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Frame Geometry...what's up with the Italians?(22 posts)

Frame Geometry...what's up with the Italians?MXL02
Aug 26, 2002 6:08 PM
I had a bit of trouble getting my saddle back far enough on my Colnago MXL, so I did some research and noticed that DeRosa, Ciocc, Coppi, Carrera, Cinelli, etc, also had more upright seat tube angles, with shorter top tubes and less set back than Merckx, Look, and other non-Italian builders....what's up with that?
same problembianchi boy
Aug 26, 2002 9:03 PM
I'm not sure what's behind it, but I've got the same problem on my Gios. It's hard finding a saddle with rails long enough to get the "correct" knee over pedal position. Can anyone recommend any comfy saddles with long rails?

Bianchis also have steep seat angles. Some of the more classic, steel Italian frames have 73 seat angles -- like the Cinelli Super Corsa, Casati, Tommasini -- particularly in the larger sizes.
nothingET
Aug 27, 2002 5:06 AM
I've stated before and I'll state it again that the first step in buying a bike should be to find the seat tube angle that puts you center or near-center of your rails. Others can say it doesn't matter but it does. You can still switch to a post with more setback and a saddle with longer rails (the Selle San Marco Era is one).

Different companies have different philosophies about STAs. Most start steeper at the smaller sizes and become slacker at the bigger sizes. Some keep a steeper STA all the way through (e.g. Coppi, Guerciotti), some keep a slacker STA all the way through (e.g. Look). Merck targets bigger guys who might have different needs than the rest. But it is not necessarily true that the Italians uniformly have steeper STAs and shorter top tubes. Guerciotti, Bianchi, Carrera have longish top tubes. Tommasini has somewhat slacker angles and shorter top tubes, etc.
I thought the elusive 'standover height' was your first step?TJeanloz
Aug 27, 2002 5:37 AM
Did we convince you otherwise?
no, not exactlyET
Aug 27, 2002 6:21 AM
I've always advocated knowing your seat tube angle first and limiting your selections to bikes that have STAs that are close. The problem is, most don't think about finding their STA first even though they should. They want a simple procedure where they go into a store and test-ride a bike. So when I posted a while back my "bikefit for idiots" or something like that, I started with inseam and approximate upper and lower bounds of standover clearance--not as a means unto itself--but as a proxy for determining the correct seat tube size, which it is. (This point is so belittled here as if it doesn't matter at all, and then many find they can't reach the drops on their 56 OCLV which is really a 54.) After they test-ride the bike, making seat adjustments as necessary, they're supposed to make a note of where they end up on their rails, and, after comparing the STAs of the bike they test-rode, zone in on their ideal STA with a few test rides of other bikes. That is what I said. But yes, ideally, STA is the very first step. But how do they find it? Through test rides (but note: not necessarily through the Serotta size cycle fitting; I had a 3-hour fitting on it by a certified tester who told me I needed around 72.5 and no way anything over 73 when my true STA is 73.5-74).
STA vs. seatpost setback vs. rails - can't we all get along?bill
Aug 27, 2002 6:29 AM
what's the big deal about STA and centering the saddle's rails? If centering is that important, which I'm not convinced that it is, can't it be adjusted by getting a seatpost with a different setback?
Second question is, what's the big deal about centering the saddle's rails?
This all goes back to what Doug Sloan said about adjusting bikes to fit. At a certain point, you're going for an aesthetic look, and a saddle slammed all the forward or back doesn't look quite right, but what difference does it make in performance?
STA vs. seatpost setback vs. rails - can't we all get along?Spunout
Aug 27, 2002 6:36 AM
A saddle in the middle of the rails will absorb shock better. I am holding my new Thomson setback seatpost, and is just the cat's a$$(I have longer Tibia). I still need this on my Lemond (73* and longer top tube).

The european frames were built around a short top tube for a longer stem (see Merckx) for stability.
setback vs. rails and getting along are 2 different things :-)ET
Aug 27, 2002 6:50 AM
It doesn't have to be dead-center, but close (i.e. +/- .5 degrees) is nice. There are other things aside from shock absorption. Anvil has claimed it affects balance over the bike and handling, and that some may notice. Too slack an angle and there will be more frame than necessary too far under your seat (extra weight, for one thing :-)). The list goes on.

