Got a DH wheel laced up by a local shop. They used plain guage spokes and nipple freeze. Rode on it for one weekend (albeit a SDA race weekend) and the spokes are noticably loose.
Now I've had wheels built before and been told to pop in for a checkup after a few 100 miles- but this isn't right surely?
I will of course be going back to the shop to give them a chance to resolve it.. but not exactly confidence inspiring!
new ones of mine usually go after one weekend at herts then they get a true and never go wobbly again.
New wheels can do this. Its basically bedding in.
Bedding in is a myth perpetuated by rubbish wheel builders. Properly built, tensioner and relieved wheels should never need to be re-truer unless they get damaged. You need to get a better wheel builder
That really doesn't sound good at all. Sounds like the wheel builder has the kit but knows jack... if he's using spoke freeze, but obviously doesn't know the basics first!
Unless of course you've flat spotted the rim & that's what has made the spokes loose?
matthew_h + 1 - if they need bedding in and re-truing then they weren't built correctly in the first place.
Ok ok. the last time I had a mtb wheel built was 7yrs ago!
There is a dent- but no flat spot as far as I can see. Loose spokes are in clusters of 2/3 intermittently all the way round.
Thats not going to help your case m'dear!
No- but it is a DH wheel and I've done far worse before with no spoke issues.
Disagree now. Its your bad luck but I personally wouldnt blame the bikeshop.
I'm not so sure. I'll admit my wheelbuilding knowledge is limited, but a ding to a sidewall on a rim shouldn't mean that the whole wheel loses tension. I'm suprised its dented as it wasn't a hugely rough course but suspect that I'm going faster not smoother..
The MTX that went to France two years ago ended up with the rim folded in to amost touching the centre, and it was still tight..
v rockthreegozy - MemberNo- but it is a DH wheel and I've done far worse before with no spoke issues.
Im sure the shop will take that into consideration. Obviously dents mean the wheel HASNT been abused then....
Theres one ding- its been ridden for DH and as much as i'd like to be as smooth as the pros, its not always the case 😉
Can someone who builds wheels explain why a ding to the sidewall would cause this?
A ding- did you pinchflat? It could be that you punctured and then whacked a square-edge rock very HARD. That could damage any wheel.
I didn't puncture nor was I running less than 30psi.
The ding isn't an issue- its still going to be used.
Dents just mean that you're not running scardy-pants tyre pressures!
When you get it back from them ping all the spokes. They should all make about the same note on each side. The ones by the weld are sometimes a little different. if they're all over the place then its a poor build.
Can someone who builds wheels explain why a ding to the sidewall would cause this?
A ding will generally only cause a flat spot in a loose wheel, unless it's a monster whack and pinches the tyre as well
My guess - not enough spoke tension. sounds to me like the poor wheel build weakened the wheel and allowed the ding to happen.
I'd take it back to the shop and ask them to retrue it and tighten the spokes.
nope.. dings just happen due to tyre pressure. if it was loose it would become a flat spot. Higher tensioned spokes can take more compression before they flex and stop supporting the rim. It sounds like the wheel had enough tension overall to support it, but the builder didn't ping the spokes to find and even out the tension on all of them
Plain gauge spokes - uggh.
My guess is the builder simply didn't tension them high enough for their intended use or stress relieve them well enough during the build, either that or uneven spoke tension which will also cause many spokes to loosen when used. IMO DH racing is the worst abuse you can give wheels.. you spend the whole weekend trying to get from A to B as quickly as possible with little to no regard for where you put them and you'll rarely check them over.
I've built my own wheels for years and years but occasionally I'll buy wheels built by online shops like Merlin/CRC (as it's far cheaper than buying the components seperately) and have never found a mail order wheel tight enough for my liking.
Which shop was it, Wheelcraft?
I can assure you that flat spots are not only caused when spokes are loose.
sounds to me like the poor wheel build weakened the wheel and allowed the ding to happen.
Not true (no pun intended...). A little dent to the rim, as described by the OP, could happen on any quality of wheel build. As he's said, the little dent isn't really an issue.
The issue is that the wheel simply should not have loose spokes, after any amount of time, unless it actually gets properly flat-spotted (written-off rim). matthew_h is on the money: re-truing after a few weeks is a myth. The spoke tension should be checked and perfect at the time of building, if the wheel builder is any good (and, not to blow my own goat, but I'm a pretty fair wheel builder).
Sounds like the wheel build was a little shonky in the first place. I'd get them to re-build it, and not use cheapo plain-gauge spokes. There's no reason to ever use plain-gauge, other than cost.
