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  1. #1
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    Tire Pressure vs Spoke Durability

    Hi i went to my LBS for the 3rd time for my rear 26" MTB wheel as 2 of the spokes snapped off These wheels have seen at least 12k km and it seems spokes come off every 4k km like clockwork After a chat with the bike mechanic he noticed i have swapped my usual 2.3" MTB tires for 1.25" slicks. He advised me that with higher pressure, spokes might be more likely to be damaged? Is this true? My feeling is the wheel has seen much wear and tear anyway and could be it's time for a new rear wheel? I do admit though i mostly use the MTB for commuting rather than offroad these days and noticed instantly how thinner, higher pressure tires result in a far harsher ride! Should i switch to thicker commuter tires or get a new rear wheel? As a guide my tire history 2.3" 35-50 PSI F/R now 1.25" 80-90 PSI F/R

  2. #2
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    Im not able to answer your question, but I am really interested in the inner width of your rims - jumping from 2.35 to 1.25 is pretty huge, I have a very small suspicion that the slicks are too thin for your rims.


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  3. #3
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    Possibly... higher pressure can affect spoke tension sometimes. Reducing spoke tension can mean larger load cycles on the spokes, which could lead to increased fatigue susceptibility.
    A lot of "ifs," but the answer is "maybe."
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  4. #4
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    Me be think'n spoke tensions too high.
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  5. #5
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    After breaking spokes multiple times around a wheel, and continuously only replacing the broken spokes, the unreplaced spokes drastically weaken due to multiple retruing and high stress sessions. After multiple spoke breaks it is time to relate the whole wheel, pretty plan on the continuously breaking spokes. Also if the wheel is being tensioned unevenly to pull to true breaking spokes is more likely.

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  6. #6
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    12,000 km is A LOT of miles for a mountain wheel. Of course it depends on riding style and weight but I would never get that much and never would expect it, especially on a rear wheel. Higher air pressure equals lower spoke tension but I think the main issue is how old the wheel is.

  7. #7
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    Sounds like you've got some good miles on those wheels, but not knowing what the build is, kind of hard to give any proper help. My thoughts are that the higher pressure is compressing the rim, dropping spoke tension and there's nothing that fatigues a spoke more than being loose.

    Where are the spoke breaking, at the hub, in the middle or at the nipple? What is the wheel build?? Info OP, it helps people help you. For me, once you break more than 4 spokes, something's up and the wheel should probably be re-built.

    Also bit of a suggestion, try dropping the pressure on those tyres 80-90 PSI on a 1.25" tyre is damn high and will be harsh.
    One day your life will flash before your eyes, will it be worth watching??

  8. #8
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    Spokes can go hundreds of thousands of miles if the wheel is built correctly, so tire pressure has little effect on spoke durability. People wear rims out, or they crack and break at the spoke holes, and relace a new identical rim in with the same hub and spokes.

    Now, if you get a stick in the spokes, they can break...

  9. #9
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    Quote Originally Posted by hodak View Post
    1.25" 80-90 PSI F/R
    Those pressures are better suited to road rims and are excessive for a 1.25 tire. Try running something in the 60s for better ride/handling/rolling resistance/durability.

    The spoke tension definitely drops as you pressurize the tire, some rims 'shrink' more than others. You can partially combat it by double checking the spoke tensions after the tire is aired up.
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  10. #10
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    Wow did not expect so many helpful replies! Ok more info since requested

    Hardtail, currently commuter duty wif front suspension locked
    Rims : Alex XC-44, internal width : 17mm
    Rear Hub : Shimano FH-RM35
    Spokes are breaking mostly @ hub side.
    Ok i'm 85kg now and when i 1st got the bike i was 108kgs! Actually lost weight till then haha
    Hmm ok i think i shall drop the pressure but for "stock wheels" i get the feeling getting 12000 km out of em is already decent?

  11. #11
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    Quote Originally Posted by hodak View Post
    Wow did not expect so many helpful replies!
    This message board attracts a lot of older, more experienced riders. Usually when there's disagreement it's nuance or one person is fkn clueless. It's a good resource. Most of the responses here come from people who REALLY know their shit. It's pretty cool.

