Forum home Road cycling forum Cyclocross

Why do cx racers run such narrow gearing?

JterrierJterrier Posts: 97
edited December 2016 in Cyclocross
I posted an earlier thread about what gearing i am going for on my new bike, but the question that has been bugging me for ages is, why do cx bikes have such incredibly tough gearing? I watch the replays of top guys like nys and van aert etc grinding their way up slopes, killing themselves, and having to get off half way up and wonder why it is this way. Is there a historic reason? Is spinning up in a low gear not more sensible?

Just wondered really.
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Posts

  • imposter2.0imposter2.0 Posts: 11,003
    Spinning is not an option if it is quicker to run/carry...
  • doug5_10doug5_10 Posts: 465
    Much less traction as well, CX cadence is usually much lower than the road when going uphill
    Edinburgh Revolution Curve
    http://app.strava.com/athletes/1920048
  • DOn't underestimate how stupid and narrow minded PRO cyclists can be...
  • fat daddyfat daddy Posts: 2,632
    From a non-racer point of view, I get narrow gearing for CX .... trying to keep your speed on sticky, ever changing gradient grass and terrain its nice to be able to just flick one tooth at a time on the rear, a slight gradient change and you don't want to be d1cking about trying to work out what gear is more comfortable when the one in the middle of them that you don't have would be better .... its a lot more pronounced than when on the road.

    BUT

    screw that I am unfit and come from a MTB background, I want an easy gear that spins up and wheel spins a lot as I go up hill, I cant be doing with grinding my censored off.
  • Having recently bought a cx bike, traction definitely plays a big part, going up a 10-15% mud/grass bank you need to keep a lower cadence in a bigger gear otherwise you just get a lot of rear wheelspin. I would imagine the pro's have worked out which is quicker for them, grind up part of the climb and then run the rest must work out as generally being faster than trying to spin a lower gear as I assume they would not do it otherwise! I guess with the traction issue they also don't want to take the risk of sliding out and losing time.
  • I did a fun MTB race once which had some steep slippery climbs on it. I had to borrow a bike because I'd only ever had road bikes. When it got steep my natural inclination was to jump off and run while the more experienced MTBers stayed on their bikes, and I was going up faster than anyone else on the climb. They all flew past me on the downhill though! So I think it just is because it's just faster to run than spin when it gets steep, especially when traction is at a premium.
  • tgotbtgotb Posts: 4,714
    So I think it just is because it's just faster to run than spin when it gets steep, especially when traction is at a premium.
    This. You can spot the experienced MTBers who are new to CX because they try to ride pretty much everything, even if it would be faster to run. On the trickiest bits of the course there's generally only one rideable line. If you're running, you stay on that line and no-one who's still riding can get past. If you're riding, the person who's behind can just run round you.

    Traction, not gearing, is generally the limiting factor on steep climbs in cyclocross races.
    DOn't underestimate how stupid and narrow minded PRO cyclists can be...
    Although they probably have a better idea than someone who hasn't actually taken part in a cyclocross race.
    Pannier, 120rpm.
  • ah. kind of makes sense now. traction limits due to thin tires. I suppose as well there has historically never been road chainsets with wide gearing anyway - until quite recently you couldnt even get a road 11-32 so if you WANTED to be all spinny you would have needed a heavy MTB setup.

    the point about it being faster to get off and run, and it helpfully blocks the racing line too, i think only applies to the sharp end; at the middling amateur level I have done a fair few races wherein I have rode uphill (spinning like crazy admittedly on either an MTB or my MTB geared cx bike...) and passed people. But thats hardly the sharp end.
  • I use a CX gearing on the road 36 x 46 front and 12-30 rear... I've spun out of gears once, on the A66 towards Keswick folks were doing 55/60 Km/h and I could not keep up. Not sure what makes it a good range for cycling in the mud to be honest.

    Lots of people have realised it and run a single chainring at the front. If you need a double, I guess a 34/44 would be more adequate or even a 34/42.