I stand corrected.
Wheelbuilder here.
allthepies - Member
matthew_h + 1 - if they need bedding in and re-truing then they weren't built correctly in the first place.
+1 also. Unless you've actually damaged the rim (eg hit it hard enough to flat spot it or bend it (side to side) then the spokes shouldn't come loose. On the face of it, the wheel was simply built too loose.
I can assure you that flat spots are not only caused when spokes are loose.
I wasn't saying that. You would need to hit a tight and even wheel a LOT harder to create a flat spot.. Hence why tyre pressures and pinch flats are an indication.
[edit].. Anyway, op has a crappily built wheel. PG spokes don't help; they should always be DB as they conform to loads better, and don't transfer so much force to the rim.
When I've built wheels in the past, I've always spent a fair amount of time stress relieving the spokes, then re-tensioning and repeating till all spokes are of an equal tension and theres no stress in them.
I think I over turn the nipples too, so if I want to add half a turn I add 3/4 then back off a quarter to stop the spokes from twisting.
When I first ride the wheels, non of the spokes tend to make that 'ping' noise i.e. they are al-ready all bedded in.
I never have to re-true after a few rides either.
Id guess your wheel builder never did any of this.
i dont know much about wheel building or material properties but my old dh wheel did exactly the same thing, straight gauge spokes with ex729 built by crc. lost tension on its first outing at an uplfit day at inners, but i got it retensioned and no problems afterwards for a few years. maybe its to do with the spokes stretching? wouldn't use straight gauge again now mind as it seems the cost incurred from getting that wheel sorted out negated the cheaper spokes...
NOT Wheelcraft. No problems with Als wheels
Bedding in is a myth perpetuated by rubbish wheel builders
bedding does happen - but yes from rubbish wheel builders. my first set of wheels did a lot of pinging - but didn't need retruing - second set of wheels were fine.
Bedding in is a myth perpetuated by rubbish wheel builders. Properly built, tensioner and relieved wheels should never need to be re-truer unless they get damaged. You need to get a better wheel builder
disagree, spokes stretch, like cables do.
the best wheel builder i know by far, asks that wheels are brought back to the shop after a bit of riding and he retensions everything.
they have never been out of true when mine have gone back for a retension, but they have also NEVER even developed a slight wobble, after 5 years of hard abuse of light wheels.
this is of course part of the price of building a wheel, not an extra.
i wouldnt ride a brand new wheel on full on DH weekend personally, i wouldnt give it a hard time for the first week or so.
and a flat spot has nothing to do with spoke tensions whatsoever.
unless your rims are made of cheese and the wheel was built by a chimp.
Edit
I wasn't saying that. You would need to hit a tight and even wheel a LOT harder to create a flat spot.. Hence why tyre pressures and pinch flats are an indication.
tyre pressure and pinch flats are an indication of what exactly
You're right, flat spotting is down to how hard you hit a well built wheel and the strength of that particular rim (given the same quality of build)
from experience, I've flatspotted DH rims (721s 729s, WTB speeddiscDH to name a few) running dual plys and DH tubes at 40-45psi without puncturing and vice versa I've done a whole run from the deer gate at fort william on a flat rear tyre without a single ding on another rim (Sun Doubletrack)
where do you get your information from?
i wouldnt ride a brand new wheel on full on DH weekend personally, i wouldnt give it a hard time for the first week or so.
How would you manage that then?
rear DH wheels only fit DH bikes and DH bikes only work on DH tracks.
are you really saying you'd waste the petrol money to get to a DH track and mince down all day coz your wheel is "new"
FFS!
use a wheelbuilder you trust or build your own
and a flat spot has nothing to do with spoke tensions whatsoever.
unless your rims are made of cheese and the wheel was built by a chimp.
er... no.
A flat spot has everything to do with spoke tension. If you don't think so then you don't understand how wheels work. The supporting pressure of a spoke is equal to it's static tension. The wheel stands on its spokes; it doesn't hang on the ones above.
i do build my own and havent had a problem with any of my wheels.
cheers 🙂
The wheel stands on its spokes; it doesn't hang on the ones above.
riiiiiiight.
i suppose that makes 36spoke wheels stronger, as the "next spoke" its "standing on" gets under the hub quicker.
maybe you should invest in some of Mr S Browns POWer wheels?
http://www.sheldonbrown.com/power_wheel.html
the hub is supported equally in all directions mefinks, and a flat spot is cause by a "ding" in the rim, which may or may not cause a pinch flat, depending on how the tube and tyre align during said "ding"
lol @ thread .....
