K2 / Proflex Riders Group
General => Tech Forum => Topic started by: Akagi on May 19, 2009, 01:22:41 am
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(http://img206.imageshack.us/img206/7162/cimg2918.jpg)
The bike is basically a NOS 757, but has a carbon swingarm upgrade.
After a year of first getting the bike, I have finally found the time and people to ride with. I found out quickly that the terrain here is very nasty here in Kelowna, Canada (I am only here for school). Very rocky, very dry, very loose, very nasty when you fall. Even the plants here hurt because they all have thorns... I am used to the flat forgiving nutrient rich soft soils in the province of Ontario.
Here are my first impressions:
The bike climbs great (despite the stock tires). I am incredibly out of shape, but I was able to keep up with the "B" group right off the bat, without having excercised in almost half a year. A lot of people riding longer travel super heavy looking All Mountain rigs with 2.25 tires. I think that when my IRC Mibro 2.1s arrive and a few more weeks, I should be able to outclimb most of them. The panaracer duster II really suck in my conditions, I wonder why they would put a specific (muddish) tire stock on so many proflex bikes.
For the Downhill, I had problems. I was able to keep up with the group while descending but I felt like I was almost on the edge of being out of control. I don't think it was really the suspensions fault. The rear suspension worked wonders while the Crosslink felt a bit harsh; I think the spring is a bit heavy for me. The Panaracer Dusters made me feel really unconfident about myself as I would slide laterally into ruts and other things. I felt like I couldnt steer where I wanted to, and the bike went where it wanted to go, all of this is at a decent speed too, it wasn't like I was locking the brakes.
The terrain was also very steep, and I found myself behind the saddle for a lot of it. Is this normal? I figure if I want to be one of the faster people I would need to stay on my saddle and pedal. There were times that I stayed on the saddle so I could pedal but something would end up suprising me and I would end up going over the handlebars. What can I do to improve descending while avoiding bailing over my handlebars?
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After I started going over the handle bars going up hill, I thought I'd best sort this out.
That was when I changed my elastomers on my XP-X & got the COR Spring upgrade. There is also a riding technique I read about which basically has your arms, hands, Shoulders, wrists as loose as possible to absorb shocks, and not tense which results in you leaving the bike.
You've mentioned your spring & tyres - google for the technique, but basically the modern bikes are going to have more travel & on certain runs will have an advantage, but you're on a great bike so who cares!
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How tall are you and what do you weigh?
Forgive the personal Q's but it's just to judge how suitable that bike is for you, You're aware that it is a Small aren't you?
What weight springs are on the shocks ( it should say on them if they're still "as new")
Looking at the height of that saddle, you must be reasonably tall and so you have a relative "ar$e up" angle to the handlebars so I expect you're always going to feel as if you are going over the handlebars even when you don't actually.....................<GRIN>
Yes, interesting that a 2000 has a carbon swing-arm, they had the Ally one as standard I'm pretty sure.
Tyre choice is very important for confidence so, yes, go with something that inspires you!
Downhill speed may just come with experience and confidence, so keep at it! <GRIN>
Col.
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at the risk of being hung drawn and quartered it sounds like the best thing you can do is get yourself a modern fork with about 100-120mm travel as youve got the j path blues, also if youve got one of those silly tiller length original stems swap it out for something no longer than 90mm, keep the crosslink so you can refit it when you get back to your smoother trails. im now going to run off and hide where no one can find me ;)
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at the risk of being hung drawn and quartered it sounds like the best thing you can do is get yourself a modern fork with about 100-120mm travel as youve got the j path blues, also if youve got one of those silly tiller length original stems swap it out for something no longer than 90mm, keep the crosslink so you can refit it when you get back to your smoother trails. im now going to run off and hide where no one can find me ;)
Jeff beat me to it. I had a tendency to fell like I would be pitched over the bars. The J-path would tuck the front wheel under and dive. The noleen shocks are over damped for me too, which is why it felt harsh. I went with a slider fork of 100 mm travel, actually a Noleen mega air.
