UST and High PSI

DCR00

Afternoon all

New wheels arrive tomorrow - Red Metal 3

Wheels are UST compatible, so im considering whether to go for some new UST tyres, or to run my existing tyres (Conti Twister Supersonics)

Now ive read all the blurb about being able to run UST at a lower pressure and that running non-UST tyres at a lower pressure could be an issue to due tyre sidewall strength

However, i usually run my current tyres at 60psi, so assuming i can get them on ok, do we think that my current non-UST tyres will run fine on the Fulcrum rims ?

Also, given that i use the supersonic version, will the sealant eat throuygh them in no time ?

Cheers

DCR

milfredo

60psi is high!!

I run non ust tyres as tubless at 30psi max and have no issues with the sidewalls being flexy. At 15psi was a different story when I forgot to check the pressure and it felt like the rear end of my bike was going to fall off.

MountainMonster

Why do you run them so high? I had mine set to about 36 or so before, and it felt extremely uncomfortable on even slight gravel.

Thewaylander

I ride with tubes and normally hit 32 on the back 30 up front for long rides, and on the weekend in the mud on uplift was at about 20psi each..

60 psi is almost road pressure.

slimboyjim

If you want to run tubeless you'll need a conversion kit or do a ghetto tubeless effort for non Ust tyres. You don't mention if this is your intention. It can be pretty hard getting a seal at the best of times (although I've only used ghetto and not a proper Ust setup) so I'd always recommend sealant. I'd carry on with the tyres and tubes you've got until it's time to get new tyres - then pick up some Ust ones (and some sealant).

If you are wanting to try tubeless sooner then I'd look at a ghetto conversion to keep it cheap but be aware that results can be mixed depending on the tyre/rim combination in my experience. Search the forum for how to do it...

DCR00

Run them high to keep rolling resistance low. Deliberately use a thin tyre (1.9) and the supersonic version to keep the weight low. If i can get this to work, then ill shave a further 350g from the weight of the new wheelset.

Twisters are almost road tyres anyway, having minimal tread in the centre of the tyre and some knobbly bits on the outside for grip when cornering

I have some sealant from my LBS. He seemed to think it couldnt be done having tried it himself a few years ago. However, im still gonna give it a go.

DCR00

slimboyjim wrote:

If you want to run tubeless you'll need a conversion kit or do a ghetto tubeless effort for non Ust tyres. You don't mention if this is your intention. It can be pretty hard getting a seal at the best of times (although I've only used ghetto and not a proper Ust setup) so I'd always recommend sealant. I'd carry on with the tyres and tubes you've got until it's time to get new tyres - then pick up some Ust ones (and some sealant).

If you are wanting to try tubeless sooner then I'd look at a ghetto conversion to keep it cheap but be aware that results can be mixed depending on the tyre/rim combination in my experience. Search the forum for how to do it...

my new wheels are UST tho ? so i guess its a half ghetto set up

if i cant get a decent seal, then ill default back to a tube setup until i need new tyres

danlikesbikes

60psi sounds quite high - I run 35 at the most and either a 1.8 or 1.9 and mine run pretty damm fast but each to their own I guess.

Sealant is going to be a must though - loads of different brands out there for you to look at plus if your interested in home made look here http://www.bikeradar.com/forum/viewtopic.php?p=16092261

jairaj

unless you use all UST or tubeless ready products the results are unknown and changes from setup to setup.

Normal Maxxis tyres work well with UST or tubeless ready rims don't know about yours. Giving it a go is the only way to find out.

If that fails to work then going for a tubeless ready tyre instead of a UST tyre will help save some weight. Tubeless ready has the same beam profile as UST but doesn't have the extra air tight layer that makes UST tyres slighter heavier.

Also not sure what you mean by sealant eating the tyre? As far as I know sealants aren't corrosive to tyres? In fact they do the opposite, they seal up any holes and make the tyres less porous.

Also are you actually using your mountain bike off road? If so, you maybe increasing the rolling resistance by running such a high pressure. Have a read of Sheldon Browns website on this subject.

DCR00

jairaj wrote:

unless you use all UST or tubeless ready products the results are unknown and changes from setup to setup.

Normal Maxxis tyres work well with UST or tubeless ready rims don't know about yours. Giving it a go is the only way to find out.

If that fails to work then going for a tubeless ready tyre instead of a UST tyre will help save some weight. Tubeless ready has the same beam profile as UST but doesn't have the extra air tight layer that makes UST tyres slighter heavier.

Also not sure what you mean by sealant eating the tyre? As far as I know sealants aren't corrosive to tyres? In fact they do the opposite, they seal up any holes and make the tyres less porous.

Also are you actually using your mountain bike off road? If so, you maybe increasing the rolling resistance by running such a high pressure. Have a read of Sheldon Browns website on this subject.

from Sheldon browns website "Small cross section tires experience more deformation than a large cross section tire and therefore, should have greater rolling resistance, but they generally do not, because large and small cross section tires are not identical in other respects. Large tires nearly always have thicker tread and often use heavier tubes, besides having thicker casings. For these reasons, smaller tire usually have lower rolling resistance rather than from the smaller contact patch to which it is often attributed."

Anonymous

I just want to add to the echo chamber here... 60 PSI? holy crap.

Having your tyre deform over small obstacles is a GOOD thing, it means you lose less energy rising up and over them.

DCR00

yeehaamcgee wrote:

I just want to add to the echo chamber here... 60 PSI? holy crap.

Having your tyre deform over small obstacles is a GOOD thing, it means you lose less energy rising up and over them.

80% of my ride is relatively smooth trail and road i.e. no obstacles at all. If it wasnt for a few sections of trail that require some level of grip, then i would run slicks

So surely having a harder tyre is better as this reduces the drag from the amount of rubber in contact with the ground ?

supersonic

To a point. Tyres have optimum pressures for rolling resistance that depend on your weight, weight bias, tyre type and ground surface.

On flat surfaces this optimum will be a little higher, but extra PSI on top of that doesn't make that much difference really.

Barteos

I normally put 55-65PSI in 700x35mm tyres (tubeless conversion) on my road bike.
Any more than that and I don't get any faster, just less comfortable (based on the powermeter data).

robertpb

I've never had a tyre sidewall issue in 26 years and I run pressures between 21-26psi.

A friend of mine has run 15psi in his MTB tyres for more than 30 years without a problem, though he always uses a heavy walled tyre and heavy tubes.

Under race conditions XC with UST tyres sub 29psi is normal.