tire and tube questions

melb2ib

HI

I have a cannondale bad boy 29er, under the spec online is say it has Schwalbe Big Apple 29X2.0 tires, however on the physical tire it say 28 x 2.0.

I recently put in new tube that is 29' and wide of 1.9 x 2.35, does this mean it should fit any tire within those widths?

Should i get one that's 1.75 x 2.5 as this would be less stretching for the tube? (less likely of puncture?) also should i be worried i put a 29' tube under and 28' wheel as I am keen to inflate to the full 70 psi as listed on tire but don't want to blow tube.

One final thing, the rims are Maddux C3 Urban 29" , 32 hole, I cannot find full spec on their width online. But I guessing its 2'. What kind of range does that give me in tires and tubes, down the line I am keen to get bigger tires.

Thanks, and sorry if these questions were stupid, im new to cycling.

Tenzor07

This should help, have a read: www.sheldonbrown.com/tire-sizing.html

mirv

70psi in a 29 x 2.0" tire? That's madness. You'll get much more comfort at a lower pressure unless you're quite heavy and need the pressure to avoid pinch flats. You won't get any more speed out of them after 40psi I reckon.

With a total bike + rider weight of 75kg I run 42 psi front and 47 psi rear on Vittoria Randonneur Hypers (700x35c), which is the same as 29 x 1.4" - far narrower than yours. I reckon you could easily run them under 40 psi without getting any rolling resistance if you're the same weight as me, probably somewhere in the mid 30s.

Regarding the tube sizes, you'll find that it says 1.9 - 2.35, rather than 1.9 x 2.35. You're right in assuming that it should fit any size within that range. People often use undersized tubes to save weight or give them a smoother ride.

melb2ib

Thanks Tenzor

according to Georg Boeger, im well and trully over the recommended width as it is. Thanks grand, ill stick with a 2' wide tire from now on

Any advise on the tube stretching question? And anyone else blew tubes when pumping to fill PSI?

mirv

Regarding blowing the tubes - it's more likely to do with the rim/tyre interface and your pumping to 70psi in what is a very wide tire, than it is to do with the tubes stretching. Almost no-one would usually run a 29x2.0" tire at 70 psi - as you'll lose all the benefit of having all the suspension the size of the tyre allows, and you'll likely blow the tyre off the rim (and then subsequently explode the tube after the tyre is blown off the rim).

melb2ib

Hey Mirv

Thanks for your post, that's the PSI it says on tire. The lad in shop told me 100 PSI and i blew a tube !

Im slightly heavier that you, 98KG (all muscle honest lol), do you recommend pumping to about 40, then sitting on bike and looking at back wheel at give it more air if it looks like its folding slightly at base? but leaving front at say 35?

Apologies, you are right, it was 1.9 - 2.35. So getting one with a larger range would be heavier, but would getting one with smaller range make the tube more likely to puncture as it stretched to the max? or is it all about good tire and correct PSI to avoid punctures?

thanks again for your help

ford2600

Your weight and tire, 36 front 39 rear.
For 2" 29" wheel.

40 is good

mirv

The tube isn't going to be 'stretched' any more when it is at 40psi than when it is at 200psi. It conforms to the shape of the tyre, which is relatively fixed in size. What is happening is that when there is 70psi in the 29x2.0" tyre is that the tyre is being pushed outwards and off the rim. When the tyre pops off the rim, it leaves a gap for the tube sneak out a bit, blister outwards and burst.

You'll burst a tube at 30psi if the tyre pops off the rim and leaves a gap for the tube to sneak out. So it's absolutely nothing to do with the tube, and entirely to do with the pressure you're running at and the interface between the rim and the tyre.

If you're running a 1.9-2.35 in a 2.00 then you're already playing it quite safe so I wouldn't worry about that. Maybe pump them to about 40-45 front and 45-50 rear, and then seeing how it rides and if it feels draggy - you should see a little bit of squish when you mount the bike. It's hard to describe how soft you should be running them without seeing it in person. Move up/down by 5psi at a time until you're happy.

melb2ib

Thanks Mirv and Ford2600

Currently have just under 35 in the front and 40 in the back. Will have to bring it for a spin and see how it goes.

Great advise on the tubes, I think ill stick to the ones with the smallest range I can get from now on so.

Really appreciate it

mirv

Enjoy, report back with your findings so if anyone searches for something similar they'll have a good thread waiting for em.

melb2ib

will do

ford2600

http://www.vittoria.com/tech/recom-tyre-pressure/

One of many online

mirv

Not to be *that guy* but the vittoria one is particularly useless for commuters as it doesn't account for tire width/volume, only for casing tpi. It pretty much assumes you're running 700x23 slicks, at least in the road bit. The mtb bit is a little better though.

melb2ib

Great site ford2600

cheers,
I can readjust as I lose weight or eat more lol

melb2ib

Hey
Just reporting back, I felt a bit of a drag, so I put a bit more in each wheel, 43 in front, 47 in back.
Will see how it goes.

Ive one final question, the bike has disk breaks...is it normal for the disks to be rubbing off the break pads? I can hear it when i spin front or back wheel?
thanks