For fire roads and fast sweeps I like my crosslinks, but heavy braking was terrifying.
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Thanks for the quick reply guys.
I just got back from a ride and took a pic I took today. This is the accurate seat post height I ride at now after i got the LBS to chop it down.
(http://img38.imageshack.us/img38/1681/cimg2932.jpg)
I am 5'7, and weight 130 pounds. Rear shock has a 250 lb spring, front has a 200 lb spring; which explains it... I should be riding a 175 lb up front. According to the spring charts, the SMALL MODEL of the x57 came with a 130-170 rider weight spring for the rear, but a 160-200 rider weight spring for the front! What could possibly be the reason for such a missmatch ?!?! I am considering a shorter stem, but I think i will need to ride more to decide, as the bike might be too cramped with a shorter stem than I have; or perhaps not cramped, but more modern position? Anyways, it is a 110mm with 5deg rise.
I think I am going to stick with the crosslink as long as I can. This is still so much more bike than I am rider. I am going to see how much I can get out of this platform. Thinking... If i mated a Fox RP2 to the front shock, the 8.5inch e2e one, it could make it a little more nose up, add more travel, and lighten it at the same time.. And probably introduce even more J-Path woes.
But for now, 175lb spring is the first priority.
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if you put a lighter spring on the front than whats on now then the over the bars feeling will be exaggerated as there will be a bit more sag meaning a slightly steeper head angle also when you brake downhill the lighter spring will compress quicker and further than the current one leading to more comedy over the bars antics.
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try turning the top pivot to alter the j-path.. although this will make it more sensitive to smaller bump's and will increase the pogo effect!!
check that your rear shock is properly damped as this could be throwing you over the bar's and the forks may not be to blame!
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try turning the top pivot to alter the j-path.. although this will make it more sensitive to smaller bump's and will increase the pogo effect!!
check that your rear shock is properly damped as this could be throwing you over the bar's and the forks may not be to blame!
I can do that? I don't understand, can you be more specific or point me to a howto?
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Hold the phone. Those are Crosslinks. I thought only Vectors had adjustable pivots. I will check my crosslinks tonight.
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oops!! as shovelon say's vectors did it but unsure about crosslinks come to think off it(DOH!!)..
top pivot on the fork leg could be rotated to alter path of travel i.e j-path or more of a straiight up action..
face the front of the fork and check to see if the top pivot has a hole in it..
if so one side will be a plain hole & the other side will be counter sunk....
loosening the top bolts on the fork legs allows the pivot to be turned to the desired travel path....
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Correct! Vector's DO, Crosslink's DON'T
Vectors have an adjustable J-Path movement because of an eccentrically centred Upper Pivot Axle Rod.
There is no mention of this facility in the Crosslink Manual.
Neither the upper or lower Pivot Axle rods are eccentrically centred on the Crosslink.
and there is no central access point on the Upper Link Assembly to pivot it anyway (the small grub screw on it is a Grease Port).
Your Suspension Tuning adjustments are:
Spring Rate:
Rider Weight (lbs) Spring Rate
up to 140 175
130-170 200
160-200 200
190-230 225
over 230 250
Suspension Sag:
20% of the total shock shaft stroke, or 20% of the total wheel travel
Cross-Link forks have a total shock shaft travel of 52mm which yields a total wheel travel of 76mm
suggested sag for the Cross-Link is 10mm at the shock, or 15mm at the wheel.
Preload:
Used to set the correct Sag.
NOTE: Never increase the preload on a spring past 5 full turns of the preload adjuster. If you have tightened the preload adjuster
over five full turns and are still getting too much sag, move up to the next spring rate.
Damping:
The damping on the Cross-Link EXP is not externally adjustable. This fork uses a Noleen NR-1. The NR-1 has a preset amount of rebound and compression damping which is set at the factory.
