cfm

Hello All,

I'm new to this message forum and just recently got back into biking at age 48. I used to ride a 10-speed up until about 1990. About 3 months ago I purchased a GT Aggressor mountain bike (model 6061) because a friend of mine has one and I rode it and loved it. I've been back into riding everyday for about 3 months now w/o any problems other than a flat tire. Then last Wednesday night I was flying through (Hauling Butt) a subdivision having a blast until I decided to begin braking for an upcoming intersection. All I remember is beginning to brake and then trying to pick my face and chest up off the pavement. My husband witnessed the whole event and said that the rear tire went straight up and over me slamming my chin straight down into the pavement at about 20mph. It was instantaneous! He said my feet were still in the pedals when he took the bike off of me. All my injuries are symetrical so what he says happened makes sense. I was knocked out for a few seconds and I'm pretty seriously injured, but why did this happen I ask? I NEED to know...

I have been using my front and rear brakes simultaneously since I began riding again, thinking that I would experience smoother, more even stopping. I did NOT KNOW that the front brake was stronger than the rear brake though, until I read the archived thread #73271 ("Is there a difference between front and rear discs/") yesterday. I was pretty much applying the same amount of pressure on each brake. Would that be enough (with the front brake being stronger) to instantaneously flip my bike like that though? Is it posssible that my front brake is Maladjusted and just locked up for some reason?

Another thing that makes me think that it may have been a problem with the bike, and not a problem with the rider (I hope, Ha Ha), is that this is the first time I've ridden this particular bike in about 2 months. I have 2 GT Aggressor model 6061's, one a 2004 and the other a 2005. I've been riding the 2005 nearly exclusively because I like the updated shifters on it much better than those on the 2004. Tuesday night I had a flat on the 2005 so rode the 2004 bike on Wednesday night, which is when the crash occurred. I've been riding the 2005 bike using both brakes together all this time w/o a problem... Hauling Butt too! I ride the 2004 once in about 2 months and I have a major crash. Was I just lucky on the 2005 bike all this time, and perhaps I've just been braking WRONG all along?

Does anyone have any ideas or questions for me that may help me to understand what happened to cause this crash??? I do realize that I'm a novice at biking after all these years, so feel free to use some constructive criticism if necessary. I really do NEED to know what happened so I don't do this again. I don't think I'd live through another crash like this. I feel very lucky that I didn't break my neck... or maybe I did and don't know it yet. I'm going to try to get my neck and upper back exrayed this pm. My lower jaw was exrayed last Thursday and it's broken inside the joint (both condials snapped off) on both sides. I literally rammed my lower jaw up into my ears. The specialists don't like to do surgery within the joint because it usually results in more aggravation, loss of range of motion, etc. down the road than if they just leave it alone. Sooo, my lower jaw is permanently disconnected from my upper jaw. I have cracked ribs and possibly a cracked sternum. Both of my elbows are fractured, but tolerable. PLEASE help me figure this (instantaneous flip) out so I don't do this again...

Thank You,
Carol in S.Tx.

Little Darwin

Carol,

First, good luck on your healing process. Take care of yourself!

You may have already checked, but... Is there anything about the bike that appears unusual after the accident? I.E. What damage is there to the bike?

This may provide information useful in determining a likely cause of your accident.

The bike may have been damaged as a result of the accident. But there is another possibility... something was wrong before the accident and since you seem to have taken the bulk of the force, the evidence may still be detectable. There is a chance that your bike holds the answer to this mystery...

Anything bent like spokes, rims, disc etc?

IF nothing appears wrong, does the brake seem to catch at any point if you rotate the wheel either with no brakes applied, or brakes lightly applied?

Is anything on the bike, or that you were carrying capable of getting caught in the spokes like a loose computer cable or anything?

schang

Sorry to hear about your accident, it sounds scary, and I wish you the best possible recovery.

I don't know whether it was hardware or braking technique, or quite possibly a combination of both. Sheldon Brown (of course) has a very good article on braking that is definitely worth reading, as far as technique goes: https://sheldonbrown.com/brakturn.html

I'm not up on disc brakes, but it might help others on the forum if you could mention whether you have disc brakes in front and rear (it sounds like you do), and if they are hydraulic or mechanical.

cfm

Hi Darwin,

The ONLY damage to the bike is on the top of the handlebars... the shifter numbers are ground/gouged off in about a 1-inch area on each side. The outer knuckle on both of my hands is scraped/gouged too so I guess they were still on the grips when it flipped. I can find no other damage other than a minor scrape on the outside of one of the pedals. If the shifters still work, then the bike is still rideable. The tire appears to spin 'true,' and I can't see any bent spokes or disc. The brake appears to grab evenly when I spin the tire, even when applied lightly. I wasn't carrying anything that could have gotten caught in the spokes or between the the tire and the forks. The only thing I noticed that 'might' have gotten caught is the little cheap reflector that came on the tire. It's loose (only attaches to one spoke), but not cracked or broken. It may have come loose from the impact... dunno! The only other thing on the bike was a seatpost attachment that sits well above the rear tire... for carrying things when needed. It was flipped sideways, but I don't think it would have anything to do with the front brake locking up. I guess I should take the bike to a shop and request that an expert look it over real well...

