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Re: Tyre sizes

Posted: Thu Sep 21, 2017 9:12 pm
by GerryP
Hi all,

I have a manual and changed my tyre size in Forscan to 0987 (previously 0977). It hasn't thrown any errors and measuring distance, the odometer is now within 0.8 km over a distance of 185 km, so pretty happy with that. It means my economy figures should be more accurate and possibly the DTE for the fuel tank as well.

The only down side is that my speedo is now (once again) reading 84 at a GPS speed of 80 and 106 at a GPS speed of 100, so about 5 or 6% high. But I guess we can't have it both ways unless we can find a way to 'adjust' the speedo reading separately.

Cheers

Re: Tyre sizes

Posted: Thu Sep 21, 2017 9:27 pm
by rusty-pie
What tyre size do you have Gerry?

Re: Tyre sizes

Posted: Thu Sep 21, 2017 9:31 pm
by GerryP
rusty-pie wrote: Thu Sep 21, 2017 9:27 pm What tyre size do you have Gerry?
I'm running 285-65-17 Toyo Open Country A/Ts

Re: Tyre sizes

Posted: Fri Sep 22, 2017 9:10 am
by saeb
Remember everyone these extra wide changes only effect manual transmission at this stage.

We can make finer adjustments Gerry. Say bring it back a 1kph?

There are other changes in the IPC and PCM for different countries speedometer requirements although changing them did not seem to make any noticeable difference.

Think of it as a fuel saving feature. Less loud pedal :)

Re: Tyre sizes

Posted: Fri Sep 22, 2017 9:41 am
by GerryP
Yeah, I can live with a bit of speedo correction Stewart, I know what to set my cruise control on now to maintain the speed limit, and I'm happy to have the odometer and DTE so close to 100% accurate.

Thanks for all your great efforts mate. :)

Re: Tyre sizes

Posted: Tue Sep 26, 2017 9:44 pm
by wishiniwozfishin
Stewart,

i did the cage to my 2015 auto and its been great. Been about 5 weeks now and just did a couple thousand kms trip town camper and offroading. My vehicle did loosen up at about 27k kms and gel economy seemed to improve but with this change its better :)

I checked with my Hema navigator and the speedo is now spot on with GPS speed. I am now getting as low as sub 10ltrs/100kms and regularly seeing 12's. On my recent trip away towing the camper and offloading I varied 15.2ltrs/100kms which I am over the moon about.

I am running 295x70x16 Mickey Thompson P3 ATZ's.

Re: Tyre sizes

Posted: Tue Sep 26, 2017 11:48 pm
by rusty-pie
saeb wrote: Tue Aug 29, 2017 7:48 pm We may try to implement a feature in Forscan to fix the Tyre size DTC's.

It would be a test and see from a different model vehicle. Doubt it will be implemented to test until all the other changes I have put forward are implemented.
Hi Stewart, has there been any progress with this?

Re: Tyre sizes

Posted: Wed Sep 27, 2017 6:21 am
by saeb
Not with our auto transmission no. We have not been able to make any changes to the TCM and the TCM asbuilt does not hold tyre size so I found out after writing some other calibration files. We have spent too much time on it for now and it is slowing up the Forscan release.

Tested with 10 speed box on a F150 and got rid of the errors though.

Re: Tyre sizes

Posted: Mon Oct 02, 2017 12:24 am
by rusty-pie
That's a shame, the fact that all systems are working on an incorrect speed is really bothering me.

Re: Tyre sizes

Posted: Mon Oct 02, 2017 8:20 am
by saeb
If someone wants to find a used Ranger TCM and send it through then I will crack it open and see if anything can be done but for the short term I'm done spending. No guarantees but unless we crack one open then we will never know.

Re: Tyre sizes

Posted: Mon Jan 29, 2018 10:23 pm
by drprem
Hi Stewart

Am I missing something:
0936 = 2438 265/65 R17 Factory Tyre
0977 = 2505 265/69 R17 - Non existent but closest we will get
0987 = 2520 265/70 R17 - Fault codes
By my calculations with aid from a Hex to decimal converter on the internet!

0936 Hex is 2358 Decimal (80 difference to what you have quoted)
0977 Hex is 2423 Decimal (82 difference to what you have quoted)

What am I missing?

Prem

Re: Tyre sizes

Posted: Thu Feb 01, 2018 7:38 pm
by saeb
drprem wrote: Mon Jan 29, 2018 10:23 pm Hi Stewart

Am I missing something:
0936 = 2438 265/65 R17 Factory Tyre
0977 = 2505 265/69 R17 - Non existent but closest we will get
0987 = 2520 265/70 R17 - Fault codes
By my calculations with aid from a Hex to decimal converter on the internet!