Im with gw .....
Olly, you have no idea how pre-tensioned engineering structures work.
The pre-tensioning is supported by the rim. any compressive forces on the rim act as a reduction on the tension... A reduction on a tensive force is a compressive force. And yes, 36 spoke hubs are stronger for exactly that reason.
spokes stretch, like cables do.
absolutely; and whether cables or spokes and mechanic worth their wages will pre stretch in the workshop so that the rider/ customer never sees the resultant stretch.
bikewhisperer - MemberThe wheel stands on its spokes; it doesn't hang on the ones above.
Rubbish - spokes have no strength in compression and a lot in tension.
The wheel hangs from the spokes at the top.
jesus.. you lot are hilarious.
spokes have a LOT of strength in compression, provided they are pre-tensioned.
trail_rat - Member
lol @ thread .....
Quite! 😀
The whole Jobst Brandt thing about bottom spokes supporting the wheel may be one analysis of a sheel structure but it's misleading and pointless.
Olly - Memberdisagree, spokes stretch, like cables do.
Nope. Spokes bed in which gives the appearance of stretch - if they aren't tight and haven't been properly stress relieved.
Cables don't stretch either - it's all the cables & ferrules bedding in.
Cables don't stretch either - it's all the cables & ferrules bedding in.
amen
The wheel hangs from the spokes at the top
...and doesnt the overall tension in the spoke have to be greater than the force it will receive from the opposite side etc? Something like that in the Wheelpro book anyway!
if wheels stand on the spokes below... how come the nipple doesnt thread into the rim? the spoke would just fall through into the tube?
some bizarre ideas here..
bikewhisperer - Memberjesus.. you lot are hilarious.
spokes have a LOT of strength in compression, provided they are pre-tensioned.
utter tripe - a pretensioned spoke is in tension. Compress it and you remove some of the tension. It remains in tension. However it is supporting no weight at all - it is in tension. the weight is sported by the top spokes
A spoke has no strength in compression at all - it just bends.
if wheels stand on the spokes below... how come the nipple doesnt thread into the rim? the spoke would just fall through into the tube?
It's because it's PRE-TENSIONED. If the spoke tension was too low then the greater force of the compression that the bike hit would be more than the tension in the spoke, so the compressive force would out-do the available strength. Then the rim would be the only bit opposing the compressive force, and if it was too great it would bend.
EDIT.. thanks TJ
dont shout pre-tensioned at me!
regardless of if its in tension or not, the spoke is not supporting weight. i.e the hub is not standing on the spoke, it is hanging off the one above...
bikewhisperer - MemberIt's because it's PRE-TENSIONED. If the spoke tension was too low then the greater force of the compression that the bike hit would be more than the tension in the spoke, so the compressive force would out-do the available strength. Then the rim would be the only bit opposing the compressive force, and if it was too great it would bend
Therefore the bottom spokes are NOT IN COMPRESSION 🙄
Ah, forget it. You are welcome to continue being wrong.
ok big boy. slow clap for you being so damn right about a pre tensioned structure suddenly being able to support load, despite not being constrained at the bottom end.
bikewisperer - you are talking utter tripe - a spoke has no strength in compression at all. None. It just bends.
In a spoked wheel all the weight is hanging from the upper spokes - the bottom ones carry no load at all. None. Not 1 g of the weight.
At rest with no weight loaded all the spokes are in tension. When a load is applied the upper spokes gain more tension, the lower ones loose tension - thus the load is hanging from the top spokes.
where you are getting confused is the entire wheel has strength in compression. Put a load on the rim from the top of the rim the wheel wiill try to go eggshaped - but the spokes front and rear will resist this as the tension in them increases while the tension in the to and bottom ones decrease.
it basic mechanics. A spoke has no strength in compression whatsoever
bikewhisperer; show us some numbers.
TJ... If you put tension on a spoke then it has compressive strength to resist that amount of tension. Above that point it will bend. I've got no prolems with that bit.
The net force on a bike wheel is compressive on the bottom spokes.
Yep BW up to you to prove this.
I think I can see your point but for me it is meaningless. If one were to cut a bottom spoke in the wheel, it would ping apart in 2 AS IT IS STILL IN TENSION. The fact that it is in less tension than the other spokes does not make it "in compression".
thats just not right buddy. thats not how it works. if anything, the pre tension reduces its resistance to compression...
