29er – how much slower will I be all other things being equal over an 80k / 4h ride carrying an extra 319g and 509g at the wheels?

I realise mostly comedic posts will arise, but one serious equation / answer to both weights would be appreciated…

😀

depends on the hills and amount of acceleration you have to do but not measurable I would guess. Weight only matters under climbing and acceleration

How much do you plan to shed by over thinking things again….. 😉

It all becomes pretty meaningless because it depends how stop-start you ride and how you react to the feeling of weight- I reckon the biggest factor for me is my XC bike has nice lightish wheels and because it feels fast I tend to go harder. When it had my spare, heavy wheels in it felt lethargic and I couldn’t be arsed.

1kg = ~1min per 1000m climb
Since we don’t know the answer, lets just assume that extra efforts for acceleration are balanced by maintaining momentum better over rough stuff.

1min per 1000m climb

1000m climbing is most of a days climbing on a decent length ride for most folk isn’t it? So, a minute in 4 to 4 and half hours on the bike…matters if you’re racing, probably not in the real world.

It also only matters if your going at your speed all the way, making it into a corner in front of somebody could get you 2 mins…
Race smart and don’t be the guy walking home with snapped wheels

matters if you’re racing,

Well, its for the Scott Marathon at Wantage which has more than 1000m of climbing, and its kind of a race, with myself at least.

829g weight saving on your bike, concentrated on the wheels….

If it’s a twisty route where you need to accelerate regularly I think it could have an decent impact, say 30 seconds per 10k as a wild guess

1000m climbing is most of a days climbing on a decent length ride for most folk isn’t it?

1000m isn’t a huge amount over 80k, but it depends how it comes at you

See you there Kryton!
I did the 100km one last time round. Some of the climbing is short & sharp where you’ll be stopping and accelerating, that said you keep momentum well on the long flats.
For Wantage specifically I wouldn’t bother with lighter kit. I’d make sure you’ve got enough food and water though, I got caught out a bit. Possibly an extra tube as with all the hedges around they cut them this time of year leaving lots of thorns that can shred your tyres.

and its kind of a race, with myself at least.

If it’s a race with yourself, just take a minute off your time, guaranteed win.

829g weight saving on your bike, concentrated on the wheels….

Not both together. To explain I was considering a wheel purchase, but only of it makes a difference to the bike.

a) Current – Probuild/Chosen my “Trail” wheels at 1915g
b) AC Wide Lightnings – 1597g cost £495 so -319g
c) AC Race – 1404g cost £600 so -509g

Personally, as I’m not going to be troubling the top ten its not worth buying lighter wheels. The rest of the bike – and Anthem 29er – is pretty much as light as it will go being covered in KCNC & MT Zoom plus 1 x 11.

But then my OCD got curious about how much difference each weight saving would make, just for kicks!

and its kind of a race, with myself at least.

I predict a draw.

A no score draw.

followed by further “how to go faster than myself” threads

1000m climbing is most of a days climbing on a decent length ride for most folk isn’t it?

If you don’t go anywhere very fast in a day it is.

As for wheels, probably **** all. I’d love a set of DT carbons to replace the XR331’s I’ve got, but it’d make bugger all difference to my placings.

Did 1000m of climbing in a short day yesterday mostly off-road with short bits of road to connect things up, about 5hrs of riding, didn’t feel too hilly.

As to the OP’s question – fitting tyres that maximise grip whilst reducing drag would probably have more effect. Depends on the course/conditions of course.

It won’t make much difference, unless one of the wheels folds halfway through the ride. Worth it as part of an overall weight saving across the bike, although I would start with tyres where you can save rolling resistance and weight (although the lifespan is somewhat limited…), rolling resistance will make a much bigger difference.

If you really want to go faster than yourself, you’d be best off spending the £495 on a heady cocktail of shrooms, LSD, ketamin and weed and having an out of body experiance*. 😆

*Results and survivability of participants not guarenteed

Oh, and in response to how much faster, if it was all uphill so that the only thing that mattered was weight, you’d be around a minute faster. In reality that’s not the case, so 30s or so maybe. Put a tighter T shirt on, carry less kit etc. etc.

Acceleration and rotating mass isn’t really as important on a long MTB ride as it’s not going to be decided by a bunch sprint.

