Gearing question with 1 x 12 or 2 x 11 geartrain

[slowtour]

I am organising a Jones Plus build - 29+ wheels on 3" tyres on a Boost frame. The standard gearing quoted is SRAM GX 1x12 with 32 front and 10-50 rear cassette. This comes to 19.51 gear inches. My current bike, a Surly LHT has Shimano XT triple 3 x 9 with 22/32/44 front and 11-36 rear and gear inches of 15.99. Since I am an "older gentleman" with "used" knees who tours long distances, I use the lowest gear on the LHT rather a lot and I would miss these lower gears on another bike. I won't miss the upper gearing as I rarely use the top gears. I will go back to Jones company to discuss but wanted a better idea of what might be possible before going back to them.

My question is - with a Boost frame - is it possible to successfully fit a smaller front cog for the front chainwheel on a SRAM 12 speed? About 26 teeth would give me about the right gear inches.

OR is it possible to get a 2 x 11 speed combination that will give me something like 16 gear inches that would be compatible? Searching the net some seem to get closer but even the 2x speed set ups like Shimano XT M8000 stop at front 24/34 and rear 11-42 which isn't as low as I would like.

[Duck!]

There will be some smaller chainring options available, at least down to 28T; 26 I am not sure about.

[RonK]

I'm in the same boat as you, and I'm using 2x10 (2x11 wasn't yet available).

So my setup is SRAM GX using 36/22 chainrings with an 11-36 cassette.

I'm not sure about your current gearing. According to Sheldon Brown's gear calculator, this yields 16.9 gear inches with 29 x 2.1" tyres. If you are going Plus size tyres then it will be higher.

I did consider a 1x arrangement, but considered the gear range too narrow to have a the low gear I wanted and still have a reasonable high gear.

The best person to ask what will fit a Jones frame is Jones himself.

[slowtour]

Thanks Duck and Ronk for your replies. Ronk - I forgot to note that my Surly is 26" (not 29") - hence the gear inches that I quoted in my initial post. Yes I expect that Jones will have a good idea of an alternative drivetrain. In our last conversation Jeff Jones wasn't conversant with the pricing of various different gear trains so I thought that if I had a better idea of compatible alternatives, I could select one that best fits my budget before calling back to discuss further. Still hunting for a 26 teeth chainring that would be compatible with 1x12 boost...or similar. Thanks again.

[RonK]

Well, have a read through this thread. Jone Plus build. This setup might work for you.

[slowtour]

Yep, thanks Ronk, I am already on this thread and they have been helpful also.

[Rodgerbiltit]

G'day slowtour,

https://www.wolftoothcomponents.com/col ... indle-bb30

My son has one of these (or similar) on his Hunt 1 x 11 - perhaps it might suit what you are considering? They go as low as 24T.

Not sure about the Jones bottom bracket set-up tho...

[slowtour]

Thanks Rogerbuiltit for the practical example - this is exactly what I was thinking of. It looks very possible. I will ask Jeff Jones if it is compatible. You must have real mechanical knowledge I am thinking. Thanks muchly.

[Duck!]

On the Shimano 2x11 track, while theoretically out of spec (Shimano tend to be very rigid in their setup thoughts and suggestions, and largely ignore the available compromises in trading off cassette and chainring ranges within derailleur capacity), you can run an 11-46 cassette (which they say is only for 1x) in a 2x system, with the use of a long-cage (theoretically for 3x) rear derailleur. There are from memory three options of 2x chainring combinations, all with a 10T difference, and 24, 26 & 28T small ring.

There is of course the 3x11 option, which will bring you down to a 22T small ring up front (30 & 40T for the middle and big rings), but officially at least limited to the 40T sprocket on the back. It may be possible to push the system to the 42T on the back, but how tolerant of this I do not know.

[slowtour]

Thanks for the information Duck, there seem to be some interesting options out there. Not sure about the 3x option & whether that will work with the 3" tyres and Boost frame. I recently read something about issues with chain lines and rubbing those big tyres. There does however appear to be real possibility with the 2x as Shimano and SRAM appear to make Boost versions. I have sent an email to Jeff Jones asking about using the Wolftooth front with a 24 or 36 tooth - and the SRAM 1x12 (10-50 cassette). If this works it will give me the low gearing I am looking for. Still it is good to look at all the options out there.

Incidentally the frame is meant to be suitable for 29x 3.25 inch tyres on the back (and even wider on the front) but this size has currently disappeared from the market. Hoping this option will return but happy enough to try the 3" tyres that come as standard. Pretty sure I am just being greedy looking for 3.25" but what the hell ha ha.

I will let everyone know when I get a result.

Thanks again for the reply and the information.

[baabaa]

Maybe worth putting the question up here as well?
http://forums.mtbr.com/custom-builders- ... 06728.html
People do and get away with some weird setup and some things that the builders/ bike companies sometimes wouldn't have even considered. I agree that the chainline should be you key focus with boost frame.
For me I tried 1 X 10 but on a 11 speed hub and found the chain noise from having to "bend" across the width of a 135mm hub plus the wide gear ratio a bit disturbing. Went back to single speed on that bike and not really that rushed to go now go 1 X 10 or 11 on my other bikes so will stick with the luddite front chain mover system thing for now.