The Piper

Hola, Just picked up a Kona Big Unit Scandium frame to build for the up coming warmer season (some light trail riding). Never built a MTB before. Currently picking out parts for the build and I have a few questions:

1) How is this frame in general? I'm around 240lbs (Probably going to lose 20+ lbs.)
2) I want to go Sram Eagle (X01 or XX1) but having a few problems with which crankset and BB version (Dub, Fat, Boost etc.) to purchase.
3) What's a good wheelset? What to look out for? Thru axles, Boost? (Sub 500$)
4) How to find out what's the largest fork I can use?
There might be a few more but this is what I can think of for now.
Thanks!

Russ Roth

What year frame matters a lot to your question, what is it designed for?
1. Its a Kona, they make nice moutain bikes that are sturdy and designed to great off road geometry, you won't go wrong with it..
2/3 Boost BB, boost hubs/thru axle will all be dependent on the frame and nothing to do with what is better. Figure out what fits first
4. Whatever kona speccd the bike with is about right.

grubetown

Kona’s website and Jenson seem to have info about your frame if it’s the 2016. This will help with some of your questions and narrow down your options to get our thoughts on more specific details.

Kapusta

Like others have said, start with answering questions about the frame. The frame will determine what rear. axle standard and hub width you need. The fork will determine that for the front wheel. Frame will determine the type of bottom bracket, the rear wheel spacing might affect the actual crank and/or rings you pick.

Also, the frame most likely has a tapered head tube, but if it is a used frame, check to verify before buying a fork.

The Piper

Appreciate the replies! The website specs KONAWORLD

qclabrat

as others have said it's a 2016, between the Kona site and Jensen, you'll get the specs
First of all it's not boost, its a 142mm rear, nothing wrong with that, many of my bikes are 142 but no many are using that standard for MTBs
Bikeradar demo'd a bike with 80mm travel but 100mm may work, just do your homework
https://www.bikeradar.com/reviews/bi...g-unit-review/

Getting a set of $500 wheels with either SRAM X01 or XX1 components seem wrong, XX1 is $1500 for the group, I'd rather get $1500 wheels and go with GX eagle
The frame was $650 new, and the geo is already a bit dated, I'd be cautious throwing $2-3K on it unless it's the perfect frame.
It's actually an awesome frame for singlespeed with the sliding dropouts, tho I know it's not for everyone
Good luck and let us know how you make out

Kapusta

The model you linked to is the 2013 model. Is this correct?. It does not say specifically, but it LOOKS like it has a 135mm QR rear dropouts. If so, you will need a rear wheel with a 135mm QR hub.

But more importantly, it also looks like it has single speed-specific sliding rear dropouts.... no derailleur hanger.... so you can't run a rear derailleur. If this is indeed what you have, you will need to see if you can replace those sliding dropouts with the ones with a RD hangar. It appears to have a front derailleur mount, as well as all the cable guides for a FD and RD, so it was clearly meant to have the option to run it geared, so they must have sold derailleur-compatible dropouts for it. You might check to see if the ones from the Raijin of the same year will fit (and if they are available), or see if the 142 dropouts on the 2016 Big Unit will work. Or something else.

It also LOOKS like a tapered head tube. And LOOKS to have a standard 73mm threaded BB.

I don't see much useful info on that page in terms of what length fork it is meant for, but I would guess it is the same as the Unit complete bike of that year.

qclabrat

good catch
Seems like the built versions are all SS
Here's an aftermarket source for a dropout which should work, tho its not in the US
https://www.elanusparts.com/deraille...anger-for-kona
Don't think they are Paragon, but you can check with Kona to be sure

qclabrat

looks like does have the dropouts if your's don't have the right ones
Hangers & Dropouts: Dropout CC | KONA PARTS

The Piper

It is a 2013 model. My sliding dropouts definitely have a derailleur hanger. The plan is to use GX derailleur, shifter and either X01 or XX1 cranks. I can always either sell the components or use them on a newer frame(which is what I'm planing to do). Are all BB treads the same with the MTB? I usually ride fixed/single or road and some of those frames have different BB threads. Are there different size thru axles diameters or are just the lengths are different? How to know what Sram crank/bb to match up with?

