Lowside on 84

[EEL]

I had a crash exactly like this on 5 years ago on 84. the rear spun out cuz I got on the gas during a turn. Unfortunately it was a shaded turn and I didn't see the wet patch.

The position of the bike is identical to the way mine ended up. If you've ever taken a dirt bike off a jump the first thing you'll notice is that you can control the angle of the bike based on the relative spin of the back wheel and the front. If you gas it, the bike actually wants to endo. If you slam on the brake in mid air, the front end will nosedive into the ground.

Based on how your bike spun out. Your bike's rear wheel was spinning faster than the front. That means you lost traction on the rear thru the turn.

Why did you lost traction on the rear? My opinion is similar to others prior. You scraped exhaust and your bike skipped out because of it.

I had an old monster 800 w/ low pipes where I did the same thing. I went around the turn and the suspension compressed over a bump. Unlike your incident, the rear end jumped out like it went over a speed bump and then suddenly gripped again. Needless to say I almost got bucked off the bike.

For your kind of bike, its safer to hang off a bit thru turns so you can keep it upright enough to not scrape. If you are getting more confident in your riding and want to keep the bike, a suspension adjustment may help.

 

[mototireguy]

+1 on wearing proper riding gear and walking away with only minor bumps and bruises.

Probably not a factor but what are your tire pressures?

 

[JSGrind]

hey man happy your good! In that situation I think you were going to fast and basically tried to jump into that turn to fast instead of gradually shifting from the right into the turn.

Also did you possibly downshift before the turn?

Sometimes I downshift at around 7, 8k and my bikes back end slides out, I try never to do it but luckily my dirt bike days pay off.

Did it today coming to the onramp of a freeway entrance that cuts hard and I have to drop speed quickly before the turn.

I'm a noob but, If you downshifted in the apex while trying to turn it could have been the culprit.

 

[Lunch Box]

Sometimes I downshift at around 7, 8k and my bikes back end slides out

You may want to start rev-matching, especially during aggressive downshifts.

Also, I see/hear no evidence of downshifting mid-corner in the video posted by the OP.

 

[Cycle61]

EEL: I don't think he crashed because of scraping hard parts. I think he crashed because of his reaction to scraping hard parts. Two very different things.

 

[Kornholio]

Here are some of the things I noticed:

• The line is an early apex as mentioned.
• The throttle is negative for most of the turn.
• Rider increased lean angle (to correct line) just before the bike slid.
• Rider began to open the throttle simultaneously with increasing lean angle.
• The rear came around first.

This looks to me like a case of increasing throttle and lean angle at the same time. It is extremely easy to lose the rear while doing this.

Yep. Agreed.

I see that same thing in these videos a lot...

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[CABilly]

After having closely examined the video and more importantly "audio" portion of the provided video, and combining that info with a viewpoint of someone having logged 120K miles on the very same bike, and having long ago identified its attributes, here's what I believe is the two-part recipe of this crash.

PART 1 (the bike part):

1) What was it that actually triggered the bike's final moment in going down?

- Metal-to-pavement contact at one, or more of the following vulnerable points.

* The foot of the left side of the centerstand
* The foot of the sidestand, and the metal baseplate of the sidestand pivot
* The lower side of the left mid-pipe of the exhaust, right before where it heads into the muffler.

If you listen closely in the video, there's a very defined interval (close to a second?) of a recognized type of "kaaaakkkk" scraping sound (signatory of the parts above touching down), that occurs just BEFORE the bike goes though the actual heading to the ground crashing actions.

I can almost guarantee if you check these locations on the left side of the bike, you'll see noticeable "scraping" evidence is present.

2) What was the impact on the bike of the metal-to-pavement contact at that/those points?

- As the greater and greater amounts of the bike/rider weight was transferred to the metal-to-pavement contact points (as the suspension compressed and the bike was leaned over more in the turn), it eventually leveraged enough weight off the rear tire that it virtually was lifting it off the pavement.

- At the point where insufficient weight remained on the rear tire, it instantly lost traction, and the back end of the bike slid out (first), and the bike lowsided off the road

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PART 2 (the rider's actions part):

Error 1) Initiating the original turn-in event too early for that corner (i.e. "early apexing")

- Result being an early apex, that put the bike on a forced trajectory of heading outward away for the direction of the turn.

