Dog bone length

[roortcloud]

Gentleman
I noticed recently that my rear tire has contacted the inner fender on both sides (a lot) just forward of the fender mounting screws. (Fasteners were also contacted by the tire)
Some specifics about my bike first.
1989 FJ1200W
Rear tire is a Michelin Pilot Power 3 / size 180/55-17
Rear shock is RPM. Installed and adjusted for sag by Randy but can't remember the number.
Dog bone length is 11.5cm hole center to hole center. (4.527") Stock hole spacing is 4.160" center to center.
I was surprised to discover that much travel in the rear wheel. Has anyone experienced this issue?
I don't know when it happened but assume it was a result of additional weight on-board.
I have adjusted the pre-load of the rear shock to make it stiffer when I add luggage & camping equipment.
It seems to me that adjusting the pre-load more & more to correct the problem limits the travel of the wheel, rear shock, & may reduce that "magic carpet ride"
Would changing the length of the dog bones help? Changing the length increases the riding height which also effects steering characteristics correct?
I made this set myself with numbers suggested on the forum & will make a new set if required. Any recommendations?
Thanks.
Ron

[ZOA NOM]

I have the same dogs and wheel/tire combo. Never had an issue. My RPM shock is adjusted midrange, but I've never carried much weight back there.

[roortcloud]

I thought about it some more & there's one other thing to consider.
The lower shock mounting bolt broke some time ago and damaged the lower end of the shock slightly.
The shock stayed in place for the most part.
Most of the contact with the inner fender is along both sides.
Anyone replace this fender with something else?
Ron

[aviationfred]

Would changing the length of the dog bones help? Changing the length increases the riding height which also effects steering characteristics correct?

Ron

The answer to this question is yes, shorten the dog bones a bit more will raise the inner fender further from the tire. You have already stiffened the spring preload on the shock, that should help also.

Maybe this will help..... When I had my 89 with the RPM shock and running a 180/55/17 tire I had no issues with the tire contacting the inner fender. I had DIY fabricated dog bones. Here was my set up. Bike on the center stand, I placed a 1/2" piece of board under the tire and removed the dog bones. With the tire sitting on the board, I measured the attaching point hole centers. IIRC the hole centers for the dog bones were real close to 4" exact.

On another note. the inner fender is not that difficult to replace and they are plentiful on eBay.

This one even comes pre decorated.... https://www.ebay.com/itm/89-Yamaha-FJ-1200-used-Rear-Fender-Splash-Guard-Shield-Inner/333099505577?fits=Model%3AFJ1200&hash=item4d8e4717a9:g:3VIAAOSwUHRceqxz:sc:USPSPriority!67207!US!-1


Fred

[roortcloud]

Thanks Fred.
The fender is still in reasonably good condition so I won't need another one. I'll clean it up enough to remove the tire rubber & scratches & keep a close eye on it. Since no one else has experienced this issue hopefully it happened when the shock bolt broke!

[aviationfred]

The machinist put a zerk fitting for the swing arm dog bone mount. I need to put one in the swing arm relay. Before the zerk fitting, I would pull the bolts out, wipe off any old grease and regressed once a year or whenever I changed a rear tire, whichever came first.

The Soupy's adjustable dog bones are nice and easy to make rear height changes.


Fred

[great white]

Just so you are aware, changing the link length also changes the ratio for the progressive linkage. The linkage has a "rising rate". Meaning; as it travels through it's arc, it increasingly compresses the spring more and more. You may notice a difference, you may not. It all depends on how "in tune" you are with the ride quality and control. Increasing a rising rate suspension also means it "works" the spring more through its travel. If the spring has already fatigued, then i creasing the rising rate can fatigue it further or faster. It's not likely to break or anything catestrophic like that,  but the wear will increase.

As you mentioned, raising the rear also affects steering geometry. It reduces rake and trail. This effects steering "quickness", but it can also effect steering stability. The FJ is pretty conservative considering it's frame and you have to go pretty extreme to get it to act up negatively. Most guys "sport touring" will never really push it hard enough to tell if they have gone too far with the alterations anyways.

If you're carrying loads where you're hitting the inner fender, you need more spring. In cases like this, I would suggest a revisted spring rate.

If it was just a "one time deal" where the tire hit, you likely just had it overloaded that time. But if you are hitting regularly, it's time for a higher spring rate.

Or, depending on the amount/type of mileage on the current spring, it might have fatigued (all springs fatigue with enough cycles) and is now, effectively, operating at a lower spring rate. If this is the case, a simple replacement gets you back to riding level.

If you nust want to rsise the rear for more travel, a longer shock is the proper way to do that. Unfortunately, the stock FJ shock has no provision for that. It means a nee shock or radical alterations on the stocker.

