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Speedometer is off big time after changing front sprocket to 14T

H

HyperstradaHopeful

Joined Jan 2014
215 Posts | 0+
California
Just had the 14T front sprocket installed today and noticed that the speedometer is VERY off. Up to 50mph, according to my GPS, it's only about 2mph off, which is normal. But while cruising at 65mph, my GPS said I was doing 60mph... that's 5mph off and pretty huge! I haven't gone passed 65mph since installing the sprocket but if it goes from being 2mph to 5mph off with just a 15mph increase, I can only imagine what it's going to be like at faster speeds. When the bike says I'm doing 100mph, am I really only doing 88mph?

Has anyone else had this problem when going to the 14T front sprocket? And more importantly, is there any fix for it? Can Ducati update the software and tell the bike that it has a 14T front sprocket now instead of a 15T?
 
Back in the day, speedo error would get you out of a ticket once. Had to get it calibrated then show judge.
 
Thanks, R6! Looks like what I need. But I did a Google search and can't find one for Ducati. All the ones coming up on eBay for Ducati say "NON ABS only" and obviously the Hyperstrada has ABS.

Any ideas?
 
Check their website. I saw one there for my old R6 (which was 10% optimistic as delivered), but haven't tried looking for a Ducati one as the error is only about 4%.

The difference is easy to calculate, 15/14*100 = another 7% of error. That's way more than I would like. At least on the R6 you could ride by the tach in top; 6000 rpm = 60 mph. Not sure why you needed to make the change, I try to find seventh gear enough as it is.
 
Did you check to speedo before you installed the 14t cog ?

In the UK they need to within 10% lower, but no higher. Every car or bike I have owned or hired has had the speedo think its faster than the GPS speed reading.
 
I thought our bikes used the ABS signal for the speed reading, meaning that a sprocket change would make no difference?

Edit: found this older post of mine...

>I assume that with all the hi tech, the speedo should be accurate...

Well, it isn't. The manual even states that the ECU takes the computed value and adds 5%. And I think it's off closer to 7% but have my yet confirmed.

I read an article a couple of years ago that claimed that European regs dictate that a speedometer can never real lower than actual, for any 'reasonable' wheel and tire combo that an owner might put on. So they look for the dumbest over-profile tire someone could fit and figure the error from that case.
 
Last edited:
jamiesk said:
Did you check to speedo before you installed the 14t cog ?

In the UK they need to within 10% lower, but no higher. Every car or bike I have owned or hired has had the speedo think its faster than the GPS speed reading.
Click to expand...

Every Harley I've ever seen has an accurate speedo. Even says "certified" right on the face. That included my Buell, but without the marking. And both of our Mazdas ('13 MX-5 Club and '14 Mazda3) are similarly accurate, to one mph. So it can be done. Perhaps this is a trend.

Back when the USA had a 55 mph national speed limit, and speedos could not read higher than 85, there was an accuracy requirement. I had a couple of SR500s and a Rabbit (Golf) GTI that had perfectly accurate speedos then. But when they dropped the speed limit and speedo marking laws, they threw out the accuracy requirement as well. Bastids!
 
porkrind said:
I thought our bikes used the ABS signal for the speed reading, meaning that a sprocket change would make no difference?

Edit: found this older post of mine...

>I assume that with all the hi tech, the speedo should be accurate...

Well, it isn't. The manual even states that the ECU takes the computed value and adds 5%. And I think it's off closer to 7% but have my yet confirmed.

I read an article a couple of years ago that claimed that European regs dictate that a speedometer can never real lower than actual, for any 'reasonable' wheel and tire combo that an owner might put on. So they look for the dumbest over-profile tire someone could fit and figure the error from that case.
Click to expand...

Where is that statement in the manual? I believe you, but I haven't seen it. The EU has come up with some pretty weird regs; the UK members of my old Brit bike forums get pretty exercised about some of their proposals.

Hard to believe that there is a street tire that is 5% taller that fits the Strada. I don't think they were considering full knobs with ice screws! My Q3 rear is about 1% taller, and if you went with a 190 it would be a 50 instead of 55 so there would be no difference. And if it is ABS-driven, what different front tire would be so much taller?
 
zippy49 said:
Where is that statement in the manual? I believe you, but I haven't seen it.
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Page 31
ScreenShot2014-02-15at112133AM.png
 
Here's Wikipedia's take...

Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter.[citation needed] Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers [8] [9][10] are similar to the UNECE regulation in that they specify that:
The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.
Click to expand...
 
Unless something drastically changed with the Hyperstrada, the speedo uses tire rotation to determine speed so front sprocket would not affect speedo reading at all.

And yes, the speedo does read higher than actual speed because it's completely non-compliant with regulations for it to under report. Once I'm above 40MPH, mine Duc's speedo is usually showing 5MPH faster than actual speed.
 
Pinoybear said:
Unless something drastically changed with the Hyperstrada, the speedo uses tire rotation to determine speed so front sprocket would not affect speedo reading at all.

And yes, the speedo does read higher than actual speed because it's completely non-compliant with regulations for it to under report. Once I'm above 40MPH, mine Duc's speedo is usually showing 5MPH faster than actual speed.
Click to expand...

Interesting and good to know! But why does Ducati set it so much over what it actually is? I like to drive right at 10mph over the speed limit. So if it's showing 5mph faster than actual speed, I could actually be going 5mph more without risking a ticket (here in CA, they don't ticket you in the area I live for 10mph or less over the limit... drive right passed cops with radar guns drawn at 10mph and they do nothing). So do I go 15mph over the limit, according to the speedo? Well, no, because it's variable and might show 5mph more when doing 60mph but only shows 2mph more when doing 40mph. So I don't know what it really is without also looking down at the tiny GPS speed indicator.
 
The speedo uses tire rotation to determine speed so front sprocket would not affect speedo reading at all.
 
HyperstradaHopeful said:
Interesting and good to know! But why does Ducati set it so much over what it actually is? I like to drive right at 10mph over the speed limit. So if it's showing 5mph faster than actual speed, I could actually be going 5mph more without risking a ticket (here in CA, they don't ticket you in the area I live for 10mph or less over the limit... drive right passed cops with radar guns drawn at 10mph and they do nothing). So do I go 15mph over the limit, according to the speedo? Well, no, because it's variable and might show 5mph more when doing 60mph but only shows 2mph more when doing 40mph. So I don't know what it really is without also looking down at the tiny GPS speed indicator.
Click to expand...

Just look in your owners manual. It gives you the % that the speedometer is off by. Which is also why it's not a set number over.
 

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