Front end dips A LOT under moderate braking

[VA Sean]

I was riding a bit in downtown DC today and noticed that even in moderate braking situations my front end really dives (compresses) a lot.

A bit more so than it used to - 2004 Coppa that has about 5,000 miles.

Is this normal because it is finally "broken in" now? Is there an oil issue (in the forks) that I should be concerned with? Or should I just be adjusting something to stiffen them up?

[Guest ratchethack]

I was riding a bit in downtown DC today and noticed that even in moderate braking situations my front end really dives (compresses) a lot.

A bit more so than it used to - 2004 Coppa that has about 5,000 miles.

Is this normal because it is finally "broken in" now? Is there an oil issue (in the forks) that I should be concerned with? Or should I just be adjusting something to stiffen them up?

Sean, I've mucked around with the Marz forks a bit and posted a fair amount on it.

 

Of course it's controversial, no one likes to take a stand on guidelines, and there's considerably more misunderstanding, superstition, and Old Wive's Tales on this than clear thinking. . .

 

The GENERAL guidelines I like that no one wants to commit to (for most average weight riders over most kinds of road conditions) are:

 

Laden sag should be 30-35% of total available fork travel.

 

Unladen sag should be 15-20% of total available fork travel.

 

I happen to prefer "tighter" sags than this -- but that's just me. Racing types go quite a bit tighter yet.

 

NOTE: THE KEY to setting sags is having BOTH laden and unladen sags IN YOUR TARGET RANGE -- getting just one right counts for nothing a-tall!!

 

If your sag settings are very far out of this range, it'd be an indicator that your spring rates aren't properly matched to your riding weight. Again, there are many threads on this. A simple spring rate upgrade is relatively inexpensive, and has always been a HUGE bang-f'er-the-buck improvement for many (myself included).

 

If your sags are out o' whack (easily determined with the usual zip-tie around the lower fork tube to determine extent of fork travel when laden & unladen), and the spacers are the proper length (again, see threads on the subject), this would be an indicator that you're riding around on the air spring. By my experience, far too many Guzzi riders (and riders of other marques) are doing this and have no clue. It means that they're getting the benefit of only an inch or so of fork travel out of an available 120 mm total fork travel, along with the usual fork dive symptoms to boot.

 

Here's a few Web sites that I've posted before that I find cover the basics accurately and in terms that most can follow without too much trouble:

 

http://www.strappe.com/suspension.html

 

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

 

http://www.peterverdonedesigns.com/oilheight.htm

 

Hope this helps.

[dlaing]

Laden sag should be 30-35% of total available fork travel.

 

Unladen sag should be 15-20% of total available fork travel.

 

I happen to prefer slightly "tighter" sags than this -- but that's just me.

FWIW, Ohlins recommends

Without rider:

Front: 25-30 mm

With rider:

Front: 35-50 mm

If I dare speculate....

I am inclined to think unladen sag of about 20% (24mm) regardless of riding style,

and laden sag of about 25%(30mm) would be near ideal for sport

and laden sag of 30%(36mm) would be ideal for touring.

Sport/Touring might be about 33mm.

YMMV

My Ohlins were last measured at 26mm unladen and 36mm laden.

I find this to be too soft, especially after getting 550#/inch spring for the rear, so I plan on getting firmer springs.

 

 

I was riding a bit in downtown DC today and noticed that even in moderate braking situations my front end really dives (compresses) a lot.

A bit more so than it used to - 2004 Coppa that has about 5,000 miles.

Is this normal because it is finally "broken in" now? Is there an oil issue (in the forks) that I should be concerned with? Or should I just be adjusting something to stiffen them up?

Start with sag.

You certainly can adjust something.

It is a little worrisome that it just started having a dive problem.

But maybe you are just getting familiar with the brakes, etc.

Or someone messed with your daming settings.

Once you know the sag, you may get by with adding preload and or damping.

FWIW my preload is already maxxxed out.

