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Episode #55 – Six Steps to Perfect Tire Pressure

Episode #55 – Six Steps to Perfect Tire Pressure

Tire pressure is as simple or as complicated as you make it, but this episode gives you a 6 step plan that takes into consideration all the factors associated with getting your tire pressure right in every situation.

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You already know there are a bunch of options out there whether we’re talking road bikes, let alone mountain bikes, but I’ve chosen to focus on road clinchers. I believe that covers the majority of competitive cyclists. If you don’t race on them, you will at least use them for training. Singles, tubulars whatever you call…maybe next time.

 

An interesting note is the slow shift towards clinchers. not that anyone is using them in the bunch yet, but the mass market is flooded with options. And while the hold-up is mainly due to rim technology and weight of the ‘hooks’. Tubeless will make its move – which can only be better for Semi-Pros. By the way I say mainly because tradition is a hard thing to break in road cycling.

 

Tire pressure is a little underrated and if you’re anything like me, a little neglected. But it really is a critical component to getting the most out of your bike. There are a bunch of different variables that go in figuring out what your ideal pressure should be, for any given situation.

 

Personal taste is a large factor here, but as a starting point I thought it would be handy to go through 6, yes 6 things to consider when searching for that the holy grail of pressures that will makes the dead roads turn into hot mix and hot mix into flying. That doesn’t really work, but you get the picture.

 

Six things to consider when searching for perfect tire pressure

 

1. Rider Weight: How a tire performs at a given pressure is relative to the rider’s weight

 

2. Tire Volume: Tire volume and pressure

 

3. Road Surface: What are the roads like?

 

4. Riding Style: How you ride is as important as where you ride

 

5. Rim Width: Ride em wide

 

6. Weather Conditions: Really the only adverse conditions that we get in road riding is wet weather

 

Perfect Tire Pressure

 

Wrap up and final notes

 

After all that you should have a solid starting point to go out and test. Remember don’t be afraid of higher rolling resistance when running lower tire pressures, be more afraid of your rims wearing down and exploding.

 

While we’re on the subject of pumping up tires. Do you keep the valve cap and washer screw thingy? I’ve never kept them, it is just easier dealing with flats that way. I found something that might change my mind on the valve cap front though. If you ride without valve caps, dirt can get inside the valve or even the tube, later returning to the valve and getting stuck between the valve’s sealing surfaces. The only way to get rid of the dirt is by inflating to max pressure and deflating quickly a few times. If this doesn’t work, you will need a new tube. I will have check out my bike to see if it’s a legit problem.

 

How to measure your weight distribution front to back.

 

I haven’t mentioned this yet but there is an 7th consideration. Weight distribution. Effectively the difference in pressure on the front and back of your bike.

 

Do you account for this already? What percentage difference do you run? There is a lot of noise out there regarding what a standard weight distribution of a bike and rider is. 50-50, 60-40, 70-30…you get the idea.

 

It’s hard to guess if you have no experience in this area. So I have pinched a way to measure your weight distribution from Lennard Zinn. Even if you just do it once, you will have a better understanding when making the final tweak to your tire pressure.

 

Step 1: Put a bathroom scale under one wheel and a wood block the same thickness as the scale under the other wheel.

 

Step 2: Weigh yourself standing on the scale while lifting the bike off of the ground.

 

Step 3: Sit on the bike perched on the scale and block and hold yourself up by touching an elbow against the wall. Have somebody else read off the scale reading.

 

Step 4: As a double check, turn the bike around so that the wheel on the scale and the wheel on the block are reversed, and take the measurement again.

 

Step 5: Calculate. Take your weight from step 2 and work out the percentage using the figure from step 3 or 4.

 

One will do.

 

This will give you an idea of where your weight sits. How does effect the final pressure? Drop the pressure on the front wheel because it holds less weight. By how much? You could get exact by using the numbers you just produced – or you could just use the Vittoria tires app. Either way it’s going to come down to personal preference from testing.

