Under acceleration your rear suspension compresses. Thus giving you traction to the rear wheel.

 

In Keith Codes Twist of the wrist II he says that it extends. If you put your front tire against a wall and give the bike power the rear end will extend. Why is this?

This is not the same thing as your title says.... if you put your front tire against the wall then your bike can't go anywhere...but your rear tire will move FORWARD a little which in turn will extend your rear suspension.

 

With the front end against a wall, of course it will extend because the bike has nowhere to go.

While riding, the rear will compress during acceleration.

 

Under acceleration your rear suspension compresses. Thus giving you traction to the rear wheel.

I think your wrong bro, ever watch a bike under accelleration, the rear end lifts up, but when you stop accellerating the bike will compress alittle while it stablizes. Just my .02 cents....

 

I think your wrong bro, ever watch a bike under accelleration, the rear end lifts up, but when you stop accellerating the bike will compress alittle while it stablizes. Just my .02 cents....

Well then... hey, if I'm wrong it won't be the first time and certainly won't be the last.

 

I think It's the opposite kevap

It makes the rear want to rise. Ever watch a Tractor Trailer take off ? The rear of the Tractor keeps rising while on the throttle.

I had this on my quad and it worked

http://www.jlatvproducts.com/catalog/index.htm


http://www.amp-research.com/media/index.asp?cat=6

 

When I was a kid we fitted my 70 Chevel with traction bars to help keep the rear end pushing down on the axel.

 

i cant even believe this conversation is taking place!! it compresses! ENOUGH SAID! end this idiotic thread!

 

just so you know you put the traction bars yes to keep the wheel on the ground and prevent wheel hop. that is a whole different design than a bike my friend. as a matter of fact you didnt put traction bars on it you would have to have put ladder bars on it as there are coil springs on a 70 chevelle... not leaf springs as on most cars of the era.

 

i cant even believe this conversation is taking place!! it compresses! ENOUGH SAID! end this idiotic thread!

dewd.....your are 100 percent wrong.the angles between front and rear sprockets and the swingarm pivot form a triangle.when throttle is applied the chain(wich pulls from the top of the rear sprocket) tries to pull the rear wheel forward,which it can't,as it tries to do this the only thing it can do is to pivot.seeing as the rear axle is lower than the front,it tries to pivot underneath the bike,which raises the rear upon acceleration.when that happens tha front raises more than the rear...this is what you feel and it is also what makes you think the rear compresses....but it doesn't.

 

The rear of the bike rises under acceleration. It was written in an article, don't ask for the magazine don't remember. Anyway, they installed linear potentiometers on a GSXR 1100 on the front and rear suspension. Guy goes around the track, come to find out that the suspension does rise on acceleration. The surprising thing was that when the bike was wheeling exiting a turn the rear suspension was still rising. That was unexpected.

 

dewd.....your are 100 percent wrong.the angles between front and rear sprockets and the swingarm pivot form a triangle.when throttle is applied the chain(wich pulls from the top of the rear sprocket) tries to pull the rear wheel forward,which it can't,as it tries to do this the only thing it can do is to pivot.seeing as the rear axle is lower than the front,it tries to pivot underneath the bike,which raises the rear upon acceleration.when that happens tha front raises more than the rear...this is what you feel and it is also what makes you think the rear compresses....but it doesn't.

This certainly makes sense to me. Thansks for the explaination.

 

i cant even believe this conversation is taking place!! it compresses! ENOUGH SAID! end this idiotic thread!

Wow!! I guess it would be an idiotic thread I started and a idiotic book that Keith Code wrote. I'm just trying to figure out how it does this because he doesn't explain what causes this. I'd sure like to learn why, wouldn't you?

 

i cant even believe this conversation is taking place!! it compresses! ENOUGH SAID! end this idiotic thread!

Sorry to tell you but the rear suspension extends under hard exceleration. Chain force causes the rear suspension to extent, in some cases even top out, thats why some bikes have a adjustable swingarm pivit among other reasons. Even when you change your rear sprocket, that changes the chain angle which changes lift force on the rear suspension. It's a pretty long explenation but the rear does lift under hard exceleration.

 

Depending on the acceleration, the rider position, speed, and basically everything else, it could either compress or extend.

At higher speeds where wind resistance is pushing on the front of the bike, like that wall, the spring will extend because the rear wheel, being the drive wheel, is pushing the entire bike, trying to "get ahead of the front".

But this depends on the front forks too....If they rebound too much under heavy acceleration, lift too much, the weight will be transfered differently. This is more hindered at higher speeds due to the aerodynamics of the bike, it tries to keep the front down, to bite in, so the rear can push against it, making the bike go faster.

So long story short if your rear is compressing, which it does alot, you are wasting energy and power, and compromising the suspension more. If you are on a track at high speeds, with less power than 150hp, your rear will not bog down, but lift. Mabey this is why people lower their front for racing. Mabey I'm just talking out of my ass.

 

just so you know you put the traction bars yes to keep the wheel on the ground and prevent wheel hop. that is a whole different design than a bike my friend. as a matter of fact you didnt put traction bars on it you would have to have put ladder bars on it as there are coil springs on a 70 chevelle... not leaf springs as on most cars of the era.

Easy killer. and yes your correct about the ladder bars its been a while, and I know the bike is different just was adding info. :riding

 

You want your suspension to extend under acceleration. Think of this way, if the rear squats it's picking up the rear wheel. If the rear rises, it's pushing down on the rear wheel.

 

another thing is to watch a shft driven motorcycle.when throttle is given,as in a v-max example,the rear lifts noticably from the pinion acting upon the ring gear.

 

It does extend when the bike has no where to go. I do this all the time at stop lights. just hold your front brake and give the bike some gas. the rear with lift up.

 

You want your suspension to extend under acceleration. Think of this way, if the rear squats it's picking up the rear wheel. If the rear rises, it's pushing down on the rear wheel.

:iamwithst If the rear compresses when you exit a turn it's going to take the weight off the front tire and cause the bike to push the front through the turn.

 

There is a balance that needs to be achieved. You cant just put a ton of anti-squat into the suspension because the rising chassis will unsettle the bike. Likewise you cant have to little anti-squat or the power will not be transfered to the ground efficiently. It's all about a balanced setup that will propel the bike and not create an unstable chassis. All of this logic is the same in cars but goes about it differently.

 

ALL objects of a signifigant amount of mass (motorcycles included) shift their weight under any + or - acceleration, for all you idiots, negative acceleration = braking. why do power wheelies work? most of the weight becomes transfered to the back of the bike (hence COMPRESSING the supension) therefore, when hitting the brakes hard, you produce a negative acceleration, and the weight transfers to the front of the bike.....compressing the front forks. that is why when you tighten up your rear suspension it is harder to wheelie,, the suspension will resist more weight load being tranfered. the same is true if you soften it up, the bike will wheelie easily. Also not that if you are holding a steady speed the bike is undergoing zero acceleration, and its the same as not moving at all. its all physics, specifically, rigid bodies of motion or dynamics.

 

In Keith Codes Twist of the wrist II he says that it extends. If you put your front tire against a wall and give the bike power the rear end will extend. Why is this?

thats a good book. I hope you have a chance to read it through a few times. Lots of the stuff doesn't sink in the first time.

and yes, the rear extends. Look at the geometery involved.

 

The rear suspension will compress under hard acceleration but once you get up to speed will extend.

 

The rear suspension will compress under hard acceleration but once you get up to speed will extend.

Your swing arm pivot is higher then you rear axle correct?