"True" versus "False" Trail

[cvegmond]

Why are we complicating the front axle trail definition with a "true" and "false" trail? Both are measures of front-ends ability to track well and steer, right?

BDM says my K-9 has 4.35" of trail. I'm pretty sure that is "false" trail or the trail and measure horizontaly and not perpendicular to the line through the streering head. Anyone know if BDM is quoting "true" of "false" trail?

The reason I ask is that the springer front end vendors like to talk in terms of "true" trail. 4-6 inches is great trail, but "true" trail should then be 1-3 inches?

Thanks, Cor.

 

[PurpleDog]

Custom Motorcycle Suspension Tuning - Rake And Trail - Street Chopper Magazine Online

 

[RubWhore]

Bigdog is quotin false trail

The differance is true is no raked trees and false is raked trees and a springer is figured totally differant cause of where the front wheel is in repect to the neck and the angle of the two

 

[Moespeeds]

A springer is completely different, and the trail is adjustable to a degree by changing the angle of the bottom rockers, essentially lowering or raising the front end of the bike and raking/deraking it. The manufacturer of your springer should be able to give you the optimum rocker angle.

 

[cvegmond]

A springer is completely different, and the trail is adjustable to a degree by changing the angle of the bottom rockers, essentially lowering or raising the front end of the bike and raking/deraking it. The manufacturer of your springer should be able to give you the optimum rocker angle.

Mr. Moe,
Yes, adjusting the rockers will change the trail, but that can't be much.

Is it not true that the rocker should not be perpendicular to the ground. I see most rockers at about 15-30 degrees from horizontal. That is fixed to give the wheel a good reaction to bumps. All springer manufacturers work in this range.

Better if the springer vendor would offer different length rockers to adjust the trail and allow some offset in the trees to provide good clearance for the gas tank and steering stop.

I am strongly considering a D-66 Springer from American Suspension. But it appears one will lose about an inch of trail going with this front (using the 0 degree offset trees).

The mixed discussion of "true" and "false" makes the comparison diffucult.

It's easier to ask: If you have a springer...can you tell me how it rides relative to the stock telescopic fork?

Thanks, Cor.

 

[BBChopper]

Custom Motorcycle Suspension Tuning - Rake And Trail - Street Chopper Magazine Online

Good info Jim!:2thumbs:

 

[RubWhore]

Nite and day differance in ride and its even better ifins you go to a 120 tire

 

[PurpleDog]

Mr. Moe,
Yes, adjusting the rockers will change the trail, but that can't be much.

Is it not true that the rocker should not be perpendicular to the ground. I see most rockers at about 15-30 degrees from horizontal. That is fixed to give the wheel a good reaction to bumps. All springer manufacturers work in this range.

Better if the springer vendor would offer different length rockers to adjust the trail and allow some offset in the trees to provide good clearance for the gas tank and steering stop.

I am strongly considering a D-66 Springer from American Suspension. But it appears one will lose about an inch of trail going with this front (using the 0 degree offset trees).

The mixed discussion of "true" and "false" makes the comparison diffucult.

It's easier to ask: If you have a springer...can you tell me how it rides relative to the stock telescopic fork?

Thanks, Cor.

It seems to me you need to work with American Suspension to build you a springer specifically for your setup. I haven't personally done this yet as others have, but I've been studying on it. From what I have read, I note a couple things.......

Your front axle should be about 1/2" above rocker pivot point...They can make it a bit longer for the builder to trim for a dialed in setup per bike from what I am reading......

Gear Head College • Springer Geometry Correct?

Gear Head College • Why Springers

Gear Head College • Articles-Design & Engineering - Vehicle Geometry

My ride height is lower than a stock K9; therefore, I wouldn't just take Rub or Reapers specs and have it duplicated and expect it to be dialed in for my bike for example.
Although, I am curious what our stock tree offset is exactly? I tried measuring mine on the bike the other day, that didn't work good enough for me - trying to calculate everything to end up with the stated stock trail.

 

[cvegmond]

Dear Mr. Purple Dog,
I read the articles. The articles focus mainly on telescopic forks.

I struggle with what is the right amount of trail for the American Suspension Dragon springer as an application for a K-9. Since the rocker come in only one length, you only have one decision to make. That decision is the offset for the springer trees.

I believe both Mr RubWhore and Mr. Reaper are using the 0 degree offset trees.

Tree offset is the distance from the steering column out to the fork tubes. On my K-9 it looks like the a stock trees have 2.5 inches of offset.

Offset in the springer trees would lessen the trail...I think?

I would like to stay with the stock wheel and front tire.

I have quote from Mac at Twisted Steel Choppers for the whole springer package for about $3,000. It's a lot of money for just good looks...is it worth it?

Thanks.

 

[alhall88]

With anything less than 40 deg rake in the neck it is advised to use the 0 offset batwing trees. And yes the axle pivot point can be changed to get whatever look your trying to achieve but be warned this wont help the ride at all. I ordered 2 sets of springer trees with mine so I could play around with it. Found out in the end that the sweet spot of the axle was the recommended 3/4 above the pivot point. Don't get bent up on all the trail measurements because what you need to do is establish the stock frame height and then duplicate it unsprung with the new springer.

 

[Staffy]

All comments are on the money.....
I "believe" the preferred tree is the 0 offset - BATWING but will require some modifications to where you mount the tank or the stops (turn radius) no getting around that.

Being that the stock rake is 39 degrees (without the trees) we end up at "border line" and can use the DECAPITATOR trees which I have done and requires no mods to the tank or stops – works well when it comes to handling however do have some vibration on the handle bars at top speeds - not sure where that is stemming from. Am in the processes or switching out my 360 brake – didn’t do it for me. Am also attempting to mount the front fender this time around – will keep you posted, think it’s going to need new (longer) fender brackets.

 

[cvegmond]

All comments are on the money.....
I "believe" the preferred tree is the 0 offset - BATWING but will require some modifications to where you mount the tank or the stops (turn radius) no getting around that.

Being that the stock rake is 39 degrees (without the trees) we end up at "border line" and can use the DECAPITATOR trees which I have done and requires no mods to the tank or stops – works well when it comes to handling however do have some vibration on the handle bars at top speeds - not sure where that is stemming from. Am in the processes or switching out my 360 brake – didn’t do it for me. Am also attempting to mount the front fender this time around – will keep you posted, think it’s going to need new (longer) fender brackets.

Mr. Staffy,
Your comments are quite interesting. I agree that the Decapitator trees with offset would make for an easier installation and retain the turning radius and eliminate the need for spacers under the handlebars.

Do you think your vibration at high speed could be due to lack of trail because of the use of offset trees? What do you mean by "high speed"? Do you think fenders and brakes have something to do with your vibration?

Could you post a few photos of your K-9 with it springer front end?

Thanks, Cor.