Chain rubbing rear tire on Clem.

[Jim Whorton]

Hi--

I have noticed on my Clem that the chain rubs the rear tire slightly when the bike is in lowest gear (small ring in front, big cog in back).  It's a 59cm Clem H, which I bought complete, so the bottom bracket, etc are as installed by Riv.  The tire is a 2" Kenda Kwick Nine and the cassette is a 9 speed.

Anybody seen this before, or have advice on it?  I don't see any weird wear on the side of the tire--and of course I don't use that gear much, only briefly on a steep incline--so maybe Riv set it up this way deliberately, rather than going with a wider BB to avoid the rub in that gear.

So maybe it's not a big deal.  On the other hand, I'd rather not have the chain rubbing the tire....

Jim

[Jeremy Till]

The long chainstays on the Clem mean that the chain is closer to the tire in lowest gear than it would be on an equivalent bike with shorter chainstays. My wife briefly owned one of the first gen 52cm Clem demo bikes that had 2.3" Schwalbe Super Moto tires and it had this issue. The chain occasionally got sucked between the tire and chainstay. Accordingly, when I built up my 59cm Clem with 2.2" tires I used a wider BB than was intended for my crankset to avoid the issue (I think the crankset was intended for a 113mm BB, and I'm using a 118mm). I'm not particularly sensitive to Q factor so the wider stance of the pedals doesn't bother me. I'm also not using a front derailleur, I shift manually between the two front chainrings, so I can't speak to how this might affect front derailleur operation. YMMV. 

-Jeremy Till

Sacramento, CA 

[aeroperf]

My Velocity hubs have a little 2mm spacer that goes on the freehub before the cassette is slid on.  It is required for “8, 9 and 10 speed cassettes.”
If your hub also requires a spacer and somebody changed the cassette and left off the spacer, that wouldn’t help your problem.

[Eric Norris]

Jim:

I wouldn’t worry about this. The chain isn’t going to wear down the tire, but the tire might deposit a little dirt on the chain.

I have one or two bikes which have a very minor rubbing issue in one ring/cog combo that I use probably less than 1% of the time. I just live with it.

--Eric N

On Feb 24, 2020, at 6:40 AM, Jim Whorton <jameswh...@gmail.com> wrote:



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[Jim Whorton]

Thanks, all.  I'll leave it alone for now...never noticed it while riding, only while looking at it on the stand.

Jim

On Monday, February 24, 2020 at 11:59:07 AM UTC-5, Eric Norris wrote:

Jim:

I wouldn’t worry about this. The chain isn’t going to wear down the tire, but the tire might deposit a little dirt on the chain.

I have one or two bikes which have a very minor rubbing issue in one ring/cog combo that I use probably less than 1% of the time. I just live with it.

--Eric N

On Feb 24, 2020, at 6:40 AM, Jim Whorton <jameswh...@gmail.com> wrote:



Hi--

I have noticed on my Clem that the chain rubs the rear tire slightly when the bike is in lowest gear (small ring in front, big cog in back).  It's a 59cm Clem H, which I bought complete, so the bottom bracket, etc are as installed by Riv.  The tire is a 2" Kenda Kwick Nine and the cassette is a 9 speed.

Anybody seen this before, or have advice on it?  I don't see any weird wear on the side of the tire--and of course I don't use that gear much, only briefly on a steep incline--so maybe Riv set it up this way deliberately, rather than going with a wider BB to avoid the rub in that gear.

So maybe it's not a big deal.  On the other hand, I'd rather not have the chain rubbing the tire....

Jim

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[jeffrey kane]

I guess it depends on how you use your bike and how chill a human you are. Me, I tend to be less chill about things like that. It shouldn't happen on a bike that's supposedly spec'd for tires that big (or quite frankly, any properly designed bike). If it's just a matter of spacers not being installed on the cassette then that's an easy fix. I wouldn't be opposed to 1mm to 1.5mm spacers on a BB shell either .. or flat out changing the BB spindle length. But otherwise no. I could not stand for chain rub on a tire ...  even in a lightly used gear.

