Kevinative

ok so I have a slight dilemma on my hands. my first TT is tomorrow, and I'm starting to think I should ride the old steel frame vs the CR1. Reason being, perhaps the steel frame is "faster" due to BB stiffness and it's much more narrow (lower drag), and although much heavier that won't matter once it gets up to speed. Another consideration; the course is flat. The CR1 is almost 10lbs lighter, but I swear the BB is noodly compared to that old steel bike, and when I get the steel bike up above 25 it feels easier to maintain that speed. Another thing, I've had both on the trainer, and the BB lateral flex is almost disconcertingly noticeable on the carbon, yet barely perceptible on the 12 y.o. steel frame.

Phantoj

CR1 is low-end?

Anyway, try the steel this time and CR1 next time and see how you like it...?

PS - I would go CR1 all the way because 10 pounds is a lot.

ericm979

BB stiffness has essentially zero effect on road speed.

But if you're happier on one bike, ride that one.

I'd personally pick the bike that put me in the best aerodynamic position, as rider air resistance is the most important factor in speed on level ground.

Kevinative

guessing it is based on price. are all CR1's created equally? I have the Team. when I almost went with a Tarmac, I found that the grade of carbon changes along with the components as you go up in price. I wish the bike manufacturers would make this more public knowledge, give the frame a flex factor, lateral and vertical..., digressing. yeah the weight is huge, but I'd put the lighter wheels on the steel frame. I'll probably go with the CR1, but it does seem to flex more.

Kevinative

that's one beef I have with the CR1. don't get me wrong, I love that bike, but I wish the top tube was longer and the head tube shorter along the lines of the addict. unfortunately the addict wasn't on sale at the time. the steel bike (Diamond Bike Interval circa 2000 w/ upgraded components) gives me a longer reach. it's a Cat 5 Merckx so it'll be a good time either way.

gregf83 

No BB should be flexing much when you are TTing at approx 300W. If it flexes noticeably at 300W what happens at 1000+? Maybe you've got a problem with your bike?

Kevinative

I had an alu bike on the trainer and it flexed a decent amount as well, if not more than the carbon. it's not the bike. anything above 300 watts shows flex, don't really look down at 1000 watts. as far as an actual TT, or riding on the road, DO NOT SEE any flex. perhaps it's more of a trainer issue, but like I said the steel barely moves laterally above 300 watts.

Nerull

Bikes flex way more on trainers, because the bike is stuck in place and cannot move as your weight shifts side to side. On the road, the bike can move, so that flex mostly goes away. If pro sprinters can't cause much flex, neither can you. Steel is also not particularly known for it's stiffness - the flex of steel is what gives it a 'softer' ride and why many people prefer it to aluminum, which IS stiff and transfers every vibration into you.

Kevinative

yeah I know that's the general idea. but you can make a flimsy alu frame and a stiff steel frame. from what I read wall thickness and diameter of tubing are more important. alu is weaker, so to make stiffer they up the diameter. not necessary with steel bc it is more resilient, can flex without breaking moreso than alu, hence the stiffer feel as tubing diameter goes up. also explains the fat tubing on my CR1. comparing the 3 bikes on the trainer, FWIW, the steel rig has much LESS lateral flex at higher wattages. it stands to reason bc there is a lot more material down there.

Bacciagalupe

I think you can continue to ignore the "steel is flexy" garbage. AFAIK Merckx frames are made for high-end racing, so it'll be plenty stiff.

Also, on a flat course with little acceleration, the extra weight shouldn't make a difference.

However, as far as I know BB flex isn't going to genuinely increase the amount of power that makes it to the drivetrain. I may be wrong but IMO BB flex is much more about ride feel than actual pedaling efficiency.

AFAIK almost all of the CR1's use the exact same frame; only the most expensive CR1 has a slightly different type of carbon. It's one of the pluses about Scotts, if you like to upgrade your bikes.

Unfortunately I don't think there is a viable way to figure out which bike is genuinely more efficient than the other without a power meter. I expect though that if they have the same setup and same tires, they'll ride at the same speed on a flat TT course.

Phantoj

yah, that CR1 is a veritable noodle.

jr59

You guys make me laugh. Most on here can't believe a older steel bike could be better than a CF.

