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how persnickety are you: would you *not* buy a bike...
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walter
Joined: 11 Jan 2004
Posts: 4226
Location: metro-motown-area

1/13/13 6:36 PM

how persnickety are you: would you *not* buy a bike...

...because some spec, say the top-tube, were some trivial amount like 2-3mm different from your "perfect" spec?

the younger anal-retentive walter would be "awwww, hell no!" but now, i'm like "3mm is nothing" -- at least as far as frame specs go.

i'm still pretty persnickety when it comes to getting my position dialed in...down to the mm!


Last edited by walter on 1/13/13 7:58 PM; edited 1 time in total

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ErikS
Joined: 19 May 2005
Posts: 8287
Location: Slowing boiling over in the steamy south, Global Warming is real

1/13/13 6:52 PM

New C not quite right for you? Longer stem and slam the seat back?

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dan emery
Joined: 11 Jan 2004
Posts: 5779
Location: Maine

1/13/13 7:37 PM

not that persnickety..

2-3 mm, I'm not sure I can even measure that accurately consistently...:)

I'd say it varies with the type of bike. A city or commuting type bike, I don't worry about specs much as long as I'm comfortable. For road bikes, I have 2 custom bikes so I do value a perfect fit. For a new stock bike, I'd say about 5mm +/- on seat tube or tt; for a used/vintage bike, 1 cm +/-.

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/13/13 8:04 PM

TT, 3CM window seems to be workable, road GEOM. As long as the shorter TT has some CS and WB to the generous side.

BB drop is 5mm, and I get fussy if less than 75, 75-80 being optimum.

70mm being the limit, 67mm out of the question...

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 3772
Location: Nashua, NH

1/14/13 6:08 AM

There's more to it than just the TT length

You also have to look at the seat tube angle, as that will greatly affect the "effective" TT length. For example, I know that a 72.5 seat angle will give me the setback I need with a straight seatpost. A steeper angle effectively increases the TT length, since I'll have to use an offset post and push the saddle back. Although I haven't seen any frames with a slacker seat tube angle, it would have the opposite effect, since the saddle would have to be pushed forward.

That said, I try to stay within 5mm of what I've found to be the ideal TT lenght on road bikes. My 'cross bike is ~1cm shorter, which I like for off-road use. I'm not especially picky on MTB TT length.

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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA

1/14/13 7:28 AM

Brian is correct that the published TT length has to be considered along with the STA. What you are really concerned with is your reach to the bars and saddle position relative to the bottom bracket. A slacker STA requires a longer TT to keep the same reach and bb relationship.

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dan emery
Joined: 11 Jan 2004
Posts: 5779
Location: Maine

1/14/13 7:58 AM

keeping it simple

I think Walter's question was, assuming you know your ideal tt length for a given setup (including seat tube angle), how much variation will you allow in deciding to purchase.

Walter (and I) have been around here long enough to have endured interminable threads on the relationship betwen tt length and seat tube angle...:)

And you may not only be concerned about reach as you may prefer a certain stem length for handling purposes.

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dfcas
Joined: 11 Jan 2004
Posts: 2388
Location: hillbilly heaven

1/14/13 8:33 AM

For the right bike in a slightly wrong reach one could always have a custom stem made, so I would not let 3mm stop me.

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Andy M-S
Joined: 11 Jan 2004
Posts: 3201
Location: Hamden (greater New Haven) CT

1/14/13 9:28 AM

It all depends...

It all depends on what you want to do with the bike.

I've ridden frames from 61cm to 55cm (those were both Italian-built Bianchi frames, both CDI or so close as to make no nevermind). On the 61, I had little post showing and the bars and saddle pretty much level. On the 55, lots of post, and the bars well below the saddle. Both were acceptable, though they required riding in very different ways.

The reason for the different sizes? I knew no better, and being on the low end of the $ chain, you have to take what's available. The 61 I bought sight unseen, and it seemed to fit OK (though I had to be careful of the top tube). The 55 I bought after wrecking my previous frame, and bought after a quick test ride around town from the bike shop.

More than 15 years down the line from the 61, I know a lot more about what fits and what's comfortable, but I remain convinced that a few mm +/- isn't going to make all that much of a difference.

Of course, I'm a recreational rider/commuter, not a racer. I think sizing and fit are probably much more critical for the latter group.

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/14/13 10:16 AM

One thing in the last year that changes things.
Being more upright, bars 2.25-2.50" lower than seat as opposed to 4". I can fit on more normal TT length bikes. I always found myself slamming the seat and long TT and stems because when I am low, I am way long.

So I am riding a more recreational position now, thus with less weight forward when down low, no need to have my other weight slammed like previously to balance a fore aft CG on the road. My CG is higher though, and I can feel it too.

