Was Bad Brakes - Now Fork Design (Split)

[Bounce]

The thread was originally about the FJR brakes. The OP pointed out that his comment was best for another discussion here but I reflexed and replied to it when I shouldn't have/ My penance is to split the hijack off and put it here instead.

2. Last winter I had two fork seal leaks develop (I think I might try not installing the damn mid bushing next time - pain in the ass to remove, but that's a whole other conversation).

Is there a reason (besides convenience) to leave out a fork's mid bearing? I would think Yamaha put them in there for a reason.

 

[Bounce]

From Fred W

Is there a reason (besides convenience) to leave out a fork's mid bearing? I would think Yamaha put them in there for a reason.

Assume that you meant bushing, since forks don't have bearings.

Yes, the reason to leave out the center bushing would be to reduce friction (stiction) and extend the wear intervals on the bushings' teflon coating. Having three support points in the fork slider will mean that the forks have less ability to slide freely along the inner fork leg as it flexes and becomes less perfectly straight. And it will flex in normal use. Yamaha may have had a purpose in mind for adding the center bushing, but it turns out that it is not actually needed and actually hampers the functionality.

From Me

yeah. my mistake. thanks for the info. i figured removing one would increase flex and lead to binding.

From -Winpro-

From Me

I don't speak emoticon. Is there an emoticon-to-English dictionary somewhere?

 

[Bounce]

From 08FJR4Me

There must be a good reason for having a third bushing in the Gen2. Why do Gen1's need fork braces and Gen2 folks don't. Fred is right that it creates more friction but in my opinion it is a trade off between better handling characteristics. The front shocks become more stable with three bushings versus only two. At least that's what I think but then again this is the internet and anything can be true. So what do the Gen3's have? 2 or 3 bushings?Sorry for getting off topic but to stay on topic my brakes were squealing like a pig on the way home today in traffic. They have been that way for a while now.

Glazed over disk? They don't look it. I put OEM pads from Yamaha in last year. I am getting tired of the noise factor.

There is a descriptor for each emotion. I believe the one I used means confused.

Dave

 

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From

MCRIDER007

Yamaha may have had a purpose in mind for adding the center bushing, but it turns out that it is not actually needed and actually hampers the functionality.

I think this is an opinion rather than a proven fact and certainly wasn't my experience when I rode my 05 and 08 back to back......and I think the GEN3s are still using the center bushing. If the center bushing is causing the lower bushing to wear out then its still a good trade off because a GEN2 with worn bushings still rides and handles better than a GEN1 (my opinion based on actual riding experience when I owned both at the same time).

 

[Bounce]

From HotRodZilla

Yeah, this suspension thing is more backyard engineering by people who don't really know what they're talking about. One of the suspension shops does that to the GenIIs. I'd be pissed, and they would redo their work to install all the bushings.

 

[bluesdog]

When I had occasion to have the forks split for the AK-20 cartridges, I had the option of eschewing the middle bushing, but since there appeared to be little evidence of excessive wear at + 32K km, (20K miles), I followed the 'if it ain't broke' philosophy.

 

[Bounce]

From Chiefblueman

Hmmmm. When I purchased AK20 cartridges from Traxxion Dynamics, Lee Spitler, their FJR suspension guru, made a point to tell me not to install a fork brace on my Gen1. Not needed at all. He also prefers to remove the center bushing from Gen2 forks.

I installed Galfer lines on my non ABS FZ1 and on my ABS equipped '05 FJR. FZ1 - definitely firmed up the braking but did not increase braking power.

On the FJR I'd say it wasn't worth it. A bitch to install, a bitch to bleed. Still have a little air in the front that I can't seem to chase out.

From Fred W

I'm just one of those people that "don't know what I'm talking about", but I can say with total conviction that my 1st Gen FJR did NOT need the fork brace that was on it when I bought it used, and having that brace on the bike did NOT make my front forks any more stable or improve the handling as compared to when I removed it. To the contrary, what it did was to cause the forks to slightly bind, and be less responsive to small bumps, so after I took it off I sold it.
The 3rd Gen "A" model forks are of the same design as all 2nd Gen forks. The upper and lower bushings have updated part numbers (maybe they will slide or wear better?) but the center bushing is the same part number as on 2nd Gens. The "ES" model's upside down forks do not have any bushings at all in the design. Just an oil seal and dust seal.

