Winter Tyres on a RST - don't seem to fit

[CWM]

With a hard frost forecast for Monday morning (in northern Scotland at least),  I elected to spend Sunday evening putting the winter tyres on my commuting bike, a RST. I went for the front one first.  Whilst I do have a spare set of 26" wheels, I still needed to change the tyres as I wanted to keep using the dynamo hub (and indeed the rohloff!). I went for the front one first, wrestled the winter tyre off the spare wheel and onto the RST's front wheel.  Then discovered that with the winter tyre on the wheel would not fit back on.  Simply not enough room under the crown of the fork. 

The tyre is a Continental Topcontact Winter 26 x 1.9, the mudguard is an SKS which I think is 50mm wide, and it is installed hard up against the underside of the crown (ie no spacers between the mudguard and the underside of the fork). What confuses me is that last year I ran these tyres on a Sherpa with no trouble at all, and on the Sherpa the mudguard sits a little bit lower.  All I can think of is that the Sherpa is a short top tube and the RST is a long top tube (both about 560 frame size) and that there is a different rake on the forks between long and short tt frames and this would affect the amount of clearance.

Any thoughts appreciated.  I am assuming that the choice of rims does not make a great deal of difference, but for the record to RST rims are Sun CR18. and my usual tyres are Schwalbe Marathon Racers.

Many thanks

Clive

[martinf]

With a hard frost forecast for Monday morning (in northern Scotland at least),  I elected to spend Sunday evening putting the winter tyres on my commuting bike, a RST. I went for the front one first.  Whilst I do have a spare set of 26" wheels, I still needed to change the tyres as I wanted to keep using the dynamo hub (and indeed the rohloff!). I went for the front one first, wrestled the winter tyre off the spare wheel and onto the RST's front wheel.  Then discovered that with the winter tyre on the wheel would not fit back on.  Simply not enough room under the crown of the fork. 

I think the max tyre size on an RST with muguards and reasonable clearances is about 1.6".

Which is one of the reasons why I chose a Raven Tour frame and not the lighter RST frame for my utility bike. I have 1.95" winter tyres and they fit easily on the Raven Tour with the (widest) P65 mudguards.

[CWM]

Thanks Martin. Believe it or not I never even gave that a thought when I bought the bike (second hand, so not perhaps as long considered a purchase as if one had bought it new full price and discussed all the variables and options). I'm thrilled with the bike and so that's all fine, but just a little bemused that I never considered this issue.  Which is in fact a bit of an issue as I commute on rural roads all year round and so will occasionally crack out the winter tyres if a frosty spell is forecast. I think I just assumed that it was really the same bike as the Sherpa only set up for the Rohloff.  Well you learn something every day.

Anyone got any tips for winter tyres that fit a RST?!

In the meantime panic over for this week anyway as temperature back up again.  I was down for a meeting at Loch Morlich in the Cairngorms today. Car showed 11 degrees. That's pretty warm and doesn't suggest we will be skiing any time soon. 

[martinf]

Anyone got any tips for winter tyres that fit a RST?!

Not much help, but the thinnest studded tyres I know about in 559/26" rim size are 47x559 = 1.75x26 inch (Winter and Marathon Winter from Schwalbe).

These are probably a bit too big for use on an RST with mudguards fitted.

In my opinion, slightly more clearance is needed for studded tyres compared with the same dimension without studs. On my former utility bike the first time I used 1.95" Nokians they would catch on the mudguards, which were set up for 2.0 semi-slick tyres. Luckily I had enough room in that frame to adjust the P65 mudguards to get sufficient clearance.