Regular readers will know that I have had had a rather variable relationship with the Birdy, and in particular I have never been entirely happy with the tyres available in this particular size - 355, or 18 inches. The original tyres were rated at quite a low pressure, which resulted in increased rolling resistance compared with the bikes I am used to, and the subsequent high pressure tyre, although better, was still not good in this respect, and furthermore it gained a reputation for very short life. I tried a Vredestein San Marco in this size, and found it a distinct improvement despite the low pressure rating, but it still did not fully satisfy my expectations. The most recent tyre to carry the Birdy name was something of a disappointment - a robust design offering good life and puncture resistance, and reasonable grip (though I found it poor on damp grass), but with no improvement in rolling resistance - indeed, not as good as the Vredestein. Part of the explanation for the relatively high rolling resistance may lie in the fact that all these tyres were 38mm (1.5inches) wide, whereas most high-performance road tyres as used on other folders are no more than 1 3/8 inches wide. Of course, the extra size and tread may well have benefits in life, puncture resistance and performance off road, but I was not happy about compromising the on-road ride quality for these possible benefits.
Now at last there is a tyre which, at least on paper, seemed likely to fully meet my needs - the Schwalbe Stelvio. It is also available in the 406, 20 inch, size, and reports received from a variety of sources suggested that it has very low rolling resistance - even lower in the 406 form that the Continental Grand Prix, which was generally considered to offer the lowest rolling resistance on the road of any tyre in this size. The Stelvio differs from the other Birdy tyres in being only 28mm wide (1 1/8 inch), and is rated up to 120psi. Tread pattern is minimal, though slightly more than on the Primo Comet, and perhaps more too than the Continental GP (neither of which is of course available in 18 inch form). The central part of the tread is fairly wide, and doubles as a central rib on which most of the running will be done, with a smooth roll off onto the lightly treaded section beyond this.
Fitting the new tyres proved something of a nightmare, as is so often the case with the Birdy. I can only conclude that the rim diameter of the Birdy wheels varies, as I have found considerable variations in how easily the same tyres go on depending which rim they are being fitted to. On my previous Birdy the one rim in particular seemed if anything rather undersize, resulting in the newer Birdy tyre blowing off the rim shortly after fitting. On the current Birdy I have, the back rim seems about right, and tyres require a fair amount of effort to fit and remove, but not excessive. The front rim is a different matter, as I had already found when fitting Schwalbe Marathon tyres a few months ago. This experience resulted in me packing some stronger tyre levers in my saddlebag, to give me a better chance of dealing with a puncture while on the road. Fitting the front Stelvio proved even more difficult, and my tool kit has been further revised, though I doubt my ability to get a tyre off and on again by the road in really cold weather.
Once fitted, the tyres seated nicely on the rims, and I inflated them to something over 100psi - my two pressure gauges disagree alarmingly over the pressure I actually achieved, one showing 120 psi and the other only just 100.
There is one other adjustment you need to make at this point, but it is easy to forget: you will soon be made aware of it the first time you fold the bike! When folded, the front wheel is held in place by the head of a domed bolt on the inside of the front forks which presses against the side of the tyre; the Stelvios are so much narrower than any of the other tyres that you will need to unscrew the bolt a considerable distance to enable it to do its job - don't forget to tighten the locknut after doing this.
The acid test is of course the performance of the tyres on the road, and the Origami Ride at Cheltenham was my first opportunity to try them. I had not ridden the Birdy on its previous tyres (Schwalbe Marathons) for some while, which makes comparisons difficult, but subjectively the bike did seem to roll more freely, although on the other hand the stability seemed slightly impaired - it felt slightly more twitchy, at least at low-medium speeds. Tackling moderate hills, I seemed to be able to get up in one gear higher than I would have expected. That is partly down to the fact that the Stelvios are also slightly smaller diameter than the previous tyres - giving in effect a reduction of 4% in gearing. However, some of the gain seems likely to be down to the performance of the Stelvios. The smaller diameter and lowering of the gearing is something that suits me - I find the standard Birdy rather over geared, particularly at the bottom end, but for those who are younger and/or stronger, or who favour a different pedalling style, the reduction may be less good news. The Cheltenham Origami Ride involved a very short stretch of unsurfaced track - no tarmac, but quite smooth. The Stelvios were completely happy on this surface.
