All these problems get solved so quickly if you just use a wider chainline...~10mm wider BB, offset chainstays ~5mm to drive side to get a dishless rear wheel with standard 135mm hub, stronger wheels, plenty of room for big tires, everyone wins except the people who nerd out about 10mm of Q factor.
Frame design
- Thread starter Ted Wojcik
- Start date
10mm wider - meaning an 83mm bottom bracket shell?
I don't think that the new XT crank/BB will allow that much more shell, but I'll take a look at how much of a shift that setup will take. I won't be able to take a look until this week and I'll be some what unavailable until after the holiday.
HAPPY THANKSGIVING !!
HAPPY THANKSGIVING !!
For shorter rides, I don't notice much change in q-factor, but when I'm looking at long days in the saddle (touring, solo 24 hour, etc) 10mm more on an already too wide crank is too much.
The new XT won't work with an 83mm shell. Truvativ and Race Face make ISIS BB for that size, and I beleive Phill Wood will make a 83mm sqaare taper BB up if you ask.
I'm not aware of any external BB Shimano cranks that work with an 83mm BB. Truvativ, Race Face and maybe a few others have soem DH oriented cranks that work, but this all seems to be getting away from the idea of an East Coast XC bike.
The Saint's are available in 83mm...not too heavy and sexy looking to boot.
But the point is moot...Ted is looking for realistic solutions to 29er problems on a trailbike for more than one person...this isn't a design exercise in what works best for an individual. Normal parts for a normal rider on a sweet frame.
Ted, what do you feel would be some good points for a 29er? I think Ted is likely more qualified to tell us what tends to work, whereas we can tell him what we like, what works for us and what doesn't.
I mean hell, I know I love how my 29er rides etc, but that is because Darrell and I fed some valid info into the computer that is FTW, and he gave us his interpretation of our data, in the form of 6061.
I respect what everyone here is saying and the ideas put forth but I think we start to micro-manage the whole thing.
But the point is moot...Ted is looking for realistic solutions to 29er problems on a trailbike for more than one person...this isn't a design exercise in what works best for an individual. Normal parts for a normal rider on a sweet frame.
Ted, what do you feel would be some good points for a 29er? I think Ted is likely more qualified to tell us what tends to work, whereas we can tell him what we like, what works for us and what doesn't.
I mean hell, I know I love how my 29er rides etc, but that is because Darrell and I fed some valid info into the computer that is FTW, and he gave us his interpretation of our data, in the form of 6061.
I respect what everyone here is saying and the ideas put forth but I think we start to micro-manage the whole thing.
My idea here is to make a 29er frame that rocks in New England Single Track. I want the frame to be light, quick, and be able to use components of the owners choice. Unfortunately, Shimano kinda' dictates the layout. We might find out that other parts will work the best, but I would prefer that any body's parts will work. How short do the chainstays need to be? How short are your's and are they too long? Why? It has been agreed upon that 29" wheels have better traction, so we might get away with something greater than sub 17". I will try to make the bike steer like the single track bike we all love, but I'm really looking for input on all the other feature the Monkees are looking for in the ideal 29er. I think an LX/XT/XTR crank is a good standard because of the popularity of Shimano parts and the 22" small ring is really needed with the big wheels. It would be good if the bike would suit a broad cross section of riders. The crank, front dérailleurs and.dropouts will be here this week, but with the holiday, I won't get to do much. I will tack together a chainstay, BB, seatube assembly and we will take a look at what we have to work with and settle on a rear triangle design.
Do you think that because sliding dropouts make the rear triangle smaller, that compliance is effected?
I would think that a CS @ or shorter than 17.25" would be worth doing. That would make it shorter than allmost all production bikes and most custom bikes as well. That is of course if you can get the FD to work. Otherwsie, just make them as short as will fit without having to get too creative with the ST junction and angle. Have we desided on a STA?
