# Cyclocross Bike Fit Question



## dgearhart (Mar 21, 2008)

I am 5'11" with an 84cm inseam (official cycling measurement to bone). I ride an Orbea Orca 57cm which leaves me very stretched out. I am really a 56cm, but I didn't want to go 54cm on the Obea. I am a Cat 4/5 road racer, so I don't mind being stretched out for my road bike, but I would like something less aggressive for my first cross bike. I plan on doing 1 or 2 cyclocross races a year in mainly dry conditions in Atlanta. Then, I'll mostly use it as a winter training bike.

Question: 

1. Am I too big to get a Scott Team Cyclocross size Medium with compact geometry 52cm C-C / 56cm C-T / "sloping" Eff Top Tube 53cm? (A size Large is 54cm C-C/58cm C-T/ 54.5 sloping Eff Top Tube)

2. What about the same question with a 54cm Orbea Cyclocross with a 54cm C-C / 58cm C-T / 54cm Top Tube?


I'm asking because I can't seem to find any LBS with cyclocross bikes in stock....I know fit is very important, and it is hard to suggest based on this post, but please provide any info based on your own experience with either bike and your own measurements. 


Thanks,
Dave


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## vanjr (Sep 15, 2005)

Great question. No bike shops carry cross bikes anywhere near me and the few that do carry any in far off towns don't have a wide range of sizes to try or more than a model. Big problem with no solution that I know of.


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## MIN in PDX (Nov 29, 2007)

My cross bike is 56 cm TT with a 11cm stem and I am the same height as you with 32.25" inseam. I was fitted professionally.


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## stwok (Mar 15, 2007)

dgearhart said:


> 2. What about the same question with a 54cm Orbea Cyclocross with a 54cm C-C / 58cm C-T / 54cm Top Tube?
> 
> 
> I'm asking because I can't seem to find any LBS with cyclocross bikes in stock....I know fit is very important, and it is hard to suggest based on this post, but please provide any info based on your own experience with either bike and your own measurements.
> ...


Check this 54cm Orbea out on Ebay, here's the link!


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## shomyoface (Nov 24, 2007)

Because of slacker/different ST and HT angles, you cannot compare TT lengths on a cross or road bike.


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## dgearhart (Mar 21, 2008)

*RE: Slack/different ST and HT Angles*



shomyoface said:


> Because of slacker/different ST and HT angles, you cannot compare TT lengths on a cross or road bike.


Thanks, I was beginning to think the same thing and have read similar thoughts from others on different threads. My gut says that if I am a true 56cm on a road bike, then I should be fine with a 54cm cyclocross bike assuming it has at least a 54cm C-T. It may be a little on the small side, but at least it will be lighter and easier to jump on and off during a race, right?

Thanks,
Dave


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## pretender (Sep 18, 2007)

dgearhart said:


> My gut says that if I am a true 56cm on a road bike, then I should be fine with a 54cm cyclocross bike assuming it has at least a 54cm C-T. It may be a little on the small side, but at least it will be lighter and easier to jump on and off during a race, right?


Your gut, and reasoning, are wrong.

"I would like something less aggressive for my first cross bike."

An undersized bike is a _more_ aggressive fit, because the handlebars are lower. It won't feel less stretched out than the larger bike.


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## dgearhart (Mar 21, 2008)

*Gut Wrong*



pretender said:


> Your gut, and reasoning, are wrong.
> 
> "I would like something less aggressive for my first cross bike."
> 
> An undersized bike is a _more_ aggressive fit, because the handlebars are lower. It won't feel less stretched out than the larger bike.


Good point! So, would you suggest that I should stick with a 56cm/55cm cyclocross bike? I am 5'11" with a 84cm inseam as measured with the book to bone approach.


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## pretender (Sep 18, 2007)

dgearhart said:


> Good point! So, would you suggest that I should stick with a 56cm/55cm cyclocross bike? I am 5'11" with a 84cm inseam as measured with the book to bone approach.


