RoadBikeReview.com's Forum Archives - Cyclo-Cross
Going custom, did I forget anything? Here's my list...(30 posts)
|Going custom, did I forget anything? Here's my list...||SJT|
Feb 12, 2003 10:16 AM
|I made my final decision to get what I wanted all along, a custom frame. Before I place my order this week, I would love to get some feedback on the sizing of the frame and the options I am getting. Any help would be great, here's my list:
Top tube length- 56cm
Seat tube length- (cc) 54cm and (ct) 56cm
Saddle pedal spindle length- 94.6cm (172.5mm cranks) *note: that is for *max* leg extension, could never keep the saddle that high off-road though*
Seat tube angle- 73
Stem length- 12cm
Stem height- 14cm
Stem angle- 90
Saddle fore/aft- 50.2 (nose to bar)
Crank Arm length- 172.5
Handlebar- (cc) 42cm (ee) 44cm
Handlbar drop- medium (145-159)
True Temper OX Platinum tubing
disc-tab (no canti bosses)
curved seat stays
1-1/8" head tube, reinforcing ring at top and
bottom if possible
sloping top tube
forward facing seat clamp to keep dirt out of the seat tube
mountain bike axle spacing- 135mm
plenty of room/mud clearance for larger 'cross tires such as a 38 with fenders, or even larger if feasible.700x45 (29"er tires) for trail riding?
room to run a triple ring if I want, but will most likely be using double ring cross cranks
top routed cable bosses (would you agree this is best for 'cross?)
2 sets of water bottle mounts, 1 on seat tube, 1 on down tube
rack braze-ons, if possible, on the seat tubes and drop-outs (I might add a rack one day...wouldn't be used for touring, just very light duty)
Did I miss anything? Would you add/delete anything? Overall, does this look like a successful design? I really respect everyone's opinions here and would love to get some feedback before I drop some $$ on this frame. Thanks in advance.
|re: Going custom, did I forget anything? Here's my list...||DropTheHammer|
Feb 12, 2003 10:40 AM
|Head tube height and fork rake.|
Feb 12, 2003 10:41 AM
|re: Going custom, did I forget anything? Here's my list...||SJT|
Feb 12, 2003 10:56 AM
|Thanks for that reminder. I need to get that value from the shop owner that did the fitting. I believe we were discussing a length of about 120mm though. As for fork rake, I have no clue. I'll need to talk with him about that. This is not meant to be a racing bike, more of a "do-it-all" bike. I do want a straight leg fork though.
Feb 12, 2003 10:40 AM
|Looks nice. I didn't see any mention of Headtube angle. This -- combined with fork off-set -- will have impact on how the bike handles. Most CX bikes seem to be between 72 and 73 degrees, with fork off-set (rake) around 42 - 45. One other thing: don't know if you plan on racing this bike, but you may not want too much of a sloping top-tube, as it can interfere with shouldering. Enjoy|
Feb 12, 2003 11:00 AM
|Thanks for the advice, I'll need to check on the headtube angle, not sure what my fitter decided on. As for the rake, I need to do the same thing...we didn't talk about fork off-set. This is not going to be a race bike, so the sloping top tube shouldn't be a problem. Also, the slope will not be that radical, probably be down about 1-2cm. Anything else I might have missed?
|some more specs||Dan Cas|
Feb 12, 2003 12:12 PM
|Chainstay length,Bottom bracket drop,type of dropout(vertical,horizontal,or interchangeable),bent or straight stays,tube diameters|
|straight leg fork||atpjunkie|
Feb 12, 2003 1:46 PM
|I assume steel fork, yes? If so get a smooth curve. Much more compliant ride. This is going to start a fire but physics doesn't lie. Vibration and force travel easier in a straight line, whereas in a curve they are more evenly dispersed. Plus it looks cooler.
People will argue this back in forth but you never see them arguing that your curved seatstays produce a smoother ride.
It can't work both ways. Since this is a utility bike, go curve as it will smooth things out a bit. Plus why 'soften' the back and make the front more rigid? seems counter intuitive
|straight leg fork||achmedzacky|
Feb 12, 2003 3:12 PM
|just so the preceeding (mis) information does not go to the archives unrebutted. Curved fork blades and chainstays are irrelevant to comfort. If the design looks cool to you, fine, but don't use pseudo-physics to justify your design choices.
