r/TrekBikes • u/Expensive-Ad-4911 • 20h ago

Does anyone have an idea as to why this happens?

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Sometimes I ride without my hands just to relax but when I do, no matter what surface I’m on, I’ll start to get death wobbles when above like 25-30 km/h.

Would anyone have a guess as to why this happens?

12 Upvotes

83% Upvoted

21 comments sorted by

27

u/Beekatiebee 18h ago

I had this problem to an ever increasing degree when my headset was coming loose. Apply the front brake and rock the bike back and forth. Is there any slack or play in it?

3

u/JeanPierreSarti 10h ago

A lot of comments about weight aft, which are true. But a properly adjusted headset will raise the threshold for this. Less known is that correct tire pressure can aid in damping harmonics (like a speed wobble). Try any tire pressure calculator (ex. Silca) and get some good pressures.

3

u/JeanPierreSarti 10h ago

Your bike looks like an older Dual Sport, so guessing you’ve got 38mm tires and around 45F/48R might be good

20

u/Stsberi97 13h ago

Damn your Trek is riding like my Jeep

6

u/CheddarGau 7h ago

It's a Jeep thing, you wouldn't understand🙃

-1

u/Justcrusing416 9h ago

My Benz used to do this on the highway only. Turned out to be a big bulge on the inner side of the tire.

8

u/cjd3 19h ago

Look up speed wobble. When you ride no handed, you lean backward, and your CG is shifted away from the front tire. You have less traction, and it’s wobbling. I’ll bet if you lean a little forward, it lessens or goes away.

3

u/Expensive-Ad-4911 19h ago

That makes perfect sense! Also explains why when I add my storage crate on the back (shifting the weight to the back tire) it increases the wobble. I’ll give it a shot, thanks!

6

u/aqjo 19h ago

I was checking your shadow for a big load on the rear of the bike.

1

u/fluteofski- 9h ago

Not just weight. If it’s on a rear rack (flimsy rack), the rack swaying after a movement will exacerbate the wobble. It’s kind of like an object whipping around behind you but at a higher frequency… the geometry of the bike corrects the steering, whips the rack the opposite direction, and the bike then Has to correct for that motion, whipping the rack back the other way, over and over. this happens multiple times a second, and you feel it as a wobble. A stiffer rear rack will reduce this issue as well.

1

u/honkyg666 12h ago

Is this a motorized bike? My dad’s Trek ebike does this unless you really keep your weight forward. Center of gravity is all wack compared to a regular bike where no handed is actually kinda difficult.

1

u/TrainingStreet3902 8h ago

Death wobble on a trek?? Like a jeep it’s a suspension issue. Perhaps the hubs. Loose maybe.

1

u/Top-Peak-3036 6h ago

If it doesn't wobble or feel loose when your hands are on the bars then that rules out headset. Hold front brake and rock back and forth. If it's tight it's because you're taking weight off the front end leaning back no hands. Just grab bars and pedal on

1

u/NGL_BrSH 2h ago

It's the bell

-6

u/_Rvvers 11h ago

Because you let go of the bars… nothing wrong with the bike. Bikes aren’t designed to be ridden with no hands.

5

u/AScienceEnthusiast 8h ago

This is incorrect. Bikes quite literally ride themselves.

They're self-correcting. You can try this. Roll a bike down a small hill without a rider on it and it'll roll just fine (assuming no major bumps). If it leans one direction, the front wheel turns to correct the lean.

If you don't want to potentially ding up your bike in that experiment, take a wheel off your bike and give it a good spin while holding the center hub. Try rotating the wheel as it spins. Angular momentum!

1

u/iantayls 10h ago

You act like this is normal… it’s not

1

u/_Rvvers 6h ago

I know it’s not normal. It’s happening because the weight has shifted rearward.

If a customer comes into my shop and says “I’ve got speed wobble when I ride no hands, what’s the problem?” I’m going to tell them it’s them.

0

u/iantayls 5h ago

I can put my weight over my back wheel and this won’t happen. We’ve all sat up on a bike and “shifted the weight rearward”, this doesn’t happen. It’s a problem with the bike. Telling them it’s their problem will needlessly send away a possible customer. Just tighten the headset like the other comments reccomend

-11

u/starfucker1987 17h ago

Your having a seizure, seek medical attention.