My next test of the Stelvios involved a rolling resistance test, where I coast down a gentle hill and measure the distance covered. Although changes in conditions (wind etc) are often not apparent, I do find that the distances can vary quite appreciably on different occasions, so rather than quote actual distances covered, I prefer to make comparisons. On this occasion I chose the Airnimal Chameleon on Kenda 24 x tyres and the Brompton SP on a Brompton (Kevlar) front and Primo Comet rear tyre. In previous tests the Airnimal has been one of the top performers) and the SP (but then fitted with Primos front and rear) has also done very well. The tests were carried out in the usual way, making two runs with each bike. Although the absolute distances covered were rather less than in some previous tests (wind, road surface etc?) there was no difference in the distances covered by each bike in its two runs, so conditions were stable. The Birdy outran the SP by barely 1 metre, while the Airnimal covered a further 7 metres (in about 150 metres). This is a pretty good performance, and certainly better than previous Birdy tyres could manage.
Since I originally fitted the Stelvios to the Birdy, I have used them under a variety of conditions. Although they have now been fitted for a couple of months, the total distance covered is not all that great, as I have used a number of my other bikes as well during that period. Apart from general commuting and shopping locally, longer outings have included local country rides, rides at CycleFest in Lancaster in August, and some light off-road riding in the form of the canal towpath between Birmingham and Tipton. In such limited use, there is still no sign of wear, as I would expect. I have not had any puncture either in these tyres, but as I have commented repeatedly in the past, I find punctures are strongly influenced by luck, so I don't consider this particularly significant at this early stage. On the road, the Stelvios continue to give a sense of free running, and are a marked improvement in this respect over other tyres I have used on the Birdy. I do still feel that they make the handling rather quicker and more twitchy, and I still lack confidence when riding them on loose surfaces. I haven't made much use of them in the wet, but, as with all my bikes, I would be rather cautious with them in these conditions. I was particularly pleased with the way they handled on the towpath, though - conditions in which I think the Birdy excels. They seemed to roll very freely on the fairly smooth and dry surface, and there was no obvious evidence of their narrow width and high pressure - they appeared to grip well, even though I have found them rather inclined to respond to loose gravel etc on surfaced roads. For the journey to and from CycleFest (most of the distance being on the train), with a substantial load on the bike, handling was still good, though perhaps not quite as stable and inspiring of confidence as on wider tyres.
The choice of tyre for the Birdy has increased dramatically since it was launched, and in terms of numbers, Birdy owners have been well served for some years. However, previously all the tyres available seemed to fall into the category of utility tyres - some offering good life and puncture resistance and road grip, but a little sluggish for longer and/or faster rides n the road. The Schwalbe Stelvio seems to have fully addressed this problem, and it certainly rolls very freely, and in the rather limited tests so far it seems to be quite robust, and handles well. Although it can't be expected necessarily to have the ultimate life and puncture resistance, nor the grip on rougher, wetter or muddy surfaces of the wider tyres such as the Birdy, Schwalbe Marathon and Vredestein San Marco, it performs very creditably in all conditions. I think it will prove very popular on the Birdy, and it becomes the tyre of choice for me on that bike in the future. I've also bought a pair of the 406 size for use on one of my other machines.
As well as the 355 size which fits the Birdy, the Stelvio is already available in the widely-used 406 size (in which it will be the only tyre apart from the Continental Grand Prix which will fit in the limited clearance of the New Series Moulton), and we have heard reports that a 349, which will fit the Brompton, Micro, and classic Moultons amongst others, will be available later this year. I would resist the temptation to assume that because the tyre has the same name it will behave in the same way in different sizes, but reports on the 406 version at least do suggest it is just as good in that size.
A number of members have sent in reports about the Stelvios, in the 406 size as well as the 355. All the users seem favourably impressed, and the views of one of them appear below.
The 406 Stelvio
By Ian Dicken
I've had a set of 406 Stelvios on my APB for about a month now. I fitted them to try and make life a bit easier on the CTC's Phil & Friends ride, but I think the hills (all 2000m of them round the 100km course) had more to do with the amount of effort needed! They certainly roll better than the Marathons I had on previously (as you might expect) and give the handling a lighter feel. Grip seems to be good, both in the wet and dry. Initially I took it quite steady round the corners, but I'm now back to my usual ways without mishap, so far.
Touch wood, I've not had any punctures yet since fitting them, although I have picked up a couple of nicks in the rubber from slivers of glass. The biggest problem I've had has been with inner tubes for them. I initially used my existing inners, but they had to be "rucked" slightly to get them in, so I went out and bought the next size down. These are labelled for use with larger 18" tyres and 11/4" 20" tyres, which sounded about right. However, when I came to fit them, the tubes were tight round the wheel and it was difficult to be sure that the tyre wasn't sitting on top and trapping them. Despite this, they inflated well (with the help of some washing-up liquid) and have run fine since. I'm just not looking forward to having to mend a puncture on the side of the road when it's dark and raining!
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Last updated: 29 September 2002