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wheel strength?

saruti

Turbo Monkey
Oct 29, 2006
1,167
73
Israel
We often see here questions like:
What is the lightest rims you can use?
Lightest spokes?
And more...
I think we have to think about it differently
From where comes the strength of the wheel?
What is the most important element?
The rim?
The spokes?
In the past years we see lot of really light rims in the downhill scene. (ztr stan joe and more)
Lighter rims are surely weaker... (Are they?)
And if not, can we use AM light rims for DH?
Or maybe Chinese light carbon rims?

What do you think?
 

iRider

Turbo Monkey
Apr 5, 2008
5,648
3,089
Define 'strength'!
Strong as in denting proof? Strong as in stiff? Strong as in durable? For a 140# or a 200# rider?

In my experience a stiff rim will allow you to get away with superlight spokes and still end up with a rideable wheel. If you are going to town with light rim, light spokes, low spoke count etc. you end with something that wins you bragging rights on here but doesn't keep you happy on the trail.
BTW: hub weight has nothing to do with wheel strength (excluding bust freehubs of course).
 

baca262

Monkey
Aug 16, 2011
392
0
from my experience the strength comes from builders skill - the 4 wheels i built (i only ever built 5) kinda sucked but one turned out perfectly, i have it up front for 3 years already, re tightened only once.

all were quite different but 2, the one i built (fireeye excelerant + alpine III) and the one i got from the shop i still ride (sun ringle s-type + alpine III) - i had to constantly re tighten my handiwork till i cased it into a curb placing a 2" deep bump into the rim and breaking 4 spokes (which i found quite astounding for my 60 kilos) while i cased the latter similarly a few weeks ago and not even a dent in it.

also the wheel with xm321 i built was rather disappointing, all of these were on the rear.
 

saruti

Turbo Monkey
Oct 29, 2006
1,167
73
Israel
OK
You're right
Let's say we're talking about a rider, an average weight of 75 KG
My intention was on disaster tolerance.
I dont want my front wheel to crash on a big jump landing.
I want it to be stiff when I corner.
I dont really care about the rim getting some beatings, as long as they wont let the tire get out of it....
 

iRider

Turbo Monkey
Apr 5, 2008
5,648
3,089
OK
You're right
Let's say we're talking about a rider, an average weight of 75 KG
My intention was on disaster tolerance.
I dont want my front wheel to crash on a big jump landing.
I want it to be stiff when I corner.
I dont really care about the rim getting some beatings, as long as they wont let the tire get out of it....
Hub: pick your favorite, 32 hole
Spokes: CX Rays
Nipples: alu DT or Sapim
Rim: tough choice, but you should be able to get away with a Flow, Alex Supra 30 or DT EX500.
 

Tomasis

Monkey
Feb 26, 2003
681
0
Scotland
probably it depends on if you will build a wheel with limited skill.

I always choose competition 2.0 and brass nipples. It adds weight, but it is better be safe than sorry. If I give a wheel to tune to a pro, light spokes and al nipples might work.

Re light rims, it is very individual, maybe try lighter one and see how long time it takes to dent, destroy depending on track profile, frequency of riding and so on. Downhill racing affords to throw out every wheel set after each ride (change rims). Carbon products changed it and you can run those for a while in a pro team.
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Nipples: alu DT or Sapim
Alloy nipples are a waste of time for DH in my experience, they tend to fatigue crack over time - especially after a few truing cycles. Brass or bust.
 

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
Just for the record if anyone wants to try the new dts that come stock with demos don't do it. Just came back from a local race and a friendly team went trough them like they were made of rubber. They had gigantic dents even though the riders didn't feel any hits.

In my opinion get stans for the front and something a bit heavier or cheaper on the rear since it will get beat up. I run old 823s (the lighter ones) but If I didn't have a few of them I'd probably go with Dartmoor rider due to the price (replacing them costs next to nothing). That or new e13s if you can afford them.
 

saruti

Turbo Monkey
Oct 29, 2006
1,167
73
Israel
so. you say that with the right build any light rim can be used in DH?
and I mean, it will not catastrophic crack under me.... ?
can I use XC rims?
(I really dont care about dents only about it being strong in corners and big jumps)
 

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
so. you say that with the right build any light rim can be used in DH?
and I mean, it will not catastrophic crack under me.... ?
can I use XC rims?
(I really dont care about dents only about it being strong in corners and big jumps)
I wouldn't even if they were strong enough because of rim width but honestly stans is as light I'd go. Even with the best build if you make a mistake a rim may crack.
 

