MTB tyre pressures

[europa]

The lad and I will be hitting the trails in the Shepherd's Hill National Park on monday (the joy of a public holiday). To celebrate, I've taken off the utterly worn slicks on my Diamondback Wildwood and fitted knobblies.

Oh okay, here's a piccy

and here's the story ... such as it is.

I went to my favourite lbs, the one that did the Europa's wheels and tyres, and dealt with a long suffering lad whom I've helped discover some of the more well hidden bits of old and unusual stock they have He's always been good but I could tell I was pushing his personal cycling envelope to new levels, so today, after buying the Europa's tyres and making him dig around for some oddball crank bolts, I then asked him about mtb tyres. Man did his eyes light up Turns out he doesn't own a car and spends all his spare time riding his mtb on anything that does not resemble a road.

Anyway, on his recommendation, the Diamondback now wears a set of Velociraptors

The question I didn't ask was, what pressure?
I'm guessing I'm looking at two figures so:
What pressure for the off road trails (probably soft)?
What pressure for exploring dirt roads (ie, hard gravel)?

Richard
btw, any advice on surviving on an mtb in the bush will be appreciated ... such as 'don't do it'

[Kev365428]

Morning Richard,

I'm no MTB expert, but my suggestion on presures would be -

For fire trails/hard gravel surfaces - firm pressure (say 50 psi)

For the softer, muddier type of track or sand - I'd reckon about 40 psi.

Couldn't be too different to tyre pressures in a 4WD, surely. But like I said, I'm no expert. (edit - I don't mean the pressures would be the same, but the concept of softer pressures for softer conditions vs harder pressures for harder conditions.)

Advice for surviving on a MTB - don't hit trees (did that once - the tree won ), stay sitting down when hill climbing - better traction, lower your seat a bit so that on steep downhills you can lift your butt over and past the seat so that your weight is over the back wheel. This helps braking and traction, but you need to practice this a bit to gain confidence. I'm sure you can figure out why.

Is it still raining in SA? Should be fun in the mud. Was thinking of taking my GT MTB out for a blast in the dirt today. After all the rain we've had in the past 24 hrs, should be nice and muddy.

Have a blast.

Kev.

[Kalgrm]

I also would not say I'm an expert, but MTB riding was all I did until I bought the 'bent in April, so I think I can offer advice here.

You didn't tell us the width of the tyres, so the answer won't be definitive. However, the rule of thumb is to have them as soft as you can without getting pinch flats. The variable you need to consider are the tyre width, your wieght, the terain you're riding in and the style of riding you intend to do (aggressive or not-so-aggressive).

I'm 80kg fully kitted out, plus my bike is 11kg. I don't ride aggressively (no drop-offs over about 40cm). I have my 2.1" Kenda Blue Groove (F) set to 32 PSI and the rear set to 34 PSI. I would go softer, but that's a good compromise between puncture prevention and speed. It also gives me excellent traction.

I realise that last comment might raise some eyebrows, so I'd better explain: when you are on dirt, softer tyres have less rolling resistance than hard tyres. The reason is that soft tyres will deform around stones and bumps, rather than try to propel the wheel, bike and rider upwards. Lots of little stones - all trying to lift the rider - are like lots of medium size hills: the more you can glide over them, the better. I will find the reference research for this statement some time later today, when I'm on a faster connection.

The other reasons for soft tyres are that you improve traction, since the tyre's footprint is enlarged, and you are better able to "float" over soft gravel rather than bog down in it.

I suggest you start at 35 psi in the front and 38 psi in the rear, and let them down a little at a time when you are out there. When you start to hit the rims, put a few pounds back into them to stop flats and you should have found the right pressure for you.

Cheers,
Graeme

[Kalgrm]

Here you go:

http://schwalbetires.com/tech_info/rolling_resistance

and

http://schwalbetires.com/wider_faster_page

It sounds counter-intuitive, but softer, wider tyres are much better off road when it comes to rolling resistance. The research cited above also indicates the same is true for on-road riding, but then wind resistance rears its ugly head .....

I forgot to mention above that other factors also affect your optimum tyre pressure like the suppleness of the walls and the width of the rim, but that's not going to affect your choice of pressure on this ride - you already own the rims and tyres.

