If you want to reduce weight I would consider looking at tubular tires and rims. They offer more strength for the weight and offer, in my subjective opinion, a better ride.
We are talking about weight and “rotating weight” is important. The current trend towards tuning, titanium and thin walled tubing (TTTT) does not make sense with heavy wheels. How can someone be willing to do anything (and spend a lot of money) to save a few grames in the bicycle frame but accept nearly 300g more rotating weight in the wheels?
The strength of a rim is directly related to its mass, width and cross-section. The taller the section, thicker the sidewalls and the wider the rims, the stronger they are. Since nearly all rim extrudusions are made with 6000 series aluminum alloys, the less the mass the weaker the rim. Forget the ad speak, clincher rims must always be heavier than tubular rims. The shape of a tubular rims is not only closest to the ideal from the view of structural strength but, since tubular tires are glued onto the rim, they don’t require a horn.
Granted ultralight “folding” (kevlar core) clincher tires and inner-tubes are commonly available and have allowed one to develop lighter (more narrow) rims– coming down from well over 500g to near the 400g mark (e.g. the 410g Mavic Reflex). Lighter is better but unfortunately 400g clincher rims are too weak for other than special applications, similar in many ways to sub 300g gram tubular rims. Sure with proper tension one can build a true wheel with these rims but to get towards the 400g mark (like sub 300g tubular rims, e.g. Fiamme Ergals, Mavic GL280s etc.) the rim makers have reduced wall thickness and sometimes chosen harder, more britle, alloys. While softer materials during a clincher rim failure cycle from wear will first bend at the horn, the more britle alloys (can) break with little or no warning— fortunately the catrostrophic rim breakages occur most often during tire inflation. The min. wall thickness for a clincher rim should be 1 mm or more. Many failures of clincher rims have been documented and the wall thickness of these samples have tended to be between 0.7 mm and 1 mm: See also the Hardcore Bicycle Science archive contributions on “How thin may the braking rim of my wheel get”. Lightweight clincher rims should not have walls thinner than 1.5mm (e.g. Mavic MA-2s). Some ultralight clincher rims are made with 1.2 mm walls and offer very little margin for wear. Blue, red or other coloured rims do not provide any additional reliability since the thin eloxial layer, although providing some initial dry wear resistance (which is anyway rather minimal), is usually removed during the very first ride in the rain. Hardox (Grayish Brown, so-called CD by Mavic) rims provide better resistance to breaking wear at the cost of vastly inferior brake performance and increased failures due to cracking. The current limit for reasonable aluminum alloy clincher rims is just under 500g— and the best of them, still, offer strength in the sub 350g tubular class. Tubular rims with 1.2mm or even 1.0 mm (e.g. Fiamme Ergal) walls provide enough reserve given that they have neither the requirement to resist tire pressure (the tire is held on by tire contraction and mastic) and the structure provides substantialy better resistance to lateral deformation. In this light, a 1.0mm tubular rim is stronger, lighter and will last longer than (even) a 1.5mm clincher rim. Add at least 50g for the horn and one sees that a clincher rims must always be substantialy heavier than a tubular rim.
While a clincher wheel plus tire and inner-tube can these days approach what one often considers the weight of a tubular wheelset, one is comparing a weak ultralight wheel with paper-thin (failure prone) tires with a strong tubular wheel with robust and sturdy tires. A tubular rim weighing 60g less than a clincher rim will still be stronger and despite “common knowledge” the frequency of failures of good tubulars is not higher but lower than equivalent clincher tires (e.g. Continental Competition 240 versus GranPrix, Vittoria CX versus their so-called “Open Tubulars”).
The difference in weight of clincher and tubular wheelsets, in this light, is at least 200 grams. That’s 200g rotating mass. What’s the point of trimming weight with paper-thin (e.g. Columbus Nemo) frames, expensive Titanium or “Coke Cans with Wheels” to then throw away 200 grams where it really counts?
And the ride? Forget the talk about the comfort of different frame materials. A harsh ride comes from the wheels, esp. the tires, and not really from the frame. The feel of the ride of a good pair of tubulars is the standard against which everything else is measured.