I only mention these things so you can make an informed decision on what to do. Longer links might be the way you want to go and that's ok, as long as you understand what you are actually changing in thesuspension (and steering) geometry.

[ribbert]

............. Since no one else has experienced this issue........!

Not so fast, I do.
I have much the same set up, raised rear end, 17"/180 tyre (although that's irrelevant) and expensive shocker, mine bottoms out also. On regularly travelled roads when I know where it happens I momentarily take the load on my legs, on roads I'm not familiar with, it knocks the wind out of me, then there's my back.....

It  happens (not so much in the US though).

Noel

[ribbert]

The Soupy's adjustable dog bones are nice and easy to make rear height changes.

Fred

Fred, as you may recall, I'm a tradesman, I have an eye for, and experience of under engineered parts. Some years ago I ordered a set of Soupy's adjustable bones, what a great idea I thought. When they turned up I can remember rolling them around in my hand and thinking.....nah!

IMO they have two problems, one is the threaded linking between ends isn't beefy enough, and probably the most relevant is the potential for not being exactly the same length. When this happens the load is effectively taken on one link only.
Yes, they can break, I recall a member had this happen not long back?

I could not relax riding with them. Maybe in Kansas they don't get a pounding but if something relies on smooth roads to not fail, that's too fine a margin for me.

The load on bumpy roads is high but the momentary load on components when your suspension bottoms out is enormous.

Noel

[ribbert]

....Most of the contact with the inner fender is along both sides.

...at least you know your wheel is centralized!

Noel

[great white]

....Most of the contact with the inner fender is along both sides.

...at least you know your wheel is centralized!

Noel

[great white]

The Soupy's adjustable dog bones are nice and easy to make rear height changes.

Fred

Fred, as you may recall, I'm a tradesman, I have an eye for, and experience of under engineered parts. Some years ago I ordered a set of Soupy's adjustable bones, what a great idea I thought. When they turned up I can remember rolling them around in my hand and thinking.....nah!

IMO they have two problems, one is the threaded linking between ends isn't beefy enough, and probably the most relevant is the potential for not being exactly the same length. When this happens the load is effectively taken on one link only.
Yes, they can break, I recall a member had this happen not long back?

I could not relax riding with them. Maybe in Kansas they don't get a pounding but if something relies on smooth roads to not fail, that's too fine a margin for me.

The load on bumpy roads is high but the momentary load on components when your suspension bottoms out is enormous.

Noel

Here's the post you were thinking about:

http://www.fjowners.com/index.php?topic=3148.msg175538#msg175538

Yep, broke right at the thread/eye end transition. If you know what you're looking at, the area that is going to be highly susceptible to stress riser is pretty plain to see....

[ZOA NOM]

*centered

[Pat Conlon]

The Soupy's adjustable dog bones are nice and easy to make rear height changes.

.......IMO they have two problems, one is the threaded linking between ends isn't beefy enough, and probably the most relevant is the potential for not being exactly the same length. When this happens the load is effectively taken on one link only.
Yes, they can break, I recall a member had this happen not long back?

I also have Soupy's adjustable and I have ruined a set of bearings from not having the adjustable bones set even. The course adjustment threads give you no where near the precision you need to get them even. Even if you manage to do it, you will change the setting when you tighten the lock nuts.
Even a millimeter difference in length between the two will cause uneven loading.

My friend Paul made a neat jig I now use to set the bones. I can get each bone set dead nuts even and locked in on my bench only then do I install them. There is no way in hell I can get those adjustable dog bones even by adjusting them on the bike. Gotta do it on the jig on the bench.

It's important to note that the failure of the Soupy dog bone was a single bone used of a R-1 swing arm conversion.

Fred, is that a crack on the weld on the swing arm link mount? (Chain side)

[aviationfred]

The Soupy's adjustable dog bones are nice and easy to make rear height changes.

.......IMO they have two problems, one is the threaded linking between ends isn't beefy enough, and probably the most relevant is the potential for not being exactly the same length. When this happens the load is effectively taken on one link only.
Yes, they can break, I recall a member had this happen not long back?

Fred, is that a crack on the weld on the swing arm link mount? (Chain side)

Good eye Pat.

Had me worried for a moment. I went and cleaned the weld and found no crack. What you see is a small ridge where the weld stops.

On the thread with the broken Soupy's dog bone. http://www.fjowners.com/index.php?topic=3148.msg175538#msg175538

My take on the failure is not so much on a badly engineered dog bone, but as on that particular bike, only one dog bone was being used. These are engineered and intended to be used as a pair.


Fred