Rear suspension travel

[Burns310r]

Okay well i have a buddy that races with me in the Open A class at our local MX track. He is on a PEP ZPS 09 YFZ 450.

I noticed that when he lifted up on the rear of his quad, he had an additional 4-5 maybe more inches of travel. So in other words, that swing arm will drop along ways when he goes in the air giving him a much cushier landing on the big jumps.


I did the same to my 86' -1 Lonestar swing arm with stock linkage and Custom Axis shock. My rear end only goes up 2 inches from ride height. I assume we have the same trave in the compression direction though. Our ride heights are roughly the same. Mine is 7 inches to the frame with me on it.

Is there something wrong with my quad, or is that part of the problem with the stock linkage setup?

Would a CR500 rear setup really give me more travel? As much as a newer quad?

Is there such thing as a 86' style CR500 swing arm? I know i can find a shock and linkage on the net somewhere. But the swing arm could be tricky.


Thanks

Burns

[SilverLake250R]

A CR500 Link on a stock frame would be tricky. On the Walsh and Laeger frames, the shock mounting location is offset to the side on both the swingarm and the frame, and it is also higher up on the frame. I'm not saying it couldn't be done, but it would take some major frame modification, because I don't think you'll find any CR500 link swingarms that are set up in the center.

Here's a pic of my Walsh frame so you can see what I'm talking about-

http://a7.sphotos.ak.fbcdn.net/hphotos-ak-ash2/148574_587029156854_15305732_33765300_7060604_n.jp g

[Burns310r]

Well im going to be re powder coating my frame this winter, so it would be a prime time to make necessary mods to the shock mounts.


Im more curious if it will provide similar travel to the newer quads, or if there is something wrong with my quad.

Also about the 86 style mounting CR 500 swinger.

[DnB_racing]

the extra couple inches of sag on your buddies quad is from the ZPS,

[Burns310r]

Its not technically sag.

Our ride heights are about the same, his just has much much more travel when you pull up on the rear end.

[DnB_racing]

Originally posted by Burns310r
Its not technically sag.

Our ride heights are about the same, his just has much much more travel when you pull up on the rear end. your right its not actually sag,it more of the part of the zps that gives it the floating feel, but it is the zps spring that your seeing the difference. there probably isn't anything wrong with yours

Im not good at explaining it but its like the quad floats on the suspension if you know what i mean lol

[Burns310r]

I understand how the ZPS system works.


But the difference is that if i where to put a ZPS shock on the rear of my quad, the range of motion of my rear swing arm will not actually improve any.

It is either limited by the linkage setup or shock stroke. Probably both.

That is why im trying to figure our what it would take to get my rear end to have the length of travel of a newer quad.

[mx Eli]

in other words he has about 2-3 inchs more drop-in travel then you? I would maybe think you quad would not have the travel of your buddy's quad and thts where the extra travel; comes from? it would also depend on where the shock sits in its stroke while at normal ride height.

just my .02

[mx Eli]

most of the dirt bike linkages like you said (cr500, crf 450) are set off to the right like silverlake said. I would say converting to a no-link would be a good option. talk to pinitatv (jody) on here, he should be able to give you the right info

[D Bergstrom]

Originally posted by Burns310r
I assume we have the same trave in the compression direction though.

I wouldn't make this assumption, the only way to know how much up travel is to measure it, it can very greatly depending on tire size, shock setup, etc. Sure you buddies YFZ may have 4" more of droop, but he could also have 4" less of up travel. The location of the travel in regards to the chassis is the most important thing. I believe GT Thunder has a write up on their website on how to measure to see if your shock lengths are correct, might be worth reading and looking into your setup.

I know my stock 86 linkage/swingarm setup with an Elka shock had just over 9" of travel. I know I didn't have as much up travel as it should, but I also run 23" front/22" rear tires, didn't help things.

I have noticed the same thing on my 250R compared to my 450R's, my 250R just doesn't have much drop. I actually had a custom shock made for the rear of my 250R, I measured out the bottomed out frame height and extended frame height to get my extended and compressed lengths. Ended up with almost 11" of rear travel, but most of that came in the form of uptravel, the extended length of the shock I came up with was only about a 1/4" longer then the Elka I had. Problem with going any longer on the shock is I couldn't get the compressed length I needed, just not enough shock to do it.

I would for sure check out GT Thunders website, get some measurements off your setup and see what you are working with.

Doug

[dustin_j]

Kyle,

Check your pms; I'd love to help you out with this, and maybe we can get something figured out to help stock frame 250R guys.

Like Doug said, where your wheel travel is located in reference to frame travel is very important. If you don't have very much down travel (sag), you're giving up traction and plushness. It would be worth measuring extended and compressed lengths with your current setup to see what can be improved. Also worth measuring, would be the leverage ratio for the first and last inch of wheel travel. To do this, measure the shock length (shocks removed) with frame height at 1.5" 2.5" 11" and 12." What you'll find is the leverage ratio is roughly 60% higher at bottom out than top out; this is what makes Hondas buck, though I'm not sure if the 250Rs are as bad.

I'm confused as to why you guys don't think the yfz has more sag? Sag is measured as the amount of travel, from full extension, to ride height. If you two have the same ride height, but you can lift up his grab bar higher before the tires lift off, he has more sag. Not saying one setup is better than the other, just clarifying. To add to the confusion, I believe many ZPS setups use longer extended lengths to allow for more sag while using stiffer spring rates.