Bicycle Mechanics - Danger of this frame modification?

my friend has a cheapo wallmart bike thing that he wants to mess around with. he's thinking about removing the seat tube and just having the thinner white tubes support the weight. he's also thinking about modifying the fender to support the rear of the bike. but all in all, is this a bad idea for him to be removing that seat tube?? im thinking its a bad idea, but thoughts from people in the know would be appreciated.

A Darwin Award candidate.

I'm no engineer, but I suspect the frame will collapse under his weight if he cuts out most of the seat tube (i.e., between the bottom bracket and the top tube). The seat stays just aren't designed to carry that much load.

this is a joke, right?:p

Geez, I wouldn't think a Wal Mart bike would be safe riden as is.

poor man's suspension??? .....bet it'll be a comfortable ride, but won't last long....

not even a funny joke!

The frame is made of not so resilient low carbon steel. It will be weak at best, since the frame is designed to have the seat tube be the load bearing member. With it not there, the trussing of the remaining tubes will kink most likely and at the very least the seat will have no lateral stability. Not a wise idea.

People have been doing that mod to low-rider bikes for years.

here's an example (http://lowriderbike.com/bike_features/cremator/)

That is in my opinion not an acurate comparison. The bike in your example uses a smaller frame and an axle-supported banana seat. On the beach cruiser sized frame there are much longer runs of tubing for flex to affect.

im thinking its a bad idea, but thoughts from people in the know would be appreciated.
Tell your friend he's an idiot. If he insists on doing it register at the flower shop so all you have to do is call for the "Get Well" or "Sorry for your loss" flower arrangement

Put pivot points at the top tubes, then remove the seat tube and replace it with a shock...
What is that guy smoking?

Put pivot points at the top tubes, then remove the seat tube and replace it with a shock...
What is that guy smoking?
Dunno, but I bet a guy could get rich selling it.

GAARRR! My eyes...
Ignoring the ride quality, why do people even buy bikes that look like that? They're so darn ugly. What's with the curved tubes and loopy white thingies?

I guess I'm a stickler for form-follows-function. I like a pretty bike, but I like to see that every physical feature is there for a purpose too.

Do it anyway, it will be funny when it breaks. Then post pictures.

And you people think I'M crazy? :D

And you people think I'M crazy? :D
Hehehe :) I'm gonna downgrade you to eccentric. This guy is trying to remove major structural elements of his bike. Freakin' nuts.

Give it a try. Kestrel has been doing it for years and their bikes are hot sellers:http://www.kestrel-usa.com/bikes/airfoil.php

:roflmao: :roflmao: :roflmao:

If he's got balls for coming up with the plan, he probably won't have them after trying it.

Give it a try. Kestrel has been doing it for years and their bikes are hot sellers:http://www.kestrel-usa.com/bikes/airfoil.php

:roflmao: :roflmao: :roflmao:
Well... Cannondale builds a fork with only one blade. Softail makes a bike with neither seat tube nor seat stays. The catch is that they specifically overbuild the other affected components so that they can handle the strain.

I'm not sure that Walmart has designed their bikes for de-seattubification. :D

The lefty fork is almost exactly like what aircraft have been using for decades, so that has the least of the worries in my book. The real designs have a set target and they engineered all elements to reach it with a margin. The walmart bikes are made to be just strong enough to not break under normal loads. Name of thier game is low cost. There are few mods I would consider to a walmart, most of the time are bracing, not deleting...

And you people think I'M crazy? :D
Yes, and I still do to a point. Here's why: Just as there are varied degrees of mental illness this numbskull is a much more severe case than you are. You do things that are (in my opinion) obsessive, redundant, and impractical. This guy does things that are borderline suicidal and / or will injure him with a great deal of certainty.
CdCf I will say this much at least you have a somewhat understandable reason for some of your ideas. You don't just do things because you think they "look cool"

The lefty fork is almost exactly like what aircraft have been using for decades, so that has the least of the worries in my book.
I trust Aircraft engineers a lot further than I do the folk at "Crack-n-Fail" but that's me

I trust Aircraft engineers a lot further than I do the folk at "Crack-n-Fail" but that's me
Lol.

He should start making mods on his new wheelchair too!





my friend has a cheapo wallmart bike thing that he wants to mess around with. he's thinking about removing the seat tube and just having the thinner white tubes support the weight. he's also thinking about modifying the fender to support the rear of the bike. but all in all, is this a bad idea for him to be removing that seat tube?? im thinking its a bad idea, but thoughts from people in the know would be appreciated.

He should start making mods on his new wheelchair too!
Naww I vote for airbrush work on the casket.

The lefty fork is almost exactly like what aircraft have been using for decades, so that has the least of the worries in my book. The real designs have a set target and they engineered all elements to reach it with a margin. The walmart bikes are made to be just strong enough to not break under normal loads. Name of thier game is low cost. There are few mods I would consider to a walmart, most of the time are bracing, not deleting...

Mountain bikes at walmart have a label that says, "not for mountain biking."

