Speedo Adjustments

Submitted: Monday, Oct 20, 2003 at 22:06
ThreadID: 7963 Views:2633 Replies:8 FollowUps:4
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I am just wanting a clarification as to availability of gear ratio changing drives for the speedo in the 80 series diesel. We have changed our tyres and the speedo is now out by about 5kms per 100 thus 95 is 100 etc. Now I remember reading about being able to source different gearing options for the speedo - Is this correct and where can one source these from?Regards
ExplorOz Team - David
Always working, not enough travelling ;-)
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Reply By: GaryInOz (Vic) - Monday, Oct 20, 2003 at 22:14

Monday, Oct 20, 2003 at 22:14
David try this.
AnswerID: 34533

Reply By: carazy merredin wa - Monday, Oct 20, 2003 at 22:47

Monday, Oct 20, 2003 at 22:47
David, I also have 80 series & my speedo is out about the same amount! I am using STD split rims, tyres, speedo drive gears, diff ratio & my speedo is still out. I sent the instrument cluster away & had it tested-it reads spot on, no faults with it. I have now received from TISCO INSTRUMENTS, OSBORNE PARK PERTH W.A. a small black electronic ratio box. it has 4 wires-12volt, earth, signal in & signal out. All you have to do is turn a small screw while driving along untill the correct speed is achieved. Can use GPS. It is adjustable for all size tyres. Cost $120.00 I havent fitted it yet though, been too busy with work. Hope this helps.
AnswerID: 34538

Reply By: petprass - Monday, Oct 20, 2003 at 23:39

Monday, Oct 20, 2003 at 23:39
I have 285/75/16 Cooper ST's on my Patrol and I find that my speed varies from around 5% to 10% to what my GPS says I am doing. This fluctuation in speed stopped me from getting a Marks Adapter kit to correct the difference in tyre size.

AnswerID: 34545

Follow Up By: ExplorOz Team - David - Monday, Oct 20, 2003 at 23:46

Monday, Oct 20, 2003 at 23:46
I agree with you Marks say 10% however my speedo difference is about 5%. I checked the difference from a site that has this cool calculator thingy that tells the rolling distance of all sort of tyres. From the details I found the actual conversion from the 265x75R16 (I think that was what they were) to the 285x75R16 is 3.7% (I know this number as this is the adjustment forumla we use in our field notes). So a 10% adapter is not much good.

I am still hoping that someone can advise me - Other than that maybe a few dymo labels stuck on the gauge at the correct 50, 60, 70, 80 and 100 may have to do the trick.Regards
ExplorOz Team - David
Always working, not enough travelling ;-)
FollowupID: 24912

Reply By: ross - Tuesday, Oct 21, 2003 at 08:16

Tuesday, Oct 21, 2003 at 08:16
To find a cool thingy just type in tyre calculator into google
AnswerID: 34557

Reply By: David N. - Tuesday, Oct 21, 2003 at 09:57

Tuesday, Oct 21, 2003 at 09:57
As long as your speedo is out by a known amount ie: Percentage(checked by GPS etc) and consistent, why bother adjusting it- just allow for it in your driving. Thats worked for me for many years.
I've had many cars where the speedo is not accurate (most of them in fact) but I've always checked them (used to use the measured klm posts they have for that purpose b4 GPS)
We currently have four different cars in the family (sadly only one 4wd) and all have different but consistent speedo errors. We know what the errors are and drive accordingly- easier than trying to fix them all! eg: my son's Gemini UNDER READS by about 4kmh at 60 and by about 7 at 100! Even my wife knows exactly what the error in her speedo is so no excuses if she gets a ticket!
Having said that, I never cease to be amazed by people who've never checked theirs, and then are "astonished" when they get a ticket!
AnswerID: 34567

