Rear kept stepping out today :/

[MirinNinja]

So I almost highsided on my 300 today on corner exit. I wasn't particularly hamfisted with the throttle (although it was the first session since installing the R6 throttle tube) but throughout the whole day I was getting slip on that corner. Is it time to change tyres or something wrong with my pressures?

Currently running SC2 at the front and a Bridgestone S20 at the rear. Pressures are 27PSI front and 28 rear (hot on the warmers). I wasn't setting a blistering pace or anything today either (running about .5 seconds behind PB which is still slooooooow) so I'm a little puzzled as to why the rear kept slipping on this little bike.

Perhaps time to change to a Rosso II rear?

[sharky nrk]

low pressure getting the tire hot and greasy? I tend to run around 28/26 cold on 003PRO/003RS setup

[sharky nrk]

I would say you probably should have been closer to 30/28 to 32/30 psi cold. Street tires are not nearly as tolerant to low pressure heat build up as track tires and will indeed get greasy.

[MirinNinja]

Originally Posted by sharky nrk

I would say you probably should have been closer to 30/28 to 32/30 psi cold. Street tires are not nearly as tolerant to low pressure heat build up as track tires and will indeed get greasy.

28-30 cold would translate to around 31-34 hot correct?

Also are you saying that my front is too low too? I'm running the supercorsa SC2s which is a race tyre.

How do you like the 003RS for the rear? Do they last long? I'm due for a new rear soon anyways so I'm debating between the Rosso IIs vs something else.

[sharky nrk]

Originally Posted by MirinNinja

28-30 cold would translate to around 31-34 hot correct?

Also are you saying that my front is too low too? I'm running the supercorsa SC2s which is a race tyre.

How do you like the 003RS for the rear? Do they last long? I'm due for a new rear soon anyways so I'm debating between the Rosso IIs vs something else.

Should be close on the translation from cold to hot if ideal. Generally you could see about a 4 or 5 psi pressure gain from cold to proper operating temp. I would imagine it would be low even for the front race tire, but someone who runs that particular tire can chime in and let me know. My brother runs an SC1 up front and RII rear but I can't remember what pressure he ran hot. I think it was up around 34 hot front but can check. I really like the 003RS rear personally, and the 003Pro up front. But don't have comparisons on the Ninjette on anything else really other then RS/RS combo which was a little dicey on the front. And the IRCs once ...... which really sucked everywhere lol

I feel you are probably low pressure all the way around for off the warmers hot pressures, whether or not it getting greasy was the rear slide would be speculation though. Those pressure settings are closer to what I would expect cold. Especially for a street tire.

[MirinNinja]

Originally Posted by sharky nrk

I would imagine it would be low even for the front, but someone who runs that particular tire can chime in and let me know. My brother runs an SC1 up front and RII rear but I can't remember what pressure he ran hot. I think it was up around 34 hot but can check. I really like the 003RS rear personally, and the 003Pro up front. But don't have comparisons on the Ninjette on anything else really other then RS/RS combo which was a little dicey on the front.

I do know that on that S20 I feel you are probably low on the rear, whether or not it getting greasy was the rear slide would be speculation though.

Sweet cheers for the info! Also are you running the 003RS in 140 or 150?

[sharky nrk]

140 in the back. No prob and best of luck.

[csmith12]

One question and 2 comments.

Are you a lightweight rider?

I got $10 that says you were tight on the bars.
Did you have your suspension setup?

[MirinNinja]

Originally Posted by csmith12

One question and 2 comments.

Are you a lightweight rider?

I got $10 that says you were tight on the bars.
Did you have your suspension setup?

I weigh about 170lbs with all my track gear.

And suspension is stock sadly. Preload on max.

As for tight on the bars I honestly can't recall when I almost highsided but in general I would say I'm not tight as I've been actively remembering to drop my inside elbow and let it hang as much as possible.

[Motofool]

Originally Posted by MirinNinja

I weigh about 170lbs with all my track gear.

And suspension is stock sadly. Preload on max.

If you feel like a quick succession of lateral slides when turning and rolling over less than perfect pavement, your rear tire may be in the air for too long.

This happens when the spring+tire hardness (excessive spring preload+air pressure) overwhelms the absorber.

You cannot adjust the absorber (sealed oil+gas), but you could try reducing the spring pre-load and playing with tire pressure.

Higher than optimum pressure in cold conditions, induces a more rigid carcass and lower temperature of the rubber.

Lower than optimum pressure in cold conditions, induces a more flexible carcass, higher temperature of the rubber and sometimes even higher pressure in hot conditions than the one reached with higher than optimum pressure in cold conditions.

