Tyre size change

[JuhaniLS1]

Does going from stock Camaro SS with E92 245/275 tyre combo to 1LE 285/305 combo have any other changes to be done than speedo calibration, as new combo is bit smaller and also slightly mismached in high. Stock setting speedo read 2% too much against GPS now about 5%. Do I calibrate something in T43 too.
This is 2018 manufactured Euro spec car. I have managed to read calibration.

[JuhaniLS1]

Hmm. I have read posts about this, seems to be not so simple as it was in LS1. Is the speed signal coming from VSS or ABS does Camaro have VSS? There is rear ratio in parameters, 2,77 on auto, now because tyres are smaller car sees higher ratio in practise, what happens if you change ratio 5% will it compare it to ABS and then ralationship is wrong and it pukes or?

[JuhaniLS1]

Well I chanced pulses/km from 465 to 490 and now speedo reads exactly same as GPS at all speeds. Did not notice any chances in shifting and no mils.

[joecar]

Yes, it has VSS, it is a TCM pid.