mikethe

Hi,
Is there a rule of thumb whether it's easier/safer cornering during descends (and generally feeling confident descending)
on an Endurance bike geometry/posture, or on the Aero bike style (I'm not referring here by Aero to TT/TRI)?
Or the bike type not relevant here and it's all about riders skills.
Thanks,

DaveSSS 

If you're descending with many corners, you should be in the drops. It shouldn't matter much what type of drop bar road bike you're riding. Some people's problem is they really don't know how to steer a bike, based on some of the techniques that people describe using. You should know what type of steering input tightens or loosens your turning radius. I took a motorcycle training course that made it much more clear. I'm pretty fearless, but I have slid out on sandy pavement a couple of times. Dirty mountain road pavement is not a groomed race track. I ride where I have to watch carefully for rocks that fall off canyon walls and be ready to steer around them.

Iride01 

I've never heard any one ever talk one being safer than the other.

I doubt you'll find your safe for descending bike by amalgamating the opinions of all of us. You need to ride bikes until you find one that is in tune with you and you feel it a natural extension of you.

smashndash

Lower = lower CoG, which is better. Closer to 50/50 weight distribution also maximizes cornering grip, and most people are closer to 50/50 when they get low.

so get low. Unless it makes you uncomfortable. The most important aspect of safety is that you stay in your comfort zone.

qwaalodge

When descending and cornering fast, you'll feel most stable if you put more weight on the front wheel and as low as possible. That means crouching down as low as you can, moving forward on the seat, and on the drops.

You can do this on any geometry of road bike. You'll just have to fold your elbows more on more upright geometry. You get the idea.

But if braking performance is your priority, the position is the same, except, you move your butt farther back the seat. It will be a bit less stable but you get less chance of endo if you need to brake hard in an emergency.

mikethe

So, IMHO, lower CoG and 50/50 which means leaning forward (since the natural position biased backwards) hence "aggressive" riding position - leads to Aero bike, no?

smashndash

sure. But aero bikes aren't the only bikes with aggressive geo. And you don't need a really aggressive bike to get your torso low. And your weight distribution is dominated by your saddle position and ratio of front center to chainstay length, not the bar position.

Basically, no.

GhostRider62

I had a custom endurance frame built with the main stipulation being that it descended and cornered as if on rails when I would be shivering my ass off at 0 Dark 30 on unknown roads.

It does.

tomato coupe

My wife has a custom bike. It was supposed to corner on rails at noon, but the builder got it wrong at it corners on rails in the early afternoon.

mikethe

Can you please elaborate more of what features the frame had that made her descending and cornering purpose built?

Carbonfiberboy 

Descending safely through corners is almost entirely a matter of not being stupid, very little to do with the bike. Wheel wobbles are another matter and have been discussed on BF. It's impossible to know exactly what happened when folks go off into the trees, though i generally regard that as matter of doing something stupid. Know your bike, know the rules of safe cornering, like don't go cooking it into an unknown blind right-hander or have your head over the yellow line on a blind left hander (in right hand drive countries). That sort of thing.

Anyone have the link to that wonderful video of racers crashing in a hairpin, into cars, etc.? Very nice examples of emergency braking and sequential stupidity. I descend very fast, but also cautiously. On twisty roads, I prefer to descend on the hoods with good visibility and aero braking from torso and knees and just not pushing the limits of adhesion. Going down on a motorcycle is not the same as going down on a bicycle. I've done the former plenty and the latter hardly at all. Granted I could go around corners faster with a flat torso in the drops, but that's not the point for recreational riders who won't mind losing a little time in the corners. Around here, there are plenty of straights to tuck and zoom, then come up and brake for the corners. Using these techniques, I'm almost always the fastest descender on recreational event and group rides. I ride a 22 y.o. carbon road bike, slammed stem, race frame, but I'm so short it's really an endurance fit, 23mm tires, deep alu rims, CX-Ray spokes.

As far as position in the corners is concerned, the OP is about cornering during descents. It's my observation that the gradient in corners is usually steeper than on the connecting straights because you're turning down into the fall line, duh. So being on the hoods is good because you're air braking, much safer than wheel braking. I don't see that vertical CG location has anything to do with road/tire friction. OTOH, fore-and aft CG location does. That's why we put much of our weight on the pedals and bars when we descend, less on the saddle, straights and corners alike. Every time I've had a skid, it's been the rear tire that's gone out. OTOH, that's good. You can't catch a front skid, but you can catch a back tire skid if you have fast reflexes.

cxwrench

Maybe, usually no. Aero bike is no longer the appropriate term, TT or Tri bike is. Neither are designed to handle well, they're just supposed to be fast. A UCI legal TT bike will handle somewhat better than a pure Tri bike because they have to meet the limitations of the UCI rules while Tri bikes don't have to meet any rules. I would go so far as to say that nearly any road bike will corner more safely/handle better than pretty much any TT and/or Tri bike.

