Are Softer MTB Tyres Faster? | Ask GMBN Tech

– Welcome to Ask GMBN Tech. This is our weekly Q and A show where you ask the questions and we hopefully answer them for you. If you wanna ask some questions, you can add them in the
comments below this very video. Use the hashtag #ASKGMBNTECH though, so it just separates your questions from the actual comments. And of course, you can email
them in to the email address on the bottom of the screen right there. Right, so jumping straight in is the first question from Tomuno01. Hi Doddy, I’m both a mountain bike rider and a trials rider and
I wanted to ask you why, with the advent of the 1x system, there is almost no one
adopting a front freewheel, i.e. trial style, on a mountain bike? Freewheels are way cheaper than free hubs, easier to replace and most importantly, the system will offer the possibility to change gear whilst freewheeling. Okay, yeah, so interesting there. So a lot of good points in there, but let’s just go back to what I’ve used on trials bikes to start with. Of course the gearing
on classic trials bikes is immensely low, and of course they’re normally set up single-speed, so in order to get a low enough gear, best you need a tiny sized chainring. And as you know, the
freewheel-style system are way smaller than some of the smallest chainring sizes you can get on a bike that would be compatible
with standardized cranks. So that was the first reason that we used. And the second reason, of course, is to give ground clearance, again with that small chainring there, and of course a lot of the 20-inch bikes and then later the 24s
and 26s have bash plate, so that became less of an issue, it was more about the gearing. So one of the advantages
are moving the weight from the rear of the
bike, all the derailleur, the cassette, all that stuff, and putting it on the front of the bike, or the main part of
the bike where you are. And you’re taking that
weight away from the wheels that you’re arguably moving around. So that’s very cool on a trials bike, however, it does pose a few issues if you did this system on a normal bike. Essentially, the cassette-style system is a lot more reliable, and it’s designed to cope with the load that mountain bikes and all
the gearing puts through them. So traditional freewheels,
whilst they work quite well, they are susceptible to issues, and I know there are some more dedicated trials ones out there, but I’m not convinced that
they would be a better idea than a regular, cassette-style system we see on mountain bikes. Now of course if you wanted to use a cassette-style system for
trials you can do this now, because there are
cassette systems out there like the Hope trials one
you can see onscreen now. That has a dedicated steel body on it, it’s designed to be set up single-speed, it’s designed to cope with the stress that you can put though that hub. And of course it’s less of an
issue with ground clearance because of bash plates
and things like that. So you can work around
that side of trials bikes. But if you’re looking at
normal mountain bikes, the cassette system is far better, just for the way it works. There’s less friction in it. It’s a better system for
mountain bikes to use with gearing and all the other stuff that you need on a mountain bike. But arguably, moving that weight
from the back of the wheel is something that we
still need to figure out. And you’re starting to see
this on some bike designs. You’re seeing this with
the Pinion gearbox system, and even to an extent with e-bikes, you’re gonna start seeing things changing and migrating in the future. I guess the last thing
really to sort of add is if you work and have a 1x system and use the freewheel
on the front instead, you’re gonna have to have
a pretty big chainring and it’s gonna put a lot
of stress for a system that’s already not the most reliable. Whereas as I emphasized before, the cassette system on the
back, it’s been refined, there’s ratchet systems on hubs, they’re very, very reliable these days. I know that I’d rather
pedal something like that that is reliable, it’s never gonna slip or endanger me when I’m riding. But it’s not to say that something like that couldn’t happen in the future. (bike wheel whirring) Very cool question from
Marcus Von Shoultz. This actually made me think we
need to do a feature on this. What is faster? Grippier tire with more pressure or faster rolling tire with less pressure? And also, what is grippier? I’ve forever been having this
sort of battle with myself trying to find out what works
best for the trails I ride. So just so you know, locally
we have these awful conditions that you really do need
good rubber to hook up on. But the disadvantage is, to
get to those sections of trail there’s a lot of like country
lanes and that to join them, so you quite often end up
with a harder compound tire on the rear, which enables
you to roll that bit quicker, or so seemingly quicker, and a softer compound tire on the front. However, tire pressures have
a massive effect on this, and what I’ve noticed is that a soft compound tire
run at a firm pressure doesn’t feel much faster than when it’s at soft pressure. However, when you have
a hard compound tire, it feels dramatically different when you run it hard to
when you run it soft. I definitely think this is something we need to do some
trail-side testing on though. I mean, as far as grip goes, I definitely think the first instance that makes a difference is tire pressure. ‘Cause you can have a
really, really good tire, set it up firm, and if the tire’s not able to deform around the object that you’re trying to give traction on, like edges of rocks and that, it just won’t grip in the same way. So I definitely think
you can get more grip out of a firmer tire just
by adjusting tire pressure. than you can with a soft compound tire run at a firmer pressure, and it’s gonna be able
to go faster as well, at least that is my
theory on how things feel. There’s also something else