Plus, unless you've built radially spoked wheels (and they'd have to be perfectly radial which will never happen), the spokes can never be in compression because even if they couldn't bend, they'd simply rotate in the spoke hole in the hub.
Cynic-al.. Can you imagine a spoke being compressed enough to equal its tension? It's the resultant overall force I'm talking about, not the force on individual spokes. Even so, when you even out the forces, wheels do stand on their lower spokes. All the other forces cancel out.
Can you imagine a spoke being compressed enough to equal its tension
That's what happens on loose wheels (or tight ones that have been loaded very heavily!) and what happens? The spokes bend and rotate in the spoke holes. They don't support load in compression.
That's what happens on loose wheels (or tight ones that have been loaded very heavily!) and what happens? The spokes bend and rotate in the spoke holes. They don't support load in compression.
rotation is not a problem. if they were built well then that wouldn't happen. If they were built with prolock or spoke freeze then also not a problem, unless they were not relieved. If they were not relieved enough when they were built then they might have this problem.
No, not rotation of the spoke in the nipple 🙄 Rotation of the spoke in the hub.
bikewhisperer - MemberTJ... If you put tension on a spoke then it has compressive strength to resist that amount of tension. Above that point it will bend. I've got no prolems with that bit.
The net force on a bike wheel is compressive on the bottom spokes.
Nope - no spoke is ever in compression until it becomes lose and then it will bend
bikewhisperer - Member
Cynic-al.. Can you imagine a spoke being compressed enough to equal its tension? It's the resultant overall force I'm talking about, not the force on individual spokes. Even so, when you even out the forces, wheels do stand on their lower spokes. All the other forces cancel out.
I can see this, I just can't see its relevance when discussing spoke tension in wheel builds.
The spoke will bed in at the hub. If the wheel is built well then this won't be a problem.
I can see this, I just can't see its relevance when discussing spoke tension in wheel builds.
well that's not my problem.
The spoke will bed in at the hub. If the wheel is built well then this won't be a problem.
Seriously? You really don't understand wheels.
bikewhisperer - MemberI can see this, I just can't see its relevance when discussing spoke tension in wheel builds.
well that's not my problem.
Whoop de ****ing doo for you, you've still not justified it 🙄
Bikewisperer - maybe this will explain it to you
http://hea-www.harvard.edu/~fine/opinions/bikewheel.html
You are I am afraid totally confused about how a wheel works. Have a read and a think
No spoke is ever in compression. No spoke can hold a load in compression. The load hangs from the top spokes
Edit -It is possible to build a wheel with string that has no ability to hold any sort of load in compression
well what do you want me to do? Teach you a physics a-level?
And Clubber.. yes spokes do cause deformation of hub flanges. I wasn't suggesting otherwise. Stress relieving while building will resolve this.
In mathematical terms it is possible to describe the bottom spokes as being in compression. The have less tension than they had before, so if you count the starting (pre-tensioned) state as the zero state, you have put them "in compression". The reason they can support this compression is that the spoke has been pre-tensioned.
Thanks tj
Bikewhisperer, stop trying to re-invent the wheel
bikewhisperer - Member
well what do you want me to do? Teach you a physics a-level?
Already got that thanks, my point is that yours is just irrelevant to the discussion, seems most others are with me.
bikewisperer - nice selective quoting.
Answer me this. Bike stationary, rider on the seat. The spoke that is vertical from the bottom of the wheel to the hub. Is this in tension or compression?
Edit - higher physics here
[img] 
[/img]
Was that you cycling to work earlier?
If you get an elastic band and stretch it (call this point A) then release half of that stretch (point B), it's still in tension though from point A to point B you have 'compressed it' in the sense that it has shortened. It has still at no point been in compression. Same for the spokes.
EDIT - A grade Physics A level and Masters in Mech Eng since we're now quoting qualifications 😉
Oh, and a BSC - Bronze Swimming Certificate
Already got that thanks, my point is that yours is just irrelevant to the discussion, seems most others are with me.
yep. me too. So lets go with the "my gang's bigger than your gang" logic and say you won. hubs hang from the upper spokes and tension has nothing to do with compressive strength.
Correct at last. You cannot have something in compression and tension at the same times. Tension is nothing to do with compressive strength. As I said earlier you are confusing what happens to the component and to the entire built up wheel.
You cannot have something in compression and tension at the same times.
cough
bending
cough cough
so if you count the starting (pre-tensioned) state as the zero state, you have put them "in compression"
Not the same as actual compression, just means that the tension is lessened.