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Discussion Starter · #1 ·
Can someone give a run down on general frame geometry theory? In other words, what makes a bike feel certain ways or do certain things?

1. What make a frame/fork comfortable over bumps for long periods of time?

2. What makes a bike track easily vs. quick handling?

3. Do long chain stays hurt climbing ability?

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

5. Do curved seat stays really have any effect on comfort?

Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.

Doug
 

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same Doug Sloan??

DougSloan said:
Can someone give a run down on general frame geometry theory? In other words, what makes a bike feel certain ways or do certain things?

1. What make a frame/fork comfortable over bumps for long periods of time?

2. What makes a bike track easily vs. quick handling?

3. Do long chain stays hurt climbing ability?

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

5. Do curved seat stays really have any effect on comfort?

Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.

Doug
Are you the same Doug sloan who's been posting on this site for a long time? If so, haven't you read about the effects of rake and trail many times before?

You need to be more specific. If you have something specific in mind that you like or dislike about a current bike, it would be easier to addresss those problems.

Generalized statements are not too valuable. The customs builders websites should include accurate information. I don't know why you would suspect their accuracy and trust info from unknown sources here.
 

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C-40 said:
Generalized statements are not too valuable.
So here are some generalized statements! :)

Longer wheelbase, longer chainstays, and shallower head tube and seat tube angles will make a bike more stable (century bike). Steeper angles, shorter chainstays and wheelbase will make it more responsive (criterium bike). I think that a lower bottom bracket will also make the bike more stable (since the BB 'hangs' below the hubs) at the expense of cornering clearance.

IMHO, I doubt that curved stays really flex enough to noticeably change the ride quality.
 

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my conclusions

DougSloan said:
Can someone give a run down on general frame geometry theory? In other words, what makes a bike feel certain ways or do certain things?

1. What make a frame/fork comfortable over bumps for long periods of time?

2. What makes a bike track easily vs. quick handling?

3. Do long chain stays hurt climbing ability?

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

5. Do curved seat stays really have any effect on comfort?

Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.

Doug
1. A longer wheel base and a lower bottom bracket.

2. Anything that moves the front wheel back makes bikes handle quicker and vice versa. I suspect there's a limited range within which both tracking and handling are acceptable, but I don't know what that range is.

3. I don't notice chainstay length mattering much on climbs. I suspect between sliding around on the seat and standing up, I make any differences that might exist disappear.

4. I haven't had seat tube angles so different that I couldn't slide my seat to the same place relative to the bottom bracket. The difference between 72.5 and 74 degrees moves the seat a pretty small amount.

5. No experience with curved stays.
 

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The first issue of Asphalt..

has a very good article on frame specs that answers all of your questions in detail. If you really want a detailed (i.e. 10 pages or so) answer, buy it. Its a keeper.

The common misconception on the above posts is on the all important trail. But, as c40 said, that's been discussed before. It ain't just head tube angle......
 

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Trust me, it will hurt if you get run down

1. What make a frame/fork comfortable over bumps for long periods of time?
answer: I try to ride over bumps for only short periods of time
2. What makes a bike track easily vs. quick handling?
answer: A bent bike does neither well. Remember. If it's bent. you must repent.
3. Do long chain stays hurt climbing ability?
answer: Only if they are 12 inches longer than usual
4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?
answer: Yes and Yes.
5. Do curved seat stays really have any effect on comfort?
answer: Only for the owners of the bike companies.
Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.
answer: Live crazy, die young........Repeat......Repeat.
 

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I had many similar design goals for the Vanilla that Sacha is building for me since one of the uses for the bike will be long brevet rides. Here are some of the design choices we settled on, which don't directly address your questions.

Steel fork with curved blades. Sacha acknowledged the conventional wisdom that there is no difference between straight & curved blades, but his opinion was that curved blades do give a smoother ride.

For combined stiff climbing and smoother-feeling ride at the bars, the downtube is tapered from 1-1/8" diameter at the headtube to 1-1/4" diameter at the BB.

The horizontal drops will let me vary wheelbase to, in theory, get a smoother ride with a longer wheelbase.

