Stiffer Wheel? or More PSI Tire?

Discussion in 'Cycling Equipment' started by Danv1317, May 7, 2009.

  1. Danv1317

    Danv1317 New Member

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    I am a heavier rider at about 210lbs. I have dura ace wheelset. When i go into corners fast downhill or in a fast paceline around a sharp corner, it feels like the tire only has 70PSI in it and it's sliding out from underneith me. I am indeed running about 115-118psi in my Pro Race 3 tires. Is this a problem with my wheel not being stiff enough or do i need a tire that i can run higher PSI?
    Thanks
    Dan
     
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  2. parawolf

    parawolf New Member

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    So, you are a heavier rider, with a weight weenie-low spoke count wheelset and the front wheel is laced radially. (assuming these are the C24 wheels?)

    Depending on what you consider fast, and your weight balance fore/aft when cornering. This impacts the cornering on the front/rear wheels.

    I woudln't have recommended the DA wheelsets. I'd be recommending something like a DT Swiss R1.2 with 32 spokes 3 cross front and rear, using DT competition spokes and brass nipples to dura-ace hubs.

    Drastically different to what you are on today, and you'll feel the difference in your ride.

    Wheel stiffness test : http://www.rouesartisanales.com/article-23159755.html

    you've picked some of the least stiff wheels going around
     
  3. spinner32

    spinner32 New Member

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    Any idea as to where ROL wheelsets (D'Huez and Race SL) might come in? I'm looking to potentially buy a set due to overwhelming positive feedback on performance and support from the builder.

    Also - I was a little perplexed to see the Mavic Aksium Race in one of the top slots for the front wheel lateral stiffness - I guess they truly could be bomb-proof. :eek:
     
  4. parawolf

    parawolf New Member

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    Mavic Aksium Race:

    heavy rim
    fat spokes

    Means = stiff and strong wheel
    Means = not light
    Means = not aero

    Make a great training wheel, not so good for high performance.
     
  5. Danv1317

    Danv1317 New Member

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    I have the dura ace WH-7801 wheelset. it was the set that came on my Specialized Allez pro. i live in PA, so there are some big hills where we are cornering at 40+mph but also alot in the high 20's and low 30's.

    I really only feel the flex in my rear wheel, not in the front. Should i get just a new rear wheel? Or would it make a big difference to just get a new wheelset? I need something that can perform, not just something for training. What kind of factory set do you reccomend? I have about 700-1200$ to spend. I appreciate the help.
    Thanks
    Dan
     
  6. 531Aussie

    531Aussie Well-Known Member

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    This ain't the optimum 'test', but it'll give you some idea: put the wheels on a bike and wobble them from side to side with your hand, then do the same to some 32-spoke wheels for comparison. The differences are sometimes staggering.

    Here's another, similar one: squeeze two spokes together, pretty firmly, and see how far the rim deforms.

    Flexy wheels are horrible. I dunno how some people can stomp out of the saddle of some wheels.

    A friend of a friend really wanted to buy some of the shallow Dura-Ace wheels, but the guy at the shop (Bike Pro, Surrey Hills) told him he was too heavy for them, and wouldn't sell them to him. He convinced him to get some more sturdy Fulcrums
     
  7. Danv1317

    Danv1317 New Member

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    Possibly a DT Swiss 1850 or a Campy Eurus?
     
  8. alienator

    alienator Well-Known Member

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    IF a flexy wheel is your problem, then in cornering, especially fast cornering, the effect of wheel flex is only a real factor in corner entry and corner exit. I think with a rear wheel, you'd most likely see the effect powering out of a corner. During corner entry, under braking, the rear wheel is unloading a bit. Mid corner, flexibility is a non-issue as the wheels are in a dynamic quasi-equilibrium.

    Riding flats, climbing, or sprinting wheel flex isn't really the issue that it's made out to be. From a performance point of view, energy losses due to wheel flex are negligible. Moreover, it's questionable whether riders can actually feel wheel flex or not. Mavic did a study and found that riders could NOT reliably determine whether a wheel they were riding was a noodle or was stiff enough to withstand a winter siege in Stalingrad.

    Alas, as humans we do what feels good, and iffin' it don't feel good we get doubts. It doesn't matter whether the doubts are from real or imagined phenomena.

    Before you make the leap and buy new wheels, you should try some simple things first. Try a 25 on the rear instead of a 23. Try a range of air pressures, both lower and higher. Have the wheel checked for trueness and spoke tensions. When spoke tensions have gone all pear shaped, that's never good juju for a wheel.

