Lead Screw Replacement Selection

Gandy

The lead screws on my A5 are bent, so I'm looking for replacements. I know the correct diameter and thread form (T8), pitch (2mm) and length (400mm) to choose, but I'm wondering if there is a optimal choice between a lead of 2mm, 4mm or 8mm (1, 2 or 4 starts, respectively). Obviously, since the factory lead screws have 4mm lead, if I choose different, the z-axis steps/mm need changing.

But apart from that, I'm wondering about the following questions:

1. Are there any advantages/disadvantages in selecting 2mm or 8mm lead rather than the original 4mm?
   
2. Would the printer benefit from anti-backlash spring nuts? Or is the weight of the z-gantry enough for backplash not playing a significant role? I'd assume it could affect print quality when retracting with z-hop, but to what extent?
   
3. If the motor couplers are bent or stretched, what is the best geometry to select for a replacement part? There are types with helical cuts and others with vertical and horizontal cuts available.

Any input is highly appreciated,

cheers,

Andy.

Mutlab

Ciao, mine lead screws are bended too, and I'd like to change 'em.

Are you sure T8/400mm/2mm Pitch?  (https://jgmakerforum.com/discussion/comment/4856/#Comment_4856) 
Thanks in advance

Mutlab

Diameter ：8mm screw

screw pitch：2mm 

Lead distance：4mm

steel length：400mm

Is this ok?

https://ebay.us/jwI8AW

Gandy

Yes, those are the right ones