I have no idea what I'm doing

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  • I wonder

    It's on order!

  • So I have 100mm travel Sid, what do I need to change it to 120?

  • 120mm airshaft. This will point you in the right direction trailhead.rockshox.com/

  • Oh wow, those are crazy low numbers. What size tyres are running 14/17psi?? And er... if you dont mind me asking, what do you weigh?

    I'm relatively late to the tubeless party having only converted last summer. I'm still experimenting with just how low I can go. Of course rider weight plays a part in the lowest pressures you can get away with, I've put on a bit of furlough weight and sit around 95kg kitted up.

    25psi feels like as low as I dare go in the rear right now. Don't have any inserts yet but wondering if cushcore etc really would allow me to run much lower. My rims also have a lifetime crash replacement policy so I'd like to see if I could get away with much lower than 25psi and relish in the extra grip?

    Anyone at or around my weight running super low pressures in 27.5 wheels?

    Edit - should have said I'm running a set of 2.35" tires on one bike and 2.5" on another

  • 20 psi with cushcore xc insert on 29x2.35 at 100KG kitted weight. Seems fine. On 29x3 I run 8 front, 9 back with no inserts.

  • Is it just the second picture that I need? Or the whole assembly like in the first picture?


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  • Just the airshaft, you can re use the rest of the internals. You'll also need some oil for the lowers, and grease for the shaft. Sram butter and 15w if I'm not mistaken.

  • Thanks, I worked as a mechanic for years, but have like zero experience with modern MTBs. Always leaves me confused.

  • Not that they've turned up yet, nor that I have a bike to put them on, but I'm running SC Reserve so have the lifetime warranty, what attracted me to the inserts is the ability to run low pressure without the tyre folding over under side loading, and the promise of killing some chatter - which really killed my wrists on the Megatower last year.

  • really killed my wrists

    They're probably still recovering from that time you rode the Klein

  • Yeah I'm also running Reserve rims. The warranty almost makes me hope I crack a rim to get my monies worth... of course thats silly but it definitely gives some peace of mind experimenting with the pressures. The side load support of the insert is what I'm after.
    I'm lucky enough to have a few short 2 minute steep enduro type runs 10 minutes from home in the car. Lower than 25psi and it gets squirmy and dings to the rim can be felt. From what @pit has said cushcore should give me what I want.

  • They're probably still recovering from that time you rode the Klein

    SDW has nothing on Morzine braking bumps, by the end of the week I was taking some very interesting lines into corners to avoid them.

  • Neil, pls

    As if anything could possibly be rougher than the SDW

  • You've not ridden the NDW then?

  • Went to Bedgebury today - car park is open, as are the toilets, but the cafe/visitor centre is shut.

    The majority of the trail loop is open, but there are a couple of diversions, pleasingly they've not bypassed the sections with jumps, so I'm guessing it's for trail repair rather than risk reduction.

    I'm faster up a hill due to lockdown Zwifting, but I'm much more cautious in the turns and especially in the turns whilst going downhill - I need to regain familiarity with the bike.

    I think I also need to swap back to my Rocket Ron/Hans Dampf rather than the Magic Mary/Nobby Nic, as I have a degree of rolling resistance commensurate with sounding like a Camel Trophy Landie when on tarmac.

    Great to be back in the woods, anyway. I'm going out for a run tomorrow, then might get out on the bike Monday morning - stupidly I lost track of the days and agreed to an important meeting with the German team on Monday (they don't have a bank holiday on the Monday, and I forgot that we do).

  • Also, my Rimpact strips turned up, they're impressively dense.

  • But have you discovered the optimum tyre pressure yet?

  • 25 rear 21 front today IIRC.

  • Ah, I mistakenly thought that the Tyrewiz recommended* pressures, rather than simply informed you what they currently were

    *I've no idea how that would work

  • They're for the Pace.

  • As are the Rimpact strips

  • That's on 2.35 Nobby Nic with the light fast casing, and I weigh 69kg. I'd say for my weight on those tyres that's the best compromise between grip and speed.

  • I have an XX1 10-50 cassette on the Scalpel, with an XTR GS mech - which is meant to be for a maximum of 45 teeth on the largest sprocket. Shimano XTR cassettes are 10-51, and require the SGS mech. Therefore, my mech is five teeth over its rated capacity, and maybe I should have bought the SGS which would be one under its max.

    Has anyone else run this combination and made it work perfectly? I've got minor shifting gripes in the middle of the block which I'd like to vanquish.

  • I knew this before, but apparently I'd forgotten it:

    If you set my bike up according to the Shimano instructions then it doesn't work, as the b-tension setting required to put the upper jockey cage into the specified relationship with the largest sprocket means that when the mech is in the middle of the block the upper jockey wheel is too far behind the centreline of the cassette, and when it moves either up or down the block to initiate a shift, the chain won't follow as the mech doesn't develop enough chain angle to pull it over onto the teeth of the sprocket on either side of the one being changed from.

    What is required is to set the b-tension screw so that the upper jockey plate strikes the largest sprocket when the bike is in the stand, as when your body weight is on the bike and the suspension is in its sagged position the upper jockey wheel plate will be in the correct relationship to the largest sprocket, and the upper jockey wheel will also be sufficiently far forwards in relation to the centre line of the sprocket that it can initiate and complete a gear change, both up and down.

    It still clangs into gear on the smallest two sprockets, but the other ten gears are spot on.

    My jockey wheel cage has "SGS" written on it, but the upper plate of the mech is marked in the same was as the 2x12 version, that has a maximum capacity of 45t, whereas my cassette is a 10-50.

    ^For reference in case anyone else every ends up in a situation where you need to add cable tension to shift up, but remove it to shift down - which I admit puzzled me for a while.

  • New mech arrived- very speedy!

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I have no idea what I'm doing

Posted by Avatar for Dammit @Dammit

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