Frame strength?? beware of curbs.

[Sgottt]

Last year I bought a redline conquest. I wanted something faster than a mountain bike but sturdy enough to handle a hard packed dirt trail or two.
A few weeks ago I was riding around at a snails pace with my 11 year old son in a school parking lot (I know not exactly the intended use but ...) . He decided we should make a sudden change of direction. I turned, but not sharp enough and hit a 4 inch curb straight on at maybe 3-5 mph. I tumbled off without a scratch, got up and took a look at the bike and saw nothing. But after a few more gentle rides I noticed that the frame is buckling on the underside near the front. I'm devastated. I've never spent over $400 on a bike, so this bike was big money for me and I adored it.

I noticed in the warranty papers that it says that if the frame is bent, the warranty is void. My question is, should it have gotten bent this easily? Is it to be expected that it would crumple in a low speed collision with a curb? (I weigh about 175 lbs btw.) The wheel is still true, the front fork is unaffected. Shouldn't a bike be designed such that some of the less expensive components yield before the most expensive one? Could it be that the frame was defective and my bumping the curb just brought the defect to light? Has anyone else out there had a low collision with a curb that buckled their frame?

[wildjim]

Last year I bought a redline conquest. I wanted something faster than a mountain bike but sturdy enough to handle a hard packed dirt trail or two.
A few weeks ago I was riding around at a snails pace with my 11 year old son in a school parking lot (I know not exactly the intended use but ...) . He decided we should make a sudden change of direction. I turned, but not sharp enough and hit a 4 inch curb straight on at maybe 3-5 mph. I tumbled off without a scratch, got up and took a look at the bike and saw nothing. But after a few more gentle rides I noticed that the frame is buckling on the underside near the front. I'm devastated. I've never spent over $400 on a bike, so this bike was big money for me and I adored it.

I noticed in the warranty papers that it says that if the frame is bent, the warranty is void. My question is, should it have gotten bent this easily? Is it to be expected that it would crumple in a low speed collision with a curb? (I weigh about 175 lbs btw.) The wheel is still true, the front fork is unaffected. Shouldn't a bike be designed such that some of the less expensive components yield before the most expensive one? Could it be that the frame was defective and my bumping the curb just brought the defect to light? Has anyone else out there had a low collision with a curb that buckled their frame?

It would seem that a frontal impact with a curb hard enough to damage the frame would also damage the front wheel?

I would ask the questions of Redline and ask for some help. . .

[stric]

It's possible that the frame had a flaw already. I've crashed my cyclocross, mountan and road frames many times at various speeds 9often high speeds). It was usually the wheels that would get damaged first by absorbing the impact. however, I ride on steel frames and steel is stronger than other materials but heavier too. Redline, if my memory seves me well makes Aluminum frames. The latest aluminum frames are not as rigid as their predecessors of the early 90s, so they offer some flexibility and I'd say they should not crack so easily. Check with Redline or a local bike shop where you bought the bike. The problem is that in most cases they'll try to avoid frame replacement because the warranty conditions on bikes come with many strings attached.

[seely]

My boss raced a few seasons on a Redline Conquest w/o issues. I have to ask what good is a warranty if it basically doesn't cover the frame? Give Redline a call.

[darkmother]

Go to the shop where you bought the bike and talk to them. They should be able to help you negotiate with the manufacturer. I would suggest that the scenario you are describing constitutes normal use, and that the frame failure is a result of a design flaw or manufacturing defect. If your bike store is sympathetic and willing to help you, I suspect you can get the frame replaced.

[MichaelW]

I had a freak low speed frontal impact similar to that (but I hit the rear end of a car at 3mph). On my bike the forks were weaker than the frame so they bent backwards and saved the frame from damage. I just had to replace the forks.

[wildjim]

I had a freak low speed frontal impact similar to that (but I hit the rear end of a car at 3mph). On my bike the forks were weaker than the frame so they bent backwards and saved the frame from damage. I just had to replace the forks.

