speedo recalibration?!?!?!

Probably a candidate for stupid question of the day but can i get the speedo re-calibrated on my landy because ive now got bigger tyres?

Its a TD5 and im running 285/75/16's

Im never going back to the standard size so rather than little tipex marks on the edge of the speedo i want to get it sorted permanently.

Thanks

Matt

Suspect the answer is no

Could use a GPS unit?

Is the speed difference from the tyre change enough to worry about? Most speedos over read by up to 10% anyway!

Station House said:

Suspect the answer is no

Could use a GPS unit?

Is the speed difference from the tyre change enough to worry about?

Click to expand...

Absolutely SH ... I checked mine against the speed shown on the Sat Nav and found that with my bigger 265's the speedo was more accurate than it was before!

Hi Matt

Beein doing a bit of google'ing and apparantly you just need to change the gear in the speedo gear unit to one that fits your new tyre size?

See here: How to replace the speedo drive gear on a Land Rover - The Land Rover Blog

Hope it helps

My speedo compared to my tom tom is out by about 4mph at 30mph. So the speedo reads 30 and im doing 34. then at 40 its out by 5mph. you get the idea fellas. god knows how far its out the faster i go. i just stick to 60 on the speedo and hope i dont pass any rozzers! lol


thanks chris ill read that in a minute.

Matt

Land Rover 90/110 speedo drive gears

Colour: blue/20 teeth - Part number: FRC3310 - Tyres: 7.50/16 or 235/85/16
Colour: green/21 teeth - Part number: FRC3311
Colour: yellow/22 teeth - Part number: FRC3312 - Tyres: 205/16 tyres
Colour: red/24 teeth - Part number: FRC3313

If those are the only 4 gears then i think im f&*ked, as i would have thought id need a gear with less teeth on as the wheels are bigger right? so as to do more revolutions as the road wheels do less?!

Matt

All might not be lost, the TD5 speedo is electronic if what I've read is true.
Electronic speedos count pulses rather than revolutions, much the same as rev meters do.
Anyway most guages have some kind of fine adjuster that they use to calibrate them in the factory, it is usually accessible without taking it apart ... often will have a sticker over it.
I don't know if a TD5 speedo has one ... just saying it might be worth looking.

I'm assuming 'Yellow' is the standard from the orig tyre spec.

If so, and if you can be bothered, the 'blue' one would get you closer, and as Andy says, you might then find that your speedo (which usually over reads) will be closer to the GPS!

Car speedos are only really a guide rather than meant to be accurate - a bizarre statement I know, but that's why the Police 'usually' allow you 10% over before you get fined!

Stupid question - I presume the speedo is mechanical? I'm probably wrong but I thought later cars moved to electronic?

PS and Damn - i must get quicker at typing - Cwazy had posted the electronic question as I was typing!

The electronic speedos still allow the different coloured gears, it's just now there is a transducer instead of the end of a spinny cable connected to them and then it's wired back to the speedo, apparently doesn't go anywhere near the ECU.

A little bit of googling suggest that Digidash Mileage Correction for Sussex, Kent and Surrey - Home will alter the total mileage displayed by the odometer, it may be worth ringing them to see if it is possible for them to perform a calibration at all, I'm not suggesting you get them to do it (that's your choice) but it would let you know if it is possible.

If I had one I'd take it apart and have a look for you but I'm still in the world of an old mechanical speedo guage.

PS Station House I too suffer from slow typing.... many times I see multiple posts before mine joins the thread!!

the ealier coloured gears arent compatible with transducer type the square drive is different size

My mistake, I apologise for the misinformation

I'm surprised nobody has put any info about reprogramming the td5 speedo's on the web, they have been around long enough.

I'm tempted to buy one and work it out, except there are more pressing issues on my 110 than replacing a currently working (if a little wobbly) 24 year old speedo.

Sorry again for the mis info about the coloured gears.

jamesmartin you seem to be a man of considerable knowledge on most things land rover.

Would you know about re-calibrating a speedo for bigger tyres?

Matt

Not from first hand knowledge (mine's a 1994 90!) and I've lifted this from another site, but believe you can change the little gear on the transfer box which operates the transducer.

If you go to the transfer box, look behind the handbrake drum, you'll see the cable plugged into the transducer. Undo the 10mm nut and you can pull the transducer out - see what colour gear is in there (it's a plasric thing, about 1 1/2" long) and then you can get whatever one you need.

90/110 drive gear part numbers are:

frc3310 blue ---------20 teeth
frc3311 green ------- 21 teeth
frc3312 yellow ------ 22 teeth
frc3313 red ----------24 teeth


Do please check with someone more knowledgeable first

iam afraid you cant ,you can physically do it but the square drive is smaller on transducer type ,transducer speedo will be black ,from first hand knowledge,although you do seem a very nice person mr station

I don't know about the TD5 speedo, but I do know the BMW electronic speedo on my ex-police K1100lt (bike) can be adjusted and, as it works upon the same principal as the TD5's electronic one I would assume the same is possible. Somewhere I had a bookmark for how to set it up but can't find it now. I know it hasn't been checked for a long time, but the speedo head on my bike has a calibration stamp on it from when it was a police machine so I usually use that as my reference (friend on bike at set speed and me driving behind him etc.)

I have found that GPS are not very accurate. I assume it is something to do with the fact that they are accurate to within so many meters of your location, the time taken to make the necessary calculations and the time taken to display everything on the screen. I find my GPS shows about 2 to 3 MPH less than my speedo, and the roadside speed displays in small villages etc.

I agree with those who say that your vehicle speedo is probably set anything up to 10% high. Otherwise, every time you got done for speeding, you could sue the manufacturers if it was showing under.

Can't you just tie a knot in the wire to slow down the pulses?

Cheers James

Glad I provided the 'do please check' comment!

On the 'nice person' bit - I'll have to get you to have a word with my wife - not sure she'd agree with you

Only other thread I found was around replacing the whole speedo with a different unit - one that uses the pulses but can be calibrated - seriously expensive!

If it were mine, 'live with it' is feeling like the right answer!

jamesmartin said:

you do seem a very nice person mr station

Click to expand...

He is a nice person and very proud of his looks ... in fact he rustproofed himself recently ... sorry SH, couldn't resist

No worries Andy - comes under the category of both accurate and fair comment (the rust proofing bit that is!)

Still got black chassis paint on my forearms by the way - dead impressed it's only just fading after 3 weeks. Now if it's only half as good on the chassis......

I'm feeling tempted to strip down a TD5 speedo to work out how it works, we do a bit of work on embedded systems at work so it would be interesting.

Anyone know where I can get a cheap one? or how much it 'should' cost for a used one.

Id try checking how far you're out first. Use the tom tom as suggested above.

I had standard 205/85R16 tyres on mine. The speedo was reading about 10mph over at 70. All that time I thought I was getting 70 out of it and I was only doing 60.

Anyway, just changed to 235/85R16. just under 10% bigger according to etyres calculator thingy.

Now it reads somewhere between spot on and 1 mph under.

I'm happy with that.