Recently changed the chain and cassette on my road bike. Its the same range 11-25 (I think). Its a cheapo 9spd sunrace cassette and a 9spd SRAM chain.
When putting some pressure on the pedals or just standing up to pedal and in the smallest sprocket, it tries to change up / skips a bit. Doesn't make any difference which chainring at the front.
Its fine on the work stand, shifts up and down fine, but actually pedalling hard and it keeps trying to shift.
Could it be a poorly made cassette?
Any ideas?