I am curious, was the wheel damaged also?

[chris hansen]

I had an old mountain bike that I loaned to a friend who ran it into a stop sign pole. The frame bent but the wheel and fork were fine.

[MichaelW]

I am curious, was the wheel damaged also?
No, the wheel was fine but it transferred enough force to bend the forks up at the fork crown. If you consider how much force wheels absorb in a bunny hop, they are plenty strong enough.

[cxc]

I don't know the exact details of the collision. The Conquest is a thin walled Al frame and a frontal impact with 175# behind it at 5 MPH could definitely cause a buckling of the dt if the conditions are right (or wrong as it might be seen). I don't know which Conquest this frame is, but sometimes the fork takes the brunt of it, the wheel is often not damaged if it is hit head on with good tire pressure to spare the rim from denting. It doesn't hurt to contact Redline to see what if anyting can be done-perhaps they have a crash replacement policy. A few of the earlier posters to this thread have mentioned that is is poor design, mfg. defect, or redline's problem. This type of impact doesn't really constitute "normal" useage for this type of bike. Admittedly, I often use my CX bike as a mtb, but am well aware that a poor landing or a missed hop will crack my fork or dent my tube or my rim...I will not blame this on "defective" workmanship or bad design. For this reason, I've 'sacraficed' during a race and dismounted on a high curb jump that other riders were jumping b/c I didn't want to risk breaking my bike for a race I couldn't win. Accidents happen.

[wildjim]

No, the wheel was fine but it transferred enough force to bend the forks up at the fork crown. If you consider how much force wheels absorb in a bunny hop, they are plenty strong enough.

Then I have(had) a misconception of what may happen during a crash. As I assumed that the wheel(rim) would be the first to go from a direct frontal impact. But considering that the wheels are supportive and resilient during the entire ride over all types of terrain, it makes perfect sense.

[MichaelW]

Then I have(had) a misconception of what may happen during a crash. As I assumed that the wheel(rim) would be the first to go from a direct frontal impact. But considering that the wheels are supportive and resilient during the entire ride over all types of terrain, it makes perfect sense.

Yes, in normal riding when you hit a big bump, the wheel absorbs a lot of impact and also transfers a lot of force up along the axis of the steerer tube. This pivots the whole bike about the rear axle. No individual tube is subject to bending.
In a frontal impact the force is applied as a bending force on the steerer tube/crown using the fork arms as levers.
With a bent fork, you can make a roadside repair using a drain cover. Put the fork arms into a slot and bend them back again.

[Brian]

I ride on steel frames and steel is stronger than other materials but heavier too. Redline, if my memory seves me well makes Aluminum frames. The latest aluminum frames are not as rigid as their predecessors of the early 90s, so they offer some flexibility and I'd say they should not crack so easily.

You're getting issues confused here. The diameter of the tubing, along with the wall thickness and metal composition determines the stregth more than just the material class (ferrous vs non-ferrous). Modern aluminum frames are known for their rigidity, they don't flex. His frame did not crack, it buckled. A crack generally happens at a junction. I'm willing to be that his frame buckled either right at the junction (straight gauge tubing) or a few inches from a junction if it was butted tubing.

Barring a 2nd gunman on the grassy knoll, here's my theory: The rim wasn't damaged as the impact was transferred by the rigid(?) fork up to the frame, like a big lever. You've got the rider weight multiplied by the force of whatever speed he was going (I'm no good at physics) and this energy had to go somewhere. Sucks that the frame is damaged, but I don't see this as normal usage. Now, if you've got a good relationship with your LBS, they may be able to do something for you.

[darkmother]

If running into a curb at 5mph is not catagorized as normal usage, then I suggest the criterion for the frame design is flawed. Why cyclists are willing to accept poor engineering practice is beyond me. You would not, for example, accept a car whose frame buckled just because you hit a pothole. The buckled downtube at the end of the butted section in the tube is the most common failure I see in bicycle frames. While no frame can withstand all possible impacts, a simple reinforcement of this area would go a long way to reducing failures.

