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What is the fit difference between a cross bike and a road bike?

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What is the fit difference between a cross bike and a road bike?

Old 09-07-15, 05:21 PM
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volosong
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What is the fit difference between a cross bike and a road bike?

Just purchased a cross frame and the shop has offered to build it up for me. This is my first cross bike and before I have him order parts, I need to know the difference between a fit done on a road bike and a cross bike. A Specialized Body Fit on my road bike has mitigated all pain I used to have. Are those parameters/measurements directly transferable to a cross bike, or is the riding position different? If it makes any difference, I will not be racing, but will use the bike for medium-length day rides, (about 20-60 miles), on gravel trails, specifically those in the 'rails to trails' system, and also other non-paved roads that I stumble upon in my wanderings. Do not expect to do any single-track riding with this cross bike. That's what my MTB is for.
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Old 09-07-15, 06:19 PM
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Based on how you will use it, the same, unless your road bike has the bars really low. If anything, a tad more upright, maybe swapping more reach for less drop to make out of the saddle handling easier. Within a stem-swap difference.
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Old 09-07-15, 07:28 PM
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Originally Posted by catgita View Post
Based on how you will use it, the same, unless your road bike has the bars really low. If anything, a tad more upright, maybe swapping more reach for less drop to make out of the saddle handling easier. Within a stem-swap difference.
Thanks. Bar drop isn't anything drastic. Only about 5" or 130mm, (top of seat to center of bar). Good to know everything else will go across.

If I can ask a couple other questions.

1.) for my intended usage, 50/34 or 46/36? I was going to go with Ultegra 6800 11/32 on the back.

2.) this is a newbie question . . . SPD-SL or SPD?
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Old 09-08-15, 10:18 AM
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Originally Posted by volosong View Post
Thanks. Bar drop isn't anything drastic. Only about 5" or 130mm, (top of seat to center of bar). Good to know everything else will go across.

If I can ask a couple other questions.

1.) for my intended usage, 50/34 or 46/36? I was going to go with Ultegra 6800 11/32 on the back.

2.) this is a newbie question . . . SPD-SL or SPD?
Your contact points should stay roughly the same as on your road bike. Maybe slightly more upright, as @catgita said.

1) 50/34 has a wider range, but some folks feel like the 50 is too big and the 34 too small.
46/36 has a tighter range so you spend more time in the middle "sweet spot", and is more of a "racer's" crankset.

I use a 50/34 on my cross/gravel bike, with an 11/34 cassette. I'm #225 and I ride lots of rolling hills, so I like the wide/low gear range. You need to figure out what low and high gearing you need and buy the appropriate crankset/cassette combo.

2) SPD-SL vs SPD is a question of preferences.
Do you already have one system or the other on your bikes?
Or, do you intend to buy shoes specific to each bike?

SPD:
+ walkable cleat
+ mud-shedding pedal clips
- heavier
+/- more float (some like it, some don't)

SPD-SL
+ lighter
+/- less float
- non-walkable shoes

I prefer SPD because the cleats don't protrude so the shoes are more walkable. I have SPD shoes I wear all day at work, and various SPD pedals on my 4 bikes.

SPD-SL shoes make you walk like a hooved creature, and require cleat covers.

Some folks think they need the more secure, less floaty contact of SPD-SL cleats. They're the more "racer" option, along with other, similarly non-walkable cleats (Time, Look, etc)
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Old 09-08-15, 01:53 PM
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Originally Posted by volosong View Post
1.) for my intended usage, 50/34 or 46/36? I was going to go with Ultegra 6800 11/32 on the back.
A 32t cog may work with a 6800 RD, but it's technically bigger than the specified max. Success will depend on your dropout and RD hanger geometry.

2.) this is a newbie question . . . SPD-SL or SPD?
Road cleats and pedals usually don't like dirt/sand/mud. Put a foot down in the dirt with SPD-SLs and you may or may not be able to clip back in. Also, depending on where you ride off-road, you may encounter places where you have to dismount and carry the bike. Climbing up a slippery, muddy creek bank in MTB shoes is hard enough -- I'd hate to try it in road shoes.
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Old 09-08-15, 02:17 PM
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Originally Posted by Kopsis
A 32t cog may work with a 6800 RD, but it's technically bigger than the specified max. Success will depend on your dropout and RD hanger geometry.
The 11-32 is an Ultegra 6800 specific cassette. The 6800 RD comes in two flavors, the normal short cage and a mid cage. The 11-32 will only work with the mid cage. One of my road bikes is set up with these components. Works well.

