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Gearing + Cyclocross Bike

Old 07-27-10, 11:47 PM
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Gearing + Cyclocross Bike

I'm pretty sure I'd like to buy a cyclocross bike, but I have no idea what some of the specs mean. I recently injured my knee, so I'd like to have whatever will be easiest on my knee when climbing hills for example.

Someone mentioned that more gears or the way they're set up would help with that problem.

So which cyclocross bikes should I be looking at, or which number on the spec sheet should I be paying attention to. I've seen some with 18 gears, some with 24, and then there is another spec with 2 or 3 numbers like 43/36.

What should I look for or stay away from to avoid stressing my knees to the max?
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Old 07-28-10, 06:11 AM
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Ok. What matters is the size of the biggest gear at the back and the smallest at the front. You can change these to some extent, but the smallest front gears will only fit on a bike with triple from gears ("chainrings"). One of these will go as low as a 30 up front.

As a second best, a dual chainring bike that takes compact rings will go as low as a 34. If you needed a smaller chainring even than the 30 a triple can take then you could have a bike built up with a triple mountain bike crankset.

The rear gears (the "cassette") are easily changeable.

My advice would be order either a Kona Jake (the base model, not the Jake The Snake - only the cheaper model has the triple) or maybe the Tricross Sport Triple from a good store. Or find a store that orders and builds up Surly Cross Check frames, and have one built as a triple - maybe with MTB chainrings. Explain to them what you want and ask them to fit the most powerful hill climbing cassette. Also have the bike fitted with a fork mounted brake hanger or v-brakes and travel adaptors (either will improve the braking.)
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Old 07-28-10, 07:02 AM
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Originally Posted by MacAttack
I'm pretty sure I'd like to buy a cyclocross bike, but I have no idea what some of the specs mean. I recently injured my knee, so I'd like to have whatever will be easiest on my knee when climbing hills for example.

Someone mentioned that more gears or the way they're set up would help with that problem.

So which cyclocross bikes should I be looking at, or which number on the spec sheet should I be paying attention to. I've seen some with 18 gears, some with 24, and then there is another spec with 2 or 3 numbers like 43/36.

What should I look for or stay away from to avoid stressing my knees to the max?
The numbers '43/36' means the crank has a one 'gear' with 43 teeth and another gear with 36 teeth.

For the cassette on the rear of the bike you'll see something like this:

11/26 (which means the smallest has 11 teeth and the largest has 26 teeth) or somethings you'll see them listed out:

11/12/13/15/17/19/21/23/26.

The ratio of teeth on the front gear to teeth on the back will tell you how difficult it is to pedal.

When your chain is on the biggest gear (most teeth) in the front and the fewest teeth in the back it will be the most difficult to pedal. This is your biggest gear (biggest ratio.)

When your chain is on the smallest gear (fewest teeth) in the front and the most teeth in the back it will be the easiest to pedal.

If you try out a bike and you can't find a sweet spot to ride it because of knee problems you might want to use a touring gear setup. They have lower gears because they are designed for loaded riding.

So try riding a few of the popular touring bikes. If those still aren't good (low) enough you can swap out the gearing for even lower ones. For example:

https://www.amazon.com/Shimano-170mm-...dp/B001GSSGBK/

That will put you at a 22/32/44 on the front

and

https://www.bikeman.com/FW8091.html

which will give you:

11-13-15-17-20-23-26-34 on the back.

That's pretty low gearing and should be good for your bad knees.

Most bikes won't come with gearing that low. I would try to ride a touring bike first to see if those gears are low enough for you.
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Old 07-28-10, 08:26 AM
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Yea it's not how many 'gears', that's marketing ..the math of the ratios is what matters.
crank teeth, divided by wheel teeth, multiplied by wheel's diameter.. you may also multiply by Pi and then that circumference multiplied by cadence will give you Actual speed

when you chart out all the ratio combinations you will see there are ranges that overlap as the ratios end up being
nearly the the same.

