Yeti 575 Suspension Talk
I’ve had my Yeti 575 since July ‘08. It has undergone quite a transformation from when I purchased it at Jenson USA. I bought it with the Enduro build kit which is basically the cross country package, including Fox 32 Vanilla forks and a Fox RP23 shock.
As my ability to ride more gravity oriented terrain increased, these cross country components became less than able to support my 240lbs in a matter that I would consider safe. The basic issues were torsional flex in the forks, blowing thru the travel of the shock, and severe flexing of the Mavic Crossride wheels.
Solving the fork and wheel issue was both easy and interrelated. For my weight and riding style, a 20mm through axle was mandatory. I also felt wider rims would help solve some of the instability issues along with helping out high speed tracking. The only decision was what brands to use. For the fork I chose Marzocchi 55 ETA’s because of their simple, coil spring design that I could work on and adjust myself. For the wheels I chose Sunringle Str8 Track wheels. You could say they are a tad heavy but for the price that I payed for them, I love them.
These two items very easily fixed the problems that they were intended to. The stability of the bike was greatly increased and the torsional flex issue was eliminated.
In my opinion, weighing over 180lbs puts you at a disadvantage when trying to get your bikes suspension to work for you. Most components arent designed to deal with a rider of my weight, and the amount of tuning help for my weight range is pretty small, especially if you ride aggressively. After doing alot of internet research on Marzocchi forks, I started to grasp the relationship between the different adjusments you can make internally on my forks. Once armed with the basic info it was time to start the actual fork testing.
Let me preface this section by saying that no scientific control methods were used in this testing. It was purely done by feel, subject to all the variations of environment, dirt, fatigue, etc.
Let me throw in one additional piece of advice with these forks, break them in really well. I would say 20 to 30 hours of riding time. They really come alive around that point in time and respond to very small adjustments in setup, so trying to arrive at a final setup before this is a waste of time.
Once I installed these forks on the bike, it was readily apparent that they were way too soft for my weight. From the information that I gathered on the internet, there were only four adjustments I could make to the fork to get it working for me, instead of against me. There isnt an optional spring available so I had to work with spring preload, oil level, oil viscosity, and air pressure preload.
The first and easiest adjustment I made was the air preload. On the right fork leg, under the ETA lever (which will drop the fork 1.5-2 inches and hold it for steep climbs) is the air preload valve. It does require a special adapter which is kind of a pain in the ass but so be it. Im guessing that the standard pressure range in this fork is from 2psi to about 25psi. Marzocchi will tell you that you can go up to 50 psi but over 25psi the stiction gets pretty bad. When the fork isnt broken in yet, 25 psi will seem ridiculously sticky, so I ran 15-18 to start.
At 15psi air preload the fork was ridable. I could still bounce and bottom it, but it was ridable. I had been hoping that it would allow me to ride the fork until it was broken in but it was still too soft. I will add that there is a dramatic difference using this adjustment. Once broke in, a difference of two pounds of pressure makes a very noticable difference in the spring rate of the fork.
The next adjustment I made was spring preload. I made a 20mm shim out of pvc pipe and installed it between the existing spring and spacer. The net effect of this was nothing. I think the spring rate in the fork is so light that increasing the preload is a waste of time. As a side note, there is no firmer spring available for this fork, which is too bad as this seems to be a very good fork for the price.
Next I went after oil level. Air compresses, oil doesnt. Knowing that, I wanted to reduce the amount of air volume in the fork to decrease the compressible space. This will have the same effect as a boost valve on a shock. You can tune your bottoming using this adjustment. I am currently running a 40mm oil level. This is fork compressed with the spring out. With the preload pressure that I have ended up running this might be a bit much.
One thing to keep in mind when adjusting oil level is that your air preload pressure and the oil level interact. Change the oil level and you will need to adjust your preload and visa versa.
The final internal change I have made so far is to change the weight oil in the fork. I waited till I had a lot of time on the fork and it needed a change anyway. It made a slight difference, but not dramatic.
The bottom line on the fork change was that it helped the Yeti 575 alot over the Fox Vanilla fork, but because of a lack of spring options, it never approached being adequate for my weight.
Next up was getting rid of the Fox RP23 that came on the Yeti. I assume that the way I could blow through the rear travel on this shock was due to both the decreasing linkage ratio on the Yeti and the design of the shock itself. In Fox’s defense, I cant imagine this shock was designed for anything but cross country use.
I replaced the RP23 with a Marzocchi Roco TST Air shock. The result was a much livelier rear suspension that didnt use up its travel so fast. Because of the design of the Roco I could use much, much less main chamber air pressure than the Fox. I used around 275psi on the RP23 and with the Roco I used 175psi. That difference alone really helped the small bump absorbtion. It also has an end stroke adjustment that seemed to work, but I think because of the 575’s decreasing spring rate, the shock was over come and would still get full travel.
That being said, I was very pleased with how the Marzocchi components improved the bike.
My opinion of the 575 changed over the course of these changes. By the end of my experementing I came to the conclusion that the 575 is a long travel cross country bike, with all the limitations and lateral flex that comes with that designation. I was never comfortable on steep or rough terrain and always felt like my weight was too much for the bike. Its really too bad as I really wanted to like it. I have since sold the Yeti 575 and bought an Intense Uzzi Vpx. The Uzzi is much more suited to a guy of my weight and I will be talking more about this incredible bike very soon.
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