One more sizing question
 

Hi,

I just ordered a Kestrel Evoke 59cm size. Now I am afraid that will be too big compared to my 58cm Cannondale that I use (and other 58cm touring bike).

Main differences are: Top tube Length 58.7 versus 57.5 (Canndondale),
Standover height 82.4 versus 82.9 (Cannondale).
Wheel base is the same.

Will the 1.2cm difference on the TT make a huge difference?

I am not a racer, just like to ride with a group and longer rides solo.

Any help will be appreciated.
Thks.

A shorter stem can give you the same reach (if you're comfortable with your current reach). You might need less saddle setback since larger frames typically have slacker seat tube angles, but would have to see geometries of both to know for sure.

Yes. You will definitively have to make adjustments. Check frame angles and fork length because everything will have an effect. As far as setback, I do not know if you should adjust it to compensate a change in angles. I do know that should not move it forward to compensate reach:

My big wory is I am going to throw away the new Kestrel because it is too big.

Evoke Geometry:
http://2009.kestrelbicycles.com/Road/Evoke.aspx

Cannodale Geometry: ST Angle 73.5, HT Angle 73, TT 57.5cm, Wheelbase 100.5cm.

What is the length of the head tube, the infor you have provided is meaningless without that. your top tube may be longer but if the head tube is also longer then the increase in top tube length will not equal the increase in reach. You are confusing TT length with reach which is measured from the centre of the bottom bracket to centre of top of head tube.

Provide a link to the cannondale geometry and I will put in my spreadsheet when I get home which will give an answer to the mm.
I also need to know the stem length you are currently using, the angle of the stem and the number of spacers. To get really accurate I also need the headset height between the top of the head tube and the first spacer for each bike.

Hello lazerxr,
Here is my Cannondale 58cm geometry: stem is 110mm, rising, 25mm spacers
http://www.twothirds.org/caad4-geometry.pdf

This is the Kestrel just ordered 59cm size, my mistake, I thought 59 is closer to 58 than 56!!:
http://2009.kestrelbicycles.com/Road/Evoke.aspx

I just need to find out if the bike will fit me similar to the Cannondale that I am used to.
Thank you.

With the more relaxed seat tube, some of that extra top tube length will be negated by the saddle position. So, your saddle will be a tad further forward (in relation to an equal seatpost, NOT to the bottom bracket) and you probably want a 1cm shorter stem. You're right that the 56 would have been closer, although that has a shorter TT resulting in the need for a 1cm longer stem.

Hi
That chart does not include head tube length which is critical to determining anything about a frame really. Can you measure it an let me know?

Hi,
C'dale head tube length: about 16.5cm
Kestrel Evoke Ht length: 18.2mm

Actually, since HTA and STA are usually within a few degrees of each other, it won't tell you much other than how high the handlebars will be with the same number of spacers and the same rise of stem.

Incorrect, that is a very simplistic way of looking at it. It is critical to reach when comparing frames. Reach is measured from the centre of the bottom bracket not the seat tube. Draw it out and you will see. It is possible to have two frames with the same horizontal top tube length and different reach due to head tube length.

OP There is a lack of info to get really accurate however making some reasonable assumptions i suspect you will get a very smilar fit by using the stem flipped up similar to your cannondale, 15mm of spacers under it and a 100mm stem instead of 110.

The seat tubes are different angles which complicates things but assuming you align your knee over the pedal the same way on both bikes then the above will get you very close to your current position

Why some Kestrels sizes are 56, 59, 62 and nothing in between.
It is quite a big difference between sizes.

FWIW I think you did the right thing getting the 59. The head tube on the 56 is really very short and you are already using 25mm spacers with a flipped up stem. for the 56 to work you need 30mm spacers under a 120mm stem and you will still end up slightly lower at the front than your existing bike. reach is really the issue here and in my experience its nicer riding with less spacers and a shorter stem then it is riding with loads of spacers.

Anyway let us know how you get on.

Actually, you're still looking at it too simply. If you're setting up the bike to have the same handlebar height, you would then be making the effective head tube the same length. Whether you have that length in head tube or in spacers, it still continues backward at the same angle. But even if we assume for a moment that you would leave the handlebars at different heights, you're talking about a difference less than 5mm unless you have some crazy length head tube.

You gotta look at the entire bike set up, not just what the bare frame looks like on a piece of paper.

Anyway, that being said, your advice to the OP makes perfect sense to me.

Post #7 tells me about spacers, the 25mm spacers on the op's bike accounts for about 7mm reduction in reach, in other words the best part of the next size stem length should he remove the spacers, the info lacking is the height of the headset above each frame which I simplistically took as equal on both bikes, however my own bikes range between 15 and 20mm which accouns for another mm or 2 reach adjustment. by reducing stem length you reduce height as well as reach particularly with the stem flipped up as the op says, which also effects the number of spacers required and therefore reach again.

Of course I have also assumed that handlebar reach is equal on both bikes which is unlikely to be the case, I find it surprising how many people rattle on about how stem length effects handling when no one blinks if you tell them you use 70mm reach bars or 90mm reach bars. I have also assumed the length of the hoods is the same which is likely to be wrong. I have also assumed that the stem angle on both bikes is the same which may not be the case.

All in all though the more info you take into account the closer you will get with an estimate of set up on the new bike. With my assumptions and the knowledge that in reality you may not notice just a few mm of differene anyway, the set up I posted will get the op pretty close. The calculation comes out at +-about 2 or 3 mm on both reach and height - but like I say some of the assumptions will be off.

By the way OP on the 56 frame suggested as being closer in post 8 would require you to use a 120mm stem on 35mm spacers to get a similar fit. IME I find bikes ride better with less spacers and 35mm is getting up there. If you post a picture up here of a small frame using 35mm spacers and 120mm flipped up stem, you will spend the rest of the day reading comments telling you to get a larger frame. Again, although it seems some people are saying im not thinking about this correctly - I am. and the numbers I have posted are calculated, and correct.

As a side note however, if you can survive riding a lower front end then the 56 would allow you to flip the stem flat and get lower without using a 90mm stem which you would need on the 59

Hope this has helped