[DogBoy]

The rim wasn't damaged as the impact was transferred by the rigid(?) fork up to the frame, like a big lever. You've got the rider weight multiplied by the force of whatever speed he was going (I'm no good at physics) and this energy had to go somewhere. Sucks that the frame is damaged, but I don't see this as normal usage. Now, if you've got a good relationship with your LBS, they may be able to do something for you.

A picture of what you just said...(BTW, its Mass * Accelleration = Force, not speed).

[Sgottt]

A picture of what you just said...(BTW, its Mass * Accelleration = Force, not speed).


Yes the frame buckled about 4 inches back from the headpost on that lower tube. It also looks like the top, horizontal post is 'swelled' about 1 inch back from the headpost (maybe as a secondary collapse as the bottom post bent).
I'm not sure what the proper mass to apply in your force calculation is though. In a selfless act to try to save my bike from any harm, I kind of let myself fly forward over the front handlebars and tumble onto the grass on impact. Whether that reduces the compressive force on the frame I don't know. But really I was only moving at about 4 mph. I got up without a scratch or bump or bruise.

So if the bike decellerate 4 mph with a 175 lbs load and the frame bent would you expect the same thing to happen if I were going say 17 mph and hit a pot hole that slowed me down to 13 mph?

I know once about 10 years ago I lost a front wheel on a bike (dont ask) at about 15 mph and drove the front fork straight into the pavement. That was a steel bike. The front fork bent wide, the frame was unaffected. I bent the front fork back got the wheel back on and continued riding.

I understand that part of what you are paying for in these 'more expensive' bikes is the light weight but I thought in buying a cyclocross bike rather than a road bike I was also buying some sturidiness. I'm quite sure that no other bike I've ever ridden would have been damaged like that in that collision.

This weekend will be my soonest opportunity to visit the local bike shop where I bought it. What type of gifts do bike store managers like?

[darkmother]

Good luck with the shop. Just be careful how you word things, but don't BS the guy. Explain to him that you think it is kind of dangerous for a manufacturer to sell such a fragile frame. If they are willing to help you out, I think your chances are pretty good.

BTW, I had my 12 year old frame repaired under warrantee with no receipt because the local shop helped me out. I didn't even buy it there, but the employee thought he remembered selling it to me.

[Brian]

If running into a curb at 5mph is not catagorized as normal usage, then I suggest the criterion for the frame design is flawed. Why cyclists are willing to accept poor engineering practice is beyond me. You would not, for example, accept a car whose frame buckled just because you hit a pothole. The buckled downtube at the end of the butted section in the tube is the most common failure I see in bicycle frames. While no frame can withstand all possible impacts, a simple reinforcement of this area would go a long way to reducing failures.

Do you run into curbs as part of your normal riding routine?

[darkmother]

Do you run into curbs as part of your normal riding routine?

Not curbs. But I run into stuff that size all the time. And no, my bikes don't buckle at the downtube. I would be seriously pissed if they did.

[ZenNMotion]

This is a reason why I'm not a big fan of Aluminum bikes (and I own a couple, including an Empella Bonfire cross, which as nice as it rides, I'll probably sell soon). This is a common area for frames to fail, sounds like you have a less than perfect weld there, coupled with metal fatigue that is Aluminum's weakness as a frame material. This shouldnt happen with a year old bike that isnt raced. I hope Redline does the right thing-

[TLN]

Definitely sounds like a flawed frame. Redline is very cool about this sort of stuff. I bought a USED very OLDER Conquest Pro that was used hard. After about a year I was going to paint it, so I stripped it down. Then I noticed a hairline fracture that was starting to wrap around the chainstay cause by chainsuck. I went to my LBS and they threw a call into Redline and told me either they would replace it for free or worst case, I would have to pay for a new frame. Well due to the frames age I wasnt expecting anything. So we sent in the frame and 1 week later I got a call saying that since it was an old frame and the damage was not caused by any manufacturing defect they wouldnt replace the frame for free.......they would only charge me $200 for a new frame/fork and they would rebuild it with my components. Not too shabby if you ask me!

