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Discussion Starter · #1 ·
I'm sure this has been discussed many times so my appologies in advance but....

If you find yourself "in between" when it comes to frame size is smaller better than larger? or vice versa?

eg without adding in all the other "fit" details.... if I fit on frame that will have me using a 120 or 130 stem is it better than going to larger frame which will have me using a 100-110 to achieve the same reach?


and fwiw what would be the reasoning behind riding the smaller or larger frame (depending on which one is suggested)?

thanks.
 

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I always go smaller. Two reasons - first the larger sometimes has a headtube length that would preclude me from getting my bars down where I want them. I'd rather add a 1cm spacer to the shorter HT. Second, I like to be able to clamp my bike in my shop stand without adjusting the seatpost. Larger always precludes that unless it's a sloping top tube design.
 

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hardride27 said:
I'm sure this has been discussed many times so my appologies in advance but....

If you find yourself "in between" when it comes to frame size is smaller better than larger? or vice versa?

eg without adding in all the other "fit" details.... if I fit on frame that will have me using a 120 or 130 stem is it better than going to larger frame which will have me using a 100-110 to achieve the same reach?


and fwiw what would be the reasoning behind riding the smaller or larger frame (depending on which one is suggested)?

thanks.
Depends on what you are looking for in a bicycle. In my experience, racers tend to go with smaller frames. This gets your body down into a more aerodynamic position, and it allows you to utiltize certain muscles in your legs more efficiently. Non-racers tend to sit in a more upright position. Many find this more comfortable and it helps ease neck strain, making it easier to look around while riding. The same logic applies to stem length - longer is generally more aerodynamic, shorter allows you to sit up straighter, BUT you definitely do not want to feel hunched up over the bars, so make sure your top tube/stem combination stretches you out enough that you are comfortable.

Back in my race days, I road a "tiny" 62cm frame (I'm 6'6"). It caused a lot of strain on my lower back and hips which resulted in some permanent damage. Now I ride 67 and 68cm frames. They are much more comfortable, but I would guess that I could go a bit faster on the smaller frames.

Good luck!

- FBB
 

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hardride27 said:
I'm sure this has been discussed many times so my appologies in advance but....

If you find yourself "in between" when it comes to frame size is smaller better than larger? or vice versa?

eg without adding in all the other "fit" details.... if I fit on frame that will have me using a 120 or 130 stem is it better than going to larger frame which will have me using a 100-110 to achieve the same reach?


and fwiw what would be the reasoning behind riding the smaller or larger frame (depending on which one is suggested)?

thanks.
different bike maybe?
 

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I read an article once that said to buy the smallest bike you can fit comfortably on. The main reason not to go to small is that you may not be able to get your handlebars high enough. As far as the stem length goes, different length stems can be used to allow you to sit more upright or more stretched out or to change the feel of the steering.

Let's say you can be reasonably comfortable on a partticular bike with a stem anywhere from 100mm to 120mm in length. If the geometry on the bike is very twitchy or quick steering, you can use the longer stem to slow it down a little and likewise if the the steering is slow, use a shorter stem to quicken it up.

Also the same bike with two riders the same height but different weights will handle differently. A heavier rider will most likely need to slide the seat back so as to attain proper balance over the frame. The result will most likely be that the heavier rider will need a shorter stem since he is now sitting further from the handlebars. The lighter weight rider will probably not do this, therfore he will use a longer stem. I know that I went though a bunch of different stem lenghts on my bikes until I found the right lenght for each one.

I think that the smallest frame you can ride and still bring the handlebars up to a comfortable position is the best size. And the stem that allows you to ride comfortably and enjoy the handling of the bike is the best length..
 

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mostly good advice..

You didn't mention the frame sizes, but 120-130 stems are most often seen on larger frames and 100-110 on smaller ones. There is no rule that says you can't use a 100mm stem on a 60cm bike. I've been using a 120mm on a 51cm frame with short reach (70mm) bars. My other frame has a 100mm stem with standard (85mm) reach bars. Both handle just fine.

One frame size usually requires only a 10mm difference in stem length, if you properly account for the effect of the the seat tube angle on the reach. With some brands you can see as much as a 15mm difference, which usually means two stem sizes (longer or shorter) will be required.

I'd pay more attention to the head tube length. If the smaller frame requires more than 2cm of spacer stem, then it may be vertically too small. Its better to use a 96 degree stem and 2cm of spacer than an 84cm with 4cm of spacer.

I wouldn't worry about the effect of stem length on the steering. A 20mm difference in the length will only change the length of the steering arm about 7%.

The smaller frame will usually handle just a bit quicker than the larger one.
 

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Seems to me

As someone noted earlier, you should continue to look for the right bike. Of course, it takes some knowledge of your fit preferences.

