question for dbrk on the IF Crown Jewel

[Bradford]

In the mountain bike thread you said that the IF Crown Jewel had " the weirdest geos of any road bike I know about." What is weird about it?

I've only started to think about geometry since I've started reading this web site and am still learning. I have plenty of miles on a CJ and know how it rides. Understanding how the CJ's geo is different would help me understand a little more about how geo changes ride characteristics. (without riding many bikes with different geos, which I won't be able to do anytime soon).

Thanks for the help.

[dbrk]

Okay, let's think about this a bit...Here are the numbers for the IF CJ in three common sizes:
56 cm 81.4 cm 57.0 cm 73.0 ° 72.5 ° 45 mm 70 mm 139.0 mm 100.1 cm 56.9 mm
57 cm 82.5 cm 58.0 cm 73.5 ° 72.5 ° 43 mm 70 mm 148.0 mm 100.4 cm 55.0 mm
58 cm 83.5 cm 59.0 cm 73.5 ° 72.5 ° 43 mm 70 mm 158.0 mm 101.4 cm 55.0 mm

Got that?
That's c-c st, soh, ttL, hta, sta, rake, bb, htL, wb, trail. Clearer?

Notice that the headtubes are all really short, at least by my standards and considerably shorter than Serotta without a htext, and that is pretty short. This means that the bike is pretty low up front, no matter how you cut the cake since the tt is really proportionally long and made effectively longer by the very relaxed seat tube angles. Even if you "size up" as I often suggest, you end up with a bike with a really long tt. Add in the relatively high bb mitigated ever so slightly by the long f/c that creates the relatively long wheelbase, and this is a bit odd. The trail numbers are all short, meaning that the steering is quick even with the slack relatively "normal" hta and that short headtube places the weight forward. If you look at, say, stnd Serotta numbers or most "competition" bicycles, here's what's "weird": slack sta's, long toptubes, short trail, high bb...
Now this does NOT mean it's bad but the effect of this will be a fast steering, less stable in the rear ride that emphasizes stretching you out and putting your weight forward. I think it was Robert Millar who hated the IF but I mostly think that pro opinions are pretty useless: how many of us want or should ride like pros? Pleeze. But just in comparative terms, IF definitely has their own idea. I have had three or four IF including a fixed gear IF that I regrettably had to sell in less good times. I like it, but it was long, low up front...what I liked was the butt back feeling (sta), what I liked less was how it descended. IF cross bikes are a whole'nother story.

dbrk

[jerk]

the jerk agrees....these are perhaps the weirdest frame geometries out there....colnagos have strange geometry too but the difference is the front centers aren't completely out of whach with the rest of the bike on a colnago so with proper weight distrubution a colnage will handle better than almost anyother bike while an iF road bike is about the weirdest sketchyiest ride you will ever want to experience....the jerk thinks the boys at INDYFAB make great bicycles...but rip off someone elses handling geometry if you want the bike to ride right.
love,
the jerk

[Bradford]

Thanks for the input. Also, thanks to Senor Jerk for helping out.

The CJ I have experience with is a custom, but since it wasn't my custom, I'm not sure exactly what the angles are (all I know for sure is it is 60 cm st x 59 cm tt). I picked it up for short money on ebay to give me a couple of years to really understand what I want before I drop the big bucks on a custom.

The longer top tube comment makes sense to me. At 6'3", I've always prefered being stretched out on a bike, and feel very comfortable on the CJ. That leads me to believe that I should try some longer top tubes on other bikes to see how that feels.

I don't find that it is a sketchy ride, but that may be a relitive comment. I liked the Legend I rode a lot more than the CJ, which is why the Legend is at the top of my list for my next bike. (I'm also considering a Parlee or a Moots). Perhaps that explains one of the reasons I liked the Legend so much. The CJ is certainly good enough for now, considering it only gets about 1/3 of my attention with the touring bike and tandem getting the rest. But I hope to be replacing it about this time next year.

One thing that strikes me is how my attitute towards my touring bike has changed over the last year. There was about two months that I only rode the CJ and the tandem, and then when I went back to the touring bike I felt that the reach was way to short. It just felt awkward sitting up so much. It is a better position for commuting and touring, but being stretched out feels so much better to me. I also switched stems on the tandem after getting fitted for it at Wheelworks. I just couldn't handle being so cramped and added some lenght to extend the reach.

[Sandy]

dbrk, I have learned, as a teacher, that you must ask questions, so here is one for you. What does f/c mean? Your post seemed to explain your thoughts quite well, but I must admit that I do no know, for sure, what f/c is. I cannot skip lines so I will sign it here. Sandy

[dbrk]

Sandy, always good to ask and I apologize for not explaining this more clearly. f/c means front/center. This is the measurement on a horizontal line from the center of the front hub to the center of the bottom bracket. It's an important bit of information especially when seen in light of the bigger picture, and all geometries must be seen as part of a whole. To get the whole wheelbase you simply add the chainstay length with the f/c. You need a certain number, depending on the frame size, to avoid the dreaded TCO, still called "toe-clip overlap" even though very few of us still use toe-clips (I do on certain bikes, much preferred to clipless, but that depends).

If anyone is interested in more wax on, wax off about f/c and these other issues, I'm happy to accommodate since it keeps me away from working.

dbrk

[Sandy]

dbrk,

Thanks. I thought f/c had to do with front and center, but being a math teacher in high school some 40 years ago, I was thinking about some ratio of front to center because of the f/c and hence I was obviously confused, evn more than normal. Thanks for the help. Sandy

[Indy Fab]

Hmmm...I'll defer to your wisdom and experience, but a longer top tube doesn't quite jibe with my Ti CF.

Here's the stats:
st = 55.0
soh = 81.2
ttl = 55.0
hta = 150.6
sta = 73.5
htl = 150.6
wb = 99.2
trail = 56.0
fork offset = 45

Notice the seat tube angle of 73.5. Douglas, I would think that would account for a shorter top tube on my bike, relative to the stats you listed.

I'm 5'10" with a 32" inseam, and I don't feel any more stretched out on this bike than other similar bikes I've ridden.

Isn't the whole point of getting a custom bike to avoid problems like being overly stretched out?

[Sandy]

Indy FaB, I think that you put the htl in for the hta by mistake.

Sandy

[Indy Fab]

Oops, right you are. The hta should be 73.0