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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 06-06-09, 11:46 AM   #1
karl_m
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Bianchi fork flex

Under what I consider normal braking the fork on my San Jose flexes visibly and under hard braking it does it so badly that the tire actually bounces off the ground on level pavement.

Has anyone else experienced this?

I bought the bike from a guy who got it as a commuter and then decided that the single-speed thing wasn't for him. It was in good condition, low miles and completely stock. The brakes are set up properly and the headset is in good shape with no indexing or lateral play.

I took it to the local dealer (Ozone Bikes) where one of the mechanics looked at it (but did not ride it), pronounced it fine and said I needed to "feather" the front brake and use more rear brake. I found this both amusing and insulting since he had not ridden the bike nor seen how I ride. It was also unhelpful.

Next I went to my regular shop (The Peddler). There one of the mechanics rode it, put it on a stand to check the brake set up, rode it again, put it back in the stand to disassemble, lube and reassemble the front brakes, rode it again and then recommended I replace the fork.
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Old 06-06-09, 12:53 PM   #2
PedallingATX
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hmm that's really weird. I don't like the guys at ozone much either. I think it's weird that you would need to replace the fork if there is nothing wrong w/ it visibly. I mean if it isn't bent or otherwise compromised, I don't see how this could be happening. It sounds to m
e like a headset problem but I don't know. Sometimes bike shop mechanics don't what they're talking about. I would double check all the headset parts and make sure something isn't missing or warped or anything.

In Austin, I find Bicycle Sport Shop to be the best shop as far as mechanics go. There is a guy named Jeremy there who is the only person I let work on my bikes.
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Old 06-06-09, 01:04 PM   #3
Raiden
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Could it be the wheel? I'd suggest loose brake calipers, but the mech already disassembled/reassembled them. You also said you've checked the headset.

A test: If you stand still, squeeze the front brake, and push the handlebars forward, what happens?

Also, it could be your position on the bike; if you sit back and hit the brake, you wont have a maximum amount of traction in front, and it could cause the front to skid/bounce. Additionally, though you may have felt insulted by the mech's comment about feathering, cantilever and V-brakes can have stopping power on-par with disc brakes. Braking like you would with road brakes (especially if you're on treaded tires) might cause your wheel to lock up and skid.

Just tossing ideas out there....
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Old 06-06-09, 05:33 PM   #4
karl_m
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What puzzles me most is that I've got another bike (Rawland Olaf) with the same brakes (Cane Creek SCX-5 w/ SCR-5 levers) and the braking behavior is totally different. The Olaf has Pacenti Quasi-Moto 2.0 tires and on road or off I can hit the brakes and it just stops. No fuss, no muss, no bother, and no fork flex or tire bounce. On the Bianchi with fairly gentle pressure from 10 mph up I can get the fork to flex over an inch.

BTW - I'm not running the original All Terrainasuarus tires. I swapped them for Rivendell Jack Brown 33s. which roll a lot faster and are very comfortable on pavement or hard-pack trails.
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Old 06-07-09, 01:20 AM   #5
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I just bought a Mercier Kilo TT used that came with only a front brake. I get the same effect when I brake and my LBS said it was from the fork flexing also. I think the solution is to get a stiffer fork and/or (in my case) a rear brake. Is the fork being too soft for a brake a common problem?
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