Solid state relays

[saaz]

An article on the advantages of solid state relays in some situations

http://autospeed.com/cms/A_112737/article.html

[Brock]

SSR are a handy device, but the are large, and when they fail they can cause problems that can be  difficult to fault find (Been there and done that).

They are not really suitable for use on a bike where space is limited. SSRs must have a load to work as well.

[Whizz]

I agree, also SSR's are far more expensive than standard relays, and for the number of operations required when fitted to a bike the standard mechanical relay is just as reliable as a SSR.

[DaleMcLean]

We could always make our own with FETS (LOVE FETS  ).
TO220 packs are good for 15A or so (or better)