Rear tire slip - help!

[kawa64]

Going around a long left-hand turn...

Entrance is about 150kph, exit is fully open throttle;- my rear tire keeps slipping and I don't know why.

During races, others manage to make up some time on me here because of this.

Rear also spins when rolling on a gear up.

Dry track very sunny, very hot, tires warmers than Satan's asshole.

I am using Bridgestone R11 tires, they have a small amount of tread but are very sticky, basically soft-medium slicks in heat. (Tire pressure is good, great grip everywhere else.)

I've messed with both suspension damping, I've also messed with wheel weights and adding weights to the left side of the rear wheel.

I am as low to the ground as possible with my elbows digging into the ground and the bike is as straight up as possible around the bend.

Why the hell does the rear keep slipping.

[ellipsis]

...something to do with the throttle and its tenuous link to the brain I'd say...

[dave100]

Are you tailbraking through there, maybe ur front wheel is being pushed down

[kawa64]

Are you tailbraking through there, maybe ur front wheel is being pushed down

Off the front brake before on throttle

[Kickaha]

Going around a long left-hand turn...

Entrance is about 150kph, exit is fully open throttle;- my rear tire keeps slipping and I don't know why.

During races, others manage to make up some time on me here because of this.

Rear also spins when rolling on a gear up.

Dry track very sunny, very hot, tires warmers than Satan's asshole.


What corner on what track?

[buggerit]

What corner on what track?

Top of ton straight, coro:yes:

[Grumph]

Going around a long left-hand turn...

Entrance is about 150kph, exit is fully open throttle;- my rear tire keeps slipping and I don't know why.

During races, others manage to make up some time on me here because of this.

Rear also spins when rolling on a gear up.

Dry track very sunny, very hot, tires warmers than Satan's asshole.

I am using Bridgestone R11 tires, they have a small amount of tread but are very sticky, basically soft-medium slicks in heat. (Tire pressure is good, great grip everywhere else.)

I've messed with both suspension damping, I've also messed with wheel weights and adding weights to the left side of the rear wheel.

I am as low to the ground as possible with my elbows digging into the ground and the bike is as straight up as possible around the bend.

Why the hell does the rear keep slipping.

What do you weigh ? - and what is the bike ?

[kawa64]

What do you weigh ? - and what is the bike ?

I am 75kg, the bike is 185-195kg.

The bike is a 2014 fireblade

Currently running carbon fibre front wheel, alloy rear wheel, Ohlins ttx gp suspension, stock swingarm, stock chasis and frame; but a bit of the rear frame has been cut to improve handling.

[riffer]

Where's all your weight as you accelerate - inside or outside peg?

D'oh - just realised, if you're leaning as far as you can out there's no weight on the outside peg hardly.

Maybe you've actually got too much weight off the bike - perhaps being a bit closer to the bike could help get more weight on the tyre. Or maybe its something more like how hard you're holding on to the handlebars is causing some imbalance in the suspension causing the bike to struggle.

[riffer]

I know bugger all about how those Ohlins rear shocks work through their travel but maybe it's just not working enough at the start of the travel.

[malcy25]

Could be any number of things. I'd check....as a starting point
Too much compression or Spring rate or preload which is not allowing it to ride over bumps,
Too much rebound so not extending off the backside if bumps
Chain Too tight
Swing arm spindle not free
Too much tyre pressure - what gain are you seeing cold to hot?
How old is the tyre
Is there anything odd with your rear geometry
Some one changed the linkage

[Reckless]

Going around a long left-hand turn...During races, others manage to make up some time on me here because of this.


Or maybe its something more like how hard you're holding on to the handlebars is causing some imbalance in the suspension causing the bike to struggle.

Exactly the scenario put to us at Superbike school, grip with the lower body, relax the arms, feed the throttle and let the bike have its way.

I am by far no expert, others may have much better advice but as soon as I read it, it rang a bell to our lesson :)
Great question, Interested to keep following and see what others have to say :)
Make sure you post your outcome :)

[kawa64]

Could be any number of things. I'd check....as a starting point
Too much compression or Spring rate or preload which is not allowing it to ride over bumps,
Too much rebound so not extending off the backside if bumps
Chain Too tight
Swing arm spindle not free
Too much tyre pressure - what gain are you seeing cold to hot?
How old is the tyre
Is there anything odd with your rear geometry
Some one changed the linkage

I have messed around with swingarm malleability, but because of the "low quality," of my stock swingarm, there isn't much to play with.

I don't know much about hot graining or cold tearing, but I always make sure my tire is at a reasonable temperature, the tire pressure seems to be the best grip wise I have evern riden with.

Chain, links is all good.

There aren't any bumps, it's all smooth and no curve on the track surface at that point.

I certainly don't feel there is anything wrong with my rear geometry but I'd have to recheck that from a third person view.

I'll double check with all the info you gave, thanks mate.

[kawa64]

Exactly the scenario put to us at Superbike school, grip with the lower body, relax the arms, feed the throttle and let the bike have its way.

I am by far no expert, others may have much better advice but as soon as I read it, it rang a bell to our lesson :)
Great question, Interested to keep following and see what others have to say :)
Make sure you post your outcome :)

Might have to join one of those. Most useful thing you learned?

[Grumph]

Could be any number of things. I'd check....as a starting point
Too much compression or Spring rate or preload which is not allowing it to ride over bumps,
Too much rebound so not extending off the backside if bumps
Chain Too tight
Swing arm spindle not free
Too much tyre pressure - what gain are you seeing cold to hot?
How old is the tyre
Is there anything odd with your rear geometry
Some one changed the linkage

You seem to think as I do - that it's a setup problem at the rear. I don't like to hear that he's messed around with swingarm "malleability" as errors here can be terminal...