Mountain bikes at walmart have a label that says, "not for mountain biking."
To get picky about it says "not for use off road", but yeah they market "rugged" bikes that are about as rugged as an H2 (perhaps that's giving the H2 too much credit)

Do any of you think that if Walmart tried to make a very simple diamond frame single/three speed adult bike, it would sell well? I think they might actually be able to make a decently reliable bike with that setup.

Do any of you think that if Walmart tried to make a very simple diamond frame single/three speed adult bike, it would sell well? I think they might actually be able to make a decently reliable bike with that setup.
You mean like Sears & Roebuck used to sell? Sadly it wouldn't sell, due to the fact that it's all about marketing now. If it doesn't have imitation bells and whistles itwon't sell

[color=blue]I trust Aircraft engineers a lot further than I do the folk at "Crack-n-Fail" but that's me

Raiyn-

So just for fun I did a search and find that you love to bash Cannondale yet have never once given any details as to why you think they suck so much. You have blamed them for everything from frames denting in a crash to poorly adjusted shifters. Name me one other bike company that offers a lifetime warranty on an aluminum frame with no rider weight limits for the intended use of the bike. If you have trouble parsing that sentence it means that if a 300 pound guy cracks a frame hucking a 20 foot drop off on one of their freeride bikes, he gets a new frame. Sure they are a little more expensive than a comparably equipped bike but that's the price you pay for a frame hand welded in the US, with that solid of a warranty.

So out with it, what experience do you have with Cannondale that makes you so opposed to them.

-s

Raiyn-

Name me one other bike company that offers a lifetime warranty on an aluminum frame with no rider weight limits for the intended use of the bike. If you have trouble parsing that sentence it means that if a 300 pound guy cracks a frame hucking a 20 foot drop off on one of their freeride bikes, he gets a new frame. That's funny since I found this on the Cannondale site

Product Limitations
Problems of pilot error aside, hard-core riding also beats the heck out of your equipment. Although we build and test our bikes to make them tough, there's no way that we can guarantee they'll survive your umpteenth six-foot drop. For starters, there is no industry "jumping" standard. The many circumstances of takeoff, landing, speed, rider technique, etc. are unique. The judgement, lack of judgement or insanity of a rider that may ride a Cannondale bicycle cannot be completely predicted, so it's flat-out impossible to predict how anyone's equipment is going to hold up.

Let's get another thing straight. Buying a Freeride bike does not make you any better. Do not confuse the built-in capabilities of equipment with your own capabilities, which must be learned.

Keeping your bike and all its components in good working order is critical, and it's up to you to maintain and inspect it. Even so, your sweet rig isn't going to last forever. Nothing does, particularly bikes and parts that are built to minimize weight and then subjected to abuse. Our frames carry a lifetime warranty, but that's to cover issues with workmanship and/or materials. See the Cannondale Warranties section of the Owner's Manual. It doesn't mean that they're going to last forever. They're not. It certainly doesn't mean that the bicycle will last forever or can in any way protect you from injury.
http://www.cannondale.com/bikes/tech/safety.html and this

TERMS OF WARRANTY:

* This warranty is not meant to suggest or imply that the bicycle cannot be broken or will last forever. It does mean that the bicycle is covered subject to the terms of the warranty.
* This warranty only applies to the original owner of a Cannondale bicycle and is not transferable to subsequent owners.
* For any warranty claim to be considered, the bicycle must be brought in to an Authorized Cannondale Bicycle Retailer in assembled condition and accompanied by the original, dated sales receipt for the bicycle. (Be sure to keep your receipt in a safe place.)
* This warranty only applies to bicycles purchased in fully assembled and adjusted condition from Authorized Cannondale Retailers or other outlets specifically authorized by Cannondale to distribute Cannondale bicycles.
* This warranty is void if the bicycle is subjected to abuse, neglect, improper repair, alterations, modifications, an accident or other abnormal, excessive, or improper conditions.
* Damage resulting from normal wear and tear, including the results of fatigue, is not covered. Fatigue damage is a symptom of the frame being worn out through use. It is one kind of wear and tear. See sections 5, A and D.
* Damage resulting from improper assembly or maintenance, or from installation of parts and accessories not compatible with the Cannondale bicycle is not covered.
* All labor charges for warranty service are the responsibility of the bicycle's owner.
* During the acceptable duration of this warranty, Cannondale will either repair any defective frame, or, at our option, replace any defective frame with the same or most nearly comparable model then available. THIS IS THE EXCLUSIVE REMEDY UNDER THIS WARRANTY. ANY AND ALL OTHER REMEDIES THAT MAY OTHERWISE BE APPLICABLE ARE EXCLUDED, INCLUDING, BUT NOT LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES.

THIS IS THE ONLY WARRANTY MADE BY CANNONDALE ON ITS FRAMES AND COMPONENTS. ANY WARRANTIES THAT MAY OTHER-WISE BE IMPLIED BY LAW INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE LIMITED TO THE APPLICABLE DURATION OF THIS LIMITED WARRANTY.

Please refer to the documents included with your bicycle for possible further restrictions.

