right now i’m on a Sem XLW 29er with 102mm cranks.
my question is how much max speed am i going to lose when i upgrade to a Profile set up?,because the shortest cranks they make are 145mm.
opinions from the speedsters like David Stone, Roger Davies and John Drommond would be really cool.Dan,Harper,rhysling,Neil,i love you too.jonny B wont see this cause he uses kill file.
thanx.
You’ll have to upgrade your rim too, since you said you have a 48 spoke one. Do you think you’ll be doing enough hopping to warrent the Profile hub? Just curious, since I know you have a muni, I thought the 29er would be your commuting machine. I just ordered a Coker online, and was having a hard time deciding between the Coker and the Sem 29er. The Sem is way better quality, but the Coker will be faster I hope. cheers… Joe (soon to be Cokerhead) in Iowa
Now I just have to get in shape to ride RAGBRAI with George.
couldnt help it, VERY OFFTOPIC!
i cant help it. i have to say when i saw “Iowa” that well pretty much everyone on this form doesnt listen to $lipknot, i must say that Iowa was their worst cd, a very offtopic topic, but i must take this chance to warn people about it.
Re: Please help=crank lenth question
I was out on some single track today with some 170’s and wishing I had my old 150’s on. All that to say that yes, you will notice a considerable difference from 102-145mm. If you’re on pavement all the time you really don’t need the leverage that you’re going to get with 145’s unless you do a lot of hills.
When I’ve ridden the 700c Sems, my choice crank size is 125mm.
(mojoe,of course i’ll need a new rim.to bad Profile does’nt make a 48 hole hub too.)
(brokenframe,this is a very important question to me.please dont muck up this thread with bad music reveiws.
now if somone can address my question on crank lenth that would be cool;)
Are the 145mm cranks hardened steel? What do they look like? Do the have an increased width at the pedal end to accommodate the drilled and tapped pedal axle holes? Can you cut off the cranks and then drill and tap them again at 102mm? Do you know someone who could? I probably could but I don’t think I have the LH 9/16 tap.
the Profile 145mm are, as far as i can see the same in appearance as the 170mm.(just shorter and dont have the threaded hole for chainrings.)
Re: Re: Please help=crank lenth question
is "considerable"like 2 or 3 mph,or 4 or 5 mph?
To my knowladge, Joe Marshal has the most practicle experience with riding larger wheels off road (which is why you’re thinking of Profile, yes? Hoppety-hoppety?) -you should drop him a line. Your current cranks are so bloody short, and you’ve got the buff spoked wheel- seems to me you are better off where you are. Have you noticed ANY axel or crank twist? Do you want to trade potentialy bent cranks for a bent rim?
-C
On second thought… since you will have to replace EVERYTHING but the tube and tyre- go for the Profile.
How much do you want for your old wheel? 
-C
Re: Re: Re: Please help=crank lenth question
I think the difference may come in the 3-4mph range, depending on your skill.
It is my opinion that when going for speed on a unicycle that there is a point where skill becomes more important than physical endurance (especially for high speed over a short distance). It takes some skill to maintain a controlled straight line without wheel wobble down road or path. Shorter crank arms make this effort a lot easier as your cadence increases.
With longer crank arms it is much more difficult to maintain a smooth cadence. You waste more time and energy concentraiting on the whole motion of the legs. The trade off is in the leverage and control that are gained with longer cranks.
happy cruising,
Re: Please help=crank lenth question
“jagur” <jagur.533fy@timelimit.unicyclist.com> wrote in message
news:jagur.533fy@timelimit.unicyclist.com…
>
> right now i’m on a Sem XLW 29er with 102mm cranks.
>
> my question is how much max speed am i going to lose when i upgrade to a
> Profile set up?,because the shortest cranks they make are 145mm.
You’ll have to move your feet 42% faster than before to go at the same
speed, if your top speed is 15 then you’ll probably drop down to 12 or so,
I’ve never quite got the same improvement with shorter cranks as the ratio
of crank lengths would suggest, but it isn’t amazingly far off.
