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I've looked at them some more. I think I'm going to make these work. The rod unscrews from the valve at the bottom. Having a mill and lathe at home, I think I'm going to buy some 12mm tight tolerance polished shaft, and just make a couple that are 1" longer. The adjuster rod inside is just a length of small diameter aluminum with the ends cut into a hex. Not the ease of ND4's mod, but the same functionality. I'll get the 1" extra travel, and have the external adjustment of the Racing Bros kit. Before I go to the trouble though, it may be worth measuring the OEM dampening rod, just to make sure the Racing Bros kit hasn't already extended the rod length.
 

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Discussion Starter #342
I've looked at them some more. I think I'm going to make these work. The rod unscrews from the valve at the bottom. Having a mill and lathe at home, I think I'm going to buy some 12mm tight tolerance polished shaft, and just make a couple that are 1" longer. The adjuster rod inside is just a length of small diameter aluminum with the ends cut into a hex. Not the ease of ND4's mod, but the same functionality. I'll get the 1" extra travel, and have the external adjustment of the Racing Bros kit. Before I go to the trouble though, it may be worth measuring the OEM dampening rod, just to make sure the Racing Bros kit hasn't already extended the rod length.


yes. or check with racing bros.... i know the racetech kits rod is 20mm longer if i remember correctly. This is where i got the idea for my simple fork mod.
 

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Can anyone explain what this is actually doing? I have spoken with my suspension guy at length about this and neither of us can really figure this ut. What we are fairly certain is not happening is any increase in preload or suspension travel. Unless I'm missing something, all that appears to be happening is a lengthening of the damper rod.

We know that to increase preload the main springs will need to be compressed at resting. This can only be accomplished by increasing the strength of the top out spring by a large margin, or by disassembling the forks to shim the bottom of the main spring (which may not even increase preload if the top out spring is very soft), or by shortening the effective length of the inner fork tube.

This mod doesn't seem to affect dampening.

It does affect geometry by raising the front of the bike, so maybe that is where the effect comes from?

I'm not asking how the bike "feels different". That is fairly well documented. i'm asking WHY this works.
 

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Can anyone explain what this is actually doing? I have spoken with my suspension guy at length about this and neither of us can really figure this ut. What we are fairly certain is not happening is any increase in preload or suspension travel. Unless I'm missing something, all that appears to be happening is a lengthening of the damper rod.

We know that to increase preload the main springs will need to be compressed at resting. This can only be accomplished by increasing the strength of the top out spring by a large margin, or by disassembling the forks to shim the bottom of the main spring (which may not even increase preload if the top out spring is very soft), or by shortening the effective length of the inner fork tube.

This mod doesn't seem to affect dampening.

It does affect geometry by raising the front of the bike, so maybe that is where the effect comes from?

I'm not asking how the bike "feels different". That is fairly well documented. i'm asking WHY this works.
Don't overthink it!

You're increasing the length of the dampener rod which the spring seats on in the bottom of the stanchions. Might help you guys to look at a diagram.
 

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Can anyone explain what this is actually doing? I have spoken with my suspension guy at length about this and neither of us can really figure this ut. What we are fairly certain is not happening is any increase in preload or suspension travel. Unless I'm missing something, all that appears to be happening is a lengthening of the damper rod.

We know that to increase preload the main springs will need to be compressed at resting. This can only be accomplished by increasing the strength of the top out spring by a large margin, or by disassembling the forks to shim the bottom of the main spring (which may not even increase preload if the top out spring is very soft), or by shortening the effective length of the inner fork tube.

This mod doesn't seem to affect dampening.

It does affect geometry by raising the front of the bike, so maybe that is where the effect comes from?

I'm not asking how the bike "feels different". That is fairly well documented. i'm asking WHY this works.







Get a New Suspenion Guy.... LOLOL
 

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Don't overthink it!

You're increasing the length of the dampener rod which the spring seats on in the bottom of the stanchions. Might help you guys to look at a diagram.
Preload would increase if the stanchions had a physical stop that made it impossible for the whole assembly to get any longer. In that case lengthening the dampening rod would force the spring to compress and thus increase preload. But don’t think that’s the case here. Because ride height is increasing we know the forks are extending farther.

Am I wrong? Are we increasing the dampening rod length to such a degree that the upper and lower sections of the fork are maxed out in length and some preload is actually achieved?

A lot of things are changing with this setup; oil level/air gap, basic bike geometry, unloaded fork length. But I can’t make sense of any of those having this ultimate effect.

Do you have a diagram you could point me to that explains your understanding? I’m genuinely interested in understanding how these results are being achieved.

I am “overthinking” This because people have adapted the OG fork mod to the SF in what appears to be a sketchy way. I’m trying to figure out if it’s worth the trouble to put together out a better implementation for the SF grom (which is what I have currently).
 

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Preload would increase if the stanchions had a physical stop that made it impossible for the whole assembly to get any longer. In that case lengthening the dampening rod would force the spring to compress and thus increase preload. But don’t think that’s the case here. Because ride height is increasing we know the forks are extending farther.

Am I wrong? Are we increasing the dampening rod length to such a degree that the upper and lower sections of the fork are maxed out in length and some preload is actually achieved?

A lot of things are changing with this setup; oil level/air gap, basic bike geometry, unloaded fork length. But I can’t make sense of any of those having this ultimate effect.

Do you have a diagram you could point me to that explains your understanding? I’m genuinely interested in understanding how these results are being achieved.

