A do it all 29er?
March 20th, 2007 by Tim GrahlLooking for thoughts on building a 29er that could do it all, I recently came across the GT Zum series of bikes and it got me thinking about the following:
- 29er frame
- Front suspension (with lockout)
- Disc Brakes
- Flat bars
- Compact Drive road crank or Road Triple
- MTB cluster in the back
- Two sets of disc rims, one for MTB tires, the other for road/cyclocross tires
I live in Des Moines, IA and we don’t have much for dirt hills. I think that the above setup would work for my commuting bike and the majority of MTB rides (or MTB rides on the way to work). I also think that the gearing would be enough for most road rides (unless in a paceline or with a tailwind).
What are your thoughts on such a setup? Other things to consider? Possible bike lines already out there?
– Tom
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Sound like a brilliant plan! Although, you might run into frame compatibility issues with a road crankset. In order to fit wider 29er tires, frame manufacturers have to spread out the chain stays near the BB shell quite a bit. This would result in the larger chain rings on a road crank to either hit the stays or be within mm of hitting them. Another possibility, since you desire a good mixture of larger gear ratios, would be to use a standard mountain crank, but go with larger rings. Salsa offers up to 48T outer rings and combined with a 36T inner ring you would have a crankset similar to ‘cross size. I know those rings sizes aren’t quite as big as a road crank, but throw on a road cassette and short-cage rear deralleur, and you would be pretty darn close to what you’re looking for. Good luck!
PAUL Thumies paired with Dura-Ace aero bar shifters will take care of the shifting needs.
This maybe a little off topic but I always think of it for something to concider. Why is it that both geared guys and single speeders instead of going smaller with their rear cassettes, they have a tendency of going bigger. Example, The norm for single speeders in the world is a 32t front matched to a 16, 18, or 20t rear depending on where you ride. Usually a ratio of around 2:1. Then i see that to go with a tougher gear alot of people change out the front ring to a 34 or a 36. You could keep that 32 ring and go down to a 15 or a 14t and get the same result with less weight. Street BMXers have done this for years. Even my Single Speed 29er now im running a Microdrive Seteup with a gear 22t matched to an 11t in the back, not only does it look sweet as hell but it also saves weight and keeps the chain ottadaway if you feel the urge for a pedal grind. For geared bikes i know its a little different because you can only go so small on a cassette, but has anyone tried running a road cassette matched with a short cage derraileur, it works pretty damn fantastic.
Just some thoughts
crush me if you feel the need to
-Matty
Wow i should read through entire comments sometimes, Levin pretty much nailed it with the road cassette and short der.
Matty, Small rings and cogs add drag to the drivetrain. Not a big deal for a BMXer but it is if you are pedaling steadily for an hour or more.
A big(ger) ring and cog combo feels smoother and easier to turn, reduces wear on the drivetrain and is less likely to drop the chain.
I use a 30 x 19 or 20 on my 29er and consider that to be small gears. Using a 38×23 on my 26″ bike.
There is no way in the world I could run a 32 x 15 on the 26er, let alone the 29er, in my area.
Weird, ive never experienced any drag using the microsetup 22t/ 11t, the only time i do is when i put a rediculous amount of tesion on the chain. I rock a 2/1 setup only because i live in the midwest, and im pretty used to pushing big gears anyway, so it works perfect for me.
This has gone a little off topic here, but I will concur with Shiggy on the larger cogs idea.
One thing that also bears mentioning is that when you wear a small cog/ chainring set up out, the same amount of wear on a larger cog/ chainring set up still leaves you with a lot of miles in the tank. The reason is that the wear is occurring over a greater area, so the components last longer. Sometimes alot longer. If you ride regularly in poor conditions, or in alot of gritty dirt/ sand, this makes a big difference.
My personal favorite setup for gravel road single speeding is a 37t BMX chainring up front with a 18, 20, or 22 tooth freewheel out back, depending upon the lay of the land. This is on a Karate Monkey 29″er. On my Inbred I’m running a 34T X 18T set up. I also live in the Mid West and find these gears to be just peachy.
Also, for Tom: Why the two wheelsets? Unless changing tires is a hassle, you should be able to do what you want with a single wheelset, which would be a bit less expensive, as well. Nothing wrong with owning more than one wheelset, though. Ha ha! You should see my basement!
I think Tim’s reason for the duel wheel set comes down to weight and tire size. A cross tire is just an agressive road tire and you realy would not want to run a 700×28 on a normal wheelset designed for a 29er, It would just feel plain creepy and would be to heavy to go distance (century).
No matter how Tim sets up his wheels, chainrings and cassette the shifting needs to be able to work between mountain and road, hence the Paul Thumies mentioned above. With ratio, one thing to remember is that Salsa makes thier 1×9 29er, were the ratio is 1:1 with a 32×34 setup. As this site has stated in the past, stability while climbing is not an issue, and no matter what ratio you have, these bikes climb, its the legs that give out, I would worry more about chain stretch.
I do not think that a road chain would be strong enough to take the tourqe that is needed for mountain riding. I go through 2 SS chains weekly when I race and ride the steeps of Annendale. Another concern would be that if you pound that rock in the trail with a road ring it would probibly explode and leave you walking back to the car, have good protection with you.
