Tech Tire pressure

#1
Sorry, too lazy to check if there are previous threads on this, but another interesting episode of Cycling Tips podcast:
CyclingTips Podcast: Where the Rubber Meets the Road: Rethinking Road Bike Tire Sizes and Pressures
https://overcast.fm/+GrDIAdmzg

If you haven't already checked out the research that Jan Heine is doing on this stuff, it is really interesting (even if you hate randonneur, the guy used to race, and he's a PhD).

Some takeaways:
  • There is no magic number for pressure, it depends on the road and the rider
  • Generally lower pressure is better (assuming fairly supple tire)
  • We perceive higher pressure as faster because of the higher frequency vibration
  • Lower pressure = less flats
  • Interesting chart to start with as reference: http://www.bccclub.org/documents/Tireinflation.pdf
Just my summary, check it out for yourself!
 

macrophotofly

Maximum Pace
Aug 27, 2012
581
234
73
London, UK
www.macrophotofly.com
#2
That chart attached seems to suggest I should have my GP 4000 25's down below 70 psi. I do regularly run below 90 but do try to keep above 80. Conti recommends 95 psi for them - probably for a lot heavier rider than me - even so, 70 seems a bit low. Might give it try on a flat route to see how it feels
 

dgl2

Maximum Pace
Nov 3, 2007
284
48
48
Tokyo - Minato-ku
#3
Yep, Jan Heine (who often comes to Japan in recent years) is the leading promoter of the fat, low-pressure supple tire 650B movement. As a randonneur (no self-hatred) I am trying to experiment with fatter tires because they are more comfortable, and cannot worry too much about whether the are a wee bit slower or faster.
I guess I feel that Japanese road surfaces near Tokyo are smooth enough that we will not notice any benefit from lower pressure ... but who knows.
 

leicaman

Maximum Pace
Sep 20, 2012
2,514
2,191
133
Asakadai, Saitama
#5
I used to ride my tubs at 100psi for no other reason than it was a nice uniform number to use ;). I then read about people riding much lower pressures so I lowered them to between 80-85 psi. They felt good on the flats but then I really didn't like them on the descents. I'm back to 100 now. Nice and simple, for a simple guy.
 

Chrisisism

Maximum Pace
Sep 6, 2014
112
107
73
43
Mejiro, Toshima-Ku, Tokyo
#8
I will lower my pressure ASAP...
Need even wider rims though, in order mount 28 and not suffer in the aerodynamics department, a topic they could have talked a bit more about as well, I think. Enve's new SES 4.5 AR disc would be my perfect wheel in a dream world
 
#10
I will lower my pressure ASAP...
Need even wider rims though, in order mount 28 and not suffer in the aerodynamics department, a topic they could have talked a bit more about as well, I think. Enve's new SES 4.5 AR disc would be my perfect wheel in a dream world
Totally agree about wishing they had talked more about aerodynamics. Buying a new set of wheels is a big purchase, but putting big tires on narrow rims doesn't seem like a good solution either, so I guess I just have to keep my small tires and try to keep minimal pressure in them and see how it goes.
 

Heath

Maximum Pace
Dec 13, 2014
525
452
93
47
Kamagaya
www.nanairogakudo.com
#11
@Cory M.

FYI, this is what I do...

I always keep a lower pressure in my tyres for training (90 PSI), then if I want to have a crack at a segment I run a fresh 110 PSI in the tyre. The training pressure creates a tyre drag, so it's a form of power training, then when you get on the 110 PSI, you basically just fly.

I always ride 23s because I hate the bouncy effect of 25+ at high cadence. Using your legs as a suspension source is far more effective than trying to get that from higher/wider profile tyres on tarmac.

This is completely irrelevant, but....
Back in the day, we trained on tubulars (called, 'high pressures' at that time) with 80 PSI in them (no Strava then, so just that), then on race day we put our racing wheels on the bike with silicone beaded, tubeless tyres (called, 'singles' then) which were rated to handle 180 PSI (I kid you not, these were hand-made, locally stitched racing tyres and could handle immense pressure), however we only ran 120 PSI in them to err on the side of caution, and basically went BOOM on race day. The difference was tantamount to floating on air.
 

saibot

Maximum Pace
May 29, 2012
793
934
113
Taito
#12
@Cory M.

FYI, this is what I do...

I always keep a lower pressure in my tyres for training (90 PSI), then if I want to have a crack at a segment I run a fresh 110 PSI in the tyre. The training pressure creates a tyre drag, so it's a form of power training, then when you get on the 110 PSI, you basically just fly.
This is what they claim is scientifically been disproven though ;)
They don't really say if been through a proper peer review process however so would surprise me if there will pop up counterclaims.

