Miele Man

I see a lot of images on various sub-forums here that show panniers mounted such that they are a fair distance behind the rear wheel axle center. Back in the 1980s I had really be shimmy on a bicycle with the panniers a bit behind the rear axle and moving the rack forward so that the panniers were basically centered over the rear axle eliminated that shimmy.

How is it that these bicycles with the panniers so far behind the rear axle don't cause shimmy?

Cheers

Tourist in MSN

Often they will. That is why most touring bikes have longer chainstays, you need to get the panniers back far enough so that you avoid heel strike, but as far forward as you can to minimize frame flex for handling to avoid the tail wagging the dog feel.

indyfabz

Never been an issue for me. I wear a size 48 shoe. Need to get clearance.

dualresponse

I don't know if this is it or not, but in the 1990's I had some 1980's era racks. The rear rack was small, and the front rack was flimsy. The front rack caused all sorts of problems. I ended up throwing it out.

The rear rack, was a small/medium sized 80's rack, but there wasn't enough room to mount my jandd mountain expedition megapacks without healstrike, forcing me to mount them on the rear end of the rack. It never worked right either.

In 2016, I bought a new larger rear rack. Same bike, same panniers. It let me mount the Jandd's more rearward to prevent healstrike, and was a much more stable platform. Shimmy vanished. Same goes for the front racks- when I got new front racks for several bikes, they all were lightyears ahead of the 80's setup I had.

Basically, all the new racks had significantly less flex. Just a thought in addition to the idea of bringing stuff more over the axle.

3speed

In my experience, it's also about balance. I could take my old Trek and load the rear up and it would shimmy at higher speed(downhills, etc). I could put on some front panniers and it would have much less shimmy(though it was a flexy 90 520, so still some). Same amount of weight, same placement in the rear, but add front panniers and it rode better and shimmied less. Maybe that has something to do with the pictures you've seen? There's also the factor that seems really strange to me - those bikes may well have shimmy issues, but the person riding them just doesn't seem to care(or possibly even notice???). I actually rode another guy's 520 from the early 90s because we met on tour and were talking bikes. I told him I got rid of my old 520 because it had too much frame flex and I didn't care for the ride. He said his didn't have that problem and asked if I wanted to try it. He toured with more weight than me and his bike was a noodle. Maybe it was the racks too. I don't know. But it was a noodle. I rode it for all of 30 seconds and could tell I would hate touring on it. I thought it felt sloppy and bendy. He said he didn't feel it and was happy with it. Good for him and I'm glad he's happy with his bike. Could be the same for the bikes you see pictures of.

phughes

I've done this with no shimmy. It is going to depend upon your bike. I got up to about 40mph with this load. The rack is a tubes, and I used nylon tie down straps straps for the trunk. I chose a frame on the large side for me, which helps with stability.

Wilfred Laurier

Same here. When I first loaded my bike up for touring I found there was some shimmy, but it went away after I (1) secured the luggage atop the rear rack so its sway couldn't induce shimmy, and (2) added more weight to the front by strapping my tent to the underside of my handlebar and handlebar bag.

indyfabz

The Nitto Big rack is incredibly solid. No shimmy at all.

thumpism 

I've had shimmy on a bike with rear panniers and handlebar bag, a different bike with different rear panniers and different handlebar bag, a third bike with different front and rear panniers and the same (#2) handlebar bag, and the same bike with that handlebar bag and pulling a B.O.B. trailer. The trailer setup shimmied least but was still detectable. I'd like to find a tourer that will not shimmy.

Tourist in MSN

I have no studies to base this on, but it is my opinion that steel bikes are more likely to shimmy, as they are more flexible than aluminum bikes that often have oversized tubing. I can't recall ever hearing of anyone complain about a shimmey on an Aluminum bike. If I am wrong on that, I am sure we will hear about it here.

My Sherpa (first photo below) does not shimmy, even with a heavy load. My Nomad (second photo below) with an exceptionally heavy load will have a very slight resonance in the 29 to 31km/hour range, but it is just barely perceptible and dissipates if I loosen up my grip on the bars. (Yes I said that correctly, loosening my grip on the bars reduced resonance.) Both of those bikes are steel, but they have robust tubing that results in a fairly heavy bike.

Miele Man

That's exactly the type of setup I was wondering about. So it's the racks that have become more solid than the ones made in the early to mid 1980s. That's good to know.

Cheers

thumpism 

The instances I mentioned all occurred on steel framed bikes and all with either 27" or 700C wheels. I have not toured on an aluminum framed bike, nor on a 26" wheeled bike of either frame material. Before I go spending bucks on an aluminum touring bike (was that close to an older Cannondale but got scooped) I should give my steel Cimarron or aluminum Marin 26ers a try.