We did not discuss it directly as affecting ride feel, but the bike will have a 1 inch headset/headtube, which I suspect might be a bit smoother than a 1-1/8 headsetheadtube. It will also have a custom steel stem (quill), which might not differ from an Al quill, but will be smaller diameter than most threadless stems.

I'll be using a carbon Kestrel bar (26 mm).

Good luck in your planning. Let us know what you settle on.
 

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Well I'm sure that you will find the above to be of use to you Doug.

I was quite surprised at how much difference a 73' STA made as opposed to the 74's that I've previously had. The 73 was on a cheap LeMond Nevada City and climbing in the saddle was so much better. Wish I kept it but now I'm going to try to get a custom frame built with similar angles but traditional lugged steel.
 

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I too do not trust the average builder...

DougSloan said:
I don't trust builders to tell me everything, as they seem to say whatever suits what their style is.

Doug

I've been trying to get answers regarding appropriate trail for mtb and have contacted various builders directly. As a whole, their web sites are remarkably lacking in content. Lennard Zinn and the folks at Seven answered my questions intelligently and in a way that was constructive. Frankly, after my conversation with Moots and Merlin I would never buy a bike from them again (and I have in the past). Once you get comfortable with a concept -- say trail for instance -- quiz your prospective builder on their insights and opinions and you'll quickly be able to distinquish the thinkers from the imitators...

Okay, so here are my opinions on your questions:

1. I believe that a shallower head tube angle (72 degrees) coupled with a greater fork rake (50 mm) will be more comfortable and track over bumps better than a steeper head tube angle (73.5 degrees) coupled with a fork of less rake (41 mm). Note that both bikes have a trail of about 56 mm with a 700 X 23c wheel/tire. They will have the same low speed handling, but the increased wheel base of the first frame and fork will make it more stable at speed.

2. See answer to number 1 -- it's all about trail. My opinion is that a trail from about 56 to 60 mm is what the average sized individual wants on their road bike. Anything longer and it drifts wide on corners and can dive in on you (wheel flop) at lower speeds.

3. While lacking empirical data, I do not believe that long chain stays hurt on climbs, particularly long seated climbs in the mountains. I am, however, of the opinion that short intense efforts (say sprinting or really busting up a short hill) don't deliver as much umph on a bike with longer chainstays as you would get from the same effort on a bike with shorter chainstays.

4. A shallower seat tube angle (72 degrees) only means I don't have to run my seat jammed all the way back (forward on the rails) as I do when I have a steeper seat tube angle (74 degrees). Either work -- my hips end up in the same place relative to the bottom bracket spindle.

5. I do not believe that curved seat stays affect comfort, but I do like their asthetic value. Curved chain stays help on heel clearance.

Good luck and as always YMMV
 

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Vanilla

When do you expect it? He's shipping mine today - those intervening months sped by, I can't wait to have it in hand.

True Temper S3, pretty straight racing geometry.
 

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Discussion Starter · #11 ·
custom builders

terry b said:
When do you expect it? He's shipping mine today - those intervening months sped by, I can't wait to have it in hand.

True Temper S3, pretty straight racing geometry.
I emailed Vanilla about a month ago about building a bike for me and they never responded. As this was before I spent 2 weeks there, it would have been nice to get started on a project. I suppose it could have been an email glitch, but I more strongly suspect it's the flakey nature of these custom builders. That's why I'm leaning more toward an off the shelf bike, rather than put up with delays and flakiness.

Doug
 

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terry b said:
When do you expect it? He's shipping mine today - those intervening months sped by, I can't wait to have it in hand.

True Temper S3, pretty straight racing geometry.
Not sure yet when mine will be done. The painter is backed up. I think it will be a couple weeks yet. Be sure to post photos of yours when it arrives.

The last time I was there he had another brevet-style bike in the works with fancy sculpting of the lugs and built-in racks. I'll be pretty plain with regular Henry James lugs.

Doug, sorry to hear that you didn't connect with Sacha. He's MUCH more of a catch-him-on-the-phone kind of guy than an email kind of guy. I'm sure he'd be glad to have you stop by to see him with a call ahead of time. It's worth it just to see what bike he's working on at the time.

For something this season, John Slawta at Landshark might have a quicker turnaround. Great brazed frames, ridden to victory by Andy Hampsten in the Giro, if I have my details right. Gary at gvhbikes.com has the best Landshark prices.
 

