Jump to content

Front End Adjustments


Recommended Posts

Had my 1199 out at COTA a few weeks ago and found that as I got faster, my front end started bottoming out. We tried adding a little preload and rebound with the same results. Bike has been set up to my weight, revalved, resprung, etc. Thoughts? Would you think more suspension tuning or does this have something to do with how I am braking (technique)?

Link to comment
Share on other sites

If it really bottoms you will hear a loud sound when it does. The solution is adding more oil in the forks. You can start by measuring how much oil do you need to add 10mm of height, so you will not take apart of the fork every time you want to add or remove oil.Then try it with 10mm more oil and see how it goes.

Link to comment
Share on other sites

Do you know where/when it was bottoming out? Did you feel it bottom out under braking? Are there any track day photos you can look at?

 

Where are you in your compression settings in the front? Somewhere in the middle or already as stiff as possible?

 

It was happening at the end of the back straight coming down from 160-170 mph for turn12. I'm pretty certain I actually felt it a time or two. I have a zip tie around the tube and it kept getting pushed all the way down. On any other track, I've never had it do that. As far as the settings go, if I recall correctly, we tightened it all the way down and then backed it out from 8 clicks to I believe 12 clicks. I may be off a few. I would say somewhere in the middle if I had to guess. I am running an Ohlins fork with a 30mm cartridge.

Link to comment
Share on other sites

 

Do you know where/when it was bottoming out? Did you feel it bottom out under braking? Are there any track day photos you can look at?

 

Where are you in your compression settings in the front? Somewhere in the middle or already as stiff as possible?

 

It was happening at the end of the back straight coming down from 160-170 mph for turn12. I'm pretty certain I actually felt it a time or two. I have a zip tie around the tube and it kept getting pushed all the way down. On any other track, I've never had it do that. As far as the settings go, if I recall correctly, we tightened it all the way down and then backed it out from 8 clicks to I believe 12 clicks. I may be off a few. I would say somewhere in the middle if I had to guess. I am running an Ohlins fork with a 30mm cartridge.

 

 

OK this helps, thanks for the info.

 

When you are braking, are you low on the bike with your forearms parallel to the ground? Are you able to keep most of your weight off the bars? When braking really hard on a high HP bike like that, it is very difficult to keep ALL the pressure off the bars, but do the best you can. If you sit upright with stiff arms (I know you aren't doing that at 160 mph, I'm just making a point here) and allow your upper body weight to come down on the bars, you add a lot of extra load on the front suspension. So, anything you can do to minimize pressure on the bars helps - good lock-on with lower body, grip hard with knees, use your core muscles to support your upper body, keep your forearms parallel to the ground, and for sure add StompGrip if you don't have it. It also may help slightly to get as far back in the seat as you can in your tuck.

 

What is your braking technique? Describe as best you can how you come on the brakes and how you come off them - do you brake progressively harder and harder all the way to the turn point, or do you come on the brakes really hard then taper off, do you carry the brakes past the turn point to the apex, etc.

 

Is there a bump, a downhill section, or any other track issue at the point you think you are bottoming out? Example at Auto Club Speedway there is a bump at the bottom of a downhill section at the end of a braking zone. You either have to set your suspension crazy stiff to handle that ONE spot on the track, or you manage it with technique by getting off the brakes and (in that particular case) back on the gas right before the bump to unload the front end and handle it that way. In other words, if the bike feels good everywhere else, you might be better off to manage it by braking more gradually in that spot, or letting off the brakes a bit, or moving your braking zone so you are not hard on the brakes at that point, instead of changing around your suspension.

 

You mentioned it started happening as you got faster... how much faster, and over how long a period? If you got your bike set up a few years ago and were riding in C group and now you are in A group, for example, it is not only reasonable but LIKELY that you need to update your spring rates and valving to match your new pace. A good local suspension guru can usually take your weight, laptime at the local track, and a brief description of your riding style (do you trail brake heavily, are you gentle with the controls or more abrupt, etc.) and make recommendations for spring rate and valving.