So Im almost sure they will do even better for you.

[LV2TNDM]

It would seem that a frontal impact with a curb hard enough to damage the frame would also damage the front wheel?. . .

This is not true at all. Intuition may cause you to think this, but it is not the case. Wheels are incredibly strong; they posess a strength to weight ratio of 400 to 1, which is among the highest for any man-made structure. I could ram all my bikes into a parked car and destroy every frame and fork and have perfectly good front wheels.

Bike shops and manufacturers get this situation somewhat regularly. It's called JRA. "I was Just Riding Along, when...." Be sure not to take this approach. It won't work. The previous posts describe how your frame failed: the force was transmitted through your front wheel to your fork, which acted like a lever arm on the head tube. This type of failure is not that uncommon. If bicycle manufacturers designed bikes to withstand high force frontal impacts (and they easily could), they wouldn't sell very many. In other words, the bikes would be so heavy you wouldn't want to ride them.
So, manufacturers try to find a middle ground. The bike should be able to take a certain amount of frontal force, while maintaining low frame and overall bike weight. Some manufacturers purposely design their frames and forks so that the fork will fail first in the "frontal impact" situation. But guess what? Customers complain that their forks failed! You've saved them from a frame failure, but the consumer only sees a failed fork and are thus unhappy. It's somewhat of a no win situation.
In your case, if you really were going 3-5 miles per hour under the circumstances you describe, then perhaps you have a case. However, you mentioned that the top tube was deformed as well. It takes a great amount of force to both buckle the downtube and bend the top tube as well. If the downtube failed and the top tube were not bent, buckled or deformed in any way, then perhaps there was a problem with the downtube. But this isn't the case so this leads me to believe there was more force involved than what you described.
Either way, approach your LBS with a solution-oriented approach. Leave the accusations and defensiveness at home. Most manufacturers offer a low-cost frame replacement option for cases like this. And there's always the off chance that there may have been some manufacturing defect that's only now coming to light on your model.
Good luck!

[darkmother]

If bicycle manufacturers designed bikes to withstand high force frontal impacts (and they easily could), they wouldn't sell very many. In other words, the bikes would be so heavy you wouldn't want to ride them.


Nonsense. Adding a 2 oz gussett, or increasing the wall thickness of the downtube does not render a frame unridable, at least in my book. There are plenty of sub 4 lb frames that I would feel more than comfortable running into a curb on.

[Brian]

Nonsense. Adding a 2 oz gussett, or increasing the wall thickness of the downtube does not render a frame unridable, at least in my book. There are plenty of sub 4 lb frames that I would feel more than comfortable running into a curb on.

With what size tires? And front suspension, or rigid?

[darkmother]

With what size tires? And front suspension, or rigid?

Ok, say my cross bike. 35 c tires, rigid fork. I weigh 195lb. In fact, I just got doored on that frame, and it survived without damage. The front wheel was about 1/8" out.

[Brian]

Getting doored is not the same as running into a kerb. Not be a long shot. See drawing above regarding leverage. Go run your bike into an actual kerb, and post photos of the damage please.

[LV2TNDM]

Nonsense. Adding a 2 oz gussett, or increasing the wall thickness of the downtube does not render a frame unridable, at least in my book. There are plenty of sub 4 lb frames that I would feel more than comfortable running into a curb on.

