is there a reason the X and Y idlers aren't toothed?  

Re: is there a reason the X and Y idlers aren't toothed?

I replaced my x idler with a toothed pulley. I really did not see a difference. Seems like it would be better, but it seems anecdotal at best.

Re: is there a reason the X and Y idlers aren't toothed?

nice to know...still tempted to do it.

Re: is there a reason the X and Y idlers aren't toothed?

Good question, since the toothed idlers are less expensive than the smooth ones (at least on Amazon today). Perhaps not when OEM purchasing in bulk(?)

https://www.amazon.com/BIQU-20Teeth-Aluminum-Timing-Printer/dp/B01H3DSGAC/ref=br_lf_m_de9q8ergtqgrkeb_ttl?_encoding=UTF8&s=industrial

https://www.amazon.com/BIQU-Aluminum-Toothless-Timing-Printer/dp/B01H3FNZ4M/ref=br_lf_m_de9q8ergtqgrkeb_ttl?_encoding=UTF8&s=industrial

Re: is there a reason the X and Y idlers aren't toothed?

in my head it seems that it would give more consistent tension since the belt teeth are contacting fully with the idler teeth instead of just smashing the belt teeth down onto a smooth surface.

I don't think there are any downsides but it may not make a noticeable difference either way.

Re: is there a reason the X and Y idlers aren't toothed?

I just feel like I should eliminate anything that might give any play.

Re: is there a reason the X and Y idlers aren't toothed?

You're adding more friction with the toothed idler. If it doesn't fit perfectly, you're eating the belt faster.
But I think the mechanical difference is so minor in that case that other factors like easier quality control and availability made the run.