    The lack of sensible rear cassettes is down to derailleur capacity more than anything, if you pair your drivetrain with a MTBike derailleur like an XT Shadow you can run up to 36 or even 40 Teeth and it doesn't jam with mud as easily as the road (cyclocross) do... it doesn't even snap as easily as the road derailleurs do, but obviously you don't look the part... as you need to use inadequate components in cyclocross... it's part of the unwritten rules...

    Some are written though, for instance the fact that you have to run < 33 mm tyres, when it's obvious that a 40 or 50 mm one would be much better in real mud... but that keeps the old tradition of gluing a tyre to a hoop of metal alive and the UCI is all about making sure you don't ride anything Eddy Merckx and De Vlaeminck would find exceedingly modern.
  • tgotbtgotb Posts: 4,714
    You need a fairly high top gearing specifically for the few, but important, occasions where you find yourself sprinting on tarmac. I've hit 30mph on a handful of occasions, sprinting off the start line; the pros are obviously going to be quite a bit faster. On those occasions, you have to have the gearing. 38x12 does that for me, but some riders prefer a much higher gearing at those speeds. The best way to figure out what gearing you need is to do some races, and then look at what gears you actually used...

    MTB components are actually getting pretty mainstream, depending on your groupset manufacturer. One big advantage of SRAM is that you can pair road shifters with an MTB mech, and quite a few riders have shifted (sorry!) to SRAM for this reason. A short cage MTB rear mech will happily handle a 36T sprocket, but other than for niche races like 3 Peaks, there's no real need.

    As for tyre widths - allow wider tyres and you change the nature of the sport. If you want to race 50mm tyres and twiddly gears, you can. It's called mountain biking.
    Pannier, 120rpm.
  • tgotb wrote:
    As for tyre widths - allow wider tyres and you change the nature of the sport. If you want to race 50mm tyres and twiddly gears, you can. It's called mountain biking.

    Restrictions have never helped the sport... for years the UCI have resisted disc brakes to nobody's gain... for years they asked hour record attempts to be done on a Merckx alike bike... to the point that nobody cared anymore, they still impose a frankly pointless 6.8 Kg weight restriction on road bicycles, which limits innovation in materials and technology (let's be clear, carbon is not a new material).

    Personally I think being open to innovation of any sort can only be a good thing

    Funnily enough the most open minded about innovation seem to be the folks at CTT UK, whose only restrictions are a result of safety concerns
  • tgotbtgotb Posts: 4,714
    tgotb wrote:
    As for tyre widths - allow wider tyres and you change the nature of the sport. If you want to race 50mm tyres and twiddly gears, you can. It's called mountain biking.

    Restrictions have never helped the sport... for years the UCI have resisted disc brakes to nobody's gain... for years they asked hour record attempts to be done on a Merckx alike bike... to the point that nobody cared anymore, they still impose a frankly pointless 6.8 Kg weight restriction on road bicycles, which limits innovation in materials and technology (let's be clear, carbon is not a new material).

    Personally I think being open to innovation of any sort can only be a good thing

    Funnily enough the most open minded about innovation seem to be the folks at CTT UK, whose only restrictions are a result of safety concerns
    I can see where you're coming from, but even CTT have restrictions to avoid changing the nature of the sport. One example would be the ban on recumbents, which is presumably not for safety reasons. I'd put CX tyre width restrictions on a par with that; allowing tyres of any width significantly changes the skills required, and it becomes a quite different sport. One of the most satisfying aspects of CX is extracting more grip from the tyres than your opponent (which is still more about technique than equipment). So yes, innovation is a good thing, but there have to be limits somewhere, purely to define the sport.
    Pannier, 120rpm.
  • VamPVamP Posts: 674
    I don't believe that wider tyres give better traction, especially not in mud.

    As to the pros being stupid and narrow minded...

    Ugo I know trolling is the new black, hell play it right and it can get you elected US President, but have you spent any time at all in a competitive environment? Met many competitive types who turn their back on genuine technical advantage?
  • tgotb wrote:
    One of the most satisfying aspects of CX is extracting more grip from the tyres than your opponent (which is still more about technique than equipment). So yes, innovation is a good thing, but there have to be limits somewhere, purely to define the sport.

