Been thinking- fork swap

All I am seeing is the stem bearings. Top and bottom.

I am not seeing anything about brakes, wheels etc. Let me know if I am seeing something different than you.
 
BrentMartell said:
All I am seeing is the stem bearings. Top and bottom.

I am not seeing anything about brakes, wheels etc. Let me know if I am seeing something different than you.
Click to expand...

You are right....just bearings but lets me swap the COMPLETE front ends of my 2 bikes without messing around with brakes etc.

Maybe my last post was a little dramatic but I was getting overwhelmed with the prospect of boring and shimming for two bikes. This lets me switch 2 ENTIRE front ends between my GasGas and Honda in a totally reversible and EASY fashion. All I need to change is the steering bearings. Very convenient.

The fact that I have 22mm Tclamps for the Showa suspension will mean minimal changes to handling....I'm just waiting to hear what your final verdict is on rake/trail changes.
 
I am going to run it with stock gg offset and see what it does. I have no clue how much 3mm at the axle affects all else. I might need to go 20mm offset to push the front out a little. I know a change at the clamp makes a bigger diff at the wheel, just very little experience. My KTM SX had 18/22 adjustable clamp and I ran 22 always. I want to measure the axle on it and see where it is. It turned well, and was stable. Loved that little bike. The gg at high speed acts weird but I personally think it is the suspension not the rake and trail. I could be very wrong though. Would not be a first time. LOL
 
Offset

Okay....I had some wrong information....

The offset I have available to me on the RG3's is 20mm. I could also use the stock Honda clamps (Preferred cuz they work GREAT with my Scott's submount).

I want to make sure I understand your measurement of axel to fork offset because it will affect the T-clamp I choose. As my Honda or RG3 clamps are +2mm or -2mm from GG stock, I could use either to compensate for the 3mm difference in axel placement. I just have to understand which way I'm trying to go.

Here goes......from how I understand your measurement of the axel position on the Honda, it is 3mm closer to the steering stem axis. This would move the contact patch 3mm further back behind the "projection" of the steering stem axis on the ground and increase the "castering" effect and thus stability and traction.

To push the axel (and forks) back away (forward) from the steering stem axis (or to return the contact patch forward toward the steering axis projection on the ground) would I not want a greater offset?

It seems to me that the Honda T clamp would be a perfect choice by moving the forks 2 mm forward.

Does this sound right or am I missing something?

This might be helpful for you in tuning your hybrid set-up:

http://www.rekluse.com/e-Axle_mailer4.pdf

Thanks
 
The measurement is from the centerline of the forks to the center of the axle.

The offset measurement is you have described. Honda, depending on year either have a 22 or 24 offset. 22 is less steep then 24. In other words 24 brings the wheel closer to the bike.


OK, here is what I do not have and need. Does anyone have the rake measurement for the 2011 GG? Since I am using a 2005 Honda fork I am using their measurements for reference. 26.5 rake 4.3 trail. 24mm offset.
 
Brent,

I think your understanding of triple clamp offset is backwards and Zhack is correct. The offset number(20mm, 22mm, 24mm, etc.) is the dimmension from steering head center to fork tube center. Therfore, the greater the offset the farther foward the front wheel. There is more to it than that though with rake and trail in consideration.
 
I see. Yes that is backward from what I am reading and seeing in the mags and websites. My KTM has 18-22 offsets. The book says for more stability go to 18mm. For quicker turning go to 22mm.

Quote from Bankes:
As a general rule, less fork tube to steering stem offset yields more trail and hence, up to a point, more stability. More fork tube to steering offset yields less trail and less stability.

