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advice on cassette sought.

Original Post
Rokjox Teleski · · Boise, ID · Joined Sep 2015 · Points: 0

I have been learning about working on my bike.  The lesson hasn't gone too far.

I have a 2007 Spec. FSR stumpy with a XTR derailleur and an 11x34 gearset.  I found a good deal on a 12x36 and as I spend a lot more time pushing uphill than blastin downhill pedaling hard, I thought I might replace the heavily worn old set with the bigger gears.  

Unfortunately, I didn't like the angle and way that the jockey wheels on the cage sit on the top gear.  No clearance, it bumps along the chain slightly.  It would work, but its not elegant.  If the springs of the XTR would allow (force) the cage to sit rotated an inch further back, it would provide all the clearance and lift needed. (Wanted...)  I look on the web and I notice that many derailleurs have a higher tension setting that is usually left unused in factory sets, but can be changed by placing the associated spring into a second, anchor hole, leaving you with a stronger resistance to forward pull, I assume.

But the XTR doesn't have an obvious second hole for the anchor, that I could notice... so I took the whole thing to a local shop to see what they thought.  Am I clueless on how this is done?  ((well, yes I am, but...))

The local shop isn't the premier shop locally here, I guess... the mechanic seems to have not understood a thing I said... he put it together like I had tried, and with the same results, a crammed chain path.  He seemed to have no idea that the tension of a derailer might be changed or why, and he didn't seem to find the setup he had created had anything bad wrong.  MAybe it IS ok??   ((nawwww...))

I am changing the set back to the old gears, and will replace the cassette with an exact replacement part again later.

But am I missing something?  Is it possible;e to run the old XTR with the extra size gearing?   It kinda is too far for the chain tensioner, bottom gears are almost loose chain when used and top gears are ALMOST too tight; but a change in tensioner tension would allow the gizmo to take up the slack better also.

Do I just need a stronger spring, maybe available from a better source?  Or am I trying to reinvent the wheel?  Or trying to make an XTR derailler do something it can't?

I am just creating a lot of trouble for myself I guess.   Walking isn't the worst thing that can happen on a steep climb.

Brock Warner · · Boise, ID · Joined Nov 2014 · Points: 1,215

You can likely find a spec sheet for your derailleur by googling its model number, something like RD-M###.  This model number can usually be found on the back plate of the parallelogram of the derailleur.  If you're lucky and find the right spec sheet, it will tell you the Maximum Sprocket Size.  This is the largest tooth count your derailleur is designed to handle on the low gear of your cassette.  If your derailleur can't handle a 36T cassette you can try creative solutions (some people have tried using a longer B-tension screw) but remember your equipment has limitations.  As a 6 year professional mechanic, I can tell you these days I tend to just play it by the book.  Getting creative usually nets you halfway or temporary successes (in my experience).

The spring you are describing sounds most like the lower knuckle spring.  Yes, it can be moved to the secondary position but my understanding of this procedure is that it breathes new life into old derailleurs whose springs are worn out in the factory position and the cage can't properly tension a chain anymore.  It would not affect Max Sprocket Size; that has more to do with the inherit geometry of the derailleur.

If your XTR can't do the 36T and you really want it (I'm all with you on wanting lower gears) then my advice is to first see if you can get a new derailleur to accommodate the cassette, but that may be less-than-desirable depending on your current drivetrain.  Second, check out this:  It's designed for road bikes but I don't see why it wouldn't work in your situation.  Consult with your local shop first though ;)

Rokjox Teleski · · Boise, ID · Joined Sep 2015 · Points: 0

That is a GREAT answer to my post, thank you so much.  

Rokjox Teleski · · Boise, ID · Joined Sep 2015 · Points: 0

I thought I would do an update.

Eventually I junked the shimano xtr as worn out and underperforming and found an Alivio from somebody in China for like $20, with the "shadow" chain guide, a little longer path and kept close to the wheel.  Its FABULOUS.  with the 36 I crank the sharp uphill zigs without much effort where I used to get spit off.  I spent a lot of time on Ali express and I am ashamed.  I understand that they are using it to destroy capitalism and the American Merchantile Class, but the prices give me orgasms.  And who can resist that?

I replaced both complete wheel assemblies for $80 total with a set that is as good or better as the original Mavics that were on the Spec.FSR Expert originally.  The 12x36 rear gear cluster cost me about $20.   I got a gold chain with a outrageous promise of longevity for another 20, a set of really nice German produced leather grips with quick releases instead of clamps for $25 and a nashbar seat under $20 more with a CF (Raceface, China) seatpost for $18 more.  A set of Velociraptors for the rims for $36 (EVERYTHING gets free shipping!) and a 49 dollar Nashbar triple front crankset pretty much replaced everything I had beat to death over the 11 years I been riding the machine.  I let my LBS replace the BB with something from Tru Gigapipe and bolt up and adjust everything I had done.  That was 80 bucks including adjustments, they did pretty good.

I bought a new seatclamp, pretty enough for 3.5 dolla, slime tubes and somthing else, something, somethin, and a new set of aluminum Jockywheels just for the color... another 3 bucks gone forever...

Dudes, I rebuilt a worn out beater (except shocks) for abour $400 bucks including labor, parts and shipping.  Bike is awesome again, and I like the way its looking/working.

But I feel DIRTY.   I KNOW the Chinese are just taking advantage of me, they are out to destroy our way of life through "dumping" everything we want at prices we can afford and thereby taking away the jobs of every Markup Retailer in the nation!   THE EXISTENTIAL HORRORS OF COMPETITION!

I am spending as much of my badly retained earnings as I can with local producers of American Products to compensate.   Especially high priced Beer.  The extreme profits on beer may save our nation yet, if only we can add another 10,000 microbreweries to the Nations reserves.   Remember Video Parlors?  We now got more microbreweries than Video Parlors ever!  I expect they will have the same economic value eventually!

My bike cost nearly $3000 new.  Rebuilding it from conventially sourced store bought parts would have cost another $2000 anyway...

I am beginning to understand a lot about the costs of American Capitalism.   Businessmen seem to be impressing me a lot less and good bike mechanics a lot more.  

Guys, do I need to turn my spokes into Tebetian Prayer Wheels so that I may invoke Gods forgivness with a million prayers?  The little flags might look kinda cool....

Guideline #1: Don't be a jerk.

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