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Sheldon Brown on frame stiffness and ride quality(28 posts)

Sheldon Brown on frame stiffness and ride qualitygtx
Apr 9, 2002 1:38 PM
good stuff
Seems to boil down to. . .czardonic
Apr 9, 2002 3:18 PM
"Virtually all . . . "differences" are either the imaginary result of the placebo effect, or are caused by something other than the frame material choice."

Interesting indeed.
I agree with Sheldon on this oneNessism
Apr 9, 2002 4:47 PM
In my experience ride quality is determined by 1st- tires, 2nd- fork, and distance 3rd- frame vertical stiffness. I'm not saying that the frame has no effect, it does. But the effect is quite small compared to the fork and tires.

Apr 9, 2002 4:56 PM
I fully agree. Out of 4 bikes, 1 carbon, 2 steel, 1 alum, and just sold the titanium and when I put the same wheels on they pretty much ride alike. Finding nice riding tires for long distances is a problem though. Did you ever read the reviews on tires? No one is satisfied. They are either soft and grippy with flats or hard and tough.
on what do you not agree with sheldon brownishmael
Apr 9, 2002 7:59 PM
the man seems to be an authority on everything from the latest to the classic....
So which is better, Fe, Al, Ti, or CF???Kerry
Apr 9, 2002 4:42 PM
This point has been made so many times in this forum, and yet I will predict with 100% probability that within two weeks, there will be a steel is real, Al is harsh, Ti is flexy, CF is dead thread. And which one should I get for my new bike? Tell me! PLEASE??!!
I agree about how chain stay length contributes to road shock...Tig
Apr 9, 2002 6:03 PM
...felt at the rump. Material isn't as important as chain stay length, but it can contribute slightly. The main reason my Merckx Fuga feels so smooth in the back is the longish chain stays, and the CF seat stays help mute the higher frequency vibes while keeping the rear triangle stiff.
Merckx frame geometeryNessism
Apr 9, 2002 7:03 PM
Don't forget that Merckx frames have a lot of bottom bracket drop and that results in the "effective chainstay" length being shortened some.

I can imagine that chainstay length can have an effect but I think it's a small one. Again, nothing like the effect changing tires, such as going from 20's to 23's, or of going from a stiff fork to a soft one.
Merckx frame geometerygtx
Apr 9, 2002 7:49 PM
to be honest, I don't even understand the whole fork thing. All my bikes have very sturdy steel forks and they all seem plenty comfy to me. I figure anyone who needs a "comfy" fork is putting too much weight on the bars, most likely as a result of improper fit. Regarding Merckx, the c-stay length, effective or otherwise, is still a bit longer than the norm.
ssddle tiltcolker
Apr 10, 2002 4:05 AM
i see a lot of saddles tilt, nose down. i ride mine with nose slightly upwards. it takes weight from the bars and places the center of gravity in my abs. the abs support the body, more than butt and hands. the bike kind of rides under me.
Apr 10, 2002 5:11 AM
I often think that riders who struggle to find comfortable saddles are putting too little weight on the bars.

I also prefer steel forks as they feel to me like they do a better job holding the front wheel on the pavement which helps give me a stable platform on which to spin. Road shock is less of an issue for me, but comfort is a matter of perception and thus a very individual thing.
Apr 10, 2002 7:48 AM
In 17 years of riding I have yet to meet one vaguely serious cyclist who has had a hard time finding a comfortable seat. People definitely have general preferences and favorite models, but I think the people who have trouble finding a comfy seat just don't ride that much. Also, when they do ride, I think they spend a lot of time coasting--for coasting, a big old gel seat will be more comfy than a hard narrow seat--but the opposite is true for pedaling. When you ride a lot--especially when you are riding hard--I think most of the weight is going into the pedals. Also, a lot of saddle comfort has to do with finding the right fore-aft position, and the right angle. When I set up a new bike, it usually takes me a few days to get this just right. But yes, this is all very individual.
I agree and also.Sintesi
Apr 10, 2002 8:06 AM
Part of the fit and comfort process is patience. Everyone has a sore butt until it toughens up by riding extensively. Arms and shoulders ache? Maybe you just need stronger muscles. You sometimes need to give it time to let your body adjust and the muscles to adapt and that only comes from riding constantly.
this may be truecyclopathic
Apr 10, 2002 8:39 AM
for 2-4hr rides, if you start getting into 10-20-30hr or more rides there's only as much body can take. There're numerous stories of RAAM racers riding with gallon water jars tight up to helmet at the back to counterweight neck muscle failure.
I resemble thaqt remark!Len J
Apr 10, 2002 4:06 PM
I may be the exception to your rule. I ride between 100 & 125 miles/week all winter & between 125 & 175 miles/week all summer& I ride hard. And I have yet to find a non-torturing saddle. I been professionally fit, Have great fore/aft balance & have been riding off & on for 25 years and still have never found a saddle that feels good beyond 50 miles.