Cheers,
Graeme

[europa]

Well, I'm a comfortable 105kg, so I might go for 40 in the rear and 35 at the front.

Tyre size - 47/52 - okay, what does that mean - height and width?

Interesting what you say about lower rolling resistance for low pressures. So many things to learn. Great ain't it (I admit it, I'm a junkie, I like to learn stuff about lots of stuff and am always keen to pick up a new skill)

Thanks

Richard

[stryker84]

http://schwalbetires.com/wider_faster_page

Refreshing isn't it, knowing exactly what's on the page from the link.

sorry, it amused me.

[Kalgrm]

The tyre size will appear something like 26x2.1. And you got some good tyres there - velociraptors have a great reputation.

I took your weight into consideration when I made the recommendation of 35 /38, but it's your skin. The ride will be very twitchy at 40 psi, and even 38 will not be ideal - you need to drop it from there until you feel you will hit those rims.

I ride more aggressively than I expect you will this weekend, so I actually have pretty high pressure in my tyres. I would expect that you'd find your ideal pressure to be around 32/34 psi also, even though you weigh more than I do. When I weighed 105kg, my pressure was pretty good at about 36 on the rear.

Most "serious" MTB riders run Stans No-Tubes or other tubeless systems so they can get their pressures down to 22 to 25 psi for XC riding.

Cheers,
Graeme

[Kalgrm]

And you got some good tyres there - velociraptors have a great reputation.

Actually - I just remembered: Velociraptors have a front tyre and a rear tyre design. Are both your tyres the same tread pattern or are they markedly different?

The front one has triangular knobs in the middle of the tread and the rear has rectangular knobs running across the middle of the tread. I hope you got a pair instead of "old stock".

Cheers,
Graeme

[europa]

No, I got the front and the rear - very different treads, and reversible for different conditions.

So the pressures come down even more - I hadn't realised you'd accounted for my weight. I would not have thought of running them so low and no, I will not be aggressive on the track - terrified maybe, but not aggressive, exhausted probably, but not aggressive

Richard

[Andrew69]

Great info in this thread guys!
Thanks!

[europa]

The photo at the top has been changed - it's hosted on my website and when I changed that one, the photo here changed as well

But that's how she'll be tackling the mud on monday ... unless you lot tell me to change something. Gone are the slicks, now she's wearing her new tyres, tyres pumped to about 34/38 - bit hard to tell exactly with my guage. As you can see, she's lost the mudguards and the photo now shows the higher bars.

I took her for a quick spin and boy, nobblies are noisy aren't they. She's a heavy old brute of a bike but very comfy.

Now I can go back to fiddling with the Europa

Richard

[Gishalo]

Its probably true about rolling resistance, I find my mtb tyres wear out in the side walls before the tread. I do ride pretty firm tyres though, mainly due to the firm surface on the trails up here. Not many stones and I find firm pressure digs in better.

Tested this by starting off with high pressure and working my way down in pressure over same track.

But it really depends on what you want out of your ride, speed , comfort ? I just cant stand flats, so I wont risk a pinch flat.

[Mulger bill]

The lad and I will be hitting the trails in the Shepherd's Hill National Park on monday...
Richard

Goodonya mate! Knew the woods would call
The tyre choice will be fine, those young fellers know the local conditions Treat those pressures as a good point to start experimenting.

Keep the body relaxed on the bike, bend the elbows outwards for more control and comfort, don't look where you don't want to go.

Apart from that, ride till it hurts, get muddy and have the third biggest blast in your life

Shaun

[europa]

Thanks Shaun. It's been awhile coming, but that's more a function of my life - while my son lives with me, on the weekends I don't have my daughter, I don't have him either I'd begun to suspect that we wouldn't get on the dirt together until the next school holidays, but a long weekend has given us the opportunity to get out on the mud. Fortunately, he'll be riding his bmx ... and he'll have one of his ratbag mates with us (also on a bmx) ... so I've got an outside chance of putting in a reasonable show

I was thinking about it today, and I reckon this'll be my first time mountain biking. The mtb was invented after I discovered bikes and while I've ridden road bikes on dirt tracks, this'll be the first time I've ridden an mtb on a genuine dirt track

Richard
see, you can teach old dogs new tricks ... just don't expect them to learn them particularly well

[mikesbytes]

