Designing adventure touring frame, feedback appreciated!
Hey there! I'm currently working on a project for an adventure touring bike, one that i'd like to use for long off-road rides like sections of the great divide, trans Canada trail, and visiting remote locations which may not have high quality road, if any road at all.
Here's what i've got so far, which was designed using BikeCAD after doing some drawn drafts and research.
The seat tube angle was hard to see when I put it on there directly. It's 73 degrees at the moment.
This will be TIG welded from 4130. I'd like to make this my project at the UBI frame building class this coming March, so long as they don't have any problems with technicalities in making this there. I called and asked about it, didn't experience any information that anything here would be a problem so far.
The bike in this picture is sized for myself. It's designed for use with an internal gear hub by default, but will have a derailleur hanger. Tensioning for the IGH is done via an eccentric bottom bracket. I have decided on this in order to have a drivetrain that is more resistant to mud, after speaking with a friend who had extensive great divide experience and stated that their derailleur was always troubled by so much mud.
Disc brakes will be featured, and I have some dropouts which have a chainstay disc mount on them. Are there any particular downsides to having a chainstay mounted disc brake to look out for? I'd like these in particular in order to use a heavy duty rack like a Surly rack or a Tubus stainless steel one, without the need for special adapters or jury rigging. I think that between a large rear rack and an expedition sized frame bag, the bike should be able to carry enough things.
I'd like to use the 100mm Surly Pugsley fork. The intent is to use a 29" mountain bike rear wheel, and then run a Surly Endomorph / Large Marge tire and rim on a normal width dynamo hub. If not being used in primarily off-road conditions, the bike could then have the wide Surly wheel replaced with a standard 29" wheel and tire.
I did not want to design a dual super fat tire bike because:
1. It requires odd sized bottom brackets and restricts choices
2. It did not seem like it would be an easy bike to make as a first time project, even with UBI's help - if they even said yes to doing it at all.
Regarding 29" rear, fat front:
I think that this could give the bike a lot of versatility - it can be run for a heavy duty off road situation offering a lot of flotation on the front, but a normal 29" wheel can be equipped - or even mid width touring tires front and back if the tour will have a lot of road.
To be honest too, I just want one of those super fat tires because they're awesome. I could go mountain biking too!
Or is this just being naive?
Things I am most concerned about:
The rear chainstays were made a bit longer in order to facilitate fenders and large amounts of mud clearance. That this will make the wheelbase longer is understandable, are there any severely negative consequences otherwise?
Should I use a 135mm non-offset Surly Pugsley front fork instead of the 100mm unit? That would give the bike the bike the ability to swap front and rear wheels if normal 29" wheels were being used, although not if the Pugsley wheel was installed. Are there downsides to this otherwise? The only problems I could think of were that this would disqualify the use of a dynamo hub, and if a 29" wheel was used, you probably could not use the cantilever mounts on the Surly Pugsley fork - but I was thinking that really there aren't many rim brake compatible 29" mountain bike wheels anyways, are there?
Have I messed up severely on the geometry anywhere? Should it be tweaked somewhat? I am 5'10" with a 33" inseam, and find that my personal favourite ETT is about 585 - but to keep the front center from being super short, the plan is to make the ETT a bit longer and to use a shorter stem. I would like to use an On-One Mary bar, this is a personal favourite.
Any feedback would be really appreciated. I have about 6 weeks to tweak the design outside of school.
"The seat tube angle was hard to see when I put it on there directly. It's 73 degrees at the moment."
That is pretty normal. The only thing is, and this goes for everything, with out-there builds in particular but anything custom really, you need the parts up front. Sure 73 is a good general walmart number, but what saddle what seat post? Do you want an offset seat post on a bike with 470 chain stays? So you need to draw up all the details, and be sure you really understand how all this stuff works, or it is just an expensive LBS bike with some stuff that isn't cool to work around.
"The bike in this picture is sized for myself. It's designed for use with an internal gear hub by default, but will have a derailleur hanger. Tensioning for the IGH is done via an eccentric bottom bracket."