Thanks for the well wishes. It'll take a lot of time to heal I know, but I plan to ride again soon... as soon as I can get the tire fixed on the 2005... and as soon as I get my neck and back exrayed. Those problems didn't present themselves until 3 days after the wreck. I also broke or cracked most of my upper and lower molars. It was not nice spitting my teeth out in the road. I was told that some of them may 'die' from the impact and will have to be pulled. They won't even work on them until they see what they're going to do... just antibiotics to keep abcesses from forming around the damage. What a mess eh! I never, never expected something like this to happen. I may be feeling like I'm still 20, but I'm not crazy enough to risk major injuries. I really 'think' the brake locked up for some unseen reason...

Thanks again,
Carol

DannoXYZ 

Carol, sorry to hear about your wreck, hope you recover smoothly.

"I did NOT KNOW that the front brake was stronger than the rear brake though, until I read the archived thread #73271 ("Is there a difference between front and rear discs/") yesterday. I was pretty much applying the same amount of pressure on each brake. Would that be enough (with the front brake being stronger) to instantaneously flip my bike like that though? Is it posssible that my front brake is Maladjusted and just locked up for some reason?"

How are the brakes now after the wreck? If the pads are still parallel to the rim and aren't ripped off, I think you can be assured the bike is OK. Stand next to the front wheel, lean down and apply the front brakes to see how they line up with the rim. Do the pads touch the rim evenly on the sides, that is, the pads are matching the sides of the rim? They're not too low and risk running off into the spokes?

Advances in technology have improved braking-performance tremendously. You can now apply the brakes with just 1 finger and lock up both tyres. This then requires some finesse in order to extract maximum deceleration rates safely. The exact physics behind braking is explained in this article: Physics of Racing - Weight-transfer.

When you initially apply the brakes, your weight transfers from the seat to the handlebars (your arms feel more weight). This puts more weight over the front tyre (Lf in the article), and removes the exact same amount from the rear tyre (Lr). Tyre-traction is determined by vertical loading on the contact patch, so as your weight transfers to the front, the front-tyre has more traction than the rear. The amount that changes is based upon the braking-force (Bf). The faster you stop, the greater the weight-transfer.

The other reaction that occurs to the weight-transfer is the rotation of the bike verticaly around the front-tyre's contact patch. Depending upon how quickly you decelerate and the higher the COG (center-of-gravity) over the front contact-patch, the bike+rider system will tend to pivot forward. This lifts the rear and pushes down on the front. The front tyres gain grip and the rear loses grip. So you need to adjust the pressure you're squeezing on the levers and your body's position on the bike to account for this change in grip. We can separate the braking action into three distinct steps:

1. initial braking from steady-state speed is done by grabbing both of the brake-levers. Use only about 20-30% force on the levers and apply it gently. Do not just grab the leverls and pull, imagine you're squeezing a water-balloon between the lever and the handlebar and you want to do it gently so you don't pop the balloon.

2. increase braking-force by gently increasing the squeeze on the brake-levers to 50%. You'll feel the weight-transfer to the front as your weight is pushed forward from the deceleration (or you can imagine that the bike is pushing back). To counter thes weight-transfer, push back with your arms to shove your body to the back of the bike. It helps to straighten your arms and slightly lock your elbows.

3. maximum braking force is achieved by increasing the front-brake lever squeeze even more AND at the same time, decreasing the rear-brake lever force. You'll feel the rear tyres start to skid and slide as deceleration increases and transfering more and more weight to the front. So you lighten up the rear brakes to reduce its force on the rear tyre.

At the SAME time, you want to fully straighten your arm and push them foreward and push your body to the rear of the bike. You'll feel like you're sliding off the rear of the seat. This is fine because it actively puts more of the weight over the rear tyre that's getting light. In order to really extract FULL maximum braking force from the front-tyres, you squeeze the front-brakes even harder and you'll notice that the rear of teh bike comes off the ground. You want to scoot entire off the rear of the seat with your arms fully locked aiming forward to keep yoru body from flying over the handlebars. Since the rear is off the ground, the rear brakes do no good, so you lighten up on the rear brake lever. With your rear off the seat, you can lower your butt over the rear tyres and rest your belly on the seat. This lowers your COG and reduces the weight-transfer to the front wheel.