[Dan M]

 

What they said Sean. Start with getting the sag set. V11s are under-sprung for us fat Americans. A click or two of compression damping will help too but don't go so far as to ruin the ride quality and the ability to absorb bumps when cornering.

[VA Sean]

Thanks, Gents.

Basic stats on me are 5'8" and 162 lbs... so not too much the "typical" American today, though a year ago I was closer to 190 lbs.

Based on "feel" alone, I am guessing the dive is way outside the parameters y'all have set... 35-50mm with rider? I'd want to think mine is more like 65-80mm - a REALLY NOTICEABLE dive.

 

Ratchethack - thanks for the links, haven't checked them out yet, but will shortly.

 

I'll try the zip ties and measuring to confirm actual distance of the dip.

 

For "unladen" and I to grab the bike from the front and push down on the bars to see how far it dips or is there some other way this is done.

I can probably figure out how to do it with the laden weight

[Guest ratchethack]

For "unladen" and I to grab the bike from the front and push down on the bars to see how far it dips or is there some other way this is done.

I can probably figure out how to do it with the laden weight

Sean, at the first link above, see Front Suspension: sag.

 

Do NOT push down on the bars to determine unladen sag. You want to measure the "resting point" -- where the bike settles on its springs without any weight on it.

 

NOTE: If you allow the bike to "rise" to this position from a compressed fork, the "resting point" will be perhaps a few mm (I get 1mm) lower than if you allow the bike to "settle down" to this position. The difference between the "rise to" and "settle down to" position is a measure of the fork stiction. This will vary slightly according to the viscosity and grade of fork fluid you're using, how old it is, the condition of the seals, etc. To get an accurate read on unladen as well as laden sag, take both "rise to" and "settle down to" points and average the two.

 

Have fun. If it seems to be getting a little counter-intuitive, just relax and refer to the links again. Once you get the concepts nailed down, it'll all make sense. Should be a great learning experience for you and allow you to achieve great imrovements in handling and ride as a result.

 

NOTE: Just my observation over the years, but I'd estimate that fewer than 10% of all riders ever perform this excercise or any part of it correctly, nor do they have the faintest clue about how their suspension is set up. I've always considered it mandatory (or, before I had all the knowledge available today, at least primitive laden sag setup), but then that's just me. Getting sags and preloads alone set up properly can (and often does) transform a wallowing sow into a machine that for the first time handles close to the way the engineers intended.

[badmotogoozer]

If you've noticed a sudden change you may have blown a seal and are getting an air leak. Any fluid leaks? At 162 you shouldn't be getting that much dive on stock springs. Especially the Ohlins. Make up a solution of a bit of dish detergent and water. Dribble a bit at each sealing point, compress forks a few times and look for bubbles.

 

I've never played with the Ohlins so can't offer much direct support... Ohlins forks are notorious for needing new seals @5000mi.

 

Rj

[dlaing]

Based on "feel" alone, I am guessing the dive is way outside the parameters y'all have set... 35-50mm with rider? I'd want to think mine is more like 65-80mm - a REALLY NOTICEABLE dive.

35-50mm does not refer to dive, but to the difference between fork fully extended when bike is lifted, and where its at with bike and rider weight added.

The greater that number, the more prone to a dive problem.

 

I think what badmotorgeezer said makes sense, but I wonder why no oil is leaking out?

Are Up-Side-Down forks designed to not leak as much when the seals blow?

[VA Sean]

I think what badmotorgeezer said makes sense, but I wonder why no oil is leaking out?

Are Up-Side-Down forks designed to not leak as much when the seals blow?

 

Nope-

no oil leaking - at least not enough to see under the bike, or on the legs themselves.

 

Crap - well if these things are truly busting at 5,000 for most folks, then that is probably what the deal is for me, cause I am right there.

 

It might not be "sudden" - just that I began to really notice it when I was riding yesterday -- DC has a LOT of stop & go - stoplights, and just idiots (Read: tourists) who stop for absof_ckinglutely no reason whatsoever, other than to admire statutes, monuments, museums, etc)...