You really have to think this through carefully. It seems like the kind of thing where there are no good answers. Also, you have to consider the impact on your time at the school, fabbing the right kind of BB set up could suck up a lot of time. And the stock ones aren't great. There is a company that came out with a unit that bolts through so you can use the full size eccentric tube, and don't have to split it or screw it. What I hear is that if you elect to tig, your time is tight at the UBI course.
Getting back to the 73 degree thing, with an EBB, your cranks won't be centered in the BB shell. So 73 will not deliver 73 effective. You need to rethink that.
" I have decided on this in order to have a drivetrain that is more resistant to mud, after speaking with a friend who had extensive great divide experience and stated that their derailleur was always troubled by so much mud."
If you were buying a rig, I would say go for it, but this will make a lot of problems, all of which are pretty minor, but you blow one in the crunch, and your whole rig is toast. I doubt UBI is the center of the universe designing this kind of stuff. What if your ride is dry? Most other people use deraileurs, so you won't be alone.
"Disc brakes will be featured, and I have some dropouts which have a chainstay disc mount on them. Are there any particular downsides to having a chainstay mounted disc brake to look out for?"
Yes there are, it is all doable, but I think you are out of your depth"
"I'd like these in particular in order to use a heavy duty rack like a Surly rack or a Tubus stainless steel one, without the need for special adapters or jury rigging. I think that between a large rear rack and an expedition sized frame bag, the bike should be able to carry enough things."
I sorta think frame bags are stupid. You need to have this stuff, certainly the rack, so you have more than guesstimates as to how this is all going together.
"I'd like to use the 100mm Surly Pugsley fork. The intent is to use a 29" mountain bike rear wheel, and then run a Surly Endomorph / Large Marge tire and rim on a normal width dynamo hub. If not being used in primarily off-road conditions, the bike could then have the wide Surly wheel replaced with a standard 29" wheel and tire."
This isn't all that big a deal if these two wheel and tire combos have the same axle height, otherwise, back away while you still can. Your design is a newbie special, the main feature of these, is to combine all the most radical features one can, while ignoring all the boring stuff that actually works. This is OK with colours. I do this all the time, so I recognize the symptoms, but unless you get real lucky it leads to bad bikes. It sounds cool sitting around and talking, but out on the trail your focus shifts to the real world in which sensible well designed, reliable solutions are all that mater.
" I did not want to design a dual super fat tire bike because:
1. It requires odd sized bottom brackets and restricts choices
2. It did not seem like it would be an easy bike to make as a first time project, even with UBI's help - if they even said yes to doing it at all."
A hybrid will give you real world resupply problems, just to name one.
Regarding 29" rear, fat front:
" I think that this could give the bike a lot of versatility - it can be run for a heavy duty off road situation offering a lot of flotation on the front, but a normal 29" wheel can be equipped - or even mid width touring tires front and back if the tour will have a lot of road.
To be honest too, I just want one of those super fat tires because they're awesome. I could go mountain biking too!
Or is this just being naive?"
Yes. You know the old saying about butter? One second on your lips, a lifetime on your hips. This is all really radical stuff, but there are lots of people who would do this ride on 1.5" tires with some tread, a lot of it is roads. I was along for the Canning Stock route, and Vik's videos can make anything look cool, but this is a bad idea. The very best case is it will work ok and cause no trouble, which is quite likely since you only need to please yourself. But is it wise? Now if you just want to do it, and not tell us, and enjoy your creative freedom, go for it. But it's hard to get behind. Buying this stuff and dreaming about it is going to feel good. I don't really see that it will deliver for you.
"Things I am most concerned about:
The rear chainstays were made a bit longer in order to facilitate fenders and large amounts of mud clearance. That this will make the wheelbase longer is understandable, are there any severely negative consequences otherwise?"
Long chainstays are pretty good. You are going for three things on one bike that stress out CSs, length, Rohloff, and disc. So you need to chose the right tubes, and detail them properly.
" Have I messed up severely on the geometry anywhere? Should it be tweaked somewhat? I am 5'10" with a 33" inseam, and find that my personal favourite ETT is about 585 - but to keep the front center from being super short, the plan is to make the ETT a bit longer and to use a shorter stem. I would like to use an On-One Mary bar, this is a personal favourite."
