Zinn Bicycle's: Sighting

[Too Tall]

At least a few folks on the forum have some experience with Zinn's bicyles and theories on cranks. Because I'm a tall fellah I've followed Len's products with glee. It's a wonderul thing to have someone with his skill, sincerity and marketing saavy dedicated to making products for very tall people.

Yesterday I saw my first Zinn bicycle. The rider was almost exactly my same height...hehe a little shorter (wink wink)...and very nearly same inseam. I was shocked at the BB height. The rider could not recite the bikes build numbers however placing the bikes crank to crank the diff. was close to an inch. His cranks were 220's and a really snazzy looking billet affair...really nice work. The frame looked to be a skillfully done basic tig'd. The bike was a semi-compact and proportions were really well done considering the very high BB and long levers.

OK, so here is my question / observation: After talking to the rider for a few mins. before this very climbie hammerfest we set out. I put my self squarely behind the guy so I can check out everything. The rider is strong and the bike drives VERY nicely, everything looks square etc. BUT I just can't figure you why this riders hips are moving so much. Clearly he has the right saddle height and saddle setback appears spot on, reach dead on NICE FIT!!! However, there is no getting around the fact of his hips moving way too much. The guy was spinning nicely, not mashing and damn fine pedaling otherwise....so I'm puzzled.

Thoughts?

*This is NOT a flame or criticism. I'm looking for anwers.

[Smiley]

I saw this same bike last memorial day weekend at the 25 mile rest stop . Really Tall bike . I did not see the guy riding the bike , nor did I notice the crank lengths . This was a greenish color frame right ?

[ergott]

I put my self squarely behind the guy so I can check out everything.

What the hell were you checking out on this guy???
Did you like what you saw? ;)

[Kevan]

usually, or most often, means the saddle's too high, right? Well, based on your review of the sitcheeashun, assuming the perch is set right 'n level, I'm thinking the long cranks might be at fault.

Or... the guy's some kinda freak of nature and has a displaced hip, sorta like what the Cheetah deals with romping the Serengeti .

That would help splain his strength and speed, wouldn't it?

[Andreu]

does he have a problem with his lower back. I have, from time to time, problems with my lower back causing stiffness or inflammation which causes me to rock (ever so slightly) in a horizontal plane - this occurs sometimes when I am in no pain whatsoever.
Not sure this helps but this person may be in no pain but have some lower back problem (congenital or otherwise)?
just a thought....I have seen this on other riders who have issues with their backs. It is mostly miniscule and can hardly be detected.
A

[David Kirk]

If the saddle was the correct height then I doubt it's equipment related. Sounds like a technique issue.

Dave

[Too Tall]

He was fairly limber. If it were not for the hips jacking around I'd say he looked like a decent rider. Dang, if anyone in the area knows this guy let me know. He was on the Sunday Chester Gap ride ala PPTC. Nice chap, I'd like to help straighten things out. Dave's right it could be technique. I want to ride is bike too hmmmm. It's so wierd that I've got to know more.

Dave, how's the crank situation? Are you adapted now? You might know, what would the BB drop be on a frame such as this gents be?

Smileyman it was not the green one...that makes two.

[David Kirk]

Mr Too -

I love my 190's and can't imagine going back to 180's. It took a few weeks to forget about them. Now they feel totally natural and my spin is back where it used to be at about 88 rpm's.

On my personal bike ( not a crit bike) I'm running 7cm of drop with the 190's and new Time pedals. It's pretty easy to do the reverse math with the drop to crank length issue. Make the crank 1cm longer - raise the BB 1cm. So with 220's the drop would be about 3 to 4 cm. Keep in mind this has no effect on the height of the riders center of mass. The foot is kept a constant distance from the ground.

The hard part in dealing with super long cranks, from a design standpoint, is toe overlap. it's not just for smaller folks anymore!

Dave

[Len J]

Too Tall:

My (very uninformed) opinion is that it relates to seat height. I had a friend who put on longer cranks and didn't change his seat height and had the exact same problem. Many people set their seat height relative to the BB, no the pedal, so when they lengthen their cranks, they don't change their seat height.

Just a thought.

