Understeer/Front end push problem
#1
Understeer/Front end push problem
I low sided my bike about a month ago at a track day. Front end washed out and I attributed it to an old front tire and poor riding skills.
With fresh BT014's on Sunday, I again low sided, this time on the other side of the bike. I was in a line of 15 other sport bike riders and we were making a nearly 90 degree right hand turn entering an on ramp (very good clean pavement). I slide my *** over, giver a bit and down I go like a sack of potatoes. No injuries other than, again, bruised ribs.
The previous night I had been bombing around like a mad man on my buddies done up '02 GSXR750, so I attributed this accident to trying to ride my Hawk like a racer replica.
Then a couple of friends came forward and we started talking. Friend "A" is an ex-racer and wouldn't ride anything other than a hawk on the street. He said my problem is the bike and says that stock VTR's are prone to "front end push" beause there isn't enough weight on the front ie: when accelerating while hard over, the front doesn't bite and the bike goes straight.
Now that I know that I suppose I should have thrown my weight over the tank BUT since Hawks also deck out very quickly your supposed to "hang off them like a monkey" compared to other bikes
After only twice in the seat of the Gixxer I feel like I can ride it better than two seasons on my Hawk. However I love the motor and the seating position PLUS the race replica bikes urge me to drive them hard like getting a lap dance ... so I don't trust myself. This forces me to fix the problem I didn't know I had but a lot of you guys already know the fix.
Shim the rear shock and lower the front end. I had read about doing that here but I am afraid of getting a tank slapper at 240kmh. Still my riding habits require changing the bikes geometry and maybe getting a damper.
Friend "B" says my front springs are too hard and that getting softer springs and setting the suspension for the turn should pull me through - oh ya and "slow the f*** down". (1kg springs, me = 184lbs sans gear).
I know more than a few of you race and ride hard, what do you say?
With fresh BT014's on Sunday, I again low sided, this time on the other side of the bike. I was in a line of 15 other sport bike riders and we were making a nearly 90 degree right hand turn entering an on ramp (very good clean pavement). I slide my *** over, giver a bit and down I go like a sack of potatoes. No injuries other than, again, bruised ribs.
The previous night I had been bombing around like a mad man on my buddies done up '02 GSXR750, so I attributed this accident to trying to ride my Hawk like a racer replica.
Then a couple of friends came forward and we started talking. Friend "A" is an ex-racer and wouldn't ride anything other than a hawk on the street. He said my problem is the bike and says that stock VTR's are prone to "front end push" beause there isn't enough weight on the front ie: when accelerating while hard over, the front doesn't bite and the bike goes straight.
Now that I know that I suppose I should have thrown my weight over the tank BUT since Hawks also deck out very quickly your supposed to "hang off them like a monkey" compared to other bikes
After only twice in the seat of the Gixxer I feel like I can ride it better than two seasons on my Hawk. However I love the motor and the seating position PLUS the race replica bikes urge me to drive them hard like getting a lap dance ... so I don't trust myself. This forces me to fix the problem I didn't know I had but a lot of you guys already know the fix.
Shim the rear shock and lower the front end. I had read about doing that here but I am afraid of getting a tank slapper at 240kmh. Still my riding habits require changing the bikes geometry and maybe getting a damper.
Friend "B" says my front springs are too hard and that getting softer springs and setting the suspension for the turn should pull me through - oh ya and "slow the f*** down". (1kg springs, me = 184lbs sans gear).
I know more than a few of you race and ride hard, what do you say?
#2
Re: Understeer/Front end push problem
I't may not be all the suspension's fault.
Did you scuff the tires in good before you hit that first corner?
Did you have the tires up to temp?
I did the exact same thing on my old interceptor with brand new cold tires.
Now I put new tires thru a couple of heat cycles before taking to the corners gradually getting a little more lean with each turn.
I go thru 2 rear Dunlop 208zr's for every front and can really tell a difference with a new(and slippery) rear tire and a half used( but sticky) front tire. After about an 1/2 hour of riding corners the back tire will start to hook up as well as the front.
just my 2 cents
Shane
Did you scuff the tires in good before you hit that first corner?
