Hi all I've notice on my tongsheng tsdz8 conversion that the speed on my display reads a bit high compared to my Garmin. This means the motor cuts out before a true 15.5 mph. Ive set the wheel diameter at 700 on the settings.

Would moving the sensor make any difference. IE moving it out further or in to increase/ decrease the actual diameter the sensor works.

If that all makes sense.

TIA

Hi all I've notice on my tongsheng tsdz8 conversion that the speed on my display reads a bit high compared to my Garmin. This means the motor cuts out before a true 15.5 mph. Ive set the wheel diameter at 700 on the settings.

Would moving the sensor make any difference. IE moving it out further or in to increase/ decrease the actual diameter the sensor works.

If that all makes sense.

TIA

Moving the sensor won't make any difference. It will still get one pulse per rotation.

No, the sensor will be counting revolutions. You could try a different wheel diameter setting. If you set it to 26" wheel if will think you are going a little slower than it thinks with a 700c setting.

Moving the sensor won't make any difference. It will still get one pulse per rotation.

Ah ok thank you

No, the sensor will be counting revolutions. You could try a different wheel diameter setting. If you set it to 26" wheel if will think you are going a little slower than it thinks with a 700c setting.

Ok thank you

One thing I notice is that if you actually measure many wheels (including the tyre)with a tape, they measure smaller than the nominal size, depending on the tyre size. e.g, 26 wheels with the Kenda 26 X 1.95 mtb tyres measure up at 25.5 inches and 700c wheels with thinner 28mm tyres are 680mm or less and are less than 27 inches .

Edited December 22, 2025Dec 22 by Sturmey

One thing I notice is that if you actually measure many wheels (including the tyre)with a tape, they measure smaller than the nominal size, depending on the tyre size. e.g, 26 wheels with the Kenda 26 X 1.95 mtb tyres measure up at 25.5 inches and 700c wheels with thinner 28mm tyres are 680mm or less and are less than 27 inches .

Yes. It's a nonsense when controllers only give you a choice of things like 26" or 700c.

Wheel sizes got silly for perfectly understandable historic reasons. (difference between 26x1.5 and 26x1 1/2)

They almost became sensible with ETRTO, and then the marketing people got in and invented lots of other nonsense names like 29", primarily to add a fashion element to wheel size and persuade people they needed a new bike.

Hi all I've notice on my tongsheng tsdz8 conversion that the speed on my display reads a bit high compared to my Garmin. ........

TIA

• So what's a bit high and does it really matter that much to you?
  
• Checking speed between devices (ie Garmin/TSDZ8) is never straight forward as the devices will have their own sampling and update rates
  
• When setting up a KT system, to check accuracy I temporarily fitted an 'old school' Cateye cycle computer (that works with a wheel magnet). You then measure the distance rolled by one revolution of the wheel and enter this into the cycle computer - this gives you what is probably the most accurate speed (and distance) compared to the TSDZ and Garmin.
  
• After a 100Km ride there was only 0.5Km difference in distance between the KT-LCD and the Cateye, so more than happy.
  
• I've also done this with my TSDZ2 conversion and TBH I've left the Cateye in place as it's more easy to use and read that faffing with the VLCD6 that I use.
  
• I noticed from the Endless Sphere forum that there is Open Source Firmware (OSF) for the TSDZ8 in which like the OSF for TSDZ2, you can enter precidelsy the wheel circumference like you can in the Cateye, but going that route (OSF) is a big step for what may be minor speed differences.
  

• So what's a bit high and does it really matter that much to you?
  
• Checking speed between devices (ie Garmin/TSDZ8) is never straight forward as the devices will have their own sampling and update rates
  
• When setting up a KT system, to check accuracy I temporarily fitted an 'old school' Cateye cycle computer (that works with a wheel magnet). You then measure the distance rolled by one revolution of the wheel and enter this into the cycle computer - this gives you what is probably the most accurate speed (and distance) compared to the TSDZ and Garmin.
  
• After a 100Km ride there was only 0.5Km difference in distance between the KT-LCD and the Cateye, so more than happy.
  
• I've also done this with my TSDZ2 conversion and TBH I've left the Cateye in place as it's more easy to use and read that faffing with the VLCD6 that I use.
  
• I noticed from the Endless Sphere forum that there is Open Source Firmware (OSF) for the TSDZ8 in which like the OSF for TSDZ2, you can enter precidelsy the wheel circumference like you can in the Cateye, but going that route (OSF) is a big step for what may be minor speed differences.
  

The difference is quite big I think I was out today and the difference in speed is 0.7 mph so the display is reading 0.7 mph faster than the garmin which works off satellite.

It's not a great problem but but I was just wondering if moving the

One thing I notice is that if you actually measure many wheels (including the tyre)with a tape, they measure smaller than the nominal size, depending on the tyre size. e.g, 26 wheels with the Kenda 26 X 1.95 mtb tyres measure up at 25.5 inches and 700c wheels with thinner 28mm tyres are 680mm or less and are less than 27 inches .

Im currently running 700× 38 tyres. I haven't yet measured the diameter.

The difference is quite big I think I was out today and the difference in speed is 0.7 mph so the display is reading 0.7 mph faster than the garmin which works off satellite.

It's not a great problem but but I was just wondering if moving the

 

Im currently running 700× 38 tyres. I haven't yet measured the diameter.

Why not set the LCD to 16.2mph?

Why not set the LCD to 16.2mph?

Never thought of that. I'll give it ago