speedo reads fast

[fastandcurious]

I've been out and bought a Road Angel Plus due to my recent encounter with a Scamera van on a dual carriageway. (81mph in a 70) oops! I've no idea whether the laser detector would have saved me, had I had it then, but I thought it to be a good move to get one. Since using this device I've noticed how far out my speedo is. At least 10 mph, even at the lower speeds. Does anyone know any possible reasons for this error and ways to fix it. Many thanks F&C

Edited by fastandcurious on Saturday 1st December 20:00

[spend]

If you have ETB speedo then there is a screw to calibrate on the back of the speedo. You may find it easier to wire the speedo up remotely amd do it on the road rather than doing 70mph on axle stands

Dave

[fastandcurious]

spend said:

If you have ETB speedo then there is a screw to calibrate on the back of the speedo. You may find it easier to wire the speedo up remotely amd do it on the road rather than doing 70mph on axle stands

Dave

What's an ETB speedo. My 94 500 speedo was replaced in 2002 at the TVR factory. Do you think it likely to be that type? I must admit, 70 mph on axle stands wouldn't go down to well on a Sunday morning!CRAIG

[spend]

I reckon generally if the rim is rounded in profile its CAI, and if it's a recessed V then its an ETB. I'm fairly sure they are a slightly different size but that is not so apparent anyway, the minor instruments are like 62mm vs 52mm. The sticker on the back is the proof of the pudding ~ not sure I'd trust any conformity in these cars so thats about as definitive as it gets I think

Dave

[red griff roger]

I have two Road Angels (don't ask) and find they both read about 10% higher than the speedo in a range of cars. Reckon manufacturers put a margin for error in when calibrating?

[TheGriffalo]

Yup, you could even access the true road speed in KMH on my old 911 via the onboard computer. The speedo on them is calibrated optimistically to give you a bit of leeway on prosecution.

[Griffit]

fastandcurious said:

spend said:

If you have ETB speedo then there is a screw to calibrate on the back of the speedo. You may find it easier to wire the speedo up remotely amd do it on the road rather than doing 70mph on axle stands

Dave

What's an ETB speedo. My 94 500 speedo was replaced in 2002 at the TVR factory. Do you think it likely to be that type? I must admit, 70 mph on axle stands wouldn't go down to well on a Sunday morning!CRAIG

Just seen this and my 95 had the speedo replaced at the factory around 2004. Unfortunately it seems the new speedo is calibrated for the later type diff / speedo sensor and I have the older arrangement, thus it over-reads by 20%!!!

Speedycables in South Wales will sort it out for you, but their turnaround time is 4 weeks and it costs about £120ish. I did read that somebody had tried backing the sensor away from the toothed wheel and reduced their over-reading inaccuracy? Haven't tried it so can't comment on whether it works or not. My dash is probably coming out this winter so might go the Speedycables route.

Hope this helps fastandcurious?

[steve-V8s]

Can’t see how moving the sensor too far away from the teeth would help. The Speedo is counting pulses so it would see either the correct number or none. Assume you have the correct size wheels and rubber fitted.

[Ballistic Banana]

I could be talking crap but surely moving the sensor away gives a weaker signal and maybe this doesnt pick up all the teeth and hence false readings. I imagine the sensor has an optimum range? Firking close/knats cock I think

BB

[spend]

I think it depends on the sensor arrangement BB. It seems the earlier (mainly GKN+ETB) setup with the BIG TOOTHED crown wheel on the front of the diff is pretty happy with a range of gaps. The later ABS ring on the output flange of the BTR diff (CAI instruments commonly I think) is very sensitive to the gap and being clean... Very generalized BTW..

Dave

[fastandcurious]

Griffit said:

fastandcurious said:

spend said:

If you have ETB speedo then there is a screw to calibrate on the back of the speedo. You may find it easier to wire the speedo up remotely amd do it on the road rather than doing 70mph on axle stands

Dave

What's an ETB speedo. My 94 500 speedo was replaced in 2002 at the TVR factory. Do you think it likely to be that type? I must admit, 70 mph on axle stands wouldn't go down to well on a Sunday morning!CRAIG

Just seen this and my 95 had the speedo replaced at the factory around 2004. Unfortunately it seems the new speedo is calibrated for the later type diff / speedo sensor and I have the older arrangement, thus it over-reads by 20%!!!

Speedycables in South Wales will sort it out for you, but their turnaround time is 4 weeks and it costs about £120ish. I did read that somebody had tried backing the sensor away from the toothed wheel and reduced their over-reading inaccuracy? Haven't tried it so can't comment on whether it works or not. My dash is probably coming out this winter so might go the Speedycables route.

Hope this helps fastandcurious?

Yes,it certainly does help. The thought of leaving my car in Wales for four weeks sucks! I assume that because the speedo over reads by 20%, the mileage does also. In which case I would have to disconnect the speedo to take off the extra miles it's racked up since 2002 whilst using the Road Angel as a speedo. It's a good thing I don't do to many miles. If any one knows of an easier solution to calibrate my speedo please let me know.I surpose the easiest route may be to swap my later speedo internals for earlier ones. Does any one know if this is possible? Cheers CRAIG

[red griff roger]

fastandcurious said:

If any one knows of an easier solution to calibrate my speedo please let me know.I surpose the easiest route may be to swap my later speedo internals for earlier ones. Does any one know if this is possible? Cheers CRAIG

Bigger wheels?

[fastandcurious]

red griff roger said:

fastandcurious said:

If any one knows of an easier solution to calibrate my speedo please let me know.I surpose the easiest route may be to swap my later speedo internals for earlier ones. Does any one know if this is possible? Cheers CRAIG

Bigger wheels?

[Griffit]

Don't think that Speedycables will remove the clock, they expect it delivered to them by mail AFAIK. You're right in saying the mileage is clocking up at +20% too, that's what bothers me most, though I suppose I can prove that it over-reads ATM and thus show what the actual mileage is that way?

20 working days seems a long time, but they wouldn't budge on it when I rang them.