It may be true that modern racks are stiff, but I have a hard time believing that they are significantly stiffer than an old seatstay-mount Blackburn or Eclipse, or one of their front racks.

indyfabz

I've never had any experience with flexi racks. My fist set, which I got in the spring of '99 before my first tour, were custom jobs made by Robert Beckman, who used to work with Bruce Gordon until they had some sort of falling out. Unfortunately, those racks were stolen from my home in 2010 along with the Surly LHT they were attached to. The Nitto Big racks were the closest things I could find to replicate what I lost.

robow

Shimmy can definitely occur when you get a bike where the rear triangle is not rigid enough for the amount of torque being placed upon it. There were several "touring" bikes that were under built in the 80's where this was a common problem if your load wasn't well balanced. But yes, I do think bike racks today in general are built stronger and with more rigid over sized tubing than in the past.

One last note, a close friend of mine bought a brand new Trek 520 two years ago and it shimmied terribly right from the get go. She is a small woman not weighing much over a hundred pounds and she was carrying only a moderate well balanced load with both front and rear panniers. Her frame size was really small so it should have been stiff as heck yet just riding along on flat ground, you could see that frame wobble in the rear. She took it back and no one could figure out what the source of the problem was but they replaced it with a Surly LHT and all was good. Not a knock on all 520's, but just shows that a poor frame can show up anywhere.

Tourist in MSN

The two bikes I showed photos above are 26 inch, but I see no reason that a 26 inch bike would be any different than a 700c bike when it comes to shimmy. I had a LHT in 700c that had a terrible shimmy. Surly refused to warranty it, the bottom bracket shell was warped. I put the frame in a metal recycling bin it was so bad. I talked to a frame builder and she said that it was very possible that the bad welding job on the bottom bracket shell caused the shimmy as that whole part of the frame was weaker from the welder not having his heat control settings right.

A friend of mine used to tour on Aluminum, he was happy with it. As far as i know, it had no shimmy although he had all the weight on the back rack. Then he bought a Titanium frame, had a minor shimmy when all the weight was on the rear rack, but he minimized the shimmy as much as he could by moving the rear panniers as far forward as his heels would allow. When he added a front rack and panniers, I think that greatly reduced or got rid of the Shimmy.

I usually tour with a Tubus Logo rear rack. It is stiffer than the Surly rear rack although the Surly is twice as heavy. I can't say if the Tubus is stiffer than an old Blackburn or not, but the Tubus is much stronger than the Blackburn. The Tubus Logo is rated at 40 kg.

I should have mentioned this in the posting above with the photos, the Sherpa chainstays are 450mm, the Nomad chainstays are 466mm. Thus, when I switch the panniers from one bike to the other I have to change the upper pannier hook positions, I always set the panniers as far forward as I can without heel strike.

phughes

The bike in the photo I posted is steel. No shimmy. I can make it feel wiggly if I violently move the bars back and forth, but simply riding the bike normally, no, it is rock solid when loaded, at any speed.

I truly believe it is more stable than the same frame, a Long Haul Trucker, would be in the next size down. I could fit a 54cm frame, but chose the 56cm frame for a bit more stability. Seems to be working out.

hilltowner

My experience with shimmy has more to do with weight forward rather than weight rearward. This is a good treatment of how to distribute the weight. https://www.adventurecycling.org/sit...tage_Heine.pdf
I agree with him on one point in particular. It's a guaranteed way to start a "lively discussion" among bicycle tourists. Amount of "trail" (fork offset differences) is also a factor in shimmy complaints.

Miele Man

I should have mentioned that the bike I had that shimmied before I moved the rear rack forward a bit (about 1/2 inch at most) was a steel BIANCHI MTB with straight bars. I later converted it to a dropbar.

I think that at the time of shimmy it was with a Blackburn rear rack but I'm not positive.

I did not have any problems with that bike when I toured on dirt logging/mining roads and was using Nagaoka front and rear racks. I loved those racks and would love to get another pair. One of the things I liked about them were that both had semi-lowrider attachments on them. One the rear that meant I could carry something on top of my side-opening panniers.

Here are two poor images* of that BIANCHI MTB with the NAGAOKA racks whilst I was on a two-weeks long unsupported tour of logging/mining roads in Northerm Ontario, Canada back in the mid-1980s.






