Obligatory link to fairwheelbikes' stem stifness review https://blog.fairwheelbikes.com/reviews-and-testing/stem-review/#:~:text=Overall%20the%20stiffness%20to%20weight,price%20tag%20that%20reflects%20it.
When you sprint you probably want to avoid spending energy on bending your bars and rather transfer it to your legs, a stiffer stem could possibly aid this, but has anyone studied the effect of stem stiffness and power output?
Sagan was famous for using a 140 mm Zipp Sl Sprint stem.
I currently run a 130 mm specialized multi comp set to -16 degrees with shims, wondering if something like the Vibe Pro di2 could be noticeably stiffer or would I be splitting hairs here..
Sagan uses it on his Robaix bike..
For reference not putting out mega numbers, 1700w tops, but aiming for 2000w..
Chafing??...........Oh sorry, I read the title as "Stiffer stem = more what sprinting?"
Are you racing? How long are you putting 1700w out for? If it’s any reasonable length of time turn pro and people will give you stems.
Just 1 second and at 85 kg so not great..
Maybe I should buy a zipp stem and do some testing then return it when it doesn't make a difference :p
1700w sprinting is top. Gaining 300w top end is probably impossible unless you are young?
I consider myself a bit of a sprinter, have won a 2/3/4 bunch sprint and I top out at about 1300w, probably less now, but thats a 1 second peak, 10 seconds best is probably more like 900w.
Anyway, I'm not sure that a flexy stem costs watts unless it is really flexy, watts come from your legs not your arms and there is probably more flex in the handlebars than the stem? If it flexes one way it cost energy, but potentially spring back the other way giving that lost energy back, helping with rhythm? I might be talking nonsense.
I've noticed carbon bars flexing under power, but never a stem.
Pro sprinters are probably using long stems to get aero, which will likely be much more important than flex?
1700w sprinting is top. Gaining 300w top end is probably impossible unless you are young?
I consider myself a bit of a sprinter, have won a 2/3/4 bunch sprint and I top out at about 1300w, probably less now, but thats a 1 second peak, 10 seconds best is probably more like 900w.
Anyway, I’m not sure that a flexy stem costs watts unless it is really flexy, watts come from your legs not your arms and there is probably more flex in the handlebars than the stem? If it flexes one way it cost energy, but potentially spring back the other way giving that lost energy back, helping with rhythm? I might be talking nonsense.
I’ve noticed carbon bars flexing under power, but never a stem.
Pro sprinters are probably using long stems to get aero, which will likely be much more important than flex?
Not so young anymore at 38, but I think I can get there with more leg strength work which I've neglected (squats etc) and high cadence drills, keep in mind that the number is with fresh legs.
1 minute power is 745W, goal is 1000 watts which may be a stretch..(harder than 2000w 1s!).
I run the prime primavera 40 cm carbon aero bars and yes there's some flex in those, maybe a stem won't make any difference as you flex the bars before the stem? Running a 130 mm one -16 degrees.
Stiffer stem = more watts sprinting?
Short answer is "no".
Long answer is, unless it's made from wet noodles, I doubt you would be able to measure any difference in speed.
I have a Syntace F99 stem in the garage, it's 100g and 105mm long. That's flexy.
1700 watts is a fair bit. Can't comment on the stem but the whole bike is likely to be flexing at power outputs like that. The peak power test on the Wattbike takes about 4 seconds, so I'm guessing that even if losses in the stem could be eliminated & made a difference it's not going to be for very long.
Why do sprinters use stems like the Zipp Sprint then? Tricked by the marketing dept? 😉
The number of watts lost will be negligible.
The stiffer stem is there to provide more confidence/direct handling.
I'm a < 1000W weakling in a sprint and even I noticed an improvement going from a quill stem to an aheadset.
More confidence = more watts?
they are paid to so people like you buy them?Why do sprinters use stems like the Zipp Sprint then?
A possible flip side is that a stiffer stem would lead to you being more fatigued due to vibration through your arms at the end of a race when you want to sprint.
Guessed the poster before opening thread....
I'm so far from any of the numbers being touted about that I have no direct feel for this type of 'flex' but I would have thought the bars would be the things you want to stiffen up way before the stem, as they are much bigger levers and you are yanking directly on them.