Anyway, it was in the middle of that kind of situation when I thought to myself... "geez this thing seems to dive quite a bit... can't say as I remember it doing that much before today."

In all fairness, I don't do much city driving (almost never in DC), so maybe it is just more noticeable when you have a lot of stop/go traffic.

 

I'll try the detergent trick when I get home and report on what I find.

 

Thanks again, guys.

[moscowphil]

Have you got the manual for the OHLins fork? (if not you can download one from the Ohlins web site). The manual gives quite a lot of info about how to set up the forks, and it is clear that one of the critical factors is the oil level in the forks. This is because the air space above the oil acts as an air spring - and the higher the oil level the more progressive the air spring becomes. So raising the oil level will tend to reduce the amount of dive under braking. If the bike's a few years old and hasn't had a fork oil change it probably needs one. When you do this, make a note of the existing oil level before you empty the forks, and maybe raise the oil level a bit (say 10mm higher) when you refill. If the bike has already had a fork oil change, it may be that it wasn't refilled to the correct level. I'd also try increasing the cmpression damping. These are the adjusters at the bottom of the forks - screw them in (clockwise) a couple of clicks.

[Guzzirider]

My Ohlins were like that from new- just a couple of clicks of extra compression on the front sorted it nicely.

 

Careful when playing with the Ohlins settings- just one click makes a lot of difference on the both the front and rear adjusters.

 

Guy

[docc]

Are the Ohlins springs fitted to the Guzzi somewhat stiffer than the Marz springs ? Speculation has been that the Marz springs are 0.6-0.7.

 

Will the Ohlins springs fit the Marz forks? (Sorry about the aside . . . looking to upgrade.)

[Alex-Corsa]

I was riding a bit in downtown DC today and noticed that even in moderate braking situations my front end really dives (compresses) a lot.

A bit more so than it used to - 2004 Coppa that has about 5,000 miles.

Is this normal because it is finally "broken in" now? Is there an oil issue (in the forks) that I should be concerned with? Or should I just be adjusting something to stiffen them up?

 

 

All I know and that's for sure better , fork oil has to be replaced every year regardless the milleage, or after 10k miles maximum if that's made within les than a year.

[Guest Mattress]

Nope-

no oil leaking - at least not enough to see under the bike, or on the legs themselves.

 

Crap - well if these things are truly busting at 5,000 for most folks, then that is probably what the deal is for me, cause I am right there.

 

It might not be "sudden" - just that I began to really notice it when I was riding yesterday -- DC has a LOT of stop & go - stoplights, and just idiots (Read: tourists) who stop for absof_ckinglutely no reason whatsoever, other than to admire statutes, monuments, museums, etc)...

Anyway, it was in the middle of that kind of situation when I thought to myself... "geez this thing seems to dive quite a bit... can't say as I remember it doing that much before today."

In all fairness, I don't do much city driving (almost never in DC), so maybe it is just more noticeable when you have a lot of stop/go traffic.

 

I'll try the detergent trick when I get home and report on what I find.

 

Thanks again, guys.

 

Maybe you are just noticing it more now cause you ain't so fat as last year? With the extra poundage maybe the forks were already compressed from your cheeseburger diet?

 

I'm 5'8" also, and if I weighed 160lbs the U.N. would be sending in hunger relief supplies. Seriously though, there are different body types so weight/height proportion is variable. I'd be happy to be 185.

[dlaing]

Are the Ohlins springs fitted to the Guzzi somewhat stiffer than the Marz springs ? Speculation has been that the Marz springs are 0.6-0.7.

 

Will the Ohlins springs fit the Marz forks? (Sorry about the aside . . . looking to upgrade.)

The Ohlins on the Cafe Sport and Corsas are much firmer than the Marzocchi that came with my bike.

The Scuras might be a little softer.

I highly doubt the Ohlins springs will fit the Marz.