Lenders may be beginning to wonder whether they have tightened the screws on residential property investors too much, with news of another big fall in investor mortgage lending.According to the latest Australian Bureau of Statistics housing finance data, the value of new mortgage lending to investors fell 6.1 per cent in October, compared with the previous month (in seasonally adjusted terms).This follows a month-on-month fall in new investor mortgage lending of 8.5 per cent in September. It is the sixth straight month of falls in new lending to residential property investors.Meanwhile the value of new lending to owner-occupiers was up 0.4 per cent, compared with the previous month.Overall, total new housing finance commitments were down two per cent in October, compared with the previous month.Lenders settled A$33.6 billion of mortgages in October - 8.4 per cent more than the same time last year.The average loan size was $382,400, compared with $379,400 the previous month and $336,100 a year earlier.First-home buyers made up 15.1 per cent of the market.