Originally Posted by Kopsis
Road cleats and pedals usually don't like dirt/sand/mud. Put a foot down in the dirt with SPD-SLs and you may or may not be able to clip back in. Also, depending on where you ride off-road, you may encounter places where you have to dismount and carry the bike. Climbing up a slippery, muddy creek bank in MTB shoes is hard enough -- I'd hate to try it in road shoes.
Good info. Again, my intended purposes are gravel 'rails to trails' paths. In the semi-arid West. Don't expect to run into any mud or 'slippery slopes'. However, you bring up a good point in walking on SPD-SL shoes. Doesn't work well, and I expect that if I do get into very long distance trail riding, such as a multi-day camping trip via bike, that I'd very much welcome SPD shoes. Thanks for the recommendations.

You too, Tim-Iowa. I'll probably go with the 50-34 to get the low gears. Like you, I need all the help I can get when the road goes vertical. All my road bikes, except for the TT bike, are 50-34. I'd like the option to switch wheels so that I can use the bike on asphalt. A 46-11 would probably be a tad too low when the road slants down.
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Old 09-08-15, 02:19 PM
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With classical CX bikes, the rule of thumb is to buy a CX bike one size smaller than a road bike to compensate for the higher bottom bracket.

With today's gravel road/adventure bikes, that isn't an issue and the fit is the same as for a road bike.
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Old 09-08-15, 02:20 PM
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These comments are generalities that I've gleaned from owning three CX bikes and a handful of road bikes. Also, I've talked directly with one manufacturer about the sizing of their CX bikes. Basically, the CX frame a uses different geometry than a road bike in order to gain more bottom bracket clearance as well as a more upright riding position. The top tube is usually shorter, the head and seat angles are different, and the forks and stays are designed to allow for wider tires. The biggest consideration for me was the frame size (seat tube center-to-center) - most experts recommended a frame size two centimeters shorter than what my road bike would be (remember, this is a generalization - each bike has its own geometry). I ride a 58cm road bike, but I ordered a 56cm Cannondale CAADX, and it fit perfectly. I also tried a 58cm and a 56cm Surly CrossCheck, and the 56cm fit the best (the 58cm top tube was all the way up to my crotch). I also ride a 60cm road bike that is a bit large for me, but I've changed the stem and adjusted things on it so it feels perfect. For most of us, I think a frame that is a little large is workable with some mods, but I found that a smaller frame than what I ideally need is more difficult to get right. At any rate, every new bike is going to need to be dialed in.

As far as gearing, my CX bike has 46/36 in the front and an 11-28 11-speed in the rear. That works really well for my gravel grinding and commuting. For pedals, I definitely agree on the SPD-style. I use those on my road bike and CX bike.

Have fun with the project!
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Old 09-08-15, 03:09 PM
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For typical commercially-available cranks (SRAM, Shimano, FSA), you can easily make a 46/34 by swapping the little ring on a 46/36 'cross crank. This is, IMO, more useful than a 50/34 for mixed-surface riding as the 46t big ring allows for comfortable spinning from about 12-30+ mph, and the 34t only gets used when spinning up a steep hill. The 50/34 will result in more front shifting when riding around 14-16 mph, which is a "normal" speed for a gravel road/bath/rail-trail (for me anyway). With a 35c tire, you won't spin out a 46/11 big/little combo until well above 30 mph, so it is more than sufficient for fast downhill riding.

Personally, I run a 46/30 and 11-36 cassette, which allows for comfortable big-ring spinning from 10 mph to 33 mph (where I spin it out), and comfortable little-ring climbing from 4 mph to 12 mph. But, the hills around here are very steep - the combo is great where you grades range from +30 to -30%, but may be a tad bit too wide if the steepest hill you ever go up or down is a 10% grade (most rail trails have grades in the 5% or less range).
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Old 09-09-15, 11:30 AM
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How your CX bike fits will be a function of its intended geometry. My two CX bikes (Specialized Tricross Sport, Ridley Crossbow), though set up similarly, have substantially different ride qualities and handling characteristics due to their geometry designs. The Ridley has a higher BB, shorter TT, and shorter CS, which, perhaps in combination with differences in HT and ST angles, make for a more responsive and spirited ride compared to the Tricross.

