Chainring Setup For Cross

Pross

I'm hopefully going to be getting a cross bike soon and it will probably double as a commuting bike. However, as I intend doing cross racing on it am I best off with a 46 / 36 cross chainset or normal 50 / 36 compact? My most likely bike choice is a Dolan Multi X but I'm also considering a Caad X or Ridley X Bow (all Sora versions) so opinions on those three would be welcome. Thanks.

mentalalex

You won't need the 46 or 50 in the CX you will just stay in the 36

I ran 42/34 for Nationals/World cups and never ran out of gears but when On road training the 42 was to small but 46 would be more than fine for commuting .

petemadoc

Most race bikes seem to have a 46/36 for cross

Personally I run a 50/34 standard compact chainset, it works well for me as I use the bike for commuting and wet road rides too. 34 seems to work fine on most muddy cross courses and I have a wide enough ratio cassette 27-12

Horses for courses I suppose. Interesting to hear someone more serious than me running 34, I always though it was lower than normal.

mentalalex

I found the 34 very usefull for short steep stuff which enabled me to ride things where others couldn't.

Didnt use it loads but when i did it was very useful.

liamcorrigan

I'm hoping to try cross this year and am in the process of building a bike. I have a 44/34 chainring which I was planning to run with a 12-27 cassette. Does this sound about right?

xixang

I used to run 38/48 and never really used the 48. Now I'm older I've moved to 34/48 with 12-25 sprockets, but effectively single ring 34 (no front mech - 48 is chain keeper with dog fang inboard). I find this a double advantage - lower gearing if needed and for most of the time the rear mech is well clear of rear wheel. I've had a few wrecked mechs/wheels when clogged up twigs have fouled spokes.

Never felt undergeared in vet races but suspect I would be if 20 years younger/stronger and racing with seniors

imposter2.0

mentalalex wrote:

You won't need the 46 or 50 in the CX you will just stay in the 36

I ran 42/34 for Nationals/World cups and never ran out of gears but when On road training the 42 was to small but 46 would be more than fine for commuting .

Another vote for 42/34 - I used this last season with 12-26 and never needed anything bigger, or smaller. As for using it on a road commute - it depends how fast you want to go, I suppose...

simon_e

46 is fine on the road, probably better than a 50t most of the time and not much lower.

Surely a wider range cassette would make sense too - you're either riding slowly through gloop/round the poles/up a bank or wanging it down the other side, and the fewer shifts you need across to get to a useable ratio the better. I'd be tempted to try a single front ring (as used by Louise Robinson and Isla Rowntree) and a 11-32 on the back.

CX tyres will also raise the gearing slightly compared to road tyres.

milese

34/48 here and I dont think I ever change into the 48, unless there is a long straight decent with good surface and they dont seem to exist, with a 12-27 cassette.

I'm not exactly a decent 'crosser though!

Paul 8v

I rode my first race last night, didn't get in to the big ring once!

Pross

I've ordered a CAADX Sora which comes with 46 / 36 as standard and a 12 / 26 cassette. I'll see how I get on with this, I may get a 12 / 28 cassette. I think when I last rode cross 18 years ago I had a 48 / 36 but as others have said I doubt the big ring will get much use. It will probably take me a season to get to know the local courses and then I can change the little ring if I need to but I'll probably end up with a couple of cassettes in any case. Thanks for all the replies.

imposter2.0

You going to Llantarnam? It's a flat circuit. The only elevation per lap is down/up through a ditch - which is ridable if you can get a clear run at it. The other bit is up a bank near the finish, but there is usually a hurdle half-way up there anyway, so most people run it.

Pross

Hoping to, it's only about 2 or 3 miles from home for me. I watched it last year and it looks a decent course for someone who can't climb (i.e. me!). Depends on if my company pull their finger out and approve my cycle to work voucher so that I can get my bike in time but might just do it on my old MTB otherwise. I'm even more rubbish at cross than I am on the road so should be fun! :shock:

Pooter

If you want to trouble the top half of a race you really need to be spending almost the entire race in the big ring, so choose something you can push - 44 or maybe 42. The little ring is just a bailout gear for courses with big hills/banks

milese

Pooter wrote:

If you want to trouble the top half of a race you really need to be spending almost the entire race in the big ring, so choose something you can push - 44 or maybe 42. The little ring is just a bailout gear for courses with big hills/banks

I suppose that depends on the standard of the field and the course.

On Sunday I didn't leave my 34 ring for the entire race and I finished 21st out of 60 starters.

My average speed was 13mph and I did 10 laps in the hour, so 6 minutes for a 1.3m lap travelling a total of 13 miles.

I got lapped by a couple of the top riders with a lap or two left, so if they did 13 laps they'd have travelled 14.3 miles, and averaged 14.3mph.

So I dont think that you need to be in the big ring for virtually the whole race to go 1.3mph faster, and that would be too win. This was on a very dry course, with me being technically poor and the field included the national champion and the SW champion, neither of which won.

So my advice is; if you are inexperienced enough to need to ask the question about gearing, dont be intimidated into not having easy gears. It is of course horses for courses and everyone will have different preferences, but for me and my last race the 34 was fine. I think it would be better for me to get a 36 instead of the 34 and spend the whole race in that, than to worry about about the size of my big ring and try to ride it.

Pross

The only way a gear set up will get me into the top half of the field is if it links to an engine and even then my technical skills will let me down!

FransJacques

One thing I'd say is don't go too small at the front, 38 if you have a 130 BCD or 36 is you have a 110 BCD.

I think bigger front rings "roll" better and you can get a better rhythm going, it's just a feel thing. For the same gear inches, a 53x19 feels better than its 39 tooth equivalent. I bet this is why a lot of guys cross-chain (i.e. big-big combos).

So a 25 tooth for cross is poor, you need a 27 or 28 which are widely available.

Pross

Cheers. I'm hoping the shop will swap out the standard issue 12 - 26 for a 12 - 28.