Largest mountain range in ME
 

Now I have always believed that the Misty Mountains are the largest mountain range in ME, and I think I had seen a quote sometime that said that. But somehow I can't find that proof anymore, and I'm uncertain...

So...what is it ?

If you look at the map I'd say that indeed the Misty Mountains are the biggest, but I don't think I ever red anything about it. I never really wondered about this before...so maybe I have red about it but forgotten it? ah well, I'd say they are the biggest :D

Do the Ash Mountains surround Mordor? Because then they'd be challenging.

They don't, the Ash Mountains are just west-eastern line and the north-south line which is is Ephel Dúath.

The highest mountains in Middle-Earth were Ered Engrin in the First Age, and if the Iron Hills and Grey Mountains were originally a part of them (as it is often speculated, and it is very much possible), they'd be possibly also the largest in the terms of length. However, after the destruction of Beleriand, concerning the length of the mountain range, the Hithaeglir still wound't be the greatest. They were about 700 miles long from north to south, including the mountains of Angmar in the measurement, but the White Mountains were larger in that point - according to Karen Wynn Fonstad's Atlas, they were 852 miles long. And the Ered Luin in the First Age, before the destruction of Beleriand, were more than 900 miles long, thus larger than Hithaeglir even if you didn't count Ered Engrin.

Of course you asked about Middle-Earth, by which I do not mean Aman - otherwise it'd be Pelóri.

the Walls of the Sun would however probably have a similar length as we know they were raised in the East as an opposite to the Pelori in the far west

anyway, thank you for the information, I guess I never thought that the White Mountains include Ras Morthil as well...
if it so, they probably are longer then the Misty Mountains, still if I take a better look, the Ered Nimrais probably are longer

Yeah, the part of Andrast counts as well - and if you look at it, it's really long then. The part of the Mountains of the Sun you mentioned is right as well. I could also add that we have no information about the length of Orocarni - the Mountains of the East, where Cuiviénen was. I don't know if they survived the First Age or other cataclysms (the drowning of Númenor, specifically), but I'd guess they also wouldn't be as short.

Nevertheless, I think the Hithaeglir was possibly the highest at least of all the mountains showed on the LotR map.

Just a small point, as far as the Orocarni are as along as the Blue Mountains were, as you said 900 miles

The Red Mountains were created in the very beginning before the first counting of time when the Valar laboured long and hard to order the world for the coming of the Children. The first design of Arda was to shape it in symmetry, so the Blue Mountains were as long as the Red, and if I remember the correct names we had the Iron Mountains in the north equal to the Yellow in the south. Please correct me if I got something wrong here.

Ah yes, you are right, I forgot. Thanks for the reminder. However, I am not sure about the Ered Engrin thing. It's from HoME I suppose (that thing about Yellow Mountains)? I'm not sure, but I think that the symetry of Valar was more west - mirror - east, not north - mirror - south. I suppose also the White Mountains (more or less, going from west to east, thus, if they were a part of the "original" creation of Arda, they'd have to had a counterpart on the south) were created by some natural (well, "natural"...) disaster.
I also doubt about the Yellow Mountains (I'd be grateful if you find any information about them that you post it here) being mirror to the Iron Mountains, because:
It says explicitely that Ered Engrin were reared by Melkor - so they couldn't be the part of the original "plan" of Valar, thus, not being symetrical with any of the other mountains.
However, it is also said in the first chapter of Silmarillion, that
Which seems that the mountains already were there. Not that Melkor couldn't have first reared the mountains and then started delving and building Utumno - but we are told in the previous quote, that he reared them as a fence, thus, I'd think that he did this after he had something to make a fence around, right?
Perhaps in the first quote the importance is not put on that Morgoth reared the mountains (meaning he "built them"), but to that he reared them around Udun. Ergo, the mountains were there (created by Valar), but he somehow worked on them and changed their ranges, thus, they now created a fence around his new citadel. (I know, a poor assumption. I'd rather stay with the first one - see below.)

One more thing - concerning Hithaeglir and the height of the mountains, as I implied in my previous post.
I wonder if the Hithaeglir was the highest of the mountains in ME? We are not told as much about the other mountain ranges as about the Misty Mountains, from what is described in the Hobbit and LotR, Hithaeglir seems pretty high. And also, we have the testimony of the
Silmarillion 3 - Of the Coming of Elves and the captivity of Melkor:
If we take into consideration that the Hithaeglir was raised by Melkor, then we can assume that it might have been as high as the Ered Engrin (or Ered Engrin could be as high as Hithaeglir). When we are told that they were "taller and more terrible in those days", and what we know from LotR, the Misty Mountains were pretty tall. The main thing I'd assume is that Hithaeglir was much more higher than Orocarni. Why: the Elves have possibly seen Orocarni at their awakening near Cuiviénen, so if Orocarni were as tall or even taller than Hithaeglir, they probably wouldn't be so panicked. Although they probably didn't wander the Orocarni, you are not so awed of something you know. Thus, I'd assume that the elves first saw mountains of that height, so Hithaeglir must have been far higher than Orocarni, which mean also higher than Ered Luin (symetry). Or different way, in the same chapter where we are told about the horror of the elves when they saw the Misty Mountains, there is later laconically written that "Vanyar and Noldor came over Ered Luin, the Blue Mountains", and there is no problem with it. Also I am quite convinced that the Ered Nimrais as well as the Mountains of Mordor were smaller.
What is the most interesting part in my opinion is however the following. Since it is possible that the Grey Mountains were a part of the Iron Mountains of Melkor's (see my post above) and they meet with Hithaeglir near Mount Gundabad, I find it very likely that these mountains (Hithaeglir&Ered Engrin) were actually of the same height! As I implied before, there was no
And one more thing. Maybe you noticed in the quoted text from the 3rd chapter of Silmarillion one connection of words which seems like if we have seen it somewhere before. We are told that the Misty Mountains "were taller and more terrible in those days, and were reared by Melkor to hinder the riding of Oromë".
The same words like those of Ered Engrin, that they were reared by Melkor. If the words have the same meaning here, it would mean that Ered Engrin were really built by Melkor (because of Hithaeglir we can tell for sure that it was not built by the Valar, and if Ered Engrin were "made" the same way...). Thus, this would mean that Ered Engrin wouldn't fit into that symetry of Arda, they were completely built by Melkor.

yes, I read a little bit more and I guess the Ered Engrin were never in plan
as symmetry you have the Blue Mountains in the West and the Red in the East, the Grey in the southwest and the Yellow in the southeast
The only ones made by the Valar that had no range opposing them were the Mountains of Wind between the Red and the Yellow, perhaps to suggest that the right way was to the West and not East
Ered Engrin didn't actually had any range opposing I was wrong about that