I hate that bar so I don't have much experience with your reach issues. You messed up on the EBB and seat tube angle, I don't know about your cockpit fit either, presumably you have one bike you already sit well? I'm not sure what the fork offset is, or you HT angle, or your trail?
" Any feedback would be really appreciated. I have about 6 weeks to tweak the design outside of school. "
Yeah, well there you go. Good luck. Get that fork before you go, get the headset, wheels, tires, Rohloff if you go that route, racks, etc... You really need to figure out where all this stuff goes. On an expedition bike I like Rohloff, but they built it for 26 inch wheels, so sure you will survive, and the great divide isn't a Hans Stucke kind of thing, but I still don't like that direction for myself.
I think I would prefer to run some normal 29" tires for most touring conditions.
Regarding the trail actually, I'd like to know more about what you might think about it. Unfortunately, most of my bicycles lately have had lower trail between 35 - 40mm. I based the 85 number on looking at some other 29ers, trying a few out, and just sticking with a happy medium. It seems like a pretty "safe" number but I'd definitely be interested to hear more about it though, since i've not got a lot of experience with 29ers in particular.
Regarding the hub, I have a local offer for a slightly used but much discounted Rohloff, which is spurring a lot of temptation :)
While it's probably a lot of fun to design your own bike why not just buy one? The all time champ is for sale from Bruce Gordon. While this is an older version the Rock & Road could be one of the best all around bikes ever built.
"Should I consider using a non-setback seatpost and a different angle entirely?"
I know you aren't asking me, but I am not offering internet fit advice. 73 is a pretty normal cockpit angle for efficient cycling in a touring bike, it can also be lower, would not likely be higher. That is for a standard BB where the Cranks spin on the CL of the seat tube. With EBB in the normal forward position, you are going to have an effectively lower seat tube angle, unless your extension was so great it crossed forward again, maybe that is impossible I haven't drawn it out.
I always assume, but may be wrong, is that the reason we have seat post offset, is merely to create an effectively lower ST angle which is good bio-mechanically, while allowing the rear wheel on racing bikes or MTBs to be as close to the ST as possible. It is a discount version of those bikes with a bend in the tube to accommodate the tire. If that is true, then why have it on a bike where you can fit a water bottle between the tire and the frames. But there may be other opinions. What I would do is drop a plumb bob from a currently fitting bike to the cranks, from the horn of the saddle. This will give you a number along with height that establishes the real position of your saddle to the cranks, which is what it is all about. Then you get your real saddle (buying a new one for the trip?), find out the sweet-spot for adjustability and strength on the saddle, get the most efficient post, figure the best forward position for the EBB cranks center, etc... and design the cockpit. This is easy in the sense that if your current bike is right for the type of riding you will do, and if you have the real parts, it is just draftsmanship. There aren't the guessie issues that are feel, or structure related, and require a lot of experience. If you don't have a bike that fits, then you might grab some bikes and sort out a position. I am leery of fit-meisters, because I think it gets tough outside of off the rack people. Maybe they are use to fit and proportioned racer types with decent form, but give them an odd sized gimp with poor form, and they may start to spit out some strange numbers. But if you have a local person you can trust, all the better.
"I see. I'll consider that!"
In my case I have all the tools in my shop, and I can take all the time in the word sorting things out. But you would nearly need to have all the answers sorted, and idealy some of the parts made, before you get there. I mean if UBI is 100% behind you, that would be different.
"'Yes there are, it is all doable, but I think you are out of your depth"'
"Could you please elaborate? Is it an issue of having to have specially designed stays that might just be too hard to do at first or in time constraints? I suppose I could save them for some time down the road if necessary."
You are not describing something out of the extraordinary, these bikes exist, and you can look at them all over the net. There is the basic issue of how you will get this thing built, if you don't have either a ton of help, or all the parts, and are able to do a dry run. There are cable runs, and oddball cable guides, there is the combining 5 load factors into a set stays, there is the Rohloff drops, the fitting for the disc, the rack. It isn't super human stuff, doing BOs is relaxing work. I wouldn't have too many concerns if you had time post the build to work away at home, pre-paint. But if it all has to go down in a few weeks, and you don't yet know the questions to ask, I think it is risky.
