bsurkan

I have a Trek Belleville with a 3-speed Shimano Nexus SG-3R40 freewheel hub (I hope I got that right!) with 36 spokes on a 700c wheel. To keep it from slipping, I tightened it too much and stripped the screw on the right-hand side of the hub (see picture).

From talking to the mechanics at Harris Cyclery, they suggest that I simply replace the entire wheel, despite the problem being only a stripped hub screw. I imagine that another option is to swap out the hub, but keep the rest of the wheel, though it would be my first wheel build, and I don't trust my skills in that camp.

Here is a picture. What should I do to get this back on the road? If I do have to replace the Hub/wheel, is there a recommended upgrade to this hub to avoid having this problem in future?

Can I just buy the replacement internal hub pieces and swap them out of the hub without disconnecting the hub shell from the rest of the wheel?



Stripped hub screw that makes it impossible to attach to frame.

JoeTBM 

I would try and find a donor hub with a good axle but I couldn't locate an internal parts diagram or disassembly/reassembly information but I did locate a youtube video on rebuilding, not for the faint of heart.


BTW the video got excellent reviews

https://bike.shimano.com/en-EU/produ...3/SG-3R40.html

User Manual - https://si.shimano.com/#/en/UM/38E0A
Dealer's Manual - https://si.shimano.com/#/en/DM/SG0005
Service instructions - https://si.shimano.com/#/en/SI/3R40E

JoeTBM 

Found the internal parts list page I was looking for

https://si.shimano.com/pdfs/ev/EV-SG...IM41-2985A.pdf

3 part numbers for the axle depending on length

Good luck

bsurkan

@JoeTBM, you are an angel! That video is GREAT, and definitely not for the faint of heart. That guy who created the video just to show people how to do it is a saint!

I think I'm going to try just buying a complete "guts" package and swap it out with the existing one. At that point, I can tinker with the old guts package to swap the axel in slow time.

One of the most important lessons for me in watching the video is knowing how much force to put into tightening each nut.

JoeTBM 

I thought he did a real good job with it , I did subscribe to his channel, I can't imagine he has a bad video out there. My only area of concern was clamping the axle into a vise without using something to protect the threads. I used something like this

https://www.amazon.com/GarMills-Magn...gateway&sr=8-4



Just make sure you get the proper length "guts package" for your axle length. Those part numbers are on the parts list as well (item 1).

JoeKahno

The video you linked was for the coaster brake version. There are some internal differences and the roller brake version is a little less complicated. This video is silent and I believe it's captioned in Russian but it shows the take down and reassembly in a very clear series of steps.

bsurkan

@JoeKahno, thanks for taking the time to provide guidance. All of the bike shops around me have told me to just replace the entire hub and wheel, but I have now decided to repair my hub myself thanks to the support I've received on this thread.

JoeKahno

Thanks!

One more tip. Any time you have to remove the roller brake, leave the nut a little loose when you put it back together. After you have the wheel back in the frame and the anti-rotation washer installed, swing the brake anchor around until it lines up with the frame bracket, then tighten the roller brake nut. Things weren't lining up for me and I thought I messed up something internal. I almost pulled the hub apart again before I figured it out.

harshbarj

I had that same bike for a few years. Nice bike, but lots of bad / cheap parts.

Hard to tell from the photo, but it's likely just a stripped nut. Try cleaning out the metal bits. The thread on shimano axles are hardened stainless and almost impossible to strip with stock hardware. If it's actually a stripped thread then you can look around for a replacement part. They should be inexpensive. If the wheel is still good I recommend replacing the internals. Building a new wheel + new hub is going to cost over $200. Amazon has one direct from shimano for a fair price. Keep your old internals for spare parts as they are simple to open and fix.
https://www.amazon.com/Shimano-SG-3R.../dp/B016MPFEW0

bsurkan

@harshbarj, you are absolutely correct that it is the nut rather than the axle that is stripped. It looked to be so clearly the axle that I hadn't cleaned off the shaved metal until you mentioned it. Where does one find higher quality nuts? I'll try asking at the bike shops near me, but if you have another suggestion of where I can buy one online, I welcome it. I'd prefer to upgrade from the OEM nut.
@JoeKahno, thank you for the tip. It turns out that I have the version of the hub without the roller brake. Is it safe to call it a freewheel hub?

bsurkan

I think I found one nut option on Amazon, though I believe it is the OEM quality:
https://www.amazon.com/dp/B07CKCVRVS/

WizardOfBoz

You may want to invest in a torque wrench with the money you saved not buying a guts kit. The specified tightening torque for the OEM nuts is 30 – 45 N·m (300 – 450 kgf·cm or 265-400 inch-lbf, or 22-33 ft-lbf ).

Make sure that you have and use the toothed washers. Sheldon Brown reminds us that there's a reason that wheel seating surfaces and washers are toothed - don't use smooth ones.

Good luck.

bsurkan

Alas, I'm the nut. I purchased a guts kit prior to realizing that it was only a nut problem . Is this a good choice for torque wrenches:
https://www.amazon.com/Venzo-Bicycle...dp/B00811WQT8/

AnkleWork

Looks like the "OEM quality" nut prevented damage to your axle (by design).

WizardOfBoz

I don't know about Venzo. I buy older, "vintage" US-made wrenches (Sturtevant-Richmont, Proto, and so forth) and then test/calibrate them. On first glance, this wrench looked like it had too small a handle for the higher torque ranges. And indeed it does. Only goes up to 24 Nm. For your nut, you'd likely want one that goes up to 45 or perhaps just a bit more (i.e. 50Nm). The range is 30-45 Nm. I suspect your new nuts will be in the same range. I'd start at, say, 35-38Nm, with the serrated washers, and see how that goes.

Perhaps others have experience with Venzo, or other torque wrenches can make a recommendation.

CliffordK

It may just be a standard bike nut. You could try your local bike co-op and see if you can find one that fits. No shipping and handling, just some time to try it out.

bsurkan

That is so true. Thank you for pointing that out. I have purchased another comparable nut to continue protecting my axle.

Dan Burkhart 

It is as standard as you get in this business. 3/8 x 26, 15mm over the wrench flats so the bell crank fits.

JoeKahno

+1 on buying OEM. I don't always agree with a manufacturers choices. Often the bean counters overrule the engineers. For the most part though they try to hit the best product for a particular price point.

harshbarj

I can tell you from having that bike you do want a flanged nut as in that link. Even then you can slowly pull the hub forward. I had the problem when climbing steep hills. That kind of dropout really does not suite a IGH.

JoeTBM 

Thanks for catching this and pointing out the difference.