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MotoMacGyver
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Discussion Starter #1
Ok, I'm a little confused here. Mainly about preload, both front and rear.

I know WHAT preload is. My question revolves around whether or not increasing preload raises the ride height or not. Let's just focus on the rear for now: If I INCREASE preload (i.e. turn the shock adjuster clockwise (looking down from the top)), will it increase ride height? I've tried to measure, but it seems the same. On a car (race car anyway), when you turn a jackscrew, coilover shock (or equivalent) on each corner, it increases ride height. I'm told this is not so on bikes. Why? Also, do ZR-7's have progressive-rate springs? I'm guessing so. If you turn up the preload, it is supposed "squish" the soft part of the spring so the firmer part works sooner. Correct? Well, if this is so, I just can't see how you can turn that adjuster and NOT increase ride height.

Now for the front: Same dilemna/confusion. If you do the PVC upgrade, aren't you pushing the front end up by the same distance as the length of PVC?

Basically, either front or rear, how can you turn an adjuster or add a PVC pipe and ONLY take away the "squish" and not increase ride height?

Emrah
 

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I didn't measured it, but by having it set to the 5th position (spring compressed most), I feel the bike sits lower when I sit on the seat.
 

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>If I INCREASE preload (i.e. turn the shock adjuster clockwise
>(looking down from the top)), will it increase ride height?
increasing the preload will definitely increase the ride height. it may be less noticeable in the rear since the total increase in distance is small. this applies whether you have straight rate or progressive springs. you are increasing the initial force the springs press back with so that raise the load, in this case the chassis of the bike.

>do ZR-7's have progressive-rate springs?
the zr does NOT have progressive rate springs, they are straight rate both front and back.

>Now for the front: Same dilemna/confusion.
same thing applies to the front. i'm guessing ap746 feels the bike is reding lower when they increas rear preload because it effectively tips the bike forward by raising the rear.

for the rear you can't reduce squish without changing the ride height. for teh front you could increas pre-load and then slip the fork tubes up in the tripple trees. BE CAREFUL! you're now starting to monkey with the steering geometry and can make the handling radically different.

>Basically, either front or rear, how can you turn an adjuster or
>add a PVC pipe and ONLY take away the "squish" and not
>increase ride height?
basically, you can't :( in order to reduce squish and not change ride height you would need to get stiffer springs that are stock height. this applies to front and rear.

i suggest you contact hyperpro for their progressive springs. they offer front and rear and from what i understand they ask your weight and tailor the springs for you and your riding. it may take a while to get them since they're not readily available in the states and you need to special order them from europe.

scott :)
 

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MotoMacGyver
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2,545 Posts
Discussion Starter #4
Thanks. That's what I thought, but I'd heard otherwise. Glad I'm not nuts.

Actually, I'm pretty happy with the ride and stuff. I know people claim miracles when they do the upgrades, but for me, stock is fine in the front, and the adjustability in the rear is fine as well.

Oh, who am I kidding? I haven't had one vehicle that I haven't modified! It will be a while though.

Emrah
 

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i don't know if you're not crazy but at least you understand a little about suspension ;)

i know what you mean, i just can't stop messing with my bike either :) i found the front fork limiting a few months after i got the bike. the pvc trick is cheap and easy, just like me :) it's also easily reversible if you don't like it. it really does make a world of difference. i'd recommend yout try a half inch just to see what it's like.

enjoy!

scott
 

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MotoMacGyver
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Discussion Starter #6
FINALLY figured this preload thing out

Ok, after quite a while of confusing myself about preload and its affect on ride height, I finally figured it out today. I can't believe it didn't dawn on me earlier.

Yes, increasing preload (turning the adjuster clockwise looking down on the bike) WOULD in theory increase ride height, but I/we overlooked one thing: the actual shock itselft. Not the "shock" (i.e. spring and damper combo), but the actual piston travel in the shock itself. When the bike is sitting at static height (no rider on it), the spring is pushing the rear up as far as it can go; usually FULLY EXTENDING the shock. So, the spring may be trying to push up on the rear, but it is limited by the shock travel. In essence, the shock is "topped out" to full extension.

So, once you reach this point, you can crank away all you want; the spring will now compress (hence the name "preload"), but will not push the bike up any farther because it is limited by the shock travel.

Exact same goes for the front. The forks can only extend and push the front up so much.

All this finally clicked when I had the nose cone off of the race car today and was staring at the coilover shocks for the front suspension (essentially same concept as the rear shock on a bike).

Whew! Everything is alright with the world. Well, ok, maybe just my distorted world!

Emrah
 

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emrah, you're correct BUT ride height with no rider on it doesn't matter much when you're riding. what's inportant is how the machine sits with rider(s) and luggage. this is why you may adjust preload for different rider weights.

also, the zr-7 and a race car may sit topped out unloaded but something like a dune buggy or off road bike might not. vehicles like these have longer travel and leave some of it so that wheels can extend down into approaching ditches as well as come up when hitting bumps.

scott
 

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When you ride, and the springs are partially compressed, you're suspension works the same as you described for the off road buggies. They just catch more air than you, that's why it looks like alot more. But with so little travel to start with, you don't have much to cushion the pot-holes that are out there just waiting to inflict pain.
 

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MotoMacGyver
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Discussion Starter #9
Oh, absolutely, I agree. That's why I referred to static ride height, and not (I believe the term is called) "Sag" with a rider. I was trying to clarify (for me as well as for a couple of others) about how twisting the preload collar affects static height.

And, yes, most cars and off road vehicles must have much more articulation, both upwards and downwards. I guess their "static" height would be equivalent to our "with rider" height.

Oh, by the way, I tried the PVC thing today, and it was HORRIBLE! I only did a 3/4" spacer, and took it out for a spin and bottomed out on everything. I don't think I it was bound up or anything, because at a stop, I'd compress the forks by rocking of them, and they were fine. Yes, I could feel a little less travel, but they seemed fine. Then, when I hit bumps or ripples in the road, I'd feel a definite "clunk".

Put the PVC in at lunch, and took them out promptly right after work. I dunno. I'm pretty happy with stock. Progessive Springs are only $75 bucks, so I might try those in the future.

Emrah
 

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wow! i'm surprised at what you describe since i have the same bike with the same setup and i much prefer it to stock. i regularly bottomed out with stock but haven't done so since i added the pvc.

like you i'm hoping to get progressive and some other goodies soon too. just as soon as i pay my dental bills :(

scott
 

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Wheelie for Safety
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All this talk about spring preload got me thinking about setting my rear shock rebound damping. I have already set the spring preload to the 5th position (I weight 175 LBS), but I have never touched the rebound force adjuster. I adjusted it from the default #2 position to #4 for maximum rebound force.

What a difference it makes! It handles the bumps much better now.

Andy
 
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