hotfish23

I have a 2019 RST Z71 with the 18” wheels. Today I was looking at a buddies truck that has the 20’s and realized that something looked very different and it wasn’t just the rim size. I then noticed the actual tire sizes are very different. In the past chevys with the 18’s had 265/65r18 tires and still do, while the 20’s got 275/55r20 tires. This was a difference of a 31.5” tire vs a 31.9” tire. So a very negligible difference. In the 2019’s the 20’s come with a 275/60r20. This is a 32.99” tire. A 1.5” difference from the 18’s. This is enough to cause about a 4mph difference on the Speedo and a difference in the odometer too. (Before anyone says it, I also measured the tires as well, since we all know manufacturers aren’t always the most honest). I find all of this interesting because it would mean that Chevrolet programs the comps based on your tire/rim package. This baffles me as it seems as though that keeping a very close tire size across the board would result in less work on their end. Does anyone have any light to shed on this? Sent from my iPhone using Tapatalk

Thanks! Did really good on the beach for being stock too. Sent from my iPhone using Tapatalk

Hard to beat.....

Have you noticed any loss in low end torque? I ran a straight through muffler on my 16’ and it seemed to loose a little bit of ass. Sent from my iPhone using Tapatalk

Not that it will be a huge difference but remember that your new tires are 33" which is larger in diameter than factory by 1.5", if I'm not mistaken. So not only is your dic off but so is the amount of miles that you are using in your hand Calc, if you are using the odometer. You are actually traveling farther than the odometer is reading given the increased circumference of the tires. Sent from my iPhone using Tapatalk

I agree that a 1/4 mpg isn't much. It's been stated that the difference is a 1/2 mpg, but that isn't really the point of the conversation. It's definitely more of friendly discussion. However, saying we just have to assume it's there because of mileage is not necessarily true. In an industry, world for that matter, where designs are driven by the mighty dollar an extra piece of plastic wouldn't be added for no reason. There is a gm published video showing the results of the dam and it's quite amazing. This is definitely included on the vehicle to help meet the demands of the federal gov for mileage. Sent from my iPhone using Tapatalk

I understand the logic but that's assuming the only factor at play is the angle/height of the dam. This is ignoring all of the non-aerodynamic pieces hanging below the vehicle. Take your example and place things that create drag behind that piece of wood and even if the wood is moved up or at a different angle it will help in reducing the drag created by that in which is behind it. I appreciate your time and response. And hope this can be a constructive conversation. I am a mechanical engineer in the aerospace industry so I've dealt quite a bit with drag and the likes. I've just always assumed that the dam on a truck would be beneficial regardless of height and angle (unless you are lifted high). I am leveled with the dam on and am curious now if I would see and change if I removed it. I believe that I would. My thoughts on this, are that the dam will still push air to the sides and lower towards the ground away from the drag behind it. As well as routing the air around the tires towards the outside, which believe it or not, are huge sources of drag. Sent from my iPhone using Tapatalk

I'm not trying to be an ass. But how do you know that the air dam is now causing drag/resistance? Have you seen evidence, or is this an assumption? Sent from my iPhone using Tapatalk

Tire and level specs? Looks great! Sent from my iPhone using Tapatalk

What are the specs on your truck? Lift height, rims tires? Btw it looks good. Sent from my iPhone using Tapatalk

I'm not trying to talk anyone out of this handle or diss on anyone who has one, but I had one in my first 2016 and not in my second. Upon receiving the second truck there was a noticeable difference in visibility. Just throwing that out there. Sent from my iPhone using Tapatalk

That's only a 1" level? What brand? Sent from my iPhone using Tapatalk

You will most certainly feel it. It will stay in lower gears when cruising on the interstate and take more gas to get you moving. The diameter has less to do with it then the mass associated with those tires. You will be going from a four ply to a 10 ply tire and they will weigh much more. You will probably see a fair amount of mpg loss as well. But it will look sweet! Sent from my iPhone using Tapatalk

What's your setup? Sent from my iPhone using Tapatalk

Obviously it's ultimately your call, but I would highly recommend against a 3" level. 2.5" is the max that most people agree is the most you should do. I play it safe with a 2". 3" will put terrible angles on your suspension and will wear things out prematurely, and will for sure not be covered under warranty. That's not even taking into consideration having almost no travel. Sent from my iPhone using Tapatalk