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Old 12-16-2012, 05:42 PM   #71926
Mambo Dave
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I've seen examples of different internals in fork legs in mountain bike forks, but they have a fork brace.

I have to think that either, for normal motorcycles (which includes the DR650 since it isn't stellar in the suspension department), all those people who claim the fork braces they added really aren't doing anything to improve the handling and wind characteristics of their bikes, or that there is something to it, and thus balance in fork springs for forks without an additional brace is a good idea. So either I'm not understanding what a fork brace actually does to less-than-stellar forks, or tons of riders have been scammed by unscrupulous fork-brace manufacturers.
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Old 12-16-2012, 05:49 PM   #71927
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Fork braces don't just assist the axle to keep the sliders working up and down together, they also reduce fork twist generated under brakes that you get with a single disc. The DR forks are faily flexxy and this is a particularly noticable improvement that you get with stiffer USDs. When thay flex, they also bind a bit, so their bump absorption is not as good when loaded as a stronger fork is.
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Old 12-16-2012, 05:51 PM   #71928
Rob.G
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Quote:
Originally Posted by vfr870 View Post
I have a set of .42 kg/mm Moto-Pro fork springs in my KLX250S.... just a tad too soft so I called up Moto-Pro to order a pair of .44 kg/mm fork springs. Moto-Pro suggested that if I find the .44's too harsh I could use a .42 in one fork, and a .44 in the other to end up with a .43 kg/mm spring rate.
I put .48's in my KLX250S and love them. I thought .42's were the stock ones. Now I need more rear spring too. 'Course I need to do both ends of my DR650, so it's next in line.

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Old 12-16-2012, 05:52 PM   #71929
Mambo Dave
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Quote:
Originally Posted by BergDonk View Post
Fork braces don't just assist the axle to keep the sliders working up and down together, they also reduce fork twist generated under brakes that you get with a single disc. The DR forks are faily flexxy and this is a particularly noticable improvement that you get with stiffer USDs. When thay flex, they also bind a bit, so their bump absorption is not as good when loaded as a stronger fork is.
Good point.

So perhaps somehow that is what makes the bikes work better in the wind than slider-synchronization? I guess it's plausible.
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Old 12-16-2012, 06:31 PM   #71930
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Quote:
Originally Posted by Mambo Dave View Post
I've seen examples of different internals in fork legs in mountain bike forks, but they have a fork brace.
Yep, but the forks on my mountain bike would cost more a grand to replace.
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Old 12-16-2012, 07:20 PM   #71931
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Quote:
Originally Posted by BergDonk View Post
So you're not a fan of the latest SFF (Single Function Forks) MX forks as fitted to the latest KXs and RMZs?



Admittedly these have bigger (stiffer and stronger) axles than a DR, but small differences in oil levels and spring rates in a DR fork will not make a difference to the perceived or actual performance. Theoretically yes, in practice, no. In fact I doubt any pair of springs would measure the EXACT same rate due to manufacturing tolerances.
No, I'm not a fan, however see http://www.advrider.com/forums/showp...ostcount=72041.

Regards,

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Old 12-16-2012, 08:05 PM   #71932
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Quote:
Originally Posted by Mambo Dave View Post
If that were the case, Fork Braces would never had been invented.

I think he has a good point there when he suggested making sure they're close to even in an attempt to do whatever we can to make a better-handling bike. Redneck riders won't agree to it, but then they tend to be the ones adjusting the preload to get a change out of rate.
Redneck?





As opposed to just buying stiffer springs that come with some kind of warranty and a spec'd rate, instead of permanently cutting/sanding the stockers and hoping for the best?



'Too funny.
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Old 12-16-2012, 08:29 PM   #71933
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Originally Posted by Kommando View Post
Redneck?





As opposed to just buying stiffer springs that come with some kind of warranty and a spec'd rate, instead of permanently cutting/sanding the stockers and hoping for the best?



'Too funny.
Well, it wasn't meant as an insult.

I've bought aftermarket springs before, and I saw exactly what I was getting - they, too, were pretty much the same wire diameter, but substantially shorter. I felt like an idiot for not chopping the original springs after that considering that bike cost me less then $1000.

If was building up a track bike or something then, sure, I'd go for aftermarket springs again. For the DR650 I'm going to go with cutting them (at least once) equally, and adjusting pre-load to where it should be. With me skipping the part of doing an actual calculation of weights this bike will see, plus my weight, the guesstimation of cut springs will bring me just about the same chance of getting it 'right' as if I were to buy a known spring rate for a bike I really haven't ever fully loaded yet, and don't know the weight for anyhow.

