Good Location for All mountain riding?

[syadasti]

Riding RV I raised a seatpost to the max height for efficient climbing and then realized cannot shift weight effectively anymore... stop and drop it... that is such distraction... so I gonna try an adjustable seatpost very soon

I have a friend who rides his XC bike at full extension and rides down terrain steep enough to challenge the average gravity rider on a DH rig..

Also lots of people are use to riding dropped also, see Stowe scene, and many are still plenty fast.

An adjustable seatpost is yet another cycling industry crutch/distraction/toy/fad, especially around here with such short climbs/descents. You spend too much time putting it up and down rendering these posts unnecessary. I tried one for a while and went back to a compromise height on a standard seatpost (which is lighter and stronger if you are so XC oriented).

don here had one too and he doesn't use one any more either I think?

The places it would really make a difference, steep shuttled worthy terrain, trial-like moves, or occasional obstacle require more than 3-4" of adjustment almost all of them offer (I think rase is the only to offer significant height range adjustment).

The rapid adjust seatpost comes and goes, its nothing new - see hite-rite (and later there was on that looked like a parallelogram suspension post but it was for height adjustment, can't find it right now):

Even some people out West don't like them much:

Yes I think most people including myself will admit that it's a little more comfortable with the seat out of the way but for the constant up and down of a lot of fun descents, it's not worth screwing around with a quick release OR an adjustable seatpost when the differences really aren't that great in how it affects bike handling. And that's obviously subjective. Just because YOU like it doesn't mean it's a necessity for everyone riding similar terrain.

 

[alex_k]

Ok, it might be a gimmick like fork U-Turn and lock-out or 650b wheels...

At least half of all bikes comes with fork lockout and some people like but I found that useful only for SS.

My point is if you want and can afford - try it

 

[goldsbar]

The seatpost hasn't been a gimmick in my experience. The Joplin has a remote on the handlebars which makes adjustments very easy. It becomes second nature after a few rides and I constantly adjust up and down. Ajdusting a quick release seatpost is a major PITA and interupts the ride. Going behind the seatpost is not the same - your torso is still limited by seat height. I'm reminded of this everytime I ride my cross bike offroad.

Overpriced? Sure. Heavy? Yes. Another thing to maintain? Yup.

Increased fun factor, cornering capability, etc.? Definetely IMO.

 

[idbrian]

http://nz.answers.yahoo.com/question/index?qid=20071220060219AAkNDTU

Thanks for that link. The concept isn't too hard to understand either.

Do the seat angles typically follow the same guidelines?

 

[clarkenstein]

Thanks for that link. The concept isn't too hard to understand either.

Do the seat angles typically follow the same guidelines?

pretty much... a good x/c seat tube angle (IMHO) is somewhere around the 73 degree mark... i think the general range you'll see is 71 degrees to 75 degrees on the seat tube angle - 75 being for your x/c race bike and 71 being for your more freeride oriented bike. if you combine the slack head angle and seat angle on a frame you can (generally) lower center of gravity for a more 'going down the hill' oriented bike, while having both a steep head angle and seat angle will (generally) give you better power transfer and you'll have much more responsive (yet twitchier in the rough stuff) handling.

 

[Bob W]

Whilte you are reading stuff...

Look into the effect that BB height has on a bike. Another very important factor that nobody discusses or thinks about. Goes along with the HA and ST angle...all plays together.

 

[goldsbar]

and wheelbase...

 

[don]

don here had one too and he doesn't use one any more either I think?

yeah, I actually have Gravity Dropper sitting in my workshop and hasn't been used in a few years. It's one of those things that it sounds like it would work great and be so nice to have but for me the extra complexity and weight wasn't worth it.

I found that if I'm going to ride something with the seat slammed - like a drop or jump - that I'll typically have a small sesh and flipping the QR isn't that big of a deal as I'm stopping the trail flow anyway.

Like syadasti said, there are some locals (or I should say used to be), that rode mostly singlespeed bike with slammed seats all the time. Going uphill didn't matter as they were standing anyway. But that crew did a lot of very nutty things including the level of riding.

I think goldsbar hit it on the head:

Overpriced? Sure. Heavy? Yes. Another thing to maintain? Yup.

Increased fun factor, cornering capability, etc.? Definetely IMO.

If they fit your style of riding and you don't mind an extra cable and the weight then they are certainly worth it.

 

[don]

Is there a synopsis of this somewhere? I would like to learn without going into too much details or having to read a book.

http://forums.mtbr.com/forumdisplay.php?f=142

I'd read a bit on this link - it's the mtbr.com Frame Building forum.

I'll try a quicky synopsis based soley on my knowledge from riding different frames and having a couple of protoype DJ frames built. If anyone wants to add/correct me please feel free.

HT Angle: like clarkenstein said - can be 60-75 degrees. Higher number quicker/twitchier bike. Lower number slower feeling ride. A steeper HT angle can be a factor for foot and tire rub on larger sized wheels.

ST Angle: May not be that important depending on application. Usually they will fall in the 70-75 deg range. But...Some bikes like the Evil Imperial had a wicked slack ST angle - gets the seat out of the way or help "solve" some issue with a suspension design. Slacker can be tricky as the higher the post the more the bike might feel like you are sitting over the rear tire.

BB Height: Lower will be more stable, higher will give a more clearance and make the bike twitchier. Can also be refered to as BB drop based off the horizontal line between the front and rear axles. Usually around 11-13" from a level ground to the middle of the BB.

TopTube length: Can be True TT length or Effective TT length. Generally used for fit although HT and ST angles can throw it off. Some people feel that the downtube measurement or the length from the center of the HT to the center of the BB is more acurate - it probably is but it's very hard to measure acurately

Chainstay length: Shorter is quicker and easier for things like tight turns and getting the front wheel off the ground to hop logs and obstacles. Longer is more stable but harder to move the backend around like in tight turns. A short chainstay can show issues on steep climbs - the front wheel will want to loop out.

There are even a few smaller factors that make a frame ride like it does. Material, tubing thinkness, bracing. And this is just for hardtails. Once you get into a suspension frame a bunch of other things add into the mix.

If you are still interested, write down the specs for your bike(s) and compare them to other bikes you like and or have ridden. I keep an MS Excel file with many different specs from frames I've been interested in buying over the years.

Good geometry comes down to preference and riding style too - I like short chainstays, higher BBs, a steeper HT angle, and a middle ST angle.

 

[idbrian]

Maybe it is something that comes with many years of riding but i don't think i could really tell much a difference from trying out different bikes that are of similar size and travel.


Based on suggestions on here i made some changes to my Trance so i could do techy descents better. I've got a longer travel fork on it, a much shorter Stem and am still on the lookout for a Zero setback seatpost. The differences have been great, to the point where i decided to put more money into upkeeping the Trance instead of getting a new frame. I've been riding the bike for a few years without knowing it was an awkward fit.

 

[clarkenstein]

Based on suggestions on here i made some changes to my Trance so i could do techy descents better. I've got a longer travel fork on it, a much shorter Stem and am still on the lookout for a Zero setback seatpost. The differences have been great, to the point where i decided to put more money into upkeeping the Trance instead of getting a new frame. I've been riding the bike for a few years without knowing it was an awkward fit.

with mods like that, it sounds like you probably now have a slacker HA (a longer fork will slack the head angle), and the short stem will allow you to get your weight back - both are good moves for helping out on techy decents. that's great that you got the bike working for you instead of having to go completely new.