[Joe Bernard]

The conflict is the bike was originally spec'd with Sugino cranks, then Riv switched to the very low Q Silver. The ones I've ridden were so "off" to me that I kept missing the pedals because I expected them to be wider apart. If I owned one now I would swap the stock BB (I think it's 110) for a longer one.

[Jim Whorton]

That's interesting, Joe--I did not know they had changed the crank on the Clem.  Awhile back I bought a Clipper crank from Riv, the one based on the Sugino XD2, for use on an old mountain bike and I like the looks of that crank a lot.

Jeffrey, I hear what you are saying about the level of chillness.  This is a recurring issue for me . . . riding bikes is about freedom, and setting up bikes is this fascinating puzzle that can become obsessive, which is kind of an opposite thing from freedom.  I like both sides of it, though.

[Jeremy Till]

I'm not sure it's totally down to the crankset, as the demo bike my wife owned had Sugino XD2 cranks, but still had the tire clearance issues: 

https://flic.kr/p/V8eVgF

It's worth mentioning that Riv's commitment to square taper cranks does allow a relatively simple solution to the problem, i.e swapping in a wider BB spindle. If the Clem were spec'ed with "modern" two-piece cranks we'd be SOL, since they don't allow for spindles to be swapped.  

-Jeremy Till

Sacramento, CA

[Eric Daume]

Seems like a poor BB spec on Riv’s part, since the Clem can fit up to a 2.5” or so tire. 

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[Mark Roland]

Huh. My Original Clementine complete came with Silver cranks. I thought the Clem was designed along with several components, including the Bosco bar and the Silver cranks? I may have that wrong. I guess you are saying in the early design stage it was built around using the Sugino crank? Still, with several iterations of Clem Smith Jr., you would think, if they saw it as an issue, they would have addressed it with a slightly longer bb spindle. I wonder if it's even more pronounced on the latest, longer chainstay models. I do seem to recall my Big Dummy may have experienced this on occasion. Certainly seems to be several easy fixes if it's a bother.

On Tuesday, February 25, 2020 at 12:37:45 PM UTC-5, Joe Bernard wrote:

[Joe Bernard]

Mark, my memory of this may be incorrect based on I bought a first-gen frame and used Sugino cranks. At any rate someone else said the problem happens with Suginos, too (I never noticed it) so basically I don't know what I'm talking about. It's been that kind of week for me!

[aeroperf]

Not to beat this to death, but two quick observations—

Jeremy - Two piece cranks, unlike most square taper, can be moved 2.5mm in either direction on a typical 68mm BB shell on a Riv., just by moving spacers.  The width between pedals (Q factor) doesn't change, but the bias does. 

And - Just because a tire can fit between forks or seat-stays brakes doesn’t mean that it “fits”.  There is this thing called the Chainline.  Riv specifies a chainline - 47.5mm for my Sam - which defines where the middle of the front chainrings and the middle of the rear cassette should be.  A little geometry can tell you what the maximum tire width for a properly set-up drive would be with no rubbing.
Quick example:  9-speed cassette gear spacing is 4.34mm.  Chainline is centered on gear 5.  So the gear closest to the center of my Sam is at 47.5 - 4.34x4, or 30.1mm from the centerline of the bike.  Subtract another 2.2mm for 1/2 the chain width and you’re at 27.9 from the bike centerline in the rear.
Doing this for the front chainrings (and it depends on if it’s a double or triple) and drawing a line between and locating the tire on that line tells you how wide a tire you should be able to fit without rubbing.
You CAN move your chainline out, but not far, as the rear cassette is pretty well fixed.  Also I highly recommend you actually measure your bike - my rear cassette was 2mm off and so 2" tires might have rubbed on my bike.
More help is here: https://www.sheldonbrown.com/chainline.html

As a Mechanical Engineer who enjoys math, Jim has nothing on me for setting up bikes becoming obsessive… :-)

Anyway…Rivendell may have set the bike up with smaller tires.  If it bothers you, measure your bike and dig into it.  If not, just ride.

[Joe Bernard]

One note Jim mentioned which may render the whole convo moot: he only noticed it in the stand. The chain is probably stretching taut enough under pedal pressure that it's not even rubbing in real world use. I've owned several of these with those cranks and tires and never noticed it on the road.