Error 2) Being "off-the-throttle" during the first portion of the corner entry, leading up to the point of scraping hard parts

- Result in being off-the-throttle?

* The bike's rear/side ground clearance was reduced (bike squats in rear), because of the absence of needed (on an early-gen Ninja 250) throttle induced "anti-squat" action via the drivechain's action on the swingarm angle

* The front forks were also compressed more than ideal (again reducing the bike's overall ground clearance), due to the extra forward weight bias of being off-the-throttle on corner approach/entry

Error 3) Making a lean angle increase, once already committed into the turn, due to having to tighten up the line to try to fix the improper trajectory (heading wide) of the bike - due to the excessively early apex. This one being a forced action, driven by Error 1 (turning in too early).

Error 4) Not actively working to setup some level of inside body positioning on the bike to reduce the amount of bike lean angle needed for cornering.

Though it's not visible in the video to say with absolute certainty, based on the stated experiece level of the rider, and those aspect that are visible in the footage, I highly believe that some level of this behavior could likely have prevented - or at least reduced the level of - hard parts contact. Perhaps enough to have prevented a full crash.

-------------------------------------------------------------------------

What to do to prevent a similiar event in the future?

- Acquire and read training materials and attend classes to:

1) Develop a better understanding on turn-in points, and target apex locations, for the different types (decreasing apex, increasing, constant - off camber, on-camber, etc) of corners.

2) Develop a better understanding of the dynamic effects that throttle application has on the bike, and learn to develop better throttle control ("roll-on") skills to optimize the safety buffer while riding

3) Learn about the "one steering input/turn" (in most instances) rule, and develop the skills to setup lines for corners that will not create a temptation/need for corrective inputs once into a turn

4) Develop a better understanding on the front/rear weight transfer aspects that occur during downhill riding; and techniques for using rider controls (i.e. throttle input, brake management, etc) to optimize conditions

I firmly believe that all of the above is an accurate post-mortem of the events that transpired before, and during this crash; and list of directly applicable (to this crash) points to focus on learning and improving in the future to minimize the chances of a repeat performance.

Glad you weren't injured Billy and got some great help from the BARF angels (way to go Aaron! ) in getting things sorted and back home. Hope this information above is of some value to you in learning and moving on in your future riding!

I'll check the tire pressures later today. Last I'd checked, they were right where I wanted at 38psi rear and 36 up front.

There was no downshift.

 

[Gary J]

I'll check the tire pressures later today. Last I'd checked, they were right where I wanted at 38psi rear and 36 up front.

Not that tires or tire pressure was worth referencing in the root-cause aspect of a crash analysis on this event; but in seeing your numbers, did want to respond.

I don't know exactly what brand/model of tires you had on this early-gen Ninja 250, but the pressures you quoted (36/38) is excessively high for bias ply tires, used on that 300'ish lb bike.

I'm sure the 38PSI rear, if you saw that recommended anywhere, is accompanied by a notation of "at maximum load" (meaning passenger on back, and saddlebags, etc). That pressure would NOT be appropriate for solo riding with any tires I'm aware of, on that bike.

With the Dunlop GT-501 tires on the early-gen Ninja 250's, something in the 28-30PSI (or below) range, is what gives the best overall balance of grip, handling, and reasonable longevity.

Running too much tire pressure will reduce the hard sidewall bias-ply tire's flexibility in building up a good amount of temperature and finding best grip with irregular pavement surfaces. Too little, or too much pressure is never good.

Check the owner's manual with the bike and you'll see the much lower numbers I mentioned here.

One small part of the equation in making the bike the safest it can be for riding!

 

[GAJ]

28/32 for the new Ninja 250r in the manual...so 36/38 is way over the top as Gary says.

 

[CABilly]

Oh wow. Thanks. The tires are Pirelli MT75's. I had originally had them lower, then the guy at the tire shop said it was way too low and recommended I bump it up to those numbers.

Getting straight answers on this stuff, it seems, is a task all its own.

 

[Lunch Box]

Bear in mind that if you are a fat bastard like I am, you may want to add a couple of psi to those numbers. Having met you, this is not the case, but wanted to put the info out there for any fat noobs who may be reading

 

[morthrane]

One thing I'm surprised-- that specific corner is red flagged in my mind, and I usually take care to go in extra slow and a very wide/late apex. See the oncoming car in the video? You can see a flash of it going forward, and then at the end when they stop/turn around. (one of those corners where cages seem to blow the corner more than normal...) Makes me wonder if the OP flinched when he saw it.