Ride what ever you fell you would be faster on. Don't get hung up on anything but speed.

Get aero and pedal harder and faster. The stop watch won't care what frame you are on.

zzzwillzzz

velonews did a test of a bunch of carbon frames where they measured deflection at the bb when loaded, they also threw in a relatively modern 853 steel frame for comparison. the carbon bikes were all stiff (i forgot the range) but the steel frame was about 4x more deflection than the carbon ones.

carpediemracing 

853 is one of the more flexible tubesets out there. I had a similar frameset (Tange Prestige) - after the first few sprints on the bike, I stopped to see if the BB was cracked (and I really thought it was).

The old Schwinn Continental came with a solid steel fork that was super aero. Apparently, in the old days, some riders use that fork in lieu of a lighter one, due to its aeroness. I think it'd be illegal now in the UCI, it's really thin in profile.

Since your body is the biggest aero factor, get on the bike that allows you to hold a good position. I'd use the lighter bike personally - the inertia thing is more effective in the wheels.

spock

Could it be possible that a bit of flex in the pedal stroke is actually better for the knees?

I see it as kind of like a little cushion for any irregularities that a pedal stroke might have. It kind of works with your body in a way that let's it be more natural.

Phantoj

What about ten-year-old Sora-grade Diamondback frames? The OP doesn't have a Merckx...

slipstream8

I think if the OP "feels" like the steel bike is stiffer, it may give him a slight psychological advantage to ride the steel bike, whether it is any stiffer or not. That in itself can be a significant advantage in a race. However, I don't think how a bike moves on a trainer is that relevant to stiffness while riding on the road.

I have a custom Reynolds 853 bike, and I was shocked at how much stiffer a new Cervelo RS was by comparison. Starting out from a stop is a whole new world on the Cervelo.

mazdaspeed

I think the BB flex contributes to the 'lively' feel everyone praises steel frames for. A good steel frame does feel springy, if you will. Carbon has pretty good elastic properties as well but due to frame makers being able to put the material wherever they want, most are going to be stiffer in the BB than pretty much any steel frame.

As far as what bike to use, I agree with others that your position on the bike will make the most difference, and that in any kind of race I'd opt for the lighter bike when possible.

Bacciagalupe

doh

Still, the point stands that BB stiffness is basically about ride feel rather than actual wattage hitting the drivetrain; that if the old steel frame was made for racing, it'll be fine for a TT today (assuming position is correct etc); and that weight won't make a big difference on a flat TT.

mmmdonuts

4x of what? .1", .01", .001"? Do you see how 4x can quickly become insignificant?

zzzwillzzz

i don't remember but yes, i see your point, would be a lot easier if i can find the article.

Kevinative

thanks to all for the great insights and recommendations. I think a video would be interesting to view comparing the 3 frames on the trainer. maybe throw a ruler under the BB. I was really surprised to see the CF frame flexing a lot more than the older, low grade steel. that's one reason I don't use the CF on the trainer anymore even though I know I'm being ultra-conservative. moreover, some would be surprised to see how much the (supposedly stiff) alu frame flexed (it was a redline made with 6061).

based on the general consensus about BB flex being more of a trainer-ism and very negligible as far as transferring watts to the road, I stayed with the CF. so how did it go? well, made the stupid rookie move of riding 30mph in the first minute or so, feeling great, but once the adrenaline wore off just tried to get my legs back. the passing of a storm and 20-30 knot winds made for a challenging day, clocked a 22:35 on an 8 mile out and back in the Merckx cat 5.

Beaker

Unless you have your front drop outs attached to a fixed object, I've always assumed that some motion probably comes from the slight pitch of the bike caused by deformation of the front tire in the riser block as well. As others have said, I don't really pay much attention to the BB flex issue - I've noticed it on my CAAD10 as much as my Spec'd Roubaix and am by no means a monster in the wattage department.

brians647

Smoother? Maybe. But not enough flex to benefit your knees.

Kevinative

rerode the TT today after a few days off the bike and a 20 mile warm up, was faster by 65 seconds (8 miles in 21:30). didn't think about it initially but the CR1 is designed to flex vertically in rear triangle and fork to give smoother ride, so on a trainer with stationary front wheel guess that caused the lateral frame flex. BB itself probably wasn't flexing at all.