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  1. #1
    dru
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    Tubing choice for road frame?

    Here's the plans for the second frame. I've hopefully dialed in my choices for tubing and would like your opinions.

    My 1st mountain frame was mostly True Temper VHT and I was working in wall thicknesses of 8/5/8 for the most part.

    The road frame is speced for mostly OX platinum in thicknesses of 7/4/7. (exceptions like the ST of course, 16 mm SS, etc)

    I'm confident in my ability to braze it since it is only a tiny bit thinner than the 1st frame.

    Since it is a road frame I went with a 31.8 DT. Ditto on the TT.

    Will this frame be too stiff still for my weight of ~180 lbs because of the OX, or too flexy because of the long tubes?

    Opinions?




    Drew
    occasional cyclist

  2. #2
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    (In my newbie opinion) I'd stay away from 7/4/7 tubes, not a lot of difference in thickness, but much bigger chance of screw up during brazing. Also, you might be pretty light, but that's a big frame, not a bad idea to stay away from really light stuff.

  3. #3
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    I am a newbie too - and have built two road frames, one tigged and one brazed. My frames are close to the same size as the one in the drawing (590tt, 200mm HT), but a tiny bit smaller. For reference, I am 6'2" and about 175 - close to your same weight.

    The first frame I built with a cheap oversize Nova 8/5/8 tubeset - 31.8 DT, 28.6tt, whatever chainstays and seatstays it came with. The frame was fillet brazed. It rides nice and is fairly stiff, however it ended up being very heavy (4.7 pounds). The BB is nice and stiff when sprinting, climbing, etc. however the HT/TT/DT is just a little less stiff than the carbon bike I ride (which is super stiff in that area) and is just barely noticeable. Rides pretty nice, just heavy and kind of dead feeling - not a nice awesome springy steel ride.

    The second frame I built was Tigged with Columbus tubing - 7/4/7, 31.8tt and 35dt, life seatube, life stays, columbus headtube (I think it was the 1.0 36mm but can not recall exactly) The frame ended up at 3.76 pounds, however is not stiff enough in the HT/DT/TT area. The front of the frame is pretty flexy - noticeably more than the other frame. It is a bit of a handful when riding hard and pushing it. The BB area is nice and stiff and the frame spints well, and the ride is nice - just the front end is not as stiff as I would like.

    On the second frame I am not sure what the major difference was and why the front is not solid - may be the long thin walled headtube - or the thinner columbus tubes - or a combination of different things. I hope this was helpful - again, super newbie here but have a little info on almost the same thing you are doing!

  4. #4
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    Another newbie opinion. I'm 160 lbs and ride a steel Lemond frame with a 57 cm TT. The frame is Reynolds 853 with 28.6/28.6/31.8 Tubes. Not sure of the thicknesses. It rides just right for me, springy but not flexy.

    I'm a little confused by Tamen00's experience. I've always thought that tube diameter was the biggest driver of frame stiffness and wall thickness was selected based mostly on material properties (thicker if it's 110 ksi, thinner it's 180 ksi or whatever). Obviously all sorts of factors play into it like rider weight, frame size, riding style, etc. I would never guess that a 28.6TT/31.8DT 8/5/8 bike would be more stiff than a 31.8TT/35/DT 7/4/7.

    Thanks for posting this. I have a lot to learn about this stuff and am intrigued by frame designs and tubing selection. One thing I noticed on your drawing. For fillet brazing, you may want a little more than 10mm of head tube "stick up" above the TT. You could even give you self some more room on the bottom. Looking at some pictures on the web it looks like most frames have 20 to 35mm on this dimension. This will also help your HT not look so long. Just a thought.

  5. #5
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    That's right.

    Tube diameter is the main driver of stiffness. Wall thickness has an effect as well, but it's tiny in comparison, so the aforementioned Columbus frame should, on paper, be stiffer. It is possible that it's built up with different parts, or a slightly different geometry, or that the rider *expected* it to feel flexy for whatever reason and the placebo effect took over.

