Jump to content
BikeSpeedman

IIRC, We Use Throttle To Take Weight Off Smaller Front Tire Right?

Recommended Posts

I think I read that in TotW and/or from Level 1 training. Aim for a weight distribution of 60/40 Rear/Front bc our rear tire has more rubber on the road.

Something got me thinking about that today and I'm now having trouble making sense of it. I think I've heard about people using setup to get *more* not less weight on the front to improve turning. I thought the logic there was that more weight on the front tire generates more heat and also gets a bigger contact patch. Why would we use throttle to reduce both of those things on the smaller front tire? It seems to me like doing so would simultaneously increase the risk of a high side as well as a low side.

There's probably a lot of nuance and subtlety there but I'd rather ask for clarification than assume I figured it out on my own and then risk doing something inadvisable on an indirect route to the hospital.

 

  • Like 2

Share this post


Link to post
Share on other sites

The logic in getting more weight on the front, as I understand it, is that more pressure/weight on the front tire will increase friction (friction increases with weight) and also flatten the tire out more, making the contact patch larger, which doesn't increase friction directly (friction is not dependent on area, just weight) but CAN help the tire because too much pressure in too small an area can (I think) overheat the rubber and reduce the coefficient of friction, which WOULD reduce the overall grip. (Note - this is me giving you my own understanding, this is not superbike-school endorsed info.)

Getting more weight on the front also can tighten up your steering by compressing the forks - but you can also get a similar effect with hook steering or changing your geometry or suspension settings.

So that all works well for turn ENTRY, however once have turned the bike and have reached your desired lean angle and are pointed in the direction you want to go, if you don't get on the gas you will just keep slowing down. The best scenario for traction once you DO roll on the gas is: 40/60 weight distribution. Thus, the throttle control rule, "Once the throttle is cracked on..."

So, the way I look at it, is while you are still slowing down and getting the bike turned, the weight on the front is a good thing (to a point - obviously using too much trail braking while turning can exceed your front tire traction), and once you are back on the gas, 40/60 is the way to go for best stability (we are no longer making lean angle changes at that point) and traction. Does that make sense?

Do you remember from level 1 exactly WHEN you are supposed to START rolling on the gas?

  • Like 3

Share this post


Link to post
Share on other sites

Somewhere in motorcycle setup history, some genius discovered the benefit of using tires with dissimilar profiles. Probably this same genius realized that the caster effect of the front wheel begins to work for the rider when he relaxes on the bars and allows the pro-steering to happen and caster then tracks the desired line while he simply communicated to the machine that the desired line had been established.

There's a certain training program espousing to riders techniques that maximize front tire traction. And while they work, it disregards any consideration of the fact that the rear tire can break traction.

The 60/40 idea is about each tire taking on it's fair share of load in any given cornering situation.

Now I'm going to sit back and munch on popcorn, because I tried very hard to add value without stealing Hotfoot's thunder - because I am doing my mind-reading thing now and know where she's going (smile) in her response. So listen to and interact with her and I'll shut up now.

  • Like 1

Share this post


Link to post
Share on other sites
20 hours ago, Hotfoot said:

Do you remember from level 1 exactly WHEN you are supposed to START rolling on the gas?

"As soon as you can."

Thanks for your reply. Yes, it makes sense. My brain is sorted out again. :)

Share this post


Link to post
Share on other sites
On 5/25/2017 at 5:35 PM, BikeSpeedman said:

I think I've heard about people using setup to get *more* not less weight on the front to improve turning. I thought the logic there was that more weight on the front tire generates more heat and also gets a bigger contact patch. Why would we use throttle to reduce both of those things on the smaller front tire?

The problem is that we are comparing things that are very different in nature: Steering geometry modification and throttle control.

Steering geometry modification: Motorcycle steering has some built-in dynamic stability, just like the front wheels of a shopping cart.

The front wheel steers around an axis that is always ahead of its point of contact with the pavement (distance that is named trail), which naturally straightens the steering up to follow a straight line, especially when the tire is disturbed by a road bump.

Bigger trail makes the bike harder to deviate from a straight line, especially at high speeds, and vice-versa.

Riders who prefer a lighter-quicker steering modify the geometry of the suspension in order to reduce that trail distance, while sacrificing some natural stability.

When doing so by reducing the caster or rake angle in a few degrees, there is slight re-distribution of the weight over the tires, which is very small (about 5% of the total weight moves towards the front suspension for a reduction of rake angle of 3 degrees).

Throttle control: By opening your throttle more or less, you have the dynamic ability of loading the front suspension and the smaller front contact patch with any weight magnitude between 0% and 50% of the total weight of the bike and rider, which makes a big difference respect to the fixed weight transfer discussed above (5%).

Even more, by accelerating and braking hard you are simultaneously modifying the pitch attitude of the frame and that rake angle, and consequently making the steering heavier (accelerating: tail down-nose up) or lighter (barking: nose down-tail up).

When you are turning at a fast rate and with a lot of lean angle, what of the two following extreme situations will keep your tires farther from a possible slide and crash: on the front brake or on the gas? And why?

Chapter #3 explains the link between throttle control, suspension and traction.

The rules of throttle control not only put the proper percentage of weight on the front tire, but put the front suspension to work in the more beneficial range and keep the pitch and height of the chassis as it should for stability and ground clearance.

MotorbikeGeometry.PNG

  • Like 1

Share this post


Link to post
Share on other sites
On 5/26/2017 at 1:14 PM, BikeSpeedman said:

"As soon as you can."

Thanks for your reply. Yes, it makes sense. My brain is sorted out again. :)

You should start rolling in the throttle after you have completed your steering action (reached your desired lean angle) AND the bike is pointed in the direction you want to go. 

Can you roll on TOO soon? If you did, what would happen to your line? 

Share this post


Link to post
Share on other sites
On 5/27/2017 at 3:48 PM, Hotfoot said:

You should start rolling in the throttle after you have completed your steering action (reached your desired lean angle) AND the bike is pointed in the direction you want to go. 

Can you roll on TOO soon? If you did, what would happen to your line? 

I wasn't being a wiseguy btw. I thought Keith literally said "as soon as you can." I remember feeling like he could elaborate a little more but maybe I missed the detail. It was a busy day. :)

If you roll on too soon, you run wide. So if I understand you correctly, by waiting until the right moment, the front tire isn't too busy to deal with the weight transfer.

 

Share this post


Link to post
Share on other sites
On 5/26/2017 at 11:23 AM, Jaybird180 said:

Somewhere in motorcycle setup history, some genius discovered the benefit of using tires with dissimilar profiles circumferences. Probably this same genius realized that the caster effect of the front wheel begins to work for the rider when he relaxes on the bars and allows the pro-steering to happen and caster then tracks the desired line while he simply communicated to the machine that the desired line had been established.

There's a certain training program espousing to riders techniques that maximize front tire traction. And while they work, it disregards any consideration of the fact that the rear tire can break traction.

The 60/40 idea is about each tire taking on it's fair share of load in any given cornering situation.

Made a correction.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×