97blkz

iTrader: (1)

What is involved from going to a 28" from 26" previously? Using lt1 edit would you have to just change the tire height? I think you'd have to change the shift points rpm & mph? Would you go up or down?

horist

with an A4 , yes you'd change the tire height and shift points... HP Tuners does this automatically (it rescales all your trans related tables when changing tire height or rear gear ratio)


Edit: Noticed you said using LT1 Edit... I've never used it before, but if it's similar to LS1 Edit, then yes you would first change the tire height... then go through and scale all the trans related tables by the % change
so
26" tall tire = 2(pi)r = 26*3.14159 = 81.68134
28" = 28*pi = 87.96452

% change in 1 tire revolution = ~8.15% difference

since you're effectively decreasing final gearing, you want to increase the existing shift tables... so multiply the shift tables by 108% (or multiply by 1.08) (bigger tire = more distance travelled in 1 rotation, = lower final gearing, so MPH needs to go up... RPM is RPM)

somebody wanna verify my calcs? It's late and I had a few beers tonight heh

97blkz

iTrader: (1)

I found a site and figured that my mph is off bt 5.3%. I just trying to understand which way I'd move the mph & rpm.? I have been in the dark for so long about tuning I'd like to understand the basics since we depend on it so much.

Thanks for your input.

andy

horist

the MPH would move up

increasing tire height increases tire circumference, which means in 1 revolution the tire moves the car a greater distance, as a result at any given RPM, w/a 28" tall tire you are moving a greater distance than you would with a 26" tall tire... thus MPH is greater, thus you need to raise MPH

97blkz

iTrader: (1)

Agreed , car is going to the track tomorrow to get data logged.