I would think that a CS @ or shorter than 17.25" would be worth doing. That would make it shorter than allmost all production bikes and most custom bikes as well. That is of course if you can get the FD to work. Otherwsie, just make them as short as will fit without having to get too creative with the ST junction and angle. Have we desided on a STA?
A few actual measurements of some stuff in the basement:
Bianchi Sok SS 08 17 1/4 74º
Raleigh XXIX SS 07 17 3/8 73º
Fisher Paragon 07 17 3/8 72º
Ventana Full-sus 18 1/4 74º
Custom steel SS 17 5/8 ?
Forgot to measure my KM at home but Surly lists it at:
Karate Monkey 17 73º
I haven't found any of these bikes particularly well suited to NE single track, although they all work just fine. I don't see any reason to go with super short chain stays for traction reasons, as all 29er's I've ridden can claw their way up almost anything with a minimum of technique compared to 26" bikes. The 26" bike I'm currently testing gets gobs of traction, but the rider needs to really use some technique to keep the front end from wandering and coming up on steep climbs. I have a feeling the longer chainstays and steeper seat angles used on many 29er"s make it a comparative no brainer to climb the steep loose stuff.
Personally though I'd give up some of the climbing ability to get a bit more playfulness in the bike. It takes a pretty solid pull to get the front end to come up for log piles and the like. The big wheels seem to require less lift to clear similar size obstacles as a 26", but I like the feel of a bike that wants to get up on it's rear wheel, something I think can be accomplished by a slacker seat angle, shorter chainstays and a higher BB.
This may not be what Ted has in mind of course, but when I think of an east coast single track hardtail, this is how I want it to ride.
Bianchi Sok SS 08 17 1/4 74º
Raleigh XXIX SS 07 17 3/8 73º
Fisher Paragon 07 17 3/8 72º
Ventana Full-sus 18 1/4 74º
Custom steel SS 17 5/8 ?
Forgot to measure my KM at home but Surly lists it at:
Karate Monkey 17 73º
I haven't found any of these bikes particularly well suited to NE single track, although they all work just fine. I don't see any reason to go with super short chain stays for traction reasons, as all 29er's I've ridden can claw their way up almost anything with a minimum of technique compared to 26" bikes. The 26" bike I'm currently testing gets gobs of traction, but the rider needs to really use some technique to keep the front end from wandering and coming up on steep climbs. I have a feeling the longer chainstays and steeper seat angles used on many 29er"s make it a comparative no brainer to climb the steep loose stuff.
Personally though I'd give up some of the climbing ability to get a bit more playfulness in the bike. It takes a pretty solid pull to get the front end to come up for log piles and the like. The big wheels seem to require less lift to clear similar size obstacles as a 26", but I like the feel of a bike that wants to get up on it's rear wheel, something I think can be accomplished by a slacker seat angle, shorter chainstays and a higher BB.
This may not be what Ted has in mind of course, but when I think of an east coast single track hardtail, this is how I want it to ride.
So are you saying you'd like a bike that would be a bit easier to manual, wheelie, loft the front end for playing on rocks and whatnot? A bike that was a tad bit easier to do small drops and to do wheelie drops and whatnot?
It doesn't matter whether the BB shell is wider or not, so long as the spindle length produces a 5mm wider chainline.
You don't even need weird parts. All Truvativ ISIS and square taper cranks, for instance, use a 113mm BB as standard, so all you need for the offset rear is a standard 68x122mm BB -- available from Shimano for about $20.
Yes, this means the XC cranks with integrated spindle won't work, because Shimano didn't want to add 10 extra grams and put a bolt on the drive side like BMX cranks use. As mentioned, you have to use Saints, ISIS, or square taper.
I don't personally think this is much of a sacrifice considering that it fixes all the other problems and uses standard, currently-available parts.
Note for the Q-factor nerds: external BB cranks are wide as hell. A set of Truvativs or Middleburns plus an extra 10mm is probably the same width as a set of new XTs. So I don't think the "too much extra Q" argument is necessarily true.
