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Old 05-10-2013, 03:17 PM   #706
jmcg
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Quote:
Originally Posted by RuggedExposure View Post

You're going to need a metal rack mate.
Yeah, I figured as much when I saw the amount of flex in the plastic rack.

I'll make do for the commute for now and sort out something more robust for any off-road shenanigans..

Cheers,

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Old 05-10-2013, 04:29 PM   #707
rride
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Quote:
Originally Posted by Blakebird View Post
I've had a half dozen BMW's....airheads, oilheads, K-bike. I've never felt the need to change oil viscosity in any of them.

The only one that made a clacking sound was the '81 R100RS, and that had nothing to do with fork oil viscosity....it was fork internals, they clack on rebound not compression
How much do you weigh?
150 lbs riders probably don't need to.
200 lbs riders and over should.
If you get a NEW bike doing it from the start, the dealer
should do it for you.

Most offroad riders are smaller though,
except out West where the roads are not
as good as the Appalachian Mountains as a
general rule and are few and far between sometimes.

On new BMW bikes, the 'rule' is let bugs accumulate on
your fork tubes and ruin the fork seals. THEN you go
and replace the seals on warranty (one of the few BMW gimme's),
while putting fork boots and increase the oil viscosity simultaneously.

Lighter people don't notice or notice as quickly, but
even with them, the lighter fork oil has a short oil life.
When the poster described it, it is exactly the same thing.
It gets so distracting, that all you notice when you are riding is the
stupid fork banging. Ask any BMW mechanic what to do.
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Old 05-10-2013, 04:36 PM   #708
rride
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Quote:
Originally Posted by jmcg View Post
Yeah, I figured as much when I saw the amount of flex in the plastic rack.

I'll make do for the commute for now and sort out something more robust for any off-road shenanigans..

Cheers,

JM.
Plus, high on the rear rack behind the rear axle with gas sloshing around is not the most stable vehicle design. If it were lower and in between the axles, it would be better theoretically. It is not as easy figuring out how to do it, but any changes on a motorcycle require planning if it is going to last and be efficacious.
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Old 05-10-2013, 04:59 PM   #709
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Clanking forks

Im probably 200 pounds with all gear and have 3k miles on my Strada...I noticed today the "clanking" on the top part of the stroke...noticed it all the way home from Tellico Outfitters ....if new fork oil will make it go away it will be gone. I don't think anythings bent or loose...I do have a good dealer...so I'll ask him and report back. They..(Eurosport Asheville) are also a BMW dealer.
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Old 05-10-2013, 05:25 PM   #710
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Quote:
Originally Posted by trapperj View Post
Im probably 200 pounds with all gear and have 3k miles on my Strada...I noticed today the "clanking" on the top part of the stroke...noticed it all the way home from Tellico Outfitters ....if new fork oil will make it go away it will be gone. I don't think anythings bent or loose...I do have a good dealer...so I'll ask him and report back. They..(Eurosport Asheville) are also a BMW dealer.
Let me know what they say. Mine seems to do it once the forks get heated up.
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Old 05-10-2013, 05:32 PM   #711
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Heat

Exactly how mine acts...I will speak to Justin @Eurosport tomorrow ..I'd imagine he'll want to see the bike before he agrees to change anything ...but they seem very reasonable and he's a rider too ...never hurts.
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Old 05-10-2013, 10:36 PM   #712
rride
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Quote:
Originally Posted by trapperj View Post
Im probably 200 pounds with all gear and have 3k miles on my Strada...I noticed today the "clanking" on the top part of the stroke...noticed it all the way home from Tellico Outfitters ....if new fork oil will make it go away it will be gone. I don't think anythings bent or loose...I do have a good dealer...so I'll ask him and report back. They..(Eurosport Asheville) are also a BMW dealer.
Thicker is more important than new. They will have some available. Of course I'd just ask for it. I've hung around enough BMW dealers for long enough to know better (hint - it's better asking a mechanic than a shop owner or service writer: even a novice mechanic on minimum wage).

Engine oil range is temperature controlled to viscosity: doesn't start (cold, too thick) to blowing oil out tail pipe (hot, too thin).

Fork oil is all oil almost, so it's main variable is weight: doesn't absorb shock/rigid (light weight forces/ too thick) to doesn't resist force/ bounce unrestricted (heavy weight forces, too thin).

rride screwed with this post 05-11-2013 at 12:08 AM
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Old 05-11-2013, 06:12 AM   #713
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Lighter weight oil does not have a shorter useful life than heavier weight oil, per se. That is simply not accurate. And "thicker" is not necessarily better. In fact, it may be worse!

