you will see each calibration it has had and all the K,W L factors and they re all different
I have a similar problem on one of my lorrys, it is forever saying overspeed on the flat but im often overtaken by other lorrys, it had a new exact tacho put in and somethings not right. If its a twin wheeled drive axle do you have to turn up at the recalibration centre with both wheels on or can you go with one wheel on each side, don’t fancy changing 4 tyres over to worn ones then change back again.
it only measures 1 tyre…the one you see the reflective tape on it…but to be honest I wouldn’t know if you would have to change all the tyres.you would definitely have to do the 1st drive.it isn’t something I really think about,as long as they are legal and inflated ,the tyre is your L factor and will be on the plaque in mm…so when running vehicle up everytime the reflective tape passes a sensor It is measuring the tyre
Last time we had our digi tacho recalibrated I lost speed on the limiter, I often travel in a convoy of several trucks and this made me the slowest, sat nav said I’d dropped from 89/90 to 88, not much but on a 3 day trip through Europe it adds up. Now I’ve just had it done again and it’s dropped to 87 on the sat nav which means I’m going to be really popular the next time we’re all travelling together. My question is, am I within my rights to complain and ask for it doing again?
No. Legally they are required to set the speed limiter to 85kph.
It wasn’t the digi tacho recalibration that lowered the speed but the speed limiter recalibration.
norb:
it only measures 1 tyre…the one you see the reflective tape on it…
It only needs to. The tyre with the least tread will be the one rotating the fastest and therefore the one which will have the most impact on the speed the speedo/tacho shows. The tread depth is factored into the readings.
norb:
it only measures 1 tyre…the one you see the reflective tape on it…
It only needs to. The tyre with the least tread will be the one rotating the fastest and therefore the one which will have the most impact on the speed the speedo/tacho shows. The tread depth is factored into the readings.
I might not be following this but it doesn’t sound right at all. The L factor remains whatever it was at calibration. The sender will count the revolutions from the gearbox and assume the vehicle has travelled whatever distance it did when it last went on the calibration rig.
The l factor is just the circumference of the tyre and changes with tread depth, tyre pressure and axle load. This is why the vehicle is meant to be unladen and the tyre pressures checked before calibration. It’s not a totally exact science as you can run the same vehicle up twice and get two different results albeit only a tiny difference.
Last time we had our digi tacho recalibrated I lost speed on the limiter, I often travel in a convoy of several trucks and this made me the slowest, sat nav said I’d dropped from 89/90 to 88, not much but on a 3 day trip through Europe it adds up. Now I’ve just had it done again and it’s dropped to 87 on the sat nav which means I’m going to be really popular the next time we’re all travelling together. My question is, am I within my rights to complain and ask for it doing again?
No. Legally they are required to set the speed limiter to 85kph.
It wasn’t the digi tacho recalibration that lowered the speed but the speed limiter recalibration.
Legally the max limiter is 90 km/h. They can set it at anything UP to 90 km/h.
If your tacho was calibrated you may get a change in INDICATED speed, but the limiter calibration will change the actual speed. If you get both done together though…
Last time we had our digi tacho recalibrated I lost speed on the limiter, I often travel in a convoy of several trucks and this made me the slowest, sat nav said I’d dropped from 89/90 to 88, not much but on a 3 day trip through Europe it adds up. Now I’ve just had it done again and it’s dropped to 87 on the sat nav which means I’m going to be really popular the next time we’re all travelling together. My question is, am I within my rights to complain and ask for it doing again?
No. Legally they are required to set the speed limiter to 85kph.
It wasn’t the digi tacho recalibration that lowered the speed but the speed limiter recalibration.
speed limiter has nothing to do with the tacho ,the speed limiter is programmed in to the engine ecu and can not be altered by tacho calibration equiptment