    -Walt

    Quote Originally Posted by Hooder
    Another newbie opinion. I'm 160 lbs and ride a steel Lemond frame with a 57 cm TT. The frame is Reynolds 853 with 28.6/28.6/31.8 Tubes. Not sure of the thicknesses. It rides just right for me, springy but not flexy.

    I'm a little confused by Tamen00's experience. I've always thought that tube diameter was the biggest driver of frame stiffness and wall thickness was selected based mostly on material properties (thicker if it's 110 ksi, thinner it's 180 ksi or whatever). Obviously all sorts of factors play into it like rider weight, frame size, riding style, etc. I would never guess that a 28.6TT/31.8DT 8/5/8 bike would be more stiff than a 31.8TT/35/DT 7/4/7.

    Thanks for posting this. I have a lot to learn about this stuff and am intrigued by frame designs and tubing selection. One thing I noticed on your drawing. For fillet brazing, you may want a little more than 10mm of head tube "stick up" above the TT. You could even give you self some more room on the bottom. Looking at some pictures on the web it looks like most frames have 20 to 35mm on this dimension. This will also help your HT not look so long. Just a thought.

  6. #6
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    Me again. This Carl Strong frame is a little smaller, but it would be interesting to see what the tube specs are and what rider size/strength that he was aiming for.

    http://www.strongframes.com/blog/201...l-on-frameset/

  7. #7
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    Quote Originally Posted by dru


    Dru, that's almost identical (geometry wise) to this frame I built myself (also my #2):


    BTW, I used the cheap Nova 9/6/9 on it because it was like $80 complete. I knew that I wanted to build another road frame later so as cheap as possible is what I did for this one. I'm hoping to have it replaced this year or before it rusts all the way through, whichever comes first.

    Looks good and I'm glad to see someone else not afraid of some head tube.

  8. #8
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    Quote Originally Posted by Walt
    Tube diameter is the main driver of stiffness. Wall thickness has an effect as well, but it's tiny in comparison, so the aforementioned Columbus frame should, on paper, be stiffer. It is possible that it's built up with different parts, or a slightly different geometry, or that the rider *expected* it to feel flexy for whatever reason and the placebo effect took over.

    -Walt
    Yeah - on paper the columbus frame should be stiffer - but there is a very noticeable difference in the two front ends. FWIW - when I built the second frame - every part from the first frame was moved over to the new frame. Also, the Geometry is identical on the two frames (other than the first frame is a little crooked ) and is identical to my carbon frame (I copied my current road bike). I did not expect the frame to feel flexy, I actually expected it to be stiffer than the first but the difference is pretty dramatic. Also, FWIW - the columbus tubes were all Life.

    I may have messed something else up on the build that is contributing to this - but I am not sure what it could be

  9. #9
    dru
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    Hmmmm..

    A lot of food for thought. Thanks for the input everyone.

    @tamen, a question for you; what length stem are you using, and are your bars 100 mm reach? I'm asking since I'm not 100 % on the TT length. My 1st frame is 647 mm and I'm running a 100 mm stem. It is a super comfortable mountain bike frame, so I took almost 2" off the TT length for the road frame to account for the fit of road bars. I'm wondering if 600 mm TT is a hair too long still?

    I'm sold on using OX in 7/4/7 so I'm wondering if I should bump the DT diameter to 34.9 from 31.8? My mountain frame is very compliant, almost cush. I'm sure that a stronger and bigger guy would find it a noodle. You guys seem to think I might have some flex issues with the front end?

    Of course I also don't want a pig as a road frame. The mountain frame was either 4.75 or 5 lbs depending on the scale, without paint.

    @walt, I followed your advice on tubing pretty closely last time and I couldn't be happer with my frame's handling. Hopefully I have the same luck this time.

    Drew
    Last edited by dru; 01-26-2011 at 04:01 PM.
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  10. #10
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    I would bump the downtube up to a 34.9 or 35, but I really like a bike with a stiff front end. When I build my next road frame it will have a 38mm OX downtube, tapered steerer/etc. (but that will not be for a while - when I am a better welder/builder!!)

    I mirrored my Gary Fisher Chronos Ultimate geometry for my builds - here are complete specs: http://fisherbikes.com/bike/model/cronus-ultimate.