to throw into the mix here. So I’ve had this conversation with several people over the years, and everyone’s got their own theories on what works and what doesn’t work. So I will make a video on this, and I think we’ll hook
up with Neil on GMBN and try and work this out, because there’s some definitely
some interesting points. But in the summer, a lot of riders I know, including myself, run our tires quite firm and the reason for that is you wanna get to and
from the trails quicker. But because the trails are
nice and dry in the summer, you end up leaving your tires as they are. You sacrifice a bit of grip, ’cause it feels like
the tire rolls so fast. But this summer I actually practiced a lot with a lot lower pressures
than I normally would, and it was substantially faster in every section of trail. And it’s common sense really if you actually think about this. If you’re running a firm tire, it’s gonna be fast on a firm surface, but as soon as it hits a rock or root or anything like that, it’s not gonna deform and follow, it’s actually more likely
to get bounced off, like deviate from its initial route. And of course any time in the air is time you’re slowing down on the bike, it’s not quicker. Unless of course in the situation where you’re doing a gap
jump or whatever it might be. I’m talking just covering ground on trail. So I definitely think that softer tires are faster off-road, but we have to have this
as a comparison video. And there’s a lot to do in this. So we have tire pressure as a factor, we have tire size as a factor in there. I don’t think we’ll do wheel size, that’s been done to death, we kinda know that bigger
wheels do go faster in a straight line on certain terrain, and smaller wheels will corner
better in certain terrain, maybe they’ll be a bit more agile. I think all that stuff’s kinda put to bed and it comes down to personal preference. But there’s definitely
some differences to be made and some speed to be had
with different tire compounds and different pressures. So watch this space. (bike wheel whirring) And next up is a carbon
question from Moangel Please. Love the show, thanks
for all the great info. Well, thank you for thanking us. We love delivering for you. I’ve got a little curious
hearing about all the tech, and I’ve just been wondering, if I bought the new Santa
Cruz reserve carbon rims, they have a lifetime warranty. But if I bought those rope spokes, would it void the warranty? I had to have a look at the
Santa Cruz site for this ’cause I actually thought
they only came as wheels, but I stand corrected
that you can get them as rims and as wheels. And just reading this from the site, the warranty stands on the rims, whether bought individually or rebuilt from wheel sets. But you only get the full wheel replaced if it’s an original spec build. So basically they do
have a limited warranty on them but it’s on the product itself. So let’s just say you damage the rim, they will honor it if
it’s defects in the rim, but if you damage the rim, i.e. went under a bus
or something like that, then they have sort of a
program where you can buy a discounted rim to
replace your damaged rim. So it’s a very good
concept that they have, and I see no reason why, if you bought Santa Cruz rims and you got them laced
up with those rope spokes that they wouldn’t honor the warranty, because as long as
they’re built correctly, it should be fine. So there you go. (bike wheel whirring) Next up on the list is from Scoobgirl. Hi Doddy, my bike’s a
2017 Cannondale Trail 5. I was wondering what I would need to change the type of bottom bracket. At the moment, it’s got
a square taper, I think. Would it be possible to
fit a hollow-style crank and convert it to 2x rather
than the 3x it currently has, and can I have a list of
things to do this upgrade? I have to ask, as looking
for all the different types of bottom brackets and
cranks is very confusing when you don’t have a clue. Thanks, Danny. Okay, Danny, well, first up,
I had a look at that bike, yeah, it’s a square taper BB, so the good news about that is
it’s a fairly standard item, it’s just a threaded BB, so you can fit virtually any style of any option of BB into your bike. Obviously press-roots won’t fit, but what I mean is there’s a lot of threaded options for you. As for converting your 3x to a 2x, you can do this, but
obviously you’re gonna need to get a 2x crank on there, because 3x’s and 2x’s,
they’re not really compatible, you can get some offset chainrings but that might just confuse you a bit. So for the time being if you wanna get a Hollowtech crank on there, yep, get that in a 2x, no problem. And obviously, some cranks will come with the correct bottom
bracket for your bike. Others, you have to buy it separately. So just take note between brands there. But that’s nice and easy, and very easy to fit as well. I’ll tell you about the
tools for that in a sec. Now with your derailleur,
the front derailleur, you can, so with a 3x,
you can use those on 2x’s quite a lot of the time. You basically set your limit screws, and then you get a compatible 2x shifter instead of your 3x shifter, so it does mean you’ll
need to buy one of those. In some cases though, the 3x shifters have a little switch on and it’ll have a little graphic
on the base of the shifter, if it has this, and you literally turn it
and it turns into a 2x. Again that’s not on all shifters. So more than likely
you’ll need a 2x shifter. But back to that front derailleur, if you use the 3x one on a 2x, when you get those stops screwed in, it may well work adequately for you, but there’s a chance it might not work as well as a dedicated one ever would, and the reason for that is the profile of the cage itself was
designed to allow it to shift a whole other chainring, and if it’s not there to do that, basically it’s gonna have
like a little recess on there, that, basically, the
chain could slip down, basically derailing that chain. But I do think it does work, and I’m pretty sure I’ve