You don't even need weird parts. All Truvativ ISIS and square taper cranks, for instance, use a 113mm BB as standard, so all you need for the offset rear is a standard 68x122mm BB -- available from Shimano for about $20.
Yes, this means the XC cranks with integrated spindle won't work, because Shimano didn't want to add 10 extra grams and put a bolt on the drive side like BMX cranks use. As mentioned, you have to use Saints, ISIS, or square taper.
I don't personally think this is much of a sacrifice considering that it fixes all the other problems and uses standard, currently-available parts.
Note for the Q-factor nerds: external BB cranks are wide as hell. A set of Truvativs or Middleburns plus an extra 10mm is probably the same width as a set of new XTs. So I don't think the "too much extra Q" argument is necessarily true.
Ditto.I'm right there with ya sir!
A 29er that could pop up easy and roll would be unstoppable...
It appears that the Saint crank/BB system will solve some problems. I might be missing something, but I think that it will require the 150mm rear hub as well to keep the chainline as recommended. What this would mean is that if this frame design went into the market place, it would have to use Shimano Saint if we used up to date parts. Square taper cranks are in the same category as dinosaurs, I'm not a great fan of ISIS. Some manufactures did okay with it, but I have three cranks in the shop with a loose crankarm spindle interface. What is the general opinion on crank/BB selection? I have no problem with asymmetrical frame design, but I would like to keep component selection more versatile. Sooner of later, this frame will end up in somebody's hands that won't realize the design requires special components and then it will be said that Ted Wojcik builds his frames with bad alignment.
I'm in complete agreement that we can use avaliable parts to get the chainline you are looking for, but the idea here (at least as I'm interpreting it) is to use "standard" parts, not ones that will sooner rather than later stop bing supported by the major component makers.
Shimano has stopped production on the UN-7X series BB, the selection of ISIS is getting smaller, and I don't see the major's going back to 3 piece setups anytime soon.
For the record I think the newer external BB cranks are a pretty crappy solution to a problem created by ISIS and Octalink. Higher Q-factor, no real ability to adjust chainline, crappy bearing life, seal drag, expensive...did I miss any? For most XC style riding the old square taper standard was perfectly fine. All my current personal bikes are spinning on at least 2+ year old Shimano square taper BB's, some are over 5 years old.
From what I can tell Ted wants to design this bike around modern components, which means external bearing BB cranks, for better or worse.
If possible, I would like to build this frame to use stuff we are still going to be able to buy in 5 years. Oops, I just dropped my crystal ball. I have a ridable mountain bike in the shop that I built in 1984. Fortunately, I still have some N.O.S. parts to keep it going for a while. Remember Freewheels?
My idea on cranks would be based on the type of riding this bike is set up for.
Riding around on technical trails for a few hours a time? Wide cranks such as the Saint are A-OK.
A more all-purpose bike that might see some multi-hour epics with large sections of climbing and non-technical terrain interspersed with tech sections? I'd like to see something with a lower q-factor.
Your's and everyone else's mileage may vary though.
This is some thoughts I had posted months and months ago and I thought I'd bring it back here for this thread as it seems somewhat relevant.
My 29er woods bike musings:
Okay,
What do you guys think of a frame set up like this - sort of like a 29er "woods" bike if you will:
1. Seat tube angle 72.5 degrees
2. Head tube angle of 71 degrees with a 4" fork up front (Reba I guess)
3. 16.9" chainstays (possibly a hair shorter as I'd be running this single speed)
4. 23" or 23.25" Effective Top Tube length (with a nice slope to it, maybe even with an evil sovereign like brace on it)
5. 16" or so seat tube with a long post
5. but here's the kicker - a high bottom bracket - say 13.5"
How do you think something like that would ride?? Would the higher bottom bracket help make it easier to loft the front end up over or up on to logs or rocks and whatnot?
The short stays would help keep the rear wheel under me when I was standing and climbing right?
Just for reference - I selected that ETT length based on my previous (and current bikes) and my 5'9" height.
Whattya think???
