Frame with no seatstay or chainstay bridge?
05-01-12, 11:23 AM
#51
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IMO all else being equal, the addition of a chainstay bridge should certainly make a frame laterally stiffer.
The chainstays and axle don't form a triangle. The chainstays, axle and BB form a trapezoid. Add a chainstay bridge and that's divided into two smaller trapezoids. I'd be flabbergasted if empirical testing showed a neglible difference if you hack a chainstay bridge out.
The chainstays and axle don't form a triangle. The chainstays, axle and BB form a trapezoid. Add a chainstay bridge and that's divided into two smaller trapezoids. I'd be flabbergasted if empirical testing showed a neglible difference if you hack a chainstay bridge out.
05-01-12, 11:59 AM
#52
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Subjectively. After you'd expended effort cutting up the frame 
05-01-12, 05:29 PM
#53
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This is why I find this topic so interesting - it is counter-intuitive. But in your experiment you're applying forces the bike would never see while being ridden. As long as you've got a test specimen now though, see if you can make the thing exhibit "torsional flex" with and without the wheel in there.
I have broken a frame AT the chainstay bridge. Probably damage from welding, it was a cheap Sekai.
Not hard, but wrong, beyond any trivial effect.
Maybe want to run bigger tires. Maybe want to experiment. One reason NOT to cut out the chainstay bridge is because you want a flexier frame... won't help. The OP asked if lacking a chainstay bridge or seat bridge would be a reason to reject the bike and we kind of ran with it from there.
BTW, besides the fender mounting, the chainstay bridge helps keep the tire from getting stuck in there with horizontal forward dropouts and frantic wheel changes.
I have broken a frame AT the chainstay bridge. Probably damage from welding, it was a cheap Sekai.
Not hard, but wrong, beyond any trivial effect.
Maybe want to run bigger tires. Maybe want to experiment. One reason NOT to cut out the chainstay bridge is because you want a flexier frame... won't help. The OP asked if lacking a chainstay bridge or seat bridge would be a reason to reject the bike and we kind of ran with it from there.
BTW, besides the fender mounting, the chainstay bridge helps keep the tire from getting stuck in there with horizontal forward dropouts and frantic wheel changes.
Frames with bridges are found on the more "serious" bikes that are more likely to be ridden hard.
I certainly wouldn't cut out a bridge on a frame that has one. A frame CAN be designed not to need one but if it has one then it's integral to the design. They wouldn't go through the trouble and expense to put one in if they thought it wasn't necessary.
In my experience, a tire will rub on the brake caliper before it will rub on the chainstay bridge. But, you could be running no back brake.
05-01-12, 05:49 PM
#54
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That is simply incorrect. I don't care what you buy, and I don't care if you believe me, but you're wrong about this.
Last edited by DiabloScott; 05-01-12 at 05:56 PM.
05-01-12, 07:13 PM
#55
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You're creating a fallacy here. You're showing photos of reputable frames that don't have a chainstay bridge with the inference that they are not needed on any frame.
Like I said, they wouldn't go through the trouble and expense of putting one in if the design didn't depend on it.
05-01-12, 07:28 PM
#57
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05-01-12, 08:23 PM
#58
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My three recumbents all have bridges on the "chainstays". On the short wheelbase V-Rex, it seems, maybe, to serve a structural purpose, as the "chainstays" run a full three feet from the dropouts to the head tube. On the tandem and long wheelbase bikes, they would appear to exist primarily for use with brakes or fenders. Much as on many diamond frame bikes, I imagine.
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05-01-12, 09:11 PM
#59
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Don Walker... Richard Sachs... you think these guys are cutting costs?
Last edited by DiabloScott; 05-01-12 at 10:45 PM.
05-01-12, 09:51 PM
#60
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Steel is a strong enough metal that I suppose an engineer could design a frame with enough strength/stiffness in the right places that it wouldn't need bridges. I don't know if that's the case with the OP's frame, or how heavy it would be, but I can't help but think steel is strong enough that it could be done.
05-01-12, 09:56 PM
#61
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You're talking about expensive hand crafted frames, I'm talking about run of the mill, mass produced frames.
Again, you're using the same ploy to infer that no frame needs a chainstay bridge, even if it comes with one.
Notice the lug on the second photo, the lug forms a bridge.
Again, you're using the same ploy to infer that no frame needs a chainstay bridge, even if it comes with one.
Notice the lug on the second photo, the lug forms a bridge.
05-01-12, 09:56 PM
#62
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More cheap frames:
I'm sure the chainstay bridge isn't needed at all on properly designed and built frames. Don't have any experience on frames w/o seatstay bridges, but I think Diablo is right, at least for disc brakes or no rear brake.
I'm sure the chainstay bridge isn't needed at all on properly designed and built frames. Don't have any experience on frames w/o seatstay bridges, but I think Diablo is right, at least for disc brakes or no rear brake.
