Matching suspension front and rear

[anthony]

Like many budget bikes, the FZ6 comes with really basic bare-bones suspension on both ends. No adjustability, except preload on the rear, and sprung pretty soft.

So, I upgraded the forks with new springs, oil, and cartridge emulators from Race Tech. Now I'm faced with a dilemma. The stock rear shock has noticeably less damping (rebound and compression) than the recommended setup I used for the front. I love the way the front feels, but I can also tell that front and rear aren't matched up. It's nothing scary or dangerous, but I get some front-back oscillations on some types of bumps. Also, when I push straight down on the bike, the back moves down (and then back up) quicker than the front.

So, the question is this... Do I keep the front end at the recommended settings, or do I put in some lighter fork oil to back off the damping until it matches the rear? I know I'd be losing some of the benefits of my upgrade if I change the fork oil, but I'd hopefully be getting some harmony between the front and back.

Oh, and I can't afford a rear shock just yet, but that would obviously be the ideal solution.

Thoughts?

[jixaw]

How thick did you go with the oil?....what is the stock wt?.....with the cartridge emulators you shouldnt really have to go thicker....

I had a more extreme experience...dunno if you read about it...but I experienced a lil' slapper/wobble that scared me....dunno if yours is that bad, but I'd drop down the weight a lil'...have you had a chance to measure the sag in the front and in the rear at all?

I heard that some of the track guys have been using some synthetic ATF in there....its about an 11 wt. ...maybe someone will chime in about that...

[sanglant]

Like many budget bikes, the FZ6 comes with really basic bare-bones suspension on both ends. No adjustability, except preload on the rear, and sprung pretty soft.

So, I upgraded the forks with new springs, oil, and cartridge emulators from Race Tech. Now I'm faced with a dilemma. The stock rear shock has noticeably less damping (rebound and compression) than the recommended setup I used for the front. I love the way the front feels, but I can also tell that front and rear aren't matched up. It's nothing scary or dangerous, but I get some front-back oscillations on some types of bumps. Also, when I push straight down on the bike, the back moves down (and then back up) quicker than the front.

So, the question is this... Do I keep the front end at the recommended settings, or do I put in some lighter fork oil to back off the damping until it matches the rear? I know I'd be losing some of the benefits of my upgrade if I change the fork oil, but I'd hopefully be getting some harmony between the front and back.

Oh, and I can't afford a rear shock just yet, but that would obviously be the ideal solution.

Thoughts?

Back off the preload of the rear shock, if you can tolerate it, and save for a good used shock. Mismatched suspension is no fun, but screwing up the front won't help with the back. Just ride to the limits of the rear suspension and don't let the front seduce you into going faster.

[anthony]

Jixaw: Stock weight is 5W, and race tech recommended 15W with their setup. I set up rear sag a while ago, but I think it's around 35mm. Front sag is about 35mm with me and gear on the bike. Those seem to be commonly recommended for street riding. My handling isn't awful by any means, just a little peculiar.

Sanglant: Why back off the preload on the rear?

(saving for a rear shock)

[sanglant]

Jixaw: Stock weight is 5W, and race tech recommended 15W with their setup. I set up rear sag a while ago, but I think it's around 35mm. Front sag is about 35mm with me and gear on the bike. Those seem to be commonly recommended for street riding. My handling isn't awful by any means, just a little peculiar.

Sanglant: Why back off the preload on the rear?

(saving for a rear shock)

Preload effects the stiffness of the rear suspension, which you're saying is rising too fast. Ideally, preload should only be used to set the sag, and for the rear, you're looking for about 25% of total travel (common numbers don't mean much, unless its from someone specifically referencing your bike where that number is in fact that percentage). But, if you can tolerate having more sag, then you can cheat by reducing the rebound effect of the shock (the rising up fast).

What I bet the bike feels like is that it is "hinged" in the middle, with the front wanting to turn and the back wanting to stand up and go straight.

[MarcS]

Preload does not increase spring stiffness/spring rates. It only affects ride height.

http://www.sportrider.com/tech/146_9510_tech/

Pony up for the Ohlins.

[sanglant]

Preload does not increase spring stiffness/spring rates. It only affects ride height.

http://www.sportrider.com/tech/146_9510_tech/

Pony up for the Ohlins.

I didn't say it increased spring stiffness, but preload will effect the *rear suspension* stiffness. They are two different things. The spring rate, or spring stiffness, is dependant on the spring itself and is not realistically changable (stretch it, heat it, cut it, etc.).

However, the spring's stored energy at a given compression will change with preload. Ex, a spring rated at 1kg/mm compressed to a starting point of 10 mm will have 10 kg of stored "force" (not entirely accurate, but for this it will suffice as a unit), while the same spring compressed to a starting point of 5 mm with have 5 kg of stored force. Preload is independant of suspension stroke, so both springs can be thought to effectively start at point zero for this example (sag ignored, in other words). Deflect the suspension by 10 mm over a bump, and you will see that the first spring now has a stored energy of 20 kg, while the second has an energy of 15 kg. The first spring will push up the rear suspension to the starting point of zero faster than the second spring, making the suspension seem stiffer.

If you want to experiment, tighten your preload as far as it will go and ride, then loosen it completely and ride again. The rate didn't change, but the ride certainly will.

Preload shouldn't be used to do this, as I stated earlier, but in a pinch it can help crutch a bad situation.

[MikeInSLC]

Pony up for the Ohlins.

Indeed! Like buying a brand new bike!

[anthony]

I've got me eye on an Ohlins, though Wilbers makes a nice shock for the FZ6, too. It's gonna be a while, so there is a lot of time to shop.

I'll play with the preload and see what happens (since it's easy).

Thanks all!

[sanglant]

I've got me eye on an Ohlins, though Wilbers makes a nice shock for the FZ6, too. It's gonna be a while, so there is a lot of time to shop.

I'll play with the preload and see what happens (since it's easy).

Thanks all!

Fox, WP, and even Penske make good shocks that aren't too costly, especially if you can find a used one. You can also have yours revalved by Traxxion, Thermosman (my pick), Lindeman, RPS, or other places. Check them out.