I have given saddles a minimum of 500 miles and have ridden my current one for over 2000 miles, but I still know it's there at all times.

So I can't agree with your generalizations. They don't conform with my personal experience. Of course I guess by your definition I must not be a: "vaguely serious cyclist" since I have "had a hard time finding a comfortable seat" I guess I must coast more than I think, (Tongue firmly in cheek). And as to you comment "When you ride a lot--especially when you are riding hard--I think most of the weight is going into the pedals. " Well I'll let the logic of that one sit on its own.

Apr 10, 2002 6:50 PM
well, I haven't met you. ;) Seriously, that sucks. Tried a Brooks?
No Problem.Len J
Apr 11, 2002 3:47 AM
Sorry for the rant, you just hit my generalization button! :-).

I have, maybe the weirdest body in the world, nothing ever fits. Since clothes (& saddles) are built to average sizes, anyone who has about average sizing is OK, those of us who are on the extremes are SOL. Shoes are a great example. I have the length of a size 10 (Right foot) or size 9 1/2 (Left foot, unfortunatly I have the width of about a size 6. The only thing I've found that fits is SIDI narrow with custom footbed. It's never off the rack for anything for me. Unfortunatly, I think the same is true of saddles.

As to the Brooks, benn there, done that, hated it.

wtb podiumishmael
Apr 10, 2002 7:17 PM
ive gone through about 9 saddles myself and this one is a definate keeper, and very light too
Fork sifffnessNessism
Apr 10, 2002 6:06 AM
You might be right about many people putting too much weight on the bars. I've noticed that my position on the bike chances quite a bit depending on what kind of shape I'm in. In spring, I tend to carry more weight forward and the top tube on my frame seems long. By summer, I'm much better ballanced on the bike with my body trunk supporting my weight better and I desire a frame with a longer top tube.

All that aside, I have noticed significant differences in fork stiffness from one model to the next. In particular, the Kestral EMS fork is much stiffer than the Time Equipe model - I was surprised by the difference. Also, I have used steel forks that were noodles and others that were super stiff - even more so than the Kestral.

For those people that are carrying too much weight with their arms, the fork stiffness is accentuated. And I include myself in that "carrying too much weight" catagory - at least in the spring time.

Fork sifffnessgtx
Apr 10, 2002 7:41 AM
I think there are definite differences between how different forks track through corners or behave under braking, but do you really think there is that much difference in the amount of shock coming up through the bars--say, more than the difference between Benotto and Cinelli tape?

Totally agree about change of position depending on what kind of shape you're in--when I'm out of shape my stem always feels half a cm too long, when I'm in shape it often feels half a cm too short. I also like to fiddle with bar height--but only move it up and down about 1mm.
Fork sifffnessNessism
Apr 10, 2002 9:10 AM
I most definately DO think that fork stiffness has an effect in the amount of shock comming through the bars. A few years back I installed a Kestral EMS fork on my Merckx EX Ti frame only to be surprised by the amount of shock comming through the bars. My STI levers rattled quite a bit over bumps which was very annoying. Changing to a Time Equipe fork was like night and day- the ride was much smoother and the levers stopped rattling. The downside was that the Time fork felt a little spongy when cornering hard such as in a crit.

Check out the following link and look at the drastic differences in fork stiffness. This chart jives well with my personel experience so at least I'm a believer.

Fork sifffnessgtx
Apr 10, 2002 10:45 AM
cool info.