Did you have the tires up to temp?
I did the exact same thing on my old interceptor with brand new cold tires.
Now I put new tires thru a couple of heat cycles before taking to the corners gradually getting a little more lean with each turn.
I go thru 2 rear Dunlop 208zr's for every front and can really tell a difference with a new(and slippery) rear tire and a half used( but sticky) front tire. After about an 1/2 hour of riding corners the back tire will start to hook up as well as the front.
just my 2 cents
Shane
#3
The mold release agent on new tires requires a 100 mile break-in for optimum traction. If your new tires were still "green" you may be able to attribute some traction issues to that.
The front end weight comment is 100% wrong. If that were true, all the raked out cruisers on the street wouldn't be able to take a curve any faster than about 10 mph. By the very nature of the design of ANY modern sportbike, the weight is heavily biased toward the front, not to mention the riding position moves the rider's center of gravity forward of the midline of the bike, which weights the front even more. You don't need to have your *** 10 feet in the air and your triple clamps sitting on your fender to get forward weight bias...it's already there in spades. Honda would never sell a bike that, by its design, would consistently wash out the front on a fast, tight corner.
Friend B is absolutely correct. Your springs are too stiff for you. You should be running 85 or 90 springs on the front. This will contribute to pushing, but isn't solely responsible. Plus, you don't need to carry as much speed into a corner to beat the I-4s out. Try some trail braking to weight the front on corner entry and roll on smoothly as you near the apex. Hanging off like a monkey is never recommended on the street. Move off the seat, to the inside, but keep your knee tucked, and get your weight low and forward. Pivot at your hips, and support your weight with your legs, back, and abs. You shouldn't feel your weight on your wrists at all. This keeps you from making unintentional steering inputs while you shift your body position. Move the bike around using your knees' grip on the tank and your position on the bike. Countersteering should be incidental, with no relation to what's happening with your body position. As you lean down and to the inside of the turn, your arms will almost automatically countersteer. Hanging way off the bike on any corner you'll encounter on the street will move you too far away from your control surfaces, and probably cause the bike to oversteer, which will cause over-correction with the throttle, making a low-side more likely.
Go through a proper static suspension setup, and take a cue from martial artists. Practice proper form slowly first, and the speed will come with proficiency. Glad you didn't get hurt bad. Keep us posted.
The front end weight comment is 100% wrong. If that were true, all the raked out cruisers on the street wouldn't be able to take a curve any faster than about 10 mph. By the very nature of the design of ANY modern sportbike, the weight is heavily biased toward the front, not to mention the riding position moves the rider's center of gravity forward of the midline of the bike, which weights the front even more. You don't need to have your *** 10 feet in the air and your triple clamps sitting on your fender to get forward weight bias...it's already there in spades. Honda would never sell a bike that, by its design, would consistently wash out the front on a fast, tight corner.
Friend B is absolutely correct. Your springs are too stiff for you. You should be running 85 or 90 springs on the front. This will contribute to pushing, but isn't solely responsible. Plus, you don't need to carry as much speed into a corner to beat the I-4s out. Try some trail braking to weight the front on corner entry and roll on smoothly as you near the apex. Hanging off like a monkey is never recommended on the street. Move off the seat, to the inside, but keep your knee tucked, and get your weight low and forward. Pivot at your hips, and support your weight with your legs, back, and abs. You shouldn't feel your weight on your wrists at all. This keeps you from making unintentional steering inputs while you shift your body position. Move the bike around using your knees' grip on the tank and your position on the bike. Countersteering should be incidental, with no relation to what's happening with your body position. As you lean down and to the inside of the turn, your arms will almost automatically countersteer. Hanging way off the bike on any corner you'll encounter on the street will move you too far away from your control surfaces, and probably cause the bike to oversteer, which will cause over-correction with the throttle, making a low-side more likely.
Go through a proper static suspension setup, and take a cue from martial artists. Practice proper form slowly first, and the speed will come with proficiency. Glad you didn't get hurt bad. Keep us posted.
