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Discussion Starter #1
Been doing some research, but I can't seem to find this answer.

I have a Reba RL Solo Air 100mm that I believe is a 2014 (serial 21T43898342) but could be a 2015 (date on the RS sticker on the box is 2014/05/23). It is a 1-1/8" straight steer tube, 100mm, 26" QR, model 00.4018.787.000.

Rock Shox doesn't appear to have made a straight-steer tube 27.5 Reba RL 100mm from what I can find in their Spare Parts manual for both 2014 and 2015, though they made a 26" with straight tube (i.e. mine). Would it be possible to build a 27.5" RL 100mm Solo Air with a straight steer tube by using the CSU/crown from a 26" of the same year and travel? I'm going to continue researching as best I can, but I thought some of the knowledgeable folks here might be able to shed some light. I'm working on a one-off project where this would be required. Thanks for any help you guys might have.
 

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Discussion Starter #2
Ok, with some further research, it appears that there is a 2016 Reba 27.5 with a straight steer tube, per the 2016 RockShox spare parts file. This has me wondering if the p/n change is for the labels that might be on the crown, or perhaps the 27.5 and 26 use a different offset. I understand the effects of the offset, so I'm still looking to see if the 26" straight tube CSU is compatible with the 27.5" entire lower assembly, offset notwithstanding, for the year of my fork (which still seems to indicate 2014).
 

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Having read the other post and looked around I can't say for certain, but since every 32MM upper from RS is the same the only thing left to determine is the bushing respective heights of both the 26" and 27.5" lowers. While I believe that it not a good idea to take a 27.5" lowers and mate it to a 26" CSU because of a potential arch-to-crown contact under use; I haven't tried it. That it _may_ work for the _most_ part is not relevant, safety is; yours and any person who gets onto that bike. That being said: I suspect that the bushings will not be located equidistant on both lowers. But correct me if I am wrong!
 

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Discussion Starter #4
On the 26" Reba, the strange thing is that the crown clears a 27.5 tire at full compression with ease, but the lowers' arch does not. It rubs the 27.5 tire as soon as you try to put it into the dropouts. Usually I have the opposite problem when testing a fork for 27.5 capability - arch clears, but then you get contact with the crown at full compression (and at that point I know that fork can't use both tire sizes). My expectation is that the 27.5 lowers are longer overall, and of course the arch is designed to clear 27.5 tires.

I could potentially see RS designing the lowers so that all 100mm forks use the same length internals and they just situate them differently in the appropriate lowers, but that's a big assumption to make. I think going 26 to 27.5 on the same travel is much more likely to be possible than changing travel as well, but again this is all a SWAG.

Sadly, unless someone has already tried this, the only definitive way to answer this will be to buy a same-year 27.5 and try it since I'm sure RS isn't going to cough up the info due to liability reasons.
 

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Sorry for bumping a really old thread.

But did you try this? I have an old bike that I'm trying to fit 27.5" wheels onto and would really love to go with a reba or SID fork. But finding a good 27.5" fork with a straight steerer is difficult.
 

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Discussion Starter #6
I bought a 27.5 Reba of pretty much the same time frame, but I never did the swap. Looking at the parts didn't fill me with confidence that the swap would work. I ended up going a different direction with the project, but I do still have the two forks.
 

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I bought a 27.5 Reba of pretty much the same time frame, but I never did the swap. Looking at the parts didn't fill me with confidence that the swap would work. I ended up going a different direction with the project, but I do still have the two forks.
Can I twist your arm and get you to test it? Or are you interested in selling the forks?
 

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Discussion Starter #8
Sorry for the slow reply. I've allocated the forks to other builds; I won't be swapping them. I didn't get a great feeling of success by having the two in the same place. The 27.5 damper side assembly seems much longer than the 26er, more than the 0.75" of leg length would seem to require.
 

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No problem. I bite the bullet, ordered an adapter kit, reamed out some carbon fiber in the head tube and purchased one of the NOS sids on amazon for $350. Problem solved and it’s a nice upgrade over the Tk 30 silver fork
 
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