Translation, I am getting old. ;)


Last edited by Sparky on 1/14/13 2:25 PM; edited 1 time in total

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walter
Joined: 11 Jan 2004
Posts: 4226
Location: metro-motown-area

1/14/13 11:43 AM

thx mr. emery, we've been down that road many times...

i ended up buying this frame, a used semi-modern CF colnago. was advertized as a 61 but actually a 62, with 61 being my "perfect" size. sounds like it's a lot of diff, but it's not. in this size-range of colnagos the frame itself is the same "size" ST measured on-center, they just extend the seat-lug 1cm taller. so that's mostly visual and is a wash.

otherwise, the important fit stuff:
* angles are all the same
* the 62 has a 3mm longer TT (58.5mm vs 58.2 and resultant +3mm to front-center)
* 1mm longer chainstays to balance things out

silly deal on a mint frame, so i'm quite pleased. now i gotta move parts from old frame to new, and then sell the old one!

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daddy-o
Joined: 12 Apr 2004
Posts: 2847
Location: Springfield

1/14/13 12:20 PM

Where do you find deals like that?

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walter
Joined: 11 Jan 2004
Posts: 4226
Location: metro-motown-area

1/14/13 12:48 PM

patience

helps riding bigger frames, less competition!

anyone in the market for a C40HP Mk-III (final version) frame w/ easton full-carbon fork? nominally 60cm size, 73deg STA and 57.7cm TT length. :-)

<img src="http://majortaylorcycling.org/bikes/thumbs/walter_colnago_c40hp-navigators.jpg">

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dan emery
Joined: 11 Jan 2004
Posts: 5779
Location: Maine

1/14/13 1:22 PM

easy decision

Hey Walter, for a nice 'Nago I'd get a hanging bar and stretch yourself out 3mm!

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Wheels
Joined: 11 Jan 2004
Posts: 1139
Location: Needham, MA

1/14/13 3:44 PM

2-3 mm can be mile in some areas.

When bought my first bike, I had it with Ultegra 600. This was with the square tapered spindle BB. Worked great and when I replaced, just bought another BB assembly.

Bought a new bike 7 years later and decided to put 180 mm cranks on it. Ultergra cranks came in 175 mm max, so went with Durace cranks and Ultegra RD/Cassette. The newer cranks had the spline pattern, but only for Durace, not Ultegra. The new BB spindle was 109.5mm instead of 115 mm (Tapered Ultegra BB). Coupled with the cranks being less flared out from the rings, the overall result was a lower Q-factor at the pedal.

My knees were severely affected. Could feel "friction" during the bend, and after only several miles, both were painful. Went back to my old bike, no problems. Thought it was the crank length, but quickly discounted it because when I put three washers between the pedal the crank, problem was solved. However,the washers moved the pedal out of the threads, causing a higher potential to rip out the threads.

Ended up having to buy the XTR BB, which was 116.5 mm and that solved all my problems.

So basically 3 mm difference per side on the cranks was enough to cause a great deal of knee pain or a comfortable ride.

YMMV

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/14/13 4:26 PM

"Ended up having to buy the XTR BB, which was 116.5 mm and that solved all my problems."

Except maybe for the chain line problem that got created? ;)

Shims on the cleats may have got you there as well. Unless then your hips may not have been happy.. ;)

Did they make your pedals with longer spindles optionally would be another point....

I digress...


Back to another area of contention regarding making TopTube length a lesser issue. Between the short reach bars, and longer reach at least Shimano STIs have grown to in the 10s offerings...

Some bar and stem combinations vary in reach considerable of course, just bar reach can...

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dddd
Joined: 11 Jan 2004
Posts: 3158
Location: NorCal

1/20/13 10:53 PM

All agreed, that for the priv of riding a good bike at a good price, can we bend a little?

At least for the bar placement, where various hand positions can be selected from, a few mm would seem to be inconsequential, given also that we ride with some bend in our elbows.
So what could go wrong (me now being 5'9" and leggedy enough to straddle most 61-62cm frames) with selecting a nice, older, somewhat cool Austrian bike that is offered for $50?

Getting home with my latest Craigslist snag, measuring things up gives a good 59.5cm tt and, wait, yikes, both 70-degree seat tube and head tube angles. It will be interesting trying to get this 27.5 pounder up to speed, especially with it's mere 5 sprockets on the freewheel.

Luckily finding a new, 25.6mm inline post to match the bike's Metric steel tubing, and building a new 13-24t five-speed freewheel, I've come up with this, and it seems to work, today chasing the fast group on today's 48mi "metric century":



Yes, lucky for me the 36/52 chainwheels allow me to use a somewhat sporting stack of 13-15-17-20-24t and still get up one 20% grade, and the tweaked Simplex mech's handling it all in total composure.