[AllanB]

Reckon you need some ape-hangers so your body is more rearward, thus placing weight over the rear wheel. I'll be here all night if you need more advice.

[OddDuck]

Caveat: little practical experience of my own.

Google 'tyre grip vs temperature' and quite a few interesting discussions pop up, most of them from the car world. General consensus from what I can find is that there's a temperature optimum for max. grip. Go under and your tyres are slippy; go over and it's the same story.

One of the more interesting points was that it's not just temperature. Inflation, grip pattern, carcass flex etc etc all seem to influence each other.

Sorry that I can't be more help than this... would it be worth running some tests?

[ellipsis]

would it be worth running some tests?


...or a poll...

[gsxr]

Youre going into the corner too slow.
Faster entry means less throttle to exit. Problem solved.

[malcy25]

You seem to think as I do - that it's a setup problem at the rear. I don't like to hear that he's messed around with swingarm "malleability" as errors here can be terminal...

Classic example was a local guy here I know low sided hsi SV650 a couple of times and was getting odd wheel spin. We talked it through and I asked about where the bike / shock (an Ohlins) etc had come from. The old owner weighed 120kg plus gear. New Owner, may be 70kg......new spring and I think valving to suit and the problem went away.

Ken McIntosh and I were talking earlier this year as I was in his work shop and he and Pete were telling me a couple of things which get over looked. How much chain slack is the when the countershaft, rear axle and swng arm pivot line up? What happens when there's not enough? Does it stop the rear suspension from compressing beyond that binding point? What effect does that have on other things like traction, swing arm alignment, counter shaft bearings!

From what I can tell, some bikes don't have enough slack as a stock figure....oops!

[malcy25]

I have messed around with swingarm malleability, but because of the "low quality," of my stock swingarm, there isn't much to play with.

I don't know much about hot graining or cold tearing, but I always make sure my tire is at a reasonable temperature, the tire pressure seems to be the best grip wise I have evern riden with.

Chain, links is all good.

There aren't any bumps, it's all smooth and no curve on the track surface at that point.

I certainly don't feel there is anything wrong with my rear geometry but I'd have to recheck that from a third person view.

I'll double check with all the info you gave, thanks mate.

Look beyond just is "okay or good or bad. Look at what is actually happening with it.

Eg chain: It's not just are the links okay. Look to see whether it has enough slack to allow the countershaft, swing arm pivot and rear axle to line up. Take your shock out. Rotate the swing arm so they line up. Does it move freely through this point? Is the chain worn, stretched clean and lubed and free?

Have you done you static sag figures? if not, or you don't know what this is. Go to Jail and do not collect $200! Go find out what it is. That could easily be 100% of your problem.

Bumps: Who cares whether there is or not. The rear suspension needs to compress and move as part of the dynamic that creates traction, irrespective.

Tyres: I'll ask again. What pressure rise are you seeing. Google Dave Moss Tuning.

I think you need to do some serious learning in all of these areas. There's good books around like Sports Bike suspension tuning by Andrew Trevitt. Go start reading so you at least understand what you are dealing with.

Re low quality of the stock swing arm, whatever. It won't matter what the quality is if the rest of the stuff it is attached to is badly set up. My brother and I subscribe to a theory called "magpie" theory. Magpies are attracted to Shiny shit. But it does not matter how good the shiny shit is if it not as well set up as the stock stuff. I can't say I've heard of guys moaning about the stock ones.

Is the frame straight and not cracked.

can you explain how chopping some of the rear of the frame off will make it handle better.

Again, I'll ask the question asked above. Which corner, what circuit and what country. Updating your profile may explain things.

[neil_cb125t]

Going around a long left-hand turn...

Entrance is about 150kph, exit is fully open throttle;- my rear tire keeps slipping and I don't know why.

During races, others manage to make up some time on me here because of this.

Rear also spins when rolling on a gear up.

Dry track very sunny, very hot, tires warmers than Satan's asshole.

I am using Bridgestone R11 tires, they have a small amount of tread but are very sticky, basically soft-medium slicks in heat. (Tire pressure is good, great grip everywhere else.)

I've messed with both suspension damping, I've also messed with wheel weights and adding weights to the left side of the rear wheel.

I am as low to the ground as possible with my elbows digging into the ground and the bike is as straight up as possible around the bend.

Why the hell does the rear keep slipping.

Come along to CSS in Feb at Manfeild - well have it sorted by the end of the first session...........90% of the time its the rider unless your setup is way out. If your setup is way out then it will do it every corner like this, if it ONLY does it at ONE corner.....its normally you :-)

[caspernz]

Come along to CSS in Feb at Manfeild - well have it sorted by the end of the first session...........90% of the time its the rider unless your setup is way out. If your setup is way out then it will do it every corner like this, if it ONLY does it at ONE corner.....its normally you :-)

Judging by the way the OP spelled tyres with an i me thinks it's not a kiwi based rider posting :laugh:

[kawa64]

Judging by the way the OP spelled tyres with an i me thinks it's not a kiwi based rider posting :laugh:

my american/british spelling is all over the place


Come along to CSS in Feb at Manfeild - well have it sorted by the end of the first session...........90% of the time its the rider unless your setup is way out. If your setup is way out then it will do it every corner like this, if it ONLY does it at ONE corner.....its normally you :-)

I will see if I can make it, I do agree that it's something stupid that I'm doing and not the bike