The damping on the Cross-Link CS, C and ELT is externally adjustable. These forks use Noleen NR-2 or NR-5 "Smart" shocks, The damping adjuster knob on Noleen NR-2 and Smart Shock mainly adjust rebound damping while affecting compression damping only slightly.
Col
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I've not ridden in california (yet!) so its difficult to work out what your trails are like - for me, in Scotland, 'All Mountain' riding is all we have and normal rides for me tend to average about 25 miles with 1500m of climb. The trails tend to be on hills between 100m (300ft) and 400m (1200ft) high. Our weather conditions are also much more variable and we frequently ride in rain and mud. In Scotland we have 12 different words for mountain biking mud. Trails round here are a mixture of man made but the majority are open country and very rough with rocks and other natural hazards.
our bikes tend to be a bit heavier than normal, have fatter tyres (2.25 to 2.35), slightly more laid back geometry with longer travel front forks, large disk brakes (most of our club use XT now), a few riders are using Crank Bros Joplin seat posts and a lot of riders have single pivot suspension because multi-pivots just don't last in our weather conditions.
so, to make your bike a bit more all mountain, I would:
- ditch the cross links for a set of 120mm travel Revs or Fox
- use a bigger tyre - these look dangerous for DH sections!
- use a riser bar - they are more comfy and better for control
callum
rds
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In Scotland we have 12 different words for mountain biking mud
go on then - what are they? :D
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;) we also have 23 types of rain, but one description for a good day "sort of sunny, 16'C".
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Thanks for the sag calibration Colin, the shaft calculation/measurement will be helpful as it is hard to measure sag for the fork. Was just looking at the Spring rate guide again, and noticed it is kind of wierd. They have:
Weight: Spring Rate: Suggested Spring:
up to 140: 150 NB2L-175X
130-170: 175 NB2L-200X
160-200: 200 NB2L-200X (SM, MD, LG, AM Std)
Apparently even though I should be using a spring rate of 175, They recommend the 200lb spring, the same one for heavier riders.
(http://img35.imageshack.us/img35/6549/knoxo.jpg)
Here is a pic of the place where I ride daily, It is literally 5 minutes from my place and I am loving the convienence. The climb is about 200-220 m, over 2.5 to 3 km (wild estimate) depending on how which route I want to take. The killer part is that everything is parched dry here. loose jagged Shale (ranging from gravel to cobble size), Sand, and all loose; This entire area was glaciated, so lots of varying unsorted jagged debris from erosion, and a lot of exposed bedrock, the source of such material. Back where I grew up, I was used to biking on rich packed dirt, with tons of traction, and I would intentionally steer away from anything rockey. I would brake when I reached uncomfortable sections to reduce speed so I could avoid crashing.
Over here, everything is counter intuitive from what I know. The jagged rocks scare the crap out of me but they are the only thing to offer traction on descents. When on the loose stuff, trying to brake means wipeout. The problem is that I seem to not be able to control the direciton of the bike during descent in loose stuff either; perhaps it is a lack of speed but my front tire seems to wash out super easily; the result is the feeling of lack of control for either speed or direction. Any hints on steering? I am pretty sure I am the cause, I have been trying to choose my lines to for control as much as possible.
The good news is that my tires are due to arrive soon, and I am getting a better sense of balance (my ass over the rear wheel) so I can deal with more "unavoidable" drops when im railroaded towards them while decending on a path of loose gravel. I am definatly going over my handlebars less. Also, the climbing is pretty good considering the 1.95 craptactular "muddish" tire. Anything that isn't loose, I just let the suspension handle things, and I can point and shoot seemingly. Perhaps it is just a confidence level. Hmm.I think a riser bar is definatly in order too sometime down the line, along with a shorter stem down the line (running a 110 right now). I refuse to give up on the crosslinks just yet.
Hah, and to think pro-flexes were considered "downhill" bikes. In any case, I'll take some pics of the terrain here, I had never seen anything like it untill I rode here for the first time, might be interesting for you guys.In any case, I am enjoying my bike a lot, and going to push hard to make the most of it. A TON of trails out here...
