Hard braking = front end bounce?

[tecknojoe]

I have this on another forum but theres a couple guys that I'd love to hear from about this on COsportbikes, so here goes

So I'm riding at Le Mans (omgz I know right), and I'm starting to brake a lot harder. Every once in a while, when I'm really giving it the beans, the back end starts to dance around (which I'm fine with by now), but I notice it feels like the front is bouncing up and down.


What exactly is happening?


See the vid here at the 1:13 mark it does it a little bit, at the 4:30 mark I accidently click 1st and it REALLY bounces hard


No Limits Fast Group Le Mans, R6, Sept 2014 - YouTube

[justinyzfr6]

There could be a few thinks to check and rule out. The backing plate on your brake pads could be warped, and since you said you are braking a lot later which means you are giving them a lot more heat than before. If that is not the issue you could try and back your preload out a little bit, too much preload can make the bike want to "po-go stick" under heavier loads. The last thing I would check if those are not the issue would be head bearings.

[asp_125]

Nothing to add 'cept OMGZ Jelly!

[tecknojoe]

oh it's a rented bike so i had never ridden it before and won't ride again. I'm guessing we maybe didn't finish seting up the suspension on the first day. I felt nothing in the lever to make me think it was a warped rotor or pad

and yea it was hands down the best track i've ever ridden. turn one..... phew

[The Black Knight]

Yeah nothing really to add either except, super extra jealousy over here.

[tecknojoe]

I suppose I could add a bit more detail

Turns out I was pitted next to former MotoGP rider (and one time winner) Simon Crafar. So I paid the man and went out on track for the best and most hard working session of my life. That man was out of his fucking mind. He had me braking way later and the backend moving all over the place. I dropped 5 seconds in 1 lap with him. It was a pretty killer 2 day event

Also, Mark Marquez is 22 seconds faster than me

also also, I may have ridden silverstone this summer as well. and I may have gone to the TT

[Skitz]

So much jell... pffffffffffffffffffffffffff.

[madvlad]

I hate you, you're not getting your trailer back

[tecknojoe]

I hate you, you're not getting your trailer back

I'll race you for it....

[madvlad]

Well played haha, I got slightly better but not hardcore trailbraking good, yet lol

[dirkterrell]

Sounds like the front end might have been under-sprung. If the forks were buried, even small bumps on the track would become very apparent.

[The Black Knight]

I suppose I could add a bit more detail

Turns out I was pitted next to former MotoGP rider (and one time winner) Simon Crafar. So I paid the man and went out on track for the best and most hard working session of my life. That man was out of his fucking mind. He had me braking way later and the backend moving all over the place. I dropped 5 seconds in 1 lap with him. It was a pretty killer 2 day event

Also, Mark Marquez is 22 seconds faster than me

also also, I may have ridden silverstone this summer as well. and I may have gone to the TT

Yeah, I'm with Damir. I hate you HAHAHA!! I'm so jelly over here!!!

FWIW, being 22 seconds down on Marquez is pretty solid man. I would be happy to be 22 seconds down on Marquez at that track. You were on a R6 and he's on a full flown prototype 1000cc bike. Putting it into perspective that's awesome the speed you have.

You mentioned you were on a rental bike. How did you manage to not only get on Le Mans but get a rental bike for it?? Is this something many of the top level tracks over there in Europe do? If that's the case, I'm so going to figure out how I can get over to Catalunya or Mugello with a rental bike that I can flog for a couple days.

Great video by the way. I agree with what others here have mentioned. With the fact you're braking so much later now, you're over powering the brakes of the bike. Causing it to load down the front forks and you're getting that "chatter" or "pogo" effect. I had the same thing happen on my old gixxer years ago. It would chatter on turn 9 at PMP(not all the time in that corner). I think it comes from just getting close to exceeding the limits of a bike with stock suspension components. Is the R6 stock or does it have upgraded suspension??

[tecknojoe]

There's an org called No Limits that does UK track days, and some Euro days at places like Le Mans, Aragon, Valencia, etc. I did silverstone and rented from a company called SmallBoy (gxsr 600 above). At the time they said they don't go to france (although it looks like they just changed that), so I asked another rental guy while I was at silverstone and he rented me an R6. So me and a few guys packed a couple vans and drove from England to Le Mans (I've been living in England btw).

It was a killer trip but VERY expensive. The bike was 440 brittish pounds, track day was 250, then fuel hotels and toll roads. It cost me roughly $1,500 for those two days at le mans. Then I also paid Simon Crafar a good amount to do an hour of instruction with me, best money I've ever spent.

The R6 I was on in the vid has racetech fork parts and ohlins in the back, and I had the ohlins guy help me with suspension. Maybe we just didn't really finish the setup and I started to discover the bouncing after riding with simon and braking harder on day 2

When I got to the hot pit after our session, I looked at simon and told him it was the most fun I've ever had on a motorcycle

Crafar and Me



Just me

[The Black Knight]

There's an org called No Limits that does UK track days, and some Euro days at places like Le Mans, Aragon, Valencia, etc. I did silverstone and rented from a company called SmallBoy (gxsr 600 above). At the time they said they don't go to france (although it looks like they just changed that), so I asked another rental guy while I was at silverstone and he rented me an R6. So me and a few guys packed a couple vans and drove from England to Le Mans (I've been living in England btw).

It was a killer trip but VERY expensive. The bike was 440 brittish pounds, track day was 250, then fuel hotels and toll roads. It cost me roughly $1,500 for those two days at le mans. Then I also paid Simon Crafar a good amount to do an hour of instruction with me, best money I've ever spent.

