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Old 05-21-12, 06:15 AM   #1
lachy94
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Saddlebag induced shimmy

Hey guys,

I've been using my Carradice on my newish touring bike. I've been feeling some odd kind of shimmy feelings, mainly in rhythm with my pedal stroke at medium cadences and occasionally at speed. Riding with front panniers as well the other day I could feel the sensation amplified by the extra weight at the front.

I've got the bag on a bagmen QR rack. Previously, I had used it strapped straight to the saddle and seatpost of another roadbike and never felt this. When the bag is loaded; grabbing the bike by the saddle and rocking it (as I imagine my pedalling does) you can clearly feel the bagman wobble side to side and feel this moving through the frame.

My question is; is this a symptom of having the bag set too far back or just an issue with the bagman racks?



I would say its centre of gravity is probably just behind the rear axle, vertically. The chainstays are plenty long, 44 or 45cm, it's just a very big frame (yes those are 700c wheels), and 63.5cm of 72 degree seat-tube puts the saddle a long way back. I could move the wheels about 1cm back in the dropouts, and I could bend the rack forward a bit, which would probably get the *centre of gravity* in front of the axle, but not the whole bag.

Would this actually fix anything or do I simply need a more rigid mounting solution? I think I want to tour with the carradice, a large berthoud and my super C front panniers, but if I can't cure this shimmy problem I guess I'll be joining the 4 panniers club
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Old 05-21-12, 07:39 AM   #2
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I have a bag about that size on my saddle. I put a toe strap from the bag to the seat post and it reduced the motion greatly. I don't have a metal frame like you do; it was just hanging from the loops on the seat, but something like that to stabilize your setup might help.
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Old 05-21-12, 10:31 AM   #3
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Their Carradura bags, put a mini-rack pocket in the bottom of the bag.
and supplied a rack to fit that pocket over..

My non Brooks saddlebag mount kludge is Minoura's 2 bottle back of the saddle mount.
with that I can P clip around the support dowel.
the strap holes line up with the bent alloy rod bottle cage mount.

Other than that there is a rear rack under the bag .. I've had no issues..
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Old 05-22-12, 06:19 AM   #4
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I've got Carradice Barley and Pendle bags with Bagman QR racks and have never had a problem with them wobbling or swaying. In fact, I had such problems before I got the rack. My suspicion is that the clamp isn't secure on the saddle rails or perhaps you tightened the Allen bolts without the rack tubes fully inserted in the clamp. Try loosening the bolts way out and the then push the rack tubes in as far as they will go, and tighten securely. Also use some Loctite. When I first installed my Bagman the bolts worked loose within a week or so, causing a lot of wobbling.
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Old 05-23-12, 11:23 PM   #5
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Thanks for the input Tarwheel, I'll give it a go...

On a *very* unrelated note, I've seen your bike on flickr and also ride a bob jackson- How have you found the nitto front rack? does loading it up cause an uncomfortable amount if wheel flop with the bob jackson geometry? I'd like to get a Berthoud front bag, but I don't want to invest if the ride experience will be poor.
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Old 05-24-12, 01:58 AM   #6
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Jeeeeze how many beers do you need to take with you when your riding??
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Old 05-24-12, 06:22 AM   #7
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Originally Posted by lachy94 View Post
Thanks for the input Tarwheel, I'll give it a go...

On a *very* unrelated note, I've seen your bike on flickr and also ride a bob jackson- How have you found the nitto front rack? does loading it up cause an uncomfortable amount if wheel flop with the bob jackson geometry? I'd like to get a Berthoud front bag, but I don't want to invest if the ride experience will be poor.
To be honest, I am not crazy about how the BJ rides with the front rack loaded. I wouldn't say that it causes wheel flop, but makes the bike handle differently. It also it blocks my view of the front wheel, which I don't like. However, the rack is nice having because I bike commute and sometimes need to carry extra gear, like a package to mail at the post office. I've got a Rivendell Lil Loafer bag that fits the Nitto rack perfectly but it doesn't hold much. I haven't ridden the bike with a front bag as large as a Berthoud. I recently bought some front panniers and Tubus Tara rack, but haven't had an opportunity to install them or ride the BJ with them.
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Old 05-24-12, 06:27 AM   #8
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My guess is it's a combo of factors, including (as mentioned above) that it's a bit loose.

However, weight being that high up affects the bike's center of gravity, and might alter the handling if there is too much weight in it. This would be offset or modified by bags elsewhere on the bike.
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Old 05-25-12, 09:14 AM   #9
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Tail waging the dog......That's the worst place you can put weight. It needs to be secured tight with no swinging.You wouldn't strap a shake weight on your seat,same thing.

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