nginx and rails : 400bad request

Question

Im using nginx and rails for my site which contains url with georgian letters ie განცხადებები so something like http://gancxadebebi.ge/ka/%E1%83%92%E1%83%90%E1%83%9C%E1%83%AA%E1%83%AE%E1%83%90%E1%83%93%E1%83%94%E1%83%91%E1%83%94%E1%83%91%E1%83%98 It is mainly working perfectly but sometimes I receive request with truncated url ie 1 - http://gancxadebebi.ge/ka/%E1%83%92%E1%83%90%E1%83%9C%E1%83%AA%E1%83%AE%E1%83%90%E1%83%93%E1%83%94%E1%83%91%E1%83%94%E1%83%91%E1%83%9 (as u can see it should be something after %9) or 2 - http://gancxadebebi.ge/ka/%E1%83%92%E1%83%90%E1%83%9C%E1%83%AA%E1%83%AE%E1%83%90%E1%83%93%E1%83%94%E1%83%91%E1%83%94%E1%83%91%E1%83%98?mc=mini+aipadi&search=%E1%83%AB%E1%83%98%E1%83%94%E1%83%91%E1%83%9

I succeeded to deal when there is no get parameters (first url above) and make in that case a redirection to / when this happen, this line is added to nginx error.log 2013/09/24 00:46:53 [alert] 63547#0: *19359227 pcre_exec() failed: -10 on "/ka/განცხადებებ�" using "", client: aa.bb.cc.dd, server: gancxadebebi.ge, request: "GET /ka/%E1%83%92%E1%83%90%E1%83%9C%E1%83%AA%E1%83%AE%E1%83%90%E1%83%93%E1%83%94%E1%83%91%E1%83%94%E1%83%91%E1%8 HTTP/1.1", host: "gancxadebebi.ge"

but for second url, which have get parameter truncated, I can not handle that which generate a 400 bad request page. such request added this line in nginx access.log aa.bb.cc.dd - - [24/Sep/2013:00:48:47 +0200] "GET /ka/%E1%83%92%E1%83%90%E1%83%9C%E1%83%AA%E1%83%AE%E1%83%90%E1%83%93%E1%83%94%E1%83%91%E1%83%94%E1%83%91%E1%83%98?mc=mini+aipadi&search=%E1%83%AB%E1%83%98%E1%83%94%E1%83%91%E1%83% HTTP/1.1" 400 5 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.76 Safari/537.36"

does this mean that nginx accepted the request and then rails coudnt resolve it ?

I don't know if problem come from rails or from nginx. For first url, I solved it in nginx conf here part of my conf

access_log /var/log/nginx/gancx.access.log;
error_log /var/log/nginx/gancx.error.log;

client_body_in_file_only clean;
client_body_buffer_size 32K;
charset UTF-8;
source_charset UTF-8;
client_max_body_size 300M;



error_page  400 404         = @notfound;
error_page  500 502 504 = @server_error;
error_page  503         = @maintenance;

location @notfound {
  rewrite ^(.*)$ $scheme://$host permanent;
}

location @server_error {
    rewrite ^(.*)$ $scheme://$host permanent;
}

location @maintenance {
    rewrite ^(.*)$ $scheme://$host permanent;
}
sendfile on;
send_timeout 300s;

location / {
    proxy_pass http://gancx;
    proxy_redirect off;

    proxy_set_header   Host             $host;
    proxy_set_header   X-Real-IP        $remote_addr;
    proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
    charset UTF-8;
    client_max_body_size 7m;
    proxy_buffer_size          4k;
    proxy_buffers              4 32k;
    proxy_busy_buffers_size    64k;
    proxy_temp_file_write_size 64k;
}

thanks for your help