SRAM Eagle B Gap - Do you really need to compress rear suspension?

pygmypony

pygmypony

Well-Known Member
hey all,

My 2019 Pivot Trail 429 (SRAM Eagle XX1 12 sp, 10-50) was shifting beautifully for the last few months...however, recently, it's been slow on outboard shifting...HOWEVER, this only happens when i'm riding it, NOT when it's in the stand.

in the stand it shifts buttery smooth, but as soon as i roll out of my garage, the outboard shifting is slow.

this feels like it's not a cable tension issue, but a B Gap issue...i have the red plastic SRAM B Gap guide, and SRAM's video tells you that you need to compress the suspension, but i've heard different points of view on that...

wondering if anyone has had any first hand experience with this?

thanks in advance!

joe c
 
Paul H

Paul H

Fearless OOS Poser
I set the b screw w/o compressing the rear shock and it works perfectly fine.

One thing you might want to check... is the rear axle and see if it is tight.
Had some shifting issues and it ended up being the axle not torqued to spec.
 
pygmypony

pygmypony

Well-Known Member
Paul H said:
I set the b screw w/o compressing the rear shock and it works perfectly fine.

One thing you might want to check... is the rear axle and see if it is tight.
Had some shifting issues and it ended up being the axle not torqued to spec.
Click to expand...
thanks for this! i've checked rear axle, have a relatively new cable, limit screws...shifting inboard works flawlessly...shifting outboard in the work stand works flawlessly...shifting while seated on the bike, outboard super slow, and only on the smaller cogs. driving me batty
 
FastFreddy

FastFreddy

Well-Known Member
I never compress the suspension on my mine when setting the B screw. I did notice if I didn't set the the high limit screw right it would shift slow when dropping down to the smaller cogs. The pulley needs to be just outside of the smallest cog on the cassette not centered on it. From there I just tweak the adjuster on the shifter 1 or 2 clicks at a time till it shifts good. Also when I cut a new cable I use an awl to open the end of the housing back up so the cable doesn't bind on it. The ferrules on the housing ends sometimes will bind the cable a bit too if the hole isn't centered or the housing isn't cut straight. Any extra drag will stop/slow it from dropping down to the smaller cogs.
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pygmypony

pygmypony

Well-Known Member
thanks for all the feedback! i tweaked my B GAP measurement and the high limit screw (i was probably playing a little too fast and loose with the measurements), and even a little bit of the cable tension, and it's shifting much better up and down my block! will give it a test run tonite or tomorrow.

lessons learnt...1) 1 or 2mm seems to make a big difference when you are talking about a 15mm B GAP...2) always listen to @jimvreeland 3) see #2
 
pygmypony

pygmypony

Well-Known Member
and another update on this...after getting new cable and housing installed...outbound shifting went back to poop...

i toyed again with cable tension, but again, shifting from smaller to larger cogs was perfect...it was just larger to smaller that was slow as molasses.

a half turn of backing off tension on the bgap (making the gap ever so smaller than the tool would indicate) seems to have cured the problem - one ride this AM, no ghost shifting...

lesson learnt, i think...while i did not set the original bgap with sag, i think this post adjustment, adjustment (ie another 1/4 or 1/2 turn) seems to be accounting for that - reducing the original gap by another 1 or 2mm...so, maybe the pivot requires bgap to be set with sag, as that seems to have cured my lousy shifting twice...

oh, also, out of frustration, i just ordered the AXS X01 upgrade kit...so will be ditching cables soon, and will only have bgap to blame going forward!
 
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