Im living in a village so my ISP using wi-fi bridge to connect me.
I have this situation always in a day time. At night ping to google is about 60.

http://i.gyazo.com/1a194cc9cc24f91dd93359b0878e7611.png
1 hop - my router
2 hop - ISP's intermediate PC
3-5 hops - ISP

There's always spike on 3th hop, but it's doesnt affect next hop somehow.
Further hops have higher ping, but the last one have not.
In fact I have very high ping.
I guess answer lies in poor bandwidth, but I found it strange that 4 and last hops have good ping in a whole picture.