#4
Re: Understeer/Front end push problem
I read a Shawk test in Cycle Canada mag recently that said there is a higher than nomal rear weight bias on this bike (they did front & rear measurements). They said that this may be the reason for the bars being so relatively low for the focus of the bike. I wonder if this is more of a problem after puting VFR bars on (I have a set to install).
#5
Guest
Posts: n/a
I agree with Adam.
I go around every make of sport bike at the track, inside and outside in the corners, like I'm riding on a rail. I don't do anything excessive as far as moving around on the bike.
My rear shock is 5mm longer than stock, head height very close to stock. the biggest problem I have is dragging parts on the ground (lower fairing on the right, kickstand on the left). My fork springs are still stock RC51, which run about .97kg/mm. Too stiff for me at 180 lbs suited weight.
A couple things regarding tires:
I don't corner fast unless I have gotten the tires warm and I'm in full leathers in sport mode. Even then I go fast between corners and brake hard to keep corner speed moederate for safety margin (talking street riding here).
On the track I [U]never[U] run street tires. Always a DOT race compound. I've been told that 70% of trackday crashes happen on street tires. I run the same tires on the street and really like them.
I'm glad you're ok and REALLY glad to hear you've found a way to get some track time in. I hope this helps.
I go around every make of sport bike at the track, inside and outside in the corners, like I'm riding on a rail. I don't do anything excessive as far as moving around on the bike.
My rear shock is 5mm longer than stock, head height very close to stock. the biggest problem I have is dragging parts on the ground (lower fairing on the right, kickstand on the left). My fork springs are still stock RC51, which run about .97kg/mm. Too stiff for me at 180 lbs suited weight.
A couple things regarding tires:
I don't corner fast unless I have gotten the tires warm and I'm in full leathers in sport mode. Even then I go fast between corners and brake hard to keep corner speed moederate for safety margin (talking street riding here).
On the track I [U]never[U] run street tires. Always a DOT race compound. I've been told that 70% of trackday crashes happen on street tires. I run the same tires on the street and really like them.
I'm glad you're ok and REALLY glad to hear you've found a way to get some track time in. I hope this helps.
#6
I agree with Adam.
I go around every make of sport bike at the track, inside and outside in the corners, like I'm riding on a rail. I don't do anything excessive as far as moving around on the bike.
My rear shock is 5mm longer than stock, head height very close to stock. the biggest problem I have is dragging parts on the ground (lower fairing on the right, kickstand on the left). My fork springs are still stock RC51, which run about .97kg/mm. Too stiff for me at 180 lbs suited weight.
A couple things regarding tires:
I don't corner fast unless I have gotten the tires warm and I'm in full leathers in sport mode. Even then I go fast between corners and brake hard to keep corner speed moederate for safety margin (talking street riding here).
On the track I [U]never[U] run street tires. Always a DOT race compound. I've been told that 70% of trackday crashes happen on street tires. I run the same tires on the street and really like them.
I'm glad you're ok and REALLY glad to hear you've found a way to get some track time in. I hope this helps.
I go around every make of sport bike at the track, inside and outside in the corners, like I'm riding on a rail. I don't do anything excessive as far as moving around on the bike.
My rear shock is 5mm longer than stock, head height very close to stock. the biggest problem I have is dragging parts on the ground (lower fairing on the right, kickstand on the left). My fork springs are still stock RC51, which run about .97kg/mm. Too stiff for me at 180 lbs suited weight.
A couple things regarding tires:
I don't corner fast unless I have gotten the tires warm and I'm in full leathers in sport mode. Even then I go fast between corners and brake hard to keep corner speed moederate for safety margin (talking street riding here).
On the track I [U]never[U] run street tires. Always a DOT race compound. I've been told that 70% of trackday crashes happen on street tires. I run the same tires on the street and really like them.
I'm glad you're ok and REALLY glad to hear you've found a way to get some track time in. I hope this helps.
Now get me pics of your stock debaffled superhawk exhaust and your e-mail addy for paypal
#7
Re: Understeer/Front end push problem
Thanks for the well thought out and written replies. Yet another great example of why this forum rocks.
I figured it had to have something to do with me and the bike setup but the "these bikes are prone to push" comment bothered me.
The tires had about 800kms on em BUT we had been waiting about 15-20 minutes for some riders to catch up who'd taken a wrong turn.