"I have all of those components in particular, and have grown accustomed to using them. Even if frame bags are stupid"
Well only to me. I see it as the hammock of the '10-'11 season. They make sense on bikes one can't get racks on, but I don't see the value for the most part. Though it probably doesn't mater, that frame is goign to be crowded with cable runs, and straps, where do the water bottles go?
"Well, I will consider that too. I don't personally see what the harm in trying it out would be, it seems as though switching between an Endomorph and a fat 29" tire shouldn't be much hassle, so even if it turns out to be a silly idea, it'll be a learning experience and it shouldn't ruin the bike."
I haven't tried it, so you could well be right. If there is zero difference in geometry, and the forks can be changed. My downside is I don't see myself wanting to ride the big tire after the first ride on it, and if it forced me to have the wrong geometry for my 700C, I would be ticked. But if is is the monster that is a kluge, then your worst case is your best case.
"The fork offset on the 100mm Pugsley was 43mm, head tube angle is currently 70.5, trail is approximately 84.7 - 85.8 mm depending on whether a matching 29" wheel would be used, or the Endomorphy / Large Marge wheel."
That doesn't sound great to me, is it Surly stock? I think a low tube angle suits this bike, but one normally wants to stay closer to conventional trail. You basically have the offset there for a 73. But this isn't my kind of bike, so the numbers aren't in my head.
"Regarding the trail actually, I'd like to know more about what you might think about it. Unfortunately, most of my bicycles lately have had lower trail between 35 - 40mm. I based the 85 number on looking at some other 29ers, trying a few out, and just sticking with a happy medium. It seems like a pretty "safe" number but I'd definitely be interested to hear more about it though, since i've not got a lot of experience with 29ers in particular."
I try to stay pretty much in touring land, so I don't know this stuff. This is the kind of thing where the guys around here with broad experience on type are a real asset. UBI should be able to nail it for you. I do like bikes with low head tube angles, but it is for a longer wheelbase, and a tracking ride. That tends to be closer to 50 on trail, and means non-stock forks. The Marge is an out there wheel and brings a variety of stuff with it. The one place where I depart with the MTB as touring bike, and I have thought of a great divide bike for myself, is on the steering. I want a stable bike, and don't expect to be picking my way through rock gardens, and if I was I would just try to step it up. Not saying I would build a road touring bike, but I wouldn't be going to single track geometry either. Be interested to hear what the experts have to say.
"Well, I thank you for the help! I will definitely consider looking into construction methods for the first time at least that are simpler and less time constraining. If time is short, I would definitely prefer to concentrate on solid construction over adding optional features."
Regarding the hub, I have a local offer for a slightly used but much discounted Rohloff, which is spurring a lot of temptation
Rohloff is a good idea, and if this is a mudfest, all the moreso. I have a Rohloff hub, and I have been working for several years on a frame design. Clearly I have insufficient time pressure. I know there are a lot of details, nothing all that tough when you get going, and have support. But it does require planing. I have been working the last week on getting the wiring done for my shops. Such a simple job conceptually. I worked 2 hours on it today, and thought I would be plugged in by the end, then I caught some detail I had overlooked , and I have at least 2 more hours to go. Crazy, but it is the little details or the one missing part, or the right part that doesn't fit that suck up a lot of time.
There are quite a few online reports, and flicker accounts for UBI, maybe someone did a Rohloff build and you could hook up to see how prepared they are for out of the ordinary parts.
I did check on mud on the GDR, and there are a lot of accounts with mud complaints out there. So you could have a point. One thing I did notice was how the mud was building up on even 2 inch tires. While one doesn't want to sink into the mud, one doesn't want to carry twice the weight of it either. Is it possible that a consequence of the mud could be a road trip? Or are there no practical alternative bv-passes?
So the bike you need has to travel to remote locations where the road quality may be poor to non-existent, will need to carry enough gear to make you self supported, and will have to deal with extremely dirty and muddy riding conditions.