    If none of that changes things, then maybe it's time to doll out some pesos for new wheels, but iffin' you want new wheels, I'd bypass boutique wheels and go straight for the custom built wheels. For half the price of boutique you can get customs that out perform, in every way, the boutique kit.
     
  9. Peter@vecchios

    [email protected] New Member

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    Nothing from a 'factory'. Do you have a good wheelbuilder in your area that can design and build a wheelset specifically for you or your needs? Like a shimano, Campagnolo(with HG freehub) or DT hub, rims by DT, Velocity or Mavic, DT or Sapim spokes, designed for you? Probably way less than $1200.
     
  10. dhk2

    dhk2 Active Member

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    +1. As you spell out, since bikes lean over in turns, the wheels see very little lateral loading.....unlike car wheels. Even when putting in steering input to lean the bike over quickly, seems to me the "steering" flex in the fork far exceeds that of the wheel. (To illustrate this, just trap the front wheel with your legs, "steer" the handlebars and feel the flex in the forks).

    In addition to tire pressures, believe the construction of the tire itself plays a role. The current tire I'm using, the Open Corsa CX, also makes the back end of the bike feel "loose" (to use a NASCAR term :) on windy high speed descents, as if the tire is underinflated. It's not dangerous, but was a bit unnerving when I first started riding these last season. Perhaps a wider and heavier "training" tire will solve the problem.
     
  11. Feltski

    Feltski New Member

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    I just picked up a set of Aksiums today. at 220lb, Ill let you know how they hold up after some mileage
     
  12. parawolf

    parawolf New Member

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    There is one thing that will help you stop the wheel squirming when putting high forces through it....

    lose weight.
     
  13. alfeng

    alfeng Well-Known Member

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    There's some good advice here ...

    BUT, this has to be at least the third time you've cited the MAVIC "study" (BTW. MAVIC is an acronym) as if it were gospel ...

    I read Zinn's synopsis of MAVIC's study on VelonNews.com when he first reported the "study" but I have never seen the actual data ... was it published anywhere?

    Have YOU seen the actual data from MAVIC's tests?!?

    I suspect that as far as anyone knows, the difference in tension may have been minimal when one considers the actual range of possibility -- e.g., Shimano WH-7700 vs. almost any other "factory" wheel OR a regular, "benchmark" 32x3 wheel ...

    Which wheels were used in the test?

    AND, that begs the question -- did Shimano abandon the paired spoke design because they chose not to pay the licensing fee to ROLF or was it something else?

    Is the WH-7800 laterally stiffer than the WH-7700?

    Did the four extra spokes make the WH-7800 wheel laterally stiffer or only comparable to the paired spoke design of the WH-7700?

    Santana had/(still has!) their version of the WH-7700 which is spec'd with a larger (13?) gauge spoke ... unsold inventory remains, AFAIK ... it would probably be a great wheel for a single rider after adjusting the O.L.D. to 130mm.

    Regardless, just because someone is a "professional rider" does not mean that s/he is able to ascertain meaningful differences in many aspects of the components on the bikes they ride -- did the MAVIC test(s) actually measure how long it took to cover fixed distances (flats, climbs, desecents) in addition to the rider's subjective feedback?

    How many riders were used & how many repititions of the test were run?

    What was the sequence of comparison? Soft-firm? Firm-soft? Soft-firm-soft? Firm-soft-Firm?

    I suppose that if YOU/(are there any others?) repeatedly verbalize the so-called conclusion of the MAVIC test that a rider cannot tell the difference between wheelsets often enough then it could eventually have the same imprimatur amongst the naive as "the myth of K.O.P.S" (in the words of Keith Bontrager) and/or the use of double butted spokes and/or how Man's use of SUVs has caused "global warming" on the moons of Jupiter, etc.

    BTW. A cynical person might be able to infer from MAVIC's test that they were actually trying to see how lax their quality control could be -- that is, how frequently (if ever) they had to calibrate their gauges ...

    Regardless, people should buy-and-use what they want, but caveat emptor ...

    Heck, if someone thinks that a wheel's lateral stiffness doesn't matter & s/he wants to buy a pair of 16-spoke wheels, I've got a pair I can sell!
     
  14. garage sale GT

    garage sale GT New Member

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    Is it possible you have a bit much psi? Is it possible a slightly larger tire with a bit less pressure would allow a larger contact patch and feel more secure as well as being less likely to get bumped off the road? My experience in comparing 23s to 28s is very limited but as a 220 lb rider myself, I greatly prefer a slightly bigger tire.
     