Nonsense? Do you realize what forces are generated in such situations? A 2oz. gussett won't protect the entire downtube. A gussett simply increases the strength and fatigue resistance at the most vulnerable point on the frame - the downtube/headtube junction. A gussett would simply transfer the forces to the next vulnerable spot on the tube. And this says nothing for the top tube.
My point is that there are so many possible ways to destroy and damage a frame. Frontal impacts are probably the most damaging crashes a bicycle will encounter when no other vehicles are involved. Just preventing a nice frame from being dented would require significant increases in tube wall thicknesses, which would add considerable weight. And add that to all the "gussetting" you'd need to do to make a frame survive would make the thing pretty darn heavy.
And we haven't even addressed the fork failure issue. So if you add all the possible scenarios a bike could face and the contigencies manufacturers would have to take, frames would get very heavy.
I'd rather take what we have now. I've been riding seriously since '79 and have never buckled the head and downtubes on any frame I've ridden*. However, I also understand that a moment's inattention could result in some serious frame-destroying consequences. But I understand and accept the risks.
*I've broken several frames - fatigue failures all. And I don't want to think about all the components I've broken. But the broken BB spindle in Moab was probably most memorable.

[LV2TNDM]

Getting doored is not the same as running into a kerb. Not be a long shot. See drawing above regarding leverage. Go run your bike into an actual kerb, and post photos of the damage please.

No kidding! We got doored on our tandem in San Francisco with our baby in a child seat. Yikes! It's the only time I've been doored and hopefully the last. Passenger in a limo opened the right back door into my path, so I didn't expect or see it coming with the tinted windows. Taco'd front wheel. But absolutely no frame damage. Stood on the wheel to get it back to somewhat resembling round and hobbled to the train station to get home. Run a tandem into a curb and you're gonna be real sorry! Since it's a Cannondale with three tubes converging at the head tube, I'd be curious to see which would fail first: fork or frame. I'd put my money on the fork!
I had a bike shop customer get doored by a motorist back in '88. It is a great story! He was this big tall guy (and my Chemistry tutor). He wasn't injured badly, but his bike needed a little attention - nothing major. A few days after the accident, the car's insurance company called him asking him for insurance information. After he said he didn't have insurance, the agent became purturbed. He responded by saying, "I was on my bike, you idiot!" The insurance agent had assumed he was in a car because he folded the offending door completely back on itself! The driver got exactly what he deserved! And the insurance company was lucky he didn't go after them for "pain and suffering" in addition to all the damage the driver caused. Now, that's a door story I wish I could claim as my own!

[Adelaarvaren]

I'd definitely talk to Redline... I've got a 1997 cross frame from them (before they had names, it just says "cyclocross USA" and it was actually built in the USA) which is bulletproof. I ride singletrack on it all the time, do my commuting on it, raced it several seasons, etc. LOVE that bike!

[darkmother]

Getting doored is not the same as running into a kerb. Not be a long shot. See drawing above regarding leverage. Go run your bike into an actual kerb, and post photos of the damage please.


Explain to me how getting doored is significantly different. There is still an applied force parrallel to the direction of travel, only this time it is up at axle level. The fork is still acting as a lever, and is still applying a moment to the head tube. This type of scenario can and does result in buckled downtube failure as described by the OP. BTW I was doing 25km/hr before imact, and came to a complete stop in less than the distance swept by the middle of the door as it opens to it's stop. That is a *lot* of force.

You make it sound as though hitting a curb at 5 km/hr is a catastophic, frame killing event. I suggest otherwise. A frame that fails under such circumstances is not well designed, or has a manufacturing defect.

[TLN]

Explain to me how getting doored is significantly different. There is still an applied force parrallel to the direction of travel, only this time it is up at axle level. The fork is still acting as a lever, and is still applying a moment to the head tube. This type of scenario can and does result in buckled downtube failure as described by the OP. BTW I was doing 25km/hr before imact, and came to a complete stop in less than the distance swept by the middle of the door as it opens to it's stop. That is a *lot* of force.

