The prospect of another official rate rise in the next six weeks could forestall plans by some banks for an out-of-cycle rise in Australian variable mortgage rates.Westpac and Commonwealth Bank of Australia are widely believed to have been considering raising rates out of cycle - that is, independent of any official rate rise. Such a move would help restore margins damaged by increases in funding costs.But out-of-cycle rises would be likely to attract fierce public criticism, especially coming on top of recent higher profits and controversy over CBA chief executive Ralph Norris's pay.A 25-basis-point official rate rise in October or November could allow some banks to push up mortgage rates by 35 basis points. That would likely attract less criticism than a 10-basis-point, out-of-cycle rise.Analysts such as JP Morgan's Scott Manning have also noted lenders' attempts to improve margins in other ways, such as by changing how they price loans for risk.Statements by the Reserve Bank of Australia this week have financial markets betting that the next official rate rise will be delivered by November, rather than next year. On Monday, RBA governor Glenn Stevens said the RBA would probably have to use interest rates to help manage a "fairly robust upswing". Yesterday's RBA minutes showed the central bank expects mining investment to help drive growth, with "significant flow-on effects to the broader economy".And HSBC Australia chief economist and former RBA staffer Paul Bloxham predicted not only a 25 basis point rate rise this year but also a full one per cent worth of rises through 2011.