    My Road bike Top tube is 578mm, stem is 110 with a -6 degree rise, Hbar drop is 135mm and reach is 85mm. The top tube on my mtb is 623mm and I run a 110mm -10 degree rise stem with low rise Hbars (easton EC70, I like the sweep of the bars, hence the negative rise stem and riser bars), 80mm suspension fork. The fit on both my road and mountain bikes are identical - reach, saddle to bar drop, saddle position, etc.

    Hope this helps!!

  11. #11
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    The difference between my road bike and mountain bike TT length is 1.6 inches. Same length stems, same difference in handlebar height compared to seat height. Looks like tamen is about 1.8 inch difference. I would say your in the ball park.

  12. #12
    dru
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    @tamen, I dabbled with the idea of 38 mm then found that TT doesn't make one long enough.

    Are your 85mm reach bars normal or are those considered 'short reach'? I want to dial my fit right in the middle if you know what I mean. The mountain bike can go either way with stem length. I want that flexibility on this frame too.

    I don't know much about road bikes, but I'm learning....

    Drew
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  13. #13
    dru
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    @hooder

    I'll be 47 mm shorter on the TT with this plan. I'm guessing I'll need a stem a fair bit shorter than the 100 mm on the mountain frame.

    Drew
    occasional cyclist

  14. #14
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    Makes you wish you could build it both ways and then see what you liked the best. I agonized over the DT for a snowbike that I just started. I ended up ordering two DTs, one 35 and one 38. After looking at them, I'm going to use the 35. The 38 just looks huge to me. Back in the day the standard road set up was 28.6ST/25.4TT/28.6DT. Now they have Over-sized road which is 28.6/28.6/31.8. Your thinking of going 28.6/31.8/35. Certainly there is a pro builder that could say for a 180 lb guy and 60cm frame I would use something like X. Maybe they don't want the liability?

  15. #15
    dru
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    No, the guys are cool here. I got the 'thumbs up' and also 'don't use that' in conversations last year. Walt (and the others) actually know the tubing when you post the part #......

    Drew
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  16. #16
    dru
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    Quote Originally Posted by jay_ntwr
    Looks good and I'm glad to see someone else not afraid of some head tube.
    It's funny, I've got grief about the HT length on the 26er which is only 185mm.

    Why would I build a bike that doesn't fit?

    I can't help that I'm a giraffe can I?

    Drew
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  17. #17
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    I agree with Walt and Hooder - The road frame I made should have been stiffer than my other steel road frames - I probably did something wrong that I can not identify, but when I figure it out I will let you know. I have a steel lugged frame with a 25.4tt and 28.6 dt reynolds 853 and 200mm HT that is stiffer in the front end. Please take what I have posted with a grain of salt on my current build because it is my second frame and something else could be wrong - the pro guys have all the right info!

    I am not sure what the normal road handlebar reach is - I have Bontrager XXX carbons and easton EA90slx's on the bikes and the manufacturer site says 85mm (however when I look at the itm site they claim 104mm reach on their bars)

  18. #18
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    Generally...

    If nobody on the board emphatically tells you that your idea is bad/dangerous/dumb, you can probably safely assume that your tubes are *safe*, or at least they are if you do a good job joining them. Whether they would be ideal or not depends on the application, rider, parts, etc.

    So for what it's worth, if I were building this frame for a customer like Dru, and they wanted a stiff frame, I'd probably do a 35mm DT/28.6 TT. If they wanted a less stiff frame, I'd do a 31.8 downtube/28.6 toptube. Or something like that. Either one, to be honest, will most likely ride fine.

    -Walt

    Quote Originally Posted by Hooder
    Makes you wish you could build it both ways and then see what you liked the best. I agonized over the DT for a snowbike that I just started. I ended up ordering two DTs, one 35 and one 38. After looking at them, I'm going to use the 35. The 38 just looks huge to me. Back in the day the standard road set up was 28.6ST/25.4TT/28.6DT. Now they have Over-sized road which is 28.6/28.6/31.8. Your thinking of going 28.6/31.8/35. Certainly there is a pro builder that could say for a 180 lb guy and 60cm frame I would use something like X. Maybe they don't want the liability?

