2015 YZ450 Suspension advice

Lighter springs require lighter(less) rebound damping as you say. The forks will pack because the lighter springs will not have enough force to push past the heavier valving for the heavier springs. Packing will cause harshness, headshake, and will disturb handling characteristics.

You can run a rate down from factory without changing anything but you'll have to run the rebound clicker way out (like 17-18 clicks) which increases midvalve bleed and can have some negative side effects such as pushing in corners while still having it pack on large successive hits.

The stack before the stock crossover is alright but the high-speed portion of the stack needs lightened with lighter springs.

Ahhh. Thanks for the explanation. I wasn't seeing the bigger picture.... the clickers are only part of what controls rebound. Also, if it's appropriate in this forum, is there a place(s) you recommend that will do the right rebound adjustment for lighter springs? Also, if I went down one spring rate on the shock, would a similar rebound readjustment need to be done? Thanks.

Ahhh. Thanks for the explanation. I wasn't seeing the bigger picture.... the clickers are only part of what controls rebound. Also, if it's appropriate in this forum, is there a place(s) you recommend that will do the right rebound adjustment for lighter springs? Also, if I went down one spring rate on the shock, would a similar rebound readjustment need to be done? Thanks.

Rear shock rebound damping is actually too light on almost every Yamaha including this one for the stock spring. You should be good to go with just installing a new lighter shock spring.

Why not just try 10cc less oil in the outer chamber?

 

That's a pretty good idea, really.  For the time during break in, at least.  Dump the current oil in the outer chambers and refill with 335-340 instead of the 350 that it calls for (double check that in your manual).  If you don't like it, it's easy to undo. 

 

JS is right about the shock, too.  The stock rebound stack is just weak, top to bottom.   Can't be fixed with clickers because that messes with the bleed on both main stacks, and they don't do enough, anyway.

Why not just try 10cc less oil in the outer chamber? I too think the '15 is a little stiff compared to my 2011 and 2012 models. I weigh 175, but only have 12 hours on the bike. I have yet to bottom the forks, and have ridden some tracks and riding areas where they should have been to the stops. Just drained the oil over the weekend and will try it this Saturday. I hope to gain a little more compliance, and if harsh bottoming will fix with the comp clickers. I have a feeling this should do the trick.

Crusty, did you get a chance to try the fork with less oil? The 2015 manual calls out for 315 standard, with a range of 300-365. Thanks

Sorry - haven't tried it yet. May have to wait 2 weeks - too busy right now. You know how it goes. I'll post when I have a chance to evaluate.

Please do. Thanks

I got them installed and rode yesterday. Mind you this was my first out door ride of the year, and I was running on 0 sleep. The track was a full sand track and a hard pack supercross style track. The bike did improve, but the front is still not there yet in the sand. I played with the clickers a bit and was able to get it to stick alittle better but still had to fight it. The rear was amazing. Had sooo much traction on the straights and handled the bumps amazingly. In the corners the rear stepped out more which I was fine with. Also I was running 325cc of oil in the forks. 

Edited by jc6711

I got them installed and rode yesterday. Mind you this was my first out door ride of the year, and I was running on 0 sleep. The track was a full sand track and a hard pack supercross style track. The bike did improve, but the front is still not there yet in the sand. I played with the clickers a bit and was able to get it to stick alittle better but still had to fight it. The rear was amazing. Had sooo much traction on the straights and handled the bumps amazingly. In the corners the rear stepped out more which I was fine with. Also I was running 325cc of oil in the forks. 

Thanks for the update. Let me know what you discover as you "tweak" on 'em. I rode yesterday and for the first hour while I was fresh I liked the stiffer setup, but after about 2 hours I wanted off the bike. I really like how the bike has such neutral steering and minimal brake diving, but the chop eventually beats me up. Still don't have enough break-in hours, but I'm thinking I'll get the softer shock spring and then see which way to go on the forks once they settle in some more. If you decide to get ride of the 450 stock 4.9nm (.50kg) springs, I might be interested.

Thought I would update what I had done with the suspension and why it seems to partially go against the common wisdom. I had FC do the forks and shock. Based on the same information in my original post, they wanted to go down to a 5.5kg shock spring, yet leave the .51kg fork springs. They also did a revalve on both ends. I really questioned this because it seemed like the fork springs should be softer too, but they said they had been having a lot of success on the 2015, with this setup and similar weight/skill riders. I used the recommended sag/fork height and clicker sttings... finally settling on just minor changes to clickers. Bottom line, I am completely happy with how the bike performs. It now eats up the chop with ease but also offers outstanding bottoming resistance. I wish I knew exactly what they did to get the forks and shock to work so well. It definetly went against my notions that I needed a softer fork spring??? In the returned parts bag there were two fork spring guide spacers, shock compression spring, shock compression piston plate, and some nuts. Maybe that's a clue for you suspension gurus. By all acounts and spring calculators those springs are too stiff...

That is one approach; loosen way up on compression damping response and run a spring big enough to keep it from bottoming.  What you give up with that kind of setup is that the fork won't dive enough going into turns, and that aggravates understeer, pushing the front end.  That probably isn't as big a deal as it would be to an '08, but I'd be interested in what you think of how it turns now.

That is one approach; loosen way up on compression damping response and run a spring big enough to keep it from bottoming.  What you give up with that kind of setup is that the fork won't dive enough going into turns, and that aggravates understeer, pushing the front end.  That probably isn't as big a deal as it would be to an '08, but I'd be interested in what you think of how it turns now.

Hello Gray,

I had the track mostly to myself today and I was going to intentionally think about the bike understeering. Coincidentally, a guy had a video drone and gave me footage from above of me going around some turns and hitting some jumps. I definitely ride forward on the bike... seems like the whole seat is behind me! Also, I'm using the 5mm fork height recommended by FC. I think I learned to ride this way on the YZ  so it would turn. I like the way the bike feels when the rear end drifts out in turns, but it seemed a bit excessive from the camera view. Better have a look at the rear sag settings I think. So at this point, I don't think the bike is anymore prone to understeer than before the fork work. I also discovered that on jumps I tend to "absorb" the bike with my legs then start to stand up at the apex to absorb the landing. No wonder I often come up a bit short. But boy does the suspension handle that situation well. It's amazing what some video can reveal about your riding technique and bike set up!

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