    I guess the sweet spot is probably not far off 33 mm and running 50s would most likely lose you a race in all but the deepest mud conditions...
    On balance the rule is probably unnecessary... the nature of the course decides which tyres or else are the most appropriate.

    PS, good to know about SRAM... especially now that Shimano 11 is no longer compatible with MTB... is the quality a bit better than it was a few years ago when SRAM shifters were basically disposable?
  • The other thing you will find is if you race, is that you are going hell for leather so much you don't think to change gear.
  • VamP wrote:

    Ugo I know trolling is the new black, hell play it right and it can get you elected US President, but have you spent any time at all in a competitive environment? Met many competitive types who turn their back on genuine technical advantage?

    That's all you seem to be able to say... every time someone disagrees, he must be a troll.
    Your narrow mind can't see beyond your little bubble of races, glue and tubular tyres. PROs are conservative because they are only interested in winning races and whatever works for them has to be good enough for Joe average too.

    The point is: CX bikes began to sell when the UCI relaxed the regulations and allowed disc brakes... manufacturers began to flog bikes that people actually wanted to buy... as opposed to pieces good for a museum... not just folks living in a bubble, but normal folks... in fact mostly normal folks, some of them even get interested in your bubble and benefit your own little garden!

    Relaxing the regulations on tyre size means manufacturers would begin to churn out frames that can take bigger tyres, so one could for instance tap into the market of 27.5 inch MTBike wheels... of which there are plenty, as opposed to some road wheels with some dodgy CX credentials and bearings that need replacing every other week.

    None of my two CX frames can take tyres designed to go on a 27.5 inch wheel, simply the rear triangle is not wide enough. So one has to look at gravel bikes, which have marginally more clearance, although often not enough, but they are in essence hard tail MTBikes with drop bars and with no suspensions (yet).

    The CX market has to somewhat benefit from MTBike development, as road components are getting more and more fiddly, expensive and delicate and unsuitable to be used in mud
  • MoonbikerMoonbiker Posts: 1,706
    Some are written though, for instance the fact that you have to run < 33 mm tyres, when it's obvious that a 40 or 50 mm one would be much better in real mud

    haha so wrong

    Even the people who ride mtbs in our league know this isn't true & so they mostly run narrow cx tyres or narrow mtb ones, on there mtb bikes. The fast ones do anyway, the ones that don't soon end up with 5kg of mud clogging there wide mtb "mud tyres" making them pretty useless.
  • Chris JamesChris James Posts: 1,040
    ...for instance the fact that you have to run < 33 mm tyres, when it's obvious that a 40 or 50 mm one would be much better in real mud... but that keeps the old tradition of gluing a tyre to a hoop of metal alive and the UCI is all about making sure you don't ride anything Eddy Merckx and De Vlaeminck would find exceedingly modern.

    Wider tyres aren't necessarily better in mud. Narrow tyres can cut through the mud and get grip on the firm surface below the top layer.

    There is also the issue of the mud / leaves / stones sticking to the tyre and getting jammed in the chainstays. Obviously frame design impacts this to a degree, but there is only so wide you can splay the stays when there are standard bottom bracket and hub widths and you need clearance for the cranks and ideally also want a Q factor that isn't crazy wide.

    There are also cons to using a MTB rear derailleur, rather than a short cage road one - presumably because they run lower to the ground they tend to attract more leaves and the like, and a close cassette will have a tighter chain across it's gears than one where the chain has been set for a monster bail out gear. Shorter chains seem to help limit the chances of rear mechs ripping (obviously, there are also pros to a wide ranger cassette on a single ring - e.g. no front shifting, weight, simplicity etc.).
  • MoonbikerMoonbiker Posts: 1,706
    I would like better tyre clearance, not to be able to run any wider tyres but to stop mud clogging under the forks.