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How much tire pressure do you have in the front tire. I use 35 psi in my front, and 45 psi in the rear.
I did notice that when the J-path tucked under, the steering became very wiggly, and broke loose alot. In fact it was with the crosslinks that I lost control and had that pretty bad crash. Afterwards I played around and swaped the left leg to the right, and vise versa. That lengthened the rake a bit and was able to take corners much better under braking. This went well for a while until I blew the smartshock and I bought the Risse. But since the Risse has so much stiction, and was taking too long to become smooth, I picked up the MegaAir forks on Ebay(kinda Proflexish). Done deal, so much better that I can't go back.
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about 31psi all around. I am still experimenting with it. Was running something really high before that.
Going on another group ride today, should be good.
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Wow, a warning about this being an old thread. But I feel compelled to reply anyway.
Proflex's are New England born and bread XC race machines, They were never down hill bikes, but everyone at the time was making fire road bombing DH bikes, giving them a option of shorter travel and calling them XC FS bikes. So many people just assumed they were DH bikes because they had full suspension. But the New England heritage is why it came with mud tires. Also, you are having some issues with handling on the descents. I've had similar handling issues with my 5500, but had little problems with my old 2000. Some of this is because it was built with XC race geometry, which leans more towards climbing and technical trails than down hill handling. The first thing I recommend is taking the time to set the sag properly (10mm front and rear). I feel you might be happier with a 175lb front spring (assuming you could find one) because preload does not affect dampening rates or spring rates. All preload does is increase the amount of force needed to start the spring compressing. After it starts compressing all standard rates apply. I'm 6'2" and I use 120mm stems (although I used to use 130s, must be old age) I found a shorter stem with a higher rise pretty much eliminated that over the bars feeling I was getting from my hot rodded carbon x-links. I would seriously recommend a 100mm (same rise) and a low-rise riser bar as you are having so much success climbing. The riser bar's shape (combined with a shorter stem) should give you much better front end feel. That combined with the better tires should work just fine for you.
Well that's my 2 cents. I'm sure if I dig around more I'll see more of your updates.
Rich
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Wow, that first photo reminds me of when I was in college -- except my bike was blue and silver (instead of blue/silver/black like it is now) and it didn't have any of the fun carbon bits on it at the time.
Stock, my 756 felt incredibly front-biased (or much moreso than I was comfortable with, anyway), and the elastomer shocks didn't help that any. By the time I got to college I had already replaced the rear shock with an NR-2 (now an NR-4), but I still had the Girvin Vector fork and it sagged something terrible, because elastomer shocks just inherently suck compared to coils, and that sag caused the headtube angle to be even steeper than intended. I got very good at hanging off the back end of the bike, with the back of the saddle resting on my ribcage on either side of my sternum. (That might sound dangerous, but that's where the seat will hit anyway if the junk hits the turbine, and it saved me a little energy not having to hold myself up, so...use your discretion.) Since you have the coils front and rear, you're a step up from where I was, but that ass-out-back riding style will help you a lot on this frame no matter what fork you end up with.
For a while I lived in Tennessee and rode in the Great Smoky Mountains, where there is more than a little broken shale (a good portion of it being oil-shale, which is rather slippery), and eventually the technique I developed was this: stop at the top and choose my line beforehand, then ride down in the aforementioned position, dragging the rear brake a little bit and avoiding the front brake at all costs, and let the front wheel bounce around as it found the path of least resistance to the bottom. Don't try to steer, or if you do, use the front wheel as a rudder and don't lean the bike at all; just let the wheel knock the loose rocks out of the way and be glad for the tiny bit of steering it gives you.
If conditions are that dry and flaky, you might want to consider studded snow tires. I know it sounds counter-intuitive, since snow is kinda the opposite of bare rock, but nothing grips like tungsten studs. If you do go that route, get the ones with the studs just on the edges of the tread, not in the center, because you'll only really need them to save your ass if you start to slide-out.