Login required to started new threads

Login required to post replies

"Crossing" chain on the chainring/cassette?
Quote | Reply
Stupid question alert. Forgive me, I'm guilty of not being a bike gearing aficionado.

On the flats around here, my most comfortable cadence at crusing speed typically comes when I put my chain on the large chainring, but then stay in the lower gears in the rear cassette. (Not sure what my gearing is exactly, but it is stock Shamano 105 on a Cervelo One). This results in my chain "crossing" on an angle from front ring to rear cassette.

I was once warned about this by someone who said it would supposedly cause unnecessary wear. That sounded bad, so I have since gotten in the habit of riding in the small chainring more than I would like to "protect my drivetrain". I hate this. It isn't as comfortable as the large chainring.

So, how big of an issue is the "crossover wear" issue? Did I get bad advice?
Last edited by: Iron Buckeye: Jul 3, 06 7:53
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
I wonder the same thing. Thankfully someone asked before I made a fool of myself :)
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
No, you got good advice. You should generally stay out of "cross-over" gearing as much as possible. In addition to the wear on your drivetrain, you are also losing some power due to increased friction. If you do the math on your gearing, you will find that the "20-speed" bike you have doesn't really even have 20 different speeds anyway--2 or 3 gearing combinations are usually identical even though you are in the big ring vice the little ring. So, shift down to the little ring and up 2-3 gears on the cassette and you are in essentially the same gear with less wear and friction. The "comfort" issue is all in your head as long as your RPM is +/- 5 or so at the same speed.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
figuring out how many gear inches your different gears are is pretty easy. the hardest part is just counting how many teeth you have, both in front and in back. some of the cranksests have it written right on them. the cassettes often have the high and low written on them.
then, just go to sheldon brown's gear calculor and plug in your info. you can figure out what the actual difficulty of the gears are. And if it's worth it to change your cassette to get more of the ratios you want.

i've wondered, though, when it's actually "cross-chaining" on a 9 or 10 speed cassette. on a 7-speed, it was much more dramatic. but how many on a 10 speed are usable? 12 of the 20? 14?
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [aliengin] [ In reply to ]
Quote | Reply
yea, it's really not good to do that, especially since there is overlap.

go here and put in your gearing (set it to gear inches). If you don't know it, count teeth. My guess is the rear will be a 12-25 (if it's 10 speed). Just count the big and small cogs and use that to see what "standard" cassette you have.

Then just look at ratios. Look at the ratio for your comfortable combo and see where it is on the small ring. If it really bugs you that much, then play with other cassettes and see which one will give you the ratio you want on the small ring then swap out cassettes.



sometimes you just have to eat the cake
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
http://www.sheldonbrown.com/gears/

set the gear units to "gear inches", don't worry about crank lenght. enter the other info (presumably 700x23 for the wheels), figure out hte cassette and the cranks (by counting, if you have to). you can even get a little version of the ratios that you can stick to your top tube.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
Although I think the "perils" of a cross chain are overplayed, it's unnecessary in triathlon.

In road racing, it may make sense to start an attack on a climb or over the crest of a roller in the 53-25, 23 or 21. And it may make sense to stay in the large chainring as you downshift on short climbs and rollers.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [tri_bri2] [ In reply to ]
Quote | Reply
Fair enough. Can someone walk me through the "math" so I can figure out which gearing combinations are redundant and how far down my cassette I have to go before it isn't in my head?

Also, anyone know what the standard 105 gearing is on a Cervelo One (2002). The bike appears to be gone from their website.


(EDIT: Never mind, about 65 of you answered my question in the time it took me to type it. Thanks)
Last edited by: Iron Buckeye: Jul 3, 06 8:18
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
on your bike,

count the no. of teeth on each of the 2 big chainrings.

then count the no. of teeth on each of the cassette cogs.

post all that info here, someone will help you out and give you exact gear inches, etc.





Where would you want to swim ?
Quote Reply
Post deleted by Administrator [ In reply to ]
Re: "Crossing" chain on the chainring/cassette? [AlanShearer] [ In reply to ]
Quote | Reply
I agree--I would never say "never" use a cross-over gear because for short periods of effort, it makes sense to avoid shifting the front derailluer.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [tri_bri2] [ In reply to ]
Quote | Reply
No worries. I don't obsessively avoid crossing the chain (For example, I do allow it to cross on rolling hills to avoid shifting my front derailluer as noted by others). It's just the long, straight, flats where I start to think about it.

Glad to hear I haven't been doing anything too stupid.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Iron Buckeye] [ In reply to ]
Quote | Reply
There is possibly an argument for keeping your chain on the biggest ring anyway as it stretches the chain less so it will last longer.

http://mclean.errl.org.uk
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [Turg] [ In reply to ]
Quote | Reply
Chains don't "stretch." The reason chains get longer is wear, not stretching. As the chain ages, the pins and rollers lose metal due to the friction, allowing more "slop" between the links. The best way to avoid chain "stretch" is to keep your chain clean and lubed.
Quote Reply
Re: "Crossing" chain on the chainring/cassette? [tri_bri2] [ In reply to ]
Quote | Reply
In Reply To:
Chains don't "stretch." The reason chains get longer is wear, not stretching. As the chain ages, the pins and rollers lose metal due to the friction, allowing more "slop" between the links. The best way to avoid chain "stretch" is to keep your chain clean and lubed.


That makes sense when you put it that way. I meant chain "stretch" not chain stretch!

I still think my argument holds: The friction causing the "slop" will be proportional to the tension in the chain, tension which can be reduced by using a larger gear. Also the links will rotate a shorter angle as they are linked to cogs with larger radii.

I can't prove any of this mind you, its just me trying to explain my hypothesis.

http://mclean.errl.org.uk
Quote Reply