70mph in top gear???

[Paulfzs]

[quote author=Paulfzs link=topic=16362.msg188455#msg188455 date=1427286766]
got a phone? attach it to the bike so you can see it and install a speedo app

Done that. My speedo cheats around 3-4% up.
[/quote]


most speedos read slightly wrong, id trust my phone gps over the speedo any day

[rhinoeli]

Of course GPS is way more precise.


What irritates my mind is the thing that many say their bike runs over 6000 rpm at 70 mph. Referring to the calculations above, 70 mph should be at around 5600 rpm. This is almost 10% difference. Tacho and speedometer should be more precise. In fact his speedo has to show less than the reality, which is not typical. Or the tacho has to show more than reality, which... yeah, we should test it with a proper rpm measuring device.


Might worth some experimenting on this topic in the future...

[midden]

Of course GPS is way more precise.


What irritates my mind is the thing that many say their bike runs over 6000 rpm at 70 mph. Referring to the calculations above, 70 mph should be at around 5600 rpm. This is almost 10% difference. Tacho and speedometer should be more precise. In fact his speedo has to show less than the reality, which is not typical. Or the tacho has to show more than reality, which... yeah, we should test it with a proper rpm measuring device.


Might worth some experimenting on this topic in the future...

I bet you're mates have fun winding you up 

[quote author=midden link=topic=16362.msg188445#msg188445 date=1427277303]A few pounds perhaps.  [size=78%]  You can't put a guaranteed standard on how hard an engine has to work. [/size]

Basically you are talking about the cluth slipping which may count at hard accelerations or much higher speeds and rpms. Don't think it is the case here.
[/quote]

Basically I wasn't 

[rhinoeli]

I bet you're mates have fun winding you up   

Sorry, don't really know what does that mean. English is not my best...

A few pounds perhaps.   You can't put a guaranteed standard on how hard an engine has to work.

RPM, transmission, gear ratios and wheel speed are proportinal to each other. The only thing between them is the clutch. Don't know what else were you talking about.?

[midden]

A few pounds perhaps.   You can't put a guaranteed standard on how hard an engine has to work.

RPM, transmission, gear ratios and wheel speed are proportinal to each other. The only thing between them is the clutch. Don't know what else were you talking about.?
[/quote]
engine won't need to work as hard going down hill as it would going up hill for the bike to reach 70mph

[fazersharp]

Its odd that the speedo is not an MOT test item

[rhinoeli]

engine won't need to work as hard going down hill as it would going up hill for the bike to reach 70mph

RPM is the same uphill and downhill if the clutch is engaged. It has nothing to do with the "work".

[midden]

Ok I'm with ya now.
But I'm still over 6k at 70mph  standard bike 

[AndyL]

Mine reads about 5,800 or 5,900 at 70mph

[greenman]

Ok that got some very mathematical responses, when I say 61/2k rpm, I use this as a rough guide. I have a Speedo that occasionally goes weird, apparently I was doing 125mph around a roundabout I usually take at least than 30 a couple of weeks ago so when it was behaving itself I checked and displayed 70mph is just under 6500rpm = won't get nicked.

[midden]

Commuting to work I feel compelled to jump off and stand corrected.  70mph between 5800 and 6 rpm, 6500 is my normal riding area  :o sorry Rhinoela

[the cueball]

thanks everyone, very interesting answers...  :rollin

[Jules-C]

I have a Speedo that occasionally goes weird, apparently I was doing 125mph around a roundabout I usually take at least than 30 a couple of weeks ago

Check the route of the speedo sensor wire in particular by the brake disc.  Weird speedo readings are often caused by the edge of the disc wearing through the insulation and contacting the copper wire and sending confusing pulses to the speedo

[Beeblebrox2nd]

Popping down the road for a jolly jaunt shows that at an indicated 70mph, my tachograph is reading 5900rpm, in standard gearing in top gear.

[clayt74]

Yep I get 5800 at 70mph standard bike! There is also quite a variance depending on tyre condition n profile. A few extra mm in tread has a large impact on the circumference of the front wheel hence a difference in speed reading..... Also how much tread on rear tyre will also affect the drive ratios.
Hehe I await the flaming

[greenman]

[quote author=greenman link=topic=16362.msg188504#msg188504 date=1427305066]
I have a Speedo that occasionally goes weird, apparently I was doing 125mph around a roundabout I usually take at least than 30 a couple of weeks ago

Check the route of the speedo sensor wire in particular by the brake disc.  Weird speedo readings are often caused by the edge of the disc wearing through the insulation and contacting the copper wire and sending confusing pulses to the speedo
[/quote]
There is a nick in the the insulation by the disk, I just need to get around to getting it sorted but until then.......

[Jules-C]

......wrap a bit of insulating tape round it to stop water getting in and leave for about 7 years.

It was good insulating tape its not even been replaced!

[YamFazFan]

My 600 is as standard as they come & top gear at 70mph is a fraction over 6000rpm. Maybe 6100'ish.

Correction  :o :o :o: Just been out on the bike for the first time in ages & made a special point of double checking this figure. At 70mph on the speedo the tacho is reading, as close as I can tell, 5650 RPM.

[freeware]

Standard gearing from my POV:

[fazersharp]

I make mine to be 5850 rpm standard bike, dosent look quite like 5900