# F vs. Z sizing



## coop (Jun 8, 2008)

Considering buying a new Felt in the near future and wondering what the difference in the sizing is. I'm kind of a tweener for sizing as I could go from a 51 to a 54 depending on manufacturer. I like both the Z4 (why no Z3?) and the F3. If my stats matter I'm 5'7" with a 30 inch inseam, probably more torso than leg.


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## PJ352 (Dec 5, 2007)

coop said:


> Considering buying a new Felt in the near future and wondering what the difference in the sizing is. I'm kind of a tweener for sizing as I could go from a 51 to a 54 depending on manufacturer. I like both the Z4 (why no Z3?) and the F3. If my stats matter I'm 5'7" with a 30 inch inseam, probably more torso than leg.


Considering there's no standard for measuring among manufacturers, most of us are tweeners.  

Proportions matter more than height, so best bet is to visit the Felt dealer and (ideally) get fitted for both the Z and F and take them for test rides. 

Coincidentally, you and I are very close in height/ inseam and the Z series geo doesn't suite me very well. I need an effective top tube of about 535 and their 51 has a 525, while the 54 is at 545. Yes, I could run a 110mm stem or 90mm (respectively) to compensate, but that IMO isn't an ideal fit, so that leaves the 52cm F series with an ETT of 535.

I'm not suggesting you'll fit the same on either because cycling experience, fitness, personal preferences, style of riding, etc. enter into this, but it's simply offered as a FYI. 

BTW, these bikes have slightly different purposes in that the F series is Felt's racing bike, while the Z series has a more relaxed geo, affording a more upright riding position. Keep that in mind when deciding, because (again, IME) the F series is slightly too aggressive for my tastes.


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## coop (Jun 8, 2008)

Thanks for the reply, I'll have to get to a dealership to find out which geometry would suit me best. Does anybody (Superdave) know why there is no Z3? Seems like there's a pretty big drop component wise from the Z2 to the Z4. The F3 components on a "Z3" package would be an attractive option imo.


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## Superdave3T (May 11, 2009)

PJ352 said:


> Considering there's no standard for measuring among manufacturers, most of us are tweeners.
> 
> Proportions matter more than height, so best bet is to visit the Felt dealer and (ideally) get fitted for both the Z and F and take them for test rides.
> 
> ...


You've forgotten to account for the difference in seat angle. The 52cm F series bike is LONGER than the 54cm Z series, not shorter. Effective top tube doesn't give you the saddle offset or cockpit length. You need to compare the reach of these two sizes, not the top tube length. One other question, what is wrong with a 110mm stem? How is that beyond the range of a normal length? If you said 8cm or 13cm, I'd agree, but 11cm?

To the OP, why not an AR, which is a balance between the two geometries. The AR3 and AR4 covers both spec options.

-SD

-SD


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## PJ352 (Dec 5, 2007)

SuperdaveFelt said:


> You've forgotten to account for the difference in seat angle. The 52cm F series bike is LONGER than the 54cm Z series, not shorter. Effective top tube doesn't give you the saddle offset or cockpit length. You need to compare the reach of these two sizes, not the top tube length. One other question, what is wrong with a 110mm stem? How is that beyond the range of a normal length? If you said 8cm or 13cm, I'd agree, but 11cm?
> 
> To the OP, why not an AR, which is a balance between the two geometries. The AR3 and AR4 covers both spec options.
> 
> ...


If I'm following you correctly, I 1/2 agree. The effective TT takes into consideration ST and HT angles, but you're correct that, for comparison purposes, the different ST angles matter. For every degree of change there's about a 1cm change to reach, so given the F's STA of 76 and ETT of 535 compared to the Z's 74.5/ 525, the F has the longer reach by about 2cm's.

To answer your stem length question, there's nothing wrong with running a 110mm stem. In the context that I offered it, I was saying that wasn't the_ ideal set up for me_ (but then neither is a 76* STA). It wasn't meant to be a general statement or somehow related to the OP.

I agree that, given the AR's geo, it's worth a look.


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## Superdave3T (May 11, 2009)

PJ352 said:


> If I'm following you correctly, I 1/2 agree. The effective TT takes into consideration ST and HT angles, but you're correct that, for comparison purposes, the different ST angles matter. For every degree of change there's about a 1cm change to reach, so given the F's STA of 76 and ETT of 535 compared to the Z's 74.5/ 525, the F has the longer reach by about 2cm's.
> 
> To answer your stem length question, there's nothing wrong with running a 110mm stem. In the context that I offered it, I was saying that wasn't the_ ideal set up for me_ (but then neither is a 76* STA). It wasn't meant to be a general statement or somehow related to the OP.
> 
> I agree that, given the AR's geo, it's worth a look.


