Greetings,

I need answer to question: how to calibrate (or set up) wheels/tyres size in S-Type using SDD? As far as I know there's such data stored in modules (which one?) and it is possible to read eheel size settings using Enginnering Test Mode (ETM). The thing is ETM shows decimal (or hexdecimal) values and still I didn't found any way to read (translate) them. Also I tried to find adequate tool for setting up wheels or tyres in SDD, but no result. Can You help me out, any clues?

Thanks in advance

 

Probably stored redundantly. I suspect at least VID blocks and ICM. Er, what are you trying to do / why?

 

Well you hit one of the major problem with trying to modify an S Type. The ECU has not been cracked. We do now have a very limited tune for the STR but this is only the tip of the iceberg and most likely will not progress very much.

Just as a comparison the Lincoln LS which is a twin but not identical has a simple aftermarket programmer that allows you to change the tire OD.

Perhaps Brutal can answer if it's possible to use the IDS/WDS/SDD to do this. I don't think you can.
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Does this help Tire Size Calculator

 

Stan - Not at all. See General Tech if you don't know about IDS/SDD at all.

 

Thank You for all replies.

Got two reasons to do tire/wheel size modifications:
1. Speed indication - I suppose it is inaccurate. By now I've got set of 18'' Triton wheels, and 245/40/18 tires. There's digital speedometer in ETM mode which indicates speed about 2-3 kph lower than indicated in the instrument cluster. It looks like one of them is inaccurate, but which one? Also my GPS shows car's speed about 2 km lower than instrument cluster, but GPS has signal delay for sure so I don't take this measurment as an accurate one. So in this case I'd like to check if stored wheels settings are correct and appripriate to wheel size I actually use.
2. I'd like to buy a new set of 17'' alloy wheels. In this case I'll have to buy 225/50/17 tires which affects speed indication by about 1%. I'd like to confugure car's settings to new set of wheel size and get accutate speed indications.

About the modules. I wonder if ABS module programme would have something to do with speed indication? As far as I know speed is sensed by abs sensors.

 

Go hunting round the menus. I don't think most care about 2% or the like. (And also don't have SDD.)

 

I have found the GPS speed is within my ability to tell any difference with the speedometer. No more than 1-2 MPH different.

The S Type uses several speed inputs. The ABS sensors are just one of them. It also measures the input and output speeds of the transmission. Don't know which one is used for what but you can't change the rear end ratio without throwing the car in limp home mode.
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At last I've found it!

In SDD menu select "Service Functions" session type. Then select "Recommendations" tab. Then select "Add/remove accessories" and then in nex menu choose "Tires (Rolling circumference)". After that choose tire size You need to calibrate (from 16' to 18') and confirm to begin calibration.