|Wheelbase and climbing performance question||Chainstay|
Oct 1, 2003 7:20 PM
|I recall reading that longer wheelbase bikes were slower on the climbs compared to tighter frames. The explanation had to do with the relative mechanical advantage of the shorter frame. Does this make sense and how so?|
|Oh, good, another chance to make an ass of myself...||Cory|
Oct 1, 2003 7:44 PM
|I've read that all my life, too, and never questioned it until I read your post. When I tried to analyze it, though, I couldn't think of a reason it should be true. On a mountain bike, where traction is sometimes a problem, there might be an advantage in having more weight on the rear wheel (although if you lighten the front much, you'll pick it up--you can feel the difference sometimes just by shifting your head fore and aft).
But on a roadie...I'm trying to visualize the flow of power from my legs to the rear tire, and I can't come up with a scenario where it makes any difference whether the hub is 14 inches or 20 inches from the BB.
|re: Wheelbase and climbing performance question||LC|
Oct 1, 2003 7:58 PM
|As long as it does not weigh more or have more flex then it will climb the same.|
|The old chainstay length argument maybe...||Spunout|
Oct 2, 2003 3:53 AM
|in that longer chainstays (longer wheelbase) flex more, thus somehow lose mechanical advantage climbing or sprinting. Tell that to my 853 Pro Zurich.
FWIW, BB stiffness is also enhanced by the downtube.
|I think its a crock, but...||Ray Sachs|
Oct 2, 2003 4:31 AM
|...shorter chainstay bikes can FEEL like they're climbing faster. This has nothing to do with how fast they're actually going up the hill, but the "noise" that each pedal stroke causes in terms of side to side motion. Every time you stomp on the pedal, you get more feedback than you do on a bike with longer stays (which goes closer to straight ahead and spends less time jerking you back and forth) and it really does FEEL like you're climbing faster.
A few years ago, I had two road bikes, one with 40.7 cm stays and one with 43.5 cm stays. The shorter one felt quicker and faster, but my average speeds were always the same and I always hung with the same people on climbs, dropped the same people on climbs, and got dropped by the same people on climbs regardless of which one I was riding.
When you get into REALLY long stays (like 45-46 cm), things start to get really slow, but I think that's because stays this long are only found on touring bikes and there are a lot of other things going on with a touring bike that can slow you down. On my touring bike, I CAN'T hang with the same people on climbs that I can on my road bikes.
|re: Wheelbase and climbing performance question||tarwheel|
Oct 2, 2003 4:33 AM
|My GIOS Compact Pro has adjustable rear dropouts that can shorten or lengthen the wheelbase about 1 cm. Supposedly one of the reasons for this is you can shorten the wheelbase for climbing. (The other reason is that the dropouts are replacable if they ever get broken in a crash.) My understanding is the shorter wheelbase is for better weight distribution while climbing -- I think that shifting weight toward the front helps keep the front wheel planted on the ground. Not sure if that makes sense or not, but my Gios does seem to climb better than my steel Merckx Corsa that weighs about the same and has chain stays at least 1 cm longer. BTW, I kept the dropouts fully extended on my Gios because I think it rides smoother with longer stays, but they're still relatively short (40 cm extended, 39 cm shortened).|
|re: Wheelbase and climbing performance question||hudsonite|
Oct 2, 2003 4:44 AM
|There may be an argument that a longer wheelbase climbs slower. But in reality, climbing performance has more to do with the rider than anything else.
The conditioning and weight of the rider has more to do with getting up the hill than the bike. A light, stiff and efficent bike helps a good rider, everything else being equal, climb faster. A shorter wheelbase, may help in creating stiffness, but that is a big if.
Most road racing bikes have similar geometries. The differnence in wheelbase is minor. I would suggest 30 minutes of extra training a day on the hills is going to make more of a difference than any bike would.
|re: Wheelbase and climbing performance question||irregardless|
Oct 2, 2003 6:02 AM
|I have found it to be true, but more based upon the trail up front than the chainstay length. The less trail (steep HTA, high rake), the more I feel on top of the front wheel than behind it, the less the front wheel wants to flop to the side on steep ascents, so the bike tracks true uphill with miminal wasted power. This may be more pronounced for slower or heavier riders like me, but I'll take any help I can get. Of course, that kind of setup doesn't inspire confidence when you have to turn around and descend.|
|Anyone recall Steve Bauer's bike...||torquer|
Oct 2, 2003 6:43 AM
|with radically extended chainstays?
He rode it his during his last year or two with Motorola (and thus his last years as a pro). He had it built to ease his back problems, as best I recall.
Now granted, Bauer was no R. Heras, so this design wasn't about climbing performance, but it couldn't have put him at too much of a disadvantage. Even during "flat" stages and classics the pros have to tackle hills at speeds that would leave most of us cleaning our breakfast off our Sidis.
|How about this -Where is an engineer when you want one?||Chainstay|
Oct 2, 2003 2:56 PM
|You are riding along nicely on a level and then come to a 15% grade hill. Since it is rear wheel drive, the effort required to lever the front end up the angle with the shorter bike will be less and you gain an advantage over the longer bike. It's probably damn small but this is all for the academic interest anyway. Presumably you give it all back at the top when the long bike drops it's front wheel down but by that time the extra millimeters gained will have shattered the confidence of the rest of the pelotron.
I'm still wondering if because you are constantly working against the acceleration due to gravity, that this mechanical advantage effect will be acting the entire time you are climbing. Comments?