 

I assumed from your description of what has been done to the forks that they have been recently serviced... but if not, that would be step one. It's been recommended to me to service the suspension at least once a year, when racing; if I am putting more than about 6 big-track fast-pace weekends on a bike in a season, I service the suspension in the off season. Less than that on any one bike and I might skip it for that bike that year.

Link to comment
Share on other sites

​Awesome. Thanks for all the thought in this replay. My responses are below.

 

OK this helps, thanks for the info.

When you are braking, are you low on the bike with your forearms parallel to the ground? Are you able to keep most of your weight off the bars? When braking really hard on a high HP bike like that, it is very difficult to keep ALL the pressure off the bars, but do the best you can. If you sit upright with stiff arms (I know you aren't doing that at 160 mph, I'm just making a point here) and allow your upper body weight to come down on the bars, you add a lot of extra load on the front suspension. So, anything you can do to minimize pressure on the bars helps - good lock-on with lower body, grip hard with knees, use your core muscles to support your upper body, keep your forearms parallel to the ground, and for sure add StompGrip if you don't have it. It also may help slightly to get as far back in the seat as you can in your tuck.

I try to keep my weight off the bars, but I know there is room for improvement, coming down from those speeds definitely tenses me up. It was my first time at that track. I felt a little uncomfortable most of the weekend. Soo many turns to learn so I'm sure my stress was higher than normal.

What is your braking technique? Describe as best you can how you come on the brakes and how you come off them - do you brake progressively harder and harder all the way to the turn point, or do you come on the brakes really hard then taper off, do you carry the brakes past the turn point to the apex, etc.

I tend to get the majority of my braking done earlier and try to taper off. In this turn I was frequently still coming off after tipping it in. I would say that in this turn I did find that I over braked occasionally at the start of the braking zone (more abrupt pull of the lever). This was probably part of the OMFG, I am flying and I need to slow down :) This may have led to excessive compression of the suspension.

Is there a bump, a downhill section, or any other track issue at the point you think you are bottoming out? Example at Auto Club Speedway there is a bump at the bottom of a downhill section at the end of a braking zone. You either have to set your suspension crazy stiff to handle that ONE spot on the track, or you manage it with technique by getting off the brakes and (in that particular case) back on the gas right before the bump to unload the front end and handle it that way. In other words, if the bike feels good everywhere else, you might be better off to manage it by braking more gradually in that spot, or letting off the brakes a bit, or moving your braking zone so you are not hard on the brakes at that point, instead of changing around your suspension.

As I read this I started wondering if maybe I am blaming the wrong corner. Turn 11 is at the bottom of a short hill and carrying a decent amount of speed into it. No bumps or anything in 11 or 12.

You mentioned it started happening as you got faster... how much faster, and over how long a period? If you got your bike set up a few years ago and were riding in C group and now you are in A group, for example, it is not only reasonable but LIKELY that you need to update your spring rates and valving to match your new pace. A good local suspension guru can usually take your weight, laptime at the local track, and a brief description of your riding style (do you trail brake heavily, are you gentle with the controls or more abrupt, etc.) and make recommendations for spring rate and valving.

Suspension was set up last season. When I said I got faster, I meant from day 1 to day 2 at COTA. Maybe somewhere between 5-7 seconds faster. The suspension guy that is usually at COTA for these days was not there. I would have loved to have him check things out for me. As above, I would say I tend to be a little more abrupt on application of brakes but trail off into many turns.

I assumed from your description of what has been done to the forks that they have been recently serviced... but if not, that would be step one. It's been recommended to me to service the suspension at least once a year, when racing; if I am putting more than about 6 big-track fast-pace weekends on a bike in a season, I service the suspension in the off season. Less than that on any one bike and I might skip it for that bike that year.

Last year was a light year at the track, but still wouldn't hurt to have someone that knows what they are doing help me make any potential changes.

Thanks again!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...