aaw

Greetings -
After reading all the excellent advice from folks on this forum across many threads about using a cross bike for a road bike, I'm giving it a try.

I love the bike as a cross machine (Cannondale SuperX). Now on to setting it up as road machine. I'm totally confused by all that I've read on gearing. Can someone give the general options/benefits or an "optimum" solution for combinations to use for road and cross?

The current set up:
- The bike has a SRAM Red 46/36 compact crank and rear 11/25 Shimano 10-speed 105 cassette (SRAM Rival groupo on the bike - seems to work fine if not the smoothest shifting).
- I plan to buy a second wheelset for road biking and can put any cassette on that makes sense.
- The teeth on the SRAM crank are kind of chowed, so if I had to, I could be convinced to also get a new crankset (ouch; unfortunately my budget is probably around 800 for the wheelset and any changes). For that matter, the Shimano 105 cassette is nothing fancy so I could change that if necessary. And might like to change over to a SRAM one someday for smoother shifting.

Although I'm looking for general information, I know someone will say "it depends". So specifics for me:

My goals: As a cross bike - ride aggressively in cross races (mostly flat), ride aggressively on many gravel roads around here (major climbs); As a road bike - keep up with fast friends on roads but generally not road races (some climbs), clip on some aerobars and race in triathlons (mostly flat).

Me: I ain't no spring chicken but I'm reasonably strong for a 40 year old mom and my riding partners all tend to be 10 years younger. I podium in Cat4 cross races and mountain bike races. I get left in the dust by Cat 1/2 cross racers, am about mid- to back-of-pack with Cat3. My strengths tend to be cranking on flats and hills. In the current configuration, I haven't shifted to my big ring much in races and so far I've found myself struggling a bit on the super steep sections of trails around here that get me to the gravel roads. I haven't done much road racing except as a triathlete (where I generally podium in my age group and place decently overall). When I'm road riding, I'm psyched if I'm maintaining 25 mph on flats - I can't go faster (or I couldn't on my Giant TCR2 with heavy wheels). I'm scared to go faster than about 38 mph on downhills. I have not even tried this new bike on the roads yet.

So, with that, what would be the best way to set up my bike for both road and cross. A single (I mean, not swapping out the double front rings) crank set combined with any combo of separate cassettes for road and cross?

Thanks in advance for all the great input from these forums!

Number400

You could get a decent used all road bike for your $800 budget. If you really desire to have an all in one setup, like you mentioned, get light road wheels and tires, figure out what cassette spread works best for you and leave everything else alone. I doubt you will need a bigger cog up front with your current top flat speed and downhill speed fears. Check out the Neuvation wheels, or even some Planet X wheels and you can easily stay in your budget.

Good luck!

flargle

I would suggest simply riding the 46/36 on the road for now, and finding out for yourself. You might find yourself spinning out on road descents, compared to people with true road gearing. I think 50/38 is a great gearing for road, especially with an 11t cog. But you may well find 46/36 works just fine.

aaw

Thanks for responses. And I just realized that the smaller ring has been swapped to a 38, so my bike is actually a 46/38, which explains a bit about why I found it reasonable to stay on that ring during a race and it felt a bit hard to pull steep hills. I think I should swap that down to a 36, and then get something like a 11-26 cassette on the road wheelset? Does that sound like a reasonable starting place for a road cogset combined with a 46/36 up front? I'm starting to grasp this all.

Kopsis

Start with the top end. 11t is the smallest rear cog, so with a 46t front you're at 110.3 GI which will get to about 33 MPH @ 100 RPM cadence. If that's not fast enough for the road, you'll need a bigger chainring. Since you say you spend most of your CX riding in the small ring, you could swap the 46t for a 50t (without changing your whole crankset) and add about 9% to your top end without having much impact on your CX riding. I'd probably ride with the 46t for a while and see how it works out.

As far as the road cassette goes, you say you'd like a little lower gearing for riding to the trails, so I'd suggest getting a lower range cassette for your CX wheels (maybe 11-28) and moving the 11-25 to your road wheels. That would give you 38 GI on the low end for the road setup (which should be fine unless you have some really steep climbs) and 33.9 GI on the CX (about a 12% reduction) and it will only change your lowest two gears.

Kopsis

I did my calcs before you posted about the 38t. Changes the low end GI numbers to 40.1 and 35.8 but still a 12% change. I wouldn't change the small ring. You've found a setup that works well for you as a 1x10 -- I'd try to keep it. Having to use that front DR is just one more thing that can screw up your race

aaw

Thanks for calcs, Kopsis. I think I am maybe understanding this better. I looked at Sheldon Brown's gear calculator to try to figure out where you were getting your GI numbers. I have a road bike that is geared 50/12 and 12-26. I've been happy enough with that.
@Number404, my theory is that for $800, I could add a nice road wheelset to my nice carbon cross bike, and come up with something much nicer than my current road bike (which I'm selling for around $400). Maybe you are right, and I should just invest $400 in wheels for THAT old road bike. But assuming I go $800 for new wheels/any gearing changes on my cross-bike, am I understanding this correctly?

