nerobro

TL;DR: Who's done testing, and what were the results, finding the maximum amount of traction a road bike tire can generate.

Hello Everyone,

After watching some videos of TdF descents, and discussing them with some of my friends, we have some questions.

First, the lean angles achieved are less than spectacular. MotoGP bikes are getting all the way down to 63 degrees of lean. I do understand that is.. remarkable, requiring tuned flex in the sidewalls, headstock, and swingarm, along with some hilariously sticky tire compounds.

I've read tire reviews, and they almost never seem to concentrate on traction. Traction seems to come as an afterthought, after rolling resistance, aerodynamic benefits, noise, tread life, and even color.

I've never run into a ... I was about to tell a lie, but I'll share that story at the end... I've almost never run into a bicycle tire without enough traction to allow me to pick the back tire up with brake force alone. So longitudinal traction isn't a question. But I have been caught out and lost traction horizontally.

So, has anyone done testing, and reported the data, on how far a road bike can lean over?

My hunch, is that a road bike, with sticky tires would be able to get well past 45deg. Everything on a bike is set up to lead to good traction, and good recovery from slides. The rider is high up, so the CG is a long distance from the tires, that makes the pitch moment long. The wheels are high rate springs, and the rims and tires are light, so should be able to follow the road well. I think the biggest failure would come from the headstock not being stiff enough to allow the wheels and fork to do their thing.

Since I teased it.. I bought a folding bike. A clone of the Sinclair A-Bike. It came with solid foam rubber tires. The brakes could lock either tire up. And even a fast application of steering would cause the tire to slide. That wasn't the bikes only problem.. but that is still another story.

garciawork

All I know is that I have never been held back by my tires, they have been held back by me... Lowsided my motorcycle when it was 29 degrees out (still my fault for taking a turn to fast...) and have been a pansy about fast cornering ever since. I would like to know what a tire could achieve on a gravel free road though.

Lazyass

I raced sportbikes in the CMRA in the 750 class until this season when I moved from Texas. On a sportbike at the track (not the street), you're running less than 30psi in the tires. Racing slicks are in the 20psi range. These guys you see at the TDF are running what, probably 100+? The tires are not going to flex enough to get to extreme lean angles. Not to mention road bikes have no suspension. One thing that can translate from motorcycles to cyclists that I don't see them doing that they could, because I do, is change their body position when cornering. If you're turning right you can lean your body down and to the right off the bike. That allows you to keep the bike more upright when cornering which increases your contact patch which allows you to........ corner faster.

I've always said that professional cyclists would benefit from training with motorcycles on the track, even if it's just a one day track school. Not for just body position but braking techniques, proper lines, ect. I cringe when I see some of these cyclists on TV cornering, they could be so much faster and would wipe out less. The pic below is just a very, very basic example of what I'm talking about. The rider on the right would be going through the corner much faster than the rider on the left. He could probably make an outside pass in the curve.

nerobro

When a motorcycle is leaned over, it's "suspension" is effectively bound up. Most of the suspension action on a deeply cornering bike is through tire carcass, rims, headstock, and swingarm flex, instead of those expensive suspension components.

Speaking of suspension, bicycle rims wheels are much more springy in the latteral direction. The key to really good suspension is low unsprung weight, and relatively high spring rates. The weak spot on a bicycle, is that carbon fork, and headstock.

On the "lean off the bike" thing. It doesn't make the contact patch bigger. It puts you on a part of the tire that scrubs less. As you lean a tire over, the leading, trailing, top, and bottom bits of the contact patch are sliding relative to the ground. That scrub "wastes" available traction. The less the lean, the less the scrub, and the greater the available traction.

I'm really not looking to talk techinque though. I"m kinda looking for the most sticky bits of rubber out there, and how many G's a bike can generate.

As a motorcycle goes, a bicycle is pretty good. You've got 120-200lbs of mass up high, with a fairly small moment of inertia, and "suspension" that's only in the 2-3lb per end of the bike. A 60:1 or 100:1 unsprung is pretty freaking impressive.

I am really starting to suspect the weak point of the whole system is the headstock, and having to low of a spring rate up there is allowing the front tire to bounce.

You're right on the tire pressures. There's not a lot of rubber on the road when you compare to a motorcycle. I wonder how much of a difference that makes? I"m certain that's testable. If GCN is to be believed they run from 70-110psi depending on tire width and rider weight.

StephenH

The problem I notice with a bicycle is not the lack of traction, it's the variability in the traction. You'll have a few corners that are perfectly clean, a few where you get a gritty feeling as you ride through them. The places where you see motorcycles lean the most is on a track, where they know it's clean, and they're going through the same curves over and over. Put them on a road they've never been on, and that probably doesn't work as well.

JamesInSJ

It's funny you say that. I think the same thing watching cycling and not from motorcycle experience, but track car driving. I'm sure the turn-in/out lines are fairly similar. It amazes me how fast I catch up to many other riders on both shallow and steep descents just by following clean lines.

big chainring 

Bikes and motorcicles dont equate. Different centers of gravity and the weight differences. Doesnt matter what kind of compound your tires are made with, at a certain angle, you're going down.

Now what you can do for some fun is ride on a banked track. Feel the bike jamming your shoulders as you go into the banking at top speed.

nerobro

Bikes and motorcycles equate exactly. And yes, at a certain angle you're going down, that's true with a big motor and without. The question is, what is that angle :-) Motorcycles are .. I need to check the number, but we'll go with 2g for the sake of argument. A 45 deg lean angle is what you get at 1 g of cornering.