Size the cross frame same as a road frame is my advice. You can shorten and/or flip the stem to make the stance less aggressive, also set the saddle height a hair shorter.

Edit: Just to make clear, that is _my_ opinion and not universally shared. But I stand by the statement that moving to a smaller frame makes the stance more aggressive, all else being equal.


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## shomyoface (Nov 24, 2007)

Roughly speaking, one degree difference in ST angle equates to 1cm difference at the saddle. So if you are riding a 74 degree ST on the road, and get a 72 degree ST for cross, the same point on the seatpost would be roughly 2cms further back. BUT, because your actual position over the BB will be the same the TT actually means it becomes shortened. I ride a TT 58cm road and 59.5cm 'cross with a 1.5 degree difference in ST angle - thus, the TT length is roughly equal. 

The HT angle also is different but is lower in relation to saddle, so the change in cm's is less - plus because of the desire to be a little more upright, comes out in the wash.

Many folks end up getting a longer stem and pointing them up, to get the right position on the cross - this is mainly because of getting a to small frame size by equating road to cross, and, therefore, a lower HT. If they had sized up to acount for ST angle, they would have needed neither stem adjustment.


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## dgearhart (Mar 21, 2008)

shomyoface said:


> Roughly speaking, one degree difference in ST angle equates to 1cm difference at the saddle. So if you are riding a 74 degree ST on the road, and get a 72 degree ST for cross, the same point on the seatpost would be roughly 2cms further back. BUT, because your actual position over the BB will be the same the TT actually means it becomes shortened. I ride a TT 58cm road and 59.5cm 'cross with a 1.5 degree difference in ST angle - thus, the TT length is roughly equal.
> 
> The HT angle also is different but is lower in relation to saddle, so the change in cm's is less - plus because of the desire to be a little more upright, comes out in the wash.
> 
> Many folks end up getting a longer stem and pointing them up, to get the right position on the cross - this is mainly because of getting a to small frame size by equating road to cross, and, therefore, a lower HT. If they had sized up to acount for ST angle, they would have needed neither stem adjustment.


Excellent explanation which really helps me understand. I have one follow-up question. Since many of the Cross bikes out there use a sloping top tube, would that change anything noted above? I assume that the same principles are true exception that the sloping top tube results in a shorter tube length but similar "eff top tube" length. Is that correct? I ask because I noticed that the "eff top tube" on sloping top tube cross bikes is still shorter than most top tubes for similar size bikes where there is no slope. Thanks for the help!


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## bwcross (Sep 30, 2006)

shomyoface said:


> Roughly speaking, one degree difference in ST angle equates to 1cm difference at the saddle. So if you are riding a 74 degree ST on the road, and get a 72 degree ST for cross, the same point on the seatpost would be roughly 2cms further back. BUT, because your actual position over the BB will be the same the TT actually means it becomes shortened. I ride a TT 58cm road and 59.5cm 'cross with a 1.5 degree difference in ST angle - thus, the TT length is roughly equal.


Not sure I'm getting why there would or should be a difference in STA between one's road bike and cross bike.... and mountain bike for that matter. Which manufacturers spec out the same size cross and road frame with 2 degree differences in STA?


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## surfamtn (Aug 28, 2006)

I agree that having similar TT lengths from Road to Cross bike is the best place to start.

I agree with Pretender to play with the stem first.

But I see absolutely NO value in shortening the saddle height.

From there remember a few things:
-Yes the geometries are rather different
-Therefor the two bikes will feel DIFFERENT every time you go form one to the other. AND thats OK!!!

As a generality, measure your TT with stem length and consider it "reach". (factor in seat post and saddle differences if need be).
Then look at the drop from saddle to bar. Bar to ground is less helpful 'cuz the cross bike will sit higher of the ground.

What I shoot for is a similar "reach" measurement with the bars 1cm or so higher in relation to saddle on the cross bike.
Remember to look at (or feel) your saddle tilt when you move the bars up and down, as your sit bone angle changes and can change your perceived "pressure" on your hands.