  15. SUPER RIDER

    SUPER RIDER New Member

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    Experiment! I am a 220Ib rider, non-racer who likes to experiment on my rides. Just yesterday, I rode a Continental 700x25 GP4000 in the rear and a 700x23 Vittoria Evo Open Corsa in the front. The ride was excellent comfortable-wise, but a tad slow.

    I am always mixing up my tires and looking for the ultimate ride. I fully expect not to find it, but the reward is in the "Search" says Zen.

    Good luck.
     
  16. 531Aussie

    531Aussie Well-Known Member

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    I can defintely tell the difference between my flexy carbon crap and my 30mm-deep, 32-spoke wheels.

    [​IMG]

    The differences between my FP60s and my DT RR 1.2s is night and day
     
  17. alienator

    alienator Well-Known Member

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    I can tell zero difference between my 50mm CF rims and my 25mm niobium rims, but then that's why we have science: 'cuz long ago people figured out that human perception is far from accurate. There's a lot going on between someone's ass and the contact patch, so a person would be very hard pressed to say with any semblance of accuracy or seriousness what the cause of what they felt was.

    Here are a couple of tales to show just how stupendously wrong the human sensor can be:
    1. Scott Russell, AMA Superbike Champ, 5 time Daytona 200 winner, WSBK champ, ex Grand Prix rider (from the 500cc two stroke days). One year at Daytona, Scott was having difficulty getting up to speed, and he swore it was because his rear shock spring wasn't working as well as everyone else's. So, he told his chief Mechanic, Rob Muzzy, that he wanted the same colored spring as all those going faster than him. Muzzy obliged Russell, but not as you think: he painted Russell's rear spring the same color as that which the faster guys were using. Result? Russell went to the top of the charts. For those playing at home, does anyone want to guess how much more a rear shock spring on a superbike moves compared to the lateral movement of a bike rim?
    2. Fighter pilots, the world over, are the best of the best when it comes to flying planes. It's not a rare thing for a pilot, flying in clouds, to emerge from clouds flying upside down, even though their asses told them they were flying right side up. More than one pilot in such conditions has flown straight into the ground, thinking he was pulling up.
    In fact, it's a doddle to confound our senses, be they touch, sight, balance, or proprioception.

    How many times have we seen someone write about how "stiff" their Ksyriums are? Uhm, it's funny how they don't really end up being stiff when such things are actually quantified. So, then what do we do? Do we only pay heed to the "senses or feelings" of special riders? Maybe pros? Heck, we can't do that 'cuz there are pros who say they can't tell a difference between tubies and clinchers, and as everyone in the internet tubes will say, there's a difference between tubies and clinchers. Ain't it obvious? Maybe we should only trust the words of those that are sensorily adept enough to feel the flex in bottom brackets, axles, and bearings. Maybe we should only believe those that are sage enough and skilled enough to sense when wheels are actually making a bike accelerate like a rocketship or climb like a meth fueled mountain goat.

    Or......maybe we should just remember that what we sense is not necessarily related to some physical reality that we think we've discerned. Everyone forgets that little bit and then makes the leaping assumption that what they feel must be universal or a quantitative truth. By all means, everyone should ride what makes them feel right. After all, it was Confucius who said, "If it feels good, do it," but Confucius was smart enough to know that just because he thought riding fat girls felt great didn't mean that everyone else did. That's a true story.
     
  18. alienator

    alienator Well-Known Member

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    Iffin' I were you, I'd be using 25's front and back, prolly in the range of 110-115 psi or so. At what pressures did you run your "experiment?"
     
  19. Peter@vecchios

    [email protected] New Member

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    Teeny point but as a retired USN 'Fighter Pilot', in the age of jets, when they were made as jets, not just prop planes with a jet engine and poor avionics, it is actually pretty rare to get vertigo that bad. You are trained from day one, learning to fly in the clag, to trust you instruments. The 'modern' instruments, at least in the F-4, A-4, F-16N(USN adversary type) and F-14 the avionics were very good, reliable and altho uncomfortable sometimes, you came otta the clouds right side up. Now in the earlier WWI and WWII prop days, when all ya had was a turn and bank needle and ball, it happened quite often.
     
  20. 531Aussie

    531Aussie Well-Known Member

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    I was sayin to the other Aussies that cycling could do with a version of Top Gear, and it just dawned on me that you could host it

    [​IMG]
     
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