This one coming on the heels of my 72-degree, and even larger American Eagle project, the 29-pounder I used to get in shape for this past CX season, both bikes allowing an aggressive high-speed attack in aero mode and while climbing out of the saddle:



Last edited by dddd on 1/20/13 11:02 PM; edited 1 time in total

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/20/13 10:55 PM

Them some long lugs....

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dddd
Joined: 11 Jan 2004
Posts: 3158
Location: NorCal

1/20/13 11:07 PM

Yeah, and the other one (American Eagle / Nishiki) has looong-point lugs. It's also, ironically, the far more stable of these two bikes, much better in all modes outside of aggressive cornering. Both now wear 110mm stems and 42cm bars.
It's taken me all of 500 miles to adapt to the flightier directional behavior of the Steyr/Puch, but it does get the job done in comfort, thanks in large part to the fairly soft and broad saddle (Serfas Tegu Tubular Titanium) I chose for both bikes.

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ErikS
Joined: 19 May 2005
Posts: 8287
Location: Slowing boiling over in the steamy south, Global Warming is real

1/21/13 4:26 AM

dddd they are both to big for you if you need to shove the saddle full forward yet the handle well. Interesting.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 3772
Location: Nashua, NH

1/21/13 11:00 AM

I've compromised on a "grocery getter"...

...a bike that will be ridden infrequently and for short durations. It also cost me nothing, as I rescued it from a local dump. It's a Schwinn LeTour 12.2 that's slightly small for me, but it's fine for its intended purpose.

OTOH, any bike that I intend to ride longer distances on needs to fit well. That doesn't mean that they all need to be identical (my 'cross bike is different from my road bikes), but they all need to be close enough that they don't cause discomfort or injury. Thinking about it, that mainly means that the relationship between the saddle and pedals must be the same and the reach and drop to the bars cannot be excessive. Sitting a bit more upright on the 'cross bike is advantageous off-road and doesn't hurt me on longer rides. Conversely, being too low or stretched out would get uncomfortable in a hurry.

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dddd
Joined: 11 Jan 2004
Posts: 3158
Location: NorCal

1/21/13 11:10 AM

I'm actually favoring the bigger bikes now, since adopting the much more forewardly stance. I can easily discern the aero advantage, and the big ring attacks off the saddle feel a lot more efficient now, since I don't have to pull on the bars as the pedaling forces run at their highest, especially while climbing in attack mode. Glad the silver bike has a stout, forged stem(!), it having a 61.5cm TT to go with it's 72-degr seat tube angle btw.

I did initially notice that my entire arms became fatigued and painful after a couple of hours, but the muscles adapted w/in a couple of months and the bar-top position (with aux brake levers handy) gets a lot more use, natch. The leg muscles are still far and away the more tired (vs arms) from extended hard riding.

I've actually been using these very cheap bikes as my daily errands bikes, and aside from the added stability (andconvenience of the aux brake levers), these bikes don't feel much different from my traditionally-fitted race bikes. One can't go anywhere around here without riding some hills btw.

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/21/13 2:41 PM

I'd like to ride those to determine the wonky factor in practical rolling application, geometry wise. ;)

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dddd
Joined: 11 Jan 2004
Posts: 3158
Location: NorCal

1/21/13 4:32 PM

It's an interesting study, I have to say, but I started building up random frames back in the mid-90's after being disappointed with the handling of two (58cm then 56cm w/longer stem) Specialized Epics.
I initially built a few smaller ~54-55cm bikes up to see if the smaller frames with longer (and with some rise) stems would relax the descending handling of the twitchey Epics. I came to like the effect, and built several more on 56-57cm frame platforms.
These last two "projects" came mostly out of just wanting to ride these cool-looking, well-preserved relics, and luckily the ($140) silver bike came with that 110mm forged stem already. The bike's incredible stability makes (downtube) friction-shifting a LOT easier over our hilly, technical foothill roadways, and the challenge of really sorting out these cheap bike's componentry just keeps on giving until many hours of one's spare time has been spent :-)
I was able to put in another 37mi (climbing ride) today, making it 4 days in a row over 25 miles. Our weather highs have miraculously been in the low 60's for several days now.
Lastly, I have to award a failing grade to the Nashbar-brand chain lube, it having ended up on my back rim despite a couple of very thorough wipe-downs.
I will be diluting it with much OMS for a more scant application in the future, which will at least make it almost as cheap as da Forum Lube.

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Sparky
Joined: 08 Dec 2003
Posts: 15809
Location: Portland, OR

1/21/13 7:44 PM

"I was able to put in another 37mi (climbing ride) today, making it 4 days in a row over 25 miles. Our weather highs have miraculously been in the low 60's for several days now. "


Lucky dog, enjoy. Sure wish that weather was here. ;)

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