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Discussion Starter · #1 · (Edited)
Hi All. Two weeks ago (~400km ago :)) I've finally build up bike on Haro Sonix frame, key parts:
Fork: RockShox Reba Air U-Turn 85-115mm
Rear shock: FOX Float R with medium ProPedal tuning
Crankset: Shimano XT Hollowtech II 44/32/22 180mm
Cassete: Shimano XT 11-32
Seatpost: 410mm no setback
Stem: 110mm 5* up
Handlebars: LowRiser 25mm, 625mm wide

Frame is 20", I'm 191.5cm, ~67kg (no it's not a mistake). ~68-69kg equipped.

Suspension setup: 100mm fork travel, sag ~20% for both rear and front (110psi rear shock, 65(+)/50(-)psi fork), fastest posible rebound (and still it's a bit slower than what I want :(, +5..10*C outside), no compression for fork.
Riding position: Cross Country classic, for maximum pedal efficiency (I'll not describe it here, you can find this info in almost every manual, nothing new). Grips are 6cm lower than saddle.

After some try and error I've ended up with setup when there is no or almost no bob on flat horizontal road. I can "freeze" suspension on most gear combinations. There is some bob only when pedal stroke isn't good enough, also suspension bogs down on rapid acceleration in sitted position.

When road goes up I lean forward and apply more force on pedals (suspension become stiffer a bit when you pedal hard). Otherwise suspension tends to bob.

But on steep uphills when I have to slow down and shift to lower gears it suddenly becomes too hard to pedal. Rear suspension compresses more than 40%, front end becomes underweighted and front wheel almost lifts up, suspension bobs and sucks up my energy. I can't climb in sitted position and have to stand up which isn't always appropriate (some uphills are long). Yes, I can adjust fork to 85mm travel, lock it up. It helps, but still too much energy goes to bobbing and there are situations when those adjustments are just not helpful enough.

Ok, you can say that there are limits for every bicycle, nobody can climb a wall :) But I can climb those uphills without any problems on hardtail with 100mm fork travel setting (same setup, actually I've stripped down my hardtail to build up Sonix).

What would you recommend?

PS. Rear shock isn't stock. It's Werx 2007 frame, RP23 shoud be stock, this frame was bought used on ebay as it is now. But I've seen Float R with medium ProPedal tuning on Comp 2008 so it's supposed to be ok...
 

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It sounds like you don't have the correct air pressure in the rear.

Make sure when you set your sag that the ProPedal is turned OFF. Then your sag setting is 10mm.

Lets check this first, because from what you describe your air pressure sounds low.
 

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Discussion Starter · #3 ·
Unfortunately ProPedal on this rear shock can't be turned off :( Plain, relatively cheap Float R, the same model comes stock on 2008 and 2009 Sonix Comp.

I'll try to add pressure with 5-10psi intervals and will see how it affects ride.
 

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Discussion Starter · #4 ·
Yahoo! Found old PDF with setup recommendations.

"WERX SONIX
QUICK SET-UP GUIDE
for Fox Float RP23 rear shock
Virtual Link's suspension geometry dramatically reduces
pedal-bob, while allowing the suspension to remain active
over bumps. This precision geometry is extremely sag sensitive.
An out-of-range setup will dramatically reduce suspension
effectiveness. Sag must be set at 20% of the shock
stroke or 10mm.
1. Inflate spring chamber of the shock to 95%
of your body weight, in pounds
(approximately 155psi for a 170 pound rider).
2. Push shock o-ring on slider up against
shock body.
3. Gently sit on saddle, let bike settle,
give the seat a gentle
bounce to break the air shock free,
let the bike settle and push
(or have a friend push) the 0-ring
against the main shock body.
4. Measure gap between shock body and o-ring.
This is the amount of sag.
a. If sag is greater than 10 mm,
add air pressure.
b. If sag is less than 10 mm,
reduce air pressure.
c. Repeat steps 2-4 until you achieve 10 mm
of sag.
5. Ride!"


67kg / 0.45 ~= 149lbs
149lbs * 0.95 ~= 141psi

My current setup is 110psi, it's definitely lower. Will try 140psi pressure setting next time.
 

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I just built up a Sonix Werx myself. I have my sag set at 10mm with the PP off on the RP23 shock. i experienced the same exact thing you described... "
But on steep uphills when I have to slow down and shift to lower gears it suddenly becomes too hard to pedal. Rear suspension compresses more than 40%, front end becomes underweighted and front wheel almost lifts up, suspension bobs and sucks up my energy. I can't climb in sitted position and have to stand up which isn't always appropriate (some uphills are long)."

If you find a solution, let me know.
 

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Discussion Starter · #7 ·
Cool I am glad you got this figured out. Yes 110 was way too low that was your problem right there. Try 140 psi and come back and let everyone knw how it worked out.
Overall better with 140psi. I'm super fast on flats and downhills :) Even bad pedal stroke isn't a problem, but steep uphills are. No more front wheel liftups but still a lot of bobbing on lower gears.

