Ride On
Posts:537
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| 05/30/2015 06:07 AM |
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Guy 1s bike is having some minor shifting problems. Note minor. Guys 2 , our amateur mechanic offers to take a look for him. Night before another group ride Guy 1 brings bike to Guy 2. Guy 2 does some fiddling around and claims a fix.
Next day, group ride sprinting for city limit sign Guy 1s rear D some how miss shifts and does something that causes the rear D hanger to get shared off and rear D to go into his wheel spokes. He crashes, takes out 5 other guys.
Guy 2, also on the ride, goes "Wow that sucks"
No I am neither guy 1 or guy 2 but next time some guy asks me to take a look at his shifting problem, I think I'll pass. |
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huckleberry
Posts:824
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| 05/30/2015 12:36 PM |
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Guy #1 really has nobody to blame but himself - possibly can share a little with Guy #2.
Now if I am one of the 5 other guys, I am pissed at Guy #1 - for good reason.
An amateur mechanic is just that, amateur.
I would never trust my bike's mechanics to anyone other than myself, or a professionally trained and paid mechanic with a verifiable reputation. |
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Cosmic Kid
Posts:4209
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| 06/01/2015 09:17 AM |
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Well, correlation does not necessarily equate to causation....without knowing what Guy #2 actually did, it is hard to blame him.
Did he mess with the limit screws?
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| Just say "NO!" to WCP!!!!
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Gonzo Cyclist
Posts:568
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| 08/28/2015 10:21 AM |
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well, there's that, and then some racers doing their own work........
Had a guy one time crash in a crit one , was working on his bike the night before, forgot the screws that holds your brake pads in, pads eventually came out, dumbass took me and a bunch of other people out! Doh!!
It is hilarious to watch racers, even the pros sometimes trying figure out a simple wheel swap |
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zootracer
Posts:835
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| 08/28/2015 12:06 PM |
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| I'm an amateur mechanic to say the least. I do most of the work on my two bikes. Only thing I have not mastered is wheel building. On that note, it's getting to the point where I drop by my LBS, and I know more about bikes than the "pro mechanics". I'm just saying..... |
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Gonzo Cyclist
Posts:568
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| 08/28/2015 04:46 PM |
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well zoot, but your a very "Knowledgeable" amateur, and you know the workings of a bike, you would be amazed at some of the folks out there, the worst were the scientists from the National Labs......
The only thing the so called pros know better is all that weird new crap, new BB's, Headsets, electric shifting, etc....cause they have to |
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longslowdistance
Posts:2886
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| 08/28/2015 06:24 PM |
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Hey Zoot,
Former pretty good wheelbuilder here, now just a geezer pontificating:
Wheelbuilding is a science and an art. High volume and good rims are necessary . . . but not sufficient.
How many here have had wheels built so right that they never need truing?
Mike Curiak at http://lacemine29.com/ has built 3 pairs for me and they have been perfect.
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zootracer
Posts:835
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| 08/29/2015 06:37 PM |
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| One of the wrenches at my LBS used to work for Williams wheels. He built me a rear wheel using a Mavic OP 32 rim in 2013. I recently had to touch it up on my truing stand. Best wheel build ever. It has over 10,000 miles. |
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6ix
Posts:485
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| 08/31/2015 08:24 AM |
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OK, I need some feedback here to tell me if I'm crazy or not. Definitely not going to suggest I'm an expert mechanic by any stretch but I think I know a good bit, or at least enough to do most of my own wrenching. Not too proud to say I don't know something and need help though.
Rented a nice Tarmac while riding out in Boulder and Steamboat Springs last week. Just had to slap my pedals on, adjust the seatpost and lower the stem. They had 20mm of spacers under the stem so I simply flip-flopped everything and re-tightened accordingly.
The shop inspected the bike when I returned it and said I cracked the 5mm spacer I had on top of the stem directly under the top-cap. There wasn't any damage to the steerer or anything and I'm still a bit perplexed as to how that could have happened. Didn't put me in any danger. Then the mechanic said that I had moved to the stem too low and beyond the proper attachment point. Huh, what? It's a steerer tube!! The headset top-bearing race was never touched at all. Simple flip-flop of stem and spacers. These things are supposed to be adjustable. If they weren't they would have extended the head-tube higher and eliminated those spacers under the stem. I bit my tongue, apologized for fracturing the $1 spacer, thanked them for their services and left. Wasn't going to challenge it but I think he was wrong. |
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Cosmic Kid
Posts:4209
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| 08/31/2015 09:08 AM |
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Some steerer tubes / stem set-ups are designed to have the expander bolt system be centerned in the middle of the stem. If you moved the stem down 20mm, you may have placed the stem BELOW the expansion bolt in the steerer tube.
If that was the case, then you were basically clamping on a hollow tube vs. one that had a solid object in the middle for additional strength.
As for cracking a spacer....yeah, I'm calling BS on that. |
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| Just say "NO!" to WCP!!!!
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6ix
Posts:485
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| 08/31/2015 09:27 AM |
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Thanks CK. That explains a lot. The mechanic's explanation was correct and I was wrong! Whoops.
Was quite pleased with that Tarmac, surprisingly so. Significantly smoother than my Foil but that's to be expected since the Tarmac is aimed at being a stable, all-day road bike versus semi-aero road. Even the ghastly mechanical Ultegra 11 was good! |
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79pmooney
Posts:3189
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| 08/31/2015 09:27 AM |
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CK, could the expansion happening above the stem cause the steerer tube to bulge and the spacer to crack?
On a rental bike, a system that doesn't allow 2" of adjustment safely just using the provided spacers for a stem ought to have a huge warning on it. Or just plain be designed better. What 6ix did was what anyone who isn't a bike mechanic but versed in riding would do without thinking. Just like it would never occur to us old school guys that there could be a quill stem with a dangerous height BETWEEN the max height mark and slammed.
Ben |
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zootracer
Posts:835
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| 08/31/2015 09:40 AM |
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| was it a carbon spacer? |
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Cosmic Kid
Posts:4209
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| 08/31/2015 10:10 AM |
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Posted By 79 pmooney on 08/31/2015 09:27 AM
CK, could the expansion happening above the stem cause the steerer tube to bulge and the spacer to crack?
I kinda doubt it....that would indicate a dangerously thin steerer tube wall....carbon just doesn't "expand like that.
As for the rental bike accommodating that much stem adjustment, I'd lay that one at the feet of the shop. They should have walked him through it and said "Don't remove a bunch of spacers because the stem will be too low (below the expansion bolt)". |
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| Just say "NO!" to WCP!!!!
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79pmooney
Posts:3189
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| 08/31/2015 10:33 AM |
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CK, couldn't the spacers themselves be substantial enough to support the steerer to further the adjustment range, perhaps made specifically for rental bikes? Maybe with stem like clamps and bolts. Also so someone could purchase the bike and leave a pile of spacers up top until he knows what stem height he wants.
Ben |
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