Regarding "clanking", I've not experienced it on my Terra, but it is usually due to topping out (or bottoming out) of the internal components. It can often be resolved by increasing the volume of oil inside the fork. Add a little at a time (5 to 10 cc) and test. Continue until resolved. Oil is incompressible, so you fill to the point you create a bit of liquid cushion at the top....so to speak....before the cartridge reaches the end and "clanks" metal on metal.

Increasing the viscosity (changing the oil weight) is a band-aid approach. A cartridge fork passes oil thru small orifices (holes in the valve)....back & forth. Lighter weight/viscosity allows more oil to pass thru the valve quicker than heavier oil.....resulting in a greater distance of fork travel for given load over a given time.

So yes, you can slow the fork movement down in a cartridge system with heavier oil, but that can produce several undesirable consequences in your suspension performance.....depending upon your weight and riding style. Too heavy, and your forks will just plain suck.....hydraulic packing will occur frequently (in successive bumps) making the bike handle terribly.

Choose the weight of oil needed to make the forks function correctly for your weight and riding style. Set the oil height to a level that tops out before the internals due, to solve your clanking.

Also, dial-in your suspension correctly by adjusting both static sag and rider sag properly. This will help balance the system to function more correctly. If the rear shock is under-loaded and/or too stiff, you will likely have too much weight/force on the front suspension.....causing it to behave poorly and bottom out too quickly. It's all connected......cause & effect.

If the stock suspension plain sucks (like on my F800GS originally) then nothing will help short of total gut & replacement of internals. However, I have pleasantly found the Terra suspension to be reasonably good for what it was intended to do. Could always be better, of course, but it ain't too bad out of the box, all things considered.

HF
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HighFive screwed with this post 05-11-2013 at 07:49 AM
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Old 05-11-2013, 06:30 AM   #714
trapperj
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Suspension

Makes me wonder if my issue might be self inflicted...I reduced the preload of my rear shock...the front seemed to dive harder under hard braking....also after running hard for a couple of hours on blacktop the front seemed to "wash out" or slide out....to the point I thought something was either on my front tire or was way low on air...something was "real wrong" it seemed to me. I picked a different route home from Tellico because of this...(less curves)

I figure the first place to look is the pre load as that's the only thing that I changed. Tires are good with 3k miles...even wear. Pressure is good....where to look ? Ideas? Reckon I went the wrong way lowering the preload? I lowered because I think at my request the dealer added too much when I first purchased the bike. The online owners manual gives factory specs for damping ....but no such specs for pre load?
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Old 05-11-2013, 08:22 AM   #715
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Something close to 30 - 40mm of Static Sag and around 90mm of Rider Sag might be a good starting point (which would be about 3.5" of total sag when you are sitting on the bike in full gear vs what it measures un-suspended on a stand).

The Terra has what....7.5" or so of travel? I forget exactly. Try Rider Sag near 40% of travel, for starters.

1) get a helper, or preferably two.
2) raise the bike on a stand....wheels off the floor.
3) measure distance from rear axle to a fixed point vertically up near fender or rack....something you can repeat accurately.
4) put the bike back on the ground....under its own weight (without rider) and take measurement again.
5) Static Sag is difference between (3) & (4) above.
6) put on your normal riding gear....helmet, coat, pants, knee pads, chest protector, boots, camelback with water, etc.....whatever you run with.
7) sit fully on the bike....preferably feet on pegs (if you have a 3rd helper to lightly hold bike upright)....or be very light on your tip toes to stabilize bike, otherwise)
8) Helper to take measurement again from same exact points as before.
9) Rider Sag is difference between (3) & (8)

If you can't get close to 40% of travel (+\- personal preference) for Rider Sag while maintaining some reasonable amount of Static Sag, you probably need a different spring weight. Note: these are general guidelines that work well for most bikes being ridden off the beaten path. Helps to have the suspension loosened up a fair bit, before dialing in the Sag. If you're in a hurry, go ride some railroad tracks for a few miles!

I've not measured my own Terra yet, but will do this weekend and report back. I've got close to 3,000 miles on it, so it's a good time to do it now....and College boy came home yesterday, so I have a helper. I would have done it sooner, but honestly, the suspension has been working very well for me so far. I bet it's pretty close to correct setting for my weight & style. I have increased the rear damping a fair bit, though. Stopped the bucking of the rear when jumping my tabletop out back.

