[RBW] Rear Derailleur Capacity Limits
Greetings, I finally got my Bombadil going, I'm using a vintage Deore RD-MT60 http://www.velobase.com/velobase.com/ViewComponent.aspx?ID=3f73f16c-1a7e-46c5-ab73-f21755e71b08 The capacity is rated at 38t. I'm using a 24/36/48 and 13/32 FW for 43 total. The issue I'm having is when in the 24t ring, and either the 28 or 32t cog, the pulley wheels are too close to the cogs. When spinning forward, I don't notice it, but if I spin the pedal backwards, the pulleys make a grinding noise, as they are right up against the cogs. I have the angle screw at the max, but it helped only slightly with the 28t cog, but not the 32. My chain length is proper. Having this wide of range of gearing is new to me, so my first assumption is that I've exceeded the capacity of the RD. If anyone has an answer, I'd appreciate it. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Rear Derailleur Capacity Limits
on 7/28/10 10:47 AM, Garth at garth...@gmail.com wrote: > Greetings, I finally got my Bombadil going, I'm using a vintage > Deore RD-MT60 > http://www.velobase.com/velobase.com/ViewComponent.aspx?ID=3f73f16c-1a7e-46c5- > ab73-f21755e71b08 > > The capacity is rated at 38t. I'm using a 24/36/48 and 13/32 FW for 43 > total. The issue I'm having is when in the 24t ring, and either the 28 > or 32t cog, the pulley wheels are too close to the cogs. When spinning > forward, I don't notice it, but if I spin the pedal backwards, the > pulleys make a grinding noise, as they are right up against the cogs. > I have the angle screw at the max, but it helped only slightly with > the 28t cog, but not the 32. My chain length is proper. "Angle Screw" = B-Tension adjuster? http://www.sheldonbrown.com/gloss_ba-n.html You might have some play in the derailleur itself. The parrallelogram of a derailleur is held together by bushings, and so as they age and wear, they tend to twist a bit and not hold the full range of motion they once did. That derailleur is rated for 32 teeth max, so if it's having trouble with the 28 too, I'd suspect something wrong with the travel, rather than the B-Tension setting. At the time that derailleur was designed, mtb rear spacing was 130 mm. That changed to 135 (which you have on the Bombadil) in the early 90's. You can get a pretty good idea if you remove your chain and put the bike in the stand. Back off the limit screws and have someone shift the RD through its range and you view from aft of the bicycle (in a stand is best). Check the torque on the fixing bolt (mount bolt) for the derailleur. If the RD doesn't line up with the largest sprockets when shifted without a chain, then check your limit screws and your cable tension. I'd suspect that you are at the edge of range with that derailleur, so everything has to be set up right to start with. If the RD does line up, check it again with the chain installed and look for twisting in the cage or other signs of tired, worn bushings in the body. Hope that helps, - Jim more - http://www.sheldonbrown.com/derailer-adjustment.html -- Jim Edgar cyclofi...@earthlink.net Cyclofiend Bicycle Photo Galleries - http://www.cyclofiend.com Current Classics - Cross Bikes Singlespeed - Working Bikes Send In Your Photos! - Here's how: http://www.cyclofiend.com/guidelines -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Rear Derailleur Capacity Limits
You've exceeded the capacity of the derailleur. You said it was rated at 38t, and you have 43t total. The behavior you describe is expected. Well, expected by me. Other people may have differing ideas of how rear derailleur capacity is stated. The top left section of this page discusses it: http://www.sheldonbrown.com/derailleur.html On Wed, Jul 28, 2010 at 10:47 AM, Garth wrote: > Greetings, I finally got my Bombadil going, I'm using a vintage > Deore RD-MT60 > http://www.velobase.com/velobase.com/ViewComponent.aspx?ID=3f73f16c-1a7e-46c5-ab73-f21755e71b08 > > The capacity is rated at 38t. I'm using a 24/36/48 and 13/32 FW for 43 > total. The issue I'm having is when in the 24t ring, and either the 28 > or 32t cog, the pulley wheels are too close to the cogs. When spinning > forward, I don't notice it, but if I spin the pedal backwards, the > pulleys make a grinding noise, as they are right up against the cogs. > I have the angle screw at the max, but it helped only slightly with > the 28t cog, but not the 32. My chain length is proper. > > Having this wide of range of gearing is new to me, so my first > assumption is that I've exceeded the capacity of the RD. If anyone > has an answer, I'd appreciate it. > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to rbw-owners-bu...@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Rear Derailleur Capacity Limits
There is always the option, in addition to all other suggestions, of reversing the B screw to get some extra separation... That's what I did on the Bombadil first and now the Atlantis to be able to run a rear 12-36 with an XT Rapid Rise RD. René On 7/29/10, Garth wrote: > > Jim, I checked the RD travel with no chain on, and it hits the 28t cog > despite the B screw all the way in, at the highest tension. > > I'm not sure what value the Park Tool idea is though, as on my road > bike, the XT RD will hit the 32t cog with the chain off, but with the > chain on it's not too close, and it shifts fine. > > I'm using all 114 included links of a SRAM chain, BTW. As far as I > know, the Bombadil doesn't need longer than a stock chain. > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to rbw-owners-bu...@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > -- Sent from my mobile device -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Rear Derailleur Capacity Limits
If the jockey wheel is hitting the cog it's too close. Shortening the chain is IMO the main way of rotating the cage so the jockey wheel position os farther from the cog. Then you have to see if operation over the rest of the range is acceptable. If it's not, you might need a different dérailleur. A B screw adjustment might help. On Thursday, July 29, 2010, CycloFiend wrote: > on 7/28/10 6:09 PM, Angus at angusle...@sbcglobal.net wrote: > >> This must be "if Jim is wrong day" > > Y'know I'm wrong _every_ day. > In fact, I strive to be wrong every day. > Somedays I do six wrong things before breakfast... > >> By looking at the picture of the derailleur the upper pivot and upper >> jockey pulley are in different places. Look at the picture and >> imagine a shorter chain, it would rotate the cage counter-clockwise, >> pulling the upper jockey pulley away from the cog. > > I just keep thinking that the issue isn't really the overall chain length as > much as it is side load on the derailluer. My suggestion was to lessen > tension from the chain while the derailleur is at its most extended > position. > > I kinda lost track if the OP mentioned that he'd checked derailleur travel > with no chain installed (been workng/engineering today/this evening). If > the derailleur swings through the proper range without a chain, and keeps > enough spacing from the cogs, then it might be worth tweaking the chain > length to see if that helps. > > Should look like this - > http://www.parktool.com/images_inc/repair_help/der_llimit.gif > > from: > http://www.parktool.com/repair/readhowto.asp?id=64 > > > - J > > -- > Jim Edgar > cyclofi...@earthlink.net > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to rbw-owners-bu...@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > -- Ken Freeman Ann Arbor, MI USA -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