The effective TT only takes the intersection of the top tube/head tube point, and draws a line horizontal to the point where it intersects the seat tube. It does not take into account head or seat angles at all.

As for stem length. Is 110mm too long with Shimano's old brake hoods, or their new ones. What about the F-bikes 9cm of reach vs. the Z bikes 7cm of reach on the bars.

Top tube length and stem length are about 4% of the bike fit equation.

-SD


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## PJ352 (Dec 5, 2007)

SuperdaveFelt said:


> The effective TT only takes the intersection of the top tube/head tube point, and draws a line horizontal to the point where it intersects the seat tube. It does not take into account head or seat angles at all.
> 
> As for stem length. Is 110mm too long with Shimano's old brake hoods, or their new ones. What about the F-bikes 9cm of reach vs. the Z bikes 7cm of reach on the bars.
> 
> ...


You make no sense. If you measure horizontally from center-top of HT to center of seat post, it take both HT and ST angles into consideration and is the effective TT.

The remainder of you post is pure gibberish.


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## Superdave3T (May 11, 2009)

PJ352 said:


> You make no sense. If you measure horizontally from center-top of HT to center of seat post, it take both HT and ST angles into consideration and is the effective TT.
> 
> The remainder of you post is pure gibberish.



A bike with a horizontal top tube length of 57cm and a head angle of 73.5 and a seat angle of 73 will fit totally different than a bike with exactly the same 57cm top tube length and a head angle of 73 and a seat angle of 75.5.

I don't understand how you can isolate a stem length of 110mm being "bad" when there is no indication of the type and shape of handlebar and shifter/brake levers being used. Of course the stem's angle 4deg, 6deg, 10deg, 17deg has an effect as well.

I was trying to point out that the 52cm F series bike with 535mm top tube is LONGER than the 54cm Z series bike with 545mm top tube. 

-SD


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## coop (Jun 8, 2008)

So Dave, any reason Felt doesn't have a Z3 with a SRAM Red setup?


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## PJ352 (Dec 5, 2007)

SuperdaveFelt said:


> A bike with a horizontal top tube length of 57cm and a head angle of 73.5 and a seat angle of 73 will fit totally different than a bike with exactly the same 57cm top tube length and a head angle of 73 and a seat angle of 75.5.
> 
> I don't understand how you can isolate a stem length of 110mm being "bad" when there is no indication of the type and shape of handlebar and shifter/brake levers being used. Of course the stem's angle 4deg, 6deg, 10deg, 17deg has an effect as well.
> 
> ...


To avoid more confusion, let's break this down...
_A bike with a horizontal top tube length of 57cm and a head angle of 73.5 and a seat angle of 73 will fit totally different than a bike with exactly the same 57cm top tube length and a head angle of 73 and a seat angle of 75.5._

Yes, this is true. But you are comparing apples to oranges, because a bike with traditional geo has a TT length that is, by its very nature, effective. A compact geo (sloping TT) bike has a meaningless measurement for the physical TT and a useful effective (virtual) TT that incorporates the HT/ ST angles in that published number. IMO Felt misleads by using *TT horiz *for both traditional and compact geo bikes. They should use that only for traditional geo and effective TT for compacts, such as the Z series.

Next.....
_I don't understand how you can isolate a stem length of 110mm being "bad" when there is no indication of the type and shape of handlebar and shifter/brake levers being used. Of course the stem's angle 4deg, 6deg, 10deg, 17deg has an effect as well._
I already clarified the statement re: the 110mm stem. In general, there's nothing wrong with using one, but in the instance I mentioned (relating only to my fit) it wasn't ideal. 

As far as introducing bar reach/ drop and STI's into this 'conversation', I think it goes beyond the OP's interest or posts thus far. But generally speaking, of course they all matter and are part of the fit equation, but so is HT length and its effect on drop, which is more pertinent to the OP's concerns, IMO.


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## Superdave3T (May 11, 2009)

coop said:


> So Dave, any reason Felt doesn't have a Z3 with a SRAM Red setup?


