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Too much resistance when shifting up

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Too much resistance when shifting up

Old 03-29-15, 05:50 PM
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blart
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Too much resistance when shifting up

Hey all,

I'm in the process of converting a mtb to drop bars and acquired a pair of suntour accushift 7 spd bar end shifters. I am using them in conjunction with a triple fd and a 6 spd rd. The derailleurs are low end SIS shifters from the late 80s. I have set the rd shifter to friction.

Everything was going great in the build but upon installing the shifter for the fd I noticed it takes an inordinate amount of force to shift up to the bigger chainrings. I can get close to the big chain ring but not quite there. I've tried adjusting the limit screws, the L limit seems perfect and the H limit won't loosen any further without becoming unscrewed.

I experience something similar on the rd. It takes a lot of force and I can only get through the 3 smallest of all 6 cogs on the freewheel.

I am using a cheap bell cable kit if it helps. I've got a few ideas but was wondering if anyone had any input as I proceeded.

Thanks
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Old 03-29-15, 06:52 PM
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Using cheap cables generally is not a great idea. The housings internally do not have very good lubricants if any at all, and the cables themselves are not manufactured to a high standard. Both of which can increase resistance felt when shifting. If it is the cables directly, I would imagine you are replacing the brake cables as well using the same materials. A good way to isolate that phenomenon is to see if the brake cables as well seem to actuate using an obscene or irregular amount of force. Also, mixing vintages of derailleurs and derailleurs often creates problems. For example, Shimano 105 5600 vs their 5700 or 5800 series road shifters use different pull ratios for braking as well as shifting. If the ratios do not mesh well with the designs taken into consideration during the development of the derailleurs, then they will not function properly, let alone feel like it takes a lot of force to actuate them.

When adjusting the front derailleur limits, loosen the cable completely and move it by hand to see if it reaches far enough. It should be just avoiding the chain when on the lower ring as well as the larger chainring. If it can do that without the cable adjusted, then there is something wrong with the cable tension. If the pull ratios do not match with regards to the shifters to the derailleurs, then the front derailleur will not move as much as intended. For example, if the derailleur is designed to move X amount, and the shifter cannot provide that, then the system simply will not work.
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Old 03-29-15, 10:28 PM
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Andrew R Stewart 
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One factor not yet mentioned is that as the front der goes through it's range shifting to the big ring the geometry of the cable pull and the cage movement often falls changes for the "worse". So more lever movement is needed for lessening cage travel. Just look at the angle of the cable as it acts on the der's anchor bolt arm and how that cable angle changes as the cage move further outward. There are combos of chain line, chain ring number and tooth count, front der model, shift lever, cable routing and cable casing that worsen the resulting performance. This is but another example of why front der set up is not a black and white process. Andy.
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Old 03-29-15, 11:02 PM
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Many front MTB derailleurs matching the description you've offered have a little tab that kinda looks like should have a cable going under it but the cable actually needs to go over the top of the little tab. That should make upshifts much easier but I doubt you'll get it up to the big ring if the derailleur isn't designed to go that far out from the centerline of the bike. I once modified a Campagnolo Mirage derailleur to reach out a little further by removing some material with a dremel, but I dunno if that would work in this case. If there is plenty of chainring clearance from the chainstay then you could consider getting a shorter spindle BB.

Ideally you'd get a road triple with a road front derailleur, seems like that setup would be more likely for a BarCon to hit all three rings.

Last edited by LesterOfPuppets; 03-29-15 at 11:06 PM.
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Old 03-30-15, 07:12 PM
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My original instincts appear to have been correct, though I appreciate all of the replies.

I tried some NOS suntour housing and cable that came with the shifters and they made a world of difference. I have some more housing (Shimano SIS) that looks similar. Both are much thinner and stiff than the housing that came in the Bell kit. Anyway, I figure either would have had worked but the suntour housing works great so I'll just leave it for now.

I'm still having trouble getting into the big chainring but I figure with alittle tweaking it will get there. The resistance is gone, however- and I can get through all cogs on the freewheel.
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Old 03-30-15, 09:00 PM
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Thanks much for the update. Andy.
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