I really don’t see it being a problem,
Reminds me of the old doctor it hurts when I do this joke.

The 40t is where the 36 would be so the chain line left to right would be the same, so it would ether have something to do with the increased height of the sprocket compared to the chainring or maybe the way the shape of the teeth have been designed and milled, maybe the way they have been designed to easily pick up the chain is what makes it drop off when going backwards and a design tweak could fix it.

The deraileur I can not see having any influence as in normal use it guides the chain on to the sprockets so is on the wrong side of the cassette to influence the chain when pedalling backwards.

I do agree, chip, but I wanted to reduce wear in the top of range so I ordered this

4 X I.D. Outer Chainring Spacers, 2.0mm
1 X I.D. Cr-Mo Chain Ring Bolts (5 pack), 8.5mm (Double)

And it fits a treat on my slx. Noise is reduced and now the chain line is central to the group of gears I spend most time in. However it still drops when back pedalling which I can live with as I only ever crank half a turn to get around objects.

https://www.dropbox.com/s/ait2qejifwlazvc/2014-05-07%2020.15.36.jpg
https://www.dropbox.com/s/j778f7s4wokalfd/2014-05-07%2019.58.54.jpg
https://www.dropbox.com/s/r0x4vbsui706oar/2014-05-07%2019.58.03.jpg

Like doombrain, I spaced out my RF NW with 2mm spacers. I’ve not done this on my other bike, which is also running 1X10, as I use a normal 11-36 cassette. Both bikes use an XT triple with the NW ring in the middle position, but I found by spacing the T-Rex setup inwards it improved overall performance by centralising the chain into the gear range most used and also kept things quieter in the lower gears. By eye, 2mm seems to have moved things inwards by about one cog on the back. I would rather have a better chainline in the lower gears than in the higher ones as this is when I am more likely to be putting greater torque through the drivetrain.

Bang on. Not had a chance to ride yet with, having a ‘on the edge’ wife with two small kids, but doing the edale/Jacobs ladder loop on sat with some mate also running the same setup so will be able to compare.

Good reading, but I’ve gone and ordered a 40T from Hope anyway! Like a few have already said, I only intend to use it for the really steep stuff.
My gearing on my 29er is 36 front with a 11-36 10 speed xt cassette and I’ve run this set up for over two now but as I’m getting older and trying to keep up with the younger riders will I really notice this 40t x 36t combination with heavy legs?

Ive just fitted one of these myself – removed the 17t sprocket as per the instructions and wound the B-tension screw all the way in. Seems to shift ok but struggles to to shift to the 19t sprocket with there now being no 17t.

Im guessing this is the norm and wont shift as smoothly without the 17t sprocket? Ive not re-indexed the gears as it seems to be ok other than the slight hesitation shifting to the 19t sprocket.

My setups a XT medium cage – RF 32 NW chainring – 11-36 XT cassette.

You can smooth out the 15T to 19T change by buying a 16T from RoseBikes, then you get a smoother 13T-16T-19T transition.

http://www.rosebikes.co.uk/article/shimano-xt-cs-m771-10-speed-16-tooth-replacement-sprocket/aid:574089

40T-11T difference is 29T, hence a 3T change per gear is almost exactly right !

Thanks feller – Ill get me one of those ordered.

40T-11T difference is 29T, hence a 3T change per gear is almost exactly right !

Except that the teeth amount increases by a similar percentage as you move up the cassette, not in a linear fashion: So you get 11, 12 and 14 teeth at one end and 28, 32 and 36 teeth (IIRC) at the other (on a 11-36 cassette.

After a couple of weeks of riding, i now have no chain droppage.

Put on 16t cog at back and must say feel the difference would definitely recommend if you can get a hold of one.

Hope retainer 32 tooth with Shimano Deore XT Shadow long cage 10speed only been on 3 rides and has been fine not dropped chain yet. I did not have to touch any thing.

Anyone running one of these with a hope hub had there cassette off after running the t-rex for a while? Just wondering how the free hub body is coping?

Had the T Rex on for 5/6 weeks before I went back to 2×10 for a while. No noticeable extra wear/damage to the hope free hub that I could see.

I was suffering chain drop on the cassette too when back pedalling but it did seem to calm down after a couple of hundred miles.

Still there on the odd occasion but nowhere near as bad as at first.