    Pros etc just have a second bike & a pit crew so clearance is less of an issue...
  • tgotb wrote:
    One of the most satisfying aspects of CX is extracting more grip from the tyres than your opponent (which is still more about technique than equipment). So yes, innovation is a good thing, but there have to be limits somewhere, purely to define the sport.

    I guess the sweet spot is probably not far off 33 mm and running 50s would most likely lose you a race in all but the deepest mud conditions...
    On balance the rule is probably unnecessary... the nature of the course decides which tyres or else are the most appropriate.

    PS, good to know about SRAM... especially now that Shimano 11 is no longer compatible with MTB... is the quality a bit better than it was a few years ago when SRAM shifters were basically disposable?

    No.
  • tgotbtgotb Posts: 4,714
    There are also cons to using a MTB rear derailleur, rather than a short cage road one - presumably because they run lower to the ground they tend to attract more leaves and the like, and a close cassette will have a tighter chain across it's gears than one where the chain has been set for a monster bail out gear. Shorter chains seem to help limit the chances of rear mechs ripping (obviously, there are also pros to a wide ranger cassette on a single ring - e.g. no front shifting, weight, simplicity etc.).
    If you're using SRAM, you can get short cage MTB derailleurs. These seem to be a pretty good compromise; they don't stick down any further than a road mech, but keep the chain tighter and seem to be more robust. You definitely don't want a longer cage than necessary though, that's asking for trouble.

    I think SRAM shifters may have become more reliable, or maybe the more expensive ones are more robust. I blew up a couple of Rival shifters on my commuting bike, probably 4-5 years ago. The replacement Rival shifter has lasted 4 years with no issues, and is still going strong. My CX/Road bikes were all built with second-hand SRAM Red shifters (second-hand Red being a lot cheaper than brand new Rival), and have had no issues at all. For me, at least, the mean time between failures is large enough for reliability not to be a concern.
    Pannier, 120rpm.
  • tgotbtgotb Posts: 4,714
    I guess the sweet spot is probably not far off 33 mm and running 50s would most likely lose you a race in all but the deepest mud conditions...
    On balance the rule is probably unnecessary... the nature of the course decides which tyres or else are the most appropriate.
    Apologies to the OP - this is going somewhat off topic...

    As others have said, wider tyres are unlikely to be an advantage in mud. Where they would be more of an advantage is in early season races on relatively rough, dry terrain (rocks, roots etc) where the extra volume provides some suspension, and also allows you to run lower pressures without destroying your rims. This terrain is not common on CX courses, but does occur occasionally; an extreme example is the 3 Peaks race, where the descents could be ridden a lot faster and more easily on MTB tyres (and even more so with suspension).

    Apart from the fact that allowing MTB tyres would change the nature of CX racing, riders would also need to own a much wider selection of tyres to allow them to choose the best width for the conditions aswell as the best tread. Therefore the rule has an important function in controlling costs. Using the 3 Peaks race as an extreme example, if the equipment rules were opened up and you wanted to compete at the sharp end, you'd probably need a road bike, a TT bike, two CX bikes, two MTBs and an army of helpers to get them to the right changeover points. As it is, the top riders can compete on two CX bikes with one helper, and have only the smallest advantage over those competing on one bike.
    Pannier, 120rpm.

  • Wider tyres aren't necessarily better in mud. Narrow tyres can cut through the mud and get grip on the firm surface below the top layer.

    There is also the issue of the mud / leaves / stones sticking to the tyre and getting jammed in the chainstays. Obviously frame design impacts this to a degree, but there is only so wide you can splay the stays when there are standard bottom bracket and hub widths and you need clearance for the cranks and ideally also want a Q factor that isn't crazy wide.

    There are also cons to using a MTB rear derailleur, rather than a short cage road one - presumably because they run lower to the ground they tend to attract more leaves and the like, and a close cassette will have a tighter chain across it's gears than one where the chain has been set for a monster bail out gear. Shorter chains seem to help limit the chances of rear mechs ripping (obviously, there are also pros to a wide ranger cassette on a single ring - e.g. no front shifting, weight, simplicity etc.).

