Advice needed with gearing / revs

[Leonardo]

[Alpha86]

You now have a stickier tire too. Is it possible that you're just noticing a lot more rolling resistance? That would increase engine load, bringing up oil temps and making it rev slower.

[wparsons]

Originally Posted by Zero3210

That was what I understood but does not seem to be the case. Speed measurement already answered as above. I also run a dash OBD2 reader which shows intake temps, manifold pressure, etc if that's of any benefit.

So you're relying on the dash speedometer, or wheel speed sensor readouts on the OBD2 reader?

If that's the case, there will be exactly 0 difference in max speed per gear regardless of what size tires you're running. They could be 2" bigger or smaller in diameter and the rpm vs indicated speed would be exactly the same. Indicated speed is just a mathematical function the ECU runs based on wheel RPM and it assumes the stock tire size regardless of what size tire you're actually running. The only way to change the rpm vs indicated speed is a different final drive, or changed internal transmission gear ratios. Period.

You need an external speed reference (GPS, radar gun, etc) to measure the difference between what the car thinks you're going and how fast you're actually going based on the different tire size.

You say the stock tires aren't road legal, but I'm sure going 160km/h+ is also illegal, so just swap them back for a couple pulls to rule it out.

Looking at the original post again, your original max speeds are also WAY low for an automatic car, they're closer to what a manual car maxes out in each gear. My shift light comes on in 3rd at about 135km/h and that's a couple hundred rpm before redline, there's no way you were actually hitting redline in 3rd in an automatic and only doing an indicated 133km/h. 3rd in an auto should be hitting almost 150km/h at redline.

Look at the difference here to see how much longer the automatic gears are (manual 5th and automatic 4th are the same line, and the speed is in mph):

[86TOYO2k17]

Originally Posted by Zero3210

Before you think this post is in the wrong section, please hear me out.

After months of reading and contemplation, I finally made the decision to upsize from stock 17" wheels and primacies to a set of 18 x 7.5 +45 Wedsport SA20R (weight ~9.8kgs / 21.6lbs via an intelligent measuring system; though on paper supposedly ~8.27kgs / 18.3lbs) with 225/40/18 Yokohamas V105s. The intention was to improve grip and aesthetics, without abnormal change to basic driving character -- as overall diameter only increased by ~2%.

Immediate changes I felt were a more planted driving feel with lots of grip around the corners (haven't been able to slide since #sadface), braked better as well, but what I also noticed was that the car accelerated slower (as expected) but also less rev-happy?

I did some 3rd and 4th gear pulls on back roads and recorded max speeds for each gear:

Before:
3rd max speed ~133 kmh
4th max speed ~174kmh
5th max speed ~207kmh
6th max speed ~218kmh

After:
3rd max speed ~142kmh
4th max speed ~204kmh (revs took significantly longer to hit 7400 rpm and oil temps rocketed in the process)
5th, 6th no longer revs past 5500 rpm and speed no longer increases -- in fact speed starts to decrease and throttle appears to be cut? (as in throttle feels maxed out at 50% pedal input which wasn't the case with stock setup)

So... thank you if you get this far reading but does the experts here think that should be as expected? And if that is the case, can peeps point me in the direction as to how I can improve the revs? The car really feels like its struggling at 4th gear, and 5th/6th gear becomes essentially redundant. Kinda makes me sad to see all the potential locked instead of unleashed.

As a bonus, I thought revs are proportional to engine output and thus should not be affected by change in tires / wheel size so if someone could shed some light to this I would be eternally grateful.

Please help a homie out, my head if exploding from all the self-reading

Bone stock this car is drag limited to about 138mph. 4th gear in auto tops out at about 128mph, 5500rpm in 5th is about 138mph, look at max speed autobahn runs this car doesn’t have the power to accelerate in 5th on autos at 130+mph. And any up hill or strong head wind will decrease your speed in 5th above 5300rpm or about 132mph. Now combine these factors with a 2% larger tire so speedo reading +2% for actual speed. In addition to a big wing causing increased drag. And you have the before and after difference.

Sounds like you are miss remembering your previous speed per gear and everything is working just fine as intended. I am actually surprised if you can hit 5500rpm in 5th with a wing and taller tire.