Feb 12, 2003 5:14 PM
|I knew this would start a flame. Yes, throw out my pseudo science. While were at it, let's throw out this 'round earth' nonsense as well,
and all those silly engineers building bridges and dams with all those curves, what a waste. All that pseudo-science about curves superior distribution of load forces POPPYCOCK!!!
let's not forget those propeller heads at Pinarello, Colnago, Yeti with their silly degrees in engineering WHAT DO THEY KNOW?
it's all MARKETING. funny that's what I do, but somehow I still remember my math classes.
Bring back Stonehenge, eliminate the arch!
Feb 13, 2003 5:06 AM
|Actually it is not the curve that gives a fork its stiffness (or complience). How stiff it is is primarily determined by the material it is made out of, the leg cross section, and the perpendicular distance from the hub to the steering axis. How the hub got to that location is not very important. The curve does help in vibration damping though.
Arches are useful when loaded perpendicular to their long axis. This puts the arch in compression, and most materials are stronger in compression than tension. What a fork experiences is bending and axially loading though.
I do think in general that curved forks tend to have a smaller cross section and as a result are usually more cumplient.
The easiest way to tell how stiff a fork is would be to ride it. If you feel it is more complient than another, who can argue with that.
I do think that curved forks in general tend to have a smaller cross section and as a result feel more complient.
Feb 13, 2003 11:19 AM
|true, but a curve also distibutes load and dissipates force (and vibration) along it's length with some of it 'sluffing' off the curve. Bridge bracing (both curved and x'd is designed to prevent harmonic resonance from shaking a bridge down. Tesla proved this as did a high windstorm on that canyon bridge. If you don't brace to reduce vibration, things, if they hit their resonant frequency will literally shake themselves apart.
Also, consider vibrational instruments (Tubular Bells, Chimes, xylophone, etc...) they build them straight for a reason. Vibration (which sound waves are) travel best in a straight line. if you don't believe me, buy two sets of wind chimes. bend one set, keep the other straight. strike them and note diff's in sustain and sound. This is all basic physics, straight lines allow the vibrations to function at an optimum. MTB went through this argument in the early 80's
(I've discussed this before) pre suspension. They switched to straight leg forks (some Mfr's in about 1982) and the results were bikes breaking at the headtube junctions (not pretty). the end result was an end to this trend in less than a year. (I know I was a test pilot). Also as far as seatstays, would a mfr spend all the extra $ in labor to bend seat stays (and build the jigs) purely for aesthetics?
Doubtful. So if there is some rule that general rules of physics don't apply in bicycles, please inform me as then maybe there is hope of a 200 plus pounder winning a mountain top event.
Feb 14, 2003 10:06 AM
|All this does not change the fact that the argument that curved forks are more comfortable than straight is a false one. With the same materials and most importantaly the same crown and Steer Tubed size, an equally raked curved and straight fork will not behave any different. Any good builder could build you a very stiff curved fork and a very flexy straight fork.
Your whole vibrational modes argument also is irrelevant. Any structure will have vibrational modes, curved or straight. Just by having a "smooth curve" does not preclude it vibrating catastrophically.
You also wrote:
""Also as far as seatstays, would a mfr spend all the extra $ in labor to bend seat stays (and build the jigs) purely for aesthetics? """
This really is not a scientific argument. There are plenty of excepionally expensive ideas in the bike industry that are wrong or based on false premises, that does not really keep people from making them or buying them. Look, a curved seat stay will bend nominally more that a straight one, but unless you have a "soft tail" type design, it is an irrelevant amount. The driving force here is not physics, but marketing and differentiation. The customer ends up paying the increase in cost anyway.
You can apply your physics lessons all you want, but you aren't getting to the root of the situation:
The generalization that curved is more compliant than straight is false. The deflection that occurs in the fork is at the crown, NOT in the curve.
The best thing to do is to talk to your builder and see what kind of fork they come up with for your requiremnets. If the builder likes curved forks and thinks they complement the bike, great. If they like straight forks great as well. If you want a super compliant fork, tell the builder and they can do it by adjusting materials and crown type.
