Problem when braking hard

FreeHueco said:

I have a steel fork, steel frame and a 1 1/8 inch threadless headset. When I brake hard, the wheel bounces around a lot, and is very hard to control. I took the bike into the shop this morning, and they tightened the headset, yet this is still happening. Can anyone provide feedback on what else might be going on? I kind of suspect the brakes (cantilever) or excessive flex in the fork, but any other ideas would be appreciated.

If there is no headset play, it could be fork flex or your catis are loose or flexing too.

FreeHueco said:

I have a steel fork, steel frame and a 1 1/8 inch threadless headset. When I brake hard, the wheel bounces around a lot, and is very hard to control. I took the bike into the shop this morning, and they tightened the headset, yet this is still happening. Can anyone provide feedback on what else might be going on? I kind of suspect the brakes (cantilever) or excessive flex in the fork, but any other ideas would be appreciated.

Does it make a repetitive clunking noise? if it does while moving back and forth, it could be the brakes hitting the rim joint and catching.

FreeHueco said:

I have a steel fork, steel frame and a 1 1/8 inch threadless headset. When I brake hard, the wheel bounces around a lot, and is very hard to control. I took the bike into the shop this morning, and they tightened the headset, yet this is still happening. Can anyone provide feedback on what else might be going on? I kind of suspect the brakes (cantilever) or excessive flex in the fork, but any other ideas would be appreciated.

Bent rim, insufficient damping in the shock.

A couple of ideas:
The front wheel may not be in the fork straight, which is easy to do.
One of the front brake pads may be loose.
One of the front brake pads may be worn and hitting the actual tire, not good.
The front brakes are out of adjustment: quick check...the pads should be the same distance from the wheel rim on both sides and the brake arms should move the same amount when you apply the brakes.
The wheel rim may be out of true. Spin the wheel and watch the gap between the brake pad and the wheel rim.

Good luck. Let us know how you make out. P.🙂

FreeHueco said:

I have a steel fork, steel frame and a 1 1/8 inch threadless headset. When I brake hard, the wheel bounces around a lot, and is very hard to control. I took the bike into the shop this morning, and they tightened the headset, yet this is still happening. Can anyone provide feedback on what else might be going on? I kind of suspect the brakes (cantilever) or excessive flex in the fork, but any other ideas would be appreciated.

If the whole of your brake assembly is loose (so the parts can tort with respect to each other) this can cause the brakes to rotate when one arm hits the rim, and then lock and release in a juddery motion... might be worth checking the blots running throught the brake assembly are tight enough also. As always.. sheldon brown knows best!

Tyre pressure may be too high.

What size wheel and tyre?

FreeHueco said:

I have a steel fork, steel frame and a 1 1/8 inch threadless headset. When I brake hard, the wheel bounces around a lot, and is very hard to control. I took the bike into the shop this morning, and they tightened the headset, yet this is still happening. Can anyone provide feedback on what else might be going on? I kind of suspect the brakes (cantilever) or excessive flex in the fork, but any other ideas would be appreciated.

Fork and steering tube flex are the most likely candidates. Stiff steel forks and 1-1/4" steel steering tube on our tandem make a huge difference over our previous tandem with lighter steel fork and 1" steering tube.
The more you weigh the more rigid you need the fork/steering tube to be stiffer. Distance between top and bottom headset races also makes some difference as there is more steering tube length to flex between the bearings.

Stand in front of the bike, grab the front brake, and on a high traction surface, slowly move the bike back and forth while watching the fork, brakes, or headset for movement/play. Also, while the wheel is in the fork, try to move it side to side to see if there is any play in the bearings.You didn't specify if it was an oversized fork or not, but I have seen fork chatter during hard braking with non-suspended and suspension forks.

graphixgeek said:

I have seen fork chatter during hard braking with non-suspended and suspension forks.

I have a similar problem with a suspension fork, Mavic 221 rim, and 26x1.50 tires. But if I use the same bike and fork on a DeeMax rim and a 26x1.95 tire, I don't have the chatter.

Aside from the brakes, I suspect it's the fork. But if indeed it's the suspension fork, what could be wrong with it on the thinner tire and not on the fatter one?