Chainline / Shifting issues upgrade Santa Cruz 5010 V4

parnifel
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103
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10/15/2012
Location
CH
Edited Date/Time 6/16/2022 9:45pm
Hey everyone
Hope you guys can share a litte lght or experience on this topic.

I currently upgraded my wheelset to a SC Reserve 30 with Hope Pro 4 Hubs ( I used the Boost kit).
The Rear wheel due to the spacers did not need redishing and is dead centre!!

I am not 100% sure what the chainline is, but the current setup is a follows.
- Santa Cruz 5010 V4
- Shimano FC-M8100 Cranks with 1 Spacer on either side of the BB.
- Wolftoot Oval Chainring.
- Hub Hope Pro 4 with 10-51T Cassette / XT Deraillur Long.

I get that when you back pedal that the chain may fall off...just wondering what the chainline is (i'm assuming by this bike is 55mm)..should I be using the M8120 cranks which are ideal for a CL of 55mm or just stick with the M8100 which is used for 52.5mm?
Won't the M8120 push the chain more outwards, this making the shifting worse?

The way I see it, I either need to be pushing the crank more inwards of the cassette more outwards...

Any ideas or inputs will help.

Thanks guys.
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Ceecee
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4/26/2018
Location
Tucson, AZ US
6/15/2022 7:19am
Fall off the 51t? Fall off the chainring?

Mine is fine with 8100 crank and XT bb with one spacer on driveside, but cassette is only 45t, hub is 350, ring is round 32t, and chainstay is 432mm for size M frame.

8120 is not the answer. Presumably you've tried winding out the low limit on derailleur. How's the crank/chainstay clearance with the driveside bb spacer removed? Careful!
parnifel
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103
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10/15/2012
Location
CH
6/15/2022 12:03pm
@Ceecee, thanks for input regarding this topic.
Yes, falling off the 51T cog. The thing is, is if I remove all the spacers from the drive side…it gets really tight for my chainguide.
If made some photos so you guys can check out the chainline.
parnifel
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103
Joined
10/15/2012
Location
CH
6/15/2022 12:04pm



parnifel
Posts
103
Joined
10/15/2012
Location
CH
6/15/2022 11:46pm
..sent an email to Hope Tech this morning, maybe the solution is adding or removing a 2mm Barrel Spacer to the Hub - behind the Freehub body - this way the cassette will be moved more outwards.


The current spacer is 1mm thick
parnifel
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103
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10/15/2012
Location
CH
6/16/2022 12:38am
Just received an email from Hope's Tech Department..no way around this I'm afraid.
The only solution is to remove the drive side crank spacer to move the crank more inward toward the frame.

If I do this I will have to go without a chainguide.

Happy riding everyone.
6/16/2022 8:33am Edited Date/Time 6/16/2022 8:33am
That Hope Boost conversion kit adds 3mm to each side of a 142mm hub, so where your cassette is compared to a "true" boost hub is 3mm further inboard. So that's why you have a bad chainline – you're using a boost crank (52mm CL) on a non-boost drivetrain position, essentially. As you mention, using the 8120 crank would make things even worse (55mm CL).

The only way to improve the situation with what you have is to remove the 2.5mm spacer from the BB assembly, that'll move your whole drive-side crankarm inboard the same amount, thus giving you a ~49.5mm.

Alternatively, you could buy a non-boost, previous generation crank. SRAM non-boost 1x cranks were 49mm CL, Shimano were 50.4mm CL, IIRC. But bear in mind you'll need a Shimano HG+ compatible ring if you're using a HG+ chain – which can be kinda hard to find.
2
parnifel
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103
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10/15/2012
Location
CH
6/16/2022 11:08am
@NoahColorado - thanks for your help suggestions man. Thats exactly what I did this evening, I removed the spacers on the drive side and the CL is significantly better than before, pretty sure I‘ll run this setup for the summer and I think this way there won‘t be as much drivetrain wear and tear.
Parts these days aren’t always easy to find…
Thanks again!!!
6/16/2022 12:11pm
One other alternative is using a different offset chainring Superboost is 0, boost is 3mm and old 5mm offset
1
parnifel
Posts
103
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10/15/2012
Location
CH
6/16/2022 9:45pm
Thanks @mtbman99 - that was also an option I was looking into but Shimano Direct Mount Chaintings in 6mm Offset are pretty hard to come by, by removing the spacers I was able to get the CL I need and keep the costs down.
After all, i still have some spare Chainrings at home, which are all 3mm offset anyway.

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