Who rides 28mm + tires on tarmac?

Discuss light weight issues concerning road bikes & parts.
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mpulsiv
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by mpulsiv

To put this into perspective, it takes 30 strokes on standard pump to inflate 25mm tire to ~ 82 psi. In contrast, same 30 strokes inflate 28mm tire to ~65 psi. This is why I bring up the fact of over inflation because it all about volume.
Last edited by mpulsiv on Mon Oct 01, 2018 2:02 am, edited 2 times in total.
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bm0p700f
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by bm0p700f

Well the MTB ride was on 29*2.0" dugast tubular at 20psi and 20mph average with work on the front. It was hard d work.

by Weenie


zefs
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by zefs

Mr.Gib wrote:
Sun Sep 30, 2018 7:22 pm
zefs wrote:
Sun Sep 30, 2018 5:59 pm
Better handling and cornering speed making you faster does not mean wider tires are faster on straight road. How many times do you corner fast compared to going straight on the course of a ride? Also how many times do you hit cobble like sections which is were wider tires with lower pressures are faster?
This is assumed, and if you are racing this matters. Of course where you are racing is a factor as well. And don't forget all these big tires and rim add weight.

But still, it would be nice to get closer to the right answer to the question: if you are not racing, then what tire/rim choice is best?
If you are not racing and need extra comfort, why not use less psi on your current tires but you need to switch to wider tires and rims?
"Because they are faster"... but you are not racing :noidea:

If you enjoy wider tires and rims then use them and stop caring about avg speed on your rides.
But it's illogical to think a wide tire at 60psi is faster than a narrower tire at let's say 80-100 psi on normal roads.
Volume of air might be similar but contact patch and weight changes, affecting rolling resistance and aerodynamics if the setup is not optimal.
Last edited by zefs on Mon Oct 01, 2018 8:01 am, edited 1 time in total.

bm0p700f
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by bm0p700f

That depends on your normal roads. Your statement makes assumptions

zefs
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by zefs

Any tarmac pretty much. If you hit 10 potholes along a 10km course then sure you should use wider tires and less air pressure.
Also, the silca test does not mention what speeds the rider was going. A 10watt loss over 900m is significant for a long ride.

nachetetm
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Joined: Fri Aug 18, 2017 8:54 pm

by nachetetm

zefs wrote:Any tarmac pretty much. If you hit 10 potholes along a 10km course then sure you should use wider tires and less air pressure.
As people mentioned, you can't make assumptions just with your experience. The word is full with pretty rough tarmac, if you never rode it you will never understand it. It's not about the potholes. I'm with many of the people above, wide tires on wide rims give and advantage in handling and are as fast at much lower pressure. This is for non-competitive purposes, I can understand in competition on a very well paved road you can benefit from narrower tires to improve aero at high speeds, but the people that ride in those conditions are a minority. Experimenting with tire width and pressure is good, but no one can pretend that what work for himself is the "gold standard".

zefs
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by zefs

I am not making assumptions, the tarmac here is possibly the worst in Europe and still, I found 28mm tires (which measure 31mm on modern rims) to be slower in every way (uphill even more so). The only benefit was comfort and handling which is great if you are after that, but I belive most people want them to be faster too since they care about numbers/avg speed. Again, why not use lower pressures on your current tires, since most people are over-inflating?

The topic starter asked about how they feel on tarmac and how aero they are.

jlok
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Joined: Tue Jun 30, 2015 3:30 am

by jlok

zefs wrote:
Mon Oct 01, 2018 7:54 am
Mr.Gib wrote:
Sun Sep 30, 2018 7:22 pm
zefs wrote:
Sun Sep 30, 2018 5:59 pm
Better handling and cornering speed making you faster does not mean wider tires are faster on straight road. How many times do you corner fast compared to going straight on the course of a ride? Also how many times do you hit cobble like sections which is were wider tires with lower pressures are faster?
This is assumed, and if you are racing this matters. Of course where you are racing is a factor as well. And don't forget all these big tires and rim add weight.