done that in the past. As for the actual tools you’ll need, gimme two seconds to spin ’round, and I’ll just get them for you. (air rushing) Okay, so, first up you’re gonna need an old-style Shimano bottom
bracket removal tool. More than likely, one
of your riding friends might still have one of these. And to use it you’ll either need a quarter-inch ratchet, or just a big old faithful spanner, an adjustable spanner, basically, to grip that and undo the
bottom bracket from the bike. But before you do that, you’re gonna need to remove the crank bolts on there. So a crank bolt spanner is what you need. You can use sockets for these of course, but the correct one for the
job, a nice 14 on there. And then you might find you need a block of wood and a mallet,
or a soft-ended mallet, just to tap the cranks off. And then all your usual
tools will be adequate for getting stuff back in place. Just regular Allen keys
for pulling cables through and adjusting them,
and that sort of thing. (bike wheel whirring) Alright, now it’s a transmission-based one from Javed Ameen Shaikh. I’m having a 10-speed
11-42 with 32T chainring. I think I need a slightly lower gear for climbs on my local trails. I don’t wanna spend too much money to convert my 10-speed to 11 or 12, so I’m thinking of using
the 28 or 30T chainring to reduce my drive ratio and get some extra torque when climbing. What do you think? Yeah, you can definitely do that. I would suggest going for a 30, though, ’cause a two tooth is quite
a noticeable difference. If you’re gonna have four, you might find you’re sort of under-geared
in other areas. Perhaps slightly less of an issue for you if your ride is more about being able to conquer that climb than
having a big enough gear to spin out on the way back down. But do take that in mind,
’cause it does affect things. If you go down too much, you’re really gonna lose a
lot of your higher gears. And of course, you’re gonna
get that slightly better climbing gear, but it is at an expense. Now another thing to take into account is the clearance on
your chainstay as well. It’s not like having
to fit a big chainring and wedge it in, the problem you have when going for a smaller one, is your chain is gonna be a lot closer to the chainstay of your bike as well. At least if your bike
has a fairly conventional double-diamond style design to the frame. And what that means is you
might get more chain rub on the chainstay, and you’re
gonna get more chain patter. So if it’s that close,
definitely wanna get some mastic tape or something to protect the paint on your chainstay, ’cause your bike’s gonna get a lot louder. And again, another thing
to take into account, by putting a smaller single
1x chainring on the front than you already have, you’re gonna end up with a little bit more chain. So you might wanna look at
taking a link or two out. But obviously leave yourself enough spare, so when you’re in that biggest gear, the derailleur is not too stretched out. Okay, so, Josh Wells. Hi Doddy, I’ve snapped four derailleurs in two and a half months, three of them on small jumps
and once whilst climbing. I’ve made sure the
chain length is correct, my hanger is straight and limit screws are adjusted correctly. What could be causing this? Sounds like you’ve got
the same disease as Blake, mate, I’ll tell ya that. He goes through RMX like
I go through chocolate. Something wrong with that
guy, the way he rides. – [Biker] Oopsie daisies. (Blake laughs nervously) Oopsie. – It’s really unlucky, is
what it is for starters, and I do feel sorry for you. There’s a few things in here. So correct chain length
can still be slightly long and if your chain is a
little on the long side, of course it’s gonna be a bit more baggy, and all it takes, in certain gears on certain boxes on certain chain lengths is the chain to catch at the
wrong time on the spokes, pull itself in, pull the
derailleur in and snap it. And so that is something that can happen. You’ve said that your
derailleur is adjusted properly. The limit screws and I’m guessing your B-tension screw is adjusted properly. If it’s not, that can have
an effect on things as well. Is it possible, perhaps,
your clutch is not on? So it’s flapping around
a bit more than usual and you’re riding quite extreme trails, and again that chain is enabling the lower cage to pop in. I guess another issue that it could be is your upper jockey or upper guide wheel, the bolts that holds it into the two cages is actually sheering, and
when that sheers basically if you don’t notice it
at the time it happens, it can actually go worse and pull the rest of the derailleur in. Now I know that Blake has
sheered off a couple of those and has ended up pulling the whole derailleur into the spokes, so there’s a slim chance it could be that. I know that some derailleurs
have had an issue where there wasn’t quite enough thread on that upper bolt that were catching and holding the jockey wheel in place, so that’s definitely worth checking. But I can’t actually think of many reasons why it happens other than incorrect setup, or if you’re just unlucky. If anyone out there has actually got any theories on this I’d love to know, because I’d love to stop having to fit new rig derailleurs
to Blake’s bike. So let us know in those
comments underneath and good luck. There’s another weekly
GMBN Tech clinic in a bag. Hopefully we’ve answered
some of your questions. If you’ve got questions, send
’em in to our email address that we showed at the
beginning of the show and of course, you can
add them in the comments below this very video. For a couple more great videos, click down here for
some money-saving hacks. Everyone likes to save a bit of money. And click down here for
our wheel-care video. That’s everything you
want to do to make sure your wheels stay in tip-top shape. As always, click on the globe to subscribe to GMBN Tech and give us a
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