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Will better forks help?

823 Views 14 Replies 6 Participants Last post by  ro7939, 
ro7939
Just upgraded from a very nice $2500 '07 Spec Stumpy FSR Comp to a $4400 '08 Spec Epic Carbon Expert. To say the Epic eats the Stumpy's lunch is an understatment. (Disclaimer: I admit the FSR susp sag & damping were never properly tuned & that the Epic susp is very well & finely tuned. Still I think the Epic would run circles 'round the FSR w/ identical tuning. The Epic is THAT much better.)

Second time today on my favorite trail, the Epic's unexpected & unprecendented high speed vs. the FSR is requiring me to look further & make more frquent glances ahead to avoid crashing. Things like the two rocks planted in the middle of the trail that require a quick little zig-zag between the rocks: the speed is too fast to steer through the rocks, meaning I'll probably rather steer around the rocks to the side next time.

Also, I'm climbing hills w/ very rocky terrain at speeds previously thought to be impossible. The Epic is in much higher gears on the middle chain ring vs. the FSR's smallest ring. I'm going so fast today that I'm encouraged to just keep powering even harder & fly even faster up the hills. (The terrain is rocky & rough, same as usual, but last ride, the first time on the Epic, the susp was tuned very well & the bike rode flat as a pancake over terrain that previously had the FSR upset.) So this time I figured just ride harder & faster, right?

Well, I was going so fast today, encouraged to just power as hard as I could uphill, thinking I might even keep up w/ one of the 35 year old jocks that occassionly appear (I'm age 55) that I finally upset the susp. So bad so that the front end bounced into the air, handlebars (& right elbow, thank God only minor ouchy) into the chain link fence, still no crash, but out of control, trying to get my fat butt off the seat to land, can't get my feet down, bounced off the fence, back to the left over some rocks then finally landed w/o crashing.

My analysis: at slower speeds (still flying way faster than ever on the FSR), the Epic susp is well tuned & doing a superlative job. At higher speeds, if/when the rocks are big enough, the limited 4" susp travel & preset comp damping is doing all it can, which isn't enough for the intended speeds, causing a loss of control unless speeds are minimized. (Please spank me if I'm wrongly & dramatically minimizing my lack of riding skills.)

Fork sag is perfectly set via air pressure for 1/4 the travel or 25mm (now 137 PSI; I'm 235 lbs). Shock sag is likewise perfectly set at 11mm. Also, both fork & shock rebound damping appear spot on on all but these very fast very rocky sections. The shock compression/brain setting seems spot on. (Will post all setttings upon request.)

The OEM fork is a Fox F100 RL (RL = rebound & lockout, no compression adjustment); Fox said a "$700" USD fork. Would a better fork help? I'm thinking something w/ a bit more travel (maybe 5") & adjustable compression damping to maintain control at higher speeds over rocky terrain. Must fork & shock travel always match (not the case w/ off-road motorcycles)? If yes, why exactly? As an avid motorcyclist I've always favored the more linear travel of a linear mechanical spring vs. so-called "progressive" or rising rate mechanical springs or the extreme rising rate of an air spring. (Lindemann Engineering/LE & other pro mc race susp tuners tout this philosophy, which may be all wrong on bicycles.)

Am I thinking in the right direction? To summarize, I'm thinking a fork w/:

Lockout
Improved damping
+1" travel, 5" total
Adjustable rebound
Adjustable compression
No or extremly low air PSI, again, to maintain linear rate
So-called "straight rate" or "linear rate" mechanical spring (not rising or progressive rate) set for my weight, w/ adjustable preload ramp/collar for sag

Or should I just get the OEM fork modified? What mods? Who?

What's the short list for forks in the so-called "sweet" price range, you know, 90%of the performance of the best race fork for 60%-70% of the cost?
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F
How much travel are you using on the fork now?
Your pressure sounds higher than I've heard people using for the Float fork, so, assuming you did not have the fork locked out at the time you lost control, you might try lower pressure to see if it handles any better.

Also, make sure your fork rebound is not too slow, than can and will make a fork feel harsh and handle unpredictably.
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T
im 200lbs and found fox 32's amazingly flexy. i thought it was the wheel until i did some swapping around and isolated the fork. its just flexy as hell.

this thread has 09 reba with a maxle written all over it! even the earlier qr 115mm rebas would probably work for you. my reba was very very stiff.

i dont think its reasonable that a 700 dollar fork needs a 200 dollar tune right out of the box. thats insane. it doesnt live up to its extremely high cost.
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ro7939
I will try stiffer rebound damping, but am concerned about upsetting the balance on smoother sections.

