Oversizing to make up for short transmission ratio

Yes your going to run into rubbing issues

No you can't run down the highway at that low of rpm. These aren't meant to do 80mph down the highway. At 55-60mph the RPM is right where it belongs. So engine RPM is up to keep up with high speed traffic. These engines are 2.4L, they don't have a bunch of torque.

These aren't that light weight, they actually weigh slightly less than a Jeep Wrangler. And it's not the weight, people are too stuck on that which is a tiny part of it on the highway, it's the aerodynamic drag. It's effects increase exponentially the faster you go. Have to find a balance point.

The low gearing is helpful if you want to run oversized tires around town. I have the automatic and only lost about 1mpg in town going up about 8% on tire size (16" wheels). But will pay for it on the highway. The engine is too small/not enough torque to deal with larger wheel/tire combo without sacrificing highway MPG.

Also 3000 rpm for long periods on a Honda engine is nothing, won't hurt it. Trying to spin wheels and tires that much larger to do 80mph or more (not hard to figure out the speeds your trying to go) your going to smoke the transmission because it's not meant to that kind of stress. Not to mention much bigger modern SUVs would get better MPG because you'll be lucky to break 18 at those speeds

There is a balance, but 8.4% jump at the speeds you want to travel isn't it.

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emeron,

I use different size tires on one of my vehicles (works great - for it), but a few things to keep in mind:

Note: Every time my one vehicle (even at near empty load without towing anything) hit some simple rolling resistance, it would "down shift" and its RPM needle would spike up into 3-4K range. And going up a low grade hill, it would downshift several times. Thus, sucking down the gas like it was a starving animal. Ouch! So for that specific vehicle (which has known factory "too tall" OD gear), I installed "smaller" diameter tires. For it, I went from factory recommended 65 series to 60 series - using same rims. This rubber change is a 3.2% "smaller diameter" change.

In learning from this, here's a few things to keep in mind (for your larger size tire research):
- Many auto shops / tire makers recommend staying < 3% diameter size change. More than 3% change may impact vehicle's ABS, TSC and other computerized systems. Especially on a 4x4 system.
- I seen tire changes up to 5% without their ABS lights coming on. And, I've seen older age big 4x4 trucks go up to 14% tire change without impacting their ABS light. Each vehicle is different. But, I would recommend staying around the 3% range - without risking computer's calculation traction problems. Especially on an AWD system.
- For desired tire change, proactively calculate the end results. For me, rubber change is 3.2%. Take this number and apply to the vehicle's RPM at specific mph numbers. For my vehicle, it was factory tire size at 1,500 RPM at 62 MPH. Since I went with smaller tires, I applied the 3.2% against 1,500 = 50. With smaller size tires, the RPM would now be around 1,550 @ 62 mph. Yes. The speedo will be off by 3.2% as well. But, my wife always drives over the speed limit anyway. LOL! And, we always use its on-dash GPS unit - which show "real" MPH ground speed anyway. In your case, take the larger tire size difference number and apply to engine's RPM number. For example: 3,200 RPM @ 62 MPH (real ground speed), your RPM needle would show 3.2% less - which is 3,200 - 105 = 3,100 RPM. Not a huge change but every little bit counts.
- Keep in mind that math numbers aren't linear calculations in real life. The more one increases tire size, the more weight it must spin (and stop) and the more wind drag the vehicle will have. You may not notice increased rolling resistance but with full load of people, you my feel engine lugging / that didn't previously exist. Especially when using diluted Ethanol gas and weaker winter mixer. Ouch!
- If tires rub, apply a lift kit. This might help. I keep reading the CRV can have up to 1" front and 2" rear lift using spacer blocks without factory suspension changes. For lift kit spacer blocks, surf e-Bay.
- When changing tires (or even rubber on same rims), do use same or better tire weight rating and tire speed racing numbers. And if you like to load heavy, go with higher weight rating numbers.

Long mumbling short, I'd say do increase tire size (if you think your vehicle needs it). But, I would recommend staying < 5% change. And, staying near 3% change would be better. Choice is up to you.....

If wondering, I'm glad I installed smaller diameter tires on my one vehicle. It was a good "tweak" to make it better. And, I'm glad I did it. Hopefully, you have good luck with your minor tweaking as well....

Hope this helps...

emeron said:

What's the largest tire size have you guys installed and what are your experiences?

I am not concerned about ABS sensors and the parody of an AWD system as I am going to go for the same size tire all around so there will be no rpm differential. I am more concerned about increased ride height as most SUVs have the handling of a wheelbarrow. I am hoping with a small adjustment in rim offset, slightly increase the track width to make up for the increased height and keep the body roll in check.

Click to expand...

I thought I explained that above.

I have 225/70r16 and that's as big as your going to get without rubbing all the time. 8.0% increase The fronts just barely touch the inner fender well sometimes (clean spots in the plastic but no actual noise or damage) If your rear springs are weak you will have rubbing issues in the back though.

I'm running Jeep Wrangler wheels which have a offset giving about 10mm wider stance (so 20mm total).

Body roll isn't a big issue for me, but I don't overly ridiculous.

Gas mileage at highway speeds above 55-60 are total crap.

As for that rule of only 3% ya that's way off. It only effects those with computer controlled AWD and traction control (that is more than just the ABS module) because the sensors may not match up to the data the computer itself is looking for.




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