From HotRodZilla

No Fred...Rule #11. I'm not allowed to say you're wrong. I would never break that rule. How would I live with myself.

I just seriously doubt Yamaha's engineers are running around putting extra parts in random places. I'm figuring they observed something that made them decide to add another bushing, and I don't think it was the ability to sell more bushings.

Although they haven't been 100% successful with all 'improvements' it seems their plan with each generation is to improve upon the last platform. They saw something about the GenI suspension that needed improving and they added that middle bushing. Nearly everyone with a GenI and a fork brace says it makes a world of difference. GenII riders, not so much. The GENII forks seem to be better than the GenI forks, just like the GenIII shock is better than the GenII shock. Pulling a bushing out because a guy on the Internet has a theory is a bad idea. Sorry!!

From Me

I was thinking that no one is wrong. It's the 21st century and we all need to avoid heated debate. With that in mind, I was originally thinking (simply thinking or thinking simply) the extra one had something to do with either binding or wear within a 2 bushing system.
But I'm neither a suspension expert or a Yamaha engineer.

 

[Bounce]

From Fred W

I agree with you, AJ, that blindly following Internet forum theories is not often a great idea. But unless / until someone actually experiments with it and reports back first hand results, how can anyone say for sure? So far we've heard only Internet theories and conjecture that having the third bushing must improve things. No direct before and after comparisons

OTOH, at least one shop that makes their entire livelihood modifying and tuning performance motorcycle suspensions believes that the extra bushing is detrimental and outright removes it. That is not a guy on the Internet. To me that suggests it is worth not poo-pooing or nay saying and maybe further actual experimentation would be worthwhile.

The point is that one can make a good theoretical case for it either way. The proof is in the pudding.

@Bounce - The second gen bushings are known to wear at a much faster rate than first gens. Now, that may, or may not, be directly related to having the third bushing in there. With no good evidence we would never know.

 

[MCRIDER007]

From Fred W

I agree with you, AJ, that blindly following Internet forum theories is not often a great idea. But unless / until someone actually experiments with it and reports back first hand results, how can anyone say for sure? So far we've heard only Internet theories and conjecture that having the third bushing must improve things. No direct before and after comparisons
OTOH, at least one shop that makes their entire livelihood modifying and tuning performance motorcycle suspensions believes that the extra bushing is detrimental and outright removes it. That is not a guy on the Internet. To me that suggests it is worth not poo-pooing or nay saying and maybe further actual experimentation would be worthwhile.

The point is that one can make a good theoretical case for it either way. The proof is in the pudding.

@Bounce - The second gen bushings are known to wear at a much faster rate than first gens. Now, that may, or may not, be directly related to having the third bushing in there. With no good evidence we would never know.

I'm assuming that by "no direct before and after comparisions" you are talking about a blind test on 2 indentical GEN2 FJRs, one with the middle bushing and one without. That probably is not going to happen and I will admit that when I say I think the GEN2 forks handle and ride better than the GEN1s, I can't say for certain that the middle bushing is the only thing that is different between the forks. I have long wondered if the GEN2 faster wear on the lower bushing was actually caused by tighter tolerances (or less polishing) on the lower fork leg rather than the presence of the middle bushing. Another thought I had today is whether the upper fork tubes on the GEN2s may have slightly thicker steel to increase rigidity. The tubes have different part numbers which may just be due to the different size of the hole in the bottom of the tubes, but if Yamaha made even a slight increase in the thickness of the tube walls that could explain why the GEN2 forks appear to be more rigid. There are a couple of tech days coming up, maybe someone could check this if they are doing fork oil changes on both a GEN1 and GEN2.