The horror stories of tubulars are, again in my opinion, exagerated and unjustified. The main thing that you *must* accept *before* making the switch to tubulars is that you will need to repair them (and not toss them unless you earn more than $200/hour and are totally booked).
|Gluing Tubular Tires|
Tubulars tires don’t pop-off when they fail and they don’t generally get snake bite flats. The reliability on poor roads is just one of the reasons that even teams that “ride clinchers” (sponsored) will mount tubulars during the classsics. For the Paris-Roubaix race one often reduces tire pressure to 6-7 bar. Tubulars get “slasher” flats, a tiny hole where the air leaks slowly out. “Slashers” are a pain but, for especially larger cyclists, I would expect “snake bites” to be the greater problem. The odball “common knowledge” limit of tubulars to cyclists weighing 160 lbs (70 kgs) or less is ill founded. While it is generally true that lighter riders have less tire wear but this only means that heavier riders are less suited to very lightweight tires: tubular or clincher. So if you weigh 100 kg don’t even think about racing, except on the track, with 180 gram tubulars. If your counting grams a light tubular up front (220g) and a heavier (260g) in the rear is the way to go.
On poor roads tubulars tires have a distinct reliability advantage. The failure of tubular tires to catch the racing mountain bike scene was due to problems with image and less with the suitability of the concept. While for non-racers the wet, muddy conditions made tire changing impossible this is of little relevance to racing. Since the major sponsors want to sell product they were doomed from the start.
Trashing a $50 tubular is depressing. But I think trashing a $50 clincher is nothing to “light up the day” either. Where clincher tires have a distinct lead over tubulars is in the low cost segment: a cheap clincher will be more reliable, rounder and roll better than a cheap tubular. Cheap tubulars are a waste of money and cost more to operate! In this light, perhaps the poor image of tubulars can be attributed to cheap “training” tires. If you use tubulars you must be prepared, even for touring or training, to select good tires costing at least 50 DM ($30). While more expensive clincher tires are ligher but often more prone to faults (e.g. Continental GranPrix versus SuperSport) the more expensive handmade tubular tires aren’t just lighter and ride better but are often more reliable (e.g. Continental Competition 240 versus Sprinter 250). In the current market the cheapest good tubular tire is the (machine made) Continental Sprinter 250, an excellent tire weighing around 260 grams, which retails at prices between 45 DM and 60 DM in Germany (or $35-$50 in the US).
Mounting tubular tires is not the big messy event it is often considered in the popular press. Letting a new tire stretch for a week or two on a clean rim will make mounting easy. While many tires are suited to brutal stretching (e.g. the Continental)– letting one mount a new tire in minutes– some, esp. silk and fine cotton, are not. With all tubulars, if you pre-stretch them on a rim for a few weeks they will be easier to mount and be rounder. Tires are like wine and even the synthetics such as the Contis improve with aging, so having a few tires around stretching is a good idea….
Many people tend to confuse the max. pressure with the reccomended pressure (given that generally only the max. is printed on the tire). Although the rolling resistance decreases with pressure, confort more rapidly declines. The table below shows a few values and represent a good starting point for most people:
|Continental||Competition 19 27″||19 mm||225 g.||10.0||12.0|
|Competition 22 27″||22 mm||240 g.||8.0||12.0|
|Competition 25 27″||25 mm||270 g.||8.0||12.0|
|Sprinter 250||22 mm||250 g.||8.0||12.0|
|Giro||22 mm||300 g.||8.0||12.0|
1)Weight is listed weight (not true weights)
2) Pressures are “reccomended” and “maximum” Although its all too common for amateurs and recreational cyclists to select absurdly high inflation pressures most professional and veteran road cyclists rarely inflate (even in Time Trials) to beyond ½-1 bar above the above values and in special events (such as the Spring classics of Northern Europe) even select lower pressures. The author tends to inflate the front tire with ½ bar more pressure than the rear.
|Do-it-yourself Tubular Repair kit|
Repairing tubular tires is really very easy. A (surgeons) scaple, a leather needle and some linen thread (even waxed dental floss), some thin patches (the same as used by HP tires), vulcanization fluid and some rubber (shoe repair) glue or latex emulsion (carpet glue) and your set-up. One should be carefull in selecting cements since the latex of the tire casing fabric is easily dissolved by the solvents found in common rubber cement, vulcanization fluid, oil, gasoline and other petrolium distilates. The traditional (and popular) Velox tubular repair kits contain (nearly) everything you need, (these days) in a nice plastic box.