Ok, speaking specifically of Merckx (I have one, too--a 653 Century with matching steel fork)--did the Time and Kestrel forks have the same rake? I think perhaps a stock Merckx fork has a funky rake--I think Merckx uses his "proprietary" headtube angle and fork rake to achieve low trail. I've heard of people thinking stock Merckx forks are flexy, but could this be because of the small amount of trail with the stock Merckx setup? Could this "flexyness" really be more of a handling issue? Could swapping to a different fork with a different rake create more trail and thus be perceived as a difference in stiffness up front?

The Merckx approach to trail is mentioned here:
Merckx geometeryNessism
Apr 10, 2002 11:30 AM
The Merckx EX Ti is a Litespeed built frame that does not come with a fork. My first fork on the frame was the hard riding Kestral followed by the soft Time. This comparison of two forks on the same frame made it clear to me that not all forks are created equal. BTW- both forks had the same 4.5 cm of offset.

Early Merckx frames all used steel forks with 5.2 cm of offset. This is a lot of offset by modern standards - Richard Sach frames also use 5+ cm of offset in case you find this interesting. The head angles used by Merckx are quite unremarkable dispite the secret "proprietary" label. My EX had a 73.5 degree head angle. The bottom line is that Merckx bikes have quick steering due to this low trail.
One characteristic of using a fork with 5.2 cm of rake though is that they ride quiet comfortable. The large amount of rake is most likely why people say Merckx forks are flexy. The trail has nothing to do with it.
good info--more questionsgtx
Apr 10, 2002 11:46 AM
I'd been trying and failing to get more info on Merckx geometry. I realize the the LS built Merckx frames didn't come with a fork, which I always thought odd, given what I take to be Merckx's views on these sorts of things. What size is your frame? Did you measure the HTA yourself or is it published somewhere? Trying to figure out what it is on my frame--which is either a 57 or 58 (measures 57.5 c-c and has a 57.3 so I suspect it may be a "58"). Also, do you know what the bb drop is on his bikes? And that's interesting about Sachs, too. Thanks!

Oh, one more question--I didn't really understand this on the Spectrum site. My Merckx has quick steering at lower speeds but rock solid at higher speeds, and corners like a champ. This seems to go against what is said on the Spectrum site--sounds more like the way they describe high trail framesets. My other (custom) frame feel much more neutral everywhere.
good info--more questionsNessism
Apr 10, 2002 12:28 PM
To determine head angle I measured the frame myself. I'm not sure if the Ti Merckx frames had the same geometery as the steel ones though. I do seem to remember though that the specs were published somewhere - maybe an old Colorado Cyclist catalog?
Merckx 54 cm c-c, 54.8 cm top tube, 73.5 degree head angle, 73.3 degree seat angle, 41.5 cm chainstay length, 7.2 cm of bottom bracket drop.

Measuring drop is not too hard if you can get a fix on the centerline of the hub axles. Just take a string and run it from wheel to wheel on the center line of the hubs. Next measure the distance from the string to the center of the crank.

I'm not so sure you should put too much creedance on what is said on the Spectrum site regarding steering. In the very first sentence he made a mistake and said that "rake" of 5.6 cm...he should have said "trail". In my experience, low trail frames tend to steer a little faster at slow speed but are fine at high speeds. Keep in mind we are not talking about super low trail, just on the low side of average.
thanks nmgtx
Apr 10, 2002 12:41 PM
45mm rake would give 56.8mm trail on 73.5 headangle nmcyclopathic
Apr 10, 2002 1:34 PM
re: what is overlookedcyclopathic
Apr 10, 2002 5:49 AM
is the vibration dumping properties of the frame (both due to material choice and frame design). While frames may have similar "big hit" absorption they will be quite different in high frequency spectrum and that alone has to do with fatigue and perceived "comfort". This becomes obvious on chip and tar pavement long rides.

Al as material is not any stiffer then steel or Ti, but given the same flex it will have much shorter lifespan. So the AL frames designed to flex less, they're made with oversize tubing.

Stiffer frame will resonate at higher frequencies, transferring more shock to your body through points of contact (feet, arms and buttocks). While it won't have major effect on last as it is mostly protected by the saddle, it will beat up your legs and arms.

Tendonitis is caused by tendons rubbing against bones. Think what happens when vibration is applied to leg during power stroke?

still I agree with Sheldon, there other things more important then material choice. Simple thing like putting foam grips under bartape has more effect then changing fork, tried and true. Also using thicker socks or gel inserts in shoes (or those carbon cranks ;).