So there is this kit available.
https://www.rushcycles.co.uk/m49b0s472p5924/HOPE-Hope-Pro-4-Rear-hub-Boost-Conversion-Kit

Can anyone explain exactly how this works?

From my understanding if the disc is spaced outwards then the cassette isn’t going to be in the right place.

From looking at the kit I’m guessing the end caps add 3mm each and keep the hub centered so no dishing?

I’m not sure, but pro 2 and pro 2 evo are different hubs. It may not work on a pro 2.

The axle in the pro2 evo is different to the standard pro2.

So you’ve got a pair of spacers and some shims to put the rotor back in the right place.

As above, it’s not going to fit an old Pro2 but will fit an Evo.

Yep, you’re going to be getting some additional space on either side of the wheel. The wheel may not end up central (doesn’t with the front conversion kit).

It’s a useful get out of jail, but given that you’re getting the boost sizing without any of the potential strength upside, I’d view any adaptor kit as a useful get-out-of-jail for swapping wheels around rather than a proper solution to a new frame and a wheel that doesn’t fit. By the time you’ve sold your old hub and not bought the adaptor it wouldn’t need to be a very expensive change.

Most of the convertors available (like the wolftooth/lindarets boostinator) are asymmetric i.e. the extra 6mm goes on the disc side, space the rotor out and re-dish the wheel. It does actually get some of the benefits of wider flange spacing as the triangulation is better.

However, it does look a little like there are two spacers in that kit which may suggest a symmetric offset. If so that would be grand- I have a +5mm each side plus rotor spacer to fit a normal wheel in a boost fork and it’s been fine. Easy to convert back too.

You could ask hope? I think the product reference on their website is ‘HUB493’ but I can’t see any drawings/details.

I have one of these kits arriving in a few days time.
I was under the impression that it was just a longer spacer for the brake side and spacers for the rotor. Then you re dished the rim back to the center.
I’ll let you know when it arrives.
I think the silver drive side spacer in the pic is to convert from 135QR to 12×148 and you don’t need to use it for a 12×142 to 12×148 conversion.

Picked the kit up from my LBS today.
Looks from the instructions like no re dishing is required.
I’ll try it out tomorrow to find out for sure.

[url=https://flic.kr/p/HwFUok]2017-12-13_05-06-56[/url] by multispeedstu, on Flickr

Mtbtools on eBay is a gold mine of adaptor kits. I’ve used him a few times and he seems to have them all.

It’s a useful get out of jail, but given that you’re getting the boost sizing without any of the potential strength upside, I’d view any adaptor kit as a useful get-out-of-jail for swapping wheels around rather than a proper solution to a new frame and a wheel that doesn’t fit. By the time you’ve sold your old hub and not bought the adaptor it wouldn’t need to be a very expensive change.

I disagree with this. Boost makes a small difference to 29″ wheel stiffness but hardly any to 27.5. The big (and perhaps unplanned) advantage of boost is frame designers being able to make frame pivots and chain stays wider and stiffer.

You’ll still get all of this benefit with a spacer kit

Edit – the spacer kits don’t work with non-evo pro2s because the hub shell has a different lip for the non drive side spacer, not because of the axle (axle is only different to evo on the free hub bit). Took me a while to figure this out!