For instance I know that I want a bike with a 15-16cm head tube, a top tube of 54.5-55cm with a seat tube angle of around 73. If I move the seat tube angle up to 74 degrees, I know, (thanks to C-40) that my tt should be an centimeter shorter.
I like a smaller bike than a bigger bike, so I will want a CTC seattube of around 54cm and up to 55cm, but no taller. On this bike a 100mm stem will usually work nicely for me as I don't like to be too stretched out, even though I ride in a low(ish) position.
As for head tube angle, I'm looking for something moderate, 73 degrees or so, so the bike doesn't act too twitchy.
Then with this informantion I start to look at geometries to find the right frame. The more info you have, the better the bike will fit you.
The worst way to buy a bike is to go to a bike store and decide to buy based on looks and price range, then trying to find the right size on the bike you have already decided to buy.
 

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Discussion Starter · #8 ·
I know some of my fit specs and "some" of my preferences.

Seat height is 70-70.5 cm .
Setback is 5.
Handleabr drop has been 5 and
Reach (tip of sadlle to center of bars) has been 51-52.

I've been playing around with reach and handlebar drop. Not really sure where that should be. I'm pretty flexible/ limber (palms down on floor no problem). I am "older" but still race and regulalry do the hard local training rides (which are 45- 50 miles and ave 24-25mph+-).

I'm 5' 8-1/4" with an Inseam of 80cm. So I have a "short legs/ longer torso" physique. My arms are not all that long (not sure the length off hand).

What I was riding had a STA of 74 and a TT of 52.7
I was looking at the R3's (51 and 54) which have STA's of 73 and TT's of 53 and 54.5 respectively. I have test riden both.

Thanks to C-40 I know the following to be true:

Relative to my current bikes fit the 51 has a shorter TT by 7mm and the 54 would be longer by 8mm. Thus my question. I'm smack in the middle (fit wise).

I supposed HT could be a factor (12 on th 51 and and 16 on the 54). I don't know if the larger frame handled/ felt all that different than the 51. With the 51 I had 25 mm of spacers on the stem on the 54 is was on top of the headset but the FSA headset was about 20mm high on the 54(on the 51 it was only 5 or 10mm in height).

The way cervelo has built the frames the rear triangle geometry is the same as is the STA and HTA. As relates to my fit this makes this is about the front end (TT length).

You can see, as far as TT and my fit is concern I'm in the middle.
 

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C-40 said:
You didn't mention the frame sizes, but 120-130 stems are most often seen on larger frames and 100-110 on smaller ones. There is no rule that says you can't use a 100mm stem on a 60cm bike. I've been using a 120mm on a 51cm frame with short reach (70mm) bars. My other frame has a 100mm stem with standard (85mm) reach bars. Both handle just fine.
Ya know... I've been pondering this phenomenon, and wondering why it is the case.

Presumably, there is a range of stem lengths that will work pretty well with bars of certain reach. If a stem gets waaaay long, then steering can get slow, plus there are strength concerns. If a stem is too short, then steering can get twitchy (or so I am told, although all my stems are pretty long).

But why the large frame/long stem and small frame/short restrictions? Seems to me that the effect that stem length will have on handling is independent of frame size. It also seems to me that opening up different sized frames to the whole range of useable stem lengths would allow folks to tune their fit setup more finely because they'd have one more variable they could tweak in the search for the perfect riding position.

The current situation is probably driven by economics. Bike companies like the one frame size/one stem combination for its simplicity, so they design top tube length/stem length combinations to fit the middle of the bell curve for the people who are likely to be riding any given frame size. Make sense, I suppose, but I also encourage people to look at the possibility of putting on a stem of significantly different length than the OEM stem if it helps them get comfy.

Probably Stating the Obvious,

- FBB
 

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simple answer..

I really don't see the problem. Based on your short saddle height, the 51cm is the obvious choice. The seat tube length on the 54cm is too long for your saddle height and so is the head tube (140mm not 160).

You haven't mentioned stem length or angle in your fit measurements. Your handlebar drop is very conservative, so you really should be using a 90 or 96 degrees stem to reduce the spacers.

If you get an R3 with a True Temper fork, the max. height above the top of the head tube is 40mm for the headset top section and spacers combined, plus 40mm for the stem.

FWIW, on the R3, with a 72cm saddle height, I have 30mm above the top of the head tube (including the headset top section) with an 84 degree by 110mm stem. The drop from saddle to bars is about 9cm. If you used a 96 degree stem, you'd have about a 5cm drop.
 

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Discussion Starter · #13 ·
Stem length and angle

Thanks C40

My stem is 120mm with a +-6 degrees.
I put 25mm of spacers on top of the headset
and had the stem angled down.

Seems to be working for the 5cm drop I have been using.

Not sure if the 120 stem is too long for me but have been using it for about a month.

