billridesbikes

I prefer to have my butt in the saddle with my weight shifted over the front wheel as much as possible on a high speed decent. You want maximum contact with the bike and lifting out of the saddle will make the bike feel more ‘jumpy’ as all the motion is now translated through only your elbows and knees even though your weight is supplying the same downforce.

Don’t ride the brakes, instead pump them to modulate your speed. Applying brake decreases your tire adhesion to the road. This can be especially critical in turns because your tires also need extra adhesion to hold on to the road as the bike leans, therefore scrub your speed prior to entering hairpin turn so you don’t need to brake until you exit the turn.

If possible ride in the right tire track in the right lane, especially if you’re going as fast or faster than the traffic. The car tire track here is generally clean of debris and smoother than any other part of the lane. Look far down the road for trouble, remember at 35mph you’re traveling almost 20 yards every second which is a thousand times faster than my Detroit Lions can cross the red zone.

cyccommute 

Why try to match the rolling resistance to the narrower tire? If that is the point, why not just run the narrower tires? They are lighter.

Very close. I’ve looked at calculators and they give me ridiculously low pressures. Calculators have given me a pressure for a 28mm tire of 78psi for the front and 114 psi on the back. For a 37mm tire, the pressure is 46psi and 69psi, respectively. I would never ride at either of those pressure for the 38mm on just about any tire. First, I hate riding on flat tires. I’ve ridden tires at that kind of pressure when the tire is going flat and I don’t simply don’t like it. At those kinds of pressures, I’d be bottoming out the tires on even small bumps. Alternatively, I wouldn’t run 114psi on the 28mm tire. I wouldn’t run that pressure on a 23mm tire. I use about 100 psi for both.

I don’t ride 37mm tires much. I might go as wide as a 35mm tire on a road bike but seldom wider. The calculator suggests that I use 60/92 psi (front/rear) for a 32mm tire. 90 psi is about what I use for that wide a tire.

nomadmax 

Body position on the bike is job #1 when descending. If you don't have that, being good at everything else might not matter.

Pedals at 3 & 9 supporting yourself with your feet and core muscles not your hands or butt, torso hinged at the hips, back of butt behind rear of saddle (you should be able to feel the wings of the saddle on the backs of your thighs), elbows bent/pulled in, shoulders low and hands in the drops covering brakes (don't death grip the bars or the brake levers, gentle inputs), head and eyes UP looking forward much further than you normally would. Roughly, MPH x 1.5 is Feet Per Second, NEVER look away. Cornering outside, inside outside will give you a better view of what's ahead (and a view of you to others much sooner) but temper that with off camber surfaces or rough stuff which should be avoided. Not all curves in a descent have to be made, IE sometimes it's safe/most efficient to ride straight thru one to get to the entry point of the next (without crossing the center line). Knowing how to brake effectively is VERY important. I won't go into it here because I don't have time until January to debate proper technique with the "engineers" or anyone else who's never exceeded 100 KPH on a descent

There's more to it than this ^^ but that's the quick and dirty. If something surprises you on a descent, it's your fault.

Kapusta

Because the lower pressure gives you better comfort, traction, and control on rough surfaces, such as what the OP is describing. Also more control and traction on loose stuff.

It is what is responsible for the larger tire patch you mentioned earlier.

We must not be riding the same larger tires, because in my experience, a set of high performance 35-38s roll as fast as any set of 23-25s I’ve ever tried at literally half the tire pressure.

The reason many people have the impression that larger tires at lower pressures roll slower is that up until recently, anything over 28s were eaither cheap commuter tires or bombproof touring tires (like Marathon Supremes)... both of which are slow rollers, unless you pump them up rock hard. Try a set of Rene Herse tires or something like a Gravel King slick in the mid 30s sizes, and it is a very different story.

But back to the OPs issue... if you are having issues keeping control over rough surfaces, lower pressure is a no brainer, IMO. And larger tires allow that. If he can go up a size on the tires, the corresponding drop in pressure will help him.

As an aside... At 175 lbs, I’m done with anything smaller than 35s, which I would never run over 45/55 psi unless I had a load. For now I’ve settled on 38s at 38/45 for most uses, maybe go a tad higher for all smooth pavement (which does not exists around here). I did the small tire/high pressure thing for many, many years (thinking the same things you are saying) before trying a set of performance 33s (Jack Brown). It was an eye opener for me and I am never going back. It was like leaving an abusive relationship.

cyccommute 

Simply lowing the pressure doesn’t give you that. That’s why I said what I did about wider tires rather than concentrating on pressure. Lowering pressure is only part of the equation and not the most important part. A 37mm tire is still a very narrow tire in the grand scheme of things. Additionally, if you lower the pressure too far, the tire doesn’t give you more control because the tire’s sidewalls aren’t stiff enough to keep the tire from folding over. A soft sidewall results in tire squirm which means a lack of control.

