+6 mph???

Slow News Day?


Sent from my iPad using Tapatalk

BCKRider said:

I think it would be a good idea to know how fast you are going rather than having to guess. But I just try to follow the speed of traffic - which I am sure is sometimes WAY above the posted speed limit. Safety first. Legality - well don't be the fastest one down the road.

Click to expand...

I always try to have a rabbit

My RT is +5 which I think has saved me from tickets.

I used to accept that all speedometers were off by 10%...till I bought my Honda NT700V. It's spot on.

Plus, it has a speedometer that is readable.

Chris

daboo said:

I used to accept that all speedometers were off by 10%...till I bought my Honda NT700V. It's spot on.

Plus, it has a speedometer that is readable.

Chris

Click to expand...

Same thing with my 2012 Gold Wing - follows GPS to the number.

Perhaps, HONDA 'didn't get the memo.'

Others have commented on the 85 mph speedometers seemingly being more accurate. I think it is just a matter of having more graduations between the numbers, since the whole scale on the speedometer face is expanded. The inaccuracy gets spread over a larger area and becomes less noticeable. The SAE J862 spec has long governed speedometer accuracy and I don't believe there was a revision made for the Carter era speedometers. Having said that, the speedometer inaccuracy has always bugged me. The manufacturers could do better but, with few exceptions, don't.

swall said:

Others have commented on the 85 mph speedometers seemingly being more accurate. I think it is just a matter of having more graduations between the numbers, since the whole scale on the speedometer face is expanded. The inaccuracy gets spread over a larger area and becomes less noticeable. The SAE J862 spec has long governed speedometer accuracy and I don't believe there was a revision made for the Carter era speedometers. Having said that, the speedometer inaccuracy has always bugged me. The manufacturers could do better but, with few exceptions, don't.

Click to expand...

Gotta love SAE. Locks down every spec and paper.......then wonders why very few researchers reference their products.

Can you para-phrase what J862 says? Non-SAE members can't access SAE papers or pubs.......

SAE J862 pertains to both odometer and speedometer accuracy. I'll stick with the speedo part. There is a table (Figure 2) that summarizes 8 sources of inaccuracy, such as tire size variation, centrifugal effects, tire load effects, tire inflation, etc. The table gives the indicated mph variation compared to actual. This is reference information, not performance limits. For performance limits, J862 refers you to SAE J678. Paragraph 2.4 of J678 gets into speed indication, and there is a table (Table 1) that shows true speed vs indicated speed. True speed is calculated from the RPM of the drive cable. For true speed of 60 mph, the instrument is allowed to read 60-63 mph. For True speed of 30 mph, the instrument is allowed to read 30-33 mph. 90mph and 10 mph limits are also given. Then there is a spec (SAE J1059) that covers allowable variation after a 25,000 mile test of the speedometer. The instrument is required to read within 3% of the limits listed in Table 1 of spec J678. Keep in mind that these values are for the instrument on a test bench. You still have to consider the factors listed in Figure 2 of J862 that are additional factors that related to how the instrument performs on the actual vehicle. You do not have to be an SAE member to obtain these specs, but you do have to pay for them. If I recall, they run somewhere in the $25 range for a paper copy. If you buy a spec, it is on you to check down the road for spec updates that may have occurred.

If the speedometer is off does that mean the odometer is off too?

jnrugg said:

If the speedometer is off does that mean the odometer is off too?

Click to expand...

Yes.

Just picked up my 2016 RT and the speedo is very close to the GPS.

The inputs for the speedometer and odometer from the take off point (i.e. the drive gearing from the transmission) start out the same. The drive line related sources of error, such as tire size and tire condition are the same. But, the odometer is a train of gears and tumbler wheels all hard coupled. The odometer display is discrete, i.e. specific numerals on the mechanically driven tumblers. The speed display part of the instrument uses a rotating magnetic disc coupling to drive the pointer needle. The needle itself is under the force of a torsion spring. There are provisions for adjusting the spring torsion and the pointer needle hard stop points, which affect accuracy. You also have parallax errors in reading speed from the instrument face. So, you can have a very accurate odometer and a widely inaccurate speedometer.

never even thought of THAT!

jnrugg said:

If the speedometer is off does that mean the odometer is off too?

Click to expand...

jnrugg said:

If the speedometer is off does that mean the odometer is off too?

Click to expand...

Post #13. Item 2.

My 2016 speedometer reads 81 when the GPS reads 78.

The odometer reads 100 miles when the GPS hits 101, so it's very close.

26667 said:

Click to expand...

Oh yeah! I brought that up to my BMW dealer when the '36,000 mile' warranty expired on my R1200RT before my 3 years were up, which really only had 33,500 miles on it, due to a 7% margin of error, as verified by GPS.

He just shrugged and said "Oh well - can't fight City Hall (in Berlin)."

Some days, you're the pigeon ............... some days, you're the statue.

mileage awards

greenwald said:

Oh yeah! I brought that up to my BMW dealer when the '36,000 mile' warranty expired on my R1200RT before my 3 years were up, which really only had 33,500 miles on it, due to a 7% margin of error, as verified by GPS.

He just shrugged and said "Oh well - can't fight City Hall (in Berlin)."

So...some of those mileage awards are ...??? undeserved?

and what about IBA people? Do your miles match up between ODO and the IBA route?

where's the emoticon for "can of worms?"

Click to expand...

I have a Super Tenere that has a device called a Speedohealer installed by the original owner. It allows manipulation of the speedometer so that one can make it read dead accurate according to a GPS. I've found that correcting for the +5 MPH speedometer error at 70 MPH makes the odometer go from accurate to -3 miles every 100 miles.

rangerreece said:

We did a whole thread on this a couple of months ago. It was informative. Bottom line, the speedos are up to 10% higher than actual speed by design.

Click to expand...

HA! Does this explain why my R100RS looks like its going fast even when it's sitting still?

ricochetrider said:

HA! Does this explain why my R100RS looks like its going fast even when it's sitting still?

Click to expand...

That might very well explain it.

Wussies, you ought to see the dance my speedo needle does on my Ural between 55 and 70. Below 55 and it's dead on, based on the speed limit signs that give feedback. Above 55 and especially 60 the dances all over the place, continuously.

My GSA speedo appears pretty accurate, again based on speed limit signs that flash your speed back at you. Haven't head the courage to push it up to 100 mph just to see what the sign says...