GhostRider62

You would have to ask the builder.

I suspect a longer wheelbase, the seat and head tube angles, and fork rake were key attributes. I doubt that the frame material (magnesium) was a factor. Ability to mount somewhat larger width tires is a big factor because wider lower pressure tires make descending bumpy roads easier. I do notice that the chain stays are longer than all my other bikes except the circa 1986 Klein touring bike up in the attic. The top and downtubes seem really beefy. SOrry not to be more helpful

qwaalodge

I also do air-braking on the hoods if I need to slow down! Helps save the brake pads and avoid overheating brakes

But I prefer to stay on the drops if I can whenever I get above 30 mph (not for aero but for safety). I used to stay on the hoods on descents until I hit a huge bump on the road at 40 mph and nearly lost hold of the hoods! I suppose you are less likely to lose grip of the handlebar if your hands is on the drops.

Vertical CG can affect handling on descents and also when climbing. On descents, higher CG will cause more transfer of weight to the front wheels due to the gradient. Also there will be more transfer of weight to the front wheels whenever you brake. I agree it won't affect total grip from both wheels but with more weight transfer, you'll have more grip on the front wheels for braking but less on the rear wheels. That will increase your chance of rear wheel skidding if you're using both brakes even if you're using much less force on the rear brakes.

big john

I think he's referring to regular road bikes which are marketed as "aero".

big john

I'm not a great descender but I believe there are differences in the way some bikes corner. The best handling bike I had was a short wheelbase, steep head angle, super stiff steel bike back when they were called "crit bikes".

As others have said. lower is better. Try a dropper seatpost.

mikethe

What I meant in the OP by Aero is to those road bikes with aggressive seating position design (oppose to entry level Endurance bike designs) leading to shorter wheel base, lower CoG, deep rims etc. and the question is whether those features have some advantages for more "safer" feeling during descends and cornering them?

cxwrench

Mis-read the OP. The 'aero' bike might have a 'safer' feeling...it might not. Depends on how you're fit on the bike. The tend to end up w/ more weight on the front wheel which is good. They are also possibly somewhat quicker steering which might not be good, depends on the rider. Deep rims...depends on the rider. They might add a bit of stability compared to a lower section version of the same rim just due to the added weight but they will be a bit more of a handful in crosswinds. The difference in trail between a Madone and a Domane is 2-3mm which is small but just on the verge of being noticeable to many people. The Madone reach is generally a couple cm longer and the stack is lower putting more weight on the front end. The Domane is a couple cm longer but I think wheelbase is the least important metric when talking about handling. I wouldn't buy a bike for it's handling I'd buy it for it's fit. Nearly any bike built these days will handle well, bike designers have had decades to work things out.

genejockey 

The best descending bike I have is a Battaglin from the early 1990s, which I bought as a frame. It corners like it knows what to do. I don't know much about the geometry, because there's no catalog that I can find.

asgelle

I'm not sure I follow. I can get the same fit over a very wide range of frame sizes. At the small end I might require a 140 mm stem and have 350 mm of seat post exposed, while a large one might use a 60 mm stem with virtually no seat post showing to put me in the same position. The reason I wouldn't choose either of these, but one in the middle would be to get the correct handling.

cxwrench

I guess I'm saying that the correct fit also means the correct body position being where it should be on the bike to ensure correct weight distribution thus providing the 'correct handling'.

PeteHski

Absolutely agree here. Vertical CofG is critical when descending and hence why dropper posts became so popular in mountain biking. But as a vehicle dynamicist I can also say that it does affect total grip from both wheels too. When you get dynamic weight transfer, you always lose more grip at the rear than you gain at the front (since the vertical load vs grip curve is non-linear). So lower CofG with less weight transfer is always better overall.

smashndash

There's also angular moment of inertia. The higher you sit, the more critical it is to be smooth with your inputs. Suddenly diving into a turn could "shock" the tire and cause a slide. It's less likely with a lower center of mass.

PeteHski

Lots of factors, but I find bikes with modern endurance geometry i.e. relatively long wheelbase, slacker head angle, more trail, lower BB the most stable and confidence-inspiring when descending at high speed. The trade-off is slower handling, but I rarely find that an issue with a 7-8 kg bicycle! By Aero bike style I presume you mean a modern road race bike, which will tend to have a shorter wheelbase and more aggressive steering geometry for quick handling. These bikes can feel relatively twitchy and nervous on fast descents, but there isn't that much difference when comparing modern bikes. So yeah it is mostly about rider skills.

PeteHski

Yeah, sitting lower on steep descents is night and day easier/safer. Like the pro who used a dropper post recently to win the Milan-San Remo on the final descent.