# 2.75 Omni VS. 3.25 Omni Speed

I was just wondering, in terms of how speed and all that goes, what would be the difference between 2.75 and 3.25 when it comes to 450RPM and 600RPM? I doubt that there is much of a difference, but I would still like to know because my team is going to use 450 RPM, but later season seeing as skills could be a large factor for us at States, we might use 600 RPM just so that we use less time going to each goal. My team and I are going to be ordering wheels, but we’re not going to order both 3.25 and 2.75, so in a quick summary, I would like to know if for 450 or 600RPM we should use 2.75in or 3.25in wheels. I would also like to know the calculations for the two if anyone could provide those.

Both of those speeds will likely be too fast on 3.25 omnis

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Alright, thank you for your help.

To find the linear speed of a drive in inches/second, the formula would be:

(wheel rpm * wheel circumference)/60

But more often, you’ll see drive speeds talked about in terms of RPM and wheel diameter.

Both 450 and 600 on 3.25" are very very fast. 600 is definitely not viable, will be far too weak as well as uncontrollably fast. 450 is viable, though it is extremely fast and will take a very light robot with very little friction and high driver skill to work well. Personally, I really like 400 rpm on 3.25" wheels, it’s still very fast but has decent torque and is very nice to control.

450 and 600 are both viable and common ratios on 2.75" wheels. 600 is just about the upper limit of what is currently considered feasible. It’s very easy to use because you can just direct drive wheels on 600 rpm cartridges, but it is very fast and you need to be confident of your driving and build quality to make it work. 450 is still fast, but has a little more torque. It’s also harder to gear though, and the added friction from the more complex gearing might actually make it weaker than direct drive 600 rpm if not built properly.

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Thank you so much, I will definitely be ordering the 2.75’s.

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