Bacciagalupe

Heya. Just wondering what's involved in swapping back and forth between wheelsets. I know racers do it fairly frequently. Front wheel, obviously check the brakes. But what about the rear? Does each rear wheel get its own cassette? If the cassettes are different sizes (e.g. 9 speed 12-25 and 9 speed 12-27), do you need to fully re-adjust the RD? And can it be done well without a repair stand?

Quijibo187

Depends on your budget and how much time you have when you're swapping wheels.
I had 2 sets of wheels for my MTB, I had the second set built up with the same rim as what I already had so there was no need to adjust the brakes.
If you are putting a new casette on your second set, its generally a good idea to put a fresh one on your current wheels and replace the chain, it'll help with shifting and will run quieter.

It is handy to have 2 sets, I used one for commuting and one for trail riding.

well biked

In regard to the 9 speed example you give, it's possible to swap two wheelsets without having to make any adjustments. Size the chain for the 27t cog in your example. The potential problem is in the hubs and rims. If you're using identical rims/hubs, it will be no problem at all. If the rims are different width, you might need to adjust the brakes accordingly. If the hubs are different (all 8/9/10 speed hubs are not EXACTLY the same, for example), it's possible you might need to adjust the limit screws on the rear derailleur. I've swapped identical nine speed mtb wheelsets/cassettes for years, no adjustments necessary.

In regard to the cassette, if you're wanting to do this for quick, easy wheel changes, a cassette for each wheel is the way to go. Otherwise, it kind of defeats the purpose. Also, both wheels need to be dished properly (i.e., the rim needs to be centered), or you'll end up having to adjust the brakes even if the wheels are otherwise identical-

cyccommute 

You shouldn't have to adjust anything with the derailer on swapping wheels. I've found the brakes to be more problematic.

Bacciagalupe

H'm.... Well, I have a Surly Cross Check on order, and am toying with the idea of using the stock wide rims for touring & any offroad I happen to do, and putting on narrower and racier wheels for club rides.

Might be more trouble than it's worth, just curious as to how difficult it is. I'm guessing that with racers they get identically sized rims / hubs, with the express purpose of using the cheapies for training, the good ones for the race.

By the way, what's the incentive with MTB?

well biked

Do you mean what's the reason for using different wheelsets on mountain bikes?

If so, for me it's a couple of things. One, I can put a set of road slicks on one set of wheels, knobbies on the another, and be ready for two completely different types of riding without the trouble of installing/re-installing tires. Actually, though, when I first started doing it, it was so that I could have two types of off road tires already mounted, maybe one for loose or wet conditions and one for hardpacked trails. So basically, just different surface conditions, different tire types, etc., without having to change the tires-

aaronspoker

Besides the brakes, you may in fact need to mess with the derailler, but probably not the limit screws, since the limits should be in about the same place, since they're the same sort of shifter. The limit screws are primarily a safety measure to keep you from shifting too far when weird things happen.

Unless you get a perfect match, its possible that the shifter cable tension will need to be tweaked. If you have an adjusting barrel for this, and you should (Get one if you don't!), this is a three-second adjustment if you know how much you need to adjust it, and maybe 30-60 seconds if don't know. In any case, this is probably an easier adjustment than the brakes.

But even the brakes will probably be easy, as you can probably just tweak your front barrel adjuster until the brakes are tight, assuming both of your wheels are correctly dished and nothing funny is going on.

Make sure your derailler, chain length, etc are compatible with both wheelsets you intend to use.

operator

True. But why play russian roulette? Do the full RD adjustment, or at the very least CHECK the high/low limit screws carefully to make sure you won't shift into the spokes.

Especially if you aren't running a dork disk.

Super bad advice. It's the position of the cassette on the rear wheel that is going to **** with the limit screw adjustment. The shifter has jack all to do with it.

Why be lazy?

Check the limit screws

Sometimes you don't need to change anything, sometimes you will.

Check the limit screws

well biked

I was trying to illustrate to the OP that as long as you're dealing with identical wheelsets, you can switch wheelsets without hassle. But you're right, it would be wise to double check the limit screw adjustments the first time you make the switch anyway, and if you're running a slightly different large cog size, it would be a good idea to check the B-screw adjustment, too, to make sure it's not too far off with the smaller cog. But it would only be necessary to check this stuff one time, once that's done it's a trouble free switch. Kind of a moot point for the OP, though, considering he's said he wants to use two very different wheelsets-

aaronspoker

Can you explain why you feel this way?

