# PSI Question



## wiputi82 (Jun 27, 2016)

I have this bike:









Is a Norco Search A105. Which came with Schwalbe Tyrago tyres with a minimum of 35psi and max of 65psi. I put it at 65psi and it was too bumpy for my liking on dirt. I will need to reduce it but I ride about 15-20km of roads to get to the dirt trails and am worried that the lower pressures would drag on the road. Do you think I will be alright on the roads with a lower pressure?


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## PJ352 (Dec 5, 2007)

Use the second chart (Weight of (Fully-dressed) Rider & Bike) as a starting point, tailoring pressures from there.

Bicycle tire pressure calculator


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## JCavilia (Sep 12, 2005)

wiputi82 said:


> I am worried that the lower pressures would drag on the road. Do you think I will be alright on the roads with a lower pressure?


Yeah, you'll be alright. It might feel a little sluggish, but maybe not. It won't hurt anything. You can experiment and find a compromise that works for you.


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## Migen21 (Oct 28, 2014)

I own the carbon version of that bike.

You just need to experiment. I'm 6' 5", 235lbs and running 32mm Clement X'Plor USH at about 50f/55r for gravel/dirt. 

Your own weight, propensity for pinch flats, the terrain you ride on, the wheels/tires, etc.. will all factor in. 

You rode it at 65. I'd start by dropping it by 10psi and see how it feels.

Another thing to consider. How harsh the ride feels is determined in part by the tires casing. I'm not familiar with the Tyrago, and how firm that casing is, but a good quality high TPI tire is going to have a softer feel than a harder casing tire (typically flat resistant commuter tires). 

Even better, a nice tubeless set up will make a big difference in how it feels too, although tubeless tires for mixed gravel/asphalt are not terribly easy to find, and not cheap.


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## wiputi82 (Jun 27, 2016)

Thanks for the replies.



Migen21 said:


> I own the carbon version of that bike.
> 
> You just need to experiment. I'm 6' 5", 235lbs and running 32mm Clement X'Plor USH at about 50f/55r for gravel/dirt.
> 
> ...


Appreciate the info. Out of curiosity, have you ever put 28mm road tyres on the bike for pure road riding? Are the rims able to handle the higher pressures of the road tyres?


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## PJ352 (Dec 5, 2007)

wiputi82 said:


> Out of curiosity, have you ever put 28mm road tyres on the bike for pure road riding? Are the rims able to handle the higher pressures of the road tyres?


Not answering for Migen21 on your specific question, but PSI recommendations aren't based on rims, they're based on bike/ rider weight and tire widths. 

If your bike came with 35c tires, it's very likely the rims will accommodate 28c's - dictated by internal rim width, which is easily measured. 

Here's a link you may find helpful, but use it as a guide because (as stated in the text) "Many cyclists exceed the recommended widths with no problem":

Tire Sizing Systems


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## 4Crawler (Jul 13, 2011)

I would just drop the pressure and give it a ride on pavement and see what it feels like to you. I ran some Schwalbe Marathon Mondial tires (700x40) on my cross bike. They list 50-85 psi, I think I started around 65 and dropped to 50, 45, then 40 until the ride was decent. Then I set them up tubeless and now run them around 30psi and they are great on pavement and in the dirt. I've got over 5K miles on them w/ no issues aside from one nail that went in the tread and out by the bead and wouldn't seal up. They are maybe 2MPH slower than my road bike w/ 700x28 Marathon Supremes on flat, smooth pavement. But the ride comfort and durability more than makes up for the slightly slower speed. I don't really notice them being slower, only if I ride the same section of pavement on both my cross and road bikes and note the MPH reading do I see any change.


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## Migen21 (Oct 28, 2014)

wiputi82 said:


> Thanks for the replies.
> 
> 
> 
> Appreciate the info. Out of curiosity, have you ever put 28mm road tyres on the bike for pure road riding? Are the rims able to handle the higher pressures of the road tyres?


I'm not running stock wheels, and I'm not sure which rims your bike came with, but I'm sure they'll run 28's just fine. And you could certainly put 28's on it and still ride it on gravel or road just fine. I do it all the time on my *other* bike. It's not going to be suitable for really rough, rocky terrain, or deep, loose gravel, but for the average railtrail, dirt road, 28's are fine in most cases.

And don't get too caught up in running max pressure. Regardless of what tires you run, just run them as low pressure as you feel comfortable that you won't pinch flat. Lower pressure is better than higher pressure in almost every possible way. Handling (especially in less than ideal conditions like rough pavement, sandy/gritty road, dirt/gravel paths, etc...), it's more comfortable, just as fast in most conditions, and faster in some. 

That is a great bike. Let some air out of the tires and go have some fun. 

I'm riding mine up the John Wayne Trail to the Snoqualmie Tunnel (again) tomorrow. 

Here's some inspiration!


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## wiputi82 (Jun 27, 2016)

PJ352 said:


> Not answering for Migen21 on your specific question, but PSI recommendations aren't based on rims, they're based on bike/ rider weight and tire widths.
> 
> If your bike came with 35c tires, it's very likely the rims will accommodate 28c's - dictated by internal rim width, which is easily measured.
> 
> ...