HF
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Old 05-11-2013, 10:30 AM   #716
rride
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Quote:
Originally Posted by HighFive View Post

Choose the weight of oil needed to make the forks function correctly for your weight and riding style.

HF
That's exactly what I said to do. The rest may be significant to you, but for the main improvement to the main problem for over 200 lb riders, its as easy as $5 and 30 minutes work.

How much do you weigh? It sounds like you don't have a clue, but if you are a flyweight with unlimited time and money, you may be happy with your complicated algorhythm. I know your mechanic will be since he gets paid by the hour and the fork banging will never be solved. BMW dealers have been giving heavier fork oil for many, many years and empirical evidence is the PROVEN measure of success. You don't have to reinvent the wheel on an immaculate model like the Terra or Strada. Just one simple (and very common) fork weight alteration.

Put more fluid than required? LOL, no comment. That will handle swell.
"That is simply not accurate. And "thicker (or thinner)" is not necessarily better. In fact, it may be worse!"

The BOTTOM line to your solution is NOTHING will be accomplished and they will put heavier oil in the forks regardless, with your escape clause and the one truthful comment reposted above.

Some things are just common sense. One weight oil DOES NOT work for EVERY WEIGHT rider!

The BMW dealer will have a perfect weight oil to go up to because EVERY BMW fork oil is too light for 200 lb riders up from the factory. An increase in oil weight will make it handle like a $3K more expensive bike on the road. And EVERYTHING is within range subsets. But for heavier riders than 200 lbs, the same factory settings and oil capacities with only changing to heavier fork oil will make it feel like a $3K front end upgrade.

Also, your "dialing in" approach narrows the window of the improved handling, making a larger unsafe handling range (on the road with wider mph ranges). Fork oil weight is the best, easiest, safest, and cheapest way to accommodate for a wider range of front end handling exceptions. Yes, it is all connected, but the front end is the most important and correct fork fluid is the base starting point (and ending point as well for most people most of the time - Pareto analysis).

rride screwed with this post 05-11-2013 at 11:13 AM
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Old 05-11-2013, 02:06 PM   #717
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Pre load

Well I got my bike up on a lift and discovered it was on the second position from the lightest setting....I reckon when messing with it in the dark a few weeks ago I "thought" I was in the middle of the setting....so I bumped it up a total of 3 clicks....only a few miles so far....but MUCH better than before. It's amazing what a difference the preload on the rear makes to the front end of the bike. I wouldn't have thought it would be so dramatic. I'll get a helper or two and use a tape and measure later...but I am on the right track for sure!
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Old 05-11-2013, 03:20 PM   #718
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rride....you are far from a suspension expert and your "expertise" on the subject is not expertise at all. Hammering away constantly at the same point is not going to convince everyone, especially those with a half million miles under their belt over decades of riding - and do most of their own wrenching.

It is not simply a matter of using thicker viscosity oil if you weigh more than some arbitrary number of pounds.

There....said my piece, I'll be back to this thread in about four pages after it returns to it's senses
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Old 05-11-2013, 05:07 PM   #719
rride
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Quote:
Originally Posted by Blakebird View Post
rride....you are far from a suspension expert and your "expertise" on the subject is not expertise at all. Hammering away constantly at the same point is not going to convince everyone, especially those with a half million miles under their belt over decades of riding - and do most of their own wrenching.

It is not simply a matter of using thicker viscosity oil if you weigh more than some arbitrary number of pounds.

There....said my piece, I'll be back to this thread in about four pages after it returns to it's senses
You are right. I don't care what you do. But you ARE a light weight and never experienced what is happening, right? As well as dirt bike riders who like to fly high most likely are too. I was not talking specifically to you or them, who seemed to take the most opinionated stance and had the least clue (even if you had 3 million miles at 150 lb rider!) Get 2 engineering degrees from the top engineering school in your programs in the world, and then you may be more logical than your Easy Rider hero wearing the football helmet.

I sway toward what the expert manufacturers engineer and what BMW shops have been doing for decades for heavy riders. Your miles nor expertise do not impress me neither. I've said all that is required but just did not want people to be swayed by you and your small friends perceptions and attitudes about their self proclaimed expertise in something they do not know anything about no matter how much you have collectively ridden or wrenched. I know you are in a minority of mouths though. Don't let the screen door slam shut
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Old 05-11-2013, 05:19 PM   #720
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Hi guys!
New owner here
Reading the posts about the rear rack breaking, has anyone figured out how to make it a 4 point securing system rather than the 2 bolts as stock?

I have not picked the bike up yet so i don't have the visual reference
Thanks!
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