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Springrate dilemma, Ohlins TTX on '06 YZ250

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This may sound odd but lowering the yz about a inch really helps turning, esp in the corners you mention , I went to the different offset as well and it worked well but no rmz

Mog, funny you mention that about the YZ's.

I just put an Ohlins TTX shock on mine, and when I first put it on I was in a huge rush to get out to a race and never got to check the sag. Felt really damn good. Within some clicker tuning of being great. Improvement everywhere.

Then I checked my sag. 50mm/125mm for static/rider. Damn...

Set it at 25mm/~100mm. Went for a ride today. &%$#@!. All over the place. Sketchy as all hell. Unstable in corners. Couldn't even tell how the front end was knifing because the back end was just all over the place. On the descents the back end felt like it was coming off the ground through any rough stuff and wouldn't get braking traction coming into corners.

Why is everyone so set on 100mm of sag for bikes? Every bike I've set up with "proper sag" has ended up feeling terrible. I think you might be onto something with this lowering idea. I've read in a few places lately about the fast pro offroad guys running a softer spring, and getting numbers around 25-30mm static sag and around 115mm rider sag. Care to tell more about your testing with it (or have links to old threads with discussion about it)?

This was posted in another thread below and I'd like some more input on this.

I weigh 180 in gym shorts, ~205 geared up with camelback.

'06 YZ250 with 3 gal tank, guards. Ohlins TTX front and rear dampers. This is made to be a purpose built off-road bike. Mostly rough twisty fast singletrack with occasional desert racing.

0.46kg springs up front, 5.3kg rear spring presently

I like to ride fast and aggressive, but flowing with the terrain. I don't just lock my knees and expect the bike to do everything, but I expect it to be predictable.

Basically went from 125mm rear sag to 100mm rear sag (with 25mm free sag) with the same spring, and the ride went from really good to total hell. Unstable, skittery, hyper, jumpy, phenomanal traction to total LACK of traction, call it what you want. My gut instinct is that this comes from way too much preload on the spring as it seems to be the top bit of the stroke that has lost all its plushness and composure.

So, do I want a stiffer spring to get this thing at a better ride height with less preload on it? Or just ride it sacked out where it lets me ride the fastest? I'm literally covering ground and nailing corners twice as fast or more with the lower setup. The only drawback I found to it is that it wants to "endo" a bit on bigger rollers or whoops.

What sag numbers do the pro riders ACTUALLY run? I've heard from a few well-informed sources that not a single one of the offroad guys or even the SX/MX guys are running 100mm sag - they're all lower, whether it's by springrate or by internal spacer just for geometry reasons.

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105 is more the norm now days, Upto 115 is reasonable on a linkage bike , if its endoing on rollers it maybe comp too soft so going too deep into the stroke, or the rebound is too fast or both

The spring looks good to me

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The rebound was quick in stock form. I slowed it down 2 clicks and it helped, but I had the same thoughts you did about it going over the rollers.

I will try 40/115 next time out and see if that's a good medium.

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i only setup 4-st, just test it, move stuff around and write down what it did, get the proper spring rate, .......if your riding off road with ttx stuff than you prolly need it revalved, it is setup for mx..........check around your area for tuners familiar with ohlins

Edited by dunn2500

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The shock has already been valved for offroad by a reputable tuner. The fork cartridges are stock.

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if you run more sag need stiff shock for dont go deep.

i use rear sag from 100mm to 110 on all mx bike then ktm.

for wood here the sag is 110mm to120mm

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I have found that either i like more rear sag for my riding style, or the Yz's like more rear sag for woods/off road racing,

I also have a ttx on my 2010 yz 250 2t, I run 110mm rider @ 38mm static and its great (bike used for enduro racing)

I also run more sag on my 2011 yz 450 with a PC lowering link, I have 108mm rider @ 30mm static, I could probably go one stiffer but its good as is for now,

I also used to run 100, with 25-35mm rider and It was not good, somehow i think the Yz's need to be almost leaned over more to get them to turn, and if the sag is low (100mm) the front knifes and there is almost no traction on the rear

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Yes the yz will not turn at 100mmsag , no one shiikd be using 100 any longer, 103 is about the least sag on modern bikes

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I also used to run 100, with 25-35mm rider and It was not good, somehow i think the Yz's need to be almost leaned over more to get them to turn, and if the sag is low (100mm) the front knifes and there is almost no traction on the rear

This was precisely my feeling with the bike set at 100. Top heavy, fights a lean, but still has knifing issues up front and the rear wants to step out like a mofo. I felt like a retard riding the thing after having set it correct the other day knowing that was how it was "supposed" to feel and I somehow wasn't seeing any benefit to it at all. I'm glad there are others noticing the the same things - makes me feel sane again.

If I could get the bike set as stable and aggressive as I had it before with it sagged way low and solve the endo-ing issue on rollers, I would be VERY happy with this bike. Hoping this is the fix.

On a side note, I'm going to get my hands on a CR250 and an RM250 this next week and take geometry measurements of those two and my bike, and throw the linkage measurements into one of my programs and see what (on paper) all the differences are between all of them. Head angles, front centers, offsets, wheelbases, swingarm lengths, ground clearances, etc. Just riding around a bit on both bikes, they feel weighted SUPER low compared to the YZ. Sitting in the bike versus sitting on it. Granted I have a tall seat and a 3 gal tank on mine, but I remember how it felt with the normal seat and tank.

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Some quick internet research on the subject offers me this:

Measurements for head angle; wheelbase; ground clearance; seat height.

'06 YZ250: -27.0deg; 58.3"; 15.6"; 39.0"

'07 RM250: -27.5-28.0deg; 57.9"; 13.8"; 37.4"

Basically, the YZ is one tall, long, steep SOB compared to an RM which you're basically sitting IN. I have no idea how accurate these numbers are, but the height difference is pretty staggering knowing that these two bikes like the same sag.

Almost 2" taller at the pegs and the seat. Half a degree to a degree steeper in the head angle, and some fraction of an inch longer in total wheelbase (hard to tell if that's in the swingarm or in the main frame).

I think this whole "raise the rear and lower the front to get the bike to corner" approach is actually going the wrong direction, but is still getting the "knifey" feel that people think they want out of it. Going to try a bunch more testing this weekend.

Anyone have experience using a Yamalink on these to lower them? Any ill effects of it?

Edited by GHILL28

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