 

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Photo Credit: TchmilFan on Flickr

 

 

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  • Damian, great podcast about tire pressures. Had to voice my support for wider tires, specifically 25mm. Like you, I was skeptical about wider tires, believing they’d make me much slower. I started using 25mm on my winter commuter, and couldn’t believe how much comfier they were. They also handled a lot better on loose surfaces. In the wet, they were ace. I also noticed little to no difference in speed from 23 to 25mm.

    One thing left to another and based on my experiences with 25s, decided to try 28s and 32s. I put a pair of Panaracer T-Serv Protex 32mm tires on my commuter last winter. Sure, these tires were a bit slower than 25s, but they were much comfier and allowed me to ride virtually any surface imaginable. Singletrack, bad gravel roads. They were even better in the rain. Over a year and a half in with these tires and haven’t had to change them yet. Probably have another 2-3 months tread life left.

    On my Cannondale SuperSix Evo, I’ve opted to use Continental 4-Season 700x28s for my general training and road riding. Unlike a lot of standard measurement 28s, the 4-seasons really measure like a plush 26. This means they fit really well in racing frames with just enough clearance to make it work. These tires, coupled with a nice set of handbuilt wheels have made my bike ride like a supreme being. It’s also still wicked fast and I don’t notice any additional rolling resistance.

    These experiences have convinced me to go as wide as I can when it comes to tires.

    When’re you thinking of doing a podcast on cyclocross tire setups?

    • Hey Patrick, thanks for stopping by. Man, 28s! What tire pressures are you running? It’s interesting that you went through your commuter to find the benefits. I used a 28mm tire for a while on a commuter, but never dreamed of using that size on my race bike. You’ve helped sway my next purchase closer to 25s. I’ll also check out the Continental 4-Seasons.

      Cyclocross tires and setup is definitely on my radar. Expect an episode on that topic in the next month or so as we roll into the CX season. How is your season with the new bikes shaping up?

      • carlos

        HI THERE, there is no such a thing as a smooth road. nothing in the physical world is smooth. it might seem smooth but it is not. What concerns us is the degree of smoothness or roughness which is the opposite. Will it affect us in this particular subject? the answer is yes. any road is not smooth at all and it is so rough that the kinetic energy caused by the vibration of the road against the rubber is significant. this literally slows you down to a certain degree. the key is to find the optimal point. too much air or to little will cause similar effects, that will lead to increased resistance and lower speeds.
        I find it interesting how this is a studied physical phenomena since the tires were created about 100 years ago and there is still people in this sport that argues against that.

        if this would not be the case, we would be still riding on tires with no air in them, or maybe wooden ones as it used to be before the discovery of rubber and all the subsequent applications. Actually this is a historical fact.

        In 1888, John Dunlop invented the air-filled or pneumatic tires, for bicycles.

        by the way the kinetic energy is distributed among the butyl tube the tire rubber and the air inside the tire/tube. And this is not completely accurate since anything that is contributing to the weight that is being applied to the tires is absorbing this kinetic bouncing energy.

        • Damian Ruse

          Thanks for dropping some knowledge on us Carlos! This is more detail than I’ve thought about. I appreciate you taking the time to write this.

          • carlos

            thank you for allowing me to do so. By the way the key is to find the optimal balance between the rider’s weight and the tire pressure based on each tire. Each tire manufacturer gives you in their website at what pressure you should run the particular tire. this is based on total weight of the bicycle and rider together. This is also accounting for a 15% tire deflection. this is the amount in % of the total height of the tire that should shrink because of the weight being applied to it. 15% is consider to be the ideal deflection point for optimal performance. thanks again and good luck.

  • Darren

    Hi. Great podcast. I have just bought 25mm tyres, so the latest episode was very timely.

    Just one question though: And don’t take this in the wrong way…. Do you take breaths? Your voice, tone and sound levels are great (some podcasts have REALLY loud music, between really soft talking). But you talk as if you either don’t take breaths, don’t pause for full stops, or you have edited out all of the short pauses between sentences.

