Discussion
I'm looking for a little advice on gear ratios. I've sold my mountain bike and road bike, and I'll be picking up a cyclocross bike at the weekend. I'm pretty sure it will suit the riding I've been doing recently which is a combination of road and toe path type stuff. Anyway, the plan is to run the bike with the standard wheels and 35c tyres on when I'll be doing a combination of surfaces and if I plan on doing a longer ride on the road, I'll swap to a set of lighter wheels with 23c slicks.
The bike comes with a 46/36 crankset and a 12-25 cassette which I think will be bob on for the off road/combination stuff. But for the road work I think I'm going to need a smaller cog on the rear to give me a slightly higher top speed. My old road bike was a triple (never used the granny ring) - 50/39 and 12-26. The top end with that ratio was just about OK for me but I felt like I could maybe do with an extra gear or two sometimes when climbing.
Anyhoo, I plugged some numbers in a speed calculator and it looks like an 11-25 on my cx will get me about the same ratios as my old road bike. Do you reckon it would be worth going for an 11-28 instead to give me a little more help on the climbs? In the past I haven't thought about ratios and just ridden what I've got and I have no real knowledge on the subject. I don't really want to swap the chainrings around for now.
This is my old road bike on the left and cx on the right with 11-25. Below is the cx with 11-28.
The bike comes with a 46/36 crankset and a 12-25 cassette which I think will be bob on for the off road/combination stuff. But for the road work I think I'm going to need a smaller cog on the rear to give me a slightly higher top speed. My old road bike was a triple (never used the granny ring) - 50/39 and 12-26. The top end with that ratio was just about OK for me but I felt like I could maybe do with an extra gear or two sometimes when climbing.
Anyhoo, I plugged some numbers in a speed calculator and it looks like an 11-25 on my cx will get me about the same ratios as my old road bike. Do you reckon it would be worth going for an 11-28 instead to give me a little more help on the climbs? In the past I haven't thought about ratios and just ridden what I've got and I have no real knowledge on the subject. I don't really want to swap the chainrings around for now.
This is my old road bike on the left and cx on the right with 11-25. Below is the cx with 11-28.
gazza285 said:
My cross bikes have a 30-11 cassette and 36/46 at the front, never felt under or overgeared at that, but I do live in the Pennines, so you might not need to go as low as mine. 46-12 or 46-11, I doubt you'll notice a big difference in the real world.
Ta. I think I'll probably go for the 11-28.Disco You said:
If 39/26 was fine before, why do you want to move to 36/28?
As I said above, it's OK but sometimes I feel like an extra gear or two would be useful. I suppose at the end of the day, cassettes aren't expensive and I'm probably over worrying it.Looking at cyclocross bikes recently, some seemed to have what looked really odd gearing (to me) - what is the philosophy behind having a relatively large inner chainring? I'd assume you'd want something like a compact with a 28-tooth biggest ring on the cassette, or is there no climbing in proper cyclocross racing?
Back on topic, how many gears is your cassette? With a 36-tooth inner chainring I'd want to go up to 28-tooth on the rear; but you don't want to have too large a gap between ratios so might be worth compromising by going for 12 rather than 11 at the top end. 46/36 is going to provide quite a lot of ratio overlap.
ETA: just opened up my own gearing spreadsheet and realised that I'd added the Decathlon BTwin Cyclo-X to it - that has a 46/36 chainring and 11-28 10sp cassette (I believe) and still looks compromised for climbing.
Back on topic, how many gears is your cassette? With a 36-tooth inner chainring I'd want to go up to 28-tooth on the rear; but you don't want to have too large a gap between ratios so might be worth compromising by going for 12 rather than 11 at the top end. 46/36 is going to provide quite a lot of ratio overlap.
ETA: just opened up my own gearing spreadsheet and realised that I'd added the Decathlon BTwin Cyclo-X to it - that has a 46/36 chainring and 11-28 10sp cassette (I believe) and still looks compromised for climbing.
Edited by Jobbo on Thursday 19th September 15:34
gazza285 said:
The reason behind the usual 36/28 combination is that if you go any lower you are faster running with the bike on your shoulder. Also you need to remember that most climbs in cyclocross are limited by grip, not gearing.
On another thread...TwistingMyMelon said:
Theres never a time when it is better walking than riding a hill, this is a cycling forum not Mumsnet!!!!!
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