I definitely agree one might reasonably NOT expect to spend $200 to tune a "$700" fork. On the other hand, this IS often the case w/ forks except for the most costly true race type, at least w/ motorcycles anyway. The Marzocchi catridge forks on my friend's $12k MSRP Ducati Hypermotard (standard, not "S" model w/ upgraded forks) had mediocre performance till upgraded by his fork tuner. The bike's rider/owner is an ex-AMA race bike team leader, meaning lack of setup knowledge was not a factor.

Thanks for the tip concerning flex. I'm certainly not a pro at diagnosing stup but flex never occurred to me. What is MSRP for an "09 reba..maxle"? I assume that is a fork? Does it have RLC adjustments? Air, mechanical spring or both?

Thanks!
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T
bicycles are quite different than motorcycles. id take anything rockshox makes over anything fox makes, any day.. and they're cheaper. i think fox is riding their reputation VERY hard, keeping prices super inflated and providing sub par equipment. if we start demanding more for our money, or buying other brands, they might just up their game (like RS did, and like manitou is doing now)

rebas, i think they're about 500-600 bucks. a "maxle" is rockshox 20mm through axle system, very very stiff. it has adjustable low speed compression, adjustable high speed blowoff, rebound, and a really great air spring.

i moved on to a different fork/brand, but i loved my reba..
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ro7939
Sorry I forgot to mention, any fork upgrade must have clearance to accept a 27" 650b wheel w/ 2.0 or 2.3 tire. (That was a prerequisite in choosing the '08 Epic.) The radius on a 650b is about +1/2" vs. standard 26". Do the RS Reba have enough clearance? I'll check the RS website forthwith.

I suppose I should drop my fetish for linear rate mechanical spring vs. rising rate air pressure?

Thx for the tips!
jimbo
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ro7939 said:
Sorry I forgot to mention, any fork upgrade must have clearance to accept a 27" 650b wheel w/ 2.0 or 2.3 tire. (That was a prerequisite in choosing the '08 Epic.) The radius on a 650b is about +1/2" vs. standard 26". Do the RS Reba have enough clearance? I'll check the RS website forthwith.

I suppose I should drop my fetish for linear rate mechanical spring vs. rising rate air pressure?

Thx for the tips!
jimbo
Click to expand...
The RS Reba mentioned earlier, or the RS Revelation, both have dual-air springs which allow more "linearity/progressiveness" tuning than solo air or coil forks. You tune the positive spring for large bumps, then the negative spring for small-bump sensitivity.
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ro7939
fsrxc said:
The RS Reba mentioned earlier, or the RS Revelation, both have dual-air springs which allow more "linearity/progressiveness" tuning than solo air or coil forks. You tune the positive spring for large bumps, then the negative spring for small-bump sensitivity.
Click to expand...
Very interesting...in some motorcycle forks the rebound damping adjuster is found in one tube while the compression damping adjuster is found in the other.
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B
How long have you been riding?

I'm sorry, but it really sounds like what's needed is an upgrade of your skills, and not of the fork. You're on a new bike, riding at new speeds. Take the time to learn your bike and the techniques necessary for taking rocks at speed. I'm pretty safe in saying you're not out riding your gear.

The Fox damper is actually one of the best out there, even if it lacks the adjustability you're craving right now. At 235 lbs, it will be a little under damped for you though.

The Epic is an XC bike made for going fast, which is why the rear suspension is designed to be mostly locked out most of the time. If you're looking at putting a 5" travel fork on it, I think you need to re-examine the whole package first, since it goes against the specific design intent of the bike.

If you're looking for the "sweet price range", the fork you have now is right in the middle of it.
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ro7939 said:
Very interesting...in some motorcycle forks the rebound damping adjuster is found in one tube while the compression damping adjuster is found in the other.
Click to expand...
In the Fox and RockShox forks mentioned here, the compression and rebound dampers are in the same leg, and the (coil or air) spring is in the other. Some RS dual-air forks also have one positive spring in the damper leg.
I agree with b-m, the Epic is an XC-specific bike and mounting a taller fork is not suited to that bike's design.

One option is to get your Float fork custom tuned by PUSH.
But, if you are experiencing much flex like tomsmoto mentioned, then you would need a through-axle fork (15 or 20mm), like a Revelation or newer Fox.
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ro7939
bad mechanic said:
How long have you been riding?
Click to expand...
Motorcycles on pavement, club racing/track days at high speeds for thirty five+ years; but no dirt time since I was a kid (age 55 now). On MTB this, I must admit, is only my second season. In my defense I would imagine my learning curve is not that of someone completely new to two-wheel machines.

I'm sorry, but it really sounds like what's needed is an upgrade of your skills, and not of the fork. You're on a new bike, riding at new speeds. Take the time to learn your bike and the techniques necessary for taking rocks at speed. I'm pretty safe in saying you're not out riding your gear.
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Apology just as appreciated as it is unnecessary. I suggested skill being a factor in the first post. The more time has gone by since my last almost-crash the more I started to realize that I'm just not used to the speeds the Epic is capable of in the dirt. I'm acclimated to very elevated pavement speeds, but as you can imagine, no rocks (at different locations each ride), no fences separating trail boundaries, no dirt, no growth hiding the pavement, as is the case on my trail.

