wr450 setup / geometry
Posted June 18, 2012 - 06:00 PM
I have a question about the setup and geometry of the bike. A while ago, I was riding the bike but it was too stiff. So I had the suspension redone by ESP. It works pretty good I guess. I ran mx71 tire on the front and D739 on the rear. I was able to live with it.
Last time around, I changed a tire and went from a 120 to a 110 in the rear. It lays over in the turns much better. However, the front end pushes quite a bit. It also seems like there was not a lot of front end traction. It was really wierd.
So I just put a mx71 120 tire back on it and it sits almost 2 inches higher now. I bet that's what throwing me off. That's why I couldn't feel any weight on the front tire with the smaller rear.
I don't want to just go adjusting the rear spring to fix the height of the rear.
How do I measure it to make the bike balanced regardless of the tire I have on the rear.
Am I making sense?
Posted June 19, 2012 - 08:53 AM
Maybe adding a link or two to the chain? That should lengthen the bike putting more weight on front.
Posted June 19, 2012 - 07:02 PM
Posted June 19, 2012 - 07:39 PM
What I would do is start all over. Check your sag correctly, need 3 people to get it right. Full gear, standing up in the riding position, tape parallel to the shoch angle etc...I find the best time is right after the 1st loop. Shock is warm, your buddy's are there to help. I usually go to 105mm first, then adjust from there. Then I would set the fork height, all clickers, Hispd, to manual specs. Then ride it on a 3- 5 mile test loop in your terrain type adjusting it till you make it as good as it will get. Which means getting it to optimum, then making it worse to verify it. Notepad is helpful. I try to ride a race pace on the loops. I did that a lot while I was racing, and it really gives you an edge having your bike handle close to it's limit. Max out the performance in the suspension. Your faster, in more control, and much much safer from injury.
Just get the M12' and roll with it. Every tire has compromise, impossible to make a tire do everything. I use the same 3 tires. I know what they do good and what they do bad, so I'm anticipating it's behavior before it happens. I'm comfortable with them and see no reason to stray until they stop making them. Keeps things consistent with the set up. I've never tried the 71, but I've been told it sucks by several people.. I tend to stick with the Maxxis SI for most stuff, use S12, for sandy races or mudders, and Pirelli MT 16 for Dual Sporting. In fact I'm staring at my 09 with the brand new MT 16's I just put on tonight. Leaving for Colorado TAT ride next Wed.
Edited by Bandit9, June 19, 2012 - 07:42 PM.
Posted June 20, 2012 - 04:34 AM
I also need to dial in my suspension, but it's hard to find 2 buddies who're sober at the same time!
Posted June 20, 2012 - 02:31 PM
Posted June 20, 2012 - 05:02 PM
Posted June 20, 2012 - 05:20 PM
Posted June 20, 2012 - 06:21 PM
to set the record straight... my bike handled pretty good with the 120 size tire. Then I went to a different brand 110 sized tire, which was two inches shorter. That's when I noticed a bit of a push in turns and less front end bite. I have now went back to a 120 size tire. My sag is set correctly and my forks were raised slightly in the clamps to give me a front end feel I could live with.
My question is... If I change from a taller to a shorter rear tire (or vice versa), is there a way I can balance the bike front to rear by measuring the height of the bike at various points? Is there a certain difference that I should be able to measure on the front and rear of the bike? It may have a chopper or a stink bug stance, but how can I meaure that? The size of the rear tire should have little effect on the sag, right?
Doesn't yamaha have some sort of measurement or spec where I can check the relationship between the height of the front and rear of the bike. In theory, this measurement should apply regardless of the tires I have on the bike, right?
Posted June 20, 2012 - 06:40 PM
Posted June 20, 2012 - 07:23 PM
Yes, your right. The size of the rear tire will have no effect on sag. But it will have an effect on front end traction. I guess you could measure from a concrete floor all the way up to a seat bolt and get that height, and then do the same for the front end by measuring between the front axle and triple tree bolts. These two measurements will then give you the "aspect" that handles well for your riding style. Then whatever size tire (larger/smaller) you throw on there next, you can adjust to your "aspect" ratio, and the bike will handle the same as before. As long as the tires are the same construction/tread pattern that is!!!
Now you get it. But... what is the baseline for a stock bike off the showroom floor?
Posted June 20, 2012 - 07:41 PM
Posted June 21, 2012 - 07:56 AM
Ummmmm..... you don't want to know! I used to work in a Motorcycle dealership. And those monkeys just throw them together! Measurements all over the place! What's way more important, is the baseline that works for you! You said you had it working well until you switched tires, so why not switch them back and get a baseline measurement that works for you?
Good point. I'll just establish my own baseline for front-to-rear height. I'll probably do it based on the frame in the front and swing arm in the rear. I could always just measure it each time I change to a different tire.
In the summer, when I am dual sporting, I like a 120 size tire for the fire roads and rocky jeep trails..
In the winter months, when I am riding in the desert, I actually like the 110 size tire because it lays over so much better and I can slide the rear more easily when turning. (not that I'm moving the rear around all that much, but its important that it break loose from time to time)
My bike is always just a little "off" when I change tire sizes.
Edited by mauricedorris, June 21, 2012 - 07:57 AM.