Is it possible the tar snakes got your rear loose?

Unless something's changed recently, no. There's tar snakes on the approach but not in the actual corner itself. You can see this in the video as well.

 

[Cycle61]

Bear in mind that if you are a fat bastard like I am, you may want to add a couple of psi to those numbers. Having met you, this is not the case, but wanted to put the info out there for any fat noobs who may be reading

For the record, I'm a fat bastard like Aaron here, and I race my old-gen 250 with the tires at roughly 29 psi, front and rear.

 

[Lunch Box]

For the record, I'm a fat bastard like Aaron here, and I race my old-gen 250 with the tires at roughly 29 psi, front and rear.

Yeah, but race pressures are always lower than street pressures (for me at least). If you rode that 250 on the street, I bet you would be at 30-32 front and rear.

 

[Enchanter]

Rather than just going on about what pressures you guys run in your bike(s), how can we tie this into being relevant to this crash?

 

[Gary J]

Rather than just going on about what pressures you guys run in your bike(s), how can we tie this into being relevant to this crash?

Based on the video, the character of the bike in question and the section of road, tire pressure change would have had zero impact on preventing this particular crash.

For the OP to be educated (via this thread) that the tire pressures he's been running are in fact TOO HIGH for optimum road grip, performance, and safety, is however one quick value-add point to make (and move on) however.

 

[Enchanter]

Based on the video, the character of the bike in question and the section of road, tire pressure change would have had zero impact on preventing this particular crash.

For the OP to be educated (via this thread) that the tire pressures he's been running are in fact TOO HIGH for optimum road grip, performance, and safety, is however one quick value-add point to make (and move on) however.

Perfect. Clear and to the point. Thanks Gary!

 

[mototireguy]

Rather than just going on about what pressures you guys run in your bike(s), how can we tie this into being relevant to this crash?

In my experience 38psi tire pressures are what I would recommend for heavy 500-600 pound motorcycles.

For a lightweight 300 pound Ex250 I would recommend tire pressures in the 30-32psi range.

If indeed the OP was running 38psi then I would submit that tire pressures are very much relevant to this unfortunate mishap.

 

[Gary J]

If indeed the OP was running 38psi then I would submit that tire pressures are very much relevant to this unfortunate mishap.

Normally yes, but in the case of the bike type involved in this crash, and a very direct knowledge of the ground clearance limitations/issue and impact of a hard part touchdown on this bike, totally disagree that tire pressure would have had any impact on a crash? or no-crash? outcome in this particular instance for Billy.

Once the hard parts (centerstand/exhaust pipe) on an early-gen Ninja 250 touch pavement with enough force, when the bike is leaned over too far at a time that the suspension extensively compressed, it will literally leverage (high-center) the rear tire to the point that it basically has no weight left on it.

A tire that is not touching the ground, or barely doing so with minimal weight applied (in such a scenario), really doesn't care if it has 50PSI or 10PSI. The traction level with the pavement floating below will still be ZERO (or near zero depending on the weight remaining on it), and a crash is in the works.

 

[GAJ]

Normally yes, but in the case of the bike type involved in this crash, and a very direct knowledge of the ground clearance limitations/issue and impact of a hard part touchdown on this bike, totally disagree that tire pressure would have had any impact on a crash? or no-crash? outcome in this particular instance for Billy.

Once the hard parts (centerstand/exhaust pipe) on an early-gen Ninja 250 touch pavement with enough force, when the bike is leaned over too far at a time that the suspension extensively compressed, it will literally leverage (high-center) the rear tire to the point that it basically has no weight left on it.

A tire that is not touching the ground, or barely doing so with minimal weight applied (in such a scenario), really doesn't care if it has 50PSI or 10PSI. The traction level with the pavement floating below will still be ZERO (or near zero depending on the weight remaining on it), and a crash is in the works.

Yes, but if the hard parts were touching because of loss of traction, then it could, indeed, have been the direct cause.

Can't really tell whether the rear was breaking loose due to loss of traction before the hard parts started touching down...the OP could chime in an tell us whether or not scraping of hard parts was a "normal" part of his cornering experiences or one in a million.