Your analysis above is probably spot on.

The Fox damper is actually one of the best out there, even if it lacks the adjustability you're craving right now. At 235 lbs, it will be a little under damped for you though.
Click to expand...
Your description of the fork's quality is also appreciated. Rebound damping set at 10 of 15 clicks is spot on over smooth-moderate terrain. Might you recommend setting R at max & scaling downward depending on results? If I end up w/ the Reb set at or near 15 (maximum) on the stock fork, it occurs to me that a re-valve might be recommended in order to provide a better range of Reb settings from which to choose. Your thoughts appreciated on this point especially.

The Epic is an XC bike made for going fast, which is why the rear suspension is designed to be mostly locked out most of the time. If you're looking at putting a 5" travel fork on it, I think you need to re-examine the whole package first, since it goes against the specific design intent of the bike.

If you're looking for the "sweet price range", the fork you have now is right in the middle of it.
Click to expand...
Yes, above occurred to me also & makes perfect sense. I imagine another way to put it is: the Epic is a lightweight XC that climbs like a rocket; a bike that & glides at high speeds over huge rocks is more like an AM, significantly heavier & w/ greater travel. Am I getting the right picture?

Thx for your patience.
jimbo
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ro7939 said:
Motorcycles on pavement, club racing/track days at high speeds for thirty five+ years; but no dirt time since I was a kid (age 55 now). On MTB this, I must admit, is only my second season. In my defense I would imagine my learning curve is not that of someone completely new to two-wheel machines.
Click to expand...
I've ride motorcycles myself, and while it might help a little bit, the skill set for the two is extremely different, to the point where I'd said it's not applicable.

ro7939 said:
Your description of the fork's quality is also appreciated. Rebound damping set at 10 of 15 clicks is spot on over smooth-moderate terrain. Might you recommend setting R at max & scaling downward depending on results? If I end up w/ the Reb set at or near 15 (maximum) on the stock fork, it occurs to me that a re-valve might be recommended in order to provide a better range of Reb settings from which to choose. Your thoughts appreciated on this point especially.
Click to expand...
I really think looking at a new fork is the wrong step. You haven't adjusted to what you have, and with a new one you'll just have a new fork to adjust to and a new set of tuning challenges to figure out. Ultimately, I think you're jumping quite a bit ahead of yourself talking about getting forks revalved.

My suggestion would be to replace the stock 7.5w damper side fork oil with a 10w oil. This will increase the fork's damping across the board, and might suite you a little better. It will, however, make the fork less plush.

Again, the Fox you have on there really does have an excellent damper in it, with both high and low speed rebound and compression circuits and a good range of adjustability.

ro7939 said:
Yes, above occurred to me also & makes perfect sense. I imagine another way to put it is: the Epic is a lightweight XC that climbs like a rocket; a bike that & glides at high speeds over huge rocks is more like an AM, significantly heavier & w/ greater travel. Am I getting the right picture?
Click to expand...
You're getting the picture exactly, though there are plenty of trail bikes which climb well and won't be too heavy.
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donoman
I ride an Epic with an old Manitou SX-Ti 80mm front fork and it's fine. I don't know how fast you were going, but I haven't been able to really get bent out of shape on my Epic due to lack of travel.

Every suspension system will bottom-out on a big enough bump. Hopefully when you bottom out your body and the bars are in a good position to recover :)
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The rebound tuning range of the Fox forks is so ridiculously broad that my money is on your not having found the sweet spot yet. I'm with Bad Mechanic, just spend some more time tuning what you have for a while.

A 5" fork would definitely upset the climbing awesomeness of the Epic. You'd kind of be turning it into your FSR, you know? Whatever you do, I'd still hang out in 100mm land just to keep the geometry as designed.
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ro7939
Thanks for all the input.

I sold the Epic & ordered an all-new for 2010 Haro Sonix 650b.

After getting as familiar as possible w/ the Epic & getting the suspension tuned as well as could be, it turns out I needed the extra suspension & durability of my heavier Stumpjumper FSR Comp (120mm front/rear). The Bonneville Shoreline trail I love has too many too-large rocks. On smoother terrain the Epic is absolutely faster & more fun; the bumpier the trail the more time I was in the air on the Epic rather than being planted on the ground gliding over the rocks feeling confident (on the SJ).

The buyer of my Epic intends to ride the red rock desert of Moab/So. Utah, for which I'm guessing it would be just about perfect. Rest assured the higher elevations of north Utah, at least the trails I frequent, are likely not nearly as smooth as Moab.

My other choice was the all new for 2010 Jamis SixFifty B1 &/or B2, which seem closer to an AM bike rather than the XC Haro.
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