Context :

Aims : Previous studies of the X-ray flux and spectral properties of 1RXS J170849 - 400910 showed a possible correlation with the spin glitches that occurred in 1999 and 2001 .
However , due to the sparseness of spectral measurements and the paucity of detected glitches , no firm conclusion could be drawn .

Methods : We retrieved and analysed archival Rossi-XTE pointings of 1RXS J170849 - 400910 covering the time interval between January 2003 and June 2006 and carried out a detailed timing analysis with phase fitting techniques .

Results : We detected two large glitches ( \frac { \Delta \nu } { \nu } of 1.2 and 2.1 \times 10 ^ { -6 } ) that occurred in January and June 2005 .
The occurrence times of these glitches are in agreement with the predictions made in our previous studies .
This finding strongly suggests a connection between the flux , spectral and timing properties of 1RXS J170849 - 400910 .

Conclusions :