But still, it would be nice to get closer to the right answer to the question: if you are not racing, then what tire/rim choice is best?
If you are not racing and need extra comfort, why not use less psi on your current tires but you need to switch to wider tires and rims?
"Because they are faster"... but you are not racing :noidea:

If you enjoy wider tires and rims then use them and stop caring about avg speed on your rides.
But it's illogical to think a wide tire at 60psi is faster than a narrower tire at let's say 80-100 psi on normal roads.
Volume of air might be similar but contact patch and weight changes, affecting rolling resistance and aerodynamics if the setup is not optimal.
Low pressure on narrow rim and bulb like tire shape will have tire squirm feel. That's why if you go low pressure it should be of wider tire to have enough volume, plus wider rims to maintain the inflated tire shape.
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zefs
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by zefs

Yes, if you are talking about old narrow rims and tires. There is an optimal for tarmac and to me that is not 31mm measured tire and 60psi, speed wise. I am focusing on speed because the topic starter mentioned aero benefits.

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wheelsONfire
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by wheelsONfire

How about break point for puncture (risk) increase and sidewall deformation?
I ride tubulars, i hate punctures (dah - who doesn't)....
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zefs
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by zefs

Another issue with them, since contact patch increases (more tire wear too, how significant I don't know) also if something punctures the 25mm version it will puncture the 28mm one as well. But, modern rims usually come tubeless ready which would be a better choice if you plan to go for a wider setup.

Marin
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by Marin

themidge wrote:
Sat Sep 29, 2018 4:14 pm
There was someone on this morning's group ride on a cool looking steel 'randonneur' style bike (metal mudguards, shiny bits, etc, it was pretty cool). He was on what must have been at least 35mm tyres, maybe 40mm, and seemed to get on okay. Our roads are quite bumpy (surface changes a lot, lots of repairs etc, and properly smooth tarmac is rare) so maybe if it had been smoother then he would have struggled because of the extra Crr.
If he was on 42mm Panaracer Pari-Motos, these tires are about as fast as GP4000s (in my tests) so he'll just have a small aero penalty. If he had a decent position on the bike, he'll be just as fast as the other riders.

Marin
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by Marin

My standard go-to tire is now a 32mm Panaracer-made tire ran tubeless.

I apprechiate the ride comfort, but even more I like the option to sitch a ride over to gravel roads when car traffic becomes too annoying.

The tires (Fairweather Traveler) roll very well, and I think the penalty over road-only tires is minimal. I also have no problems hanging with fast group rides over rolling terrain on this setup, or even on Compass 35mm tires.

Mr.Gib
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by Mr.Gib

bm0p700f wrote:
Mon Oct 01, 2018 8:00 am
That depends on your normal roads. Your statement makes assumptions
This is my point exactly. There just isn't adequate data from real world applications.

What is better for 100 km - 200 km with a mix of surfaces from new tarmac, old tarmac, cracked tarmac, smooth chipseal, and rough chipseal, on rolling terrain at 30 km/h average? I just throw out this scenario because it's what I do 4-5 days per week. And everyone will have their own situation.

I use the term "better" intentionally. Cycling equates better with faster while using the least energy and I don't dispute this. But I can't help but think that the specific application might mean that 30 - 32 mm at 60 psi is "better" then 25 mm at 90 psi.

Again, if one is not racing, and riding long distances on less then perfect surfaces, it just may be that the bigger, softer, "slower" tire choice is better. I face my own torture test next Spring (2000 km and 50,000 meters in 10 days) and I am trying to guess what is the cumulative impact on the body of road vibration vs the expenditure of slightly more watts? I am afraid no test will ever tell us this.
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zefs
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Joined: Sat Aug 05, 2017 8:40 pm

by zefs

As I said from my tests, on that kind of surfaces the narrower tire at high psi will be faster. The wider tire and low pressure will be faster on surfaces that make your bike shake basically, cobbles, gravel etc.
Simple road vibration does not make you loose speed, despite the wider tires muting that effect.

In the end, you can do your own testing to see what's optimal just use the same volume of air e.g 80 psi 25mm tire vs 60psi 28mm tire.

by Weenie


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