Thanks Shaun. It's been awhile coming, but that's more a function of my life - while my son lives with me, on the weekends I don't have my daughter, I don't have him either I'd begun to suspect that we wouldn't get on the dirt together until the next school holidays, but a long weekend has given us the opportunity to get out on the mud. Fortunately, he'll be riding his bmx ... and he'll have one of his ratbag mates with us (also on a bmx) ... so I've got an outside chance of putting in a reasonable show

I was thinking about it today, and I reckon this'll be my first time mountain biking. The mtb was invented after I discovered bikes and while I've ridden road bikes on dirt tracks, this'll be the first time I've ridden an mtb on a genuine dirt track

Richard
see, you can teach old dogs new tricks ... just don't expect them to learn them particularly well

I've ridden road bikes (27"ers) on dirt track pre mountain bike days too !!!

Cyclecross would probably be the modern equivalent ?

[Kalgrm]

Ummm, Richard, you're in trouble. Not one but two kids on their BMXs and you think you've got half a chance? These two are out to teach you a lesson in humility, no doubt about it. You're going to need all that rat-cunning to save face, I'm sorry to say. I suggest a concealed blade to slash tyres - that should slow them down a bit!

Have fun, keep loose and stand as often as you can (it will save your posterior from a rough ride and let you shift weight around as needed). I took up MTB riding for the first time at the age of 39, after more than a decade away from any type of riding. I became obsessed with it and learnt much more than I had even considered existed in the sport before I started. Old dogs can learn new tricks, and do so very well.

Lastly, don't try to do more than you feel comfortable with. Those kids will be jumping stuff (most likely) and you should not even think about doing stunts on this first ride out. Keep the rubber side down.

Cheers,
Graeme

[europa]

Hmm. I'm 50. It's after 10pm on the night before and the lad's asleep in bed while I'm what is quaintly termed 'pithed' on the red vino. You're not suggesting I'm in trouble are you?

Richard

[Gishalo]

MMM the old red vino petrol ? My money will be on the kids for the first little bit, but i think you will wear them down. Have a good one. Sun is up enough now so I am heading out to enjoy my monday off.

[heavymetal]

Run the tyres with 0 psi air pressure. Remove the tubes and stuff the tyres with spinifex. This will give you great off road handling, and also handles sand quite well.

Don't forget to tie your water bottles into the cage so they don't bounce out on rough surfaces, and make sure you carry a compass.

Kev.

[Mulger bill]

So Richard, how did it go....

Bah, had it all worked out for today...set the alarm for 0745, the GLW gets home about 0810, a cuppa, a bit of gentle conversation while the kids snore, then out to try beating Denis distance record, ppppppppffttttt. Bloody Rain!

Nearly dry now, but at least -11DT I better rug up.

Shaun

[europa]

It all went well. Flat muddy roads, steep muddy hills, single lane muddy tracks along side of creek and on side of hill, single lane muddy tracks across creeks and gullies ... oh, and a lot of it was muddy. Used the full range of gears. The hills echoed to the sound of screaming brakes (yes, I used the brakes a lot more than necessary but at my age, cowardice is the better part of valour ). Didn't fall off though that wasn't through lack of trying. I went everywhere the lad and his mate went on their bmx bikes

'Twas a lot of fun and I handled it a lot better than I expected. A ton of grip from those tyres and I'm guessing that made all the difference - I'm used to bikes sliding around on mud (only ever ridden road bikes off road before). Sadly, I'm fighting knee problems at the moment (tendonitis by the feel of it - hence my recent interest in bike fitting). The first half hour went without a problem but then the knees started to hurt so I called it quits and sat in the car listening to an audio book while the boys went out for another half hour run.

And the bike is MUDDY ... so are my shoes, my shorts, my shirt, my helmet, my hair, my legs, my ...

Richard

[europa]

And in keeping with 'if there's no photo it didn't happen', here's a piccy. Not as dramatic as I thought it'd be, but dat's hard earned dirt there ... and riding through a couple of puddles in the carpark probably helped clean things as well



Richard

[Mulger bill]

That's the way!

Mate, I'm stoked you had a good time, pity 'bout the knee tho'.

Nice work keeping up with the lad, youthful invulnerability is the biggest thing they've got going for them.

Shaun