Bike clocks vs car clocks

[Howling TerrorOutOfOffice]

..................
____________________
Diabolical homemade music Bandcamp and Soundcloud
Singer songwriter, Artist and allround good bloke Listen to Andrew Susan Johnston here
The Harry Turner Project

[Kickstart]

Hi

Both can be pretty poor. Ford clocks used to be notorious (would make an RD125LC look accurate).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Pickle]

Is it right that bike clocks are generally slower than cars? So when you think you're doing 30 you're only doing like 28? That's what some grizzled biker told me - wasn't sure whether to believe him or not...

[0ddball]

I've generaly found most cars speedo's to be out by 5mph compared to gps, well up to about 100mph anyway.
____________________
ZXR750L

[MarJay]

My subaru overreads by about 4mph right across the range (up to about 100 anyway!).

I reckon with proper tyre pressures the Speed four is actually more accurate.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[The Disapproving Brit]

According to the little signs that display your speed on roads round here, my bike is about 5mph out, showing me at 30 when I'm doing an indicated 35.

Not sure which ones lying though...
____________________
Current Bikes: 1983 Honda VF400FD / 2003 Honda VT750 Shadow
Bike Test Passed 18/03/09, Car Test Passed 14/05/13

[Kickstart]

Hi

There are limits on how accurate speedos must be, and they can legally be more than about 10% high (10% + 4kmh for mopeds, 10% + 8kmh for motorcycles in production), but this is only checked at a couple of speeds (from memory 50kmh and 120kmh), but they must not read low.

On that basis at a true 30mph your speedo could quite legally be indicating anything between 30mph and 38mph.

Checked our cars. They seem to vary. Alfa 155 for example reads about 5mph high just about everywhere.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[krebsy]

Aye, my Ford is out by about 10%+. The GPS reads 70, the speedo 78...

K.
____________________
What's my New Year's resolution?

1280 x 1024.

[neil.]

Weird, my YBR speedo is bang on with the TomTom GPS right up to 70mph, which is the most I've ever got out of it. When I have mates/family in a car following me, they say I go over the speed limit but I'm actually dead on - their clocks are over-reading. Maybe I'm extremely lucky?
____________________
CBT February 2008 | A2 June 2008 | Yamaha YBR125 (written off) | Honda CBF125 (current)

[jayvfr]

The Fiat used to be bang on all the way round the speedo, well according to the gps anyway. The Saab's about 6-7mph over reading and I dread to think what the Kwak's at!
____________________
A quater of a NC30 and a whole tatty ZX6R J2, that's plenty...
VFR bits for sale, PM me for details!
PSN ID: money85

[smegbrains]

[.Chris.]

My car is comically inaccurate. I haven't tested it at high speed but when the clock is saying 50mph you're only doing 42mph.
____________________
Chris
1985 Kawasaki Z550F

[G]

Depends a lot on the vehicle and manufacturer.

Generally about 10% faster is displayed, I'd say.
Both my KTM690 and VW LT35 (van) seem to be very accurate; under 5% out.
My laguna and passat were both quite a lot worse. My RS250 actually displayed 10-15% slower than your real speed, which was worse.

Got told off on an IAM ride once when I was using a GPS for a speedo - the observer was very suspicious of my claims that it was much more likely my GPS was correct and their speedos were over-reading.

[cicatrez]

I usually end up riding around at 33-34mph as indicated on my Speedo.
Whenever I go past those Speed check signs it tells me I'm doing 30mph and gives me a Smiley face
____________________
-----------------------
'02 Honda City Fly

[DugieT]

[MattEMulsion]

I think that you need to compare like for like, ie the more modern (often digital) speedo's I think are a damn sight more accurate than any old style or even cable type job. All speedo's should over read slightly rather than under read. I believe a figure of 10% max is about right for todays standards.
____________________
Yamaha YZF-R6

[Kickstart]

[Azonicben]

Worst thing with digital is the garbage they give out anyway, Lag? with my mates you just end up with 00, 26, 35, 56 never really sweeps up the numbers just shows odd speeds as you accellerate.
____________________
Cbt-23/09/07.....Theory-16/09/08.....Das passed 10/10/08.....
Current bike- GsxR750 K4. Broken: Cbr400rr (Nc29) Sold: Hyosung GT125R

[Howling TerrorOutOfOffice]

..........................
____________________
Diabolical homemade music Bandcamp and Soundcloud
Singer songwriter, Artist and allround good bloke Listen to Andrew Susan Johnston here
The Harry Turner Project

[Kickstart]

[Howling TerrorOutOfOffice]

Nice1 Keith
____________________
Diabolical homemade music Bandcamp and Soundcloud
Singer songwriter, Artist and allround good bloke Listen to Andrew Susan Johnston here
The Harry Turner Project

[Kickstart]

[Noxious89123]

____________________
'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[Tango675]

According to my TomTom's and my Road Angel both the car (SEAT Leon TDi) and bike (SV650 K1) over read by a few MPH, increasing as the speed goes up. Both are digital speedos.
As did my old Citroen Xsara TD

The 1982 Saab 99 I owed for a bit a few years ago had the most accurate speedo as it matched the GPS until over 90.
____________________
Somebody give that windup merchant a torque wrench..

[motobiker]

With my Bike the problem doesn't lie in the speedo itself but in the drive at the wheel.

For some unknown reason those pesky Germans decided to fit a drive with a 1-3 ratio to the GS - this gives a speed thats on average 12% under.

The fix is to replace it with the drive from an 'R' R850R/R1100R/R850RT/R1100RT/RS

which has a ratio of 1-2.6 - this gives an error of just 2% at all speeds.

Why they did this is a complete mystery.
____________________
1999 R1100GS + 2006 F800S
(Nottingham)
Sooner or later opinions fade and the name on the tank matters not. I think that happens somewhere between 3rd and 4th gear. Enjoy the ride... everything else takes care of itself.