Len

[William]

Mr Too -

I love my 190's and can't imagine going back to 180's. It took a few weeks to forget about them. Now they feel totally natural and my spin is back where it used to be at about 88 rpm's.


Dave

Hi Dave,

How does your climbing technique/power application feel with the 190"s? Any changes? Better, worse, same?

I know when I went from 175's to 180's I felt that I could apply a little more torque and stay on top of the gear easier. I would imagine that at my height a move from 180's to 190+ would possibly be beneficial.

Thanks,

William

[David Kirk]

Hi William,

Yep I notice I can climb stuff I used to use a 21 tooth cog on in a 19 now at the same rpm's. So yes I'm faster. Frankly the more important thing to me was/is the more relaxed and natural feeling I have. I used to feel a bit like it was a kids bike and I had to really be on top of my form now it's more relaxed and easier..........which for me tranlates into more fun.

What's your inseam?

Dave

[William]

Hi William,

Yep I notice I can climb stuff I used to use a 21 tooth cog on in a 19 now at the same rpm's. So yes I'm faster. Frankly the more important thing to me was/is the more relaxed and natural feeling I have. I used to feel a bit like it was a kids bike and I had to really be on top of my form now it's more relaxed and easier..........which for me tranlates into more fun.

What's your inseam?

Dave

About 97.5 cm (as I remember it).

I like your explanation of "relaxed & natural feeling", a better way of saying what I felt going to longer cranks.

William

[David Kirk]

Yo-

I think that they are worth a try..........but frankly most anything above 180's will most likely need a frame built with the cranks in mind. It becomes a big experiment with "project creep". If you have an older frame with 7cm of drop you might be OK with 190's depending on how you use the bike. You'd need to lower the saddle the correct amount and lower the bars the same amount so you are riding a chopper.

Let me know if you have any questions.

Dave

[Too Tall]

Now I'm determined to find this guy....hmmm. I really want to ride this bike.

Haha, I REALLY need to get on staff with PEZ so I can do some product testing. With 3 yrs. of SRM data I'm real sure I can give meaningful "Tall" feedback. :cool:

The torque thing is misunderstood. Shorter cranks have greater torque. Infact the best sprinter in our region uses 175's and he is an ex-pro ball player who is 6'6' or 6'7'. He also has a HUGE sprint so the greater torque is justly applied.

Dave's easy riding approach totally makes sense to me and your comment about not having to be ontop your game makes intuitive sense. Who said "horses for courses?". How might your cranks work for racing?

Is this a case of the right tool for the job?

Also for Davedewd, yep I get the ctr. of gravity deal for a rider and won't the bike have a very different feel than an 7-8 drop bike as the low portion of mass traveling near / through the fork's trail is considerably higher? Did I say that? erk. So, how can a high BB bike handle well esp. out of the saddle and crit corners?

[William]

Yo-

I think that they are worth a try..........but frankly most anything above 180's will most likely need a frame built with the cranks in mind. It becomes a big experiment with "project creep". If you have an older frame with 7cm of drop you might be OK with 190's depending on how you use the bike. You'd need to lower the saddle the correct amount and lower the bars the same amount so you are riding a chopper.

Let me know if you have any questions.

Dave

Thanks Dave. :cool:

The spec sheet for my frame gives BB Height as: 27.00 cm/10.63 in.

William

[David Kirk]

William -

It sounds like your bike has 7cm of drop. What brand bike is it? If it does have 7cm of drop it might work out OK for you with the long cranks. It does for me for the way I ride. I wouldn't race a bike with the pedals this close to the dirt. For my riding (long climbs and long, fast descents with little need to pedal around corners) it works great. The only sharp corner I make is in and out of my driveway.

Too Tall -

I would race a bike with these cranks.....I might have a slightly higher BB though.....see above.

Your center of mass (COM) question is an interesting one that has two answers. While seated the COM is regulated by the distance your foot is from the ground. With longer cranks and equally less BB drop the COM stays the same. When standing the COM is determined by the distance the BB is from the ground. Think of standing with the cranks level.........you will be higher off the floor with less drop.........Yet while out of the saddle with your foot is at the bottom of the stroke your COM is the same. Tricky eh?

It stopped raining.......I'm outta here.

