Henry: How do we find our perfect tire pressure? Well, like a lot of things in mountain biking,
it's the result of trial and error. Today, we've come to the woods. We're going to try
some different tire pressures with some different rim widths as well as even some tire inserts
to find out the pitfalls and highlights of each setup.
[music] [background noise]
Henry: What I want to do is show a range of different combinations and situations. The
things I will be comparing will be tire casing pressure, rim width, and experimenting with
inserts. I'm going to keep the same tire on the front on the same FSA rim. For your reference,
my personal details are, I weigh 82 kilograms. I like long walks on the beach and the music
of Barry Manilow. Currently within cycling, irrespective of
discipline, there tends to be a trend for wider rims, so rims that have a larger internal
diameter are more favorable. Today, I will be comparing an XC rim, a Mavic with a 23mm
internal diameter, and this FSA Enduro rim which has a 29mm internal diameter. Rims have
got wider for a couple of reasons. A lot of it is to do with tire profile and the way
our tires interact with the ground. A wider rim can often give more of a shoulder which
you can lean against in turns. It also means you can run lower pressure as
it spreads the load laterally along the wheel. Another point to note here. Sometimes, larger
amounts of internal diameter can come at the cost of weight. It's no surprise to see most
companies with their cross-country rims going narrower than the sometimes 30 millimeters
plus of Enduro and downhill wheelsets. Often XC tires don't come with a large shoulder
like this aggressive Enduro tire. The tire and rim need to work in harmony with one another.
Please, also bear in mind that the Mavic rim I'm using today really wasn't intended for
this sort of riding. It was just the narrowest rim I had in the house. For this comparison,
I want you to imagine that you've found your tire of choice. In this case, for me, it is
a Martello 2.4, 29-inch in trail casing and you're very happy to have it fitted on the
back. This video is about maximizing the performance of that tire with other setup changes.
I'm going to be riding different sections. Firstly, a turn that will try and deform the
tire laterally and finally a rocky section trail that will put a high load into the tire
in the form of square hits and compression spikes.
[music] Henry: We've just spent a little while riding
the same turn in a repeatable manner. Although I'm not sure how much it will show up on video,
the wheels really did feel different in terms of the amount of stability and support they
offered especially at the lower pressures. That got us thinking. Can a tire insert help
us mimic the feel of a wider rim by offering more stability to the narrower rim?
I think this is really interesting. Not least, because you might benefit all over your riding.
Actually, for me, it's quite hard to include an extreme situation in a repeatable circumstance.
What I mean by that is you're probably thankful for higher pressures, wider rims, and something
like a tire insert when you least expect it and things get a little bit rowdier than you
intended. We've had a morning rolling around the woods
and testing out our tires. What have we found out? I think what's really interesting with
the tires and the way we set them up and our wheels included is they're often judged by
their worst results so when they fail. That occasion might only happen once a ride, but
when it does happen it can be disastrous. You're always having to plan for the worst-case
scenario. I think what was really interesting for me
is actually in my quest to find the perfect tire pressure, in the turns, there was huge
amounts of instability on the lower pressures. That might not necessarily come across in
the video, but it was something that it made me feel I didn't have that larger element
of control and there was certainly an element of unpredictability in the turns.
Actually, when rolling the square hits with our very high-tech stick method, it actually
revealed that the lower pressures deformed so much better that it was a lot more comfortable.
Tires like our suspension need to be bottomed out on occasion but not too often. Because
what's happening is if you run your tire so hard that it can never deform, well then you're
basically giving away grip for free. Similarly, if it's deforming too much and on a high-velocity
impact, it could slice the tire or damage the rim.
You want something that's getting close to bottoming out without doing just that. I think
the thing I noticed most of all in terms of my comparison from the two rim widths was
actually how good modern trail tires are coping with those deforming loads. In the turns,
definitely, the wider rim did feel a bit more stable but it wasn't night and day. That's
where tire inserts come in because they enable you to run lower pressures without risking
you ruining a ride or worse yet bottoming out and destroying a rim.
What that means is there's a nice chamber at the top of the tire that is supple and
grippy, but if there's any square hits they won't go straight to the rim. What is the
perfect tire pressure for me? Well, on some trail casing tires such as these, on a rim
like the FSA which is a 29mm internal, I'd probably hover around the 25 psi for the back
and maybe as low as 23 for the front. If I was to go narrower, would my tire pressures
go up? Absolutely. If only for that once in a blue moon occasion where I hit a rock a
bit faster than I was anticipating or I'm unable to weight the bike. Like I said, that
might only happen once a ride but if it does it's enough to ruin the ride. Our tire pressures
have to anticipate such an occasion. With the ongoing conversation about wider rims,
how important is that to your everyday trail rider?
Well, for me, in my personal opinion and experience, reasonably so I think for an aggressive trail
bike such as this with quite an aggressive tire with a big shoulder on it, I would tend
to lean to the slightly wider side of things. This is for a couple of reasons. Like I said,
the stability is absolutely massive especially when you're pushing load through the bike.
A big one as well means I can get the supple feeling of lower pressures thanks to a larger
contact patch. This is without then having a few problems should the terrain get a bit
choppy. I know from my personal experience that if
I do run lower pressures, anything sub 28, on what would be a more old-school or narrow
rim I'm going to be burping and I'm going to be puncturing, damaging the tire which
not only hurts my ride but it hurts my wallet too. Both things have to be carefully managed.
I think it's also worth noting that we haven't even got into climbing today and all the traction
benefits that are to be had from running lower pressures there.
I never thought I'd get tired of hitting a loamy turn, but I have to admit even I was
thinking, "Hmm, 40 times is enough." Thank you very much for watching. Please don't forget
to like and subscribe and get in the comments below. What do you think is the perfect tire
pressure for you and what do you think of rims getting wider? That's what I'm going
to stick with. What do you think of rims getting wider? Thanks, guys, and we'll see you next
time.