You're right about the R3 54's head tube being 14 cm I had inadvertently measured the next frame up.
 

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long torso..

One of th eproblems is you've got a long torso. You're about 5cm taller than me with a 2cm lower saddle. The Cervelo is designed such that a long stem will be required. Another thing to keep in mind is that the wheelbase and front-center are very short. To keep the same weight balance, you may want the saddle at 5-10mm further back, whihc would take care of the reach problem.

If I understand your response, you've got a -6 (84) degree stem with 25mm of spacer, but with what HT length and headset top section length? The R3 can have a maximum of 4cm under the stem, in any combination of headset and spacer. That's according to the True Temper fork instructions. The epoxied in place aluminum support sleeve must extend below the top headset bearing. If more spacers are used, the steerer won't be supported in a critical area. You should seriously consider a higher rise stem and use fewer spacers.

Nothing wrong with a 120mm stem for a long torsoed rider. At the worst, the R3 might require a 130.
 

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smaller frame

means lower bar height unless you can stand tons of stack or upturned stem. UGLY in most cases. also means longer seatpost.
I agree with the rest, keep shopping find one that fits. Finally are you between measurements or sizes? because if you are between sizes (Compact) say a M and a L then by a frame sized by measurements
 

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not so...

I don't think you've been following the thread very closely. Until the poster states his HT length, it's too early to make any definitive statement about this frame's suitability.

Also, you're confused about sizes and measurements. A size is a measurement, so your statement really makes no sense. Cervelo uses sizes , like the 51cm and 54cm being discussed. Even though there is a 3cm difference in the listed "size", the head tube and seat tube only differ by 2cm.

Other brands like LOOK use both a c-c frame size and a letter designation. I don't see any value in calling a 51cm an S or a 53cm an M. The letters don't mean a thing.
 

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I didn't see mfr nor size (so I guess I wasn't)

and I wasn't clear. some bikes are measured by measured size, some by S,M,L,XL (common in may compacts) so what I was saying is if this was his frame sizing choice and niether fit, find an MFR with measured sizes where there are slighter differences. Is that clearer? So what I was trying to say is some Mfrs size by measurements and some by simple letter sizes which have usually less options in regards to fit.

yes I missed the R-3 with the 51 and 54 measurement. sorry for my response from skimming.
 

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Discussion Starter · #18 ·
HT height

C-40 said:
One of the problems is you've got a long torso. You're about 5cm taller than me with a 2cm lower saddle. The Cervelo is designed such that a long stem will be required. Another thing to keep in mind is that the wheelbase and front-center are very short. To keep the same weight balance, you may want the saddle at 5-10mm further back, whihc would take care of the reach problem..
How would being 5-10mm further back affect my peddle stroke relative to KOPS? (Right now I have my saddle set back 5mm relative to KOPS). Would I need to adjust my seat (lower it) to compensate for being further back to keep/ make all things equal?

If I understand your response, you've got a -6 (84) degree stem with 25mm of spacer, but with what HT length and headset top section length? The R3 can have a maximum of 4cm under the stem, in any combination of headset and spacer. That's according to the True Temper fork instructions. The epoxied in place aluminum support sleeve must extend below the top headset bearing. If more spacers are used, the steerer won't be supported in a critical area. You should seriously consider a higher rise stem and use fewer spacers..
Yes this is correct. -6 (84) degree stem with 25mm of spacers.
Interestingly the 51 R3 I demoed had an Ouzo Pro fork which is also what I am currently using. My HT is a 12 (same as the 51 R3) with the 25mm of spacers on top of a (I think) 10mm top headset bearing. Pretty sure this is well within the specs for the Ouzo Pro.

Nothing wrong with a 120mm stem for a long torsoed rider. At the worst, the R3 might require a 130.
That's worth noting. I doesn't really bother me but I sort of wondered if it was getting a near some limit that might be considered "too long" on a "small" frame. Then again after looking at some of the pro riders in europe, they seem to have very long stems!!
 

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don't see any problem...

Sounds like the R3 should fit with a 130mm or even a 120 if you move the saddle back. When you move the saddle back, lower it 3mm for each 10mm of saddle movement.

The other thing to try is more drop. As I noted, 5cm is very conservative and creates the need for a longer stem. Just lowering the bars 5-10mm would help you stay with a 120mm stem.
 

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This discussion is interesting to me because I have the short inseam for my height thing too. When I bought my Trek 5200 the LBS said I actually need a 52 for my inseam and a 56 for my torso. Since that combination wasn't an option without going custom built frame, they recommended I go with a 54 and run the saddle a little lower and use a longer stem. They said that this would hinder my ability to get aero a bit but I'm not too concerned with that at this point, it's still an improvement over doing the road trips on my mountain bike like I've been doing.
 
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