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Tyre pressures and manufacturer recs confusion

T1beriousT1berious Posts: 438
edited November 2010 in MTB workshop & tech
Good Morning,

I've been having fun with tyres, lots of tyres. As we've reached the winter season and the weather has a more damp feel about it I've changed tyres.

I was running Maxxis Ignitor on the front and Maxxis Crossmark on the rear both 62a which I was amazingly happy with during the summer months, really fast rolling plenty of grip and once I let the pressures down no sliding at all.

Now I've switched to Maxxis Minion on the front and High Roller on the rear both 60a and 2.35 first impressions were good now I had them at the lowest recommended pressure 35psi and had a bit of slip but they were fast rolling and had bags of grip and felt planted in the stickier muddy sections of trail and great on wet rock.

The question I've got is are those recommended pressures on the tyres like just a guideline for legal reasons? As I'm pretty sure I'd run them a lot lower (so I can pinch them in my hand with a bit of effort) which for me tends to eradicate slip and give better traction, I'm pretty sure that's at the expense of rolling resistance.

Just wanted to hear other thoughts on what pressures people run.

Cheers

T1b

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    morning.

    have a read
    http://www.bikeradar.com/forum/viewtopic.php?t=12674161 and try the search button.

    this is a commonly covered topic.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Neily03Neily03 Posts: 295
    Just treat the minimum as a maximum and go from there. :wink:
  • konadawgkonadawg Posts: 447
    I tend to run the front at ~25psi max, but for loose conditions that can go down to 20 psi or less, possibly 15psi, there is a point however where you realise that you have overdone it and you get a lot of side slip.

    Rear, around ~35psi

    I'm speaking of wide tyres no less than a generous 2.35 (Maxxis equivalent, 2.5) however and they must be inherently rather resistant to pinch flats, for use as "do it all" everyday tyres I used to run the ornery Tioga Factory DH and found that they rarely pinched even on the heavy sharp rock we get a lot of here. They also have a Fat 66 (over 1kg each!) version with sidewalls so thick that 15 psi is plenty in the front!

    What I have found however is that better tyres will work well even without having to drop the pressure so much, having said that in the loose you really do need to drop it.
    Giant Reign X1
  • AnonymousAnonymous Posts: 79,667
    I run them at 35 which is minimum on my tyres. I'm often told they should be up in the 50+ range, but it's way too rock hard for getting over roots for my weight. Even 40 is too much.

    Seeing some videos and tutorials on the subject they need to be much softer for roots with less slippage. Looking at the videos and also of other riders I've been out with, I see their tyres squashing down heavily over roots. Mine at 35 to 40 aren't doing that and the result is I'm bouncing off them and slipping. I could take them down to 30 but that's below the minimum then.

    Alternative is to start eating lots of pies to add weight :D
  • .blitz.blitz Posts: 6,197
    T1berious wrote:
    The question I've got is are those recommended pressures on the tyres like just a guideline for legal reasons?
    In a nutshell, yes. The tyre will have been tested under a wide range of loads and conditions at that pressure but we are all different and ride different terrain on different bikes, so it is only a starting point.

    Really the best pressure is the pressure that suits you and your bike and where you ride. Too low will be like cycling in glue and you will be pinch-flatting all over than place; too high and you will be struggling for grip and pinging off rocks and roots. Try 5 psi adjustments up/down until you find a pressure you're happy with.
  • Cheers for the replies :)

    Yup, previously I was running them much lower and having no issues with roots but when running at 35 it was sliding big style. Think I'll go back to an ignitor on the front or get the "right" minion as the one I got was a downhill monster tyre. a bit heavy and a mare to get on the rim :)

    Cheers for the info and I'll be experimenting with pressures :)

    T1b
  • konadawgkonadawg Posts: 447
    Just remember you want the rear to have more air than the front, running the same front/rear does not make sense. You can afford the front to be far lower than what you may think is reasonable, don't be afraid to experiment, the difference on loose gravelly terrain will be amazing. Tyres I run at 20 have a rec'd min of 30, ignore. At 30 I'd be all over the place or rather flat on my back with a lot of time to ponder pressures... :shock: The front has less weight on it ordinarily and especially when climbing so there really is no issue with drag.
    Giant Reign X1
  • .blitz.blitz Posts: 6,197
    ^^ this is true. Getting the front to stick is more important than the back.
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