I like the gearing on the road bike. The tires and cranks are the same on the two bikes (size-wise). So I can just divide the front by rear cogs to get my ratios? And if they are about the same, I'm good?

So old road set up: high = 50/12 = 4.16 Low = 36/26=1.385
current cross set up: high = 48/11 = 4.36 Low = 38/26=1.52

Does that mean my current cross high is higher than my old road high? In which case, I'm fine given my ninny-speed tendencies.
But then to get a lower low, I would need to go to a 27 (38/27=1.41) or 28T (38/28=1.36)for largest rear cassette cog?? If so, I could leave my front the same. My rear derailleur is a SRAM short cage, so max teeth it can take is 28T on the cassette.

If I am getting this right, that seems to make sense - change both my cross and (not yet existent) road wheelset to a 11-28 cassette and leave my front cranks the same. I get to stay in a single front ring while racing, but keep my old road gearing for climbs.

And yes, boy oh boy is it steep around here. One of my favorite rides is in Glacier National Park climbing up to the divide.... but I can do it happily on the the old road gearing of 36/26...

Thanks so much for all the input. I'd love to be told if a) yes, I'm getting this or b) I'm totally misreading the physics of gearing... I clearly should have done my PhD in physics or engineering.

fietsbob

My Road Cross and touring bike all have the same Triple chainring combo, 24. 40, 50 .

got off the band wagon before all the 11 and 10 speed cassettes hit the market ..
top gear a 13 in cassettes is harder to come up with .. Juniors racing restrictions make some available..

Bici bodhisattva .. dropped aggressive cycling long ago .. My knees thank me for that choice ,

there were other more agressive strivers . I let them go..

Kopsis

Yes.

Yes, just slightly. Not surprising - rule of thumb is that in your highest gear a 1t change in the rear is about the same as a 3t change in the front.

You got it. Though keep in mind that derailleur capacity does not tell you the biggest cog you can use. The formula is (big ring - little ring) + (big cog - little cog). A Rival RD has a 33t capacity, and (48-38)+(28-11)=27 so you're good.

I think you're getting the hang of it

aaw

Thanks again. I've gone from having my head spin reading so many threads to starting to get a grip on all this. I am deeply appreciative.
@Kopsis - ok, I see I need to think about both maximum cog size compatibility on my Rival short-cage RD (28t cog) and maximum chain wrap (33t), and if I go beyond this I need to either change my front ring or change to a medium cage derailleur [for anyone else looking at this: Rival medium cage has a max 32t cog, max 37t chainwrap]
@flargle - I chuckled at your post; good to keep in mind that the "perfect" gearing won't change the engine and its aging decline. But I got more involved in biking (from running) to *save* my knees! So for now, I'll continue with my (likely delusional) idea that I can maintain the bliss I derive from going all out for enough years to make all this thought process worth it.

Sincere thanks, all. Now on to investigating "Neuvation wheels, or even some Planet X wheels".

pmt

I would just leave it as-is; are you really outspinning the 46-11? Can you learn to cleanly spin faster? It's nice to be able to do road training and then just swap in the 'cross wheels to race.

FKMTB07

46:11 is about 27-28 mph at 90rpm. If you're outspinning that gearing, you're either a pro or need to work on your cadence. 120rpm should be a comfortable cadence that you could spin indefinitely (given an appropriate gearing, obviously. 46:11 at 120rpm is about 36mph).

Also, if you're regularly podium-ing in Cat 4 races, it's time to cat up. Nobody likes a sandbagger.

TommyBing

49/39, straight dope.

ambro

You might want to consider a 48/34 with a 28/11 in the rear. That combo will give you a very wide range of gearing and help with both fast road rides and steep hills. For CX racing - going from a 36 to a 34 in the front is not a big deal - as you could us the lower range of gears in your cassette to make up the difference. This combination is not optimal for serious road or cross racers - but I personally found it to be the most versatile for me. I live in a very hilly area in the NE, where the 36 wasn't cutting it on hills, nor was the 46 on fast group rides. This combo allows me to race cross and spend a lot more quality time on the road off season, w/o changing cranks.

Barrettscv 

+1

Finding a modern Crankset with 48 & 34 is almost impossible. I would change out the worn rings on your Sram Crankset with these from TA Syrius Chainrings from Peter White: https://www.peterwhitecycles.com/chainrings.asp

Just be sure to confirm compatibility with the seller before ordering.

rm -rf

I like Mike Sherman's Gear Calculator to compare different chainring and cog choices. All the charts change on the fly when the gears are changed, so it's quick to see what different choices will do.

(the linked pages pop up a message about the URL. Just click OK, it only is telling you that you can bookmark/favorite those settings)

Here's a link to your 46-36 and 11-25 gears.

Compare it to a typical 50-34 and 12-25 setup.

