Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
Default IID Tool Wheel Radius? Incorrect Odometer
Does anyone know what the default wheel radius should be?
Mine is currently set to 400mm as my previous wheels were 800mm. I've now downsized so this figure is incorrect. I was going to change it to my new wheel size (387mm) however I have since learned that playing around with this figure can cause more harm than good so I'd like to just reset it. I don't want to reset the whole car or restore defaults as I have a lot of other settings changed and I also have no idea if the backup file is even correct. Ta.
Side note, why is my odo so far off? 170113 vs 171070
12th Feb 2022 1:47 pm
Harry365
Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
Bumping for Sunday evening attention.
13th Feb 2022 5:12 pm
Harry365
Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
If no one knows, please could someone with an IID tool check?
Playing around with this figure is absolutely detrimental to the vehicle. I don't want to just assume it is the OEM wheel size. D4 is 372mm. That's all I know.
Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
Using that site gives me a radius of 381mm for a standard wheel size of 255/60R18 which with a gun to my head would be the figure I would enter into the box however I would prefer to know exactly what the figure should be.
Given how much trouble changing this value can cause and how much discussion there is around changing it, I'm surprised I can't find the figure anywhere. I'm also extremely surprised its unlocked within the tool.
15th Feb 2022 3:33 pm
Breg90
Member Since: 04 Feb 2017
Location: Falkirk
Posts: 360
Try measuring your tyre rolling radius. Put a chalk mark at the bottom of the tyres & on the ground at the start point. Drive ~20 M (slowly, in a straight line, in fact the longer the better) with some one outside counting the resolutions - stop with the chalk mark at the bottom again. Measure distance traveled with a tape measure. Divide by number of wheel revolutions and you have the rolling circumference of your tyres. Calculate the equivalent radius, enter into the CCF via the GAP tool.
Another option - use a sat nav to determine your GPS speed on a motor way - choose a nice long straight and drive steady. Note off set against speedo indicated speed. Calculate % offset. Calcluate wheel rolling radius in CCF (2 x PI x R), Adjust the wheel rolling radius by the speed offset % noted against the GPS (not the wheel radius), calculate the new required wheel radius, update CCF. Recheck as required.Series one 1949 - in bits, chassis is strapped to the ceiling in my garage (beside the canoe)
LR 90 - In bits
Disco 3 - currently in bits
15th Feb 2022 10:06 pm
Harry365
Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
Breg, unfortunately this number should not be adjusted from default on the D3. It will not affect the speedo and will only confuse the computer leading to all sorts of issues. It can be changed easily changed on the D4 but on the D3 it should be left well and truly alone, no matter what size wheels you are running.
Thank you for the detailed reply, I wish I were able to change it but ultimate there is only one value that should be entered into the CCF and that is the one it left the factory with.
15th Feb 2022 10:21 pm
Breg90
Member Since: 04 Feb 2017
Location: Falkirk
Posts: 360
Harry,
Not changed it my self. You refer to it 'causing more harm than good'. What happens when your change it?
AdrianSeries one 1949 - in bits, chassis is strapped to the ceiling in my garage (beside the canoe)
LR 90 - In bits
Disco 3 - currently in bits
15th Feb 2022 10:48 pm
Harry365
Member Since: 25 Aug 2018
Location: Lincoln
Posts: 382
I wish I knew exactly what harm changing this setting did.
I've read here (I have PM'd robbie for help too) and on some Oz, SA and US forums the same advice. No one seems to know why it shouldn't be changed, only that it shouldn't.
I have a lot of issues with my D3, lots of gremlins, things that have been fixed but aren't fixed. Gearbox, suspension, instrument cluster issues etc. I'm slowly working my way through them all but I want to give my self the best chance and at least have settings the way they should be.
I can't say with any certainty that this setting has anything to do with the issues I have, I can say that changing this setting previously didn't actually correct my speedo.
15th Feb 2022 11:41 pm
Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1664
Harry365
I raised a similar issue on a smaller scale sometime back. The link to the forum for this is below. Someone else also raised this for a D3 and found the same reason for the issue, so I wonder if this may be the case with yours.
The issue was with the conversion of Km to miles. Try setting your odometer to km on the car (this can be changed back again) it is done under the 'Trip' 'units' option when pressing OK, and then change the units on the IID to Km too to see if they match.
https://www.disco4.com/forum/iid-mileage-r...93707.html
CheersGary
-------------------------------------------
Discovery 4 HSE 2016MY
16th Feb 2022 12:34 am
RichardK
Member Since: 18 Jan 2006
Location: Western Australia
Posts: 295
When I used my faultmate prior to getting the IID I could change the wheel dia in the CCF and that did alter the speedo reading, I haven't had to change it since and I now use the IID for diagnosis.
Cheers
RichardK2009 Discovery S 3, BAS tune, EGR Delete, ARB winch bar, Milemarker hyd winch, HF and UHF radios, Rear spare wheel carrier, Roof rack,
Touring: Australian Offroad Matrix IV Camper
16th Feb 2022 1:41 am
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8225
Although it’s about 3 years ago When I went into the CCF and tyre sizes, by scrolling down the list I found the correct sizes listed as per the size stamped on the tyres ie 255x55x19, 275x45x21 etc.It can when others can't,
It will when others won't,
It goes where others don't.
It will not affect the speedo and will only confuse the computer leading to all sorts of issues.
Changes the speedo for different sized tyres perfectly fine for me. Haven't had any issues, but I'm going to go and have a read of the thread you linked as I haven't previously heard of this setting causing issues
27th Mar 2022 10:57 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2463
I use two sets of wheels with 255/55 r19 off road tyres or 255/55r20 road tyres, i alway change the diameter using gap lld.
My local tacho centre let me use there rollers for an hour 370mm and 383mm gives me the perfect speedo readingsAndrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
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