Could the retro-crowd be right all along? Rim Width.....so which is it?

xtaffa

Dirt Disciple
2.1 on 19mm rims here at nice low pressures, rigid bike on woody xc, handles great with tons of grip and cushioning; tried a 2.35 Hans Dampf up front recently and was a bit squirmy on the 19s so tried a 23mm and was fine -although now keeping for rockier riding as prefer the feel of the 2.1s I've got.
 

doctor-bond

Feature Bike
I find if i go to low on pressure, even on fat rims, the vagueness of the steering ( especially under heavy cornering) as the tyre moves about, is more disconcerting and slows me more than the possible wash out risk.

My pet thoeory is that a slightly harder tyre digs in more than a lower pressure tyre that moves about under the rim. Yes a flattie might get a touch more grip, but at the loss of control. Oh, and I dont get pinch flats too often!

But i assume it also depends what you ride on. We dont have slimy rocks, just sandy forest and hard pack clay lanes.

Pretty much this: I‘m using 2.25s on AT18s with enough pressure not to be squirmy and they go fine in mixed conditions (but then again I’m a middle aged bloke who knows his limits riding an old rigid bike that has plenty of limits).
 

FluffyChicken

Archivist
Retrobike Rider
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I run 2.25 on Araya 395 (15mm IRD), Mavic 231CD (I think 17MM as the 23 is external), Mavic XC717 (17mm) and all are fine, only one of the Schwalbe's, the lighter fast one Ron? doesn't like going down below 30PSI and you could feel it move over the tyre at the front.
Pretty much run at ~35PSI on my pump, may add a bit more now I weight a bit more. Don't forget laden weight plays a factor too.


Don't have a Campag Atek rim (14mm the narrowest they made) to try it on though.
 

M-Power

Old School Grand Master
‘rut anxiety’ great term 🙇🏻‍♂️ A proper retro test is being trapped in a high wall dried rut at nearly 50mph on the SDW. Do you feel lucky today punk vibes always sprung to mind 😂 Trying to look far enough ahead to bunny hop that huge tyre destroying rock or to jump lanes. Thats when you need trust in your bike and your mates
 

2manyoranges

Senior Retro Guru
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MPower spot on....it's the SDW I had specifically in mind. Like the ruts down to Kingston from the SDW at the top. Nightmare. Suddenly the correct rut becomes the wrong one...and gets deeper and deeper and has more and more flints in it.....RA (rut anxiety) factor 11.

And those that get SO deep that it's a genuine possibility that BOTH pedals will hang up - aaaaargh
 

M-Power

Old School Grand Master
MPower spot on....it's the SDW I had specifically in mind. Like the ruts down to Kingston from the SDW at the top. Nightmare. Suddenly the correct rut becomes the wrong one...and gets deeper and deeper and has more and more flints in it.....RA (rut anxiety) factor 11.

And those that get SO deep that it's a genuine possibility that BOTH pedals will hang up - aaaaargh
Amen. Not riden SDW in many years alas but that section still gives me the heebeejeebies just thinking about it 🤪 Thankfully I never came off but usually someone always did on early full sus usually 🤔 and it could be a long group walk with a beaten up rider and broken bike 😬
 

GrahamJohnWallace

Retrobike Rider
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Geoff Apps of Cleland fame runs wide tyre on narrow rims at low pressure and swears they are great off road. This is contrary to the idea of wide tyres on wide rims for off road but Geoff has been riding off road longer than any of us so maybe he has a point. Read his blog its interesting.
I own six 1980's 'Cleland style' bikes including:
*Three made by Cleland (26mm rims & 47mm or 54mm wide tyres)
*One made by Cleland and later upgraded by Highpath (22mm rims & 54mm wide tyres)
*One made by Highpath (22mm rims & 54mm wide tyres)
*One made by Jeremy Torr's company - English Cycles (30mm rims and 26.125" tyres.

The Highpath bikes are the most agile and the English Cycles' bike the least.

Geoff Apps' choice of narrow rims/wide tyre combinations came from his motorbike trials background were this was and remains the norm.
On a bicycle, the lateral stability of a wide tyre is dependent on the characteristics of the chosen tyre; the width of the inner-tube, and the tyre pressure. The idea is that instead of ricocheting off obstacles, a tyre on a narrow rim is more likely to snake around them. This means that you can ride over house-bricks etc and still have total control over the bike's steering and balance. Though not so good for doing 'tail-slides' etc.

So that all of the air pressure supports the tyres wall, it is important that the uninflated width of the inner-tube is the same as that of the tyre.

Apps also uses low tyre pressures (around 5 to 20 psi). It is therefore important to frequently monitor the pressures. If they drop too low the tyre wall will not be supported enough and the tyre will become laterally unstable.
 
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