If I was building a bike that had to do this I would be looking at a 26 inch wheeled expedition bike to get stronger and ore affordable wheels and make replacement parts more available if I need a spare. This leaves options to run skinny high psi tyres or something up to the 2.3 range.
IGH would also be great and instead of the extra expense and complexity of an eccentric, just use horizontal drop outs... but then what happens to the rear disc ?
You don't need one.
I'd run a disc up front and a v brake in the rear... this maximizes the stopping power and simples up the installation of racks in the rear but would still use a front fork with additional V brake mounts just in case I need / want to swap the front wheel to one without a disc.
Building your own frames is an admirable idea. 30 something years ago, when I had a job that had me living paycheck to paycheck, and small kids and couldn’t afford to ride what I wanted, I built a couple of frames. The last one was supposed to be a commuting frame, with 26” wheels, fairly long chainstays 450mm) and a long top tube (620mm) with a 73 degree seat and 70 degree head angle. The fork had 50mm of offset. A few years ago I decided to set it up as an expedition touring bike. Very few changes had to be made, but one was the fork. Turns out the only real mistake I made with the original design was the fork offset. I have since learned that what the big time French custom builders liked for trail for heavily loaded “camping bikes” was on the order of 48mm. Last spring I found a bike builder who would not only straighten the frame (to repair a crash damaged frame) but bend the fork to increase offset from 50mm to 63mm. That changed the head angle slightly from 70 degrees to 70.8 degrees and decreased the trail from 66mm to 47.5mm (with 26x1.75” tires). When I built it back up with racks and mounted my loaded panniers, I was very pleasantly surprised. It was magnificent! What a concept! I am currently planning to take it cross country this summer.
From the perspective of this old man, you may want to consider making two frames: the first fairly conventional, based on the wisdom of those who have gone before, pretty much guaranteed to work well; and a second with the combination of all your very interesting ideas, with reduced risk if you aren’t totally happy with the result.
For an expedition touring bike, the conventional wisdom seems to be 26” wheels because they are stronger, and replacement tires, etc. are more readily available in Timbuktu; rim brakes, either cantis or V brakes; your choice of flat bars or drop bars; long chainstays for heal clearance with panniers; fairly long top tube for toe clearance with front tire or fender; derailleur gears for logistic compatibility in far away places. (I know the Rolhof hub is supposed to be very good and nice and reliable. I have no experience with it, but at over $1000 I don’t expect to be getting one anytime soon and if it does brake while you are in the middle of nowhere, you are really hosed
As someone who doesn’t ride off road all that much, riding my “expedition bike” off road is interesting, but it does point out a few things. I like drop bars, and my expedition bike has drop bars, but the usual width is 45cm and that seems to be too narrow for rough riding. I have switched to 48cm Nitto bars, which should work better, but may still be a little narrow for rough stuff. I have seen the wisdom of flat, fairly wide bars for rough stuff
It isn’t impossible to get good handling with disk brakes, but it is more difficult to get any fork compliance. I have a Salsa Vaya frame. It has mechanical disk brakes. They work fine, but the fork legs have to be stiff enough for the disk reaction, which pretty much rules out much shock compliance. I also had my Vaya fork bent from 45mm offset to 63mm offset. This increased the head angle from 72 to 72.4 degrees and decreased the trail from 68mm to 46.5mm (with 700x40c Conti Avenue Semislicks). I much prefer the new configuration, but you can make your own choice.
You have a wonderful opportunity here. Just remember “Man does not live by one bicycle alone.”
Well, i'm really appreciating all of the information!
Peterpan1, thank you for your input on all of this, that plumb bob idea is something to do for sure. I'm not asking for fit advice, no, but what you are giving is much more valuable. I'm sure that when I get there UBI will look over all the designs, measure me up, and then tell me how it should be! But the whole process of designing frames is such an enjoyable learning experience right now that i'm trying to pick up some basic skills and try it all out beforehand as well. Knowing tricks like this is really useful. I've got some books arriving shortly that should help learn even more :)
Time is a concern from the aspect that i'd ideally like to focus on getting the most rounded help from UBI possible in the 2 week timeframe. Not finishing the bike 100% would be alright so long as I had the direction to finish off in the end. There's a local builder who had made an offer of providing some help with this in exchange for some machining assistance, so there may be a bit more help post-class.
