My car was making a little noise sometimes after going up speed bumps.

So today, I jacked it up, took the wheel off, and noticed the OSR coil spring was broken......

Can a broken rear spring effect the tyre wear?

I know if it's the front ones, it probably would affect the tyres but can the rear one also effect the tyre wear?

yes

I would think so if the suspension settings are out at all.

 

Also I have heard of bits of broken spring dropping down and ripping tyres to bits. Best get it sorted ASAP and replace per alxe or a full set.

 

The rears should be pretty easy to replace.

yes, it will affect the camber and the toe on a multi-link rear end.  It's an easy fix - just a couple of bolts.  About 30 minutes each side if the fasteners aren't corroded solid.

Do I need to get the wheel alignment done after replacing the spring? 

I'm getting the spring changed on Thursday and the cars parked up till then.... 

4 hours ago, mk2octavia said:

Do I need to get the wheel alignment done after replacing the spring? 

I'm getting the spring changed on Thursday and the cars parked up till then.... 

Yes, wheel alignment is a good idea if it hasn't been done in a while.   Also suggest that springs be changed as a pair.