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200lb rider with cassette flex problems?(14 posts)

200lb rider with cassette flex problems?KECHINBO
Feb 20, 2002 5:03 AM
I just upgraded from 8 to 9 speed and now, with the same frame and wheelset, the bike shifts on its own, especially when I'm out of the saddle hammering or climbing. Could it be that the cassette is flexing just enough for the chain to hop to another gear? Technically speaking, the 8 speed could have flexed the same amount but not hopped a gear because of the wider spacing, wider chain and greater room for error. I'm getting to the point where I'm ready to give up and go back to 8 speed. I'm running all 105 stuff...without paying 75 bucks for a DA cassette, what's a strong, zero flex cassette?
Not possible,TJeanloz
Feb 20, 2002 5:44 AM
No, you are not flexing your cassette. You need to have your rear derrailluer professionally adjusted- pay particular attention to the little piece of housing between the chainstay and the rear derailluer.

The forces and dimensions are such that there is no way you could be flexing the cog.
probably frame flexDrD
Feb 20, 2002 6:20 AM
Doubtful that the cassette is flexing (one could argue that the 105 cassette is actually as strong, if not stronger, than the DA one...) - more than likely, you are getting frame flex at the BB which is causing the ghost shifting you are experiencing (I am a larger rider myself (6'3", 210lbs) and have had frames which flex quite a bit while sprinting or climbing out of the saddle - specifically an 853 Schwinn and an 853 Lemond - never had any ghost shifting, though - the Schwinn had Ultegra 9spd, and the Lemond 105 9spd.)

I agree with the other poster that your deraileurs may be a tad out of adjustment, esp. if you see this more at the ends of the cassette than in the middle.
Feb 20, 2002 6:50 AM
Sounds like it could be a simple as a cable tension adjustment. Try the barrel adjuster? When it does the "automatic" shift, if it goes to a smaller cog, add tension with a counter-clockwise 1/2 turn, ride the bike, adjust further if needed.
flexing cassettediggler
Feb 20, 2002 7:16 AM
that's AWESOME!!!! try giving your derailleur adjusting screw a 1/4 turn. People really don't understand bikes, do they?
Feb 20, 2002 8:15 AM
You are NOT flexing your cassette. Get your derail/shifters etc checked out.
See how that "upgrade" worked miracles for you?cory
Feb 20, 2002 8:28 AM
JeeZUZ! I never saw anything wrong with FIVE speeds, and six seemed like luxury. My first real mountain bike would grind up sagebrush in the derailleur and still shift fine. Now you need a riding mechanic to keep your nine-speed working.
Manufacturer's argument$$
Feb 20, 2002 9:02 AM
The more gears you have, the better the chance of one of them working properly....
shut yer hole!!!nm
Feb 16, 2002 3:31 PM
Feb 20, 2002 10:26 AM
re: 200lb rider with cassette flex problems?KECHINBO
Feb 21, 2002 4:59 AM
Thanks to all who responded...even those who digressed to the puerile, yet entertaining exchange at the end. I had also suspected that the rear derailleur hanger could be bent slightly....not enough to see with the eye but enough to make a difference. Unfortunately I don't own the $150 tool to professionally check that and I live on a tropical island with 3 bike shops, all of which make there primary business by patching tubes on childrens and old ladies bikes. Back to the drawing board....Thanks again for the ideas
re:re: 200lb rider with cassette flex problems?vale
Feb 21, 2002 2:25 PM
Don't know if it's gonna help you any further but i have this problem with my cromo frame+7 spd casette. Actually there should be a combined effect of frame flex and rear derailler adjustment. If you have problems on every sprocket try rear derailler adjustment via the lil' screw on the back. Since i experienced this problem only on the 2 smallest sprocket I adjusted the gear spacing between the 5-6 sprocket (added extra 1/2 mm spacing ring)This din't make the shifting from 7 to 6 any worse (surprisingly)
re: 200lb rider with cassette flex problems?curlybike
Feb 21, 2002 4:33 PM
It is most likely that it is frame flex as someone else suggested. The extreme power you can exert as a large person, causes the BB to flex to the side, effectively lengthening annd shortening the der. cable pathline. When it gets shorter the spring in the der. causes the shift to occur. That is why the cassette is noisy after the mystery shift, it is isn't it?
re: 200lb rider with cassette flex problems?kechinbo
Feb 22, 2002 5:27 AM
The whole "frame-flex" theory seems to be the most believable but I have a hard time accepting it because the frame in question is a Specialized M4. I have a Columbus SLX Lemond and a cheaper chromoly Maruichi, neither of which flex enough to cause this problem. This is however my first 9-speed. I just received the Sram PC-69, so I'm going to swap that for the stock Shimano chain I'm currently running and go thru the whole re alignment process, to include the trim adjustment that was recommended by several readers (that would be the adjustment I've never previously had reason to mess with). I've always had good luck with the Sram chains on my 8-speeds so maybe that'll help. Thanks again for the info.