I'd now change that selection of a Reba to either a new Fox F29 or one of the new RST 100mm air forks which are supposed to offer great bang for the buck and have a 44mm offset.
I had a Single speed in mind when I initially posted this, but I wouldn't object to this type of design in a 2x9 or 1x9 configuration either.
Just thought I'd throw this out there.
Is a bottom bracket that is that high insane? If so, what about say a 12.5 or 12.75" bottom bracket?
I think I'll wait until I have the chainstay length worked out before I get into the frame geometry. Cockpit size is something that can be talked about at any time. B.B. height, I would like to turn into drop, that is how far the B.B. center is below axle center. Angles will be talked about at length and I'll offer up some surprises here.
Indeedy it does!sounds like a bike with shorter stays
Really? The average production life of any post-square-taper standard has been about three years, because they all suck. If external bearing 68/72mm BB cranks are still the standard in five years I will eat a bug.
We've gone through Octalink V1, Octalink V2, ISIS, and now external BBs, and all are doomed. First, there's not enough room in a BB shell for a thicker axle and decent bearings, and if you shove the bearings outboard, you get all the stiffness, friction, sealing, mud-packing, and Q factor problems we all know and hate.
(An aside: everyone knows that we need larger diameter BB shells to really solve the problem. Whether this means the BMX standards of Spanish or Mid BB, Cannondale's BB30, or something else, things are going to change because they have to.)
In the meantime, this is an XC hardtail. If you are so rad that you can break a square taper spindle, you can buy the 83mm Saint integrated cranks. For the rest of us, there are plenty of blingy square taper cranks in production (Middleburn, TA Cyclotouriste) and plenty of cheapies as well (Sugino, Shimano). Current BB production includes UN-5X for the cheap and Phil Wood and Action-Tec for the bling. What are the odds of anyone building Octalink V1 BBs in five years?
We all know that Shimano has been answering questions we never asked for a long time. The cold hard reality is that obsolescence has been the marketing strategy of our Asian friend for some time. The most enduring design has been the square taper and for many reasons, would be my choice. Our components require updating, not because of short life by design, but short life by ending manufacture. When most of my clients pick up their new frame, they are seldom looking forward to equipping it with old school parts. The problem with a bigger shell to accommodate bigger bearings is the taps (?), reams, or other machining required to produce the new design. The LBS wants parts that are available from any distributor and doesn't want to get another batch of tools to service it. And speaking of service, how about the poor bike tech? Another tech school to attend. This design needs to be versatile enough to use any components. I don't want to reinvent the bicycle here. let's see what we can do with what we have and make the frame to present production standards.
Square taper would be fine by me. You can still get high quality cranks (Middleburns come to mind) and there are still bottom brackets of high quality available are there not?
Is the BB width the main issue with how long the chainstays can be anyway? I don't know the answer - just throwing the question out there.
Is the BB width the main issue with how long the chainstays can be anyway? I don't know the answer - just throwing the question out there.
Wow, I've had just the opposite experience...I've rounded out many a square taper spindle while having nothing but good experiences with ISIS. I've taken my crank arms on and off many, many times and the interface is still just as tight as the first build. This includes Race Face, Truvativ, and Middleburn mixed and matched with several BB's. My longest lasting, never die cranks and BB are Shimano XTR M950's. I got a very used set 10 years ago and 5000+ miles later I'm still torquing on them on my 29er single speed. I still haven't used the newer external types yet.
me too...same same (except I have used externals and dig them)
I still have a set of 9 year old race face sguare taper cranks and they work fine but I have to take them off every now and then and clean and retighten them more often than my external bb race face and saints.
Although I agree the siants would be wierd and alot of people wouldn't realize you need that specific chainline for the frame .
Although I agree the siants would be wierd and alot of people wouldn't realize you need that specific chainline for the frame .
Something seems very backwards here. Designing a frame around a specific Shimano part seems like the best way to guarantee that it will be obsolete and incompatible with anything else in 2 years.