    Quote Originally Posted by hodak View Post
    Hardtail, currently commuter duty wif front suspension locked
    Rims : Alex XC-44, internal width : 17mm
    Rear Hub : Shimano FH-RM35
    Spokes are breaking mostly @ hub side.
    Ok i'm 85kg now and when i 1st got the bike i was 108kgs! Actually lost weight till then haha
    Hmm ok i think i shall drop the pressure but for "stock wheels" i get the feeling getting 12000 km out of em is already decent?
    Running a fork locked out most of the time tends to result in unlubricated fork bushings destroying the stanchions. It sounds like you'd be better served with a quality rigid 'hybrid' bike, and adjusting the cockpit to suit your taste. It will be lighter, with gearing/wheels/handling behavior that suit your application. It's worth considering.


    We're not going to be able to go in to tons of depth about those wheels. Low rent shimano hubs tend to explode under high power, but you won't see that commuting. Nobody runs alex rims in a performance application, but they're not garbage or anything. You're an extreme use case. Pretty cool.
    "Things that are complex are not useful, Things that are useful are simple."
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  12. #12
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    All of what Scott said, especially the more purpose suited bike, even a rigid MTB would be a better option. If it's a better sus fork, i.e. air spring, then suggest you flip it over every so often to let the oil lube the bushing and stanchions and honestly, unless you're standing and hammering, you could probably ride with it open and let it do it's thing without it hampering your performance. Your rims aren't too wide for those tyres, that's what I was curious about.

    Yes, you've got good use out of those wheels, no doubt, I'd seriously consider getting a quote from your shop for a rebuild and then compare that to what you could get a new set for, maybe look at some wider options if you're thinking of hitting proper trails to better support true width MTB tyres, then rebuild your old wheels yourself, not too hard if you have patience, the resources are easy to find.

    One way to find out if your tyre pressure is effecting spoke tension is to squeeze a few pares of parallel spokes at your high pressure, then drop the pressure down to around 30 PSI, then squeeze them again, if you can feel them get much tighter when the pressure is dropped, then, yes, the high pressure is de-tension your spokes because your rim isn't the best. So you have a better idea of good spoke tension, go into your local bike shop and squeeze the spokes on some of the wheels of bikes on the floor.
    One day your life will flash before your eyes, will it be worth watching??

  13. #13
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    Well about going rigid, etc - i am actually practicing longer distance on roads on my HT because i plan to have my next bike as a bikepacking rig Would go with a 29er HT frame and a rigid cromo fork? Actually what exactly makes a super strong rear wheel that won't quit fully loaded? A combo of more holed rim, stainless steel spokes for example? Titanium spokes not worth it/snake oil? What are long lasting/quality value for money hubs? I would go maybe custom wheels next build so always good to learn from the experts

  14. #14
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    Quote Originally Posted by hodak View Post
    Well about going rigid, etc - i am actually practicing longer distance on roads on my HT because i plan to have my next bike as a bikepacking rig Would go with a 29er HT frame and a rigid cromo fork? Actually what exactly makes a super strong rear wheel that won't quit fully loaded? A combo of more holed rim, stainless steel spokes for example? Titanium spokes not worth it/snake oil? What are long lasting/quality value for money hubs? I would go maybe custom wheels next build so always good to learn from the experts
    A strong wheel will have plenty of butted spokes, a conservative rim design, and even spoke tensions. Rims with an offset spoke bed and clever hub designs are used to minimize the tension imbalance from drive side to NDS spokes. A good wheel build is important. Rims are designed with the tire in mind; road rims 'compress' less from tire pressure, mtb rims are more impact resistant and won't get ripped apart by the tire pulling the bead hooks apart.

    Ti spokes are 'stretchier' than steel, and generally a waste of money. DT350 hubs are well regarded for durability, not terribly expensive (~150$ if you look around), and a doddle to service.


    With a suspension fork they're not intended to be used locked out for super extended periods. The bushings cycle that 2-3mm of movement and wear away the lube oil in that spot on the stanchions.


    I don't see any reason to run more than 60psi on any bike that's running >30mm tires. It doesn't roll faster.

    If you're riding on roads and simple dirt roads a gravel bike might suit your interests. It's worth considering.
    "Things that are complex are not useful, Things that are useful are simple."
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  15. #15
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    Ok thanks all for the advice, tips and suggestions! I guess 80-90 PSI is on the high side? Reason i went with high is because it's in 26" rather than 29er/700c and i saw 65-100 PSI recommended pressure printed on them tires (Panaracer T-Servs) I have since dropped 65/80 yesterday and went out on a ride and all seemed well! For my bikepacking rig : i tried dropbars and being a BMX/MTB guys all my life just couldn't get used to them lol. Also it appears 29 HT wouldn't have tire clearance issues i see even some pricey cyclocross/gravel frames have?

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