Larger wheels to increase gearing

[team-monkey]

Hi all

Picked up my 89 Aerodeck today. Couple of little niggles with it id like to sort out but nothing major.

One of these niggles is that the gearing is quite short so at a cruising speed of 70mph i was doing around 3000rpm which ideally id like lower revs for better fuel economy. Main reason for that is because im planning on doing a road trip round europe in it so an extra mpg or two will make a huge difference over the entire trip.

So planning on increasing the wheel diameter to in effect increase the gearing so can cruise at lower revs.

Read the post at the top of the page which suggests the maximum diameter possible is 24.7inches or a tyre/wheel combination of 195/70/14 with an unlowered car (which is how mine will be staying).

Was wondering if a set of wheels sized 205/55/16 with offset of ET45 would fit? Actually work out at 24.9inch but was just kinda hoping...

Also wondering if anyones running any larger wheels and noticed a difference for cruising? Also whether the increase in diameter would be counteracted by the 10mm increase in tyre width.

Cheers in advance

[RAZR]

The larger your outside diameter is the lower your car revs. I have two sets of tires 185/70/13 for my winter and for summer 205/50/15 and with the 15in rims my cars revs lower because the outside diameter is slightly bigger so i get better gas mileage.

[Dr_Snooz]

I can't say about the tire size, but be aware of wheel weight as you make changes. If you add a bunch of weight with your new wheels, you won't get nearly the mileage improvement you're looking for. All things being equal, you'll probably get better results from a good lightweight wheelset than from bigger, heavier wheels.

[cygnus x-1]

I can't say about the tire size, but be aware of wheel weight as you make changes. If you add a bunch of weight with your new wheels, you won't get nearly the mileage improvement you're looking for. All things being equal, you'll probably get better results from a good lightweight wheelset than from bigger, heavier wheels.


Very good point to keep in mind. If most of your miles are highway miles where you are not accelerating a lot you may get some benefit from larger tires. With city driving, any extra weight in the wheels will be a detriment because you have to accelerate the extra mass. Also keep in mind, narrower tires have lower rolling resistance and are more aerodynamic (less frontal area), so they will give you better fuel mileage than wider tires.

C|

[Rendon LX-i]

when i went from 13s to 15s i used the motegi traklites. which by far was ligher then the oem 13inch well. if have be equal like snooz said.

[AZmike]

If you want to optimize for highway fuel economy look for tires with low rolling resistance. A bigger tire size won't help much. The engine will be turning more slowly for a given vehicle speed, but you'd need a little more throttle since you'll need the same power output.