Calling all frame fairies....

[biker7]

I know there are quite a few out there ...so will open up the discussion/debate. There have been many references to the difference between conventional and new fangled compact frames with sloping top tube geometry. Want to take a deeper dive as I am considering a new bike and in particular the new Pilot 5.0. Comments made here-to-fore as I see it weren't as inaccurate as they were incomplete. There is a difference. The frames don't line up exactly and it isn't all pertinent just to a shorter seat tube and more exposed seat post and the three points of contact, bars, seat and BB. What I haven't heard in previous threads is what it really is...which is length of steerer tube relative to length of top tube what in effect establishes handle bar height relative to seat height for the size bike you ride. And I am trying to get to just that spec. comparing the new Trek Pilot against the Trek 5000 with conventional geometry. Here are a couple of links I would like the enlightened frame guys to compare:

Trek 5000 conventional geometry:
http://members.roadfly.com/georgemann/Trek5000Geo.jpg







Trek Pilot compact/comfort geometry:

http://members.roadfly.com/georgemann/TrekPilotGeo.jpg


For purposes of discussion, I would like to focus on comparing a Trek 5000 in 60cm size...what I ride, to the new Pilot geometry in Large which according to Trek's website is 63cm...which is really an equivalency and not the true seat tube length of course with the Pilot's compact geometry not well represented in the diagram BTW.

There are some subtle differences comparing the two sizes...wheel base, BB height from the ground, slight front fork angle difference etc...top tubes are pretty close in length but Trek is deliberately non-descript about actual geometry of the new Pilot not only in terms of the diagram they provide but dimensions they display. What really matters is "steerer tube length" when it comes to how high the bars are. If you go by Trek's 63 cm size "equivalency"...clearly not reflecting seat tube length as shown...which is quite a bit shorter than the Trek 5000 60cm conventional seat tube length as we all know, one could surmise the steerer tube is just under 3 cm longer (cosine of steerer tube angle) for the Large size Pilot which in effect gives it a more upright or comfort oriented riding position. One also can't learn much from stand over height but some inference can be made because the specs are close and the Pilot's top tube slopes quite a bit but because the stand over is so close, have to believe the steerer tube is longer on the Pilot. But this is only reading between the lines...what I am seeing. Unfortunately since there are no Trek Pilots around in my area yet...only pure conjecture. I believe it is unfortunate that Trek is so deliberately unclear about defining its frame dimensions for the new Pilot but they may figure real road bike guys don't ride comfort bikes
Comments are welcome.
George

 

[boudreaux]

There have been many references to the difference between conventional and new fangled compact frames with sloping top tube geometry. Want to take a deeper dive as I am considering a new bike and in particular the new Pilot 5.0. Comments made here-to-fore as I see it weren't as inaccurate as they were incomplete. There is a difference. The frames don't line up exactly and it isn't all pertinent just to a shorter seat tube and more exposed seat post and the three points of contact, bars, seat and BB. What I haven't heard in previous threads is what it really is...which is length of steerer tube relative to length of top tube what in effect establishes handle bar height relative to seat height for the size bike you ride. And I am trying to get to just that spec.

ya know, all compacts aren't the same, just as all traditional frames aren't the same. A Rivendell to Colnago comparislon is like apples to cantalopes as is the 5200 to Pilot. The compact Pilot or Specialized Roubiax don't begin to compare to a Giant TCR. Suggest you actually get on a a few and see what fits your pistol best.

 

[artmichalek]

ya know, all compacts aren't the same, just as all traditional frames aren't the same. A Rivendell to Colnago comparislon is like apples to cantalopes as is the 5200 to Pilot. The compact Pilot or Specialized Roubiax don't begin to compare to a Giant TCR. Suggest you actually get on a a few and see what fits your pistol best.

You must be a better reader than me. I didn't see a comparisson to the Roubaix of the TCR in there at all. Comparing sizes within one manufacturer's line should be a lot easier than Trek seems to be making it. And it's hard to get on a few when the local dealers don't have any.

Back to the question, it might be best to ignore the standover height measurement on the Pilot. It would imply a similar size if it was measured right up at the head tube, but it's kind of ambiguous.

 

[biker7]

True that...and I am trying brother. Not only is it hard to find an '05 bike in my size right now but hard to get a true test with all the snow on the road.
Have to ride before you buy.
George

 

[artmichalek]

True that...and I am trying brother. Not only is it hard to find an '05 bike in my size right now but hard to get a true test with all the snow on the road.
Have to ride before you buy.
George

It's going to be snowing here for at least another month. Where are you located? Ibought my last frame without riding it and haven't had any problems, but I at least had all of the measurements. Have you tried contacting Trek yet?

