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An inch behind KOPS: Anybody doing it?  

post #1 of 12
Thread Starter 
Just picked up a new custom hardtail frame and it looks like something went way wrong with the frame
tube/angle calculation.

The best I can get with the saddle all the way forward is my knee a good inch in back of the
pedal spindle.

I've ridden in front of KOPS - on a too-short frame. Main effect seemed to be to put my butt too far
back on the saddle as my bod found KOPS on it's own while riding.

But this is the first time I've had a too-long frame and been behind KOPS - seems like the narrowing
of the saddle as one moves forward would mitigate against my bod finding KOPS on it's own.

The reason I'm trolling for someobody who rides behind KOPS is that I'd like to think this isn't
a total loss and I'm going to be able to ride it without the prospect of repetitive-use injury
to my knees.

But I wouldn't want to find out the hard way....

Comments?
-----------------------
Pete Cresswell
post #2 of 12

Re: An inch behind KOPS: Anybody doing it?

"(Pete Cresswell)" <x@y.z> wrote:

>Just picked up a new custom hardtail frame and it looks like something went way wrong with the
>frame tube/angle calculation.
>
>The best I can get with the saddle all the way forward is my knee a good inch in back of the
>pedal spindle.
>
>I've ridden in front of KOPS - on a too-short frame. Main effect seemed to be to put my butt too
>far back on the saddle as my bod found KOPS on it's own while riding.
>
>But this is the first time I've had a too-long frame and been behind KOPS - seems like the
>narrowing of the saddle as one moves forward would mitigate against my bod finding KOPS on
>it's own.
>
>The reason I'm trolling for someobody who rides behind KOPS is that I'd like to think this isn't
>a total loss and I'm going to be able to ride it without the prospect of repetitive-use injury to
>my knees.
>
>But I wouldn't want to find out the hard way....

FWIW, I tend to ride further back (relative to KOPS) on my MTB - I do more climbing and it helps me
get my glutes into the game. It does tend to make my front end a bit lighter though, and I have to
be careful not to wash out the front tire in sandy areas (and there are a LOT of those in Arizona).

BTW, are you measuring the KOPS while in your normal riding position? If not, you may find that the
shock will compress enough to move your knee considerably further forward (though I doubt an inch).

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
post #3 of 12

Re: An inch behind KOPS: Anybody doing it?

"(Pete Cresswell)" <x@y.z> wrote in message
news:<uc7m2v8aqjmvh86entque5o4ssn2hkvuu0@4ax.com>... <snip>
> The reason I'm trolling for someobody who rides behind KOPS is that I'd like to think this isn't
> a total loss and I'm going to be able to ride it without the prospect of repetitive-use injury to
> my knees.
>
> But I wouldn't want to find out the hard way....
>
> Comments?

I've ridden for 12 years and tens of thousands of miles with my knees well behind KOPS. My knees are
quite happy.

The rest of me is pretty happy, too- I ride recumbents. :-)

I'd say that you should adjust the seat in the middle of the rails; put on a tall, short reach stem;
and ride the heck out of the bike.

Jeff

Jeff
post #4 of 12

Re: An inch behind KOPS: Anybody doing it?

I'm only about 1cm behind KOPS and don't have any problems.

Did you do the measurement yourself? If so, have someone else try while you just sit on the bike.
I've noticed that when I'm fitting friends, that if they're looking at what I'm doing, it affects
the measurements.

Mike

"(Pete Cresswell)" <x@y.z> wrote in message news:uc7m2v8aqjmvh86entque5o4ssn2hkvuu0@4ax.com...
> Just picked up a new custom hardtail frame and it looks like something
went way
> wrong with the frame tube/angle calculation.
>
> The best I can get with the saddle all the way forward is my knee a good
inch in
> back of the pedal spindle.
>
> I've ridden in front of KOPS - on a too-short frame. Main effect seemed
to be
> to put my butt too far back on the saddle as my bod found KOPS on it's own
while
> riding.
>
> But this is the first time I've had a too-long frame and been behind
KOPS -
> seems like the narrowing of the saddle as one moves forward would mitigate against my bod finding
> KOPS on it's own.
>
> The reason I'm trolling for someobody who rides behind KOPS is that I'd
like to
> think this isn't a total loss and I'm going to be able to ride it without
the
> prospect of repetitive-use injury to my knees.
>
> But I wouldn't want to find out the hard way....
>
> Comments?
> -----------------------
> Pete Cresswell
post #5 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

RE/
>BTW, are you measuring the KOPS while in your normal riding position? If not, you may find that the
>shock will compress enough to move your knee considerably further forward (though I doubt an inch).

I'm not sure. I'm measuring it the same way as on my 'real' bike, though: I get on the bike, put my
butt where the indents are on the saddle, set a crank parallel to the ground, and drop the plumb bob
with the line against my kneecap.

Right or wrong, the other bike seems to work - no knee problems and, to me at least, a comfortable
riding position - albiet a very light front end from the setback seatpost.

My knees definately tell me about it when I do 20-30 miles on my utility bike - on which the knees
are forward of KOPS.

