looking for a definitive answer re travel reduction on pike 29+ ? .. TFT unsure

I am looking at reducing the travel of my Pike 29 plus forks (FS-PIKE-RC-B1 – 11T96510874) to as near to 100mm as possible.

I read somewhere online this may be possible by  changing to the 27.5 120mm debonair air spring but I haven’t been able to get a definitive answer yet .

I tried asking Sram tech dept via their enquiry form and they totally ignored me . I asked TFT also but the answer was vague  saying it may or may not work ..which I already knew ! something about possible problem with top out etc .

The 120mm airshaft seems the shortest  readily available in 29+ but I see in the tech documentation that it appears the pike 29+ did come in 100mm options according to the chart ..unless I have misunderstood which is quite possible . I also have a feeling that where I saw that it had been done successfully using the 27.5 120mm ..that may have been on the pike model one before mine and that things may have changed . I have zero expertise in such things and wondered if anyone might have a more thorough understanding or be able to make a suggestion or even give a definitive answer. I could of course just buy the shaft to try but money is tight ..hence the question . I will try and upload the sram chart mentioned earlier for scrutiny . 

Many thanks in advance , Bill in Devon .

i swapped aisprings between 27.5 and 29 on my none boost pikes 27.5×150 became 29×130

this was fine on none boost, I’ve got the feeling its not the same on boost pikes, why not look up air spring part numbers from the service catalogues, see if the same spring is used for same travel forks

and subsequently if the 140 on one is used in a 120 on the other

https://trailhead.rockshox.com/en/specs/11T96510874[/url]

When I bought my Yari 29 plus fork it was 100mm and when I swapped out the airshaft (to make it longer) it was stamped Pike 120.

As to whether this was a 27.5 or 26” airshaft I couldnt say but am happy to dig it out to measure (fnar, fnar)

2023-rockshox-spare-parts-catalog.pdf (sram.com)

page 111 for example

shows the latest designs use the same spring for same travel

I’m still rather confused (unsurprisingly) I will have to strain the grey matter later today unless anyone else has clear views on this ?

the answer is no.. hence why they use the same springs

in none boost models the axle was offset to compensate for the wheel difference size, and thus altered the travel when swapping springs between models

OK ..thanks Alan .. much appreciated . If anyone else has a possible suggestion /fix please let me know .

Get someone with a lathe to shorten the air shaft you have.

Well .. I thought I’d ask TFT again via email this time (as before I rang up and spoke to a technician) and thought maybe with more time  or a different tech I might get a different opinion . I’m really keen to do this if at all possible . This time I got a slightly more positive reply but again they are uncertain .

“Just chatted it through with a technician and we think (all theory based, no actual practice) the 120mm-27.5/130mm-26 air shaft, should (in theory) give you 100mm-29…”

https://www.tftuned.com/2019-20-b1-debonair-air-spring-pike-2014-2017/p3412https://www.tftuned.com/2019-20-b1-debonair-air-spring-pike-2014-2017

/p3412

For some reason I’m still not confident  but unless anyone knows  a reason  the 2014..2017 airshafts won’t fit in the later boost model pikes like my 2019 29+  please let me know so I don’t waste cash ..it would be much appreciated .

I will report back at some stage.

Ok .. after further detective work and research I hopefully have in my hands what is needed. The Pike I have is unusual in that it is based on the Yari/lyric B1 platform and although no longer listed ..there is a 100mm airshaft named DA100 item no 11.4018.010.244 . Ridewill in Italy has some but is ripping folk off  by adding £50 postage ..even if you are in an EU country . I managed to source mine for £70 on eBay.de but they are cheap in the states . However with shipping + tax ..well you know the score . I haven’t fitted it yet and it looks quite different to the 120 debonnaire shaft (I also have), so will need further scrutiny to see what’s what.  HTH’s anyone else looking to do the same . Oh ..and the shaft is inscribed : lyric Yari 100mm , Pike 26 -120mm.

I’ve actually shorted a Yari air shaft just by taking the nut off the end and reducing the length with a lathe. This was on a standard 29″ 120 Yari going down to 100mm.

I bought a new Lyrik, it was a steal but 180mm and I only wanted 140mm.

The dealer (specialist) was happy to change the travel and according to all the blurb we’d both read, it was doable.

But, when they fitted the air shaft it just wasn’t right, so they put a 150mm in and worked fine.

So I bought it with 150mm travel instead – and as it turned out, A-C was only 5mm longer than the 140mm Pike I’d been using.