I run a 46/34 x 12/30 with 700x42c tires on my Ridley and it gives me a good cruising gear range on flats and a low enough granny for 90% of the offroad situations I encounter. The jump between 34t and 46t (compared to a jump to 50t) feels very natural for trail riding. Also, the combination of having a 46t big ring and a 12-30 cassette also reduces cross-chaining; I used to have a 11-28 with the same crank and I am much happier after trading the 11t for a 30t.
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Old 09-09-15, 02:52 PM
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Originally Posted by volosong View Post
Just purchased a cross frame and the shop has offered to build it up for me. This is my first cross bike and before I have him order parts, I need to know the difference between a fit done on a road bike and a cross bike. A Specialized Body Fit on my road bike has mitigated all pain I used to have. Are those parameters/measurements directly transferable to a cross bike, or is the riding position different? If it makes any difference, I will not be racing, but will use the bike for medium-length day rides, (about 20-60 miles), on gravel trails, specifically those in the 'rails to trails' system, and also other non-paved roads that I stumble upon in my wanderings. Do not expect to do any single-track riding with this cross bike. That's what my MTB is for.
I'm surprised you've already made the purchase. Seeing that your questions are about fit. Not much to be concerned with though I think working out your stack height could present specific challenges. Most adventure/gravel bikes have a taller headtube and forks that can accommodate wider/taller tires. Both qualities have the effect of "lifting" the front end. I would have the bars positioned to mimic your road position but have the fork steerer-tube left a little long. You may need some time to sort out just the right combination of spacers that will go with your new riding position.
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Old 09-09-15, 04:10 PM
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I'm liking the 46-34 talk. That sounds like a nice rig combined with the 11/32. That's easy enough to do with the new 6800 Ultegra bolt pattern. It's about time they standardized on one measurement.

'cale', On purchasing it now instead of later. I purchased a Pinarello FCX and it only comes in four sizes. I got the largest size and the next smallest is really too small for me. I'd be too scrunched up on a 55.5 cm top tube. All my road bikes are either 58 or 59 cm. This FCX is 58 cm. There are no Pinarello dealers anywhere close to me, and none of them stock the FCX. Whoever I purchased it from, it would be sight-unseen. I finally found a dealer in Oregon who would order it for me, and good thing I did because, as mentioned in a different sub-forum, it was the last frame of that size at the national distributor. I'll take your advice and not cut down the steerer tube until I've had a thousand miles or so on it.

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Old 09-14-15, 12:52 PM
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I find that I like the bars a smidge higher, but further, on my cross/gravel bike. So, saddle to bar drop on my road bike is about 3", about 2.5" on the cross bike, and reach is about .5" closer from nose of saddle to center of bar clamp on the stem on the cross bike - but the saddle is also longer on the cross bike too. So, I guess I have more room to play with on the cross bike than on the road bike, which I like because I shift a lot when climbing/descending steep, loose gravel. It also gives me a little more flexibility for longer rides too.

Gearing wise, I ride 46/34 with 11-36 - but my cross bike replaced my MTB too... so I ride it everywhere. 11-32 would be my go to if I rode a little more road and flatish gravel. I geared it to ride up some pretty steep stuff on and off road. I didn't want my riding to be limited by my gearing. I think I will be switching to 48/34 in the front soon, I would like just a little more gear for flat/downhill. I cruise in the 15t cog on flats, which only gives me the 13 and 11 before I am spun out. I guess with knobbier tires it might be different, but I would like to ride a little further towards center cassette than I do now.

Pedals/Shoes - SPD for me! Some of the SPD pedals are not significantly heavier than SPD-SL pedals. The A600, single sided SPD road pedal is only 20g heavier than Ultegra carbon pedals. Not enough to notice for me. That said, single sided pedals for offroad use are probably not ideal. I like the M530 - cheap, reliable, and has a nice smallish platform around the bindings. Not unreasonably heavy either.
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Old 10-06-15, 05:45 PM
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Originally Posted by volosong View Post
I'm liking the 46-34 talk.
The 34-32 on my bike can get me up some STEEP dirt climbs. There's a permanent cross course near me (Riverpoint Park in West Warwick, RI) that has a couple of steep spots where this gearing is perfect. I also use it in spots when I lap a local state park (Lincoln Woods). It's just good to have it there as a bailout gear and the bike is still useful as a winter/rough road beater. Plenty of gear range with the 46/34--12-32 for me.
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