Dave

[jerk]

shorter cranks for short quick efforts..... twisty crits, match sprint, etc. etc.

longer cranks for steady prolonged efforts.....long seated climbs, time-trialing etc.

his hips looked rocking and stupid because his cranks are stupid long. think about it.

jerk

p.s. the jerk does not change his saddle height from the center of the bb to the top of the saddle when different crank lengths are used. don't know why, it just doesn't feel right when he does.

[TimD]

[No offense intended by the title, btw!!!]

Among the useful things I learned during my undergraduate electrical engineering education is that torque can be expressed in units of foot-pounds. An informal definition of torque is the twisting force about an axle resulting from a force F applied perpendicular to a lever arm connecting to the axle, at a distance d from the center of the axle.

A force of 1 lb applied at a distance of 2 feet from the axle will generate 2 ft-lb of torque about the axle, whereas a force of 1 lb applied at a distance of 1 foot from the axle will generate 1 ft-lb of torque.

Power and torque are linearly related: Power = Torque * 2 pi * RPM.

It follows that a rider who can apply a given force to a 220mm crank arm will indeed be generating more torque than if they were riding a 175mm crank. However, for a given power output they will be turning the longer crank less quickly.

A gain in efficiency might or might not be available by changing the angular relationship between the crank arm and the driver (e.g., the rider's quad) or by changing the "torque curve", e.g., the RPM at which the rider generated a particular amount of power, assuming that that curve is not flat.

TimD

[scrooge]

Hey TT and all interested:
You have an open invitation to try out my bike with my 200s if you're ever in Michigan--once the cranks actually get here (apparently Zinn's plater is quite backed up--they're already a good month late and aren't expected for a few weeks). Some day I'll get a chance to ride my new bike :crap:
As for the hip rocking--I can't imagine that it is a automatic by-product of the long cranks. I have no reason for saying this other than that Mr. Zinn seems to know a thing or two about bikes/riding bikes, and I'm assuming that he practices what he preaches and rides these long cranks too (he's 6'6") and wouldn't do so if he had to rock back and forth to do so.

PS thanks for giving me another opportunity to lament the fact that I'm still waiting to get the new ride set up! I always apreciate having the opportunity to moan about such things. :D

[Needs Help]

Torque:

Simply put, the same force applied to longer cranks results in more torque.

[scrooge]

Lest we forget--torque isn't the only issue here (though it is hopefully an added benefit). For bigger boys such as myself, comfort matters too. For me, turning 175s (I've never had 180s--I'm too cheap!) just feels wrong. It's "unnatural" for me to have my legs do such little circles. Weather or not having cranks an inch longer will make that feel better or not, I can't say just yet...I'll report back when I can give a more informed opinion. :beer:

[CarlosContreros]

WOW!
You guys have me thinking I should lengthen my arms(172.5)
considering I have a 94.7 PBH.

Living in Florida I'm not really concerned about climbing...but..
I live to sprint!
Would longer cranks help with my sprinting?...what I took from the
jerk's post is that shorter cranks are best for hard, short efforts..
does this include sprints??

Another thought...my dream is still 40K in an hour..longer arms
might help me to acheive that!
Maybe someday 177.5's and they should work with my Merckx's
bottom-bracket height(26.3).

HEY SMART BIKE-TYPES!!............Do you then move the
saddle forward to maintain whatever type of "knee-over-spindle"
as you increase your crank length?????

[William]

William -

It sounds like your bike has 7cm of drop. What brand bike is it? If it does have 7cm of drop it might work out OK for you with the long cranks. It does for me for the way I ride. I wouldn't race a bike with the pedals this close to the dirt. For my riding (long climbs and long, fast descents with little need to pedal around corners) it works great. The only sharp corner I make is in and out of my driveway....

It stopped raining.......I'm outta here.

Dave

Hi Dave,

Actually it's a Serotta. I received two customs back in 94/95. One built by you, the other by Kelly (according to the spec sheets). I've been kicking around the idea of trying longer cranks for a while now. Like you said, I wouldn't try racing crits with them on.....though I've never had a problem riding 180's in tight crit courses....190+ is a different ballpark.