There's debate on which position the legs & feet should be in. Some people like to have one leg fully extended about 45-degree forward to push their body to the back of the bike. This places the pedal with the straight-leg lower than horizontal and the other one slightly above with a bent leg. Personally, I like to have both my legs slightly bent with the crankarms close to horizontal. This allows me to flex my knees and provide some suspension movement so absorb bumps under braking.

So in summary, braking is a dynamic event with the initial 50/50 split in weight-distribution moving shifting to the front tyre. This shift changes with time and braking-force, the faster you brake, the faster the weight shifts. There are modulations you have to do with the levers to account for this weight-shift and body-position adustments that needs to be done as well. So... I'd recommend practicing braking in an empty parking-lot or quiet street somewhere to get used to the feel. Start an easy pace, say 10-15mph and use the brakes just slightly. Then go do it again with slightly more pressure on the levers. Get used to that and repeat again. Get used to modulating the pressure on the levers as braking forces build (increase front, decrease rear). After a while, you won't have to think about this and it becomes natural.

I'll see if I can't find a picture somewhere of a biker under maximum-braking with his *ss hung out over the rear-tyre. I recall Alexi Greywall had an article in a mag. showing this sometime back in the '80s. Maybe I'll just go outside and make a video....

rideabike

Sorry about the accident.

Could the brake have stuck? I know that when I stop, I do so by feel. If the brake is on a little too hard, I back off a little.

Maybe the brake stuck as you applied it, you couldn't back it off, your weight shifted forward and you flipped?

cfm

Thanks Schang,

I read Sheldon Brown's article yesterday and definitely found it very useful. Too bad I didn't find this forum and read up on all the basics BEFORE I had a big mishap. At least I would have had a clue how much stronger the front brake was than the rear brake. Yes, I agree that my wreck may have been caused by a combination of mechanical and 'inexperienced' technique. I just know I didn't jam on the front brake... I was going Very fast though. It just doesn't make sense to me that I instantly flipped, at least not yet.

Yes, I have disc brakes front and back. I believe they are mechanical. I'm not sure what hydralic brakes are on a bike. The 2004 bike that I crashed has Radius brakes and the 2005 bike has Shimano brakes...

Carol

CTBiker1001

Hi Carol,

I am so sorry to hear about your accident. Rest up and heal fast - recovering from injuries can be very frustrating.

I know this is a long shot, but was the road you were on very bumpy or rough? If so, could you have bounced a little bit, making the front tire go into the air? If so, the front brake may have totally stopped the wheel and you may have come down on a stopped tire. Again, this is a long shot, but just thought I would ask.

DannoXYZ 

Ok, found a picture of what the rider's position looks like:

Karldar

And I thought I'd had some serious crashes.... Hope you're recovery is going okay. Your injuries make me think you were on the wrong end of a bull ride or something...ouch!


I've done the same thing on a trail ride before, only I was bunny-hopping an obstacle and panic-braked while in mid-air. I broke some skin and teeth, but that was it. I would definitely check the roadway for ripples, debris, etc. as well. Sounds almost like the laws of physics decided to give a demonstration?

jur

I would suggest strongly that the front brakes be completely disassembled and minutely examined for any irregularities in the disc or pads. I hope the bike has not been ridden since thus obscuring possible clues.

It may simply have been a case where the different bike's brakes grip more harshly, You rode this bike, being unused to it's brakes, braked too sharply. The forward unbalance that this caused made you involuntarily grip the bars tightly, causing catastrophic lockup. I have seen my son go over the bars like that when they rotated in the stem when he braked. The unbalance made him grip it tighter, locking the brakes.

cfm

DannoXYZ,
Thank you for the wonderful, informative reply! I really appreciate it, picture and all! No doubt I was in the 'regular riding position' since the flip happened immediately after my initial braking. I do appreciate the explanation and picture regarding weight distribution though. I'll definitely be putting this info into practice from now on! Even though it's fairly common sensical (word?), it certainly helps to see it in black and white! The brakes appear just fine post wreck, and yes, the pads are relatively centered on the rim. I'll definitely practice the correct braking techniques in the near future to make sure that I get it right. I'm certain now that I was using the brakes incorrectly, but still don't feel that I did anything that would have caused the flip. I'll also take the bike to a Pro Shop, explain what happened, and ask them to carefully inspect it for me (so I won't fear the front brake on it!). Here's a link to an eBay auction selling the exact same bike (mine has a medium frame though) that I wrecked:

https://cgi.ebay.com/2004-GT-Aggresso...QQcmdZViewItem

Thanks again for taking the time to be so helpful!