I wouldn’t bother upgrading to profiles unless you start breaking cranks a
lot, you’ll lose a lot of speed just to have unbreakable cranks. Are you
doing big hops and drops on the big wheel, you shouldn’t bend the normal
ones with normal riding?
Joe
RE: Please help=crank lenth question
> With longer crank arms it is much more difficult to maintain a smooth
> cadence. You waste more time and energy concentraiting on the whole
> motion of the legs. The trade off is in the leverage and control that
> are gained with longer cranks.
Dustin is right, but here’s some more:
When you switch to a new crank length, it may be a gradual process of
getting used to them. I’m still getting used to riding with the 170mm cranks
on my Steve Howard prototype. But I had a great time on my last ride on it,
in Santa Cruz (except for the Poison Oak, which I did get, even after a
Tecnu shower). I’m used to 150mm cranks on my MUni. But I have sprinted with
George Peck and been passed by Kris Holm, with my 150s, and been amazed at
how they beat me. You can develop a smooth pedal stroke with longer
cranks.
Presumably you switched to the Profile setup so you wouldn’t have to keep
replacing axles. Hopefully that’s the part of the tradeoff that makes it
worth it.
On pavement, I can see using 102(?)mm cranks. I can’t imagine them being
very useful on dirt, unless it’s smooth.
When it comes to high-speed riding, it does indeed take more skill than
strength when you reach the limits of your ability. When you’re pushing your
limits, you really need to know where they are so you don’t exceed them. You
always have to leave a little left over to catch yourself if you hit a bump,
or lean too far forward. More strength and training will allow you to
increase your general speed, but you will always have to have that safety
margin. With more speed skill, the tighter you can make that margin though.
Enjoy,
John Foss, the Uni-Cyclone
jfoss@unicycling.com
“Vehicularly-Injured Sperm-Count seat: better known by it’s abbreviated
name, Viscount.” David Stone, on saddle preference
thanks folks
now let me be more clear.im not wanting to switch to Profiles because im hopping or stuff like trials.
i want to switch because its the best hub out there(i dont want to get into a DM-hub argument)and everytime i go out the garage i look back at my muni that has Profiles and i wish i could snap my fingers to magicaly switch them from wheel to wheel.
i have been jumping a little.its hard not to, at 12mph you get lift from the slightest bump.i guess what im on to is a faster form of muni.there is a definate differance from muni-ing on the 24 by 3 at 4mph compaired to absolutly blasting and scorching through the trees at 12mph.on the pavment 15mph bursts are possible.(probobly only with the 102’s though)
personal noteyes i do switch parts alot but like Jango Fett says in EPII “im just a simple man trying to make my way in the UNIverse”
I have very short ones on my 20" (which ever size comes stock on those wheels, 4" maybe?) and I find it hurts my knees if I ride any more than 30 minutes. I currently ride with 175mm cranks, and they are quite comforatble. I couldn’t see myself riding with anything shorter than say, 150’s. Am I missing out on anything? (I ride a 26" but my next wheel is gonna be a coker, or someting else larger, doesn’t anyone have long cranks on these? why not?)
Re: Re: Please help=crank lenth question
how do you get the number of 42%? is there a formula?and you spoke of a crank length ratio,is there a chart or somthing?
Re: Please help=crank lenth question
> > [i]Originally posted by Joe Marshall You’ll have to move your feet 42%
> > faster than before to go at the same speed if your top speed is 15
> > then you’ll probably drop down to 12 or so,
> > I’ve never quite got the same improvement with shorter cranks as the
> > ratio of crank lengths would suggest
>
> how do you get the number of 42%? is there a formula?and you spoke of a
> crank lenth ratio,is there a chart or somthing?
>
The circumference of the circle in which you have to turn your feet is equal
to
2 * PI * crank length
This is how far you have to move the pedals for the wheel to go round one
revolution.
So, to work out the relative foot speed required for the new cranks we take
2 * PI * old crank length
divided by
2 * PI * new crank length
which is just
old crank length divided by new crank length
multiply this by 100 if you want a percentage. For 145 / 102 we get that you
have to move the pedals 142% of the 102 cranks speed for 150 cranks, ie. 42%
extra effort.
Joe