Motorcycle braking questions - unusual evidence

Craig · Member

Motorcycle braking questions - unusual evidence

BlueB · Veteran Member

Lots of reasons why the rider may have chosen to have stopped braking, either due to the displacement of himself, the passenger or simply rider decisions as you suggest. evidentially it is unlikley that you will be able to identify a cause as some do not leave evidence.
Assessment on the marks seems reasonable.
You mention the marks stop 1.2m short of there the impact occurred. Is that based upon evidence or a surmation of where the truck was likely to have been.

Craig · Member

Thanks Andy for the input. The 1.2m short is based on the likely trajectory of the path of the truck, as we have not had this driver`s confirmation yet. However having reviewed the evidence again, I see that I may have misread the tyre mark, it seems more feasible that the last section of the braking mark (4.7) was the continuation of the rear wheel lockup and that the first part of the braking mark (7.1m) where the was a superimposed mark, is likely to have been the front wheel braking, and that the rider released the front brake. My rational for this is that the remaining 1.2m fits almost perfectly with the wheel base of the m/cycle where the end of the braking mark is the rear wheel position, then the front of the cycle would be at impact. This would obviously then resolve the theory of his having released the brake before impact. I have reasoned then that the release of the front brake may have been where the ride felt like that the front may have been about to "wash out", or that his hand simply slipped off the bars/lever during braking, you are right, I suppose we will never really know. Speed was calc. for the distance and given braking % variables, at 39.95km/h, interestingly a comparison by using Severy, ON A 28cm reduction of the forks, resulted in 55.25km/h impact speed.

BlueB · Veteran Member

Interesting to know the question being asked. Is it asking what was the impact or initial speed for the m/c, the impact or initial speed for the truck or more intrestingly what could the m/c have done to have realistically or effectively reduced the impact. The less issues with the biker, the more tend towards the truck.
The thing about analysis of photos is it always helps to have several and hi-def to allow zooiming in.

omegacrash · Veteran Member

Craig,
Alot of times, when a motorcyclist sees that a crash is unavoidable, an experienced rider will want to try to put the bike down before striking an object. The easiest way to do this is to lock up both wheels of the bike, or at least lock up the front wheel. The motorcycle will stay up as long as the wheels are turning fast enough. Once the wheels stop turning the bike will go down, especially if the front wheel is locked. This is what he may have tried to do. Or, if the rider is not that experienced, he found out the hard way that when he locks up the front wheel, he is going down. It is possible that once this happened he let go of the front brake before going down. If the bike is going fast enough, releasing the front brakes can cause the bike to straighten back up quickly and rattle the riders. This would cause the riders foot to come off the brake because the bike would straighten up so quickly, it could cause the riders to come off the seat of the bike, thus causing his foot to come off the rear brake. With the information you supplied, it kind of looks like that is what happened.

Craig · Member

Thanks for the input gents, much appreciated. Andy, I was asked to do a full investigation, recon, cause analysis, largely as the client wanted to know where he stands in terms of possible civil actions and the success there of, and due to the fact that the police appear to have done a rather poor job. As such, I have been dealing with all the issues, i.e. speed of cycle, truck, visibility for both, reaction times etc etc, hence my research / questions on the braking marks suddenly stopping / changing etc. I have taken detailed pics and they are available should you want to review them as interest, however as i`m sure you agree posting them all is somewhat tedious. Thanks again for the input, much appreciated, always interresting to see others viewpoint.