Has the road bike side of things taken on board the 35mm stem standard that some mountain bikes have? If so - probably worth upgrading bars & stem to these before worrying about variation between different brands that use 31.8mm.
Guessed the poster before opening thread…
Sorry but that doesn't make you Sherlock Holmes 😊
they are paid to so people like you buy them?
Sagan used the zipp sprint and covered the logo as he was not sponsored by zipp..
😂😂
I’m sure someone will have studied the affect of stem stiffness on watts lost, but whether anyone (mortal or pro) would actually be able to notice in real life is another question.
if you like the idea of buying a Gucci stem, it’ll probably make you feel better about your bike, which in turn will probably have a positive impact on your sprinting. Buy the stem you like but don’t feel the need to justify it to anyone else. I doubt most people driving Ferraris or riding £12k super-bikes are exploiting them to the best of their abilities.
Hang on, you're putting out 1700w but wanted to downgrade a 240 hub to a slightly fragile 370 because of the noise?
lower noise = more wattz
As a sprint weakling I can't comment on how flexy stems and bars might lose Watts...
But is that carbon bar a worthy treat for my Cube Attain GTC?
If you read the report on weightweenies you’ll see he mentions using a shorter stem as it’s stiffer. Talking exalite and Dario stems, but presume that’s consistent across the range. Sagan on a longer stem will likely be more about comfort and aero, saving watts in the 120 miles they’ve just ridden, rather than the last 300 metres.
I’ve noticed bars flex but never stems. I had the older model Bontrager xxx bars which had a bit of flex and a prime aero bar that was also very flexy.
But I’m only 67kgs racing weight and a huge sprint of 920 watts for 10 seconds. Never noticed it with old fashioned alloy bars and stem.
Not so young anymore at 38, but I think I can get there with more leg strength work which I’ve neglected (squats etc) and high cadence drills, keep in mind that the number is with fresh legs.
1 minute power is 745W, goal is 1000 watts which may be a stretch..(harder than 2000w 1s!).
Unless you are very undertrained or havent properly tested the existing numbers that you quote I'm afraid that you have no chance with either of your wattage ambitions.
Genetics is what is holding you back, not lack of squats. Not that your genetics are doing anything her other than stopping you from being in the top 0.1%.
What cat racer are you? What have your results been like so far?
What have your results been like so far?
He got a KOM on a bridge over a German river 🙂
Just get a proper chunky 35mm stem on there and a post with some serious layback 👍🏼
Unless you are very undertrained or havent properly tested the existing numbers that you quote I’m afraid that you have no chance with either of your wattage ambitions.
Am I undertrained? Yes.
Have I properly tested them? No, will do it this summer.
Results? A few sub 2 min KOMs against lazy Berliners. Would get smoked way before the sprint in any cat race probably, but working on improving my 20 min power..
I still think leg strength can get you a long way towards 2000w peak, just get big enough legs and it's easy! 1000W for 1 minute on the other hand is say 50% VO2 max so you need pretty great cardiovascular fitness.
I feel weak...
Also, since my bars flex i dont think the stem is the weak link here and a stiffer one wouldnt make much difference..so ive given up on this idea..for now..
Never noticed it with old fashioned alloy bars and stem.
I've found it very noticeable, especially with light ahead stems and old quill stems.
He got a KOM on a bridge over a German river
Thanks, I laughed out loud.
So you’ve not raced and yet you’re worried about your stem flexing and losing you watts?
35mm stem on a steel LLS hardtail
90mm stem on a Ali LLS gravel bike.
No noticeable difference.
JUST RIDE 😁
So you’ve not raced and yet you’re worried about your stem flexing and losing you watts?
Who says Strava is not a race??
Who says Strava is not a race??
Posted 7 minutes ago
Anyone who has ever raced.
Not everyone's a dentists who likes to play bumper carts.
Those are certainly words...
And yet so many people race without injury!
Who says Strava is not a race??
I would imagine Strava themselves would say Strava is not a race. Zwift or something similar would be closer to a race I imagine but guessing there won't be many 30 second races on there.
Have you tried cycle speedway?
Shhhh don't tell him about zwift.
Be claiming he weighs 45kg next.
The answer is NO.
Take your stem off and stick it in a vice, then try bending it.
Take your stem off and stick it in a vice, then try bending it
Depends on the stem. As above, I had a very visibly flexy stem on my bike for ages. 2-3cm of flex on the ends of the bars when I twisted them, and it was visibly the stem. It didn't break though.