In this little thread there is a diagram that shows more offset reduces trail and less offset increases trail. The measurement is based on how far the center line of the fork tube is from the centerline of the steering stem. The further (24) the forks are from the stem the steeper the fork tube angle and therefore the trail is reduced. Less trail means less stable. It also means the front wheel is getting closer to the bike.
http://www.thumpertalk.com/topic/747731-22-mm-triple-clampswhats-the-downside/
 
I would really love to see a spec on the gg for rake and trail. I have no issue measuring the trail. The rake seems a little more difficult since a slight variance in tilt of the frame would change the measurement. I guess sag etc would have to be perfect to get that number correct. I suspect the manufatures measure the head angle/rake from a jig. Ugh. Curiosity is killing me.
 
Brent,
Where did you get the Honda rake and trail data?
How did you measure axle offset (center of fork leg) to center of axle? Is there any kind of center marking on the fork leg or did you eyeball it?
Thanks
 
center to center as you mentioned with digital calipers. Found center line of tube with calipers, marked it. etc.

Honda provides those specs on the rake and trail. Looked them up via google. Almost all the other brands have this info. Not gg of course.
 
And you found that GG axle offset is 3mm greater than Honda, correct?

If that is the case, I will use my 24mm Tclamps for the Honda and "recover" 2 off the 3mm decrease in offset leaving 1mm decrease.

That 1mm decease in offset will be like changing the Gg stock offset from 22 to 21 which will increase trail slightly. I will just try it and see how it feels. The theory is that increased trail will increase straight line stability and steerIng effort but I doubt I am a sensitive enough pilot to feel it.

If it is a noticeable negative change, I can use an e-Axle (if I can find one....I have just learned that Rekluse no longer makes them and is out of stock of them) or possibly lower th forks in the clamps to upright the forks slightly, decrease rake and decrease trail.

That's the plan anyway.
 
Last edited:
Update: put some break in miles on the new forks. bolted them to the honda. They are awesome. Can't wait to get my gg done. Not as plush as the zokes in the first 4-6 inches but way better everywhere else. I think a few shims removed in the base valve to add a little more plushed to the initial will make things awesome in the wide variety of terrain I ride: gnarly rocky canyons to wide open desert roads with huge g outs.

Zhack- if you put the honda clamps on let us know how the steering stops worked out. This is one of the reasons why I chose the route I did. I also think you might want to dig a little into the offset. I can not find anything that suggests 24 mm decreases the fork angle. Maybe I am just stupid but so far everything I have found indicates the fork angle is steeper with the bigger offset number. From the literature, it says a measure is taken from the stem to the fork centerline. 24mm means the top of the fork is further away from the stem. The affect then on the bottom of the fork is the axle is moved closer to the bike and therefore trail is reduced. If this is in fact correct then the steeper offset and closer axle of the honda will likely make the front end less stable and the steering quicker.

Me- I am leaving it alone until I test. I have no clue what that 3mm means in the grand scheme. I can certainly move the forks down in the clamps and see what happens.
 
Offset

Increase in triple clamp offset moves forks (which are parallel to the steering axis) away from the steering axis at both top and bottom clamps evenly so that the long axis of the forks are still parallel to the steering axis. All of my other conclusions are based on this assumption.

Because there is rake, an increase in Tclamp offset is not totally horizontal so in addition to moving the forks forward in a direction perpendicular to the steering axis, the is also a small vertical component. As the forks move forward, they also move up. Thus as the forks fall back down to the ground (assuming they were not lowered in the Tclamps to compensate) the rake angle decreases slightly as the fork are slightly uprighted. As rake decreases, trail decreases ans steering is ever so slightly less stable.

That, and the fact that increasing offset also decreases trail directly by moving the contact patch toward the projection of steering axis on ground.

BTW... I measured and remeasured axle offset og GG and Honda and found the difference to be closer to 2mm greater for GG than the 3 you found. I was worried that we got different numbers so I checked it abnout 10 times. Looks like 2mm difference to me....

So...things are even better then I thought. With the 2mm different axle offsets and the 2mm triple clamp differences they will nearly perfectly cancel each other....thus I get Honda forks with beautiful GG geometry unmolested.....
PERFECT!
 
