Bicycle Mechanics - Can I safely replace RD without this thingy: (see pic)

I want to replace a Deore with an older XT derailer - so they're a bit dissimilar. I understand that a special tool for aligning the derailer may be needed. The picture below shows that kind of tool. My question is: do I really need it? How much easier will my work be, with it?

That is a nice pic of a guage, doesn't really have anything to do with the question but, here goes. All Shimano rear derailluers have the same pull length except Dura Ace 8 speed. So, you can swap Deore XT for a Deore. You won't really notice any improvement though. Good luck

Tim

I want to replace a Deore with an older XT derailer - so they're a bit dissimilar.

Actually, after reading this again, I see it is a very lame attempt at humor.:( Ha Ha


Tim

Actually, after reading this again, I see it is a very lame attempt at humor.:( Ha Ha


Tim

No, that wasn't my aim. I really would need an answer to my question.

If the derailleur hanger is aligned, it is aligned. It doesn't matter which derailleur you are mounting on it.

Unless your hanger has been bent, it doesn't need to be aligned again.

How did you come to the assumption that you need to realign the hanger for a different deraileur?

With that said, there are probably some people who say you should align every time you do anything, but I think unless you are noticing an issue related to alignment, it is overkill.

If the derailleur hanger is aligned, it is aligned. It doesn't matter which derailleur you are mounting on it.

Unless your hanger has been bent, it doesn't need to be aligned again.

How did you come to the assumption that you need to realign the hanger for a different deraileur?

With that said, there are probably some people who say you should align every time you do anything, but I think unless you are noticing an issue related to alignment, it is overkill.

Thank you. I was mistaken in thinking that I would need to realign the hanger when I replace a derailer. I was wrong, and I thank you for explaining that to me.

No worries on asking the question.
But it would be a more interesting (and frustrating) world if derailler hangers needed to be aligned anew for each derailler. Would be a big problem for all non-steel frames.
Some cheaper bikes that may have poor dropout alignment usually don't have derailler hangers, either - the "removable" derailler hanger (claw) is built into the top of the derailler itself for bikes like that.

Brief summary: If the bike shifted ok with the old derailleur, it will with the new one too.

Can you safely remove the RD without the thingy?

Why yes, but only if you are wearing a helmet, safety glasses, and kevlar lined gloves.