Can you correct IGH chainline offset issues by dishing wheels differently?

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argosnotch   1 µW

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Can you correct IGH chainline offset issues by dishing wheels differently?

Post by argosnotch » Mar 31 2021 4:15pm

I am researching adding a mid-drive to my IGH bike, and have been reading these forums for several weeks. One of things I need to nail down is getting the chainline correct (among 500 other things). My rear hub is an Alfine 8. If it's possible using spacers, can you simply move the hub further to the drive side (to add some offset), and dish the wheel to correct for this. I'm looking for ~5mm. Looking at the "stock" wheel building specs for the hub http://www.kstoerz.com/freespoke/hub/169, the flanges aren't centered anyway. Is this doable? It sure would make getting the chainline right easier.

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MadRhino   100 GW

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Re: Can you correct IGH chainline offset issues by dishing wheels differently?

Post by MadRhino » Mar 31 2021 5:54pm

This is only possible if the frame dropout width is wider than the hub. Then you can place the hub at the extreme drive side, space the other side with washers and dish the wheel to center it.
Make it fool-proof, and I will make a better fool.

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amberwolf   100 GW

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Re: Can you correct IGH chainline offset issues by dishing wheels differently?

Post by amberwolf » Mar 31 2021 6:00pm

Which specific middrive do you want to use? There are offset chainrings for some of them that could give you at least some, probably all, the distance you're after, without any ohter bike modification.

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Re: Can you correct IGH chainline offset issues by dishing wheels differently?

Post by argosnotch » Mar 31 2021 6:17pm

Still TBD on the mid-drives (considering BBS02, BBSHD, TSDZ2 so far). Lots of reading/researching done, but still more to go. FYI, my bike currently has a belt, and trying to figure out how to keep it if possible given the chain/belt-line tolerances of the belt. Switching to a chain might be the only option to reused the Alfine-8, but I've loved the last 10 years of a belt drive and it's hard to go back.

@madrhino I think I see what you're saying. I found a schematic of the IGH https://si.shimano.com/pdfs/ev/EV-SG-S501-2788C.pdfand mounting hardware. Looks like it fills up the whole 135mm between the drops. What I thought were spacers, are actually functional and needed.

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amberwolf   100 GW

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Re: Can you correct IGH chainline offset issues by dishing wheels differently?

Post by amberwolf » Mar 31 2021 6:52pm

argosnotch wrote:
Mar 31 2021 6:17pm
Still TBD on the mid-drives (considering BBS02, BBSHD, TSDZ2 so far). Lots of reading/researching done, but still more to go.
What specifically do you need the drive to do for you? What kind of terrain, wind, weight, riding style, etc? Some will be more suited to some uses. For instance, if you like to pedal hard, the TSDZ2 is a poor choice due to the circlip groove design they have on the hollow crankshaft, which tends to shear off due to stress fractures at that point. ;)
FYI, my bike currently has a belt, and trying to figure out how to keep it if possible given the chain/belt-line tolerances of the belt. Switching to a chain might be the only option to reused the Alfine-8, but I've loved the last 10 years of a belt drive and it's hard to go back.
Depending on the space available between the inboard side of the right crank, and the outboard face of the drive casing, and the diameter of the output belt sprocket, you may be able to use an offset mounting "tophat" adapter to connect it to the middrive output, and keep the beltline you have.

There are some threads around about the Gates belts in various middrives, if it helps (I havent' read most of them, so they may not be relevant):
search.php?keywords=gates+belt*&terms=a ... mit=Search

If it's not a Gates belt, let us know which it is and perhaps there is info around here about it.

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Re: Can you correct IGH chainline offset issues by dishing wheels differently?

Post by argosnotch » Apr 01 2021 11:34am

amberwolf wrote:
Mar 31 2021 6:52pm
What specifically do you need the drive to do for you? What kind of terrain, wind, weight, riding style, etc? Some will be more suited to some uses. For instance, if you like to pedal hard, the TSDZ2 is a poor choice due to the circlip groove design they have on the hollow crankshaft, which tends to shear off due to stress fractures at that point. ;)

Depending on the space available between the inboard side of the right crank, and the outboard face of the drive casing, and the diameter of the output belt sprocket, you may be able to use an offset mounting "tophat" adapter to connect it to the middrive output, and keep the beltline you have.

There are some threads around about the Gates belts in various mid-drives, if it helps (I havent' read most of them, so they may not be relevant)

If it's not a Gates belt, let us know which it is and perhaps there is info around here about it.
I haven't ridden in several years, but back then only rode occasionally, recreationally (3-4 times/month, 5-6 months per year). I live in Seattle, and had to stop riding because the hills became too much (age, injuries, and fitness level also related factors). As an example, I live at the top of a hill that's downhill in every direction. The least steep way back home after going for a ride is a 1.2 mile climb with a 450 foot elevation gain. Anytime I go biking, that's the end of the ride. Also, most places you bike to have you going up and down 200-300 foot hills to get there. I basically want to "flatten all these hills". I want to sometimes ride without putting in much effort to get up the hills, like the same effort as riding on the flats at 15 mph, or maybe sometimes even less. I don't want/need to peddle that hard.

Yes, bike has a Gates drive. I've read numerous threads on belt builds, so getting pretty familiar with all the issues that entails. I think I'm going to have to forget about using the Alfine 8 if I want to keep the belt. Looks like the thing that works is using the Sturmey Archer 3-speed hub that allows adjustment to the chainline using spacers. I'm wondering how having only 3 speeds narrow gear range would feel. Would I miss more gears? Would all the mid drive options still flatten the hills without being taxed, if I put the largest front sprocket made (like 60T) combined with the smallest rear (22T)?

Lastly, I have the older CDN system before the CDX system came out. I would also be updating to the CDX system. The new hub would require a new wheel (which I would also match on the front), which I would get larger than my current 32mm. The frame looks like it could handle 40mm. My brakes are lower end mechanical and I'd want to upgrade them too. I have priced all this out, but probably need to, and also consider an "off the shelf" bike too like the Priority Current. Not sure how to compare the 2 options really.

Just more to do and think about.

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