We used to offer the Z1R and Z25 as SRAM Red options on the Z-series. I think they may still be on some dealers' floors if that is your preferred group. Of course a Z1 or ZC frameset could be sourced to build the bike with the spex of your choice.

-SD


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## Camilo (Jun 23, 2007)

PJ352 said:


> To avoid more confusion, let's break this down...
> _A bike with a horizontal top tube length of 57cm and a head angle of 73.5 and a seat angle of 73 will fit totally different than a bike with exactly the same 57cm top tube length and a head angle of 73 and a seat angle of 75.5._
> 
> Yes, this is true. But you are comparing apples to oranges, because a bike with traditional geo has a TT length that is, by its very nature, effective. A compact geo (sloping TT) bike has a meaningless measurement for the physical TT and a useful effective (virtual) TT that incorporates the HT/ ST angles in that published number. IMO Felt misleads by using *TT horiz *for both traditional and compact geo bikes. They should use that only for traditional geo and effective TT for compacts, such as the Z series.


This might just be semantics. When it comes to sloping top tubes, I believe the terms "horizontal top tube" and "effective or virtual top tube" length are the same thing and I believe that is exactly what the manufacturers intend when they use those terms. They usually list two measurements: actual and "horizontal" (or "effective"). For traditional geometry frames, the numbers are the same. For sloping, they are different, and we look at the "horizontal" or "effective" number, not "actual".

On the subject of fit, that measurement, here's the way I think of it. Whether it be actual or effective - does not take into consideration the STA or HTA. Again, it is simply a measurment of the horizontal line between two points, the center of the seat tube (or a straight line extension of it) to the center of the head tube head tube (or a straight line extension of it). It doesn't matter at all what the angles of those tubes are in making that measurement.

A slacker/smaller STA will be less perpendicular (meaning it angles rearward more), As a straight line extension of the seat tube, the seat post will therefore be further behind the bottom bracket than a steeper (more perpendicular) STA. The taller the total length of seat post+seat tube, the further back it will be.

This, in turn, determines how much saddle set back will be required get the body position over the bottom bracket (and therefore pedals). For any given rider's body and position preferences, a slacker STA will require less saddle set back than a steeper STA. For any given seat post, the saddle will be positioned less rearward on the rails.

When you're sitting on that saddle, since it is positioned less far behind the seat tube (remember - this is where the TT measurement was taken), your reach to the handlebars is less.

Similarly for the HTA. Again, given identical bikes, a slacker/smaller HTA means the HT is less vertical, meaning it angles rearward more. If everything else is the same, the slacker HTA will decrease reach as well.

Of course, there's a bunch of other things that affect reach - horizontal TT length, HT length, stem length and angle, stem height, bar reach, levers, etc. But the STA and HTA affect reach independently of all of them.


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## Camilo (Jun 23, 2007)

SuperdaveFelt said:


> We used to offer the Z1R and Z25 as SRAM Red options on the Z-series. I think they may still be on some dealers' floors if that is your preferred group. Of course a Z1 or ZC frameset could be sourced to build the bike with the spex of your choice.
> 
> -SD


This is exactly why I bought a ZC frameset instead the complete bike in my price range (Z4- Ultegra). I already have an Ultegra group, and decided that if I were to pay for a new group, I'd like to try SRAM (it also didn't hurt that I already have better wheels and saddle, stem and bars that fit me better than those on the complete bike). So I put my Ultegra group on it and am going to find a Force group, maybe if I see a bargain end of the season or off season.

I do wish there were optional groups though, maybe a Z4 with a Force or Ultegra option?


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## PJ352 (Dec 5, 2007)

You may very well be right that this comes down to semantics, because much of what you state is obvious to me. Some, while literally true, is IMO, a stretch. For example, changes to HTA generally changes reach a couple of mm's.

I don't recall stating that _in and of itself _ETT dictated reach, but if I did I retract that, because I know that's not the case. I also know that STA (and to a lesser degree, HTA) among other factors, dictate reach. What I (think I) said was that traditional (or horizontal) TT's _were_ the effective measurement, while the virtual/ horizontal measurement of a sloping TT was effective. And fact is, the measurements are taken from a point at the HT to a point at the seat post, which (as I see it) takes the angles into consideration. Changes to those angles affects reach. 

I don't know why you introduced steeper/ slacker STA's, set back et al into the conversation, other than to say it (along with other factors) affects reach, but IIRC that hasn't been disputed. But it may be of value to the OP.

I hope this clarifies things. If not, I'm game for more back and forth!


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