This Limited Warranty gives the consumer specific legal rights. The consumer may also have other legal rights which vary from state to state. Some states do not allow the exclusion or limitation of incidental or consequential damages or limitations on how long implied warranties last, so the above limitations or exclusions may not apply to you.
http://www.cannondale.com/policies/bike_warr_policy.html


Sure they are a little more expensive than a comparably equipped bike but that's the price you pay for a frame hand welded in the US, with that solid of a warranty.
Considering that everything else on it is imported I could care less who welds it. Specialized has just as good a warranty on their bikes and you get more for the money besides a name.


So out with it, what experience do you have with Cannondale that makes you so opposed to them.

-sMy reasons have been posted many times do a search.

I bet riding that thing on anything off road would be life threatening. How was he planning to remove the seat post in the first place?

I bet riding that thing on anything off road would be life threatening. How was he planning to remove the seat post in the first place?
Probably something intelligent like a Sawzall

I hear saws are the tool of choice for bike mechanics these days. :rolleyes:

That's funny since I found this on the Cannondale site
and this

Damage resulting from normal wear and tear, including the results of fatigue, is not covered. Fatigue damage is a symptom of the frame being worn out through use. It is one kind of wear and tear. See sections 5, A and D.



OK, you have me there. I wasn't aware that Cannondale excluded fatigue damage in their warranty. I still think that people too readily criticize Cannondale because they are willing to go out on limb and innovate whereas other manufacturers just keep making the same bikes over and over again or copy the few builders who try something new. Sure sometimes they screw up (like trying to make their own motorcycle engine for example) but if somebody wasn't pushing the limits we'd all be riding hi-tensile steel rigid bikes.

-s

OK, you have me there. I wasn't aware that Cannondale excluded fatigue damage in their warranty. I still think that people too readily criticize Cannondale because they are willing to go out on limb and innovate whereas other manufacturers just keep making the same bikes over and over again or copy the few builders who try something new. Sure sometimes they screw up (like trying to make their own motorcycle engine for example) but if somebody wasn't pushing the limits we'd all be riding hi-tensile steel rigid bikes.

-s


If you don't live close to a Cannondale dealer, your looking at alot of travel time. Cannondale is going to unique themselves right out of business. Any bike mechanic can work on any bike, except a cannondale.
And don't call cannondale for info, all they will tell you, is that you need OUR special tool. Special tool my a$$, A rubber mallet and a screw driver worked just as good. Cannondales are pretty, but you can keep them. And IMO Specialized is innovating all the time. The Epic is one helluva xc bike. And they've licensed out their horsht pivot to numerous bike companies.

If you don't live close to a Cannondale dealer, your looking at alot of travel time. Cannondale is going to unique themselves right out of business. Any bike mechanic can work on any bike, except a cannondale.
And don't call cannondale for info, all they will tell you, is that you need OUR special tool. Special tool my a$$, A rubber mallet and a screw driver worked just as good. Cannondales are pretty, but you can keep them. And IMO Specialized is innovating all the time. The Epic is one helluva xc bike. And they've licensed out their horsht pivot to numerous bike companies.
What non-standard parts do Cannondales have other than irregular headset sizes and some weird forks? And maybe the Hollowgram cranksets, but I would assume the new Dura-Ace or Record cranksets are equally "unique".

I don't own any but thought about buyhing one...

What non-standard parts do Cannondales have other than irregular headset sizes and some weird forks? And maybe the Hollowgram cranksets, but I would assume the new Dura-Ace or Record cranksets are equally "unique".

I don't own any but thought about buyhing one...

Their Headshock and Lefty are enough to keep me from buying one. To each his own though.

Their Headshock and Lefty are enough to keep me from buying one. To each his own though.
I think Lefty is hideous, and I doubt the claim that it's equally reliable and functional to conventional suspension forks. I dunno about Headshock, it doesn't look as bad to me, but I wonder how well it can resist torsional stresses.

I think Lefty is hideous, and I doubt the claim that it's equally reliable and functional to conventional suspension forks. I dunno about Headshock, it doesn't look as bad to me, but I wonder how well it can resist torsional stresses.
Another thing I'm not too keen on is the fact that if you want to use someone else's fork you have to purchase adapters to do so.

And as far as I´m concerned, adaptors always compromise strength :p At least adaptors in electronics compromise performance so I think bikes probably have similarities :p

Man, I haven´t been to this forum in ages. I forgot just how much everyone likes to thread crap :p

They had a guy like him, on TV last night. The guy had a 6" nail in his head for a while.

Maybe he will get on TV ?

If you don't live close to a Cannondale dealer, your looking at alot of travel time. Cannondale is going to unique themselves right out of business. Any bike mechanic can work on any bike, except a cannondale.
And don't call cannondale for info, all they will tell you, is that you need OUR special tool. Special tool my a$$, A rubber mallet and a screw driver worked just as good. Cannondales are pretty, but you can keep them. And IMO Specialized is innovating all the time. The Epic is one helluva xc bike. And they've licensed out their horsht pivot to numerous bike companies.

I like your style. Keep punching those keys!