Can I apply for a new Visitors visa before my old one is expired?

[GeeO]

I have to renew my canadian visa as it is expiring on the 22nd of september and i plan to visit for canadian's thanksgiving in october. Now the issue is that the detroit office no longer does walk ins and so i have to mail in my passport and the minimum time is one month. So calculating one month from the time I want to visit would mean applying for my visitors visa before the old one expires.
Is this allowed? Or do I have to wait till my old one is expired before applying for a renewal?
I am in Chicago.

 

[computergeek]

There is no issue with applying for a new visa prior to the expiration of your old visa.