And a wider tire gives an even larger tire patch.

There is a difference in rolling resistance but I really question the claim that it’s half. Comparing a Vittoria Voyager (37mm) to a Vittoria Zaffiro (25mm) on Rolling Resistance, cutting the pressure in half doesn’t result in a lower rolling resistance for the wider tire. The Zaffiro has a 16 W rolling resistance at 100psi. The Voyager has a rolling resistance of 21W at 45 psi. The rolling resistance of the Voyager doesn’t equal the Zaffiro’s until 75 psi. In other words, a “literally” half the tire pressure, a wider tire from the same manufacturer wouldn’t roll faster. It would roll the same at 20% reduction in pressure and roll slightly faster (14W vs 16W) as the narrower tire at 90% of the pressure. That also doesn’t take into account the change in aerodynamic drag nor the difference in weight (150g of rotating weight)

The reason many people get the impression that large tires at lower pressures roll slower is because they do. The difference in rolling resistance due to the width of the tire is small and likely negated by other factors. For elite athletes it might make enough of a difference to be of a concern. For the rest of us, it’s only a small difference that is barely noticeable.

His problem isn’t with pressure. It’s with width. The Specialized Roubaix is a road bike that isn’t meant for anything wider than about a 28mm tire...if it can even take that. It’s just the wrong tool for what he wants to do.

I have bikes from 25 mm to 55mm. The fastest bike is the one with 25mm tires. The slowest are the ones with 55mm tires. A lot of that speed difference has to do with the tread...the 55mm tires are the slowest and happen to all be knobbies. But, in all honesty, the speed difference between the widest knobbed tire and the narrowest road tire is relatively small. On pavement, I can do about an average speed of about 12mph on the knobs (it drops to 10mph on dirt). On the wide road tires (32 to 35mm tires), I can average about 15mph. On the narrow tired road bike, I can do around 17 mph. There’s only about a 5mph differential between all the bikes. That’s not much.

njkayaker

For long distance riding (especially), a 5 mph difference is huge.

That's also the difference between a C level club ride and a B+ ride.

cyccommute 

That’s a 5 mph between a wide knobbed tire and a race bike tire. That’s not that much given the differences between the tires. For my road bikes the difference is more like 3 mph.

I don’t follow club ride rules so it makes no difference. I also wouldn’t show up for a fast road ride on a mountain bike with knobbed tires. On the other hand, I wouldn’t show up at a mountain bike ride on race tires...or any road tire for that matter.

bruce19

Caveat: I have not read all the responses. I am assuming you mean "winding" rather than roads hit by wind. It would also be helpful to know whether you take a proper line, aka: the racer's line, when going through corners.

njkayaker

3 mph is huge.

No difference? To you? So what?

Anyway, the point wasn't "club rules" It shows that 3-5 mph is a big difference. It's the difference between a kind of slow rider and a kind of fast rider. And lots of people are interested in going faster.

It probably doesn't matter toodling around the neighborhood.

Kapusta

No,
Much of this discussion is subjective. This point is not. The size of the tire patch is a function of tire pressure, NOT tire volume. For a given load, two tires of different sizes at the same pressure with have the same area of contact patch.

None of the advantages I mentioned (comfort, traction, control on rough surface) will be gained if you run a larger tire but don't drop the pressure. Other than gaining some float in deeper loose stuff, you will gain almost nothing, Especially on the road. You may disagree, but you are in a small minority.

I did not say ALL tires would give you the same rolling resistance at 50% pressure I was speaking about the ones I use.

But regarding that comparison; that is not a good comparison as these are completely different tires. They are NOT different sized version of the same tire. The larger tire has an extra puncture resistance layer (which will add RR). Also, it is not a slick... it has some tread.. Remember, I specified PERFORMANCE tire, and NOT a touring tire. And then there is the issue of the reliability of using roller drum testing to predict real world results. This is not universally accepted. I take them with a grain of salt as they deform the tire differently then a flat surface does.

Anyway, this topic (tire pressure and larger tires) has been discussed and reported on exhaustively. I'm not going to rehash it here. When it comes to the issue of pressure and rolling resistance in larger tires, my take on this is the one gaining more acceptance as more people try high performance high volume road tires (which were few and far between up until a few years ago).