    Bigger tyres can be ran at lower pressure without the need for expensive and frankly antiquated "sew-ups". 20 PSI or less are not uncommon in MTBikes with tubeless... So yes, you do get more grip.

    I don't think Q factor should be of great concern for a bicycle designed to be ridden for an hour or two... I don't even think the difference would be so majestic... we are talking 5 mm each side, you'd probably hardly notice

    I have used an XT shadow rear mech for the past 3 years now... I still have to find a drawback... other than I need an inline barrel adjuster. Before I got fed up of riding in the mud, I used to go out quie a lot in the Surrey and Chiltern hills, where the chances of clogging a derailleur with leaves are greater than in a muddy field, but nothing... after all they are designed to do just that, so it's not surprising they do it better than a derailleur designed to be ridden on tarmac
  • tgotb wrote:
    Apart from the fact that allowing MTB tyres would change the nature of CX racing, riders would also need to own a much wider selection of tyres to allow them to choose the best width for the conditions aswell as the best tread. Therefore the rule has an important function in controlling costs. Using the 3 Peaks race as an extreme example, if the equipment rules were opened up and you wanted to compete at the sharp end, you'd probably need a road bike, a TT bike, two CX bikes, two MTBs and an army of helpers to get them to the right changeover points. As it is, the top riders can compete on two CX bikes with one helper, and have only the smallest advantage over those competing on one bike.

    This is a funny one, as the UCI promoted the "athlete hour record" as a way to keep costs down, which were spiralling, due to high tech bikes. The record anyone can have a go at, as all you need is Eddy MErckx's bike...
    The funny thing is that nobody could actually buy a bike that was compliant with the UCI rules, so it had to be made bespoke and was actually more expensive than buying a top of the range pursuit bike.

    The argument is pointless, anyone will compete within his/her means and your collection of bikes and wheels goes to show that if the rule is meant to limit costs, then the rule doesn't work... :mrgreen:
  • Chris JamesChris James Posts: 1,040
    Bigger tyres can be ran at lower pressure without the need for expensive and frankly antiquated "sew-ups". 20 PSI or less are not uncommon in MTBikes with tubeless... So yes, you do get more grip.

    I don't think Q factor should be of great concern for a bicycle designed to be ridden for an hour or two... I don't even think the difference would be so majestic... we are talking 5 mm each side, you'd probably hardly notice

    I have used an XT shadow rear mech for the past 3 years now... I still have to find a drawback... other than I need an inline barrel adjuster. Before I got fed up of riding in the mud, I used to go out quie a lot in the Surrey and Chiltern hills, where the chances of clogging a derailleur with leaves are greater than in a muddy field, but nothing... after all they are designed to do just that, so it's not surprising they do it better than a derailleur designed to be ridden on tarmac

    By that logic then a fat bike would make a great cyclocross bike. You only need enough grip, which can be achieved by cyclocross tyres. I race on clinchers at the high 20s psi and don't have any grip problems.

    Even so, all the grip in the world doesn't help you if your wheels won't go round because the mud stuck to them has jammed in the chainstays.

    There are some courses where MTBs are faster than cyclocross bikes, but they are pretty few and far between and are usually at the lower end races where the course designer doesn't follow the guidance and basically just designs an XC MTB route.

    I also use my cross bike for blasting around in the woods and it is great fun. I've never had any problems with my rear mech there, and I use a short cage road one. I've also used my cross bike at various trail centres and off road routes in the Lakes and Yorkshire Dales without any problems.

    Cyclocross racing is very different in that by the time you come to race then potentially several hundred riders have destroyed the course by riding multiple race or warm up laps on your line. This is very different to you picking your own line through a wood, and it forces you through a LOT of mud. If the mud is followed by leaves, twigs or stones these instantly stick to the mud and get jammed everywhere - especially the jockey wheels, which will rapidly stop being able to rotate and will rip your hanger off.

    At a recent race that I attended 1 in every 7 riders snapped their hangers - and a good chunk of the field had a pit bike and crew who could wash their bike every half lap to try to prevent the breakages.

