Thread: 2007 110 - change in tyre size improves gear changes?

Has anyone got any knowledge of how the ECU on the new PUMA defenders uses the tyre size parameter to affect (effect - Ron?) gear changes?

I have been running 7.50R16 XZL Michelins on Wolf rims for the last year on my 2007 Defender. The gear change between 1st and 2nd was always a bit 'clunky' but not bad - just not smooth.

Last week I put the original General Grabber tyres (on the original alloys) back on it, and the gear changes are NOTICEABLY smoother. How can this be?

I measured the diameter of the XZLs against the GGs and there is about 10mm difference (GGs are slightly bigger). But 780mm vs 790mm is about a 1.3% difference. Probably a bigger % difference if the circumference but I can't remember the formula to calculate that!

Is this something to do with the setting for tyre size on the ECU, or would it be that the GGs are a softer tyre or something?

How can the tyre size affect the gear change smoothness?

Thanks
David

I have read in a few other threads that there are 3 tyre size settings for the ECU. Perhaps this is not the case?