Just buy it and report back when you score all those bridge crossing KOMs...
Take your stem off and stick it in a vice, then try bending it
I still ride a bike with a quill stem and I can visibly see it flex when pulling on the bars (I am probably putting out 3000W from my arms though)
Realise we are not really talking about quill stems but they flex and it makes no difference to my speed as my legs are providing that.
I had a very visibly flexy stem on my bike for ages. 2-3cm of flex on the ends of the bars when I twisted them, and it was visibly the stem. It didn’t break though.
molgrips
Depends on the stem. As above, I had a very visibly flexy stem on my bike for ages. 2-3cm of flex on the ends of the bars when I twisted them, and it was visibly the stem. It didn’t break though.
2-3cm of movement at the end of the bars, caused solely by flex in the stem!?
How wide were the bars? And how stiff were they?! I would expect the force required to flex a stem that much would also cause noticeable bending in the bar.
No way I would be riding that!
Are you sure you don't mean 2-3mm?
......makes mental note to try & bend bar/stem combo as much as possible when next in the garage!
And yet so many people race without injury!
Yes so few crashes in Cat 5..
BTW Strava is not a race, it's a competition, unless you're cheating and getting KOMs in a race :p
I thought Strava was a training aid/way to track rides?
I thought Strava was a training aid/way to track rides?
2-3cm of movement at the end of the bars, caused solely by flex in the stem!?
How wide were the bars? And how stiff were they?! I would expect the force required to flex a stem that much would also cause noticeable bending in the bar.
The stem was a Syntace F99 105mm and the bars were Easton Monkeylite SL carbon low-risers I think 620mm. The bars might've flexed a bit but you could see the stem twisting. It was a bit unsettling when I discovered it, but it wasn't obvious straight away as one generally has both hands on the bars during high load. Rode the bike for years without issue, and I'm not light. It didn't bend up and down, it just twisted. It was very much a 'holy shit' moment when I discovered it.
Yes so few crashes in Cat 5..
BTW Strava is not a race, it’s a competition, unless you’re cheating and getting KOMs in a race :p
Not sure what cat 5 is, but I’ve raced cat 3 & 4 for about 5 years and never crashed. I also didn’t win either, maybe more crashing = more wins.
Whatever tickles your pickle regarding the OP but I’d focus on other things way before I start worrying about stem flex..
Mate if you need to measure the size of your penis I think a ruler is cheaper and more accurate?
What have your results been like so far?
He got a KOM on a bridge over a German river 🙂
Shut the Front Door, surely not THE bridge over THAT river? Man, if only they all knew!!!!
Surely if you’re bending stems, there’s going to be more squish in your tyres, long before the stem bends?
Whatever tickles your pickle regarding the OP but I’d focus on other things way before I start worrying about stem flex..
Think we got to the conclusion that unless you have flex-free bars stem flex is likely not going to be a factor and even if you do have nobody has measured the effect on peak wattz - modern stems are for most part pretty non-flexy.
Shut the Front Door, surely not THE bridge over THAT river? Man, if only they all knew!!!!
It's the spree, very famous river around these parts :p
if you do have nobody has measured the effect on peak wattz –
That'll be because the number of people who care about their 1s power is infitesimally small
If you want to feel stem flex go and try an old 1" steerer solid aluminium quill stem - feels downright scary back to back with a modern bike!
I'd also be asking how accurate is the actual power measurement over 1 second?There is an angular velocity and averaging in that calculation and you are also accelerating.
I regularly get significantly different strava times on the same ride when I test 2 devices at the same time. I think a change of stem is the least of your issues if completing strava is the aim.
I regularly get significantly different strava times on the same ride when I test 2 devices at the same time.
And that is even more apparent when dealing with 30 second segments which are dodgy enough to start with.
I think BMX racing would be the ideal sport in this case as the power really is the first few seconds then once in the lead just keep it. May have to like crashing even more than in a road race though.
the only watts lost due to stem bending would have to be disappated through heat. Even if it is flexing (which I doubt) - if its not getting warm (which it isn't) then its a non-issue - any power not going to the wheels through flex is just being returned when the rider switches pulling to pushing on that side of the bar. there's no damping circuits in play and metal as a spring is a remakably efficient thing