As for just buying one like the Rock & Road, I'm not really trying to go just to UBI to build up one dream bike for myself and then drop the whole thing. To attend the 2 week session as an international student, it will be almost $4,000. That could buy quite a nice dream bike from a good custom builder on its own. Actually, even the Surly Troll is 95% of what I really would absolutely love in a bike. I'm really really not rich. I'm a self supported full time student, and have no family to go scrap money from (have been saving for this course for months now). Were it just about a bike, i'd buy a Troll. It's the craft that draws me in.
Sixty Fiver, I have always personally used 26" wheels as well. I think that the availability on 29" components is getting better, although one shouldn't hope on getting much in the way of tires for that size in a lot of places in this world. I was tempted by the 29" component due to the fact that it could play well with switching over the front wheel to a Pugsley, and that i'm neither heavy, a dead weight rider on bike, or a big packrat.
After thinking about it though, i'm starting to think there's too much trade off to using the 29" wheel. Using a 26" wheel does get a lot of extra availability, provide that extra strength, and to me it also allows for the design of a bike that can eliminate the toe striking the tire, which I can't seem to do on a 29" bicycle without other geometry compromises. It would be easier to design a lower trail bicycle using these wheels, it seems. It also allows internal gear hubs to have lower effective gear ranges without exceeding their optimal sprocket ratios..
The 26" option also opens up forks like the Troll fork, which have disc mounts *and* special rack mounts, opening more cargo options.
There's a lot of downside to the 29" format for this purpose in the end, I guess. Dropping it wouldn't be too disappointing to me, in the end. I wanted to pick it up for the Pugsley wheel switch.
Perhaps I should just go back to the drawing board on this one. In a perfect world it would be sweet to learn how to nicely bend tubing and make designs incorporating exotic and jaunty looking rides, install exotic frame components, and use fun ideas right out of the gate - but for now, perhaps the focus should be on just building something that focuses on developing the skills to springboard into those things later.
Abney - We have been designing more and more 26 inch wheeled bikes here and you know how I like my 26 inch wheeled expedition bike... if I was going to build myself a new one I would be taking a lot of cues from my Kuwahara Cascade as it is the perfect bicycle.
This is the oldest method for custom bike building and fitting... if a person really likes the bike they have been riding you can draw a lot from that bicycle in working up a new design rather than doing it from the ground up.
If one is looking at doing some epic and remote touring a 26 inch wheel makes a lot of sense as you are going to be able to find spares almost anywhere while parts for 29'rs and bikes like a big wheeled Pugsley are a little more exotic.
I really could not improve on my Kuwahara save for the fact I am going to build some new (integrated racks) and refresh the finish and might add canti mounts in the rear, not that I don't like the chainstay brake, but that finding replacement parts is getting harder.
Funny... most people would start with tig or lugged frame building but arvon set me to brazing frames right off and think my background in fabrication really helps.
I like filet brazed frames almost as much as I like lugged frames and this allows for a lot of creativity.
The Cascade in summer and winter / expedition modes... I already have my perfect touring / expedition bike in this.
My next project will probably be a classic French randonneur modeled after the Peugeot UO8 as I really like the geometry and handling characteristics but would like to see all this made with better materials and standard parts.
Also want to build a 30's styled track bike... :)
If you do have access to some tools, that would change things.
While it may not be as exciting a prospect to try a more conventional build, what can be worth your while is to try this more conservative approach for your big ride, then when you get back you will have a great deal of experience to take on another project and truly design more closely to your specific needs. That should be an exciting prospect.
If you build a wacky bike and it works out, you are stuck as a frame builder needing to convince the world to adopt your vision. There would be a sort of truth in that, but it would be a difficult prospect. If a wacky ride ends up as unsuccessful, one tends not to have much of a basis for evolution. Sure one could decide to make the next dozen frames as each a minor variation of the initial one, hoping to get it right. But that is unlikely to really appeal. One tends to feel the initial frame wasn't successful and to flip off in a more conservative direction.
Anyway, have fun with it.
|All times are GMT -6. The time now is 09:42 AM.|