Tetreault

Monkey
Nov 23, 2005
877
0
SoMeWhErE NoWhErE
it really depends on who you are, who built it, ect... there is no way that someone on here can give you a definate answer as to what will work for you. I'm a lighter guy, 155-165lbs depending on the amount of crap i eat, and i can get away with riding 719/819's almost anywhere, no flat spots no taco'd wheels, just tightening them up every once in awhile. However, on the same trails, a friend of mine weighing probably 180lbs destroys 729's, atomlab pimps lites, and ex500. I do ride with my tires at a highter pressue then him, so perhaps the narrower rim width combined with higher pressure explains my lack of flat spotting, but complete level of destruction is something that cannot be so easily explained.

TL;DR Use your discretion as with anything else
 

saruti

Turbo Monkey
Oct 29, 2006
1,167
73
Israel
OK
another Question.
what will make a wheel catastrophic fail?....
a weak rim?
bad build?

Tetre, I'm light like you, but I think that in DH speeds, on very technical trails with roots and\or rocks, the same can happen to any rider....
 

baca262

Monkey
Aug 16, 2011
392
0
landing with your wheel off by 90 degrees. i have never really seen a wheel completely disintegrate, go take a look what cam zink did to a deemax by casing a huge dropoff backflip - he did blow it up but it didn't snap in 5 pieces.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,580
2,005
Seattle
Alloy nipples are a waste of time for DH in my experience, they tend to fatigue crack over time - especially after a few truing cycles. Brass or bust.
I half way agree. Two points here:

-For DH, if I'm using a light rim to build a race wheel, I don't expect the rim to last more than a season anyway, at which point using Al nipples is fine, because it's getting rebuilt quickly anyway. I'm easy enough on wheels that if I'm using something like 823s, I'll usually get quite a lot of use out of the rims, at which point it matters, and I'll use brass.
-For AM, where I'm less likely to kill rims, I've discovered using something like DT SuperComps, which are only 1.8mm at the threads, as opposed to 2.0mm actually makes Al nipples a lot more viable. The outer diameter of the nipples stay the same, so the wall thickness is a little bigger, and it seems to be just enough to help a lot.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Both completely legitimate points.
Personally though I'd rather build my wheels to be both light and strong, given that the mode of failure is usually excessive denting - which depending on chance could take one or two seasons. On the occasion I have a good run, I can keep truing and riding the wheel worry free. The alloy nipples seem to start cracking after about a hard season, and one breaking is usually a sign of many others being cracked.

Makes sense for the AM bike with the Super Comps though, very interesting point on the wall thickness.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,580
2,005
Seattle
Makes sense. The last handful of light wheels I've killed have been a mix of excessive denting and more catastrophic failure but given the strategy I described above I haven't broken any nipples in years. The current wheelset on my AM bike are Flows with SuperComps/ Al nipples and are on their 3rd trouble free season. For DH I'm running brass nipples and DT 2.0/1.8/2.0 spokes (I can never get it through my head if those are Champions or Competitions) with 823s on one set, and 721s on the other. The 721s are actually holding up brilliantly, quite pleased with those.
 

Tomasis

Monkey
Feb 26, 2003
681
0
Scotland
While we on subject nipples:

Regarding pro lock dt nipples, does it work for you? for example truing a few times under some seasons.


Re weight, I see 22gram brass vs aluminium difference for one wheel as minimal difference, for AM, I gladly add extra huge weight gain ie 22 grams :)
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I've always used the prolocks and they seem to work fine over a few truing cycles. If I reuse the same spokes and nipples on a new rim (which has worked fine for me with DT comp spokes and DT brass nipples) then I usually use a little blue loctite on the threads anyway as the prolock compound doesn't last forever.
 

DHDror

Monkey
Feb 7, 2005
181
-1
Israel
I just wonder what people think about flange width,
I always thought the more we triangulate the spokes by widening hub flanges, the stiffer and lighter our wheels can be.
Lately I noticed some 150mm hubs with the same flange spacing as 135 hubs and just wondered if this is over rated?
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I just wonder what people think about flange width,
I always thought the more we triangulate the spokes by widening hub flanges, the stiffer and lighter our wheels can be.
Lately I noticed some 150mm hubs with the same flange spacing as 135 hubs and just wondered if this is over rated?
Our wheels are already sufficiently strong and stiff - the problem with using the maximum width afforded by a 150mm hub is that you bring about the same problems that plague a typical 135 hub, which are uneven spoke lengths and angles, thus uneven spoke tension between the two sides.

So in my opinion, the hubs that best make use of the 150mm standard are those like Hugi and Hope, as they allow for a true zero-dish wheel (even spoke lengths, even spoke tension). The result is a build that is easier to work on, and more resilient to going out of true.
 

