Over steer problem - Yamaha R3 Forum
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post #1 of 12 Old 08-15-2018, 03:10 PM Thread Starter
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Over steer problem

So I changed tires before a track day last weekend and immediately noticed a very difficult under steer. Feels like I’m wrestling the bike to keep it on a line. Bike still turns in quickly but if I’m exiting or even just maintenance throttle I have to be forceful with the handlebars to stay on a line.
The tires: from 150/60 and 110 Dunlop q3 to a140/70 and 110 pirelli sc
What I’ve tried: raising rear ride height, softening front comp and rebound.
Or is this just a coincidence and my bike is broken and everyone else has made this switch without issues.
Advice is appreciated. I’m trying to race it next weekend😬
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post #2 of 12 Old 08-15-2018, 04:03 PM
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So is it understeer or oversteer? In the title of the thread you said oversteer, but in your post you said understeer? Although I've never really heard of bikes having oversteer issues...usually that ends up in high-sides lol

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post #3 of 12 Old 08-15-2018, 05:37 PM Thread Starter
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Sorry.. it is under steer. It felt like I would just fall over if I wasn’t holding a ton of pressure on the bars. Not so much just going wide under throttle application.
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post #4 of 12 Old 08-15-2018, 07:45 PM
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Originally Posted by MarkB View Post
Sorry.. it is under steer. It felt like I would just fall over if I wasnít holding a ton of pressure on the bars. Not so much just going wide under throttle application.

Understeer means the bike is pushing wide on corner exit.


From the change in tires you mentioned you've basically gone to a setup that has a higher rear ride height, therefore steeper rake angle and less trail, because the Pirelli 140/70 tire is a bigger tire in diameter than the 150/60 one. I imagine the fronts are very similar. So if you want the same feeling as before you'd have to either raise the front a bit, or lower the rear if you have an adjustable shock.



I too made a similar change except it was a bit more extreme, since I went from a 120 front and 150 rear to the 110/140 combo. So my front dropped and my rear went up, making a very significant difference in rake and trail. I rode it at first before making any adjustments to see how i'd like it, and as expected it was easier to turn into corners, but in some situations when getting on the gas, I could feel the rear end sliding a bit which I didn't like (basically over-steer I guess), and on top of that the bike was quite a bit twitchy at high speeds, like in 5th-6th gear corners. I raised up the front just a bit, about 3-4 mm, and now it's ok, just how I like it.
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2007 ZZR600 (sold)
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2013 CBR500R (sold)
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post #5 of 12 Old 08-15-2018, 11:36 PM Thread Starter
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Sounds like your bike did the opposite of what mine is doing. Mine isn’t sliding in the rear. Yours basically did what you would expect a bike to do by rising the rear and dropping the front. The problem I am having seems to be inverse of what you would expect. The rear went up slightly and it is still wanting to go wide / not hold a line in the corner. It’s exhausting and I’m in decent shape.
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Last edited by MarkB; 08-15-2018 at 11:44 PM.
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post #6 of 12 Old 08-16-2018, 07:00 AM
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Originally Posted by MarkB View Post
Sounds like your bike did the opposite of what mine is doing. Mine isnít sliding in the rear. Yours basically did what you would expect a bike to do by rising the rear and dropping the front. The problem I am having seems to be inverse of what you would expect. The rear went up slightly and it is still wanting to go wide / not hold a line in the corner. Itís exhausting and Iím in decent shape.

Well then I don't know what to tell you lol...maybe you're pulling on the handle bars instead of pushing, and basically "fighting the bike" against what it wants to do.
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2007 ZZR600 (sold)
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2013 CBR500R (sold)
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post #7 of 12 Old 08-17-2018, 02:42 AM
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Originally Posted by MarkB View Post
Feels like Iím wrestling the bike to keep it on a line. Bike still turns in quickly but if Iím exiting or even just maintenance throttle I have to be forceful with the handlebars to stay on a line.
Quote:
Originally Posted by MarkB View Post
Sorry.. it is under steer. It felt like I would just fall over if I wasnít holding a ton of pressure on the bars. Not so much just going wide under throttle application.
So both of these statements you've made are conflicting. If you're exiting a turn you should be on the gas but you mention it doesnt go wide under throttle? You then mention it feels like its falling over? which direction? Like towards the inside or the outside?

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post #8 of 12 Old 08-17-2018, 07:10 AM Thread Starter
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Sorry it is hard to describe. Bike turns in with trail breaking just fine. Once off the breaks and transitioning to throttle, for maintenance throttle or roll on, the handlebars are pulling towards the outside of the corner. Before and on my other bikes handlebar input during this part of the corner is very little. I’ve never heard of anything like it which is why I’m posting. I’d have someone else ride it to try and figure it out but that won’t help me for my race this weekend.
I bought a new set of q3s so hopefully I don’t have to deal with it for this round.

Last edited by MarkB; 08-17-2018 at 07:16 AM.
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post #9 of 12 Old 08-17-2018, 09:48 AM
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Terms can be challenging when down loading a rider. Understeer could mean turning tighter than what you believe your input should cause or it could mean that it runs wider than you believe it should for the amount of input

What I've found is that rider to expert communications require terms clearing before the download begins.

In addition to the rider feed back you need a stable way to communicate/record chassis settings. This would be more important when the expert is not in control of the machine.

I hope this doesn't come off as rude. I just want to help.

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post #10 of 12 Old 08-17-2018, 06:44 PM
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Quote:
Originally Posted by MarkB View Post
Sorry it is hard to describe. Bike turns in with trail breaking just fine. Once off the breaks and transitioning to throttle, for maintenance throttle or roll on, the handlebars are pulling towards the outside of the corner. Before and on my other bikes handlebar input during this part of the corner is very little. Iíve never heard of anything like it which is why Iím posting. Iíd have someone else ride it to try and figure it out but that wonít help me for my race this weekend.
I bought a new set of q3s so hopefully I donít have to deal with it for this round.
That sounds like you're tucking the front. Are you absolutely positive you're no longer on the brakes? Is the bike a salvage that you race prepped? When was the last time your forks have been went through? This sounds more than a tire problem.

I run the 110/140 Pirelli Supercorsas and i've ridden the bike @ OEM ride height with ohlins suspension f/r which i recently switched up by raising the front and raising the rear as far as she would go (similar to the graves suspension setup) and I havent noticed anything close to what you're describing.

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