The new XT 11spd cassettes are 11-40 or 11-42 and the standard front chainring options are only 10t apart (24-34, 26-36, 28-38) though I daresay you could mix and match for a wider spread. So if you have 11-42 cassette with 26-38 this would make a range wide enough for almost anything rideable but it needs a RD with at least 43t capacity. Then, depending on your bike's suspension, you may need to leave 1t or 2t free for suspension related 'chain growth' . So, 45t..... I don't need this much range for normal riding on prepared tracks but its useful for exploring Lesotho's goat tracks and for those like me who lack general athleticism .