HardtailHack

used an iron once
Jan 20, 2009
6,626
5,442
How important is it to have a good wheel builder? My second wheel build was Arrow FRX rims laced to Hope Pro 2's with CX-Ray spokes. I didn't really know what I was doing but the wheels have stayed true and the only thing that has given trouble so far is the weak Hope axle.
Pretty sure the wheels ended up bang on 2kg and they seem plenty strong for me and I'm 220lb.
 

descente

Monkey
Jul 30, 2010
430
0
Sandy Eggo
i think the builder is the most important part. an experienced builder knows all the subtle tricks.
that being said, an experienced builder showed me all his tricks and i'm ready to build another set of wheels cause round one went great and has withstood some serious street pounding on my DJ bike.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,850
9,556
AK
Alloy nipples are a bad idea 95% of the time. It's cool that you can build a wheel with good even tension that will hold up for the most part (did this all the time in the shop, and do it for myself with my TS-2 and assorted tools). Totally even tension is how it leaves the wheelstand, then you ride it, and at some point you will likely have to make some changes...The problem is later when it needs a truing. They are soft and round out easily without excessive tension, if they've seized just a bit, they can break/crack/round out. Brass nipples are MUCH stronger, and if your wheel is a few mm off, it's MUCH easier to bring it back into "true" than with alloy nipples. The higher tension threshold of the brass may be necessary to bring it all back in true. They USED to make a splined-drive alloy nipple that was MUCH better than standard alloy nipples. I don't know why those fell out of favor. If you plan to change your rims each season, maybe alloys are not a bad idea. I've used them, lots of super-comps, revolutions, and other light stuff before.


One major area that people and especially "package deals" fall short with is the fact that the front wheel doesn't need to be as strong as the rear. Most of your weight's on the rear, it sees far greater forces. Most rims that are thrown out of true are usually rears. Sure, it happens to the front, but not as often. For this reason, you can "lighten up" the front and have an equivalent amount of strength. Lighter (more aggressively butted) spokes, or fewer spokes, a slightly lighter rim, etc. I've ran wheelsets like this for a long time and never had a problem with the front.
 

baca262

Monkey
Aug 16, 2011
392
0
One major area that people and especially "package deals" fall short with is the fact that the front wheel doesn't need to be as strong as the rear. Most of your weight's on the rear, it sees far greater forces. Most rims that are thrown out of true are usually rears. Sure, it happens to the front, but not as often. For this reason, you can "lighten up" the front and have an equivalent amount of strength. Lighter (more aggressively butted) spokes, or fewer spokes, a slightly lighter rim, etc. I've ran wheelsets like this for a long time and never had a problem with the front.
this has always bugged me too - why would one want to build a front wheel with a 600-700g rim and a 2ply tire? :think: i understand that there are places that would actually require this but in most of the cases it's unnecessary. saving weight on the rotational mass of the front wheel can do wonders for handling.
 

Prime320

Chimp
Jun 2, 2012
4
0
I'm new to mountain bikes (BMX for 20+ years, and dirtbike racing for 10) and wheel strength has been something that has me worried. These days I am old and fat. I am 100lbs up from what I weighed a decade ago, but I still don't give up on this stuff. I am currently building my first DH bike and want a wheel that will last with my 300lb weight. I tend on abusing the bike and being far from smooth. I am sure I will be doing big drops and using stair sets as landings when I am bashing around town, and I doubt I will be scared of decent sized drops in the woods.

What should I be looking at for wheels? 300lbs, and I don't want to replace anything anytime soon. I don't care about weight at all. Strictly durability. If I never had to replace anything wheel wise I would be a happy guy.
 

iRider

Turbo Monkey
Apr 5, 2008
5,648
3,089
this has always bugged me too - why would one want to build a front wheel with a 600-700g rim and a 2ply tire?
Not the rim, but a 2-ply all the way! Normally you can ride out a failing rear wheel/tire w/o crashing, front wheel/tire, not so much. Light rim, 2-ply tire FWIW.
 

baca262

Monkey
Aug 16, 2011
392
0
Not the rim, but a 2-ply all the way! Normally you can ride out a failing rear wheel/tire w/o crashing, front wheel/tire, not so much. Light rim, 2-ply tire FWIW.
you do have a point there, you can also ride home on a flat 2-ply. i guess it depends on the pressure you ride and how much sharp rocks is there, i never actually pinched my front tire on the trail (happend a few times on stairs and curbs but i never had to panic stop because of it).

my trails have almost no sharp rocks and i ride at 1.8bar (26psi, both wheels) and i'm really light (60-62kg) so i never needed 2-ply up front, i rarely need it at the rear too.