  19. #19
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    That geometry is a bit horrible.

    First up, 50mm of rake is optimal for a 72.5 degree HTA. If you want to run a 73 degree HTA, go for something in the 43-45mm range. 48-50mm of rake feels terrible with a 73 degree HTA.

    405mm chainstays are way too short for a guy your size, you should be looking at 420 or so, because as the seat goes up, so your COG goes back and you need longer stays to compensate.

    A 32mm downtube would be fine if you had no stiffness aspirations. I'd still go with a 35mm for your size and weight, and even then I still often do 38mm DT's for guys lighter and shorter than you because the out of the saddle stiffness is worth the 30g.

    I'd like to know at least your inseam and saddle setback before I made any more sweeping generalisations
    No longer member of the bike industry nor society, so don't hassle me.

  20. #20
    dru
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    Quote Originally Posted by Thylacine
    I'd like to know at least your inseam and saddle setback before I made any more sweeping generalisations
    Have at it!

    My inseam is 38". My saddles are ~86 cm from the centre of the BB shell.

    The 26er I built runs a straight post with the saddle all the way back in the clamp.

    My Salsa 29er runs a straight post with ~20mm of offset at the clamp. I could move the Salsa's saddle back ~20 mm before running out of rail. It is roughly 2/3 of the way back

    Salsa seat angle is 73*, 26er SA is 72*

    Both bikes are set up roughly KOPS, no that I necessarily believe in KOPS, but it is a point of reference

    The reach for both bikes is within 1/2 " when measuring from the back or front of the saddles (2 different makes) to the bar clamp on the stems.. Measured from the straight section of the posts right below the rail clamps the reach is identical 29 1/2 ".

    The Salsa has a 635 mm horizontal TT length and runs a 6* 120 mm stem. 72* ha

    The 26er has a 647 mm TT and runs a 6* 100 mm stem. 70* ha.

    The Salsa runs a straight bar which are 3" below the saddle.

    The 26er runs a 1" riser which are 2" below the saddle.

    I absolutely love the fit of both bikes. I would not change a thing, although I am dabbling with the idea of running the 26er bars a hair lower.

    My only experience with 'road bikes' was a frankenbike conversion of the Salsa last season. The only way I could get even close to a decent fit was to run a 45* 65mm stem and a road bar with 90 mm of reach. Even so, I felt like I was reaching too much by about 10 or 15 mm when riding the hoods.

    I've given things a lot of thought (especially the paragraph above) over the past day or two and I've been thinking my TT length on the planned frame is at least 20 mm too long. Based on what I'm riding now I'm thinking 580 is better than 600. I've got to fit both a stem and ~ 85 mm of road bar reach into the TT length equation.

    Drew
    Last edited by dru; 01-27-2011 at 04:50 PM.
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  21. #21
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    Quote Originally Posted by dru
    It's funny, I've got grief about the HT length on the 26er which is only 185mm.

    Why would I build a bike that doesn't fit?

    I can't help that I'm a giraffe can I?

    Drew
    Yeah, it's enough to drive a guy crazy. Especially when the guy giving you grief has two inches of spacers under his stem....

    BTW, I think I ended up with like 405mm on my chainstays. The rear wheel is so tight that you couldn't get a banded derailleur in there--not that I wanted one, I was doing a braze on from the get go, just sayin'. I like the way it rides and I'd probably do it again but it's certainly different from the Spesh Allez I was riding before. As a MTBer primarily, it doesn't feel squirrely to me but I know it is. Or to say it another way, I can tell that the bike isn't as stable as my old road bike. I can still ride hands off the bars, do all the same stuff, etc. It does change direction quickly though and I like that. Maybe that's not "good" as far as road bikes are concerned, but it's cool feeling. I do notice that really hammering out of the saddle that the rear end can tend to jump around a bit though. Again, no biggie. The way I ride off road the rear end is always jumping around so it just suits my style. I wouldn't build one for someone else like that though--no chance.

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