If we're trying to plan ahead for 5 years down the road, maybe we should assume that the component companies will make a modification to the front derailler that gives it the proper clearance to work with the flooding market of 29ers...
If we're trying to plan ahead for 5 years down the road, maybe we should assume that the component companies will make a modification to the front derailler that gives it the proper clearance to work with the flooding market of 29ers...
So where does the tire hit the derailler? On the tail of the cage? On the cable pulley? Does anybody have a picture? I held up a low clamp XT front derailler to my frame and it doesn't look like the tire would interfere with it unless it was all the way up against the cable pulley. It would take pretty short stays to reach that.
This frame has 17" chainstays - and look how close the rear tire (and it is not a big wide tire) comes to the front derailleur without any bend to the seat tube. And from the picture that's with the chain in the middle ring too.
Ted,
how would a seat tube/BB junction like this work? The small tube could be set at a steep angle to get some tire clearance for the front derailer cage, while the actual seat tube could be angled to get the effective seat tube angle wanted.
No need for fancy bending, just an extra miter or two and a bit more work with the welder.
how would a seat tube/BB junction like this work? The small tube could be set at a steep angle to get some tire clearance for the front derailer cage, while the actual seat tube could be angled to get the effective seat tube angle wanted.
No need for fancy bending, just an extra miter or two and a bit more work with the welder.
I was just thinking about this same type of solution and trying to remember where I have seen this done, perhaps pics from the handmade bike show?Ted,
how would a seat tube/BB junction like this work? The small tube could be set at a steep angle to get some tire clearance for the front derailer cage, while the actual seat tube could be angled to get the effective seat tube angle wanted.
No need for fancy bending, just an extra miter or two and a bit more work with the welder.
The question is, what is this a solution to? It can allow more clearance between the tire and seat tube but it won't make more room for the derailleur. The derailleur has to stay centered around the BB and chainrings. Moving the seat tube forward necessitates using an E-type derailleur mount but doesn't move it forward.
Is it really really difficult to bend the seat tube ever so slightly in the right spot? For example - the guy who builds those wolfhounds has significant bends in a lot of his tubes that he uses? couldn't the seat tube be bent just sliglty to allow for a bit more clearance and still accept a standard front derailleur?
Brant at On-One gave me permission to post this as an example:
Although it still seems like an e-type or a modified e-type like Specialized is doing these days is the way to go.
Brant at On-One gave me permission to post this as an example:
Although it still seems like an e-type or a modified e-type like Specialized is doing these days is the way to go.
Sorry for the ginormous photo.
Perhaps I should just provide a link instead?
Perhaps I should just provide a link instead?
...looks fine on my monitor
That is good.
Here's something that Brant put out there and It how has me thinking and wondering.
Are shorter stays better for Single Speeding vs. geared riding where you could have the ability to stay in the saddle longer on climbs?
Here's something that Brant put out there and It how has me thinking and wondering.
Are shorter stays better for Single Speeding vs. geared riding where you could have the ability to stay in the saddle longer on climbs?
The main problem with the front derailer I've seen is tire contact with either the cable pinch bolt, and/or some other part of the cable leverage mechanism. Rotating the front derailer forward would free up a bit more space behind the seat tube.
If you look closely at the bike below you can see where the rear tire is overlapping the front derailer. I saw this bike at Interbike and the tire was firmly pressed into the front derailer. It may have been a preproduction sample, as the geoemtry on the Jamis website seems to long and steep(17.72", 73º) to have this much contact.
The other idea here was to not lock someone into an E-type derailer and help keep the seat tube out of the way if a slacker angle was used(which I'm all for).
The main problem as I see it, is the tail of the front dérailleur cage hits the tire. Now as the new stuff has all the crap for top/bottom pull cables, it gets more complicated. E type answers the cable routing issue. I have the parts coming to build a mock up to check these clearances. Sorry about the delay, but we will have to wait until after I eat the bird.
Happy Thanksgiving
Happy Thanksgiving