Bicycles give up some traction by running high tire pressures, higher ground pressure hurts the coefficient of friction for rubber. They also get some back by having very low unsprung weight. (A bicycles suspension when laid over is spoke tension. And the effective unsprung weight is in the 2-4lb range, where on a motorcycle it's 20+lbs, my motorcycles are somethingl like 50lbs...) Bikes also have a very high unsprung weight ratio, where you have say a 120lb rider with only 3lbs of unsprung weight, that's almost a 43:1 unsprung weight ratio. A motorcycle is likely to be 10:1. They also have a big cornering advantage with their high CG. Higher CG's make the breakaway (when a tire starts sliding) speed slower, so you get quite a bit of time to react. Road bike tires are also narrow, so they don't have a lot of scrub when leaned over, that lack of scrub makes their departure pretty sudden.

Come to think of it.. I'm going to be at the velodrome tonight :-) Yes.. that velodrome. I've been two years since I've ridden there. I'm going to get my butt handed to me. :-) and I'll enjoy every minute of it.

merlinextraligh

Davis Phinney, who was pretty good at taking a corner and descending would disagree.

https://books.google.com/books?id=LDm...nering&f=false

https://www.alicehui.com/bicycling/Sk...d%20safety.htm

Lazyass

Yeah they do. You should read what I posted again, then explain exactly how keeping the bike more upright when cornering would not increase the contact patch and traction.

nerobro

The man's wrong. Pushing the bike down into the corner DOES make it "feel" better, but it's not faster. Due to scrub. If you're upright, and your bike is leaned over, you're sacrificing traction.

However, that's not what i'm trying to get at with this thread. What tires, and who, have pulled the most lateral G's on a bike.

Lazyass

Mr. Phinney would learn a lot from going to a track school, which I don't believe he has. I read your google links and if he leaned off the bike the way he described on a motorcycle he would crash. When he talked about not counter steering like on a motorcycle, it sounded to me like he had never been on a motorcycle or at last ridden it properly. And when he talked about crashing, it didn't even have anything to do with his cornering technique.

Therefore, the proper cornering technique is to sit on your saddle, relax, torque the bike just a little to cause the tires to bite, and let the bike arch through the corner. Your upper body and head should drop lower and toward the inside so that your head will be just about over the inside brake lever. This is to better position your center of gravity on the bike in relation to the centerline of the bike. It is also important to keep a smooth arching line through the corner. Bobbing and weaving will throw your line off. It is just that simple.

Cornering

merlinextraligh

Do you know who Davis Phinney is?

The winningest bike racer in American History. He won more than 328 races, including multiple stages of the Tour de France.

His teammates called him the Cash Register because he was a guarantee to get prize money in Crits.

You don't win TDF stages, and dominate crits without knowing how to descend and corner.

I'd take cornering advice from one of the greatest bicycle handlers ever, before trying to apply motorcycle experience to bicycling.

Lazyass

I'll give him a cookie. It seems he needs to work on his braking technique, because that's why he crashed. Probably got target fixation as well heh

lsberrios1 

I notice the bad g spot on my tires comes in at around 17degrees.

WhyFi

Maybe I'm mistaken, but motorcycle tires and road bike tires seem to have quite different cross sections. I also have a to believe that a motorcycles ability to get on and off the power, while leaned over in a turn, is a pretty significant difference, too.

WhyFi

How many people are you riding with when you're talking about said catch-ups? I neither race, nor in fast packs, but I'd be interested to hear the opinions of those that do when it concerns an individual gobbling up lots of lane real estate, moving side-to-side, in an effort to set-up/hit the apex/exit/whatever.

Lazyass

Well obviously you don't want to be leaning off the inside of your bike when you need to pedal. IMO it's an irrefutable fact that you will have more traction with a bicycle tire when the bike is more upright than leaned over. How many times do you see riders wiping out descending on mountain stages? Almost every stage you see it. I'm not talking about hanging off the bike and dragging knee like you're on a GSXR750. Just get down and a little to the inside with your upper body and chin over your inside arm so you don't have to lean your bike so much, it's not a big deal. It actually makes it less scary when you're going fast.

gl98115

Jobst Brandt thinks that max lean angle is around 45 deg on clean dry pavement.

Descending by Jobst Brandt

WhyFi

There is no such thing as an opinion on an irrefutable fact. You either SHOW that it's a fact or it's just your opinion.

Lazyass

You gonna be okay?

JamesInSJ

~2 years, weekly club rides, 10-25+ riders, most of the riders much more experienced than me and often (until recently) on much nicer bikes. Our policy is to rarely pass each other on the downhills unless on straight, safe sections, so there really isn't a discussion for me to participate in on the second part of your concern.

WhyFi

Um, why would I be anything other than okay? I'm not the one making extraordinary claims and failing to back them up, after all.

nerobro

Something tells me road bikes could go further. But we're traction compromised by the desire for lower wind and rolling resistance. Thank you for the link. That's still 1.4g. :-)

lsberrios1 

I used to ride motorcycles on the canyons and the track... It is scarier for me on the bicycle but I think some of it translates well. I do put my upper body in a lower position, take the weight off the bars and my body towards the way I am leaning. TRying to keep the biggest contact patch on the tire as well as absorbing bumps without upsetting balance is what keeps the rubber down for me best. Sometimes I am able to do so, other times not so much since it may depend on the people around me when I am riding in a group.

Same sunglasses