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Opinions on Rims, Tires, and Climbing stresses

Old 09-28-10, 09:25 AM
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Opinions on Rims, Tires, and Climbing stresses

Here's the rub.

I just returned from a 478 mile, week long, fully loaded, selfcontained tour around Middle Tennessee. I thought my wheels where tough as nails, but I cracked up a rear rim in 4 or 5 places about 200 miles into this tour.
Salsa Degalo cross rim, DT 2.0/1.8 spokes and LX hub. (sorry) 36 hole rim.
I started using this setup with 32 tires, but have switched to 28s for the last two tours. I also commute on this bike, very lightly loaded, through out the year on this wheel set. I'm a big fella 245lb and cary plenty.

Questions?

1. Do you beleave climbing puts more stress on rear wheels than flat rides?

2. Does running a narrower tire put more stress on wheels on a loaded bike?

3. Is there any way to realy know if a wheel will fail days into a tour, if it already has many miles on it?


I had a great time, and would encourage any of you to visit the back roads of your home state. You will find all kinds of things you may have never known about! I would like to think the bike shop in Cookville TN for getting me back on the road in the same day, and the kindness of total strangers along the way!

Last edited by uciflylow; 09-28-10 at 03:06 PM. Reason: confusion
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Old 09-28-10, 09:46 AM
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Originally Posted by uciflylow
Questions?

1. Do you beleave climbing puts more stress on rear wheels than flat rides?
Obviously, the steeper the hill the greater the proportion of the load that will be borne by the rear wheel as you're climbing. But I wouldn't normally expect that on its own to lead to failure.

2. Does running a narrower tire put more stress on wheels on a loaded bike?
Not as such, but obviously a fatter tyre is going to do a better job of soaking up the bumps, loaded or unloaded.

3. Is there any way to realy know if a wheel will fail days into a tour, if it already has many miles on it?
Not that I know of. Making sure you can't see any damage, checking that the wheel is true and the spokes properly tensioned is a sensible precaution but it won't guarantee against failure.

FWIW, if you're 245lbs and carrying "plenty" in the way of baggage, I suggest you're asking quite a lot of a 28 spoke wheel. I use Mavic rims with 36 spokes on my own tourer, and I tour at a total weight (me + bike + baggage) of about 280lbs when fully loaded. I use 32 spokes per wheel even on my carbon road bike, where the total weight is about 215lbs.

Last edited by chasm54; 09-28-10 at 09:49 AM.
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Old 09-28-10, 10:22 AM
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36H Velocity rims on our tandem, which weighs 390 lbs. full loaded. Haven't had a problem. OTOH, I build my own wheels, so I know they are tensioned evenly. Buy a Park TM-1 and check your wheels. IMO every tourer should own one of these. We put a lot more stress on our wheels and then go off into the boonies on them.

Salsa doesn't list a 28H version of their Delgado.

Check the rim carefully for cracks at the spoke holes. Probably your spokes were under-tensioned. With the right rim, 28H could be OK. No way to know now what the problem really was.
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Old 09-28-10, 10:46 AM
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i've been running almost the same wheel setup for the past year. 32H salsa delgado cross (700c) rims to a deore LX hub with unknown (i didn't build it) straight gauge spokes. i've commuted, toured and raced cyclocross on this wheelset for the past 13 months with no problems. i weigh 215lbs and commute with maybe 20 lbs of gear. probably have put 2000-3000 miles on them in the last year. also, my commute is fairly hilly.

how many miles does the wheel have (did it have) on it? i usually end up replacing mine every 4k miles due to rim wear from braking.

i put on about 40lbs over the past year and to be honest i've had way more trouble with those LX hubs than the rim.
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Old 09-28-10, 10:54 AM
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Originally Posted by Carbonfiberboy
Buy a Park TM-1 and check your wheels. IMO every tourer should own one of these. We put a lot more stress on our wheels and then go off into the boonies on them.
A tensiometer is very helpful when you build wheels, but another way to make sure the spoke tensions are even is to pluck the spokes (a tire lever works well as a pick) and listen for the tone that is produced. If you get about the same tone in every spoke (or every spoke on one side, in the case of rear wheels) then your tensions are about the same. A spoke that produces a lower tone is under less tension, and a spoke producing a higher tone needs is under more tension.

I have used both methods when building wheels, and the tensiometer is much easier to use and somewhat more reliable, but if you are trying to check spoke tensions while on tour, the plucking method works reasonably well, provided you can get away from traffic noise.
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Old 09-28-10, 10:57 AM
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I think someone your size (my size too) should use a much stronger rear rim and tire. 36 spoke is a minimum and a fatter tire will absorb more of the shock that can stress a rim. I use a Mavic A719 rim with 37mm tires, well over 10k miles, no problems.
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Old 09-28-10, 11:10 AM
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Originally Posted by uciflylow
1. Do you beleave climbing puts more stress on rear wheels than flat rides?

2. Does running a narrower tire put more stress on wheels on a loaded bike?
Rocking your bike with rear panniers puts a lot of stress on the rear wheel. If you rock the bike while climbing, then yes. Instead of sharing the load somewhat evenly among the spokes on either side of the wheel, the load is transfered mostly through the spokes on one side.

For the same load, you probably run narrower tires at higher pressure than wider tires. That higher pressure alone stresses your rims. Narrower tires also do not absorb and distribute shocks and bumps as well as wider tires. You get a rougher ride and every component between your butt and the ground experiences higher loads. You're more likely to crack rims, pop tires, break spokes and nipples, wear bearings, bend seat rails, crack frame welds, etc.