[2:1 can be described in many combinations]


Reads like a fairly Light bike with Touring/MTB is what you want, thats spooners suggestion.

for Cross racing bikes are not geared so low, because in a low gear the field will leave you behind, next thing they will be passing you and you are a lap down..
Perhaps, it's better to shoulder the bike and run up the hill, and keep your momentum up.
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Old 07-29-10, 02:15 PM
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So being a newbie would I really be hurting without the lower gearing similar to a road bike?
I do plan on pedaling up some mountain roads, and I have to admit I have weak, bird legs for now.

As an example the bike below is on sale for $959, but it has typical cyclocross gearing. Would I be hating life trying to pedal that up a long stretch of road?

Key Features:
* Double butted aluminum frame with disc tabs, S-bend seatstays for great mud clearance, and a replaceable derailleur hanger.
* Responsive R6 aluminum fork with disc tabs.
* Shimano 105 rear derailleur with Tiagra STI shifters matched up with a FSA 46 x 36t crankset, and a 9 speed 12x25 cassette.
* Ritchey Comp wheel set with Maxxis Raze tires give you a great ride over any terrain.
* Available in 7 sizes (44cm-60cm) center to top.
Specifications:
Frame 6061 Double Butted Alloy
Fork R6 Alloy W & Alloy Steerer
Headset Steel Threadless
FD Shimano Tiara
RD Shimano 105 Short Cage
Shifter Shimano Tiara
Crank FSA Compact Cross 36 x 46T
BB Set FSA Square Taper 68 x 110mm
Cogs Shimano HG 50 12-25 9 speed
Wheels Ritchey Comp Road
Tire Maxis Raze 700 x 35 WB
Bar Ritchey Biomax Pro II
Stem Ritchey Road Comp
Saddle San Marco Ponza
Brake Tektro Oryx 992 canti
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Old 07-29-10, 02:35 PM
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If it comes with a 110 crank and medium sort of rd a 27t rear cog and a 34t chainring is in the range .
34/46 is 12t jump , most FD will work .
get your cross country running training in shape , and dismoutn practice, so the transition to jumping off and throwing the bike on your shoulder
is fluid, as is the leaping back on the saddle at the crest of the hill and going down the other side .
it's more than the bike..
if its just to commute on, a triple crank will be fine, that will give you a lower front gear
shimano as a group sorted out it's components as a set, best not go too far outside of the stock kit..

Last edited by fietsbob; 07-29-10 at 02:39 PM.
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Old 07-29-10, 02:53 PM
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the main question is, does it fit you?
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Old 07-29-10, 03:04 PM
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Well I could actually stop by the store after work to see if it fits, unless more overtime comes my way, but if it fits and I can't pedal up a hill then it doesn't do me much good.

I'm not fully understanding the whole gearing concept.
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Old 07-29-10, 05:31 PM
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Originally Posted by MacAttack
Well I could actually stop by the store after work to see if it fits, unless more overtime comes my way, but if it fits and I can't pedal up a hill then it doesn't do me much good.

I'm not fully understanding the whole gearing concept.
Normally I'd recommend Sheldon Brown's website or wikipedia. But between my explanation and Spooner's excellent post I think everything has been covered. Basically: the smaller the smallest chainring at the front and the larger the largest gear at the back, the more hill climbing power a bike has.

The bike you asked about was a 36:25 . A dual ring crosser can get to 34:28. A triple ring crosser with road chainrings can get to 30:28. And a crosser or tourer with MTB hardware (or a 29er MTB) 22:34. These have relative hill climbing power of 0.7, 0.82, 0.93, 1.53.

As for which one of these is enough for you - well, we're not your doctor and we don't exactly what hills you'll be climbing. In your shoes I'd go for the most mojo I could. But then in your shoes I'd protect my knee by using a short travel suspension system on the badly rutted roads you talked about.
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