Feb 17, 2003 4:24 PM
|so you seem to have missed Logic Class as well as Physics. Simply dismissing a point is not considered valid counterpoint in a debate. You need to back your claim with some sort of evidence to have any argumentative validity. Poo-pooing ones argument wouldn't classify as 'valid'. I'll show you how this is done by rebuffing your (lack of) arguments.
Crown and steer tubes, if you build 2 forks with identical crowns, steer tubes and materials, the curved fork will deflect more energy. It's true any builder could build whatever you wished but that does not invalidate the curves vibration dampening abilities and is really irrelevant.
Vibration is the main culprit in 'rider fatigue' and physics has shown us that it travels easiest in a straight line as it is the shorter distance. The curve also accounts for the deflection of force vectors away from the structure itself. To disregard this point is to disregard all modern archetecture, engineering etc... since the invention of the arch. The catastrophic tests (see Tesla) were to illustrate a point that you've seemed to avoid. The extra structure in building and bridge design dampen vibration in the same way a curved fork does. With out it, the bridge becomes like a guitar string. Yes, this a point to the absolute extreme and it would never happen in a fork but it illustrates how engineers had to design around the 'straight path' to prevent it from occuring. All things can 'catastrophically vibrate', straight ones (see Tesla) do it easier and sooner.
as far as crowns, it has also been shown that the curved unicrown (IMHO not as aesthetic as the traditional) is stronger (by spreading force along curve instead of at the fork/crown 90 degree joint) and less prone to fail.
as for your marketing argument, this is my field. None of my clients (including 2 MTB mfr's) would add cost and drastically slow down production purely for marketing puposes. This is not what we refer to as 'good business'. Did you miss business class as well?
Marketing is the first dept. cut in financially tough times
as it is lowest on a companies priority. To add unneccessary cost would drive price up and make you no longer competitive in the marketplace. If there were no performance benefits the consumer would avoid.
So if physics isn't the point what is? What is the 'root' of the problem? Fork, crown and steer tube are one joined piece so they will work symbiotically and changes in any of them will affect a forks total performance. Where is this research into your 'crown theory"? and to deny the curves deflection ability is to once again deny my 'silly' physics lessons. Once again does bike construction exist in a parallel universe where the principles that govern ours don't apply?
so let's talk to some builders so to speak.
Tom Ritchey: inventor of the Plexus where his Swept (READ CURVED) seatstays give the bike a measurable amount of travel.
He applies this to the swiss Cross as well to in his words 'soften up the trail'', but with 30 years of frame building experience what would he know? Mountain Cycle does the same producing nearly one quarter of an inch of deflection (read Travel) and classifies their bike as a 'suspensionless soft-tail'.
Scott Nichol and John Castellano at Ibis, using curved seat stays and flat chain stays produce a soft-tail with double the travel of all other ST MTB's (SILK TI). The best part is the wide/flat chain stays make the bike more vertically compliant but lateraly rigid as lateral forces are countered by stiffer FLAT STRAIGHT stay.
This applied theory (note: Castellano is an engineer) works so well, they build a version out of Al. The stiffer material (Al) still gets as much travel as most Ti ST's and both Ibis' show less fatigue to the flexing parts. Unfortunately this increased cost and slowing of production is what drives Ibis to bankruptcy as they can't make them fast or cheap enough. This point backs my marketing argument.
Feb 18, 2003 1:48 PM
|The curve of a bridge and a curve of a fork are not the same. One is supported at both ends, one is not. For all practical purposes the load and behavior of a fork are path independent.
You are applying physics incorrectly. You would need to brace a front fork at a third point to get your curved benefits, or at least change the head tube angle AND type of loading, so that ALL the forces were axial. In real life the fork is not loaded in this manner.
I think this probably has been covered to death on the rec.bikes.tech list, spend some time there.
As for your assertion that marketing is not a driving force to production, I don't really think you are being honest with yourself, your arguments here are pretty facetious. First example, carbon seat stays (they probably make a frame easier to build though, so not a great example, but still of little or no value engineering wise). I will give you an another example that will probably not impress you. A carbon fork maker used to make 2 molds for each fork, one curved and one straight legged. The guy who owned the company knew it did not make a difference, but he felt he sold more forks that way, so he went with it at the cost of tooling and stocking issues. I think there are thousands of examples of things done in the name of differentiation from competitors, rather than in the name of good science. GT triple triangle anyone?