The R6 I was on in the vid has racetech fork parts and ohlins in the back, and I had the ohlins guy help me with suspension. Maybe we just didn't really finish the setup and I started to discover the bouncing after riding with simon and braking harder on day 2

When I got to the hot pit after our session, I looked at simon and told him it was the most fun I've ever had on a motorcycle

Crafar and Me



Just me

Man that sounds amazing!!! Must be such an unbelievable experience to not only ride some world class level circuits but to have some excellent instruction as well. You're right, it would be best money ever spent as it's knowledge and instruction that you'll carry on for the rest of your life. Very very cool!!

[Drano]

Sounds like a dream vacation to me! Very, very awesome! Thanks for sharing!

[WolFeYeZ]

I have this on another forum but theres a couple guys that I'd love to hear from about this on COsportbikes, so here goes

So I'm riding at Le Mans (omgz I know right), and I'm starting to brake a lot harder. Every once in a while, when I'm really giving it the beans, the back end starts to dance around (which I'm fine with by now), but I notice it feels like the front is bouncing up and down.


What exactly is happening?


See the vid here at the 1:13 mark it does it a little bit, at the 4:30 mark I accidently click 1st and it REALLY bounces hard


No Limits Fast Group Le Mans, R6, Sept 2014 - YouTube

Hey Joe, your lines on those complex corners were amazing. I'm super jealous. You are going to kick some major ass our here next season. .

As for the bounce, I recently experienced what I think is the exact same problem at round 3 this year after changing out my clutch. Under hard braking and a couple downshifts it would shudder and bounce in the front. Scary stuff. I originally thought it was a problem with my front brakes or suspension, but I am pretty sure it was the rear tire locking up and bouncing... I ended up being a bit smoother on the clutch when downshifting and it solved the problem. I think it was the slipper not quite being able to keep up with my dumping the clutch after a few downshifts. Before the clutch change, dumping the clutch going from 5th to 2nd would be perfectly fine =/. Meh, being smoother on the clutch is fine... just takes a little more attention off of the actual corner.

[rybo]

Joe,

1st - count me as amongst the jealous.

2nd- the bounce you experience at 1:13 in the video is 100% a rear wheel problem and cannot be solved with a frond end adjustment. What is happening is that you are simultaneously hard on the front brake (=near 100% weight transfer to the front wheel) and back torque loading the engine, which is a lot like putting on the rear brake.

Net result is is that as the rear tire makes intermittent contact with the ground, it tries to "stretch" the bike out, transferring weight back to the rear wheel. The tire then loses grip again (due to the engine braking) and skips. This unloads the rear wheel and transfers weight back to the front. This back and forth weight transfer is what you feel as a bounce in the front end.

Solution? Let the clutch out more slowly. Watch the Moto GP videos of the fast guys clutch hands when they are entering the corners. When is the clutch fully out? Sometimes not until the apex. It's an easy thing to understand, but difficult to put into practice.

Good luck! Can't wait to see you back stateside!
scott

[tecknojoe]

Hey Joe, your lines on those complex corners were amazing. I'm super jealous. You are going to kick some major ass our here next season. .

As for the bounce, I recently experienced what I think is the exact same problem at round 3 this year after changing out my clutch. Under hard braking and a couple downshifts it would shudder and bounce in the front. Scary stuff. I originally thought it was a problem with my front brakes or suspension, but I am pretty sure it was the rear tire locking up and bouncing... I ended up being a bit smoother on the clutch when downshifting and it solved the problem. I think it was the slipper not quite being able to keep up with my dumping the clutch after a few downshifts. Before the clutch change, dumping the clutch going from 5th to 2nd would be perfectly fine =/. Meh, being smoother on the clutch is fine... just takes a little more attention off of the actual corner.

Thanks Brad!

You know that brings up another conversation I had with someone. I'm not sure if it's true because I had never used a slipper until this year (omg was I missing out for all those years). My buddy said since I was now braking much harder, I was loading up the front and leaving no real weight on the back wheel. Since there was no weight, the was nothing to force the clutch to actually do the slipping (via my weight on the back tire and friction causing the tire to want to keep spinning). So with what he said, I'm guessing if you dump a few gears while the rear wheel is up on a stand, you would get more lockup. I'm wondering if that's true

Joe,

1st - count me as amongst the jealous.

2nd- the bounce you experience at 1:13 in the video is 100% a rear wheel problem and cannot be solved with a frond end adjustment. What is happening is that you are simultaneously hard on the front brake (=near 100% weight transfer to the front wheel) and back torque loading the engine, which is a lot like putting on the rear brake.

Net result is is that as the rear tire makes intermittent contact with the ground, it tries to "stretch" the bike out, transferring weight back to the rear wheel. The tire then loses grip again (due to the engine braking) and skips. This unloads the rear wheel and transfers weight back to the front. This back and forth weight transfer is what you feel as a bounce in the front end.

Solution? Let the clutch out more slowly. Watch the Moto GP videos of the fast guys clutch hands when they are entering the corners. When is the clutch fully out? Sometimes not until the apex. It's an easy thing to understand, but difficult to put into practice.

Good luck! Can't wait to see you back stateside!
scott

Thanks Scott! I was definitely being hard on downshifting and the backend was moving around / skipping a lot. I just have to make sure I always let the bike settle before I get it leaned over! I'll focus on being smoother on the clutch on my next time out and see what kind of results I can get

Can't wait to get home and ride with the MRA again!