05-01-12, 10:39 PM
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Maybe a frame builder can answer this one - Is it possible that some builders make a rear assembly of the four stays by sort of tacking them together at the bridges before they weld or braze onto the frame? That would answer a lot of questions.
Last edited by DiabloScott; 05-01-12 at 11:04 PM.
05-03-12, 01:39 AM
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My '95 Giant CFR1 had no chainstay bridge (carbon tubes, ally lugs, wishbone seatstay); it was a bit of a noodle. Taught me to spin.
05-03-12, 08:52 AM
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Your claim: The lack of chainstay bridges is to save money on cheap frames which aren't ridden hard or meant to be.
Your evidence: cheap frames which aren't ridden hard or meant to be which lack a chainstay bridge.
Someone showed contrary evidence: expensive frames which are ridden hard, and meant to be, without a chainstay bridge, and your response is "well, I'm not talking about those!"
EDIT: and that's not the inference anyone is trying to make, and it's no 'ploy', just a discussion.
05-03-12, 11:35 AM
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My frame's aluminum, other than the carbon seatstays.
05-03-12, 11:45 AM
#67
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when I learned to build frames back in the '70s, there wasn't any question about bridges, we put them in. Since then, some of the newer tubing doesn't do all that well with the stress riser imposed by the chainstay bridge. This was a hard lesson learned by many builders who ended up with broken frames. Now I have to convince myself to put a chainstay bridge in because of this issue. I usually do anyway so I can mount fenders. I have thought about just putting a cantilever beam off of one stay for this, maybe I'll do that on the next build.
Leaving off the brake bridge is a little weird, but I don't think it will hurt anything on a bike with a modern tubeset. The bridge does protect a little against bending in a crash, but high strength modern steel tubes are not that likely to bend unless it's a really bad hit. And then it's likely that you only have to replace one stay.
Leaving off the brake bridge is a little weird, but I don't think it will hurt anything on a bike with a modern tubeset. The bridge does protect a little against bending in a crash, but high strength modern steel tubes are not that likely to bend unless it's a really bad hit. And then it's likely that you only have to replace one stay.
05-03-12, 05:45 PM
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I have a Surly Karate Monkey; mass produced, not high end, but certainly meant to be ridden "hard". It has no chainstay bridge (which makes it a bit of a pain to fender). No ploy here, just another piece of evidence.
06-28-12, 01:25 PM
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New entry into the bridgeless seat stay design - Trek Madone 7:
Brakes are behind the BB.
Brakes are behind the BB.
06-28-12, 01:51 PM
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Having worked on a number of Cervelos set up this way over the last few years, I think this ranks up there with some of the dumbest ideas that should have never proliferated, but as is so often the case, being cool trumps being smart.
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06-28-12, 01:54 PM
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Is there some issue besides the brakes getting mucked up with road grime and other slop? This is a $10,000 bike... probably won't see such abuse.
06-28-12, 02:45 PM
#72
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It's just that this is a crowded area, what with the cranks there. So it just makes everything, including simply replacing brake shoes that much harder. It also depends on how the entire brake is mounted, Cervelo made it harder than it had to be.
Bottom brackets and chainstays have been there forever, and it's such a handy place to put the brake, all out of the way and all that, it makes you wonder how somebody didn't think of this 100 years ago. Fact is they did, and stopped for a reason. As I said, it's more about being cool, than being smart, though I'm sure that Trek validating this bit of nonsense, others will follow, proving once again that no idea is ever to dumb to be copied.
Bottom brackets and chainstays have been there forever, and it's such a handy place to put the brake, all out of the way and all that, it makes you wonder how somebody didn't think of this 100 years ago. Fact is they did, and stopped for a reason. As I said, it's more about being cool, than being smart, though I'm sure that Trek validating this bit of nonsense, others will follow, proving once again that no idea is ever to dumb to be copied.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
06-28-12, 02:52 PM
#73
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I agree with the fact that bridges are not structural. But the seatstay bridge might be a good idea to keep for canti/V brake, as well on lugged stell frames (as most of them have a somewhat weak braze between seatstays and top of the seat tube, like those are not lugged are just face brazed)
06-28-12, 03:11 PM
#74
Banned
Yea but, you wash down the bike after every day of racing, Scott, FB,
or the team mechanics take over.. so It does not accumulate.
I think that is on a time trial bike so It does not see as much time on the road as a regular stage .
[ + bike section of a triathlon , is only 1/3rd]
or the team mechanics take over.. so It does not accumulate.
I think that is on a time trial bike so It does not see as much time on the road as a regular stage .
[ + bike section of a triathlon , is only 1/3rd]
Last edited by fietsbob; 06-28-12 at 03:15 PM.
06-28-12, 03:11 PM
#75
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Oh good point. Trek calls this an "integrated brake" which makes me think ease of service wasn't driving the decision. I'll bet all the adjustments are a PITA.