As for the curved seat stays. First we can disregard the ibis design as it has a shock in it, these work because there is an opening in the circuit, the seat stays do not bend. They are a nice design, it would not work if there was no suspension in the loop. On the closed rear triangles the "travel" has to come from the seat stays bending. Given a typical seat stay, I don't think the flex is 1/4". I will allow that in this case it is nominally more flexy, but I think the 'travel" is exaggerated, but I have not tried one. I did some calculations based on a serrotta type design and the flex was very insignificant.
BTW, aluminum is not stiffer than Ti. Ti is about 1.5-2 times stiffer than Al, steel about 3 times than Al. This kind of ranks up there with "curved forks make a difference" in the annals of cycling misinformation. Al frames are "stiff" because aluminum is an inherently more flexable material. You probably have this misconception as you listen to the markete.... Never mind.
I think I am done here. I suggest you try some experiments, learn some beam bending and look around on rec.bikes.tech,
"keeper of the crown theory"
Feb 18, 2003 4:34 PM
|AL is not stiffer by material, but is stiffer by design and usage. CroMoly is stiffer than both. It is Aluminums weight to thickness to strength that allows such 'oversize' tubes to be used which in practice makes a stiffer bike. I understand this point and once again this is an issue of practice vs theory. Al by material is softer , granted , but by design and usage is stiffer. So we can agree on this I assume? this isn't misinformation it's semantics (the last refuge of a scoundrel). So let's drop the semantics or are you going to tell me a Ti or Steel Bike produces a less comfortable ride than a Cannondale CAAD 3?
Why the third point? One would assume cantilevers function between 2 points. A)being the rider and B) the contact patch of tire to road. When you flex test materials you apply pressure at the ends, not by adding a third point. A third point would cause a kink in the bend. This would turn it into a LEVER. I've seen the arguments presented in rec. bikes and like yours none ever present how the fork somehow escapes basic laws of physics? A fork is loaded between rider and earth with force loads changing from sitting to standing to side to side sway of a sprint. You don't need a third point, energy is travelling from A to B and back.
Your GT triple triangle arguement is again specious. This is, as you say product differentiation, but it takes little additional tooling, jigging or welding time in comparison to bending S-Stays so it's cost to market benefit is far greater. Especially in Ti bikes where just creating the tubes drives prices through the roof it makes no economic sense to add unneeded labor. As far as carbon seatstays I tend to agree. Once again as you say it's CHEAPER to do than normal frame building and supports my point. Bells and whistles are only allowed when cost isn't a factor.
The Ibis point was the chainstays not the seat. It's wide flat and straight stays created a lateral stiffness not known in other ST's. Again you miss the point. All ST's have an open circuit, it was Ibis differentiation in the chainstays that produced the superior results.
Yes on 'closed frames' it is the curve that aids this bending but then again that's just physics and I won't waste your time with that. It's funny that no such bike exists with straight stays...hmmmm kinda begs the question. The seat stay bending on both the Ritchey and the Mountain Cycle add Flex that was measurable (Mountain Cycle claims near .25", but I wasn't there for the test) so proofs in the pudding. If it applies to stays it has to apply everywhere , physics works that way.
I will agree though, yes you are done. quite.
it all comes down to energy and if it travels as efficiently in a curve
as it does in a straight path there would be no linear accelerators, only cyclotrons as they take up less space.
STUPID EINSTEIN, STUPID NEWTON, STUPID SCIENCE
STUPID ENTROPY, STUPID THERMODYNAMICS
Bikes are IMMUNE
|Science Indeed||Dan Q|
Feb 19, 2003 8:09 AM
|If you know so much about structural analysis, why don't you pick up a pencil and do an analysis of your curved fork to prove to us that they all have a much more complient ride. Actually you are so dead set in your convictions you must have already performed one, so why don't you just scan it and post it here to make us look like fools.
It is obvious that there are more important factors in the stiffness of a fork than if it is curved or not. Saying that curved forks are more complient than straight ones is like saying red frames are stiffer than blue ones.