I've been going wider and lower pressures during these last few years, now I'm never above 90psi. I'm not a hammer jockey so can't say if it's affecting my speed but is definitely helps with the comfort.
I took their advice and got som latex tubes as well, have yet to try it out though.
 
Last edited:
Likes: Heath

Chrisisism

Maximum Pace
Sep 6, 2014
112
107
73
43
Mejiro, Toshima-Ku, Tokyo
#14
@Cory M.

FYI, this is what I do...

I always keep a lower pressure in my tyres for training (90 PSI), then if I want to have a crack at a segment I run a fresh 110 PSI in the tyre. The training pressure creates a tyre drag, so it's a form of power training, then when you get on the 110 PSI, you basically just fly.

I always ride 23s because I hate the bouncy effect of 25+ at high cadence. Using your legs as a suspension source is far more effective than trying to get that from higher/wider profile tyres on tarmac.

This is completely irrelevant, but....
Back in the day, we trained on tubulars (called, 'high pressures' at that time) with 80 PSI in them (no Strava then, so just that), then on race day we put our racing wheels on the bike with silicone beaded, tubeless tyres (called, 'singles' then) which were rated to handle 180 PSI (I kid you not, these were hand-made, locally stitched racing tyres and could handle immense pressure), however we only ran 120 PSI in them to err on the side of caution, and basically went BOOM on race day. The difference was tantamount to floating on air.
It looks like @Heath has the potential to take even more KOMs
 
Likes: Heath
Mar 31, 2015
57
19
38
41
#15
FWIW after reading this thread I went out last night and this morning running 80/90 on 25mm tyres (I'd been running them at 90/100). I was surprised that it felt faster given how smooth the ride was and was pleasantly surprised to see a nice set of PBs on most of the climbs and a higher than usual average speed. Obviously there could be other reasons but I'm going to keep them lower (until I start getting slower again).
 
Likes: Cory M.

Heath

Maximum Pace
Dec 13, 2014
525
452
93
47
Kamagaya
www.nanairogakudo.com
#16
My theory on gaining speed through lower tyre pressure is that riders who use their tyres for suspension, and not their legs, should re-consider their pedalling technique.
Of course they will reap greater speeds by using bouncier tyres because their legs cannot deliver that same smoothness in the powerstroke.
Pedalling technique is very important.
Anyone who has ever done a lot of track racing will tell you that pedalling technique is everything, and that theory transitions to the road automatically.
 
#17
My theory on gaining speed through lower tyre pressure is that riders who use their tyres for suspension, and not their legs, should re-consider their pedalling technique.
Of course they will reap greater speeds by using bouncier tyres because their legs cannot deliver that same smoothness in the powerstroke.
Pedalling technique is very important.
Anyone who has ever done a lot of track racing will tell you that pedalling technique is everything, and that theory transitions to the road automatically.
Definitely a valid point from someone with your level of experience, @Heath .
But playing devil's advocate here, chances are that most of us don't and won't have that track experience or the dedication to develop really good pedaling technique. So if going with the right types of tires and pressure is a way to gain advantage and be comfortable despite mediocre technique, it seems like a pretty good option. Also, I'm assuming that Jan and the guys that did the testing do have pretty solid technique, although it's interesting that it didn't come up in the discussion of shock absorption.
 

Bruno BQ

Maximum Pace
Mar 9, 2015
149
26
58
32
#18
The smoothness seems a plus to the reduced pressure. The idea that the lower pressure adds a more constant contact allowing more force to be driven on the pavement seems very reasonable. Still, if you are on a very clean track, with a very smooth track line, this probably don't make that much sense, as there wouldn't be much to bounce of and lose track.

So if you are on very good track, would make a lot of sense to pump up, while on the commoners road a lower pressure makes probably makes more sense.
 

macrophotofly

Maximum Pace
Aug 27, 2012
581
234
73
London, UK
www.macrophotofly.com
#20
Deliberately ran my Conti 25mm Clinchers at 80 this last weekend (instead of my normal 90). Felt very good on both the flat/climbing and more importantly when descending. Got a couple of PB's so didn't seem to be affecting my times. Very comfortable and I'm using a non-padded seat so it is quite noticeable. I'm personally back down to 67kg so still plenty over the suggested pressure in that table, but probably won't drop below 80 to give me a safety margin if I ever went out and forgot to pump the tires before going.
 
Likes: Heath