guys maybe this wud help u to go for an appropriate upsize.
a +-5mm is said to be acceptable .as anything differnt cud affect the handling,the ground clearance,the speedo reading
consider 145/70r13,of the carb zen
to calculate the tire overall diameter(OD),we multiply the tire width by the aspect ratio to get the height of the tire.
tire height =145*70%=101.5mm=3.9961inches
then we add this tire height to the rim diameter.
2(3.9961)inches+13inches=20.9962inches=533.2018mm.
this is the unloaded tire diameter.as soona s any weight is added this will reduce.
for 145/80r12 ,this is 536.8mm(difference of 3mm)in the mpfi zen,so ground clearance increases by 1.5mmand speedo rdg is same.
for upsize of 155/70r13,this is 547.2mm(a massive increase of 14mm over the original tire),so that is 7mm increase in grnd clrnce.
for 155/65r13,this is 531.7mm ,so that is -2mm and so 1mm decrease in grnd clearance .
so to get an almost similar peedo reading the ideal upsize for a zen shud be 155/65r13 that is provided the 155mm does not foul with any body part.
simi;arly u can calculate the required upsize for ur cars |