Feb 19, 2003 7:49 PM
|will do when I have the time. My convictions are based on the simple rules that govern the universe. You can't escape the laws of physics unless you are in a parallel universe or black hole to my knowledge. Yes, there are more important factors, crown size, etc..but all things being the same (rake, steer tube, crown) a curve by simple/basic rules of Science will dissipate more energy. So if we could build 2 identical units with the only variance being the curve, the straight fork would feel more rigid. (mostly in vibration to the rider). That is the nature of things in this world. You could make a flimsy straight fork by altering material, hell use tin for the crown that would be more compliant than anything, but once again it avoids the argument. It's also self evident that frame builders etc.. can alter parts of a fork to change it's performance but again that's like saying suspension forks are staright and their more compliant than anything. We need all other variables removed for the experiment to be accurate.
RE: your red frames/blue frames, that non-point only insults your intelligence.
Seriously folks, do the wind chime test. Vibration (Sound) is the simplest form of energy to test this theory. Buy two identical sets at the swap meet, etc... cost ya about 10 bucks. Keep one straight (control group) and slightly bend the others. Now ring them, which sustains longer? Which produces more sound? the answer shows which is the better conduit for transmitting vibration (Energy). The more you bend, the less sound they will produce.
Yes, I've done this experiment, with a 5th grade class I was teaching. This is rudimentary science, I'm so suprised no one out there has done this, or anything like it in school, and I'm not talking about college. It's the basis for the xylophone, tubular bells, etc... and it all comes down to very simple physics. If this other gentleman hadn't called basic physics PSEUDO Science he wouldn't have created this diatribe in the first place. He never presented any science whatsoever, so who's being Scientific?
I knew (see first post) that this would start a flame and still no one produces the Scientific reason tht a fork somehow escapes the rules that govern our universe. Please, if you can enlighten me I'd be most appreciative.
Feb 20, 2003 7:37 PM
|so I'm on a roadie with 2 friends this morning. We're checking our bikes out and you know what I noticed? Ovalized and Bi-Ovalized tubing. Funny this whole concept revolves around the same principles of math and science I've been referring to. Flattening the tubes to stiffen them in certain directions against pedaling torque (BB), handlebar torque (headtube) etc.... Marketing Hype? So any of you nay-sayers inspect your frames and sell them if they have such pseudo scientific abominations of pure marketing hype. It's funny, I was inspecting my friends Prince and I noticed the chainstays are actually ovalized on a vertical axis. I think this strange as a vertical oval would stiffen against vertical loads (road vibration) and be flexible against horizontal loads (pedaling torque), which is the opposite of what you want and would negate any of the positive affects of carbon seat stays (if there are any). So I look up a reveiw (Bicycling TdF Issue Y2K) where they reviewed the bikes of the pros. Their conclusion, the Prince had a suprisingly stiffer rear triangle than most CF seat stayed bikes. Hmmmmm am I psychic? or do I just draw reasonable conclusions based on ....what did Thomas Dolby say?
Back to round tubes and a flat world, all of ya.
|straight leg fork||SJT|
Feb 13, 2003 6:38 AM
|Well due to my finances I will be getting a curved fork, the Dimension disc cross fork. I would have prefered a lighter, hand-built fork, but too costly for me right now. I'm trying to keep the cost of the bike build at $1500 or less. The Dimension forks are supposed to be a little heavy, but I'm not racing this bike so I hope I won't really notice.
|some more specs||SJT|
Feb 13, 2003 6:35 AM
|I believe I'll go with a traditional chainstay length (42.5cm?), with a 11" BB drop, breezer style drop outs (I can ask Doug if he has interchangeable drop outs...those would be cool), bent seat stays, and tube diameter will be set by Doug...I don't know. Thanks for the help though, I'm trying not to miss anything.
|What color scheme?||buffalosorrow|
Feb 12, 2003 4:45 PM
|Nothing complements a custom frame better than color choice and components.|
|What color scheme?||SJT|
Feb 13, 2003 6:31 AM
|Not sure on the color yet. Probably will go with a cool color like limelight green or maybe a sunny day yellow (see colors on link). The fork will be black because that is how the Dimension disc forks come. I guess I could have that custom painted as well, but I don't mind a black fork (my girlfriend has a red bike with a black rigid fork and it looks great). I have about two weeks to decide on the color though. Heres the link to my color options: http://strongframes.com/frames/colors/
BTW- The bike is being built by Curtlo, but Strong paints his frames
|What color scheme?||buffalosorrow|
Feb 15, 2003 1:59 PM
|From deesidecycles UK, I ordered a custom orange to black fade, black fork. I get lots of complimets, solid frame and good color choice. From the strong frame site the colors seemed to be on the flat side, any of the blues/ greys along with gloss black would look great.
