Derailleur pulleys - Does size matter?
 

I was here a couple of weeks ago concerning derailleur adjustments (http://www.bikeforums.net/bicycle-me...djustment.html) and was interested in hearing from folks in the know about der pulleys and if size matters.

My original der had the 10/11T pulleys. A few years ago, when I replaced the der, it came with the larger pulleys (in dia. and no. of teeth, tho don't have the no. of teeth at hand, but the setup has the pulleys fairly close to each other). Does anyone have any insight as to whether this is better or worse than the smaller pulleys. Here's my take on it:

Pros -
* Larger diam. means more chain on pulley which could mean smoother, more positive shifting? (not clear to me since I don't really have any way to do A/B comparison)
* Fewer rotations per stroke which could mean less wear-and-tear on the pulley
* Since the pulleys are closer together, there's less chance of the chain coming off between pulleys (never experienced this and have never heard of it happening)

Con -
* With more of the chain on the pulley, less flexibility during the shift which could mean a stiffer/worse shift (see Pros above)

Anyway, interested in anyone else's experience or knowledge...Thx in advance....

Shimano on some of the lower range do just that, bigger pulleys, but the upper range they're 11t

My old Campag and the chain tensioners on my Brompton and Rohloff use 10t.



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Tooth profiles and the bushingless chain designs are in service of shifting quicker.

When you said lower range....did you mean lower-end/less expensive?

When I bought the bike, the Shimano parts were of "Alivio" class, at least, ders, freehub and cassette were. The orig der had the 10T pulleys on it. When I replaced the der I went with the same Alivio brand. Maybe at, or by, the time I replaced the der (quite a few years after I bought the bike) Shimano went to the bigger pulleys.

So, any direct experience with small pulleys vs big pulleys worth noting?

Cheers.....

The larger pulleys will wrap a little more chain. Probably not a big difference for a road bike, but perhaps on a MTB or small wheel bike..

Oh, that reminds me, my cargo bike just ate the derailleur. 20x4.5 on the rear, and I've been having troubles with derailleur sizes. So, I need to get something wrapping a bit more chain installed. I have some ideas in mind.

Realized I forgot to mention that this is about a MTB - Specialized Hard Rock.

Can't say I've ever noticed much of any difference. Was curious if anyone else had a chance to compare.

Cargo bike...is that a specific kind of bike...or just the bike you use for hauling "cargo"?

Noticed you're in Eugene. Lived in Hillsboro for ~6 yrs. (Now back in SF Bay Area). Miss the beauty that is OR

My cargo bike is a homebuilt Frankenbike designed and built specifically for hauling cargo. See my Avatar. 'The idea was that a smaller rear wheel would lower the center of gravity, and improve overall stability. Anyway, one might call it a class of bikes with many different makes and models.

I tend to use trailers with regular road bikes most of the time, and only drag out the cargo bike out when I need to carry something on the larger trailer, so really it doesn't get a lot of use carrying stuff. However, I've had over 100 pounds on the rack, and about 500 pounds on the trailer.

Mine was built around a 20x4.5 rear wheel. Kind of a fun idea, but in the end not so really practical. However, the rear derailleur tends to overhang the rim a bit when shifted to the lowest gears which causes problems with the small, wide rear wheel.

Suntour also made a triple pulley derailleur that pops up for sale from time to time. The idea is to wrap a little extra chain with a shorter derailleur cage. When stretched forward, chain wraps the rear two pulleys. When relaxed, the chain wraps all 3.

I swapped my pulleys from 11t to 13t. Not sure if i noticed an increased performance due to the size but definitely due to the newer bearings. The old ones were draggy to begin with.

Yep. At 1 point I also replaced the 10T jockey/guide pulley (top one) on the now-replaced der with the same 10T pulley cuz it seemed fairly sloppy. That cleaned up the shifting quite nice. Never thought of going to a larger pulley at the time...either wasn't aware that was an option or wasn't sure it would fit (short length der on the MTB).

Appreciate the feedback.

NB; The top guide pulley on Shimano indexed shifting schemes are sloppy, laterally intentionally, by design.


Cage design is different on RD that use the larger pulleys..


But feel free to experiment..





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There's sloppy...and then there was *sloppy*. I had done a poor job of maintenance up to the point where I replaced the pulleys :( so the top pulley bushing was fairly well worn (creating more than lateral play). And I didn't understand the Shimano design (lateral play) until I put in the new pulley. Of course, poor maintenance eventually caused the whole RD to become unusable anyway.

Hadn't thought of replacing the larger pulleys in my current RD with smaller ones to see what affect that might have. Interesting. Maybe even trying a mix...tho, that might be pushing the experimenting a bit too far (have to check if I still have the old RD....pulleys were still in fairly good shape when I replaced it). Appreciate the suggestion.

Cage design different...how so?

Rivendell sells the Shimano Altus which has a 13-tooth jockey pulley and a 15-tooth tension pulley. The stated advantages are:
* Greater chain wrap allowing for a shorter cage hence more clearance - important for small-wheeled bikes and maybe some mountain and cyclocross bikes;
* The larger diameters provide a longer lever arm around the pulley Axel's reducing the effort to spin them.
YMMV
Cheers!

Appreciate the link. I have the RD-M410 (Alivio version?) so the pulleys are prob'ly the same. I 'spose I could count the teeth and know for sure.....but then, that would be too easy ;)

Hadn't thought about the shorter cage benefit, but that makes sense. I'm on 26" tires, so no help for me. "longer lever arm"...sounds like my "not as many rotations per stroke, thus less wear-and-tear" comment. YMMV "fer sure" :)

Wondering if that's a trend overall, or maybe just for a specific class of bike, or just a passing fad (for whatever biz bennies Shimano gets from it).

Cheers.....