Presumably, putting on a seatpost with too much or too little setback than is appropriate for that bike will affect the ride. If not, to take things to an extreme, choose a bike with the steepest STA and a post with the most setback you can find. This would produce a lighter bike. Why not? Cause something's gonna suffer. How much? Who knows?
setback vs. handlingcyclopathic
Aug 27, 2002 10:03 AM
most frames with shallower STA also have longer chainstays. In reality it is not the saddle moved backward, it is BB moved forward. Putting too much weight on back wheel changes handling, and in this matter even little is much. On typical set up offset btw rear axle and saddle is only about 2-3". Just for kicks put your saddle over rear axle and try to ride w/o hands.

Second comfort. Moving seat back puts more bump into your a$$. One of the reasons why touring frames and mtbs have longer chainstays.
comfort..colker
Aug 27, 2002 7:04 AM
a saddle clamped at the rail extremities will react diffenrent than one clamped in the middle. it's not a BIG geom. issue but it's the little things that count on everyday 30km rides.
You mention GuerciottiSteve98501
Aug 27, 2002 1:00 PM
I'm riding a Guerciotti, 59 cm (c-c), and I've been wondering what the STA is. I've got my Brooks 17 shoved all the way back on the rails, and wish I could get another 2 cm. I'm guessing the STA is 74 degrees. Do you know if that is correct? I'm beginning to think I might have to get a Merckx frame to get a good fore and aft weight balance. I thought about trying to find a seatpost with more setback, but am concerned that would just put too much of my weight on the back, reducing front end stability. I like my bike, but I'm dissapointed in not being able to get my weight further aft of the bottom bracket. I guess I have longish femurs.

I tried looking for a source of information of Guerciotti geometry, but wasn't able to. Where did you find it?

Thanks for any information.

Steve
Guerciotti geometryET
Aug 27, 2002 5:47 PM
Go to

http://www.Bullteksports.com

and click on "road frames" at bottom left or in dropdown catalog index at top. Click on Guerciotti, then click on a bike's picture. It gives the STAs. Steep!
Look Ergopost? Thomson setback post?djg
Aug 27, 2002 7:12 AM
Some folks have complained about the Look but I've had no problems--tons of adjustability.
re: Frame Geometry...what's up with the Italians?flying
Aug 27, 2002 7:37 AM
I have the same problem with my MXL.
So much so that I am thinking of selling it & getting the Look 381i

It is not as ET suggests that I cannot center knee over BB.
I could do that easily. But all I do is climb & I like the seat quite a bit *behind* the BB. The Look 72.5 seat angle versus the 74 on the MXL should work better for me.

This is actually only a prob on the smaller MXL's above 53 c-c or 55 c-t the seat angle starts to slacken.
all you do is climb?ET
Aug 27, 2002 7:49 AM
Don't you have to come back down? :-)

When one descends, one tends to slide back in the saddle, and when climbing, one tends to slide to the front of (or off) the saddle. Climbing-specific bikes are more likely to be designed with steeper, not slacker angles. But whatever works for you.
huh.........JohnG
Aug 27, 2002 8:03 AM
What are you talking about?

Climbing ====> slide back!

JohnG
all you do is climb?flying
Aug 27, 2002 9:38 AM
Ummm Could be for you that is true but it has always been the opposite for me & everyone I know.

Most climbers like to be back further.The only folks who usually slide way forward are TT & Tri riders.

Yes I descend too ;-) But all rides includes an average of 4000' of climbing.
what size is your mxl?colker
Aug 27, 2002 3:23 PM
i could be interested..
what size is your mxl?flying
Aug 27, 2002 9:57 PM
53 c-c or 55 c-t
As new not a scratch.
Even has its own bedroom ;-)

Not sure I will sell it till I ride
the new bike.
oooh, that's beautiful!rufus
Aug 28, 2002 7:19 AM
for my biases, all that would need is a silver quill stem and bars, and a chromed fork. perfection!
re: Frame Geometry...what's up with the Italians?MXL02
Aug 27, 2002 8:58 AM
Yeah- I actually moved the seat forward about 1cm...my KOPS is about dead on now, before I was behind the PS. Although a Thomson setback might help (and I may try it) I, like you, am seriously considering a Look, with that 72.5 STA.
re: Frame Geometry...what's up with the Italians?mapei boy
Aug 27, 2002 4:03 PM
Ain't it great that frames have national identities?