I have slipped off my bike 3x in the last 2 months - will changing tyres help? Recently picked up a used Boardman Hybrid Team and it's my first bike after several years on boris bikes in London.
I was doing great in the summer but recently have slipped/skidded 3 times in last 6 weeks or so and fallen - cutting my knees, once my palm as well. The first was defs my fault (cornering too fast), but the other two I was behaving what I thought to be sensibly and the falls came out of nowhere - though it was wet both times and manhole covers were involved and after searching I'm learning they could be the culprit.
If I want to avoid falling so much I realise I need to change my riding style (keeping an eye out for those manholes to start with, and being more careful with the disc brakes in the wet as they lock up fast).
But beyond changing how I ride, could the tyres the bike has (Schwalbe Stelvio 28mm) also be a contributor? They're pumped up pretty full so I could let some air out, or I could just buy some new (fatter? grippier?) tyres. Would that help with the skidding and falling everywhere? If it would - I'd appreciate any recommendations for tyres to buy as well :) Thank you.
Wet metal plates on the road have an astonishingly low grip, on par with a sheet of ice.
There's very little you can practically change on your bike to improve this - changing to wider tyres at low pressure would help, but the rest of your commute will be like slogging through treacle, and highly unpleasant.
What you can do - change your technique.   Never turn or brake while crossing a metal plate.  Keep the bars and therefore front wheel straight and roll over it.
If the plate is on a corner (and many are)  then try to avoid going over them at all.  Take a left or right position and bypass the plate completely.  Naturally this requires local knowledge and for you to anticipate what's coming up.
It may be possible to participate in activism - write to the local council or similar roading authority, and request the plate be replaced with a textured one, or surfaced with bitumen.  This is a slow process but is not impossible.
Your very last resort is to react quickly should the bike start to slide, and take whatever action helps to restore your balance.  That may be a shift in body weight, which could potentially put you into the path of traffic.  
The counter here is that when your bike is sliding, it happens really quickly and its hard to react in time.
Or find a route that avoids this corner/plate completely.