Yes – if it was all uphill, 500gm is 0.5% of 100kg rider+bike so 0.5% of 240mins = 1.2 minutes.

But it won’t be all uphill so it’ll be worth **** all.

If the acceleration/deceleration things was significant it’d have been calculated through measurements & extrapolation by mfrs – it hasn’t.

Come on, people. The OP wants to buy new wheels and everyone’s denying him the pleasure.

I say they’ll feel great. buy them. Even if it’s only a placebo, it’ll be a nice placebo on a long ride. You can even buy the less expensive set so that you’re being fiscally responsible while still treating yourself.

Depends on the air pressure on the day, and how this reacts to the air pressure in the tyre.

Yeah obviously knowing you have light wheels on is probably worth at least as much as actually having them on. (How do I actually make it clear here that I’m not being sarcastic?)

I certainly wouldn’t say not to buy them.

I reckon I’d still feel better even if I’d just bought them and left them in the shed

If the acceleration/deceleration things was significant it’d have been calculated through measurements & extrapolation by mfrs – it hasn’t.

I calculated it. I forget the specific weights, but I calcualted that when accelerating out of a corner from slow corner speed on an XC race it was equivalent to something like 20-30W, when you might be doing 400W or so.

I would guess that the biggest effect would be that the slight extra bit of work on every tight corner, lap after lap, would add up to a bit less fatigue with lighter wheels and possibly a little more speed.

As said though, if you are quick on singletrack and on the downs, half a second gained by a small sprint on the way into a singletrack section could save you minutes overall as you aren’t held up.

However on a long endurance ride, you might actually be better off with heavier wheels as they are easier to keep going on technical bits due to increased momentum.

molgrips – Member

I calculated it. I forget the specific weights, but I calcualted that when accelerating out of a corner from slow corner speed on an XC race it was equivalent to something like 20-30W, when you might be doing 400W or so.

I’d love to see the calcs, I can’t see myself doing 400W out of any corner, and any acceleration might last a couple of seconds at most.

I suspect most xc riders will ride a lot more steadily as sprinting out of corners like that is going to be much more tiring.

I can’t see myself doing 400W out of any corner, and any acceleration might last a couple of seconds at most.

A casual honk on the pedals for a few seconds is easily 400W for me. And yes, it’s only for a couple of seconds – but it’s a small cumulative thing.

Genuine question – have you done much XC racing down south?

Is gravity different in England or something?

the weight at the wheels depends where in the wheels it is, at the hubs, its pretty much the same as if its on the frame. If its out by the tyres, it makes a difference. as a result, a 29er wheelset with the same weight as a 26er wheelset will be (marginally) slower accelerating/decelerrating, assuming the weight is distributed relatively the same

Is gravity different in England or something?

Yes, actually it is in the South, but that’s not what I meant. The geography is quite different which means the courses might end up being different. They tend to be very tight and twisty without long climbs. So powering out of corners is something that you end up doing a lot or you’ll lose loads of speed.

scotroutes – Member

Is gravity different in England or something?

Great Big Hitting, but my guess is the courses might be.

molgrips – Member
A casual honk on the pedals for a few seconds is easily 400W for me. And yes, it’s only for a couple of seconds – but it’s a small cumulative thing.

Genuine question – have you done much XC racing down south?

I still wonder how significant that’d be vs say 250-300W for 50% of the race (on flats and climbs).

Never raced doon sooth bar Kielder, done plenty in Scotland though. Again I’ve not seen many courses where I think this would be significant.

I still wonder how significant that’d be

Well of course it’s impossible to say for sure, but my crude calculations suggested it was, and of course we know that a bike with light wheels seems to surge forward much more easily than one with heavy wheels. This stands to reason and is clearly verifiable.

So maybe you feel like it’s easier to accelerate, so you don’t have to smash so hard to get it going again. And you definitely brake a lot on the windy courses which means that energy has to go back in.

At least I do.. cos I’m made in a sprinty smashy sort of way. Maybe that’s why I used to do much better on the descents and downs. I used to pull way ahead only to lose it all and more on the actual climbs.

So maybe it depends on your riding style as well?

the answer to all of this is 650b, surely?

I have a lovely 26″ race frame in the garage if anyone wants it. Under 5lbs in weight, the wheels are 1250g and the 2.1″ tyres are 450g 🙂