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topazsparrow

Twitchy front end?

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topazsparrow

Head bearings are all good.

 

Running Renthal Ultra-lows and Bitubo Carts up front, other than that nothing else is different from stock up front.

 

Even when the bike was stock I still found it to be a little bit twitchy over 70mph. If I swerve left and right at any decent speed, the handlebars have a reverberation to them - it's not a full on death wobble or tank slapper but it feels like it's close to getting into it, it just never fully does. If I push the bars one way, it wants to correct back the other way before steadying to where the pressure finds a middle ground. It's kind of hard to explain, but it's a bit like if you don't have enough rebound dampening and you get a few extra mini bounces out of a shock after the first bump.

 

Is there anything that can be done to reduce the head shake or sensitivity? I'm not keen on a stabilizer as I don't think that will do much for the twitchyness, only prevent tank slappers usually.

Does front end rake due to suspension /fork height have a role?

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Zephyr

Probably not the culprit, but I'm curious if you have removed the rubber washers that come stock under the handlebars?  Or perhaps they are still installed and are compressing enough to rebound a touch under quick firm steering inputs?

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Evill_Ed

Have you checked your front and rear wheel alignment? 

Have you adjusted your rear shock to set sag? You could be transferring more weight to the rear of the bike making the front end lighter.  You want the weight biased towards the front.

 

Ed

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shinyribs
10 hours ago, topazsparrow said:

 

Does front end rake due to suspension /fork height have a role?

It definitely can. Lowering the front or raising the rear will steepen the rake and can cause a bike to be more twitchy than before. A shorter front tire, especially one with a steep profile, can do the same thing. 

 

These bike have pretty steep fork rake numbers (24 degrees) even by sport bike standards. And the 90mm trail number is also on the fast-steering side of things. With the steep rake and short trail numbers ( the 09 is 25 degrees and 103 trail with  and extra 1.5" of wheelbase) I'm pleasantly surprised with how much straight line stability the 07's have. But a nimble chassis comes at a bit of a price. You have to be gentle with steering inputs at speed or the bike can start to shake it's head to let you know it doesn't like it.

Or in other words, the fast-turning geometry of these front ends will want to snap the bars back to straight ahead, and a slight oscillation after it self-corrects is kinda to be expected. I don't think the 07 is a twitchy steering bike, but I've been less than smooth with steering inputs a few times and had the bike quiver the bars in protest. 😁 I also wear out the sides of my front tires before the centers, which always results in a triangular ( steep) tire profile. When my tires get worn to that point steering always gets a bit more twitchy, so maybe have a look at that if what you are feeling is a new sensation. Depending on your mileage you may also want to check for worn wheel bearings. 

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Beemer

It happens to me sometimes also and I just push through it. It's no big deal.


Beemer

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topazsparrow
9 hours ago, shinyribs said:

It definitely can. Lowering the front or raising the rear will steepen the rake and can cause a bike to be more twitchy than before. A shorter front tire, especially one with a steep profile, can do the same thing. 

 

These bike have pretty steep fork rake numbers (24 degrees) even by sport bike standards. And the 90mm trail number is also on the fast-steering side of things. With the steep rake and short trail numbers ( the 09 is 25 degrees and 103 trail with  and extra 1.5" of wheelbase) I'm pleasantly surprised with how much straight line stability the 07's have. But a nimble chassis comes at a bit of a price. You have to be gentle with steering inputs at speed or the bike can start to shake it's head to let you know it doesn't like it.

Or in other words, the fast-turning geometry of these front ends will want to snap the bars back to straight ahead, and a slight oscillation after it self-corrects is kinda to be expected. I don't think the 07 is a twitchy steering bike, but I've been less than smooth with steering inputs a few times and had the bike quiver the bars in protest. 😁 I also wear out the sides of my front tires before the centers, which always results in a triangular ( steep) tire profile. When my tires get worn to that point steering always gets a bit more twitchy, so maybe have a look at that if what you are feeling is a new sensation. Depending on your mileage you may also want to check for worn wheel bearings. 

Makes sense. Solid reply.

 

New tires upgraded to Pilot Power 3's at the end of last season, they do have a much narrower profile for easier tip in, so that all makes a lot more sense now.

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shinyribs

I put on a front Pilot Power 3 on the recommendation of a forum member ( different forum) and absolutely love it.  I'm currently at about 8k miles on that tire and it's still going! That's exactly twice as many miles as ever before! And the grip is insane for such a long lasting tire. I've never pushed it in the rain, but I'm 100% confident in that front tire at all times. I love it.

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