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I've always assumed single speeding increases the forces going through the rear hub bearings and freehub
However it occured to me in a recent conversation that perhaps it doesn't, and having gears is really just like using a longer-handled tool to tighten a bolt to the same torque
(Assuming you are accelarating, climbing, whatever at the same speed/rate, that is)
So single speeding only puts more force through cranks and bb
Am I missing something?
No idea but my related and occasional pondering is….…..
are forces greater if run a SS setup on a regular hub rather than an SS hub? In my head the chain line in a regular hub run SS is further from the hub shell so more leverage or whatever on the hub shell and bearings compared to an SS hub. I’ve always assumed this but no idea if an actual basis to it. It’s stopped me using a regular hub.
if you're going the same speed, the force applied to the freehub mechanism is the same either way - either less torque at higher rpm though a lower gear or more torque at a lower rpm - the casette is multiplying/dividing it to the exactly same number.
however, the forwards torque (chain pulling the hub towards the bb) on the singlespeed is higher at lower rpm, assuming the same size chainring/cranks. so if your singlespeed is geared such that your average rpm is less than a geared bike, there's more force pulling the hub to the front of the bike, being resisted by bearings
in reality, I suspect the differences are small enough as to make no meaningful difference to hub life
My SS race bike is on a 2009 hub and it's fine (Tune Princess with spacers instead of a cassette) The seals are rubbish so it's dry weather only but that's a different issue. In the wet I use a Chris King ISO and that's faultless, but a little heavier.
My everyday bike is an SS Cotic Escapade, that's got a CK R45 rear hub which has been faultless, I've had it a couple of years and it was second hand when I got it.
So IME no issues at all caused by SS, even on a normal geared hub.
Someone once told me that the weird torque of SS bikes means carbon is unsuitable as it can cause early fatigue. Anyone know if that's true? Doesn't bother mean, the race bike is titanium and the everyday bike is steel but just wondering. It's almost entirely steel and titanium at SSUK for instance but is that just fashion?
No difference. Never noticed any issues when I was commuting on a fixed gear, carrying heavy panniers.
No, because Gears. Two riders of the same weight climbing the same hill at the same speed will put the same average load on the hub regardless of the gear they're in (or the lack of).
There might be some difference in peak loads to the increased propensity to stand up and "smash it" up the hills.
I edited my post - @whatgoesup is right. Torque on the cranks and tension in the chain is greater when SSing, but if you are going up a given hill at a given speed the wheel torque is always the same (assuming the same sized wheel). The leverage/moment at the cassette will be different, and that is what affects the cranks/chain/your knees.
I'd expect forces from the rider to be dwarfed by the battering those same bearings take from rocky ground.
Someone once told me that the weird torque of SS bikes means carbon is unsuitable as it can cause early fatigue.
Carbon is not subject to fatigue like metal frames.
Nope, or certainly within the margin of error so worse hubs are always worse whether SS or geared.
Of my SS builds hubs:
Hope XC - no problems
Salsa SS - seemed to go though bearings, not quickly, but not exactly long lived either.
Hope Pro2 - cracked the hub across the body like they all did
Fulcrum - no problems
A2Z ultralight - no problems although others reported freehub pawl failures but that's a flaw in the design overall not an SS issue.
Track style hubs - never an issue
It’s almost entirely steel and titanium at SSUK for instance but is that just fashion?
Fashion and availability. I can only think of the Ibis and On-One Lurcher carbon SS frames and steel / Ti suit small batch niche production runs.
I've never worn out or broken a cassette free hub when running SS, got through plenty of cogs/chainrings though. I think SS is lazy way to ride, & that's not because its easier because in the majority of cases it isn't. It's a grab & go bike requiring virtually zero prep or maintenance, & that suits me for the often short & unplanned rides I do, max of 1 hour or so usually. When riding its pedal or don't. Pushing is ok. Folk running those 52 tooth dinner gongs as chainrings must be going slower than walking at 32x52 !!.
Current SS on the fatty was just a cheapo kit on a regular On-One fat wheel, Emental I think the hub make is.
Sunday best SS set up is a Surly SS hub with a White Industries trials freewheel. It sounds lovely.
only if the chain tension is tighter than a nun's chuff. Magic gear ratios or early Gates belt drives where a bugger for killing hub bearings, ( I killed 2 hubs in super quick time with first Gen gates carbon drive) but a well set up singlespeed, nah it's not a major issue.
OK cool, yea this all makes sense.
The conversation that brought this up for me was actually about Pinion's. Someone thought theirs was killing their rear hubs, as rather than increaing the lever length to achieve higher torque, as a cassette does, the gearbox gears down and then applies greater force through the belt/chain, through the same size rear sprocket.
I suggested it may instead be that their belt tension is too high.
Hope Pro 2 Singlespeed hub here, would be 11 yrs in september and not new to me... still on original bearings and pawls and still spins for ever and sounds like an angry hornet
Yes. From experience. Serviceable hubs are a must.
Averages don't matter.
Sunday best SS set up is a Surly SS hub with a White Industries trials freewheel.
Do you find your cranks rotate if you are pushing your bike? I also have a bike with the WI trials freewheel but it's always bugged me that it rotates the cranks. I've stripped the freewheel and replaced the bearing but it's still the same. Great freewheel though, super fast pickup.