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Discussion Starter · #1 ·
Wonder anyone can help me here. I have posted the same question 3 times to continental tires but they just could not bother to reply. Wonder what kind of service?

Here’s my question I posted to them:

I purchased 2 tyres GP4000s, 25c. Bike and me weigh 65kg. I searched your web and could not find a tire pressure chart.

Please advise what is the best pressure for the front and rear tire.

Thank you.
 

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Bianchi-Campagnolo
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At 65 kg you can go pretty low with 25mm. The Michelin chart suggests 6 Bar (87 psi) as a starting point, but I believe that's based on rider weight only, so 5.5 Bar is probably a better start value for your 65 kg equipage weight. You may try to run your front tire 0.2-0.3 Bar lower than the rear. Experiment and good luck!


Michelin Bicycle USA - A better way forward®
 

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Discussion Starter · #3 ·
At 65 kg you can go pretty low with 25mm. The Michelin chart suggests 6 Bar (87 psi) as a starting point, but I believe that's based on rider weight only, so 5.5 Bar is probably a better start value for your 65 kg equipage weight. You may try to run your front tire 0.2-0.3 Bar lower than the rear. Experiment and good luck!


Michelin Bicycle USA - A better way forward®
Tks for reply.

Question
1) Can we use another brand as a good guide. I not familiar with characteristic of tyres. Perhaps generally all the same
2) Chart only shows rider weight. How do i factor in including bike wt?
 

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Bianchi-Campagnolo
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1) Yes. As a guide it's fine.
2) Interesting question. Since I tend to run slightly lower pressures than Michelin's recommendations I thing "their" bike is heavier than mine. Use you weight and experiment over a few rides to find you tire pressure sweet spot.
 

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Have heard the following advice many times from many self appointed bicycle experts: " .. Pump the tires up to the maximum pressure shown on the tire's sidewall."
.
Not ... don't do that. don't tell folks that.

See advice in posts above and below; and spread that around.
 

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Discussion Starter · #6 ·
Have heard the following advice many times from many self appointed bicycle experts: " .. Pump the tires up to the maximum pressure shown on the tire's sidewall."
.
Not ... don't do that. don't tell folks that.
See advice in posts above and spread that around.
I understand pumping to max is flaw unless one is heavy weight. I'm not, so that's the reason i ask.

I still prefer some good establish figures showing pressure for rider and bike weight, rather than go for a few rides to experiment. That will waste alot of time and maybe have to factor in the mood. I'd put the fine adjustment part as last after having pump to some good guidance.
 

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I still prefer some good establish figures showing pressure for rider and bike weight, rather than go for a few rides to experiment
While "established figures" are comforting, they can't really do much for you if you ride on varied road surfaces. For example, pressure that's perfect for smooth tarmac is too high for rougher, chip-sealed roads. And if the surfaces are varied, you need to compromise a bit. Tire brands and -models also vary in their response to a set pressure, so there's another uncertainty. In short: for fine-tuning your pressures, the best tire gauges are your thumb, your butt and your hands.

Not sure I would consider experimenting a waste of time. If I had to do all my rides without experimenting, I would fall asleep from boredom and fall off my bike. :)
 

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Your 65kg is 143 lbs.
I'm about 191, bike and rider, that's 87 kg. (google "65 kg in lbs") That's bike & etc about 19 lbs? and rider about 172 lbs.


I use 100-105 psi in the rear, which is 6.8-7.2 bar,
85-90 psi in the front, 5.9 to 6.2 bar.
And both pressures could go a little lower.

You are about 75% of my weight, but I don't think you can just drop the pressure by 25%. Maybe try 90-95 rear (6.2 to 6.6 bar) and 77-82 psi front (5.3 to 5.7 bar)

For me, if the pressure is too low, the steering feels a little vague, (and there's more risk of pinch flats) If the pressure is too high, the tires don't soak up the rough roads. My preferred range gives me a smooth but responsive ride.

I really like the 25c tires. They do seem better on rough roads, and aren't any slower than the 23c GP4000 tires I used before. I was using 105-110 rear, and 90-95 front.

The 90 front and 105 rear makes my 25c tires harder than my usual 23c tires were, yet they still soak up the rough roads.
 

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Discussion Starter · #9 ·
Your 65kg is 143 lbs. I'm about 191, bike and rider, that's 87 kg. (google "65 kg in lbs") Bike & etc about 19 lbs? and rider about 172 lbs.


I use 100-105 psi in the rear, or 6.8-7.2 bar,
85-90 psi in the front, 5.9 to 6.2 bar.
And both pressures could go a little lower.

You are about 75% of my weight, but I don't think you can just drop the pressure by 25%. Maybe try 90-95 rear (6.2 to 6.6 bar) and 77-82 psi front (5.3 to 5.7 bar)

For me, if the pressure is too low, the steering feels a little vague, (and there's more risk of pinch flats) If the pressure is too high, the tires don't soak up the rough roads. My preferred range gives a smooth but responsive ride.

I really like the 25c tires. They do seem better on rough roads, and aren't any slower than the 23c GP4000 tires I used before. I was using 105-110 rear, and 90-95 front.

The 90 front and 105 rear makes my 25c tires harder than my usual 23c tires were, yet they still soak up the rough roads.
Tks for advise.

I change from 23c to 25c after reading many articles that 25c reduces rolling resistance. Now I begin to wonder if the pressure is so low, will I actually benefit from using 25c.

According to chart, the optimum is abt 63 psi. That is quite below your advise and way below the general consensus here of 95 to 100psi.

Your thoughts?

http://www.bccclub.org/documents/Tireinflation.pdf
 

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I change from 23c to 25c after reading many articles that 25c reduces rolling resistance.
Only if you pump up the 25s to the exact same pressure you used in the 23s. Many articles don't mention that because the fact that fatter tires have more rolling resistance at proper pressures isn't very newsworthy. But it doesn't really matter: you're overthinking all this vastly. Go with some chart and fine-tune according to your feel. You'll be a better rider for it.
 

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Only if you pump up the 25s to the exact same pressure you used in the 23s. Many articles don't mention that because the fact that fatter tires have more rolling resistance at proper pressures isn't very newsworthy. But it doesn't really matter: you're overthinking all this vastly. Go with some chart and fine-tune according to your feel. You'll be a better rider for it.
I agree completely with Wim. This is not the exact science you may think it is. How it "feels" is very much a legitimate part of the process.

With your quite light weight and 25mm tires, I'd start with something like 80 front, 85 rear. See how it feels. Pay attention particularly to how secure you feel in high-speed aggressive turns, how smooth it feels on bumpy pavement, and whether you feel sluggish when accelerating, or putting on the power on long straights, or climbing out of the saddle.

If it feels good, try a little lower, and then a little higher, and go with what feels best.

Have fun.
 
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