Sincerely,
Carol

slagjumper

That sounds like a nasty crash. Could there be oil on the front rotor? That might make the brake grab. In general disc brakes are much more sensitive then cable/rim brakes. Sometimes the geometry of the bike and your arm lenth puts you too far forward to brake safely. If you are panic braking or going down a hill, you need to get that butt back behind the seat. That can be a problem if you have short arms/large breasts and too long top tube on your bike. The breasts can force your arms out a bit and "eat up" arm lenght making it harded to get far enough back.

bhchdh 

May you heal well, and soon.

cfm

CTBiker1001,
Wow, based on what happened, and how instantaneous it was, this makes sense to me! Is this what happened though, I dunno! It's definitely possible! The road I was on was rough asphalt with an occasional bump, pit, or rut. It's possible that the front tire was airborn ever so slightly when I began braking. In my mind, this certainly would explain why I just don't 'get' what happened. I guess I'll never know for sure on this one though. If no mechanical problems turn up, then this is likely the explanation that I'll lean towards. Thank you so much for your reply and thoughts!
Sincerely,
Carol

CTBiker1001

CFM, I would think the odds of this being the problem would go up if you are especially light and/or you had relatively high pressure in your tires. But, like you say, it may be difficult to ever really figure it out.

I hope today was better than yesterday for you and I hope tomorrow is even better.

Oh, and by the way - I was stung 8 times by a swarm of bees today (totally non bike realted), so I'm feeling a little of your pain tonight.

Michel Gagnon

Ouch! Prompt recovery, I hope!

Since the bike looks OK, there probably wasn't anything to stick through the wheel. But what about a large pothole or a lengthwise crack in the street? Could your front wheel have fallen into one while you were braking hard?

Apart from the wheels and brakes, check the fork and the downtube (especially near the headtube) to see if anything is bent. It would indicate that the front wheel was blocked by something, and it would also mean that the bike isn't safe anymore.

locky63red

I went for a ride on the weekend and witnessed a huge stack with a woman riding with me going straight over the handlebars and smacking face first inthe dirt. She was also riding a unfamiliar bike(Brand new for her) She had applied the same amount of force on the brakes as what she had been used to on her old bike . Bum side up instantaneously. Lucky for her she grazed her abdomen and a few bruises, helmut worked and so she could ride on. Hope you get well quick.

dstrong 

Sorry if someone already mentioned this...I read quickly through the bulk of the responses and may have missed it.

Did anyone mention the front shock as being a potential problem or contributor? During heavy front braking the shock will compress until it has no further to go. At that point, the braking force seems to increase as the shock is not absorbing any more of the braking load.

I know that I was surprised several times on my MTB on how much it would "dive" in certain braking or bump situations. I always rode my shocks on their most stiff setting.

Good luck on your recovery!

cfm

slagjumper,

I'm very clueless regarding bike mechanics (plan to brush up on that while recovering). Could you please tell me what the front rotor is??? Also, I suspect that I'm confused as to what disc brakes are... the bike I wrecked has 'Radius Alloy Linear Pull Brakes.' If those brakes are the same as 'cable/rim brakes,' then I clearly don't have disc brakes as I indicated in an earlier reply. Obviously, I have A LOT TO LEARN, and I appreciate all the help everyone has contributed so far! I'm certain that I wasn't panic braking because I was having fun, very relaxed, and never saw a problem coming. It was an instantaneous, freak thing. But yes, I definitely need to have my butt back behind the seat when braking from a fast speed. I'm certain that I didn't in this case. I have long arms and small breasts, so I doubt that contributed much to the problem. I am a short girl though (5'3"+) and 140lbs hoping to get back down to about 120... likely will happen soon with my liquid/mush diet from the broken jaw. I'm likely using a bike-frame size too large for my small body (don't know if that's relevant to this particular situation), but like I told them at the bike shop, "We like things BIG in Texas." Actually, this frame size (M) 'feels' perfect to me. I can't imagine riding a smaller one...

Thanks again,
Carol

cfm

Jur,

I plan to take the bike to a shop (The Pedal) in Corpus Christi that has a very good reputation to have the brake assembly minutely examined for irregularities as you suggest. I was going to do it today because I had a 'jaw appt.' over there and wanted to kill two birds with one stone (it's 90 miles away from where I live). Because of Hurricane Rita my appointment was cancelled until next week and Corpus Christi subsequently evacuated. When I get the bike to the shop I'll likely have to leave it there until my next appointment because they're always very backed up, so backed up that they actually turn people away at times. The bike hasn't been ridden since the wreck, so if there are any possible clues, hopefully they'll be evident upon inspection. I'll post the results of the shop's findings... likely in about 2 weeks.




