ok car seems to have less grip under braking than before!

now its got eagle F1s on 3/4 corners.. the rear left is a shit tyre ona spare wheel (which has f**k all grip) but i'd expect that under braking one rear tyer dont make much difference?

before the car stopped LOVELY... now the abs kicks in under hard braking...

can tyres loose grip, or is it likely the shit rear tyre is the cause of my problems? (this thing really has NO grip!)


ps its only on there as a spare whilst my wheel is being repaired