Thorn Cycles Forum

Community => Thorn General => Topic started by: ZeroBike on January 11, 2013, 11:21:35 AM

Title: Whats the tyre pressure for a sherpa?
Post by: ZeroBike on January 11, 2013, 11:21:35 AM

Im running Schwalbe Marathon Supremea (26 x 1.6) on Rigida Grizzly Rims.

Whats the correct tyre pressure for laden and also unladen rides?

The only info I can find is from the Schwalbe site that says its between 50-85 psi.

http://www.schwalbe.com/gbl/en/produkte/tour_city/produkt/index.php5?flash=1&ID_Produktgruppe=36&ID_Produkt=131&ID_Land=38&ID_Sprache=2&ID_Einsatzbereich=9&tn_mainPoint=Produkte&tn_subPoint=Tour/City

Also are front and rear different?

Best wishes

Title: Re: Whats the tyre pressure for a sherpa?
Post by: jags on January 11, 2013, 11:36:59 AM

well i have 70psi  in mine  find that to be perfect for all my riding. ;)

Title: Re: Whats the tyre pressure for a sherpa?
Post by: geocycle on January 11, 2013, 01:12:33 PM

I have the same tyres on my raven tour which is similar to the sherpa.  I run 60 psi at the front and 70 psi at the back.  I use 80 psi at the back when touring.

Title: Re: Whats the tyre pressure for a sherpa?
Post by: JimK on January 11, 2013, 01:15:39 PM

http://www.schwalbe.com/gbl/en/technik_info/luftdruck/?gesamt=74&ID_Land=38&ID_Sprache=2&ID_Seite=136&tn_mainPoint=Technik (http://www.schwalbe.com/gbl/en/technik_info/luftdruck/?gesamt=74&ID_Land=38&ID_Sprache=2&ID_Seite=136&tn_mainPoint=Technik)

I came up with some formulas a while back to fit the Schwalbe recommendations. My formula says for a 42 mm width tire and 165 pound rider & I think I guessed a 25 pound bike that 48 psi would be about right. That's be about 50 psi in the rear and 45 psi in front.

Scale up proportionally as the total weight changes from 190 pounds. My chart tells me 56 psi with my extra weight.

Title: Re: Whats the tyre pressure for a sherpa?
Post by: JimK on January 11, 2013, 01:37:06 PM

Here is the graph of my formula vs Schwalbe - you can see that my nice curve is lower than their chart in the 40-50 mm range. Not like this in any kind of precise science anyway! Lower pressure will give a smoother ride on rough pavement but then you don't want to bottom out either so really it gets beyond precise calculation.

http://www.thorncycles.co.uk/forums/index.php?topic=3798.msg16658#msg16658 (http://www.thorncycles.co.uk/forums/index.php?topic=3798.msg16658#msg16658)

Title: Re: Whats the tyre pressure for a sherpa?
Post by: Dave Whittle Thorn Workshop on January 11, 2013, 02:22:11 PM

Dont forget rim manufacturers have tyre pressure limits too.

Title: Re: Whats the tyre pressure for a sherpa?
Post by: triaesthete on January 11, 2013, 02:59:25 PM

Hi Zero
I run these tyres on these rims and I weigh 78kg.

About 40 psi front and 45 psi rear gives a super cushy, creamy smooth ride and no bottoming out so far. Bike still pics up spped dpwn hills really well so rolling resistance is not high either.

I couldn't think of a reason to go above 55psi. If you were going to lose all the comfort by using high pressures I think it would make more sense to run a 700c bike with 25 or 28mm tyres like everyone else does when speed/weight are more important than comfort/mileage/economy/strength.

The Bicycle quarterly blog has some good info on tyre pressures for given sizes and wheel loads.

Have fun
Ian

Title: Re: Whats the tyre pressure for a sherpa?
Post by: ZeroBike on January 11, 2013, 04:52:45 PM

Thanks guys.

I have always used the thumb test in the past, but treated myself to a nice new pump with a pressure gauge... and then realised I have no idea what pressure to use!

http://www.bikeradar.com/gear/category/tools/cycling-tools/mini-pump/product/review-topeak-turbo-morph-10-37556

BTW its a really nice pump!

Title: Re: Whats the tyre pressure for a sherpa?
Post by: Andybg on January 11, 2013, 05:32:24 PM

Yeah  I have the same pump and am really happy with it too.

Andy