My advice:
If the road feels rough, take some air of the tires. If you keep getting pinch flats, get bigger tires.
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Old 09-28-10, 11:50 AM
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climbing is irrelevant, but riding down hills at speed would put increased load, though not enough to mater. 28 spoke wheels are a very bad choice. 36H is good enough in a proper set of wheels. I ride 40 at your weight, but they are a bit of a pain on parts availability.
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Old 09-28-10, 01:10 PM
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Originally Posted by gorshkov
A tensiometer is very helpful when you build wheels, but another way to make sure the spoke tensions are even is to pluck the spokes (a tire lever works well as a pick) and listen for the tone that is produced. If you get about the same tone in every spoke (or every spoke on one side, in the case of rear wheels) then your tensions are about the same. A spoke that produces a lower tone is under less tension, and a spoke producing a higher tone needs is under more tension.

I have used both methods when building wheels, and the tensiometer is much easier to use and somewhat more reliable, but if you are trying to check spoke tensions while on tour, the plucking method works reasonably well, provided you can get away from traffic noise.
Yes, all true as long as the person has a TM-1 at home and set the spoke tensions properly. Many wheels are under tensioned. Most? Because the builder used the pluck method and never did do a proper tension check. The reason for using butted spokes isn't really to save weight. It's so you can stretch them enough so that they never become under tensioned as the wheel revolves under load. Under tensioned spokes break and can also crack rims.

In theory, 28H should be fine if the rim is strong and the wheel properly built. Look at it this way: normal spoke tension is 105-110 kgf, no matter the number of spokes. So you have 220 lbs./spoke. As the wheel goes round, you've got maybe 6 spokes at the top and bottom that really do anything, so 12 spokes * 220 lbs. * 2 wheels. That's a lot of force supporting even 300 lbs. of rider and gear. The real big difference is in rim stiffness. The old 20 spoke Rolf front wheel on my road bike has only 70 kgf tension. Why so little? Because the rim is so stiff. So the stiffer the rim section, the fewer spokes you can get away with and the lower the spoke tension can be, because you don't have to stretch the spoke to account for rim movement.

So wheels are funny things. The new Rolf 16-spoke tandem wheels have very high spoke tensions because each wheel supports twice as much as on a single. Makes sense. And yet the ordinary 36H wheels on our tandem have the same spoke tension that we run on a single bike, loaded or not, because the rim section isn't as stiff. Though we run 28H on the singles.
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Old 09-28-10, 03:04 PM
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WOW! I read and reread before I post, and I still get a line in there that is not properly understood!

I modified the origonal to read 36 hole rim, 32 or 28 tires. Thanks for the replies, here's more information.

The wheel was built by a good builder and it had about 5000 miles on it when the failuer occured. I have cracked rims at the spoke holes in the past, Bontrager, and even my AC Hurricanes, and they always cracked away from the spoke twards the next spoke hole. These cracks formed from the radius of the rim in a large U shape around the spoke hole. It was like the rim metal was being pulled off the rim proper. I also never broke a spoke or had the wheels out of true untill the failing rim.

I have a new set ordered, Mavic A719, DT 2.0/1.8 spokes, and XT hubs. I intend to have the shop stress releave them and check the tenson before I pick them up.
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Old 09-28-10, 03:52 PM
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Originally Posted by uciflylow
Here's the rub.

I I'm a big fella 245lb and cary plenty.

:
How much is "plenty"? I could see that a wheel being pushed to it's limits could start failing in 5000miles. I don't understand why a big person carrying "plenty" would use 28mm tires.

Last edited by LeeG; 09-28-10 at 03:58 PM.
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Old 09-28-10, 04:22 PM
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My pretty trouble free touring wheels have been, a Mavic Mod 4,
and my current wheel set uses a Sun Rhyno [not the rhyno light, its definitely heavier]

Both are tandem like wheels I built .. front 40 spoke , rear 48.

after damaging the 1st rear with overshifting the chain into the spokes
i rebuilt it and added a spoke protector.
after that I had only 1 spoke to replace on the Mavic wheel, on the road in England,
finished a 6 month tour after replacing that 1 break.

Ive had none to deal with the Sun rim wheelset. 622-40 tires
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Old 09-28-10, 04:24 PM
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Wheels are funny things to the extent that I don't pay much attention to technical discusions that are way above my pay grade. With touring the usual issues come into play, they aren't particularly designing this stuff for us. So it becomes a risk management thing. There aren't that many really good rim choices out there, some would say none. And to the extent that they are "stronger" it may not relate to the way we use rims. So far, nobody has made an argument I have heard as to why more spokes is less strong. I tried to get one going on the idea there could reach a point of too many holes... Mostly people talk about how few spokes could one get away with. Ironically the best high spoke rims currently are also deep section rims that should skate by on less spokes. So is that the best of both worlds, lots of spokes and deep sections, or not?
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Old 09-28-10, 04:44 PM
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Merit of a high spoke count wheel is each spoke carries a smaller % of the load..

My broken spoke was only 1 of 48, and a trifle of wheel truing on the roadside ,
and I was good to go for days until the opportunity came to replace it ..

Phil Wood Freewheel Hub.. just needed to borrow a big adjustable spanner to remove the freewheel
to get at the broken spoke.. I carried a couple of each in the sizes for each of the 3 lengths.

Carrying the wheelbuilder under my hat really helps.
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Old 09-28-10, 04:44 PM
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Originally Posted by Peterpan1
So is that the best of both worlds, lots of spokes and deep sections, or not?
and is the thickness of the rim sections appropriate for the load? Lots of spokes on a light deep rim that has a thin flange that can bend under pinch flat isn't much good either.
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