When I was a kid I used to repair them on the roadside (my Velox patch kit was my spare)– I remember once riding with a friend when we rode through a patch of thorns, I think I needed 30 min. to mend all the tires. Sewing a button back onto a shirt is harder and takes just as much time as to sew a tire back together. The hardest part is patching the inner-tube and this is the same for clinchers and tubulars. The time difference between mending a clincher’s or a tubular’s inner-tube is really only maybe 10-15 minutes (or less). Those using the (silly) 18mm clincher tires will switch the timings around in favor of the tubulars. Greg Lemond in his “Complete Book of Bicycling” claimed that tubulars are difficult to repair and that they take loads of time– claiming 45 min. to several hours for an experienced mechanic. While he might have been an excellent cyclist and a well known material fetishist (remember how his eyes glowed when he first saw Boardman’s Lotus) I think that he perhaps personally found it difficult (I find clinchers a pain but there are many people that don’t have problems) or, elected to pass-on “common knowledge”…
|How to Repair Tubular Tires|
Sound complicated? Its not really. After a few attempts one should get a good feeling. Your first few tires, untill you have some experience are probably best mounted on the rear.a) Unless you have some good boot material (silk and the Polyamind material from Conti Competition tires make reasonably good boots, track tires offer the best!) and its an exceptional tire— or you really need it, e.g. roadside repair– its often not worth the effort (except maybe for a needed spare) to boot a severely damaged tire.
You should also keep an eye on the sidewalls as they tend to get worn and this can tear the fine fibres and ruin a good tire. The best overall sidewall protection is natural latex emulsion (this also works for high quality clincher tires). Shake the latex bottle and ONLY use the foamy suds and NOT the liquid as this will help keep the coating thin. Brush a very thin coating ONLY on the sidewalls. If the emulsion does not foam add a tablespoon or ammonia per 250 ml of emulusion. The emusion tends to also get thick so one should dilute it with just enough distilled water to get a nice creamy emulsion. Allways let dry for at least 24 hours before using the tire (and maybe dust with some talcum powder to prevent objects from sticking to the fresh latex).
And a total failure? Clincher tires have the advantage here since with a spare inner-tube and a tire boot one often can get a clincher back on the road. While one can also boot a tubular and replace an inner-tube its substantially more effort and not really something for the roadside! And if the tire is totally trashed? Either an equipment wagon or enough folded tires (clincher just as tubular) or a long walk (although if you really need to and don’t care about the rim one can ride a flat tubular).
While a spare inner-tube and a tire boot (people have been known to use paper money notes or other available materials) might be enough to take on the road while training with clinchers, with tubulars a spare tire is really (despite the practice of my youth) a must. Old, worn, but still intact, tires are the best spares. When the rear tire is low on tread, I tend to rotate the front tire to the rear and the rear to the spare tire collection, yielding in-time a plentifull collection. Sure a spare tire weights more than a boot and inner-tube but it not rotating weight.
For a longer multi-day tour one probably wants, should one use tubulars, to take along 2 spares, repair material and tubular mastic– compared to 2 inner-tubes, repair material, a folding tire and a boot for clinchers. Some people like tubular mastic tape instead of mastic, I don’t. On such a tour one also has clothing, tools and many other things to carry and the additional 300g for the tubulars is a disadvantage but tolerable. While wide heavier weight clincher tires are probably best here, for tubular wheels some of the special Paris-Roubaix Pavé tires (e.g. Vittoria, Clement) offer excellent alternatives (to building a new wheelset for that special tour). For fast Alpine descends one should also select a harder glue and keep an eye on rim heat. Its important to use a good brake technique and avoid continuous use of ones calipers as this can cause significant heat build up. Heat can soften the mastic or, with clincher tires, melt the inner-tube (causing a blow-out).
The absolute #1 problem with tubular tires, beyond incorrect mounting, is heat from braking on the front rim. I’m not sure which is the greater danger, it or clinchers popping?
You say that I’m overstating the clincher popping? It happens just as tubulars can float on “hot” glue. Both are problems, both happen, and luckily both are not frequent— it would still be much better if they never happen.
So you get tubulars and curse me after your first flat? At this point I think clinchers are kind of like MS-Windows versus Unix. MS-Windows is not the right solution for many but “no one ever got fired over it”.