    I've done a fair amount of mountain bike routes on my cross bike and the bike needs hosing off afterwards. After only 40 minutes of cyclocross (I'm a vet now :wink: ) my cross bike has sometimes been so badly gunked up that I have had to remove the cranks because so much grass was jammed in there that they wouldn't rotate.
  • Chris JamesChris James Posts: 1,040
    Moonbiker wrote:
    I would like better tyre clearance, not to be able to run any wider tyres but to stop mud clogging under the forks.

    Pros etc just have a second bike & a pit crew so clearance is less of an issue...

    Yes, me too. I'm happy with my tyres but my next frame will have more rear clearance (my front forks are okay).
  • Bigger tyres can be ran at lower pressure without the need for expensive and frankly antiquated "sew-ups". 20 PSI or less are not uncommon in MTBikes with tubeless... So yes, you do get more grip.

    I don't think Q factor should be of great concern for a bicycle designed to be ridden for an hour or two... I don't even think the difference would be so majestic... we are talking 5 mm each side, you'd probably hardly notice

    I have used an XT shadow rear mech for the past 3 years now... I still have to find a drawback... other than I need an inline barrel adjuster. Before I got fed up of riding in the mud, I used to go out quie a lot in the Surrey and Chiltern hills, where the chances of clogging a derailleur with leaves are greater than in a muddy field, but nothing... after all they are designed to do just that, so it's not surprising they do it better than a derailleur designed to be ridden on tarmac

    By that logic then a fat bike would make a great cyclocross bike. You only need enough grip, which can be achieved by cyclocross tyres. I race on clinchers at the high 20s psi and don't have any grip problems.

    Even so, all the grip in the world doesn't help you if your wheels won't go round because the mud stuck to them has jammed in the chainstays.

    There are some courses where MTBs are faster than cyclocross bikes, but they are pretty few and far between and are usually at the lower end races where the course designer doesn't follow the guidance and basically just designs an XC MTB route.

    I also use my cross bike for blasting around in the woods and it is great fun. I've never had any problems with my rear mech there, and I use a short cage road one. I've also used my cross bike at various trail centres and off road routes in the Lakes and Yorkshire Dales without any problems.

    Cyclocross racing is very different in that by the time you come to race then potentially several hundred riders have destroyed the course by riding multiple race or warm up laps on your line. This is very different to you picking your own line through a wood, and it forces you through a LOT of mud. If the mud is followed by leaves, twigs or stones these instantly stick to the mud and get jammed everywhere - especially the jockey wheels, which will rapidly stop being able to rotate and will rip your hanger off.

    At a recent race that I attended 1 in every 7 riders snapped their hangers - and a good chunk of the field had a pit bike and crew who could wash their bike every half lap to try to prevent the breakages.

    I've done a fair amount of mountain bike routes on my cross bike and the bike needs hosing off afterwards. After only 40 minutes of cyclocross (I'm a vet now :wink: ) my cross bike has sometimes been so badly gunked up that I have had to remove the cranks because so much grass was jammed in there that they wouldn't rotate.

    I guess my point is not coming across the way I mean it... I am basically against over-regulation... defining a tyre size means that manufacturers have to conform and the scope for new designed is somewhat limited. Discs opened up things dramatically and allowing different tyre sizes would give even more scope.

    Whether that will result in a change of equipment by PROs or not is irrelevant... as a consumer I am interested in more choice and I would really like a drop bars bike that can take 2.5 inch tyres on 650b rims... I think it would be popular, some folks would use it for CX, others for a ride on the Ridgeway, others to go shopping or whatever...

    Whether anyone would win the Worlds or not on it I am frankly not bothered
  • Bigger tyres can be ran at lower pressure without the need for expensive and frankly antiquated "sew-ups". 20 PSI or less are not uncommon in MTBikes with tubeless... So yes, you do get more grip.