If anyone knows where I can get a pair of those Nagaoka racks I'd really appreciated hearing about it. VBG

Cheers

* Images are scans from 3" x 5" photos.

phughes

Nice old photos. Great memories, I'm sure. You will have to simply keep searching for those racks if you want them. In lieu of those, Tubus racks are very well made, and strong.

bwilli88 

I had a couple of bikes that shimmied. My Pro Tour did but I readjusted the headset and it went away. The other was my Zunow and I put a roller bearing headset on it and it was great. Another is my Fuji Stratos and it had a cartridge headset but it is just a noodle, it has become my bomb around town bike.

djb

miele, I really do think that this is a tricky topic to get reliable answers because of the so many factors that come into play for shimmy wobble issues.
From my experience, racks can be a part, slight or not so slight weight placement issues, headset issues, and most importantly, specific frame characteristics that affect how the other factors come together.

re materials, steel vs alu, I think its more frame design, although I'll be honest and my two alu bikes are stiffer than my steel frames and this seems to be a factor iin them being rather stable.
My old 90s alum Spec Rockhopper , even with a front suspension fork, has a typical of that period very solid alum frrame and thick chainstays, kinda like Cannondale tourers. Ive ridden this bike with a heavy rear only load and the inherent stiff frame handles it really well, so I do think the frame characteristic is a big part with this bike.

My Troll can have a slight wobble shimmy if I have too much weight in my rackpack, on top of my rear panniers, so I learned very quickly to keep the high up weight to a minimum, and it immediately went away (I keep my heavy extra water or food in a pannier now, and have tent and other less heavy stuff up high in rack pack)

Ive always noticed that being reasonably even loading side to side weight wise helps also, with front racks also, in an overall sense, so I tend to instinctively try to balance out pannier sides for weights. That said, both my old mtb and my old steel commuter ride really rather well with one heavily loaded pannier only with groceries--ie one stupidly heavily pannier on the bike and thats all--so clearly diff frames can handle weight differently.

My troll is my most robust bike, and I figure the very sturdy and wide front fork plays a part also, as well of course as the Tubus racks which are really solid. To add to the racks issue/strength, I have fattened up my rack rails so that my panniers fit on them tightly, ie there is no play at all or looseness, so panniers are solid , dont sway or even budge at all which Im sure helps with handling as everything is one good solid mass. In the past, Ive had panniers that swayed a bit, and were loosey goosey a bit all in all.

John N

When a QUALITY loaded bike is shimmying, it is most likely due to weight distribution. Assuming all the racks are quality, the racks are fastened on securely, etc. the amount of weight and where it is located is factor. Historically, you should have at least 40% of the weight over the front wheel, not the rear wheel, and all gear should be loaded as close to the the center of gravity and as equally balanced side to side as reasonably possible. This is also true for non-quality bikes but if a really cheap bike, the frame design & manufacturing itself may contribute.

If you have heavy rear panniers and all your other stuff loaded on the rear rack and a small handlebar bag up front, you have a decent chance to get shimmy, especially on a fast downhill.

Solution, put more stuff in front low-riding panniers. If my gear for a given tour weighs more than 25 pounds total, I will divide between front and rear panniers. I always put the heavy stuff (tool kit, batteries, food, etc.) up front. I personally strive for at least 50% up front as I really do not like to be going 30mph down a hill and start to get shimmy as I did in my early touring days. The only downside is it makes the steering much slower but unless you are doing bikepacking (which uses a different packing system typically), this is not a big deal.

If you want to test this, put a bunch of 1 gallon or 1/2 gallon jugs of water in your rear panniers only and a gallon or more in your handlebar bag nut nothing in front panniers, strap on a few pieces of firewood or something heavy to the top of the rear rack and ride down a steep downhill. USE CAUTION and don't blame me if you crash because you didn't slow at the first sign of shimmy. Then ride down the same hill after putting at least half the the WEIGHT in front panniers/rack and remove the firewood (weight transferred to front) to lower center of gravity. Again, keep the total weight the same, just distributed with at least 40% in the front panniers & rack. Any difference? This is because the weight is better distributed.

Another way to look at this is it is similar when pulling a trailer in a car. If you put the too much weight toward the rear of the trailer, the trailer starts to shimmy causing the car to shimmy (tail wagging the dog). That is why you are supposed to have about 10%-15% of the weight on the tongue (coupler) of the trailer for safe trailering.

Tailwinds, John

pdlamb

I suspect we'll get a definitive single answer to "What causes shimmy?" right around the time we get a definitive single answer to "What causes cramping?" There are so many things that can contribute to either than neither question has a single answer.

TiHabanero

In the 70's we toured using the fabulous Pletcher rack. The tail wagged the dog all the way, every day. Just learned how to ride and climb without upsetting the rack and all was good. The Blackburn racks were a real revelation when they were introduced. Still use the same Blackburn from 1985. Don't have issues of wag, but that may be due to the excellent practice I had working with the Pletcher.

Tourist in MSN

I remember those, if you had any weight on the rack and hit a bump, the clamp holding the rack would slip down the seatstays and jam against the brakes. If you had sidepulls, your brakes were locked up unless you brought some tools with you and nobody carried that set of tools on the bike.