Can tires cool off in 20 minutes?
The idea that the VFR bars pushes back the centre of gravity is good but I don't think I was leaning back because of them.
Hindsight i should have:
- warmed up the tires more
- not thrown it over so hard going into the corner
- .9kg springs
- 5mm shock shim
PS: I always wear full armored leathers
I figured it had to have something to do with me and the bike setup but the "these bikes are prone to push" comment bothered me.
The tires had about 800kms on em BUT we had been waiting about 15-20 minutes for some riders to catch up who'd taken a wrong turn.
Can tires cool off in 20 minutes?
The idea that the VFR bars pushes back the centre of gravity is good but I don't think I was leaning back because of them.
Hindsight i should have:
- warmed up the tires more
- not thrown it over so hard going into the corner
- .9kg springs
- 5mm shock shim
PS: I always wear full armored leathers
#8
Guest
Posts: n/a
[quote="Utah996";p="9139
Now get me pics of your stock debaffled superhawk exhaust and your e-mail addy for paypal [/quote]
I think about it sometimes. Just not when I'm at home. I should really do it because I can't believe somebody wants to pay me for some hacked up mufflers!
:P
Now get me pics of your stock debaffled superhawk exhaust and your e-mail addy for paypal [/quote]
I think about it sometimes. Just not when I'm at home. I should really do it because I can't believe somebody wants to pay me for some hacked up mufflers!
:P
#9
Re: Understeer/Front end push problem
Based on my experience (had several episodes of front tire breaking free - I just got lucky and didn't go down), I'd say Adam is dead on.
In my case it was: tires and suspension set up.
I switched to Pilot Powers and they stick like glue.
I backed off the front preload (and adjusted damping just a little) to allow the front in to load a little better and avoid stacking, and the darn thing works great now.
What was your tire pressure? - just curious.
I can - and do - run both front and rear tires all the way to the edge. Yes, I hang off and drag a knee, but not to the point of looking like a monkey as you describe. The only time a tire breaks free is the occasionl spin of the rear, and it is predictable and manageable when it occurs. (for clarity, it is not an unexpected event, it is something I coax out of the bike - said another way - I do it on purpose.)
As you get the bike further and further over, you'll start to notice your knee seems to be pointing to towards the front of the bikes rather than down at the road. That's when it starts getting fun, as your knee is on the ground before you even expect it and you have to keep your knee tucked in a little to satisfy the lean angle you need.
Anyways, back to the subject: Yes, SOMETHING was wrong, and any or all of the previsouly mentioned factors might have contributed.
Because, a SH with good tires and good suspension set-up (mines even all factory except for 10 weight fork oil) can power thru turns at some pretty impressive lean angles and never give you a scare.
BTW- What works well for me is a late break, flopping the bike into the turn and roll hard on the gas. I don't start the turn too early as it will cause me to push wider on the exit. This is less fun and more dangerous as it drives me closer to any oncoming traffic (not a problem if you are on the track).
Keep us posted on how things turn out.
Thanks,
Brian
edit to add: look at RC996's avatar. See how he has his elbows bent and is "scooched" forward on the bike? That makes a BIG difference. It helps provide a smooth transfer of weight to the front end and shifts the center of gravity down and towards the front.
A front tire not loaded properly will push. It's gotta' have some weight on it to keep it stuck.
We can't forget, much of the forces applied in a turn are forcing the tire lateral to the pavement. Only the sine (or is it cosine?) of the angle times the force applied in-line with the forks, is what is pushing the tire down (the "normal force") Pretty darned impressive what good tires can do!
In my case it was: tires and suspension set up.
I switched to Pilot Powers and they stick like glue.
I backed off the front preload (and adjusted damping just a little) to allow the front in to load a little better and avoid stacking, and the darn thing works great now.
What was your tire pressure? - just curious.
I can - and do - run both front and rear tires all the way to the edge. Yes, I hang off and drag a knee, but not to the point of looking like a monkey as you describe. The only time a tire breaks free is the occasionl spin of the rear, and it is predictable and manageable when it occurs. (for clarity, it is not an unexpected event, it is something I coax out of the bike - said another way - I do it on purpose.)