The limit stops usually don't actually do anything. They only prevent overshooting, and help prevent catastrophic failure when something goes wrong, like a broken or caught shifter cable. They are not a sensitive adjustment at all. Quantitatively, in most shifters, you have several full turns on the low stop between the optimal adjustment and the danger area where the chain might leave the cassette.

Anyway, if the two wheels are even vaguely similar, it should be very easy to find a limit stop adjustment that works for both. Setting that up should be a one-time affair, as well biked mentions.

The point I was trying to make is that the only adjustment you'll need to make each switch is the tension/index adjustment--and that unless the wheels are completely identical, you'll probably need to give the index adjustment barrel a quick turn to get optimal shifting, making the switch and adjustment operation a 10-second affair.

DannoXYZ 

Yeah, the limit-screws odn't affect the shifting in any way, other than to prevent overshoots off each end. If you have the same model hubs, you probably don't have to adjust the cable-tension after swapping wheels. With different model hubs, you sometimes have to juggle axle-spacers to move the cogs in and out so that all the wheels have cogs in the same place, making wheel-swaps simple.

operator

You miss the point.

The limit screws is the ONLY adjustment that REALLY matters, a cable tension problem with the former properly set will only result in crappy shifting.

Out of adjusment limit screws can cost you your frame, derailleur and rear wheel. Yes, in an ideal world with identical everything you wouldn't even need to check or adjust anything.

But it's not. Limit screws can lose their adjustment, cable tension can lose their adjustment. Blindly putting in another wheel and crossing your fingers is stupid when it takes an extra 5 seconds to make sure the low/high limit screw is still properly adjusted. This check is even more important on low quality shifters with slop between the indexing.

I'm not even sure why this even needs to be debated.And yes, I agree once you've done the switch between two different wheelsets you know what adjustments need to be made if any.

operator

Of course they do, the also prevent your bike from exploding. Which is why I said "ignoring the limit screws on a wheel swap" advice is the worst you could possibly give.

Limit screws don't affect shifting? How about blindy screwing the H and L screw all the way in. Still shifts into all your gears? Didn't think so. Thanks for playing.

fourpunk

operator gets +1

as the primary mechanic for a cx team i have done just a "few" wheel swaps. each one gets a full RD adj--everytime.

well biked

But for the person who simply has two identical wheelsets (same rims, hubs, cassette), has the RD adjustments set up correctly initially, and just wants the convenience of not having to install/re-install tires all the time, checking RD adjustments isn't necessary. For the person in this situation, there are plenty of things to worry about in life, but this is not one of them.

aaronspoker

Yes, the possible consequences of failure are high. But I'm not sure why you think changing between two different wheels changes anything. Do you think this is somehow different from removing and replacing the same wheel (something that is fairly frequent for many people), or do you check the limit adjust screws in that circumstance too? Do you check the limit screws before every ride also, since they're probably much more likely to "lose their adjustment" by ordinary riding than by a wheel switch.

So, I don't think your concern is logical, as I don't see a mechanism by which switching a wheel is more likely to disturb the limit adjustment more than other typical activities. If the failure mode bothers you so much that you feel the need to frequently check the limit adjustment, it might be more reasonable to advise people to use spoke guards, which can contribute single-digit gram weights, and add no significant air drag.

The other half of this is I disagree that there is any meaningful limit stop adjustment you can do within ten seconds. For one, you need to place the bike on a stand (or invert the bike) to be able to shift the complete cassette. But I still don't see what sort of quick check you propose. Are you intending to shift into high and low, and check screw clearance/contact? This isn't necessarily that easy, particularly on most modern deraillers where this interface tends to be obscured. I think most people adjust these things by tightening them until they're too far, then backing them off. Do you propose doing that every time?

Anyway, for occasional wheel swaps, I agree with a check. But the OP asked about the specific case of two specific wheelsets that are swapped "fairly frequently" "without a repair stand." I don't see any rational reason to support what you suggest, although I do agree with your general sentiment to err on the side of caution. So I think the right answer is that almost no adjustment should be necessary after initial tuning, except possibly pre-measured tweaks to the indexing barrel.

By the way, cable tension etc does not affect the limit stop adjustment, which is why--in theory--it should never need to be adjusted after the initial set.