ElasticSearch Jest Client Read Timeout

Question

My config in jest 2.4 ES 2.4

JestClientFactory factory = new JestClientFactory();
     factory.setHttpClientConfig(new HttpClientConfig
     .Builder("serverX:9200")
     .multiThreaded(true)
     .defaultMaxTotalConnectionPerRoute(75)
     .maxTotalConnection(75)
     .readTimeout(20000)
     .build());

I have like 50 threads doing ES queries. They constantly Read timeout. If I leave the defaults.. kind of work better. It just timeouts 1 of every 3 or 4.

Is probably issuing 1 query per second or more. Any clue ? Doc on how are the defaults is not quite easy to find ?