I just built up a Sonix Werx myself. I have my sag set at 10mm with the PP off on the RP23 shock. i experienced the same exact thing you described...
"But on steep uphills when I have to slow down and shift to lower gears it suddenly becomes too hard to pedal. Rear suspension compresses more than 40%, front end becomes underweighted and front wheel almost lifts up, suspension bobs and sucks up my energy. I can't climb in sitted position and have to stand up which isn't always appropriate (some uphills are long)."

If you find a solution, let me know.
From all info I've gathered on the Net and from discussions with friends I've came to conclusion that "low gear bobing on steep uphills in sitted position" is a design flaw. Any design is a balance between different conditions and Neal Saiki did a great job with Virtual Link. But nothing is perfect. It seems like he did make some compromisses aswell, he traded performance on steep uphills to something more important.

Solutions?

1) Rear shock with lockout or VERY firm platform mode can help.

Here are some extracts from theory:
- Virtual Link will not resist bobing in second half of travel, it's part of design
- On uphills in sitted position rider's weight is shifted to the rear wheel
- Every platform incorporated into rear shock has it's limit, just push hard enough

So on uphills in sitted position rear suspension will resist till the first rock or root. Then ProPedal will give up and allow shock to compress. VL will enter non-platform suspension travel zone and remain there. Too much weight on the rear wheel, shock can't decompress on it's own. To decompress rear suspension rider will have to stand up shifting weight more to the front, after decompression he can sit (gentle!) again. Repeat after next root or bump.

2) Add more air pressure.

Here is another piece of info:
- Virtual Link with excess air pressure in rear shock produce as much bob as it does with 10mm sag setting, downside - ride becomes more harsh.

One have option of sacrificing his comfort to the ability of riding uphills. Could be wise decision if there are a lot of uphills on the course or there is one long (some km long) uphill just ahead (stop, add air pressure, ride uphill, stop, return pressure to normal level).

3) Reduce fork's axle-2-crown length.

Forks with ability to change bike's geometry (Manitou ITA, Marzocchi ETA, RockShox U-Turn...) can also help shift rider's weight more to the front.

Hey, anybody riding Sonix? How do YOU overcome steep uphills?
 

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Discussion Starter · #9 ·
So far 1000km on this frame. Trail riding, Enduro riding (all day long trip through Siberian taiga, without GPS or even compas, only with old maps :p), MTBO-racing, XC-racing...

Not bad. Bobing is not issue in most cases, only when you don't have fresh legs and have to climb on low gears... Last race there were 7 laps. Fist 5 laps I climbed as well as other guys on hardtails. But race is long and eventually you get so tired you have to use low gears and here it is - bobing. Suddenly lose tempo, energy, and postion in the race :(

Also I'd definately recommend everybody rear shock with ability to switch any platform damping off. Medium propedal is a bit too harsh overall even with low air pressure setting.
 

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Great thread.

Thanks for info. I am considering a Haro. Have been reading about the virtual link. Seems that most expert riders find issues on either steep up or downs.
It seems that the uphill issues can be moderated or overcome.
I am interested in how it performs when pointed downhill. When you stand and descend, does the bike stiffen up a lot? Many thanks.
I am tempted to get one of these for my Mrs as a first FS bike. Want her to be able to climb well, but the whole point of FS is for the downhill!.... So need to know how it does there. I read one review that was not +ve, but most users seem happy enough.
Anyway, any comments on the downhill performance when standing would be much appreciated. Thanks again.
 

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Downhill is when the fun part really comes alive, I have no issues with the way it goes down. Still have to work on the way up.

I have the Sonix LT with Monarch 3.3 rear shock, on the uphills, even when it's fully locked (which isn't fully locked anyway, has +/- 3mm or shock travel) it feels too heavy.
 

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Okay, my first ride went okay...learning how to ride and get used to the bike. I had a long gradual uphill, not too steep. Some sections were steeper than others and I just had to suck it up and pedal through it. Downhill was fun but my suspension wasn't dialed in to my weight.

After lunch, My friend helped me dial in the suspension. I had 20% sag both front and rear with 5 inches of travel (front and rear). Hit the trails again and it felt much better especially going downhill...plush!

My psi for the rear is 55. The front is 65 I believe. I'm 5' 7" 140lbs with noodle legs :sad:

On the uphill climbs I almost completely lockout the front and leave the rear at the "Gate" (middle) setting. This seems to work for me.

My second ride was at a different trail with crazy climbs. I had to get off the bike this time in the middle of the first big climb. More conditioning on myself than the bike.

The third time ride was at again another trail with some steep climbs in some sections. Did much better there. I think it's a matter of getting used to the bike. New geometry, WEIGHT, suspension and tires that are all different from the hardtail I moved from.

I'll report back after a few more rides :thumbsup:
 
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