Tire pressures
 

I'm wondering what is the max pressure I can safely use on Panaracer tires rated at 105psi when this site
http://www.precisiontandems.com/arttiresbymark.htm recommends over 140psi for our crew weight of 360#. If 140psi is too much for these tires, which ones would the experts here recommend to achieve this? (Our co-riders keep telling us our rear tire needs air, tho' I've put 110psi into it).
We have just taken delivery of a new Co-Motion Primera with the following upgrades: Bontrager tandem wheels, Windup X2 carbon fork, and Cane Creek Thudbuster ST stoker seatpost. What a difference in handling, speed and comfort compared with the Cannondale Los Dos we had previously. What I don't like, however, is the appearance of the Windup fork; I didn't realise that it would have a chrome crown which is a bit naff and cylindrical cross section. It's purely esthetic as the ride and control are great, but I expected a more conventional-looking carbon fork.
Thanks.

Don't like the looks of the WoundUp fork? Put on an other tandem rated c/f fork that suits you better. . . we use an Alpha Q X-2 with a d/a brake (much lighter and perhaps a bit more pleasing as far as aesthetics go to some discerning eyes).
Tire pressure: run the pressure listed on the tires . . . (don't say we said so, but boost it up another 10 lbs.). We run Maxxis 120 lb tires with kevlar/folding bead.
Your experience/results may vary from ours.

I agree. Riding with too little air in tyres is worse than too much as you will get punctures, the tyre wears and the ride is soggy.

The reason manufacturers post advice on how many psi to run is because the tyre pressure pushes the rim walls apart, and once the rim walls are non-vertical, hitting something could make them bend, resulting in tyre failure. However, manufacturers test these things under extreme conditions, including a margin of error for over-inflation, force of a heavy rider or riders hitting large lumps and a well worn rim. In my opinion this means that if you avoid these conditions, putting a bit more air in the tyre is unlikely to cause a failure.

The other point to note is that the tyre height has as much influence on the force on the rim as anything else. Reason for this is that if you calculate hoop stress (imagine slicing the wheel in half down the centre line of the tyre, force on the rim = 1/2 pressure x area, where area is the height from the rim well to the inside of the tyre x the rim circumference. 1/2 is included because the tyre itself bears half the stress). This means that running a lower profile (i.e. normal racing tyre) than a large balloon tyre at the same pressure will mean less stress, and is therefore safer.

I (and obviously a lot of other people too) used to run 150psi on my continental clinchers (18 or 20mm, so practically rubber bands) in the days before rim manufacturers posted safety advice on how many psi to run and never had any problems.

Bontrager's Web site and owner's manuals don't provide any information on rim bead width or tire size/pressure ratings so I would be hesitant to put 140psi into a 28mm tire on a Bontrager rim without first checking with Co-Motion or Bontrager to verify max psi for the various tire sizes.

That said, I'd suggest that you could safely go to 115 lbs and then again to 120 psi and see how that works and looks; there should be a slight bulge in the rear tire when you and your stoker put your weight on the tandem. As a rough eye-ball gauge, if there is no tire deflection (bulge) when a team's weight is placed on a tandem, the rear tire is over-inflated. If the rear tire deflects to 1/2 of its unweighted height, it's under-inflated. Front tires tend to be inflated to the same psi as the rear (force of habit?) and also tend to be over-inflated as a result.

Note: If your co-riders are on single bikes with tires inflated to their max psi, chances are they're probably used to seeing tires that have NO sidewall bulges which is actually indicative of an over-inflated tire -- very common with roadies (myself included). Tire pressure is very subjective; we're a 280lb team and I prefer our tires to be over-inflated. We run Vredestein 700x23 & 700x25 tires rated for very high pressure (135-145psi) on narrow rims (Velocity Deep-V) that are well-matched to the narrow, high-pressure tires and have done so for many, many years.

My counsel is to do some experimentation and see what works best for you. If you aren't getting a bunch of pinch flats and the ride quality is to your and your stoker's liking, then you're tire pressure is probably OK. If you find you are getting pinch flats or that the ride is spongy, add 5 lbs of air and see if that corrects it. At the high end, if you get lots of puncture flats or tire cuts (road debris driven into your tires) or find the ride harsh, drop 5lbs of air out of your tires and re-evaluate. You might also try experimenting with a different tire such as a Continental 700x28 Gatorskin just to see how that compares. I find that some tires simply work better for certain teams than others. Again, trial and error.

For more information on tire pressure, be sure to visit this site: http://www.sheldonbrown.com/tires.html#pressure

I'm not a fan of the look either, but the fork itself is well matched for Co-Motion's tandems and a bit more aggressive than their stock steel forks. Moreover, they are very robust, hence the great handling and control. The True Temper fork, while a good fork (I have one on each of our tandems) comes with some limitations: 1) they're not as stiff as the Wound-Up; 2) they're shorter than most tandem forks by nearly 2cm which skews the rake numbers since the head tube angle of a stock tandem not built for that fork ends up being steeper and the front bottom bracket ends up being lower; and 3) the largest size front tire you can use is 25mm. The Reynolds Ouzo Pro while very robust is still only available with a 1.25" steerer and 55mm of rake; perfect for a Santana but not compatible with any other stock tandem as everyone else uses 1.125" headtubes. Bottom Line: You may need to get used to how it looks because the alternatives are functionally not viable or "better".

You don't state what size tires you are running. Are the tires to small? Our team weight is about 10lbs more than yours. I have Conti 28's on the tandem and inflate them to 125 psi. If you are running 23's or 25's I would say the tires are too small for your team weight.

I assumed Co-Motion's spec tires for the Primera was the one he is referring to, i.e., Panaracer Pasela 700x28 which coincidentally carries a recommended psi of 105

The tire that comes on the Supremo/Robusta with the OEM Rolf Prima Vigor wheelset is the Michelin ProRace 700x25

<<I assumed Co-Motion's spec tires for the Primera was the one he is referring to, i.e., Panaracer Pasela 700x28 which>>

You are correct and tks for your advice.

140lbs sounds like a lot to me. Our team weight is right around 350. We run 700x26c tires at 110lbs, and I don't recall the last pinch flat.

I ran our 700X28s at 120psi last evening and they felt good.