I'm still holding that preload adjusts preload, and that's best reserved as a setting unto itself.
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Old 12-16-2012, 08:37 PM   #71934
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I was under the impression (possibly mistakenly) that fork braces cut out some of the side to side flex when cornering, too. I don't have them on the DR, but sure seemed different when cornering on the Strom. I could be a victim of my own imagination and marketing.
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Old 12-16-2012, 08:55 PM   #71935
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Quote:
Originally Posted by Kommando View Post
Redneck?





As opposed to just buying stiffer springs that come with some kind of warranty and a spec'd rate, instead of permanently cutting/sanding the stockers and hoping for the best?



'Too funny.
Springs can be cut and rate targets hit quite precisely. It's not hard to figure out how much of an increase in rate each coil (or fraction thereof) will be worth. As mentioned before, you can also measure the rate as you go. On bikes with little or no aftermarket support, or if you just need a rate that isn't being manufactured, it's the only choice you have available.

Regards,

Derek
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Old 12-16-2012, 09:18 PM   #71936
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Quote:
Originally Posted by Mambo Dave View Post
Wow! what a great idea! Not sure where I'd get the measuring apparatuses, but a damned fine idea!
Measuring apparatus.
See post #106
http://tw200forum.com/index.php?/top.../page__st__90?
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Old 12-16-2012, 09:21 PM   #71937
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Originally Posted by TrophyHunter View Post
I was under the impression (possibly mistakenly) that fork braces cut out some of the side to side flex when cornering, too.
Controlling flex during cornering is probably the main purpose of a fork brace. The other benefits are secondary.
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Old 12-16-2012, 09:21 PM   #71938
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Quote:
Originally Posted by motolab View Post
Slide carbs will always have a loss in bottom end to lower midrange of the rpm range at the larger throttle openings because the air velocity (and therefore the quality of the metering) is proportional to the engine rpm and inversely proportional to the throttle opening. Slide carbs require you to learn throttle control. When tuned properly (I say "tuned properly" because it is possible to mask many problems with an overly rich mixture), you cannot open the throttle to WOT or near WOT suddenly from low rpm without significant hesitation (its even possible to stall the engine if you dont back off). A properly tuned accelerator pump will help this, but is not likely to completely mitigate the problem. On the other hand, CV carbs allow you to open the throttle all the way from low rpm and will pull smoothly when tuned correctly, because the height of the slide automatically attempts to maintain a consistent velocity.

The ability to open the throttle to WOT from low rpm without hesitation with a CV carb does come with a price, and that is in a comparative lack of responsiveness in those areas where the combination of throttle position and rpm does not cause too much of a loss in in intake velocity with the slide carb.

Another area where the CV carb has an advantage is in the ability to change the fuel delivery curve based on rpm via the needle shape. On a slide carb, you can add or subtract fuel via tuning a circuit responsible for a given throttle position, but you cannot change the shape of the delivery curve in terms of rpm. For instance, if you had a lean and a rich spot at different rpm at a certain throttle position, you could fix the lean spot while making the rich spot even richer, or you could fix the rich spot while making the lean spot even leaner. You could not fix both. Unfortunately, these types of scenarios happen quite frequently.

The throttle pull on the TM40 is also quite a bit heavier than on the BST40.


Regards,


Derek
i knew i could count on you for more information than i could imagine i needed. its good to have people out there that understand this stuff and can give good reliable advice. the slide has the single stock hole, im after reliability, not performance here. the elbow has a unifilter attached to it but ill check the hose and connections, may even need a new filter. so is there any advantage in terms of the reliability of the slide and guide in going for the TM40 or am i better to persist with the stock carb?
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Old 12-16-2012, 09:26 PM   #71939
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Thumb cutting fork springs

Here is a good tool to help figure spring rates when cutting springs:
http://motorcycleinfo.calsci.com/Sus...aseForkSprings

I cut 4" off of the close coil end of my springs but I also lowered the front end 4" for my street tracker.
Coil bind is a concern when cutting a large percentage of the length so figure carefully.
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Old 12-16-2012, 10:38 PM   #71940
Adv Grifter
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Quote:
Originally Posted by BergDonk View Post
Fork braces don't just assist the axle to keep the sliders working up and down together, they also reduce fork twist generated under brakes that you get with a single disc. The DR forks are faily flexxy and this is a particularly noticable improvement that you get with stiffer USDs. When thay flex, they also bind a bit, so their bump absorption is not as good when loaded as a stronger fork is.
Good points!
A fork brace can reduce "stiction" and bike can feel more planted mid corner over bumps, rider feedback is better. Less stiction means better overall feel, better control, more confidence.
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