I believe this build Kona Big Unit - Singlespeed 29er Mountain Bike - Eddie's Bicycles and Hockey Equipment used a 140mm fork if i'm reading correctly. What about the geometry to look for when choosing a fork?

Kapusta

I think you should post a pic of your rear dropouts, because if they are not The ones in the picture for the 2013 model, then we can’t tell you what you have.

Or google “135 vs 142 rear spacing” with pictures and figure it out yourself. And double check by measuring the spacing.

If you do not own a set of digital calipers get one. They are cheap and will pay for themselves quickly.

Until then, we can’t tell you what rear hub you need.

I am 90% certain what you have is either 135 or 142, both of which would mean non-boost. But your dropouts are clearly not stock for a 2013 model, so you need to double check.

Regarding the fork and geo: it looks like this frame was made for a long time, and over time geo of models change. Without knowing what model year the bike with the 140mm shock was built on, it is hard to know it it was an appropriate length for your uses. Plus, just because someone did it, does not mean it works well. The fact that the 2013 frame has a ~70 def HA makes me very doubtful they had a 140mm fork in mind. Heck, the Unit complete bike came with a rigid fork.

Unfortunately, without knowing what length fork that a given geometry chart is based on, it is not very useful. There is really no way I can think of to reverse engineer the fork length from that geo chart.

Honestly, that product page for the 2013 is mostly useless.

qclabrat

I agree the Kona site is rather poor and missing basic info a user would be looking for.
Here's a 2012 which is outfitted as an XC. Check with Kona, but my guess is that they designed the bike for 100mm travel. You can go up or down 20mm but 40 may make the steer slow and the stack too high.
https://www.vitalmtb.com/product/gui.../Big-Unit,6945

The Piper

I measured the bottom bracket and it came out 73mm and the gap between the real dropouts around 145mm. I still want to make sure that I'm ordering the right components from Sram. I'm trying to understand dub, boost, bsa, fat4 bottom brackets and cranks. Which match up with which or does it matter?

Kapusta

Well that looks like a through axle. Question is what size.

Where exactly are you measuring the 145? There should be a shallow slot in each dropout where the hub slides in. You need to measure the width INCLUDING the slot. It will most likely be either 142mm or 148mm.

grubetown

Some preliminary searching leads me to believe that you have a 2009.

grubetown

scratch that - 2013
The colors are very similar.

The Piper

I'm trying to understand dub, boost, bsa, fat4 bottom brackets and cranks. Which match up with which or does it matter?

Kapusta

Read this about bottom brackets. You have a 73mm wide BSA BB shell (threaded shell)

Don't worry about "fat" anything, you don't have a fat bike. Don't worry about DUB, either, it is just another crank design. They will fit your bike with the right bottom bracket, but beyond that it is irrelevant to you at this point..

"Boost" simply means that the rear spacing is wider (148mm) than traditional standards. This pushed the cassette outboard by 3mm, so a "boost" chairing or crankset simply means that it is designed to have the chain-rings line of 3mm outboard of where a "standard" chainring would be. But we can't help you know whether you have a boost frame until you answer my question I asked in my last post about how you measured your frame.

hig4s

Is there a local IMBA or other mountain biking and trail maintenance group in your area? There is almost always someone that likes to wrench or that even works at a shop that is willing to help in those type of groups.

The Piper

Had my frame measured its 12x142 and 73mm for the BB. Still need my help choosing the crankset. The wheel I'm looking to get are NoTubes Flow MK3 any other suggestions? Been looking at the Truvativ Descendant Carbon 12-Speed Crankset is it any good what the difference between it and the X01 and XX1?


Will look into it. Thanks!

Kapusta

Deleted.

Kapusta

Flow MK3 is fine.
You should probably look for a non-boost crank, or at least one that can take a chain-ring for a non-boost chainline. Your frame is not boost.

The Piper

The TruVativ Descendant Carbon DUB Crankset I'm looking at is non boost. How would it compare to x01 and xx1 cranks?

Kapusta

How do the prices and weights compare?

The Piper

What's a good brake set up for a reasonable price?