humancannonball

I've got a first gen, 2012, Surly Krampus. I bought it back in 2014. It's an awesome bike, but some components are starting to show their age, and I'm wanting to breathe a little life back into it. I'm wanting to upgrade the cranks, but am having trouble determining what cranks will work with the rear hub's chainline. I'm running a Surly Ultra New Hub with a White Industries freewheel. Does anyone know if this has the traditional 47.5mm chainline? Or, as is common with Surly stuff, is it something slightly different?
Thanks in advance.

Kapusta

Did you check out the FAQ on this page?

https://surlybikes.com/parts/ultra_new_hubs

humancannonball

Yeah, I had a look at that page, but it seems like the 53.5mm chainline listed for the 135mm MTB hub isn't the traditional 47.5mm. I wasn't sure if the hubs being manufactured now are different specs than the one I have which is about 10 years old, so I can't be sure they're the same. I sent a message to Surly directly, but haven't heard back. And I also posted a question on that same page as your link, and it's not been answered yet (and may never be I fear). I also looked in the archived Surly catalog from 2012, the first year the Ultra New Hubs were manufactured, and there's no description of chainline inside. I'd post the URL for the catalog here, but Bike Forums won't let me because I've not posted 10 times on the site yet. Anyways, it's in the Surly Memory Hole, and if you're interested in looking, it's on page 22 of the 2012 catalog.
I'm just looking for that definitive answer so I can be sure to order the correct cranks.

Polaris OBark

What is relevant is if the crankset is boost. 135mm hubs are quick-release and by definition are not boost. 142 mm hubs are actually the same width, but thru-axle, and are also by definition not boost. If it is 148mm, then you have boost and need the boot-specific chainline. The cassette will occupy the same spatial position, so the chainline only has meaning in the context of the crankset. I would think any non-boost crankset with a chainring that fits the frame will work.

humancannonball

Ok, I feel like this is pointing me in the right direction. The main issue for me is that I'm running a freewheel, not a cog on a freehub body. If I were using a freehub with a cog, I could just arrange the spacers to give me whatever chainline I want, but as it is, the freewheel cog is where it is. I was also just a bit nervous that Surly's hub might not be the same as most others because, well... Surly. They just do quirky stuff (which I usually like by the way).

So according to your reasoning, a modern, non-boost, 1x crank should, more or less, line up with my rear freewheel cog? What I really want to use is a spiderless crank with a direct mount chainring. So I won't have the latitude of shifting the chainline by moving the chainring side to side using spacers or by changing it's position on either side of the spider.

Polaris OBark

I just assumed you had a cassette and "freewheel" wasn't literally accurate. But if it is, then I really don't know. But, I would still find it hard to imagine that a 135mm hub would be compatible with a boost crankset.

base2 

A boost crankset is going to move the chainring outboard by a few millimeters. Off the top of my head the chain ring ought to be ~50-53mm from the bikes centerline. A 1x boost single chainring is about the same place as the outboard ring of a non-boost triple.

humancannonball

Yup, a proper, old school freewheel. It's a first-gen Krampus from 2012. I bought it in around 2014. It's a fantastic bike for day rides (20 miles or less). I just want to update some components (like the square taper cranks in question... getting tired of having to sort out the creaking periodically). If money were no object, I'd just replace the freewheel with a cog/freehub combo, but having a new wheel built isn't really in my budget. So here I am trying to get as much assurance that whatever crank I decide to buy will work within the system as it is.

humancannonball

I did some more research, and it seems as if the chainring, not the cranks necessarily, determines whether it's boost or not (at least this seems to be the case with SRAM cranks specifically, I don't know about superboost cranks however). If I get a SRAM crankset with a 24mm diameter spindle and external bearings that takes a spiderless chainring, and then replace the boost chainring with a non-boost, 6mm offset chainring, then I might be good to go? I have a friend who's just volunteered to give me a spare, non-boost, Wolf Tooth Components SRAM direct mount chainring. That mated with whatever SRAM crankset I decide on seems like it might be worth trying.

seat_boy

If you have the frame and the wheel, just measure the chainline directly.

To measure the chainline at the rear of a bike, I do this:

1- take the rear spacing width and divide by 2 (135/2 = 67.5). (this is how far the axle locknut is the from the bike's centerline)
2- measure from the inner dropout face to the cog. Let's say that value is 15mm. (this is how far the cog is from the axle lock nut)

Subtract 2 from 1, and that's your chainline (67.5 - 15 = 52.5 in this made up example).

To measure it at the front, I just measure from the edge of the seat tube to the center of the chainring, and add half the seat tube diameter to that number.