Drastically down sizing the frame is asking for trouble.


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## pretender (Sep 18, 2007)

surfamtn said:


> But I see absolutely NO value in shortening the saddle height.


FWIW:

http://www.cyclocrossworld.com/Tech.cfm?Action=Edit&MenuKey=3&theKey=43&ShowDisabled=0

_Your saddle height on your 'cross bike can vary from the same as your road bike to 1 cm lower. Some people keep the height the same and let the higher stack height of mountain bike shoes and pedals provide the lower overall height. Because you're often riding on bumpy ground you'll spend a lot of time slightly out of the saddle. There needs to be room for your bike to "dance beneath you." I find that no more than 5 mm lower is perfect for most people._


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## CrankyMonkey (Jul 8, 2007)

Okay... So after reading this article: http://www.cyclocrossworld.com/Tech.cfm?Action=Edit&MenuKey=3&theKey=43&ShowDisabled=0 I'm wondering if I ordered the right frame. I ordered a 60 cm frame because the geometry was the closest to my road bike, TT being 600 where my road bike is 599. The STA on my road bike is 72.5 and the Cross Check is 72. The only major difference is the head tube which is 72 on the Cross Check vs. 74 on my road bike. I'm planning on running the same stem which is 110 mm with a 6 degree rise. I have my road bike setup in a pretty relaxed position compared to my buddies which all run with their bars lower then mine. The next size up is a 62 cm which TT is 610. Now I'm wondering if I should have gotten the 62 and then switched the stem out for something shorter. I could probably call and change my order. 

What do you think?


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## pretender (Sep 18, 2007)

CrankyMonkey said:


> Okay... So after reading this article: http://www.cyclocrossworld.com/Tech.cfm?Action=Edit&MenuKey=3&theKey=43&ShowDisabled=0 I'm wondering if I ordered the right frame. I ordered a 60 cm frame because the geometry was the closest to my road bike[.]


That is what the article recommends doing.


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## CrankyMonkey (Jul 8, 2007)

What I got out of the article is this... You should keep the size the same as your road bike but you want to have the ability to put your handle bars either even or slighly higher then your seat. The only problem I have with my road bike is that my seat post is pretty high, to the point that it's almost maxed out and I flipped the steam to compensate for the frame possibly being a tad on the small side. SO I think my road bike frame might not be a good benchmark since it's slightly too small. 

I called and changed to the 62 cm, I figure it's probably the right size and I can make better fit adjustments with the stem and seat post.


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## shomyoface (Nov 24, 2007)

For the OP, use effective TT, not the sloping of the compact frame, that screws up everything.

Also, a post above refers to "reach". This article on the link below really illustrates the important aspect of the right fit, and not relying to much on TT length etc....angles change everything. There are formulas to determine Stack and Reach, but I don't have one.

STACK and REACH


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## dgearhart (Mar 21, 2008)

*Question re: Article*

In the article inserted in the previous threads, it stated the following:

Bottom brackets on 'cross bikes used to be very high to allow for clearance when pedaling on the backs of pedals that had clips and straps. With clipless pedals, most 'cross bike bottom bracket heights have come down to that of a normal criterium bike. 

However, I have found that many bikes still have much higher bottom brackets. Is this a safe assumption?


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## MIN in PDX (Nov 29, 2007)

dgearhart said:


> In the article inserted in the previous threads, it stated the following:
> 
> Bottom brackets on 'cross bikes used to be very high to allow for clearance when pedaling on the backs of pedals that had clips and straps. With clipless pedals, most 'cross bike bottom bracket heights have come down to that of a normal criterium bike.
> 
> However, I have found that many bikes still have much higher bottom brackets. Is this a safe assumption?


We recently had an in-depth discussion of BB height/drop on the cross forum. Check out that thread. 

Most times, the BB drop is comparable to road bikes, with the median BB drop around 60 mm.


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