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Try Strong Frames (www.strongframes.com)

You will find that he will return your call or email promptly, that he is more than an average builder, and that he won't blow smoke up your a$$. Carl is straightforward and plainspoken. There is no hype around Strong Frames, Carl's reputation is his frames, not his name. He does Ti, Steel, and Aluminum (including Scandium if that's your preference).

That said, I have nothing bad to say about Vanilla, Moots, Seven, etc.

Disclosure: I know Carl well, and have been riding his bikes for several years both on and off-road.

Best and good luck,

Michael
 

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Doug -

I'm with you on the apparent flakey nature of some of these guys. But then, the whole "why have email if you're not going to answer it" seems to be a common denominator among many of these small businesses. Personally, I like to do email first, as I hate talking on the phone. I send one off and see if they respond. Often they don't and I go elsewhere, immediately. Good example is oddsandendos from whom I really wanted to to buy some wheels. Repeated emails - no answer, no sale.

Sacha though did answer my initial email right away, so I was hooked. I only asked about delivery dates and confimation on price, nothing technical. Figured I needed to cover my design requirements on the phone. I will say though while he is less communicative than some, I've really enjoyed working with him once I got past doing it exclusively on the phone. At the other end of the spectrum is Carl Strong who answers his email and phone messages often within minutes. He's willing to sit and jaw about the questions you asked above - eternally. From my experience, I'd highly recommend both.

You might want to consider giving him a second shot (or talk to Carl.) Both will build you a fantastic bike for a very reasonable amount of money (at least in comparison to the price range I know you've bought from in the past.) Custom is a blast - not a necessity, but an awful lot of fun. And, you'll have their answers to your question which might result in a frame that embodies what you're after.
 

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Vanilla

I'll post some pix when it gets here. I'm expecting it Monday.

Agree with you on Sacha's communication style - he was always willing to spend the time on the phone. Also I appreciated his low-pressure approach - was willing to do what I wanted to do with good suggestions. I felt I was getting a straight answer all the time.
 

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DougSloan said:
Can someone give a run down on general frame geometry theory? In other words, what makes a bike feel certain ways or do certain things?

1. What make a frame/fork comfortable over bumps for long periods of time?

Doug
For comfort, have you considered one of the Softride bikes. The suspended beam makes them very comfortable over bumps.

Also, recumbents are exceedingly comfortable.
 

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1. What make a frame/fork comfortable over bumps for long periods of time?

Your butt shouldn't be right over the rear wheel, and your weight should be distributed so that you're not putting too much weight on the bars.

2. What makes a bike track easily vs. quick handling?

Combo of wheelbase and trail.

3. Do long chain stays hurt climbing ability?

To me long c-stays feel like crap when you're climbing out of the saddle. I don't want anthing longer than 41.5 on a road bike, but much shorter than 41 is asking for trouble (see butt issue in #1).

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

The goal should be that when you have YOUR optimum saddle position relative to the cranks, your seat rails should be centered on a Campy-style post.

5. Do curved seat stays really have any effect on comfort?

They have a great placebo effect if you believe they do.
 

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Doug, since your in California you should contact Bernie Mikklesen in the East Bay. He can draw up a design and then set up his funky trial bike to let you try before you buy. He's kind of a nut. I also think he uses D&D paint, which is awesome--I have a bike painted by them which still looks new after 15 years.

http://www.mikkelsenframes.com/
 

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1. What make a frame/fork comfortable over bumps for long periods of time?

A long wheelbase. Long chainstays to keep you in well front of the rear bump center and a slack HTA with appropriate offset on the fork. The further your weight-bearing contact points are from the bump centers of the wheels, the more comfortable the ride will be. You also don't want a bike that is too laterally stiff. A little BB sway helps comfort. Strange but true.

2. What makes a bike track easily vs. quick handling?

A combination of HTA, offset, and acheived trail. If you're looking for a loaded touring bike, a lower trail number helps offset the slowing affect front panniers have on steering and helps make the bike more stable when you're climbing at a snail's pace. If you want a stable sport bike, then shoot for a trail of between 57 & 59 depending on how much weight you have on the bars (positioning related).

