This is a quite common problem with larger tires. Stuff in the 2.4" + range frequently do that on bikes not built around chunky tires. This is why freeride and DH bikes and surly pugsleys with there massive 3.9" tires have wider bottom bracket shells of 83 or even 100mm vs the normal 68 or 73.
Chains hits tire - rear derailleur crooked?
This is driving me nuts. When I am in my smallest chainring (22T) and biggest rear cog (34T), my chain rubs my tire. When look at my rear derailleur, the bottom pulley is closer to the wheel than the upper pulley. I tried messing with the high/low adjusters to fix it with no luck. Derailleur is a a relatively new SRAM X-7 unit which replaced a X-9. It almost looks as if the X-7 cage is bent. Any ideas?
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Need to visit the LBS to get a handle on whats going on....that or post some pics. Could be derailleur or hanger
No, it is unavoidable with a big tire, 135mm rear hub, 8/9-speed cassette and a proper chainline.Vespasianus said:This is driving me nuts. When I am in my smallest chainring (22T) and biggest rear cog (34T), my chain rubs my tire. When look at my rear derailleur, the bottom pulley is closer to the wheel than the upper pulley. I tried messing with the high/low adjusters to fix it with no luck. Derailleur is a a relatively new SRAM X-7 unit which replaced a X-9. It almost looks as if the X-7 cage is bent. Any ideas?
Shimano has moved the chainline of there cranksets out ~5mm from what it should be to increase the tire/chain clearance, at the expense of drivetrain efficiency.
Thanks. I am running a 2.4" MK on a Titus ML but I think I was even getting it with a 2.1 Nevegal. Currently, I am running an old Octa-link XT crank (73 X 113). I wonder if I can move the crank out a bit and get a better chain line?
If it also happened with a 2.1 tire and you have a 73mm BB shell I would think you have an actual problem, likely the rear der hanger. May be possible to swap to saint cranks built for an 83mm shell and a saint front der and add BB spacers. I wouldnt run any thing but the recommended spacers or your front der isn't going to line up and you will have terrible shifts.
Thanks. I may just take it to the LBS and see what they think.bikerjay said:If it also happened with a 2.1 tire and you have a 73mm BB shell I would think you have an actual problem, likely the rear der hanger. May be possible to swap to saint cranks built for an 83mm shell and a saint front der and add BB spacers. I wouldnt run any thing but the recommended spacers or your front der isn't going to line up and you will have terrible shifts.
Uhhhh....
Sounds whacked to me.Vespasianus said:When look at my rear derailleur, the bottom pulley is closer to the wheel than the upper pulley.
Your crank likely has the more inboard chainline (which is technically the "right" one). I do not know if there is a longer spindle Octalink BB. If there is, it will increase the tire/chain clearance.Vespasianus said:Thanks. I am running a 2.4" MK on a Titus ML but I think I was even getting it with a 2.1 Nevegal. Currently, I am running an old Octa-link XT crank (73 X 113). I wonder if I can move the crank out a bit and get a better chain line?
Note that the chainline "issue" is when the clearance problem is on the top run of the chain. If the bottom run is hitting and the top is not, you have a bent RD and/or hanger.
When look at my rear derailleur said:A crooked derailleur could cause the bottom portion of the chain to hit the tire but not the top. The position of the top of the chain is located by the cassette and chain ring only.
It is the bottom and I guess it must be the RD. The hanger is new.shiggy said:Your crank likely has the more inboard chainline (which is technically the "right" one). I do not know if there is a longer spindle Octalink BB. If there is, it will increase the tire/chain clearance.
Note that the chainline "issue" is when the clearance problem is on the top run of the chain. If the bottom run is hitting and the top is not, you have a bent RD and/or hanger.
New does not guaranty straight.Vespasianus said:It is the bottom and I guess it must be the RD. The hanger is new.
Very true.shiggy said:New does not guaranty straight.
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