Fork Direction

[floridabike]

I originally turned the fork backwards as instructed and installed 700c wheels/tires and have about 500 miles on the bike. Because of the area that I ride, rough streets and sand, I decided to try 26" wheels with 1 3/4" tires. Because the front fork was designed for the 700c wheels I couldn't use the same brake setup with the 26" wheels. However, turning the fork back to forward, the brakes lined up perfectly with the 26" wheels and I did add safety clips on the quick release to insure it doesn't slide out of the slot. This moved the front wheel about 3" forward and after about 50 miles of riding I don't see much difference in handling. My question, why is it recommended to turn the fork backwards.

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[floridabike]

Files attached.

 

[Doug Burton]

To preserve trail dimension, and improve high speed stability

Your bike now has positive trail, the distance on the ground between a line drawn vertically down from the axle (tire contact patch), and a line drawn though the fork steerer tube axis.

As forces on the tire contact patch build with speed, positive trail makes the front wheel want to turn away from the bike's direction of travel. This can make the bike extremely nervous at high speed and on rough surfaces.

Negative trail (contact patch behind the head tube axis line) causes the front wheel to want to align with the bike's direction of travel, adding a stabilizing force that increases with speed.

The fact that your legs are "attached" to the steering, providing a damping force to the steering system, can make Cruzbikes less sensitive to trail than a lot of other bikes, particularly at low speed. But once you get rolling quickly, like on a chipseal down hill road, you may find the bike hard to hold on line, particularly if you are trying to accelerate by pedaling down hill.

My advice would be to turn the fork back around.

Cheers,

Doug

 

[floridabike]

Thanks Doug,

That all seems logical. I do like the 26" wheels with the softer ride and now to deal with the brake issue. Hills are something I don't have here in Florida so my max speed is about 18 mph because regardless of the direction I'm traveling I always have a head wind, or it seems that way.

Thanks,

Phil

 

[billyk]

dumb question

I know about trail, but why should the trail on a conversion be any different with the driving wheel on the front than it was on the previous free-spinning front wheel? With the fork in the original direction, isn't the axle in the exact same place as on the original bike? Namely the trail should also be the same. What am I missing?

And speaking of trail, what is the trail on a Quest 2.0? I realize this depends on the tire size (larger tires decrease the head angle and thereby increase the trail), but say with the stock tires.

Thanks ... Billy K

 

[Doug Burton]

Turning the fork restores the original trail...

... because the triangle brackets have to move the axle forward to allow space for the cassette ahead of the fork legs. This distance is about 86mm, depending (for conversions) on where in the axle slot you place the axle (which restores the average 43mm of racke most forks operate with). We don't recommend running the axle at the rear limit of the slot, because the cassette can interefere with the fork leg or the chain may catch on the triangle bracket when shifting into the small cog. This also can cause the triangle bracket to bend if you hit a particularly nasty bump.

Most of our bikes use about 2 inches of trail, (although they're fairly insensitive to trail dimension as long as it's positive - tire contact patch behind the steering axis).

Trail dimension can change depending on the rear shock preload, which affects the headtube angle. The target headtube angle with the suspension loaded is 72 degrees.