OTOH, I just heard from somebody else that being behind KOPS doesn't seem to cause injury - in fact
this person seemed to think that a lot of professional road riders ride that way anyhow.

That being the case, I think I'll try to work with this thing for awhile and see if I can live with
it. KOPS isn't a matter of principle - I'm just looking for something that works.

Also, this bike is intended just as a "go anywhere" road bike and a travel bike (I got it with the
B&S couplings). If things don't work out, I may be throwing myself on you guy's mercy....which is
probably what I should have done in the first place...depending on a cost comparison between
re-making this one "right" and going titanium. The second time around on this end should have a 100%
chance of success given that we have a concrete reference point - so that part of the decision is
probably a wash.
-----------------------
Pete Cresswell
post #6 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

With 5 3/4 inches of seatpost extension to play with, I'm thinking a viable workaround (instead of
junking the frame) would be brazing together a faux seatpost/seat tube: something that sticks down
into the seat tube on the bottom side and presents an offset section of seat tube to stick the real
seatpost into on the top side. The real seatpost could be trimmed so it doesn't hit the top tube.

Dunno how much overlap is necessary when sticking one tube into another, but I'd guess the amount
isn't that much, is well known, relates to the diameter of the tubes in question, and is a lot less
than 5 3/4 inches.

Not real elegant, but seems like it would get the saddle up where my butt is without dropping a
bundle on another frame...
-----------------------
Pete Cresswell
post #7 of 12

Re: An inch behind KOPS: Anybody doing it?

I don't see mention of whether your seatpost has any setback. If it does, as most do, you might find
your answer there. There's quite a range of seatposts on the market, some with no setback and some
made for negative setback (intended for triathletes, mainly). Control Tech used to make reversible
ones which were quite common; you might find one of those lying about or maybe on ebay. From a
typical setback post to an inline post will get you close to an inch right there, and the tri or
reversible posts even more. Saddles also vary a fair amount in how much fore-aft range of adjustment
the rails allow. I'd go for either of the above before a mudge like you're talking about.

SB

"(Pete Cresswell)" <x@y.z> wrote in message news:a4br2vg9lgv7h9prbm9qh216p62jn9h7m4@4ax.com...
> With 5 3/4 inches of seatpost extension to play with, I'm thinking a
viable
> workaround (instead of junking the frame) would be brazing together a faux seatpost/seat tube:
> something that sticks down into the seat tube on the
bottom
> side and presents an offset section of seat tube to stick the real
seatpost into
> on the top side. The real seatpost could be trimmed so it doesn't hit
the top
> tube.
>
> Dunno how much overlap is necessary when sticking one tube into another,
but I'd
> guess the amount isn't that much, is well known, relates to the diameter
of the
> tubes in question, and is a lot less than 5 3/4 inches.
>
> Not real elegant, but seems like it would get the saddle up where my butt
is
> without dropping a bundle on another frame...
> -----------------------
> Pete Cresswell
post #8 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

RE/
>It can cause injury, but not where you may think. If you are not pushing "down" when you pedal your
>butt will move forward and back on the seat

I'm already noticing that - lots of sliding back-and-forth. I'm also thinking that an unexpected big
bump in the "forth" position could ruin my whole day....
-----------------------
Pete Cresswell
post #9 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

RE/
>Have you lowered the saddle to compensate for it being farther back?

Never thought about that.

Sounds like when I do the knee straight, heel on pedal thing, the pedal needs to be cocked a little
forwards of straight down.
-----------------------
Pete Cresswell
post #10 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

RE/
>From a typical setback post to an inline post will get you close to an inch right there, and
>the tri or reversible posts even more. Saddles also vary a fair amount in how much fore-aft
>range of adjustment the rails allow. I'd go for either of the above before a mudge like you're
>talking about.

I'm wedded to the Brooks B-17.

As far as seatposts go, the ThudBuster I want to use on this bike (it's a hardtail) looks to have
about a half-inch inherant setback in it. But that's non-negotiable: my tender tush just doesn't
thrive on solid-rail saddles.

I *could* go to the four-wire Brooks B-72, and have done so in the past - but that's only going to
pick up that half inch.

Considering that when I config this thing for my Rohloff hub and tension the chain via the eccentric
BB we're going to add another half-to-three-quarters inch I think I'm looking at wanting about two
inches of forward shift (given that may be a little too much, but now the saddle is all the way
forward on it's rails - so there'll be some room for adjustment there...
-----------------------
Pete Cresswell
post #11 of 12
Thread Starter 

Re: An inch behind KOPS: Anybody doing it?

RE/
>The Profile Fast Forward seatpost might also be an alternative or perhaps the Look ErgoPost.

That's the idea - but I want a sus post - specifically the ThudBuster.

-----------------------
Pete Cresswell
post #12 of 12

Re: An inch behind KOPS: Anybody doing it?

Read this

http://www.sheldonbrown.com/kops.html

everybody is slightly different. What is good for one person might injure another.

Personally i ride way behind the bottom bracket. I don't know how far behind my knee is.....and I
don't care.....i just make sure the saddle is in the right place and that sets everything else up

Peter
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