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Sram 7 speed on older Shimano cassette compatible?

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Sram 7 speed on older Shimano cassette compatible?

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Old 07-09-18, 09:42 AM
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draganm
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Sram 7 speed on older Shimano cassette compatible?

I have an older Shimano Deore rear Mt. bike wheel with shimano Cassette. My kid must have dropped the bike repeatedly on the drive side ( i think) and slowly bent in the Deore RD, eventually sending it into the spokes. So $83. later I have a new hanger, new Sram GX rear derailer, and new Sram XD 7 speed shifters on an Access AL frame. I specifically bought both SRAM shifters and RD for matching SRAM's 1:1 ratio and to have all new shifting parts
Everything went together well, I used the new cable and added all new housing, but cannot get the shifting correct. Bottom 4 or 5 gears are fine, but things seem to go awry as you go further up. Shifting 2 gears on 1-click of the shift lever at the top. So what should should be 2'nd largest is actually first(largest cog), and the last click on the shifter doesn't go because RD is correctly stopping at the limit screw.

Never seen this before, I put a new wheel on my other sons mt. bike with Sram PG-730 and grip shifters and everything dialed in really well, so this one is just weird. The beauty of 7-8 speed systems was the large spacing between cogs and the ease of of dialing in the shifts. No matter what I do with this system though it's acting like a 6 speed shifter on a 7 speed cassette? any advice greatly appreciated
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Old 07-09-18, 11:03 AM
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Did you check the derailleur hanger alignment?

The derailleur mounting bolt needs to be on the same plane as the cassette cogs. With 7-speed I've been pretty consistently successful just eyeballing the hanger into alignment.
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Old 07-09-18, 01:09 PM
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As @Retro Grouch said...

Anytime you have to replace a derailleur hanger, it is likely that the frame was also tweaked. The alignment needs to be checked, and likely tweaked.

Also check the frame for cracks - aluminum.....

If your kid is repeatedly dropping a bike on the left side, it is time to take away bike privileges until he/she learns some responsibility, and put them on Shank's Pony for awhile.
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Old 07-09-18, 03:32 PM
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Originally Posted by nfmisso View Post
If your kid is repeatedly dropping a bike on the left side, it is time to take away bike privileges until he/she learns some responsibility, and put them on Shank's Pony for awhile.
haha, no idea what a shank-pony is , but I don't know that he dropped it repeatedly, maybe a few times, but more than likely he leans it against walls and trees and it just rolls and then slides down. I think what it really needs is a kick stand

Originally Posted by Retro Grouch View Post
Did you check the derailleur hanger alignment?.
I did, it was a bit off a bit but I bent it back until the derailer cage is parallel to the cassette, did not make my problem better or worse though. This ones just really weird, never sen anything like it, almost like a manufacturing defect in the shifter. I'll undo the cable tonight and go thru the range to make sure the cable pull is equal on every index, don't know what else to try

BTW, anyone know the correct square taper bottom-bracket length for a Mt. Bike with a triple crank? I seem to recall buying the longest one available from the vendor stock, but the crank is still too far in. I would like to have all 3 rings available (instead of just top 2) for some trails we plan to do this summer. Edit: never mind, I found a chart on Shedlons site with deore cranks listed
http://www.sheldonbrown.com/bbsize.html#deore

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Old 07-11-18, 11:24 AM
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I want to try and figure out my crank chain-ring locations first so i know that's right before messing with RD function any further. My current cranks are really old Exage FC M500 and according to Sheldon's require a 121mm BB. I have a sealed 123mm long on there and cranks are way too far inboard, probably 3 to 4mm. Current Sram FD with With low-limit screw backed off completely and the FD only goes in enough to line-up on center ring,

Instead of trying to figure this out I just want to get a new set of new SRAM cranks and BB for $60. delivered. Based on what I could find, the SRAM S600 triple cranks with square taper call for a 113mm BB. Can anyone please confirm these 2 parts go together?

https://www.ebay.com/itm/SRAM-S600-T...s/391922060003
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https://www.ebay.com/itm/NEW-Shimano...m/172373046615
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Old 08-26-18, 04:37 PM
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so to warp up this one as well, (and to show that despite building many, many road bikes, Mt. bikes are a really different ball of wax), I finally got this issue resolved.

1) Problem one was the RD I bought did not have the necessary "chain wrap capacity" , it was medium cage and I thought this would suffice but really needed a long cage with at least 40 tooth capability. It was also a 10 speed capable RD, and the cage spacing was just too tight for a 7 speed cassette and limit screws are not well suited for 7 speed, so I got a brand new sRAM 7spd RD for $20. delivered. The 7speed stuff is not as fancy as the newer groups, jockey wheels are riveted in and there's a lot of composite construction, but for single track type riding I think it's fine.

2) it is not possible to really align the RD hanger by just eye-balling the Derailuer and it's even harder with the chain on because it creates more problems with your line-of-sight reference points. I'm going to buy the tool next time I need it, not cheap at $75. , but in a pinch remove the RD and install a 4 to 6 inch long 10mm bolt and cinch it down with a jam-nut. View the center-line of the bolt in relation to the center-line of your hub-axle both by looking straight down(with bike upside down) to see any twist and straight on from the back to see any bend inwards or outwards. Turns out mine was off by a little both ways,
Bike shifts and rides really nice now, 10 miles yesterday with 1K feet of climbing on rocky trails and some really steep parts with 13% grade, but bike ran perfectly.
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