Thanks. Makes sense. I was reading an article and the writer said you should know what you're rims are rated at because high pressures can cause the rim flange to flare outwards. I couldn't find any rating on the rims though which is why I asked.


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## wiputi82 (Jun 27, 2016)

4Crawler said:


> I would just drop the pressure and give it a ride on pavement and see what it feels like to you. I ran some Schwalbe Marathon Mondial tires (700x40) on my cross bike. They list 50-85 psi, I think I started around 65 and dropped to 50, 45, then 40 until the ride was decent. Then I set them up tubeless and now run them around 30psi and they are great on pavement and in the dirt. I've got over 5K miles on them w/ no issues aside from one nail that went in the tread and out by the bead and wouldn't seal up. They are maybe 2MPH slower than my road bike w/ 700x28 Marathon Supremes on flat, smooth pavement. But the ride comfort and durability more than makes up for the slightly slower speed, I don't really notice them being slower.


Thanks for the advice. I wish the shop had told me that. They just said run them at 75-90psi when the tyre max was 65!


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## wiputi82 (Jun 27, 2016)

Migen21 said:


> I'm not running stock wheels, and I'm not sure which rims your bike came with, but I'm sure they'll run 28's just fine. And you could certainly put 28's on it and still ride it on gravel or road just fine. I do it all the time on my *other* bike. It's not going to be suitable for really rough, rocky terrain, or deep, loose gravel, but for the average railtrail, dirt road, 28's are fine in most cases.
> 
> And don't get too caught up in running max pressure. Regardless of what tires you run, just run them as low pressure as you feel comfortable that you won't pinch flat. Lower pressure is better than higher pressure in almost every possible way. Handling (especially in less than ideal conditions like rough pavement, sandy/gritty road, dirt/gravel paths, etc...), it's more comfortable, just as fast in most conditions, and faster in some.
> 
> ...


Looks like an amazing ride! 

My rims are: Double Wall Aero 28mm - Black

I'll be putting the 28's on because I'll want to do some rides soon on only road. 

thanks for the advice


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## Lombard (May 8, 2014)

PJ352 said:


> If your bike came with 35c tires, it's very likely the rims will accommodate 28c's - dictated by internal rim width, which is easily measured.
> 
> Here's a link you may find helpful, but use it as a guide because (as stated in the text) "Many cyclists exceed the recommended widths with no problem":
> 
> Tire Sizing Systems


These are the older guidelines. Newer guidelines can be found here:

https://www.dtswiss.com/Resources/Tech-PDF/Tire_Pressure_Dimension


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## PJ352 (Dec 5, 2007)

Lombard said:


> These are the older guidelines. Newer guidelines can be found here:
> 
> https://www.dtswiss.com/Resources/Tech-PDF/Tire_Pressure_Dimension


Seriously? And in regard to the OP's question, _how_ is 'new' somehow better than 'old' when we're talking basic laws of physics? 

You're literally the first person I know to disregard Sheldon Brown's (RIP) recommendations.


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## Lombard (May 8, 2014)

PJ352 said:


> You're literally the first person I know to disregard Sheldon Brown's (RIP) recommendations.


Not quite. Remember, he did say "Note: This chart may err a bit on the side of caution. Many cyclists exceed the recommended widths with no problem."

And these are the ETRTO guidelines and were not created by Sheldon Brown - who BTW, I have a lot of respect for. If you do a thread search, awhile back, there was a poster who warned alarmingly about exceeding the ETRTO limits. He was reprimanded repeatedly by some very reputable members here about this. You may want to read up on this:

http://forums.roadbikereview.com/wheels-tires/tires-fit-622x18-wheel-175604.html


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## PJ352 (Dec 5, 2007)

Lombard said:


> Not quite. Remember, he did say "Note: This chart may err a bit on the side of caution. Many cyclists exceed the recommended widths with no problem."
> 
> And these are the ETRTO guidelines and were not created by Sheldon Brown - who BTW, I have a lot of respect for. If you do a thread search, awhile back, there was a poster who warned alarmingly about exceeding the ETRTO limits. He was reprimanded repeatedly by some very reputable members here about this. You may want to read up on this:
> 
> http://forums.roadbikereview.com/wheels-tires/tires-fit-622x18-wheel-175604.html


The chart was provided to Sheldon Brown, but by posting it, he endorsed it, then added the footnote "This chart may err a bit on the side of caution. Many cyclists exceed the recommended widths with no problem." 

Your addition with the DT Swiss chart (IMO) brushed aside an 'older' guideline for a 'newer' one. Implication, DT Swiss guidelines were somehow superior? 

As I said previously, this isn't a 'new' versus 'old' issue. It's a law of physics issue. All DT Swiss did was err less on the side of caution, But Sheldon's footnote covered that.

As far as any alarmist warnings of exceeding ETRTO limits, Sheldon's text covers that - paraphrasing, it depends on by how much. DT Swiss does not include such info. 

The OP's question is a good one, and IMO Migen21's first hand experiences have answered his question.


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