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Considering that all mid-range rear shocks have a setting to limit the travel (called oil gate?): CTD or equivalent, why wouldn't most frames be designed for extremely long travel?

What is the biggest factor that influences this?

  • Is is it that a frame with compromising geometry between cross-country and downhill geometry (head tube angle, chain stay length) can't exist?
  • Is it because of the added weight?
  • Is it because many people ride cross-country and don't imagine they will ever enjoy rougher sections of the trail?
  • Maybe the price is the main reason?
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Is my question too vague or opinion-based? The core is answerable: "Controlling the frame travel is awesome, why is not everyone getting 180mm bikes?". –  Vorac Mar 10 at 14:31
    
Suppose by the same token you could ask why people buy "Softroaders" rather than hard core off road 4x4 trucks. –  mattnz Mar 10 at 22:46
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"don't imagine they will ever enjoy rougher sections of the trail" That presupposes you need long travel to enjoy rougher sections. Watch Chris Akriggs "Five" and tell me he isn't have fun climbing rougher trails on a hard-tail XC - youtube.com/… –  Snixtor Mar 11 at 3:38
    
Yes, @Snixtor I can't ride unless it's hardtail (I can, but I prefer their control in quick cuts over suspension, like ice skates on ice vs long skis in snow) and even with front shocks I like them harder. I went in and asked how to get them even tighter and the shop owner was already surprised how hard they were, maybe I ride front heavy, but they feel squishy to me... –  BillyNair Mar 13 at 11:49

2 Answers 2

up vote 6 down vote accepted

Put simply, a master of a craft will be better at it than a "jack of all trades".

A dedicated cross country race bike will be better for XC racing than an All Mountain bike. The same would be true of the dedicated downhill race bike. An All Mountain bike strikes a compromise in the middle, making it a good choice for someone who wants to do a bit of everything.

It's a bit more complex than that though, e.g. the Specialized Enduro makes different compromises to their Stumpjumper Evo. One is closer to the DH end of the spectrum, while the other is more of an XC/Trail machine. Cherouvim's answer points out some of the compromises (geometry, inefficiency, weight, flex, cost). Others include things like wheel size (XC racers might want a 29er, DH racers a 26er, and Enduro riders — who do a bit of both — might go for 27.5) and axle size (9mm QR is lighter but more flexible than 20mm thru). Which compromise you choose depends on what you want to ride!

The "do everything" bike you describe would be complex and compromised, but it does exist:

  • Bionicon specialise in such bikes. Their "Edison" model has 160mm travel in the fork. At the flick of a switch, the fork adjusts down to 80mm and the frame changes its geometry (by lengthening the shock). It's complex (it needs very special suspension to enable the adjustment) and compromised (the shock and dual crown fork are significantly heavier than dedicated XC suspension, and you have to carry the extra weight of the adjustment equipment too).

  • The Scott Genius LT offers 170mm travel in a lightweight carbon frame, along with an adjustable fork and shock. It doesn't change geometry, but offers three suspension modes (I think it limits travel). It's still too much of a compromise for a dedicated XC racer, who wants their bike to be even lighter, will probably never need all 170mm travel and probably wants 29" wheels and a front mech. It's also not far pushed enough in the other direction for the dedicated downhill racer. It's a compromise.

Additionally, many forks offer a travel adjust option (e.g. Rockshox Dual Position and Fox TALAS). They tend to be big, stiff and relatively heavy forks which work best in their longer travel mode, but can be lowered in order to aid climbing up really steep ascents. However, they're far too heavy for XC racers. If you made them light enough for XC racing, they'd be too flexible for the more gravity-focussed riders. Additionally, the adjustable spring can have an effect of the suspension's sensitivity. They're a compromise.

By the way, features such as Fox's CTD/ProPedal and Cane Creek's Climb Switch don't usually limit suspension travel. They firm up the shock's Compression (and in some cases Rebound) damping. This is to improve the pedalling efficiency of a longer-travel suspension design, in order to help with climbing, or riding on flatter, smoother terrain. They can still use all of the travel if they need to. The climb setting is a compromise.

Those compromises aren't necessarily a bad thing though: They enable me to ride my 150mm travel 30lb bike up and down some of the craziest terrain you can imagine. It'll probalby never win an XC or DH race, but it's still a fantastic bike.

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I am under the impression that most bikers don't race, hence no need for the-most-optimal-design. And while riding for fun, it is hard to foresee what will be the terrain exactly. Hence the question. Furthermore, each trail has asphalt approach, cross-country part and many have very steep and rocky sections. –  Vorac Mar 11 at 12:32
    
In other words, why wouldn't specialized bikes be the exception, and not the norm, in the mid-radnge bikes market. –  Vorac Mar 11 at 12:35
    
All-mountain/trail bikes are the norm, and XC or DH race bikes are the exception. A trail bike will compromise to make the majority of trails fun (at the expense of the extremes). How much of a compromise is up to you: If you're more into the steep rocky, rough trails, buy an Enduro (or similar: slacker, stronger, heavier and better at descending), but if you prefer covering long distances and smoother, flowy trails, buy a Camber (or similar: lighter, flickable, less strong, better at climbing). –  Olly Hodgson Mar 11 at 15:36
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"do everything well" bikes do not exist. –  cherouvim Mar 11 at 17:05
    
I doubt the statement about wheel sizes. Any references to back it up? –  mattnz Mar 11 at 19:32

Because:

  • Long travel bikes have a particular geometry which only benefits descends. Applying long travel on an XC geometry bike will create a bike which is not good for anything.
  • Long travel absorbs a lot of energy. XC riders would not like this.
  • Long travel requires stronger construction to avoid flex. This means more weight.
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Might want to add cost to the list..... –  mattnz Mar 10 at 22:44
    
How does long travel absorb energy, if it is locked out? –  Vorac Mar 11 at 8:31
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Long travel forks (180mm+) and shocks for long travel bikes (180mm+) rarely offer an option for lockout. –  cherouvim Mar 11 at 9:30
    
The other day I rode 30+ km on a 160mm upright bike with downhill tires and grew to appreciate your post and the difference a laid-forward cross-country bike gives! –  Vorac Mar 17 at 10:03

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