Hello Sandesh and all concerned,
I just want to give my experience in this issue. The problem is not only in i20s but also in i10s, while driving over the rough patches of the road, particularly on gravel roads.
I own a i10 Sportz which was also having exactly the same issue. After informing Hyundai Coustomer care, I really appreciate their concern as they promptly replaced the steering column. But before that, like yours, the yoke pad and a slightly longer spring were tried first at the bottom part of the column to rectify the problem.
The dealer showed the documents of replacing the steering column, although I was not an eye witness, trust it was done properly. I test driven the vehicle before signing off and found that the sound subsided a great deal, but a hint was still there. To become more sure I drove their demo car, which is also having a similar sound. So I accepted the replacement.
And now one month after the replacement, the sound started to pronounce itself again. I am at a loss what to do now. I test driven 4 i10's and one Ford Ikon near my area, out of which 3 gave the same sound. One i10 Era and the Ikon produced absolutely not sound. Another guy who got his steering column replaced at the same time as mine, is absolutely satisfied with the current status.
It also seem to me that some drivers even do not pay any attention to these kind of sounds and take it for granted that some sounds are bound to come on bad roads.
If this is not a problem and is rather a symptom common with power steerings, I believe the car manual should mention it, as Hyundai has included even the very very small "whining sound" of the steering motor which is only audible while manuevring the vehicle at very very slow speed. This is just a humble appeal from me to Hyundai.
Right now I am driving the vehicle with the sound still there, just with the hope that no major concerns were reported on this beloved car in all over India till now. And I must also say to the tune of SRK, that "the i10 really does not move, but glides", even on average roads, where it is a real delight to drive.
I hope there will not be any terminal issues in future because of this problem. I believe there will be very few who will not accept that that purchasing a car spending 4 lakhs is "once in a lifetime purchase" for many people.