I would upload an image but I had to initalaze my hard drive an re-install everything, at a loss though.
|What color scheme?||kilimanjaro|
Feb 17, 2003 9:45 AM
|Is your custom deeside aluminum or steel? If it is steel can you tell me if the welds are smoothed out. I would love to see the picutre when you get the chance.|
|custom deeside aka graham weigh||buffalosorrow|
Feb 22, 2003 7:17 AM
|reynolds 531 main tubes, and a tear drop 853 down tube. This makes the frame sub 4 lbs. If I were to compare the welds to an IF or colnago, they are of lesser finishing time spent. A little spatter leftover although smothed out to an acceptable finish.
My good friend and I both order custom frames, mine a custom cross, and his a custom 853 hex road bike. He has crashed the frame a number of times, no welds have ever broke. The seat stay is now curved from an accident, but the frame rides true and wheelset has lasted....its amazing. He is thinking of sending it back to deeside to have straightened and repainted.
I would send a photo but my scanner needs to be re-installed and I am having difficulty doing so. Both frames are heavily commuted on 1000 miles plus on each bike, I also raced mine as a single speed for the previous season, because I did not have enough money to set my colnago up.
For the price you can not beat it. I will look through saved emails with images form deeside.
|re: Going custom, did I forget anything? Here's my list...||Ash|
Feb 13, 2003 10:10 AM
|What happens if your discs crap out. With no bosses for cantis, you are down till your discs get fixed. Just a thought. This sounds like your do it all machine, and I think being versatile to go cantis or disc at a moments notice might be nice.
Don't they make screw in bosses that are easy to remove?
Will the sloping top tube cut into your shouldering room. It depends on the TT length but keep that in mind
BB height (BBdrop) affects the ride a lot, and if you add on big cross tires, it raises you up even more. Depending on how much of your time is spent on the road, vs trail this might be an issue
|re: tire size, BB height and standover.||atpjunkie|
Feb 13, 2003 6:42 PM
|make sure you have jewel space with a high BB and big tires
sloping TT will help
|re: Going custom, did I forget anything? Here's my list...||xcandrew|
Feb 17, 2003 2:00 AM
|Some minor things that I noticed:
With a forward facing seat clamp, the difference between cc and ct will be more than 2 cm if ct is measured to the top of the seat tube, so you probably want 54 cc OR 56 ct.
With a 56 top tube and 12 stem, the saddle nose to bar will probably be a lot longer than 50.2 cm nose to bar unless you have a super stubby saddle.
I like under bb cable routing because it looks cleaner to me and it keeps water (and rust) out of the rear derailleur cable housing, but other people like tt routing - it's your choice.
Make sure to specify bb drop... bb height depends on tire size, so bb drop more precisely defines how you want the frame.
If you want a lot of mud clearance and really big tires, it will be easier to get everything to fit with longer chainstays, which are nice.
No chainstay bridge for mud clearance, though if you want fenders...
You mean rack braze-ons on the seat stays? You mentioned fenders, so double eyelets on the dropouts.
Since it is custom, make sure to have the frame built around the fork that you want. The fork length will affect some of the measurements: the angles, head tube length, bb drop.
I don't know how you are measuring stem height, but if you specify stem drop from top the of saddle, it would be easy for the framebuilder to design around that knowing your saddle height (where you want it... why "max"?).
|re: Going custom, did I forget anything? Here's my list...||SJT|
Feb 20, 2003 6:58 AM
|Sorry I didn't respond earlier. I need to bring up your concerns with my builder the next time we speek. There are obviously a few things we need to iron out before he starts cutting the pipes. I don't have answers to most of your questions, but plan to this week. Thanks, I really appreciate you post.