Horrible Grinding from crank

[Paddles1982]

Hi guys and gals, i seem to have a problem with my road bike at the moment, while riding my bike every now and again there seems to be a horrible grinding feeling followed by a slight gear slip causing me to almost come off the bike if i am standing up, i have checked the bolts to make sure everything is tight and as it should be but it is still there, does anyone know the cause of this?

 

[CAMPYBOB]

Grinding? Worn bearings? With the chain removed from the chainrings, the crank should spin smoothly, freely and with no noise. Lack of lubrication to the bottom bracket bearings?

A slipping chain may be caused by a tight chain link(s) or poor derailleur adjustment or alignment. It may also be from worn gear teeth or a worn/stretched chain.

Clean, lubricate and adjust. Inspect for parts in need of replacement. If you can not perform the maintenance yourself, any local bike shop can assist you.

 

[Paddles1982]

thanks for the advice campy bob, i will look into these adjustments later today