As you get the bike further and further over, you'll start to notice your knee seems to be pointing to towards the front of the bikes rather than down at the road. That's when it starts getting fun, as your knee is on the ground before you even expect it and you have to keep your knee tucked in a little to satisfy the lean angle you need.
Anyways, back to the subject: Yes, SOMETHING was wrong, and any or all of the previsouly mentioned factors might have contributed.
Because, a SH with good tires and good suspension set-up (mines even all factory except for 10 weight fork oil) can power thru turns at some pretty impressive lean angles and never give you a scare.
BTW- What works well for me is a late break, flopping the bike into the turn and roll hard on the gas. I don't start the turn too early as it will cause me to push wider on the exit. This is less fun and more dangerous as it drives me closer to any oncoming traffic (not a problem if you are on the track).
Keep us posted on how things turn out.
Thanks,
Brian
edit to add: look at RC996's avatar. See how he has his elbows bent and is "scooched" forward on the bike? That makes a BIG difference. It helps provide a smooth transfer of weight to the front end and shifts the center of gravity down and towards the front.
A front tire not loaded properly will push. It's gotta' have some weight on it to keep it stuck.
We can't forget, much of the forces applied in a turn are forcing the tire lateral to the pavement. Only the sine (or is it cosine?) of the angle times the force applied in-line with the forks, is what is pushing the tire down (the "normal force") Pretty darned impressive what good tires can do!
#11
Guest
Posts: n/a
Re: Understeer/Front end push problem
I was laying in bed thinking about this story last night and it reminds me of a similar story...
It goes back to the fall of 2002, the first year on my VTR. I had replaed the shock and fork springs and revalved the forks but otherwise stock. I rode about 8000 miles that summer, mostly solo on twisty roads (lucky for me, that's about all there is around here). I was getting pretty comfortable with the 100HP Super Beast between my legs. My friend Bob had been warning me about riding with other people and getting pulled in over my head, so I always had that in mind.
Anyway, this is not really about me. I was with a group of 5. 2 RC51s, an R1 and a Ducati 998. The riders on the '51s and the R1 had quite a bit of track experience and had been riding a long time. Not sure how much experience Dustin had, but that Duc sure was exotic.
So off we went over Monitor Pass. I had ridden it several times, both in previeous years and almost every week that summer. I was leading and riding at a "comfortable pace". We got to the top and Dustin came roaring by. We all let him go. He'd never ridden the road before.
The descent starts out with some sweepers then has a couple hairpins. I saw him coming out of the frist one from above. At the next one he lowsided and was all wadded up in the gravel next to a rock wall. He kept saying, "I should have given it more throttle through there to pull the front around." and "that Ducati likes high corner entry speed."
Yeah right! Everything except "I shouldn't have been going so fast."
We left him beside the road with a dislocated elbow and a twisted motorcycle after calling some friends to pick him up, and went on to enjoy another 200 miles or so. The next year he wadded it up for good at the track (his second track day).
Street pavement has a thin film of engine oil, gear oil, diesel oil, antifreeze and dust. Especially at places like freeway onramps, where it's full throttle for all the cagers. That may have played a role. Who knows...
I drag my knee very rarely on the street if it's an especially tight turn. I try not to make a habit of it. Riding a track keeps me from needing to do that stuff on the street.
Ride safely!
It goes back to the fall of 2002, the first year on my VTR. I had replaed the shock and fork springs and revalved the forks but otherwise stock. I rode about 8000 miles that summer, mostly solo on twisty roads (lucky for me, that's about all there is around here). I was getting pretty comfortable with the 100HP Super Beast between my legs. My friend Bob had been warning me about riding with other people and getting pulled in over my head, so I always had that in mind.
Anyway, this is not really about me. I was with a group of 5. 2 RC51s, an R1 and a Ducati 998. The riders on the '51s and the R1 had quite a bit of track experience and had been riding a long time. Not sure how much experience Dustin had, but that Duc sure was exotic.
So off we went over Monitor Pass. I had ridden it several times, both in previeous years and almost every week that summer. I was leading and riding at a "comfortable pace". We got to the top and Dustin came roaring by. We all let him go. He'd never ridden the road before.