William

[Fixed]

shorter cranks for short quick efforts..... twisty crits, match sprint, etc. etc.

longer cranks for steady prolonged efforts.....long seated climbs, time-trialing etc.

his hips looked rocking and stupid because his cranks are stupid long. think about it.

jerk

p.s. the jerk does not change his saddle height from the center of the bb to the top of the saddle when different crank lengths are used. don't know why, it just doesn't feel right when he does.
This guy know 's his stuff if you want to sprint go short.I don't know much about bike racing I am just a bike messenger most of us use 165 cranks and short sprinting repeats are what we do all day. Cheers

[Too Tall]

TimD - Thanks for that, it appears a case of "what I ment" vs "what I said". Shorter cranks require more force for the given power input thus making for a much narrower peak powerband and in the case of a rider layin' into the cranks at fairly narrow rpm range during peak power output this makes for a BETTER application to have shorter cranks. I'm asking, not telling...this is a very VERY interesting subject and I draw much from practical applications over the yrs. as do we all. You won't find alot of Mtn. bikers running 165s or big time sprinters with 190's, it's not chance.

Senor' - Enlighten me man. Rubber biscuit.
I suspect all sorts of things incl. this is a case of a guy who might have an unusually long lower leg and he's got an issue but I can't be sure without a second look.

[Len J]

how do I decide what length crank makes sense for me?

I'm 6'0" and currently run 172.5's........should I be running longer?

The majority of my riding is long distance.

Thanks for any input.

Len

[scrooge]

how do I decide what length crank makes sense for me?

I'm 6'0" and currently run 172.5's........should I be running longer?

The majority of my riding is long distance.

Thanks for any input.

Len

If you want to follow Zinn's formula (which most taller chaps don't because it leads to the previously mentioned really long cranks) you take your Pubic Bone Height times .21 (or you measure your femure from hip bone to knee bone)

[Len J]

If you want to follow Zinn's formula (which most taller chaps don't because it leads to the previously mentioned really long cranks) you take your Pubic Bone Height times .21 (or you measure your femure from hip bone to knee bone)

So PBH = 88 X .21 = .1845 Does this mean I should have 184.5 mm cranks?

Len

[scrooge]

Or there abouts. That's the theory anyway.

[William]

Hmm,

Roughly 200's for me?


William :)

[theprep]

Check out this link. It has data from some of the cycling greats (Bernard Hinault,Jacques Anquetil, Eddy Merckx, Miguel Indurain) with respect to crank lengths.

http://www.cranklength.info/cranks.htm#how

[Too Tall]

Here is another:
the rule of thumb is: 20.8% of inseam, +5mm for long femurs, -5mm for short femurs. also considered is ankling and toes pointing down while pedaling

Sorry, this is far from over. It's a way intersting topic.

[Needs Help]

The torque thing is misunderstood. Shorter cranks have greater torque.
Cranks have a weight, a length, and a color. They do not have torque. Force applied to a crank creates torque. If you apply the same amount of force to a longer crank, you create more torque.

However, if a sprinter is able to apply greater force to a shorter crank, they can create more torque than a weaker rider pedaling a longer crank.

[Too Tall]

NH - compare apples. One rider using same force and two diff. cranks. Push down with 1000watts in a 50X13. Which bike travels further, faster both?

[shaq-d]

NH - compare apples. One rider using same force and two diff. cranks. Push down with 1000watts in a 50X13. Which bike travels further, faster both?

watts IS torque. (or actually, watts is power, or watts is torque over time). you don't "push down with 1000 watts in a 50x13" and ask which travels faster, longer cranks or shorter cranks. the question doesn't make sense, because the OUTPUT of what you turn IS torque/watts.

your question should be, given the same FORCE (measured in pounds, or newton's, etc.) in a 50x13, which is faster, longer cranks or shorter cranks. the answer is the longer cranks, because the lnoger cranks generate more watts/torque.

sd

[Too Tall]

Got it, terminology can get in the way can't it ;) Why is it that sprinters prefer shorter cranks?

[William]

Got it, terminology can get in the way can't it ;) Why is it that sprinters prefer shorter cranks?

Pseudo sprinters prefer longer cranks.....of the 180 variety. ;)


William