    I don't think Q factor should be of great concern for a bicycle designed to be ridden for an hour or two... I don't even think the difference would be so majestic... we are talking 5 mm each side, you'd probably hardly notice

    I have used an XT shadow rear mech for the past 3 years now... I still have to find a drawback... other than I need an inline barrel adjuster. Before I got fed up of riding in the mud, I used to go out quie a lot in the Surrey and Chiltern hills, where the chances of clogging a derailleur with leaves are greater than in a muddy field, but nothing... after all they are designed to do just that, so it's not surprising they do it better than a derailleur designed to be ridden on tarmac

    By that logic then a fat bike would make a great cyclocross bike. You only need enough grip, which can be achieved by cyclocross tyres. I race on clinchers at the high 20s psi and don't have any grip problems.

    Even so, all the grip in the world doesn't help you if your wheels won't go round because the mud stuck to them has jammed in the chainstays.

    There are some courses where MTBs are faster than cyclocross bikes, but they are pretty few and far between and are usually at the lower end races where the course designer doesn't follow the guidance and basically just designs an XC MTB route.

    I also use my cross bike for blasting around in the woods and it is great fun. I've never had any problems with my rear mech there, and I use a short cage road one. I've also used my cross bike at various trail centres and off road routes in the Lakes and Yorkshire Dales without any problems.

    Cyclocross racing is very different in that by the time you come to race then potentially several hundred riders have destroyed the course by riding multiple race or warm up laps on your line. This is very different to you picking your own line through a wood, and it forces you through a LOT of mud. If the mud is followed by leaves, twigs or stones these instantly stick to the mud and get jammed everywhere - especially the jockey wheels, which will rapidly stop being able to rotate and will rip your hanger off.

    At a recent race that I attended 1 in every 7 riders snapped their hangers - and a good chunk of the field had a pit bike and crew who could wash their bike every half lap to try to prevent the breakages.

    I've done a fair amount of mountain bike routes on my cross bike and the bike needs hosing off afterwards. After only 40 minutes of cyclocross (I'm a vet now :wink: ) my cross bike has sometimes been so badly gunked up that I have had to remove the cranks because so much grass was jammed in there that they wouldn't rotate.

    I guess my point is not coming across the way I mean it... I am basically against over-regulation... defining a tyre size means that manufacturers have to conform and the scope for new designed is somewhat limited. Discs opened up things dramatically and allowing different tyre sizes would give even more scope.

    Whether that will result in a change of equipment by PROs or not is irrelevant... as a consumer I am interested in more choice and I would really like a drop bars bike that can take 2.5 inch tyres on 650b rims... I think it would be popular, some folks would use it for CX, others for a ride on the Ridgeway, others to go shopping or whatever...

    Whether anyone would win the Worlds or not on it I am frankly not bothered


    Build it, I've basically done that but with 26" wheels as that's what I had. The great thing is if you have a bike like that it'll easily take 29er wheels with CX tyres too.

  • Build it, I've basically done that but with 26" wheels as that's what I had. The great thing is if you have a bike like that it'll easily take 29er wheels with CX tyres too.

    I'd really like 27.5, which basically keeps gearing unchanged. I'd probably have to fit MTB cranks to make it work on a wider rear triangle... can you buy a MTB double chaniset?

  • Build it, I've basically done that but with 26" wheels as that's what I had. The great thing is if you have a bike like that it'll easily take 29er wheels with CX tyres too.

    I'd really like 27.5, which basically keeps gearing unchanged. I'd probably have to fit MTB cranks to make it work on a wider rear triangle... can you buy a MTB double chaniset?

    Yep, a good few still about from Shimano and others and still being produced with the new, top of the range kit:

    http://www.chainreactioncycles.com/shim ... prod119769

    I'm running a 46T at the front with an 11-36 at the back (although I'm using bar end shifters so can currently only just get the 32). It's massively over-geared for MTB but the idea was to have a do anything bike, MTB trails to road riding with my club. So far it's worked well but when I have the money I'll be updating the bar ends to get the full gear range and fitting a double crankset. If you want drop bar shifters with an MTB rear mech you'll need to run a wolftooth Tanpan or something similar:

    http://www.wolftoothcomponents.com/coll ... cts/tanpan

    But if the CX set-up gives you the gear range you want it'll be fine without.
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