The descent starts out with some sweepers then has a couple hairpins. I saw him coming out of the frist one from above. At the next one he lowsided and was all wadded up in the gravel next to a rock wall. He kept saying, "I should have given it more throttle through there to pull the front around." and "that Ducati likes high corner entry speed."
Yeah right! Everything except "I shouldn't have been going so fast."
We left him beside the road with a dislocated elbow and a twisted motorcycle after calling some friends to pick him up, and went on to enjoy another 200 miles or so. The next year he wadded it up for good at the track (his second track day).
Street pavement has a thin film of engine oil, gear oil, diesel oil, antifreeze and dust. Especially at places like freeway onramps, where it's full throttle for all the cagers. That may have played a role. Who knows...
I drag my knee very rarely on the street if it's an especially tight turn. I try not to make a habit of it. Riding a track keeps me from needing to do that stuff on the street.
Ride safely!
#12
[quote=rc996";p="9144]
I think about it sometimes. Just not when I'm at home. I should really do it because I can't believe somebody wants to pay me for some hacked up mufflers!
:P
Well that is a good point, and you should take advantage of it. Really want to see some pics to see the condition. Hehe!
As far as the rest of this post is concerned...I have no track expertise. I do ride the local twisty canyons
Originally Posted by "Utah996";p="9139
Now get me pics of your stock debaffled superhawk exhaust and your e-mail addy for paypal :evil: :D[/quote
Now get me pics of your stock debaffled superhawk exhaust and your e-mail addy for paypal :evil: :D[/quote
I think about it sometimes. Just not when I'm at home. I should really do it because I can't believe somebody wants to pay me for some hacked up mufflers!
:P
As far as the rest of this post is concerned...I have no track expertise. I do ride the local twisty canyons
#13
Re: Understeer/Front end push problem
Good story and good info.
FWIW - the only time my knee ever touches the ground is when I am riding The Dragon and a few other twisty roads in that area. Around town and on the rural roads I ride near Birmimgham, I'd have to be going WAAYY fast to drag a knee. So, I don't.
It's one thing to do it on mountian roads at 30-50 mph. It's another thing to do it on more "public" roads at 80-100 mph. I do NOT got there!
The roads I ride in the mountains are roads I'm familiar with, have few (or no) side entrances, no traffic lights, no stop signs, etc.
In other words they are pretty good for more aggressive riding.
Attempting the same on more public thoroughfares exposes one to just what you mentioned: oil film, rocks, gravel, someone's trash, etc.
There's a time and a place for such antics. I like to believe keeping that in the back of my mind helps me avoid a major boo-boo.
Brian
FWIW - the only time my knee ever touches the ground is when I am riding The Dragon and a few other twisty roads in that area. Around town and on the rural roads I ride near Birmimgham, I'd have to be going WAAYY fast to drag a knee. So, I don't.
It's one thing to do it on mountian roads at 30-50 mph. It's another thing to do it on more "public" roads at 80-100 mph. I do NOT got there!
The roads I ride in the mountains are roads I'm familiar with, have few (or no) side entrances, no traffic lights, no stop signs, etc.
In other words they are pretty good for more aggressive riding.
Attempting the same on more public thoroughfares exposes one to just what you mentioned: oil film, rocks, gravel, someone's trash, etc.
There's a time and a place for such antics. I like to believe keeping that in the back of my mind helps me avoid a major boo-boo.
Brian
#14
Re: Understeer/Front end push problem
Trackdays, Trackdays, Trackdays, leave the knee draggin for trackdays and the rare mountain roads. If you're into that type of riding go to the track, it is sooo much fun!! There's nothing even close to it, you can go as fast as you feel comfortable and slowly increase your speed as you get more confidence.
The track surface is stickier and most are a lot better maintained then most public roads. But the number one reason is there's nobody but you and a bunch of bikes and your all going in the same direction.
The track surface is stickier and most are a lot better maintained then most public roads. But the number one reason is there's nobody but you and a bunch of bikes and your all going in the same direction.
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01-06-2007 05:19 PM