Very good point! I too considered this after comparing the difference between the brakes on the 2 bikes. The front brake on the bike I wrecked does grip much harder than the front brake on the other bike. The pads on the bike I wrecked are also much grippier (word?) in appearance than those on the other bike. They (the pads) are longer and almost spongy looking (softer with 3 elevated humps? along their length) compared to the other's pads (shorter in length and flatter). If I roll each bike and then grip the front brake, then the wrecked bike's pads 'mega' grip compared to the other bike's 'strong' grip. Sooo, considering that I was unused to riding this bike, and considering that I was riding it the same as I was riding the other bike, yes, I very likely braked too sharply. I don't feel like it was enough to instantaneously flip me, but I guess it's possible considering my inexperience. I've never been a brake jammer or a panicky person, so I find this possibility difficult to accept though. Maybe I will if no mechanical problems turn up. Thank you so much for your suggestions and thoughts. They are very much appreciated!

Sincerely,
Carol

cerewa

Carol:
There are unrelated problems that can be caused by having a frame that's too large for you, but it's not going to make it any more likely for you to flip your bike like you did. ("do an endo.") A frame that's too small for you could put the front wheel to close to being directly below your weight, while a frame that's too large puts the wheel in front of you a bit more.

A lot of people do some pretty hard braking with their butt still on the seat. You shouldn't have to put your butt behind the seat to be safe, but you should know how to do it anyway.

Pay attention Michel's advice to check the frame and fork- if they're damaged the bike needs to be fixed or thrown out.

Also one thing that can contribute to "brake grab" is a loose headset or shock absorber. What can happen is that the looseness in the shock absorber and headset allow the brake to stop the wheel momentarily while the bike (aside from the legs of the front fork) keeps going. Once the brake pads have grabbed the wheel, of course, it takes more to get them to let it turn again than it does to keep them moving in the first place.

cfm

Michel,

There are many lengthwise cracks in the road I was on, just wide enough to grab a front tire too! I'm very aware of (and paranoid of) them though, so avoid them bigtime. I'm certain that my front wheel didn't fall into one of them while I was braking. Good point though! I plan to revisit the area where I wrecked to see if there are any obvious flaws there that could have contributed to the flip. It was very dark out when I wrecked, but my hubby and daughter were behind me in a vehicle with headlights on so I could see the roadway real well. I have a head lamp on the bike that I usually ride, but not on the one I wrecked. That's why they followed me home that particular night. They were on the way home from our local HS track and I'm just thankful that they didn't run right over me.



I can't see anything bent with my untrained eye, but will make sure this is checked out when taken to the shop! The fork and tubes 'appear' true and undamaged...

Thank you,
Carol

cfm

I'm not especially light (140lbs) and my tire pressure is relatively medium (not low, not high)... makes me work a little harder... If I could just narrow the possibilities down to just a few, then it would lessen my fear of the front brake on that particular bike. All this discussion (and reading past threads) is helping quite a bit...



Thank you! Actually, yesterday was better than today. I had my ribs wrapped day before yesterday. It helped the rib pain immensely! Unfortunately, it increased the sternum pain, especially today. Took the wrap off for at least half of today. The Hydrocodone helps immensely too! I don't like to take drugs, but haven't been able to tolerate the pain without them. I try to take them just 3 times/day rather than 4 times/day, which has been tolerable. I've been flying high though since I'm not used to such! IMO, I'm healing very fast. The major bruising is fading rapidly, the road rash scabs are gone with the exception of the deeper gouges (thick scabs!) from the rougher areas of the asphalt, and the jaws don't bother me much (unless I try to chew of course). My ribs and ears have been the biggest aggravation so far, but definitely improving! Tomorrow I'll likely be down to 2 pills/day. I'd be riding again, but I can't justify the 60 miles to a shop to get a tire fixed. I live in the middle of nowhere...



Ouch! I've been stung a lot over the years and it gets worse (the swelling) with each sting. Was working in NW Montana in 1988 and stepped on a yellow-jacket nest (they are ground nesters). I received about 30 stings before I could get far enough away from them (was on a very steep slope). Talk about viscious! I'll never forget that either! Aren't they fun! I hope I don't encounter any on my bike! We have lots of them down here, including the aggresive Africanized variety. Hope you recover soon...

Carol

cfm

Thanks dstrong! I'll keep the shock in mind when braking. I'm learning so much here. Thank you everyone!