Ducati.org forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter #1 (Edited)
noticing my 2012 796 the speedo reads high ie: 90 kph reads as 100kph. owners manual page 20. on speedo illustration and operation says that 8% is added to read-out.
i cannot under stand why they would purposely engineer that?:confused:
 

·
Registered
Joined
·
270 Posts
Install a Healtech Speedo healer. It's a direct plug in. Double check on its application if you have ABS.

I'm drawing a blank on a truly good reason to have the speedometer read high from the factory, as time in corners already changes the read due to the smaller circumference the sides of the tires. My guess is they can get you in 8% sooner for over priced services.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #3
i think it it saved me a couple of times , were i thought i was speeding 15- 20 kph over the posted speed limit , but the cop didn't seem to be bothered. maybe ill just add 5-10 in my head. just seems odd why it would be set up that way??
 

·
Registered
Joined
·
1,216 Posts
The design of motor vehicles offered for sale in a particular country is regulated by its government. So, to meet the requirements of markets around the world, Ducati designs their products to meet as many countries regulatory requirements as possible. Still, some requirements such as lighting or exhaust emissions require country-specific models to be designated.

Most countries specify a legal requirement that speedometers cannot indicate a speed lower than the actual speed of a vehicle. Otherwise, in speeding violation cases, the responsibility could be shifted from the operator to the manufacturer.

Suppose for a moment that Ducati was at liberty to decide that your new bike would have a extremely accurate speedometer; one that read 40 mph when you were moving at exactly 40 mph. As you speed up to 80 mph, at the higher rotational speeds the tire diameter grows due to centrifugal force, the rear wheel pick-up or front wheel speedometer drive registers fewer rotations per mile, and the speedometer error increases, that is, it reads lower by a greater amount. GPS measurement have shown that you’ll get about a 4% error or about 3 mph. Because your speedometer reads 77 mph, you speed up to 8o mph thinking you remain at a legal speed.

As a complication, pretend that you’re riding a 748 that comes from the factory equipped with 120/60Z17 tires. You’ve decided that you like the handling of the 120/70Z17 profile better, so you switched over. The 120/70Z17 profile tire is used on the 916 which uses the same speedometer as the 748.

Michelin Pilot Power 120/60Z17 rolling diameter =586 mm
Michelin Pilot Power 120/70Z17 rolling diameter =612 mm

C=πD, 612/586=1.04, so you get 4% more wheel rotations per mile with a 60-section tire. (Different numbers for different tires.)

By changing from a 70-section to a 60-section tire, the front wheel will now rotate 4% faster so the speedometer error is an additional 4% low so you speed up an additional 3 mph. Tire wear will increase this error.

Over the next hill you encounter a radar trap and they get you for riding 86 mph in a 80 mph zone.

Is Ducati responsible for your ticket? Are they libel in a potential class action suit? Have they taken the proper steps to prevent foreseeable circumstances from causing you to get a ticket?

http://en.wikipedia.org/wiki/Speedometer#Error
 

·
Registered
Joined
·
16 Posts
Discussion Starter #6
ok, great info, well at least they inform the owners via the manual so the can choose to make modifications if they wish. yes excellent explanation thank-you.
 

·
Registered
Joined
·
4 Posts
European regulations state that indicated speed cannot be less than actual speed but not more than 110% of actual speed + 4km/h:

https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf

The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).
0≤(V1 -V2)≤0.1V2 +4km/h
 

·
Registered
Joined
·
6 Posts
On my 696 Monster I once read the speed shown on the bikes speedometer is 7% over true speed. Many towns around where I ride have radars showing your speed as you're riding by and speed posted on these devices is consistently lower than what speedometer shows.
 

·
Registered
Joined
·
90 Posts
Speed reads on the back tire.
The front tire ratio has nothing to do with speed reading .
You could pop a wheelie and your front wheel stopped in the air and still recording speed.

Having said that,
My 1098 is 7% off.
Speedo says 140... And I'm doing 130 kph.


The design of motor vehicles offered for sale in a particular country is regulated by its government. So, to meet the requirements of markets around the world, Ducati designs their products to meet as many countries regulatory requirements as possible. Still, some requirements such as lighting or exhaust emissions require country-specific models to be designated.

Most countries specify a legal requirement that speedometers cannot indicate a speed lower than the actual speed of a vehicle. Otherwise, in speeding violation cases, the responsibility could be shifted from the operator to the manufacturer.

Suppose for a moment that Ducati was at liberty to decide that your new bike would have a extremely accurate speedometer; one that read 40 mph when you were moving at exactly 40 mph. As you speed up to 80 mph, at the higher rotational speeds the tire diameter grows due to centrifugal force, the rear wheel pick-up or front wheel speedometer drive registers fewer rotations per mile, and the speedometer error increases, that is, it reads lower by a greater amount. GPS measurement have shown that you?ll get about a 4% error or about 3 mph. Because your speedometer reads 77 mph, you speed up to 8o mph thinking you remain at a legal speed.

As a complication, pretend that you?re riding a 748 that comes from the factory equipped with 120/60Z17 tires. You?ve decided that you like the handling of the 120/70Z17 profile better, so you switched over. The 120/70Z17 profile tire is used on the 916 which uses the same speedometer as the 748.

Michelin Pilot Power 120/60Z17 rolling diameter =586 mm
Michelin Pilot Power 120/70Z17 rolling diameter =612 mm

C=πD, 612/586=1.04, so you get 4% more wheel rotations per mile with a 60-section tire. (Different numbers for different tires.)

By changing from a 70-section to a 60-section tire, the front wheel will now rotate 4% faster so the speedometer error is an additional 4% low so you speed up an additional 3 mph. Tire wear will increase this error.

Over the next hill you encounter a radar trap and they get you for riding 86 mph in a 80 mph zone.

Is Ducati responsible for your ticket? Are they libel in a potential class action suit? Have they taken the proper steps to prevent foreseeable circumstances from causing you to get a ticket?

http://en.wikipedia.org/wiki/Speedometer#Error
 
1 - 10 of 10 Posts
Top