In regard to the effectiveness of a fork brace, I have not ridden a FJR with a fork brace but have not experienced any improvements on other bikes with fork braces, at least not on those that have been built in the last 20 years. However, if the tube walls on a GEN2 are thicker than those on a GEN1, I think that might explain why fork braces seem to be more effective on GEN1s, I really can't see how the middle bushing would have any impact on the effectiveness of a fork brace. There are negatives to a fork brace besides the additional weight. A standard 3 piece fork brace can cause additional stiction unless it happens to be a perfect fit....which probably doesn't happen that often. Kuryakyn makes a 5 piece fork brace that offers fitting adjustability and anyone wanting to install a fork brace probably should avoid the 3 piece models.

 

[JamesK]

I've been running a SuperBrace fork brace on my Gen 2 for over 200k miles. I have been able to get around 80k miles out of a set of bushes and seals (always running all 3 bushings). I think it helps and will continue to use it.

I can't speak for the quality or fit of the other fork braces, but the SuperBrace unit is very well built and fits like it's OEM.

 

[garauld]

From Bounce:

Assume that you meant bushing, since forks don't have bearings.

From Wikipedia:

Bushing may refer to:

• Bushing (bearing), a type of plain bearing
• Bushing (electrical)
• Bushing (isolator), a mechanical device used to reduce vibrations
• Threaded bushing, a metal sleeve with screw threads

From me:

 

[08FJR4ME]

Just as an FYI I did my first fork rebuild at 64K miles. Up until then they had not been touched and that includes not changing the oil out either. Come to find out the oil wasn't all that dirty and the bushings did show wear but not to the extent that I expected. Now I do live in the land of flatness and venture to other states to tromp on the old beast once and a while. With that said forks are like tires. Everyone is going to get different types of wear.

Still sticken to the 3 is better than 2 theory until someone proves it wrong.

Dave

 

[Fred W]

I'm assuming that by "no direct before and after comparisions" you are talking about a blind test on 2 indentical GEN2 FJRs, one with the middle bushing and one without. That probably is not going to happen and I will admit that when I say I think the GEN2 forks handle and ride better than the GEN1s, I can't say for certain that the middle bushing is the only thing that is different between the forks.

The test need not be blind, though if it were that would add some credibility to the perceptions.

I guess I was thinking more of a before and after test on the same bike (to remove any other bike to bike variability) where someone removed the middle bushing and saw an improvement in compliance or loss of stability after the change. The fly in the ointment is that, usually when we are inside the forks we are also making other changes (improvements) to the forks, such as new bushings and oil at least. That would taint the results.

In regard to the effectiveness of a fork brace, I have not ridden a FJR with a fork brace but have not experienced any improvements on other bikes with fork braces, at least not on those that have been built in the last 20 years. However, if the tube walls on a GEN2 are thicker than those on a GEN1, I think that might explain why fork braces seem to be more effective on GEN1s,

I see claims for improvements in motorcycle handling with to the use of a fork brace that just do not make much sense to me. People like to hold the wheel between their knees and lever on the handlebars and say, "See! The brace stiffens the wheel from turning laterally", but realistically, how much are we actually levering on the handlebars? I don't even grip the bars very tightly when riding, so how important is it to hold the wheel perfectly perpendicular to the bars? And what road forces are trying to deflect the wheel laterally that we need to stiffen against? What exactly, from a mechanical sense, are the braces supposed to be accomplishing? I've never felt a need for increased precision in pointing the front wheel.

Any fork brace can do only one thing, and that is to clamp the two lower fork tubes so that they remain parallel to each other. It will not magically stiffen the (much longer and thinner) upper fork tubes, so they will still flex around the same amount as you ride over bumps.

I really can't see how the middle bushing would have any impact on the effectiveness of a fork brace. There are negatives to a fork brace besides the additional weight. A standard 3 piece fork brace can cause additional stiction unless it happens to be a perfect fit....which probably doesn't happen that often.

I suspect that you are right and that variability may explain some of the difference in perceptions about using braces. Even if the brace is manufactured to exacting tolerances, the outside of the fork tubes and their relationship to each other are probably not as precise, meaning the brace would fit differently on various examples of the same model bike. Any brace that forces the lower fork tubes into a position not naturally aligning with the uppers will increase the friction and add stiction.

Of course, there are also wide variations in how people perceive almost anything in life, and motorcycle handling is certainly no different in that regard.