Follow Up By: ExplorOz Team - David - Tuesday, Oct 21, 2003 at 11:08

Tuesday, Oct 21, 2003 at 11:08
Yes this is exactly what we do however I was wanting to fix it to reduce the chance of getting a ticket. I was hoping for a cheap and easy solution.
FollowupID: 24931

Follow Up By: carazy merredin wa - Tuesday, Oct 21, 2003 at 21:30

Tuesday, Oct 21, 2003 at 21:30
David, it happened to me 5 or 6 years ago. I was following a cop car on the highway in my VL turbo, at what I thought was 100km/hr. After following for about 20km, I wanted to do 110km/hr & thought the cop was slowing me up delliberately. So I slowly passed them-not going over 110km/hr & guess what-they pulled me over! They recon I passed them doing 120km/hr & should have a ticket. I explained to them there must be a speedo error in my car, otherwise I would not have passed you doing 120km/hr & demanded to see the speed on there radar. He did let me off, so I don't trust any speedo's in any vehicles. Also VL had STD wheels, tyres etc-when't like Greg Murphys commodore-well nearly!
FollowupID: 25004

Reply By: cj - Tuesday, Oct 21, 2003 at 10:50

Tuesday, Oct 21, 2003 at 10:50
Get in touch with these guys, they can probably help you.
Ringwood Speedometer Service
693 Whitehorse Road Mitcham 3132
Ph & Fax: 98742260
AnswerID: 34574

Reply By: Simon - Tuesday, Oct 21, 2003 at 13:36

Tuesday, Oct 21, 2003 at 13:36
I put bigger tyres on my 100 series and now the speedo reads to within about 2% but the oddometer is over 10% out.

I need to get my oddometer calibtated to the tyres then alter the speedo to suit?
AnswerID: 34594

Reply By: Steve o - Sunday, Nov 02, 2003 at 21:53

Sunday, Nov 02, 2003 at 21:53
Hi David, we spoke at the 4WD swap meet about the speedo driven gears available from Toyota for 80 Series Landcruisers. The gear on my petrol auto was a 32 tooth standard, this was swapped for a 31 tooth gear from toyota (available same day in Perth) suitable for my 33in BFGs it has almost corrected the speedo properly (about 4.5% higher indicated speed) as evidenced by using two magellan GPS units.

For toyota owners using taller than standard tyres, not correcting the speedo has wider implications for transmission shifting, fuel economy, and engine life. The pulse generated by the speedo sender actually has several functions. Apart from the position of the speedo needle, the signal is used as an input for the auto transmission CPU, and the engine management CPU, it must also agree with a separate ground-speed sensor in the transmission. Here's where it gets tricky, if for example the speedo indicates that your speed over the ground is say, 10% lower than actual, the signal recieved by the engine CPU has the engine thinking that the vehicle is in a condition of greater load than it really is. The CPU regulates functions such as fuel injection timing and duration. In this case the CPU would be fooled into thinking that the vehicle was travelling up a long gradual incline (as the airlow MAF meter would input high volume signals to the CPU) , even when you are on the flat! Obviously fuel ecomomy is compromised to some degree, and engine life decreased due to less lubricant fluid film in the upper cylinders due to washing with excess fuel.

Futher inplications for auto owners includes possible driveline damage from kickdown occuring at much higher road speeds than was intended for the transmission. This happens as the transmission CPU thinks you are travelling at a lower speed than you really are and considers a downshift appropriate when you plant the foot for overtaking or hill climbing. Smoother up-shifting will also result from correcting the speedo.

AnswerID: 35991

Follow Up By: ExplorOz Team - David - Monday, Nov 03, 2003 at 15:18

Monday, Nov 03, 2003 at 15:18

Nice to meet you yesterday. Thanks for the post I have just realised that you were refering to petrol and not diesel. The diesels speedo is run via direct drive cable and not electronic. Do you know if the drive you are refering to will work on diesel or not?Regards
ExplorOz Team - David
Always working, not enough travelling ;-)
FollowupID: 26008

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