Don't look for a hard number for optimum pressure in cold conditions: there is a unique number for the particular combination of your weight+bike weight, the suspension set up and the specific type of pavement and experimentation is the only way to fine tune it.

Then, you also deal with the inaccuracy of the pressure gauges:
https://www.ninjette.org/forums/showthread.php?t=193885

[csmith12]

Originally Posted by MirinNinja

I weigh about 170lbs with all my track gear.

And suspension is stock sadly. Preload on max.

As for tight on the bars I honestly can't recall when I almost highsided but in general I would say I'm not tight as I've been actively remembering to drop my inside elbow and let it hang as much as possible.

170 hmmm... depending on how you ride, could go either way to bump it down one or leave it. Lemme ask you this, did it happen every lap every time?

[MirinNinja]

Originally Posted by csmith12

170 hmmm... depending on how you ride, could go either way to bump it down one or leave it. Lemme ask you this, did it happen every lap every time?

I backed off my roll-on aggressiveness but if I was too aggressive, I could definitely feel slip. It's just that one corner.

The thing is I remember being just as aggressive (sometimes more so) last track day and this didn't happen. Same tyre, same pressures. Yesterday was a warmer day though.

[cuong-nutz]

Lower the preload first and see how it feels. Then after that increase the rear tire pressure. How's the wear look for your rear tire?

[MirinNinja]

Originally Posted by cuong-nutz

Lower the preload first and see how it feels. Then after that increase the rear tire pressure. How's the wear look for your rear tire?

Ok I'll take a notch off the preload. The wear looks fine. Don't have a photo for you but no balling or tearing of the tyre. Just the usual wear that you would expect from a track day.

[csmith12]

Seems to me that if the suspension was out of sorts then it would be noticeable in other corners as well, not just skipping in one. There should be other clues if this was the case. imho, something else is going on.

[Aufitt]

Which track and corner?

[cuong-nutz]

Perhaps this particular turn is different than the others to where it exaggerates the less than ideal setup of the suspension and tire pressure?

Things I can think of for the rear to step out:

loose debris (off race line)
lean angle > throttle
rear suspension is fully extended on a downhill turn from hard braking
high tire pressure (not enough carcass flex)
low tire pressure (too much carcass flex)

[MirinNinja]

Originally Posted by Aufitt

Which track and corner?

Broadford turn 1

Originally Posted by cuong-nutz

Perhaps this particular turn is different than the others to where it exaggerates the less than ideal setup of the suspension and tire pressure?

Things I can think of for the rear to step out:

loose debris (off race line)
lean angle > throttle
rear suspension is fully extended on a downhill turn from hard braking
high tire pressure (not enough carcass flex)
low tire pressure (too much carcass flex)

It's my favorite turn and it leads onto the back straight so I do love getting a really drive out of it so maybe that's why it's happening only in that particular corner.

I will try higher pressures and lower preload. If that doesn't work I'll get some new rubber.

The corner itself is a long right hander which is uphill and on camber.

[Ducati999]

Just a thought, How tight is your chain? Any chance it tightened up since last time you rode this track. Slightly softer rear compression, little slack in the chain and proper tire pressure (available on MFG web page) should have you hooking up in no time!

[cbinker]

it may seem crazy, but on the rear i run about 40 psi on really hot days. That is when i was running Metzlar M5, and did 14 track days that summer.

[csmith12]

Originally Posted by MirinNinja

The corner itself is a long right hander which is uphill and on camber.

Interesting, I just checked out the track map and some vids. Lemme ask you this. Do you feel you make a steering corrections midcorner or about that same time as the rear steps out? What I am ultimately getting at is... how is your line/turn in point vs. others?

Normally, you can just rail the crap outta on camber turns.

[MirinNinja]

Originally Posted by csmith12

Interesting, I just checked out the track map and some vids. Lemme ask you this. Do you feel you make a steering corrections midcorner or about that same time as the rear steps out? What I am ultimately getting at is... how is your line/turn in point vs. others?

Normally, you can just rail the crap outta on camber turns.

I can't tell you for sure as it all happened so fast (cliche!) but I don't think I was making any steering corrections as this was at or just after the apex so I wouldn't have needed to adjust my line or anything.

I'm going to go with my pressures being too low. Gonna try 30PSI hot off the warmers at the rear and see how it goes.

Just out of interest, what pressure (hot) do you run on your front?

[csmith12]

Originally Posted by MirinNinja

Just out of interest, what pressure (hot) do you run on your front?

31 hot but I have the SC1.

[Braden07]

I have rosso II tires and i love them. strict track use, race-prepped 250.. race tec .8 front springs.. stock rear up to 5. (had to because she was walking on me since my trail was changed with it being taller in the front)