 

[biker7]

yeah more than ambigious artmichalek...don't think there is any question Trek has deliberately not provided complete frame size information.
The wheel base difference between the bikes is substantial...the Trek 5000 is clearly the quicker bike...and tube angles will also affect reach as well over and above top tube length. The final determination will be a ride of course...was curious what forum member input would be.
Thanks,
George

 

[biker7]

gonna snow here for another month as well artmichalek...I'm in Michigan. LBS's are going to get these bikes in soon. Since there is little discounting going on...a 5000 will go for $2K and Pilot 5.0 for about about $100 more...not that plussed...can wait until the better weather. Also want to ride an OCR C3 with 105...a LBS has one in stock in Large.
Thanks,
George

 

[boudreaux]

Comparing sizes within one manufacturer's line should be a lot easier than Trek seems to be making it.

It ain't necessarily so when they are totally different types and geometries.

 

[boudreaux]

You must be a better reader than me. I didn't see a comparisson to the Roubaix of the TCR in there at all.

Maybe bub, but it's really more about comprehension skills.

 

[RC2]

At the end of the day only you will live with the bike day after day, so your impressions from riding different geometries is going to be hold a heck of a lot more water than any words you read here. On a similar frame w/the same geometry (other than the compact-conventional) I can't tell a thing... my conclusion has always been it's a 'which do you think looks better?' question.

 

[biker7]

you're right of course RC...but what do we do when we aren't riding?...talk about riding...lol
Will of course road test each and report back. Believe only a foolish man would throw down $2k for a bike without testing others for comparison but as many know, its been done. I was hoping others who live in a more favorable climate had ridden each for a comparison. So far, no word.
George

 

[RC2]

...What really matters is "steerer tube length" when it comes to how high the bars are...

Theoretically steerer tube length has nothing to do with the other geometry as you could have your bars as high on a colnago C50 as you would on fat tire beach cruiser... it would look kind of funny though. An overall frame geometry like a TCR/Tarmac/5000 vs. OCR/Roubiax/pilot (using the Giant/Spec/Trek comparison) will have a shorter wheelbase, quicker handling, and put your torso into a lower more aero position intentially as they are the racing version/geometries...a lower bar/stem naturally goes with that on the typical racing-oriented frame, compact or not.

 

[biker7]

...actually RC, fly handlebars on a colnago C50 is a growing trend.
Believe mounting a banana seat is next.
Watch for it at your LBS.
George

 

[artmichalek]

...actually RC, fly handlebars on a colnago C50 is a growing trend.
Believe mounting a banana seat is next.
Watch for it at your LBS.
George

They're just waiting on the Pro Race whitewalls

 

[biker7]

yeah the whitewalls are a nice retro touch
George

 

[RC2]

...fly handlebars on a colnago C50 is a growing trend....

If you wanna spend your money that way, don't skimp on the grip-end streamers.

 

[jvs]

For frame fit there is only one measure important, that is the distance in X and Y direction from the bottom bracket to the lowest point where your stem can be (where the steerer leaves the headset)

For how the bike will ride add to this:
- head angle & fork rake,
- chainstay length and
- bottom bracket height,
i.e. apart from frame material, stiffness etc.

 

[biker7]

agree...in principle with one variable missing. Exception being...from a geometry stand point, seat tube angle affects virtual top tube length...so it just isn't horizontal X-distance from BB to top of steerer tube.
In support of your comment, the Pilot, OCR and other more upright bikes, Y is by comparison larger for same sized X dimension, conventional frames in part due to more upright steerer tube angle by a degree or so but mostly steerer tube length...the biggest contributor.
George

 

[jvs]

agree...in principle with one variable missing. Exception being...from a geometry stand point, seat tube angle affects virtual top tube length...so it just isn't horizontal X-distance from BB to top of steerer tube.
George

Hi George,
The point is, seat tube angle does affect top tube length and virtual top tube length (measured horizontally disregarding slope) as you said, but it does only affect the front end length IN COMBINATION WITH the (virtual) top tube length. That said, you can have the same fit with a slack seat tube and a long top tube or a steep seat tube and a shorter top tube that will both result in exactly the same front end length. Seat angle alone is only relevant for how far back you can get your seat and even that can also be done with a seatpost with a lot of setback.

 

[biker7]

We are on the same page....no refuting physics One thing you hear alot of reference to is...the frame triangle which in actual fact it is a four sided trapezoid with the shortest leg being the steerer tube...the first thing I look at to see if a frame will fit me.
George