I love my road bike as much as I love my Ventana SS, and with just being 4 months out of rotater cup surgery, I am currently coverting my SS into a 1×9. So I will be riding my 29er as a bastard road bike to work and back for training until my arm and leg strength return. unfortunately Tim road is road and mountain is mountain, I think cross breeding a 29 and a road bike would be like breding a Great Dane with achihuahua, you will need a lot of patience and determination to make it all work right but it can be done.
Tim, build it as you want, it is a 29er thats what is important.
CrMike: On the wheels: Use a road width rim for both intended purposes. Lots of 29″er riders are doing this already with good success.
On your other points: You have valid concerns for a very technical, mountainous area. However; Tim is in Des Moines, Iowa, so his idea bears merit for the intended riding style and terrain. As in anything concerning bicycles, what works for one may not necessarily even be a consideration for another.
The reason that I was thinking two wheelsets is one with a full time MTB tire and the other with a full time road tire (23) or cyclocross in the winter. If there is a rim that would handle both, then I’m just not aware.
Ted is correct that since I live in Des Moines, most of my riding is flat. I currently have a 26″ MTB and a road bike. My road riding no longer includes racing and road rides are usually less than 75 miles. Plus, as I get older, riding in the drops is not happening as much. I’d like a frame with the comfort of my MTB, but with the rolling ability of my road bike.
As for the dirt riding, on the MTB, I rarely find myself in my granny gear (locally). I would hope to find a gear range that would work for both off-road and for the majority of my road rides. If I had a 29er with road tires and a 48-50 in the front I should be good for most pave conditions. Swap out to the dirt treads with a 34 and it should be close as well. A triple would be even better.
Do I need to consider the change in gearing with respect to the change in tire size? Example, does a 34×16 feel the same in a 26 vs. a 29?
Thanks for all in the input.
Tom
CrMike,
There is no reason to use the Thumbies unless he wants bar-top thumb shifters. Any Shimano 9-speed shifter works with any Shimano derailleur and 9-spd cassette. You can use a “triple” front shifter with any front derailleur with 2 or 3 rings. too.
Rapidfire, Dual Control, road STI, it all works with the same derailleurs.
Tom, I have an excel-based gear calculator on my site (download here): http://mtbtires.com/tech/gear_calc.xls
Also has a speed and cadence calculator.
A 34×16 is a harder gear on a 29er than a 26″ bike. A full width 29″ knobby also raises the gearing significantly compared to a narrow 700C road tire.
I think with some careful figuring you can use the same gearing on and off road, especially if you use a triple.
Please correct me if I’m wrong but …. the spacing in road chainrings and mountain chainrings is different due to chain thickness. Shimano shift spacing is set to match either road or mountain and is incompatable with each other. The reason for the thumies and Dura-Ace shifters is that the although cassette spacing is the same on either set up it is the chainring spacing where shifter is able to be manualy positioned and compensate for the differances in the spacing.
CrMike: Tom, (Sorry if we got it wrong and called you Tim!) is going to be using a flat bar with a road crank, most likely. The issue with mountain vs road shifters on the crankset is not the chain, or chainrings, it’s with the shifters themselves and how much cable they pull. While it’s true that a mountain shifter won’t be perfect, it can work, (I’ve done it).
The issue causing the problem is the extreme difference in chainring sizes on a road triple. This is even a problem with road shifters designed to work with road triples to a slight degree. It’s the decision that Shimano made to have only three and a half index points that really threw a wrench in the works. Compare to a Campy set up, and the difference is quite clear. Anyway, there isn’t any need to fret.
Tom could get himself a road compatible RapidFire shifter pod for the left side. They are new for ‘07 and quite elegant looking, having alot of aluminum construction, much like a SRAM X-9 shifter pod. Your Paul idea would also work, and for that matter, Campy makes some killer flat bar stuff too.
If it’s cheap that you want, any old skool thumb shifter will do the job on the left side mated to your right side shifter of choice. Suntour XC-Expert thumbies show up on e-bay yet NOS and quite cheap. I believe some mail order based bike shops also sell Suntour left side thumbies yet, as well.
Another flat bar option for left side shifting would be a grip shift, with it’s micro indexed set up. That could be matched with a similar right side shifter for a balanced look.
And as far as the crankset, I would seriously consider a compact double road set up. Tom: You won’t be needing that granny, as you have surmised, so why have it at all? Your compact roadie crank can cover nearly the same ratios as a triple with less shifting woes and less weight. Give it some thought!
Thanks to everyone for their input. I’ll use all of the thoughts and ideas and check back in when complete. Time to start frame shopping…..
Tim-Tom,
I used to live in Des Moines. Back then there was Brown’s Woods and behind the Science Center to ride. BW got closed. What is there to ride currently?
In hindsight the ideal bike for Des Moines would be some type of ‘crosser with 38c-45c tires, since there are long stretches of pavement that turn into dirt road. The suspension fork is unnecessary since there is only one rock in town (unless it got moved) and the 29er wheels reduce impacts adequately for what is there. I’d say whatever you choose, keep it light and fast.
Sounds like a Slingshot folder would be a perfect choice. My 2(biased) cents worth. I just bought a Slingshot 29′er. Great on and off the road. I have run a wide ratio mountain cassette on my road bike for years with no problems. It works great with the road double and gets you uphill to boot!!