Hope Pro 4 20mm to 15mm conversion…..

I’ve picked up a set of wheels which has a Hope Pro 4 front hub currently in 20mm guise.  The front hub is non-boost but the 20mm end caps enable it to be run boost.

I’m converting it to 15mm, I’ve bought the end caps and the boost converter.  Assumed I’d just pop the 20mm caps off, replace with the 15mm caps and possibly redish the wheel. Having removed the caps I’m confused, the 20mm caps are wider than the 15mm (inc the boost cap).

Having offered up the wheel to my 15mm axle forks and tightened up I can feel a little play (maybe bearings need replacing but they seem ok), which is further making me thing something is not quite right.

I can call Hope tomorrow but any ideas in the meantime.

Not sure what’s going on here, old school 20mm was 110mm wide as is boost 15mm so yes you should have the same “thickness” of spacer before and after.

Hope convert for boost by adding a longer spacer to one side only and dishing, so you should have one old spacer and one 10mm longer spacer. So comparing the length of the 2 15mm spacers could be useful?

I can’t tell if it’s a trick of the photo or not but the 20mm definitely looks “thicker” than the 15mm. (the relevant measurement isn’t flange to flange though, ie widest part of both- the 20mm ones fit flat to teh bearing while the QR ones have a little step- so the relevant measurement is the sidest part of the 20mm adaptors, compared to the point where it fattens up on the 15mm ones)

But the best thing of all is just to measure end to end. That’s kind of fiddly to do because it’s all too fat for rulers or calipers, but if you’ve got a decent sized G clamp you cna usually use that as your “caliper” then measure it.

Usually I’d wonder if you’ve got parts for different hubs but Hope used the same parts for several generations in there so interchangability should be good. Albeit there was always some weirdo options to make it more confusing. But you oughtn’t to have play in the hub because the pro 2 hub is bsaically a solid stack of spacers all teh way through. If the spacers were the wrong length it would be too wide or narrow for hte fork but that should only create side-to-side slidey play on the axle, not play in the hub.

Thanks Northwind, 20mm being 110 spacing from the start answers why the 20mm spacers are equal size vs the 15mm boost using different widths.

Basic measurements make the shell 80mm wide and the new spacers 1x20mm and 1x10mm.  Also makes sense with the stepped part sitting against the bearing rather than the flange on the new spacers, which by the photo would make them a similar width (I was looking flange to flange). So in theory…..

I’ve ordered some new bearings to see if they were the reason for the slight play and report back.

I use one these on a 20mm front wheel to run it on 15mm axle forks.

Works perfect.

https://www.ebay.co.uk/itm/235328600243

Is it because the 20mm fits with circlips while the 15mm doesn’t? I.e. are you measuring from the face that sits on the bearing in each case?

@dave_h that’s interesting as it would allow me to run the wheel without a re dish so I could use the original 20mm forks as spares.  How does the 20mm end cap work interfacing with the dropout on a 15mm fork ( unless a RockShox with a torque cap option) – I’m using a Fox 38?

Swanny – yes I think I that’s potentially the answer to the caps looking different widths. I’m hoping the movement when wheel is fitted will be resolved with fresh bearings.

So the 20-15mm converter won’t work with my forks, they’re machined on the drop outs to accept a 15mm end cap, 20mm is too big.

Fresh bearings, 15mm converters and a redish it is.

So the 20-15mm converter won’t work with my forks

Did you try to fit it?  I’ve ran the wheel with the adapter in Lyriks and Zebs without any problems whatsoever.

Did you try to fit it?  I’ve ran the wheel with the adapter in Lyriks and Zebs without any problems whatsoever.

Yes I did, RS forks have the ability to run the torque caps which are bigger so have more space in the dropout (my previous Zebs came with little screw on plates to run standard 15mm), the Fox forks don’t.

I did change the bearings which sorted out the play issue.  All this is now moot as I subsequently found out the rear the rear rim was shot (cracked) so I may as well sell on the front wheel (the rear is a boost Pro4 which I’ve rebuilt) and either build or buy a set with a proper boost front hub.