I gotcha. I think I have a better understanding now. The forks are futher forward with more offset. It would be interesting to what the actual number is for the trail.

http://www.brpmoto.com/product-info/controls/triple-clamps

If it is in fact 2mm, I am sure you are right, the difference is pretty minimal. It might show up on the high speed road transfer sections but I doubt I would notice it in the tighter stuff. I just can not wait to get this bike done. My clamps are ready. If all goes well, I might be able to test on Saturday and race on Sunday. We have 90 mile desert race. Would love to put this bike on the overall podium.
 
FWIW: You may want to weigh the bike under the front wheel and the rear wheel to get baseline measurements for the weight bias before and after the swap...If you do this and see a big difference in the bias you will know what you have to work on to get it inline with how you want the bike to steer/handle.

Eric
 
Thanks Eric. I assume you are speaking to Zhack as I honestly can not imagine 2mm in the wheel base making any difference without changing the rake or offset. I am not doing currently. However, I might weigh the front with forks at diffferent positions to see what it does.
 
Update. Something I had not considered was the overall length of the showa. From the top of the axle hole to the indicator line on the fork is about 6mm difference. The showa's are taller. Measuring the zoke to the line is about 36.13 inches. Showa is 36.40. So, the logical answer is to push the showa up in the clamps. Right now I am about 1/8 inch or 3mm taller on the showa then the zoke. I am not yet sure how that equates to handling etc with a 2-3mm difference in axle offset

because

Testing did not go well. I installed a set of seals from a kit that wound up being too tight. On the 450 the weight bias was enough to overcome the stiction. On the 300 it was not and the forks would not settle in the stroke for turns or higher speed. I did not like that. The bike did not feel well to me and I missed Sunday's race. I could have raced but would have had to back off the pace. No good.

I will install new seals and bushing etc and re-test. The bushing were destroyed in the process of pulling apart the forks due to how tight they were.

Good news- the bored lower clamp and sleeved upper seem to fit the forks just fine. I used the honda wheel and brake assembly for initial testing. I hope to have a chance this week to look at mods to fit the gg wheel and brakes.
 
Update:
I broke down and bought a honda front wheel assembly and lower brake assembly. When I have more time etc I will see what it will take to mount the gg wheel and brake. Currently the nissin caliper for GG is different then the honda.

Cost list, prices may vary:
Bore triple clamp and machine shims to showa specs- $60
Honda forks- $200
Honda front wheel assembly- $142
Honda brake caliper- slave: $48
PW fork rebuild kit- $63
HV1 Bell Ray 5 wt oil- $20
FC inner chamber spring $35
Total $568

Optional
Race Tech complete Gold Valve inner already set up - $200
New .46 honda springs $20

New Total $788


FYI-I have no idea why the PW kit for the forks came with the wrong seals and wipers. The other kit specs measured out perfectly and look totally different as well. I had to get new bushings and wipers. I had an extra set of SK seals. That whole ordeal cost me another $75 I would guess.

In a week or so I will have better idea of what the gg brake and wheel set up is going to look like and cost. If it all works out for less than $100 to machine spaces and set up the brake bracket it will bring the actualized cost down about: $478 This does include sales tax on items purchased locally btw.
 
Update- The brake slave cylinder mounting bracket is all that is needed for the lower brake mount. If you compare the GG unit to the Honda they look different but once mounted it works. I spent $48 on the brake from ebay but could have probably spent 10-15 less for the bracket.

Put 115 miles on it Sunday and have a few balance issue's to sort out. The fork springs I think are too heavy. They are either 46 or 47. Depending on who you believe. I am going to try 44's. The front is too light and the butt too low IMO. However, the whole system seems to be coming together well enough. I don't like the fact the showa's are a solid .25 INCH taller to the mounting guide grove and that requires a bit of thought on how to install the fork in the clamps. Pushed up in the clamps makes adjusting the comp a real chore.
 
I have some brand new 50mm Marz's from a Husky for sale cheap! They come with triple clamps but they are from the Husky too. You could try to get some triples from an MC 250.
 
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