hi there new on here after sum help so here we go there is a big allen key bolt that holds the discs on does any 1 no what size it is the car is a 03 a4 estate

 

The one that holds the disc in place?? isn't that a really tiny one? like a 6mm??

 

Could it be the wheel nut he is referring to? It it is, I think that is 17mm.

 

hi thanks for the replys think we r confused remove wheel then in the middle of the brake disc there is a metal cap remove this then there is a big allen key head looks like the wheel bearings are behind it looks around 17mm 18mm 19mm or 20mm hope this helps

 

Thats the axle bolt.. I think its 17mm.

 

Is either a 16 or 17 mm, make sure you have from a 15 to 18 just in case and you will need a breaker bar...

 

Maybe he means the caliper bolt to swap out the pads?

 

The axle stretch bolt is 17mm and one time use. Must be replaced when you remove it since it stretches under torque. You don't need to remove it to do the brakes. only if you changing axles or wheel bearings.