You make it sound as though hitting a curb at 5 km/hr is a catastophic, frame killing event. I suggest otherwise. A frame that fails under such circumstances is not well designed, or has a manufacturing defect.

Different as the applied force is in a different location thus creating a different force/angle in the direction of the momentum....all statics and strengths my friend. But you are correct in that it most likely is a flaw in the frame. The forks should give out before the frame... in the ideal situation. Just look at the abuse the pro riders give their frames... they are cranking the hell out of them and sometimes on cobblestone at high speeds. Frames can and do withstand a lot more than hitting a curb at 5km/hr. Ive slammed into things a lot harder/faster than that with only damage to things other than the frame. I have hit a 1-1/2 to 2 foot dia. log sticking out of a bush going down hill and going into a turn doing about 20mph. Forks shot, wheel shot, handlebars shot, ass and elbow shot. Frame needed slight adjustment, definitely nothing major.

[slagjumper]

Hey I once hit a parked car doing about 3 miles an hour and it bent my Raliegh DT and fork. I rode that bike for years w/o issue-- except that it now had the geometry of a track bike and my toes would hit the front wheel on turns.

I seem to recall manufacturers replacing "cracked" but not bent frames. I think it is a bit odd that the aluminum bent rather that cracked because it is harder than steel. A helpful bikeshop employee could go a long way in getting satisfaction.

[Brian]

Explain to me how getting doored is significantly different. There is still an applied force parrallel to the direction of travel, only this time it is up at axle level. The fork is still acting as a lever, and is still applying a moment to the head tube. This type of scenario can and does result in buckled downtube failure as described by the OP. BTW I was doing 25km/hr before imact, and came to a complete stop in less than the distance swept by the middle of the door as it opens to it's stop. That is a *lot* of force.

You make it sound as though hitting a curb at 5 km/hr is a catastophic, frame killing event. I suggest otherwise. A frame that fails under such circumstances is not well designed, or has a manufacturing defect.

A door can absorb some of the impact. Kerbs aren't known for being very forgiving. Someone else has already pointed out the leverage issue as well, which is not "parrallel to the direction of travel". Once again, go run your bike into the kerb and take some pictures for us. Oh, and email the manufacturer and let them know you broke your frame running it into the kerb.

You've got unrealistic expectations regarding frame design and durability. You're wrong, get over it, and move on.

[darkmother]

A door can absorb some of the impact. Kerbs aren't known for being very forgiving. Someone else has already pointed out the leverage issue as well, which is not "parrallel to the direction of travel". Once again, go run your bike into the kerb and take some pictures for us. Oh, and email the manufacturer and let them know you broke your frame running it into the kerb.

You've got unrealistic expectations regarding frame design and durability. You're wrong, get over it, and move on.

This will be my last post regarding this issue. There really isn't much to talk about. In summary, I *have* run my bikes into curbs at the speeds being discussed, and there is no damage to photograph. I don't think you understand the forces involved as much as you pretend to. If you enjoy riding stupid light frames with paper thin walls that buckle at the slightest bending moment, so be it. I like my frames to last, so I buy, or in the case of my cross frame *design* appropriately.

[Brian]

I mostly ride a custom titanium tandem, not "Stupid light frames". I do have a couple of XC frames as well, but my Cannondale and Kinesis (Custom tube set again) have never been run into a kerb. Go ask at your LBS which bike is best for running into kerbs, if that's how you get your kicks. I prefer to avoid obstacles.

[prodigal son]

I ran into a locked steel gate at a park. I was on steel cx bike. I was not going super fast, under 10 mph. I went over the bars and scratched the headtube, but htat was about it.
Sorry to revive an old thread.

[G-Unit]

I never really liked Redline, I read a few of the reviews on them in Bicycling Magazine and they seem like a bargain bike company.

Sorry for the misfortune with your bike though, it really sucks to put your heart (and $$$) into a bike and have it fail on you.

Save up and get a Poprad!