jtaylor

On the first day of my recent U.P. tour with my new Trek 520, I was shocked to find that my front wheel was shimmying all over the place when fully loaded, including front panniers. Riding at a comfortable pace, I couldn't stop my front wheel from moving back and forth like it had the DTs. I was very surprised at this, because I had heard from multiple posters on this site that a Trek 520 actually rides more smoothly when fully loaded than otherwise. Also, prior to the tour, I had loaded up the front panniers (with lighter material than I ended up with on the road) and experienced no problems during test rides. I was able to reduce the shimmy the first day by making some weight adjustments, and that night I rearranged my load completely so that much less weight was in the front. I also tightened up all the compression straps on the front panniers. That seemed to fix the problem. No front-wheel boogy for the rest of the tour, but my initial surprise and disappointment remained. Anyone else experience this?

BTW I have big-ish Trek panniers on a Tubus Duo front rack. The rack is rated for 33 pounds (16.5 pounds each side), and before my weight readjustment I had probably close to that in the front panniers.

bradw

Last year I did my touring with most of the load on the back except for a moderate-sized handlebar bag. The bike was generally OK but I didn't like slow speed handling.

This year I installed a front rack and panniers, shifting a good portion of the weight to the front.

Handling problems solved.

I hate to ask this question, it seems too obvious, but you did balance the weight on the front equally between the two panniers? Balancing the weight doesn't matter as much in the back, but seems very important up front.



Also, do you use a large handlebar bag? I've found that a heavily loaded handlebar bag, especially if not balanced by front panniers, can cause some slop in the steering.

jtaylor

bradw,

Yours is exactly the kind of post I thought of when my front wheel started shaking all over the road. I thought, "Isn't this bike supposed to handle even better when it's loaded up front?"

Yes, I was perfectly balanced between the two front panniers. I do have a sizeable handlebar bag, but it holds mainly maps, a camera, and a cell phone. Not much weight up top.

bradw

Well maybe you had to experiment with the front-to-back weight ratio. Maybe 30lbs up front upset the steering.

I have relatively light items in my front panniers: tent, bag, pad. In the back I'll have tools, spare tire, clothes, pillow, food, books, etc. I'm not hauling a stove or several days of food.

Bekologist

jtaylor, I had the same problem with a 2005 520 lightly loaded up front with about 6 pounds in each pannier on a jannd lowrider and a small handlebar bag, it began the fatal death wobble at about 25mph and was incredibly irritating, not to mention dangerous.

Same rack, same load on a LHT trucker and there's no problem grabbing a drink of water at 40mph... I think the 520 fork has something wrong with the rake geometry or trail. Regardless, try a lighter load up front, but it may be a problem that can only be fixed by switching to a different bike.

Dahon.Steve

I also think moving to a 26' inch with a thicker/heavier fork is the LHT's advantage over the 520.

Bekologist

..i'm riding a 700c LHT

bradw

I switched my 520 over to a flat-handlebar with extensions. This may give me extra leverage and reduce the possibility of wobbles. Also, I've only had the bike up to about 38mphon a downhill. I'm not brave about charging down hills.

The geometry of the 520 changes a little for each size. Maybe there's a particular size that is prone to high-speed wobble? I ride a 21".

If you'll notice on the table linked below, head angle, trail and seat angle change with size.

https://www2.trekbikes.com/Bikes/Spec...0/Geometry.php

I'm also a bit heavy at 200lbs. Could this have a damping effect?

I should be leaving on a multi-day tour on the 17th. There will be a few short but steep hills. I'll pay attention to how the front end behaves with a fully loaded bike front and back.

skookum

I've had this problem, too, (not on the same bike) and I have never been able to make it go away completely. It was fine without panniers but as soon as I loaded the front, watch out! It was bad enough that it was causing my stem to loosen and then my handlebars to twist. I had to tighten my stem with a big cheater on the alllen wrench to get it so it wouldn't loosen.

Check your handlebar bag. I have seen heavy handle bar bags cause this problem. When the handlebar bag was removed the problem went away.

Reduce weight in the front and try to pack your panniers so the weight is on the inside of the pannier nearest the wheel.

I found that the problem was worse at slow speeds like maneuvering in city traffic and just about non-existent at high speeds, like going down hills. I also found that as time went on, ie. the second or third week of the tour I noticed it less. I think the body needs time and training to adapt to the different balance of the bike, but it seems to do so.

Good luck.

taylor8

Just a thought. Have you checked your spoke tension? Could the wheel be flexing? I have had some strange wobbles on wheels with spokes that are not up to proper tension.
Joe

gazelle

I have found that keeping the weight as low as possible on the front end greatly changes the way the front end acts. On my Cannodale the same panniers and load shimmy slightly at high speeds when they are placed high on the rack and do not when placed on the lower part of the rack. Just a thought.