They both have similar top end speeds, but the 36 small chainring won't do steep hills as well, of course.

~~~~~~~~

Here's an example of the two charts on the page that are the most useful. (This is for a different bike, not your setup.) Big chainring in black, small chainring in red.

rm -rf

Are your chainrings actually worn? modern rings have differently shaped teeth to help with shifting. If the "worn" pattern repeats around the ring, then it's designed that way.

aaw

Thanks all.

I'm currently at: keep 46/38 for a while and see how it goes. I will keep my 11-25 on for CX racing; I just bought a second pair of rims (Rev30s closeouts!) and a 11-28 cassette for them. I figure I can use them for CX racing and triathlons (swapping cassettes back and forth once a year) with the other set of rims set up for either road or gravel rides in the off-seasons.

I may try a 48 in front if I need to (so, I'd be 48/38, much like the 49/39 recommended above). I realized putting a 50 on there would just increase likelihood that I could whack a root or rock with my front ring when out riding on gravel with the occasional single track section. And as someone said, I could still race CX with the 48 - which would mean not needing to swap rings around. I'll have to check out the TA Syrius Chainrings from Peter White; I know there are FSA rings that will work.

Honestly, I don't know if my rings are worn - they have some "shark fin" shaping going on - not in the actual shape of the teeth, but worn marks on the teeth. I have learned in the last 6 months that the "broken" teeth on my rings are supposed to be there...

Thanks for the link to Mike Sherman's Gear Calculator. I made a spreadsheet, but this is much better way to visualize the ranges. Thanks! Putting together my own gear spreadsheet was what made me realize I was unlikely to spin out a 46/11. I thought I had to go to a 50 to match my old road gearing, but I realize now the 46/11 is getting close. But yes, I could definitely use working on my cadence! Recognize, I have NOT ridden this as a road bike yet, so I don't really know what works/doesn't work. I just know I couldn't get up a few trails with the current gearing and there are steep roads around here.

I agree it is bad to be a sandbagger. So this year (my 3rd year of racing), I race with the "A" group instead of the "B" group (there is no women's masters category - I am no longer winning my beer cozy prizes). But for the UCI official races, I will race Cat 4 because I don't have enough points to cat up - those "B" wins didn't give me points. I'm slowly accumulating enough points that if I keep riding official Cat 4 races, I can cat up (if I don't age out of the sport before!). Women's racing is a bit different than men's racing. I find the distribution very bi-modal. There are women who try it out Cat 4 - so there are lots of Cat 4/"Bs". But then only the good ones stick with it, so there are a handful of really good Cat 1/2s. I can either be out in the front of the "B's" or back of the pack "A's". I end up racing some of the "B" men for motivation, because I'm right in the middle of the bimodal distribution. I wish more women raced!

fietsbob

Course Dependent, .. single ring setups work 42t , is a common choice,
and so there are guard rings made in that or 44t sizes ..


I got a nice one for my IGH bike to go with my 110-38t at https://www.cyclocrossworld.com/thorn...hainring-guard

road bike cannot you change stuff back on Mondays ?

Jiggle

Swapping rings is super easy. I'd just ride what you have and buy a 52t ring for group rides.

idc

Sounds good to me! I have 46/36 and 11-28 on my CX bike which is about as much range as I need for CX races or gravel. If you're going <40 mph downhill you don't really need a lot more. In commuter mode on the road I use my spare rear CX wheel which I think might be a 25 or 27 top, but that works fine. If I could only have one bike for both I'd consider a 48/36 with 11-30 in the back (Tiagra) or 12-30 (Ultegra). I think SRAM makes similar range cassettes too. I'm not 100% sure all RDs will work with 30+ teeth though.


Chainrings take some time to really wear out, afaik. And yeah modern ones have all sorts of ramps and pins on them to make shifting smoother.

Agreed! I have some friends in a women's team who race, and sometimes they get lumped all together in one race; sometimes even the Cat 4s get lumped in together with under 18 (unisex) races. I don't blame the organizers, but if there were more women racers they could ride their own race.

aaw

Yes, *one* could swap them back and forth; *I* however am unlikely to do so! I squeeze racing and training in around the fringes of working and parenting 2 small children. 15 minutes of bike dealing can make or break whether I ride that day.

Glad to hear support that my plan is likely to work! Has been weirdly fun geeking out on bike planning.

I'll come back here to repost how it works out. I love, love, love the bike in its current cross configuration. I'll report back on how it feels as a road bike; holding out hope that my wheels/cassette get here before the snow flies and the ice starts to set in... Thanks!

idc

I hear ya, I have two young kids and work full-time too. Swapping out wheels on a bike or even swapping which bike is out and ready to ride and which is in the garage is often as much as I can manage.

aaw

One of my secret motivations for wanting to combine my cross/road bike was that I'd only have 3 bikes to clean instead of 4! Less cleaning = more riding! (not sure that really works out though - I'll just have to clean one bike twice as often, but it *feels* less overwhelming!) Cheers to the parents of young kids who make it happen. (I'm proud to say that my 6 year old is asking for a cross bike for Christmas [which he will not be getting]).

idc

Yeah having a cross bike (and riding it in dirt/mud) necessitates lots of cleaning as it is

Let him wait a couple years and then get one of these bad boys: https://www.redlinebicycles.com/bikes...14-conquest-24