Symox

Just put some 28 Gatorskins on my Specialized Roubaix (there is plenty of room cyccommute ). You guys are right, here is a huge difference in comfort (running at 90psi (115 is max). Should I run at a lower psi? Thanks for the inspiration!

Also tested the lifting weight (not standing) off the seat and it works! Ready to try some hills again.

Symox

Went for a quick ride - wow, why haven't I done this before? For years I was riding skinny tires because it looked cool and I thought it made for a better ride. I love the handling and comfort going from 23 to 28!!!

Thanks sooooooo much everyone.

BTW, so far I like the Gatorskins.

Symox

A HUGE thank you to everyone who replied. I just finished the same ride that I originally had issues going downhill only this time I used 28s with lower pressure instead of 23s, stayed in the drops, feathered the brakes and lifted (slightly) my butt off the seat - it felt like a whole new bike!!!! Not only did I never feel like I was about to lose control like last time, I actually felt like the bike was sticking to the road so much better that I was able to ride more aggressively.

I'm really liking the Continental Gatorskins in 28 that I got. Great traction

I'm so happy right now and I love my bike. No more 23s for me!

Mulberry20

I use a technique that is helpful in skiing as well. If I am going fast I went my body weight off the saddle and distributed as evenly across the bike as possible. Being off the seat and relaxed moves the vibration through the whole body making it much easier to ride. I also use my upper highs to grip the radius of my saddle.

I use 25’s on my bike but as supple a tire as possible. Conti 5000 while otherwise great are horrible on chop. The best tires to keep you confident are the Pirelli P Zero, Veloflex Corsa Evo and the Vittoria Corsa 2.0. All three are supple. The latter two are very high TPI cotton/poly casing and are like putting slippers on your bike. The Pirelli is a vulcanized tire and will last the longest but still manages to be incredibly smooth.

Symox

A HUGE thank you to everyone who replied - you may have prevented a crash:

Was going down a hill pretty fast when I saw it - a gnarly patch of tree root distorted road. A little voice inside my head said "lift your butt, don't hit the brakes, stay relaxed"
It was scary but surprisingly stable. I'm positive if I was sitting in my seat and hit the brakes it would have been bad.

so thanks everyone!!!!!!!!!

billridesbikes

Yup, nice job.
"Nothing good happens when at the last second you pull hard on the brakes." -Juliet Elliot

Symox

Want on several more windy hills and its been fantastic. No more "I'm about to lose control" feeling - in fact I am more aggressive as I've gained confidence.

Thanks everyone

The 28mm tires with lower pressure and better technique made a huge difference

79pmooney

Another point - use a firm grip (not a death grip!) but keep you wrists and arms loose. I was taught to always ride conditions like that on the drops so if I did hit that unexpected whatever and my grip did come loose, my hands are still on the drops, meaning I can trust my less than death grip is perfectly safe. And less than a death grip plus less than tight arms means they act as shock absorbers, allowing the front tire to track better over rough pavement.

rsbob 

Glad to hear your descending has made real gains. It’s amazing what the right equipment coupled with the excellent advice above can result.

The only piece of advice I didn’t see above, was when fast cornering, with your outside pedal down (inside up) when you point your inside knee out about 45* you can gain additional stability. Watch some videos on YouTube of racers descending mtn passes to see what I mean. You don’t need to be a racer to get the benefit.

rydabent

You may be a candidate for a tadpole trike. They have 3 wheels to keep you stable, and setting low they are really not affected that much by wind trying to blow you into the driving lane.

tomato coupe

The OP is successfully dealing with the issue. There's no reason to condemn him to a life of 3-wheel misery.

Symox

Another fantastic ride. The technique improvements along with 28 tires at lower pressure makes the bike feel incredible.

And someone asked, I really didn't mean windy as in blowing, I meant windy (winding) as in lots of curves.

To the person saying the Roubaix is the wrong tool for the job I say, meh. Works for me

billyymc

Symox - one other suggestion with regard to overall bike handling (and specifically to descending) is if you have access to a mountain bike get out and ride some trails. Descend on narrow single track and you'll naturally get your butt off the seat (sometimes even behind and below the "normal" seat level depending on how steep).

Symox

I've been doing a lot more riding and I cannot tell you how much more stable I am on the bike with the change in tires and technique. For years I was scared I was going to lose control on fast downhill runs. Now the bike literally feels like it is sticking to the road!

Thanks again everyone!!!

Symox

With 28 tires at 80 psi and using correct technique I was able to go down the steepest street full speed twice. It felt secure - I no longer get that “about to lose control” feeling anymore. I have NEVER gone down this street without using brakes before.

Thank you everyone- you are changing my riding for the better.