3. Do long chain stays hurt climbing ability?

Not directly. Excessive lateral flex in the chainstays/BB and lack of traction hurts climbing ability. If the rear end is appropriately stiff, then it's just a matter of keeping the rear wheel loaded to maintain traction. Think MTB'ing. As far as excessive lateral flex, look at it this way: if you used the same stays to build a bike with 440mm chainstays as you do with 405mm chainstays, you've significantly increased the bending moment on the stay without increasing its stiffness. Appropriate bridging can help here, but the answer is to use tubes appropriate to the load.

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

STA should be dependent on your fit & knee to pedal spindle preference criteria. Different angles do have an effect on bike design, at least from a custom frame perspective. A slacker STA will, if your body move with it, will move your CG rearward. A steeper STA moves it forward. A slack STA requires longer chainstays to maintain the appropriate CG. Steeper STA requires shorter chainstays. STA angle also has an effect on cockpit length.

5. Do curved seat stays really have any effect on comfort?

Depends on the design. If you take seatstay out of pure compression then you can start to achieve some movement. It helps to have a pivot point, but introduce enough of a bend in the stays and you will start to achieve some compliance. A nice, fat, set of tires at appropriate air pressure helps too.

Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.

You say that like you think they'll intentionally mislead you. Why would you buy from a builder you don't believe in? Better yet, why would place more belief in the opinions you read on the internet vs. those of somebody who earns their crust by working to achieve the answers to the questions you're asking?
 

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Discussion Starter · #20 ·
thanks

Anvil said:
1. What make a frame/fork comfortable over bumps for long periods of time?

A long wheelbase. Long chainstays to keep you in well front of the rear bump center and a slack HTA with appropriate offset on the fork. The further your weight-bearing contact points are from the bump centers of the wheels, the more comfortable the ride will be. You also don't want a bike that is too laterally stiff. A little BB sway helps comfort. Strange but true.

2. What makes a bike track easily vs. quick handling?

A combination of HTA, offset, and acheived trail. If you're looking for a loaded touring bike, a lower trail number helps offset the slowing affect front panniers have on steering and helps make the bike more stable when you're climbing at a snail's pace. If you want a stable sport bike, then shoot for a trail of between 57 & 59 depending on how much weight you have on the bars (positioning related).

3. Do long chain stays hurt climbing ability?

Not directly. Excessive lateral flex in the chainstays/BB and lack of traction hurts climbing ability. If the rear end is appropriately stiff, then it's just a matter of keeping the rear wheel loaded to maintain traction. Think MTB'ing. As far as excessive lateral flex, look at it this way: if you used the same stays to build a bike with 440mm chainstays as you do with 405mm chainstays, you've significantly increased the bending moment on the stay without increasing its stiffness. Appropriate bridging can help here, but the answer is to use tubes appropriate to the load.

4. Does seat tube angle depend primarily on your anatomy, or will different angles acheive different things for a particular person?

STA should be dependent on your fit & knee to pedal spindle preference criteria. Different angles do have an effect on bike design, at least from a custom frame perspective. A slacker STA will, if your body move with it, will move your CG rearward. A steeper STA moves it forward. A slack STA requires longer chainstays to maintain the appropriate CG. Steeper STA requires shorter chainstays. STA angle also has an effect on cockpit length.

5. Do curved seat stays really have any effect on comfort?

Depends on the design. If you take seatstay out of pure compression then you can start to achieve some movement. It helps to have a pivot point, but introduce enough of a bend in the stays and you will start to achieve some compliance. A nice, fat, set of tires at appropriate air pressure helps too.

Any other issues or comments would be appreciated. I'm thinking of a custom frame, and want to be fully, but objectively, informed. I don't trust builders to tell me everything, as they seem to say whatever suits what their style is. Thanks.

You say that like you think they'll intentionally mislead you. Why would you buy from a builder you don't believe in? Better yet, why would place more belief in the opinions you read on the internet vs. those of somebody who earns their crust by working to achieve the answers to the questions you're asking?
I had forgotten about all the help you used you provide at the old site. Good stuff (others, too).

I'll email you about what I'm thinking for this project. Thanks.

Doug
 
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