0936 Hex is 2358 Decimal (80 difference to what you have quoted)
0977 Hex is 2423 Decimal (82 difference to what you have quoted)

What am I missing?

Prem
It will be different to a direct conversion. There are other factors and %'s involved, 96.7% from memory, you can download my attached pc app that has the calculation included.

Re: Tyre sizes

Posted: Wed Feb 21, 2018 4:24 pm
by tezza4x4
So do those digital signs that show your speed and tell you to slow down have the same 4km/hr correction in them too? I have noticed they read my speed exactly the same as what the speed on the IPC.


Sent from my iPhone using Tapatalk

Re: Tyre sizes

Posted: Wed Feb 21, 2018 5:39 pm
by saeb
Not that I was aware of but plausible. Could be a way to slow people down.

Re: Tyre sizes

Posted: Fri Mar 16, 2018 10:03 pm
by diomac
With manuals is there a limit beyond 0987 that creates faults? My diameter is 2637mm (33.3" - 255/85/16) I would like to make the ODO as accurate as possible, not really a big deal as I only use these tyres on the farm where I need muddies and a bit more height. On the road I use AT's 265/65/18's.

Re: Tyre sizes

Posted: Mon Mar 19, 2018 7:50 pm
by saeb
You mean 0977? With a manual use what you want, it may or may not through an error. If it does then the PCM needs to be changed as well but is something you cannot do.

Try 09F8 for 255/85/16 for tyre size and 0984 for the 265/65/18.

Re: Tyre sizes

Posted: Tue Mar 20, 2018 10:30 am
by diomac
If it throws and error, I can just clear it and change it back to a lower figure yeah like 0977 or 0987 like Gerry is using on his manual?

Re: Tyre sizes

Posted: Tue Apr 10, 2018 3:47 pm
by Eha002
Could we change the transmission ratio in order to trick the vehicle into thinking its moving faster or slower?

Re: Tyre sizes

Posted: Tue Apr 10, 2018 5:15 pm
by saeb
Axle ratio is also stored in the PCM and TCM so you will get the same problem. Feel free to play though.

Re: Tyre sizes

Posted: Sat Apr 14, 2018 11:15 pm
by Eha002
Ah ok, i might have a fiddle,

See if axle ratio and tyre size calcs can ge tit closer.

Im about 5% out on Trip meter but speedo is spot on according to gps, go figure.

Re: Tyre sizes

Posted: Wed Apr 25, 2018 6:22 pm
by saeb
Yep its the 4% correction. Speedo needs to read 96 at GPS speed 100.

Re: Tyre sizes

Posted: Wed May 02, 2018 9:51 pm
by Eggs1
HI
I've now got BF Goodrich AO 2 , 285/70/17 on my 2016 manual XLT and have changed it to

0977 then 0987 as Gerry has, it now reads spot on 60 kph speedo to 60 GPS (two of them )
and then the same for 70 and 80 and 100 kph I don't know about DTE I have a 140lt tank or distance in km either.

I'm in Perth, doing a half loop from Melbourne and got new tyres and had to get my OBD mailed to me and just got it today.
I'm a amateur when it comes to Forscan and have just followed what Stewart and others have posted, if I get errors where would they show up? in Forscan? or on the dash?
Also is that as big as I can go 0987 or has someone pushed it more or do I need something else beyond me to be done to get it just 1-2 km down more ?
it was reading 100kph on speedo and 104-106kph :shock: on GPS and 60 speedo and 61-62kph GPS so it's better now doesn't seem to fluctuating like it was before even on cruise control on the flat.
I can live with spot on will take awhile to get used to it though. :roll:

thanks Greg

Re: Tyre sizes

Posted: Thu May 03, 2018 6:38 am
by saeb
Basically you want the GPS speed to show 4kph faster than the digital speedometer on the instrument cluster to be back to factory standard DTE. So set cruise control to spot on 64 kph or 104 kph and respectively you should see GPS speed of 60 kph and 100 kph.

You should no issues going higher than 0987 on a manual without errors. Try 09DC and see if you get it back to specs without errors. If you get errors move it back down and clear the DTC.

Re: Tyre sizes

Posted: Thu May 03, 2018 9:28 am
by GerryP
If you get the indicated speed on the dash display correct, unfortunately your DTE and odometer won't be. The % 'correction' applied to the indicated speed (for legal reasons) is programmed in the firmware and is not able to be changed.

So the choices are to either have the speedo reading accurately OR the DTE & odometer... you can't have both, unless of course as Stewart says, you use a Scangauge or a GPS speedo.

Re: Tyre sizes

Posted: Thu May 03, 2018 9:24 pm
by Eggs1
Thanks for the answers, I would rather have DTE correct and odometer the way it was before, I would set the cruise control to 104kph and the GPS would say I was doing 99-100kph
Stewart you said try " 09DC " is that correct ? what's DC ?