    Sorry to nitpick, but by the end of an episode, I feel like I have just ridden a race! Keep up the good work.

    • Hey Darren, what’s your impression on the 25s so far? Do they feel clunky, or too big for racing?

      Thanks for the feedback, it’s always welcome! I feel the same after I record each episode, sweaty and tired. I do take breaths, and only edit long pauses out. I think because I try and jam in a lot of information into a short amount of time, that I move through topics really quickly. I also get pretty pumped up talking about cycling. I’ll keep an eye on the levels when I’m talking over a sound bed, thanks for the heads up.

      • Darren

        Hi there. My initial impression was not good. I got Continental 4 seasons. I simply pumped them up to 120 psi and went for a ride over rough Tarmac and a bit of dirt. They seemed slower (much slower than my other wheels and tyres, which are Mavic Kysrium SLS with 23mm Mavic tyres) and no more comfortable than 23mm.

        But after talking to some people in my club and then listening to your (very comprehensive!) podcast, I did a bit of research. I weigh 75kg and the bike is about 8.5kg (with water, tools, etc). I ended up putting the front at 95psi and the rear at 100. Wow!

        Today I just commuted 50km each way to work over the same rough roads and dirt and some rain for good measure. This is the first time I’ve commuted this far and the tyres were really, really good. Definately not slower. My average speed for most of the morning commute was over 31km/hr (until I hit the dirt and rough road). Overall avg was 29.3km/h. The ride was much more comfy. My bike is a Spesh Tarmac Comp BTW – so not built for comfort.

        As for your podcast – the levels are fine. Really good. Some other podcasts are terrible. You turn it right up to hear what is being said and then get BLASTED when they play some music. The speed just sounds a bit fast. Noticeably faster than say a radio announcer, or audiobook reading. But hey, keep up the great work. I was put onto your podcasts by word of mouth and really enjoy them. It’s also clear that you do your research, so Bravo on that too.

        • I’m running 23mm rims as well. I’m really curious about 25s now. It won’t be a few months till I can buy some tires, but when I do I’m going to go 25s. I let you know how I get on.

          • carlos

            I know this is kind of a late response but sharing knowledge is always a good thing. the key for wider tires is the pressure. when you run 25s at 95 psi they feel like silk. i have conti 4000s. i chose these after a very long research, taking into consideration rolling resistance, puncture resistance and durability. i am 200lbs rider 5,11 racing cat 4 crits for now after only one season. Now the higher the tire pressure the more bouncing you will have when the tire touches the irregularities of the road. when this happens the kinetic energy of the impact between the tire and the road is dissipated into the air because there is less dampening force. every time you pump your tires to very high pressures you are increasing this effect b/c of lack of compliance. the final result is the tire bouncing more off the road and the kinetic energy being dissipated into the air, literally. by lowering the tire pressure you increase the dampening effect, your tires touch the road more and you do not lose as much kinetic energy into the air from the bouncing. this is pure physics and it has been proven. this only applies for uneven surfaces. if you do the same in a very smooth surface where there is no irregularities the wider tire will have more rolling resistance b/c of increased contact surface. for example a roller will have more resistance on a 25 than on a 23 or 21. on the road the physics change b/c the amount of rolling resistance you decrease from going from 25-23-21 is lost in kinetic energy due to the bouncing. therefore when you get a more wider tire by rolling lower pressures you create a more compliant tire that will absorb the road irregularities better. this effect is greater than the rolling resistance that you save therefore yes, you will be going faster.

  • carlos

    Sorry i forgot to say that i run 23f/25b at 85-90psi/F and 90-95 psi Back. i weight 200 lbs and race Crit mainly and the set up is great

    • Damian Ruse

      It’s a good point that you raise regarding the contact patch and bouncing around, versus a smooth road. I guess it’s hard to find a perfectly smooth road. So 25s would work for most riders.

      What about freshly laid Worlds or Tour road. Do you think there’s less bumping around?