I am “overthinking” This because people have adapted the OG fork mod to the SF in what appears to be a sketchy way. I’m trying to figure out if it’s worth the trouble to put together out a better implementation for the SF grom (which is what I have currently).

Let me see if I can find you a suitable diagram.

There is NO.. NONE... ZERO preload being created by doing this. It's merely just changing the length of the dampener rod so that it's taller while it sits atop the internal spring. If anyone says it creates preload, they're entirely wrong. The ONLY way preload can be created is by taking off the fork leg and adding shims on that end of the fork. The cartridges have enough travel between the top out spring and the physical stop inside the stanchion that allow this modification to happen.


Edit, Picture:


 

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Discussion Starter #349
Can anyone explain what this is actually doing? I have spoken with my suspension guy at length about this and neither of us can really figure this ut. What we are fairly certain is not happening is any increase in preload or suspension travel. Unless I'm missing something, all that appears to be happening is a lengthening of the damper rod.

We know that to increase preload the main springs will need to be compressed at resting. This can only be accomplished by increasing the strength of the top out spring by a large margin, or by disassembling the forks to shim the bottom of the main spring (which may not even increase preload if the top out spring is very soft), or by shortening the effective length of the inner fork tube.

This mod doesn't seem to affect dampening.

It does affect geometry by raising the front of the bike, so maybe that is where the effect comes from?

I'm not asking how the bike "feels different". That is fairly well documented. i'm asking WHY this works.

Posted this in the SF fork thread for you

The mod extends the damper rod length. The fork bottoms out on the top cap, by extended the damper rod you push the fork lower further away from the top cap at full extension, thus increasing fork travel. (See my OG fork mod link in my signature below). With the OG forks you can easily get another inch of travel (which is huge considering stock travel is 3.9, so over 25% travel gained), which puts your sag numbers in a more proper spot with the stock spring, paired with some thicker oil actually makes the stock forks decent. The concept for this SF fork mod is the same as mine but not as much extra travel (~1/2in).
 

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Posted this in the SF fork thread for you
I saw that! Much appreciated. The mechanics of it make sense.

So why do you think it ends up "firmer? feeling? If it's not preload or spring rate, is it additional compression dampening being caused by the longer stroke?
 

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Discussion Starter #351
I saw that! Much appreciated. The mechanics of it make sense.

So why do you think it ends up "firmer? feeling? If it's not preload or spring rate, is it additional compression dampening being caused by the longer stroke?
Firmer because you are compressing the main spring more at the end of the stroke + the addition of thicker oil to make the shim stack create more dampening.

Similar in concept to preload, but in this form, its actually more proper because like stated, you increase fork travel (on the OG grom forks) by 25% which puts the stock sag with a normal 150-160lb rider in a more adequate zone (the fork sags just as much but you have another inch of travel before bottoming out).
 

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Firmer because you are compressing the main spring more at the end of the stroke + the addition of thicker oil to make the shim stack create more dampening.

Similar in concept to preload, but in this form, its actually more proper because like stated, you increase fork travel (on the OG grom forks) by 25% which puts the stock sag with a normal 150-160lb rider in a more adequate zone (the fork sags just as much but you have another inch of travel before bottoming out).
I see. The spring is "firmer" feeling at the bottom of the stroke because we hit the bump stop and inch of travel later. The stock setup bottoms out on the bump stop way before the spring can provide that support, especially for a heavy rider. This makes way more sense.

With all this in mind I do think this is worth trying to cobble together something more legit than the current proposed solution for the SF grom. I am going to see what I can come up with.

THANK YOU for the explanation.
 

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Discussion Starter #353
I see. The spring is "firmer" feeling at the bottom of the stroke because we hit the bump stop and inch of travel later. The stock setup bottoms out on the bump stop way before the spring can provide that support, especially for a heavy rider. This makes way more sense.

With all this in mind I do think this is worth trying to cobble together something more legit than the current proposed solution for the SF grom. I am going to see what I can come up with.

THANK YOU for the explanation.
No problems! glad my explanation helped!
 

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Just got a e-mail to come check out your ND4 mod because i just did one for the Z125 and posted it on our forum.
I read all 36 pages and now know what I'm in for ... Lol
Nice thinkin man ...
 

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@nd4spdbh thanks for this tutorial. Just did this mod on my 15 OG, and it made a nice improvement to both ride quality and handling. I like how it’s a bit less twitchy with the added trail.

I didn’t change the fork oil and it’s still plenty firm for me. On a side note, it’s quite spectacular the amount of stiction in these forks. LOL It felt like it got worse after this mod, but that’s probably because I have a lot more usable stroke and I’m no longer sagged through 60% of it.

Quick tip for anyone attempting this: I suspended the front by hanging from the lower triples until the tire was barely above the floor. Once the 36mm fork caps are completely loose, I lifted the front wheel slightly (by hand) and slid a 2x4 under the tire. This exposed just enough of the damper rod out of the top of the forks to get some vice grips on for loosening the screws. Do what you need to create the new stack up top, retorque the little screws, and carefully remove 2x4 and lower the wheel back down to thread fork caps back in.


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Which one are you talking about? I've seen a couple of different ones.
I think bucknut’s reply was in response to the inquiry from @superdappa in regards to this mod on 2019 models.

The first post in this thread states:

NOTE: This does not work on the 2nd gen groms as they have different fork caps.

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I think bucknut’s reply was in response to the inquiry from @superdappa in regards to this mod on 2019 models.

The first post in this thread states:

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Sorry, I wasn't clear. Which SF mod was he talking about? I've seen at least two - changing oil and the other is a preload mod.
 
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