rear spring rate - too stiff?

[shwaz]

does this sound right:


i picked up a set of ikons on clearance from z1. i'm on a 79 850, so it's a heavy bike. i weigh close to 200lbs.

the fellas there recommended the highest spring rate, 123-217. i'm just wondering if anyone with more experience would have gone with this high, or stepped it down. ikon's next highest is 100-185.

it rides ok but does feel pretty stiff. there's a lot of physics involved that i dont understand, but i know the 850 is a beast, and i'm not a super lightweight rider. i just wonder, since these are the highest rated i saw, isn't it the same thing someone who weighs 350 would buy, and if so isn't that odd for me to be using them?

anyway, not gonna rush out to buy a lighter set, but curious to hear what opinions people have.

[razor02097]

Yikes... That is a very very heavy spring...

Since you have a twin shock motorcycle those spring rate numbers effectively double! When you sit on the seat I bet it barely compresses the rear suspension... A 200 lb rider isn't a heavy rider...and unless you are riding 2 up with a heavy passenger and have luggage or you want a ride that can break your back... The spring rate is much too high...

Better to select a lighter spring that you can adjust preload to suit your need.

[shwaz]

yeah, i suspected that. i'm a little frustrated as the purchase was on their advice. called back the other day to discuss and that person gave the same advice - says he would have recommended the same spring. it just seems too much. said he'd be glad to swap it out if they had any more, but they don't - it was on closeout.

anyway i'm waiting for someone to swoop in here and say that they would have got the same spring and explain why, but having a hard time imagining it. i can't imagine ever jacking up the preload on these things. there's a rebound adjuster as well, but the last thing i want is to make them bounce back any faster than they already do.

[Tim Tom]

Well one of the good things about the shock is they are rebuild-able. You could always get a new spring, and rebuild the shock with that spring. Kinda sucks but it may be worth it to improve the ride quality.

Of course now I'm very curious about how mine will feel when I can finally give them a proper test.

[salty_monk]

On the progressive the 95-140 was fine for me at 165lb with 1 step of preload.

Have you taken a sag measurement? I think the 850 should have 4" of rear travel with those shocks so you want about an inch (20-25%) of sag with you sitting on the bike in full riding gear. Better than guessing...

Bunch of resources on the web for this. Bit difficult on your own but you can get a reasonable idea by yourself...

http://www.racetech.com/articles/suspensionandsprings.htm

http://www.sportrider.com/tech/146_0308_set_your_static_sag/index.html

http://www.protechsuspension.com/race_sag.php

http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=How+to+measure+static+sag

http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=How+to+measure+static+sag#sclient=psy-ab&hl=en&source=hp&q=How+to+measure+motorcycle+suspension+sag&pbx=1&oq=How+to+measure+motorcycle+suspension+sag&aq=f&aqi=&aql=&gs_sm=e&gs_upl=10006l13811l0l14152l22l22l0l0l0l0l191l2139l17.5l22l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=56c688f775f9feb&biw=1920&bih=993

[Steve]

... anyway i'm waiting for someone to swoop in here and say that they would have got the same spring and explain why, but having a hard time imagining it. ...

OK. I haven ot done a whole lot of research yet on spring rates, but I might have gotten them for my bike.

I weigh just a bit more than you, and my bike is heavier, too.

What's heaver than an 850G?

Click the link in my sig and see my 850GK.

.

[shwaz]

meh.

does this have safety implications? like hitting a bump at speed and instead of the suspension soaking up the impact and keeping the rear wheel in contact with the ground, actually pogoing and lifting the rear?

in a totally unrelated topic, my petcock is failing and i'm grumpy because i kep pouring money in :/

[razor02097]

Safety implications? Not likely unless you consider damage to your back part of safety. You aren't going to take jumps with it. A pot hole or bump in the road big enough to make you lose control isn't going to be because of the rear suspension. Your ride will be uncomfortable but not dangerous. Not if it was the forks too stiff.... that might be a different story.


I would see if anyone would be interested in them then put that money toward some more comfortable springs.