|Am I the only one who....||tirider|
Sep 8, 2003 3:07 PM
|...Runs different tire pressures on the front and rear tires? I picked this up from my mountain biking days. There it was always preferable to have the rear tire break loose first on loose descents (via a bit more pressure than the front) and I found the extra benefit of a bit more comfort and steering control with lower front pressure. Now on road bikes I usually run around 105-110 lbs in the front tire and 120 in the rear (depending on the tires). It also seems a bit more comfortable this way. This makes sense to me since the weight isn't distributed evenly on a road bike. I'd guess it's around 40/60 percent, front/rear, depending on the setup. When I go back to the even pressures, I can tell the difference with comfort and the front end feels a bit squirrely comparatively. Any thoughts?|
Sep 8, 2003 3:49 PM
|I run my front about 10 psi less than the rear because of the weight distribution issue as well.
Also, "Uncle Al" of RoadBikeRider.com fame suggests doing this, so I'm confident you're not the only one!
|Thanks to "Uncle Al" I have less flats. 100 front, 105 rear tire||Tig|
Sep 8, 2003 4:29 PM
|I don't trust pump gauges completely, so instead of Al's recommendation of 95 psi in front, 100 psi in rear tire, I stick with 100/105. I've been running this pressure for over a year and I have reduced flats by more than 1/2!
Al is 225 pounds and gets away with the lower pressure, so I sure can at 135 lbs. I gain better traction, a more comfortable ride, and far fewer flats now. I gain a near impossible to measure amount of rolling resistance.
|Traction revisited: This is soooo true (story)...||Spunout|
Sep 9, 2003 7:53 AM
|Last weekend's racing saw me around a 42km/h turn in choppy pavement. You know, sortof like marbles embedded over three poor attempts at re-capping the road.
A few times I found myself a few feet further out the line after a slide, but stayed upright all the way. Not so for a few of my competitors. I was using Michelin Pro Race(dark blue) at 110R/105F and had alot of faith in my grip. I race at 160lbs.
|Fairly common practice||Kerry Irons|
Sep 8, 2003 4:01 PM
|Though there's not a huge point to it. You might consider knocking 10 psi off both front and rear to improve handling, traction in corners, and comfort. You don't state your weight, but if you need to pump to 120 psi to avoid pinch flats, then you need wider tires. Otherwise, 100-110 is the most you need to get a good balance of handling, rolling resistance, and comfort. I can't see how the front end would get squirrelly by reducing the rear pressure to 110, but I'm guessing you mean you pumped the front to 120. You'll note that Michelin recommends 110 psi max for their racing tires, and that's not because they're worried about blowing the tires off the rim.|
Sep 8, 2003 5:05 PM
|Michelin recommended a maximum of 116 psi for the last year of the Axial Pro and for the newer Pro Race. I run 120 in the rear and 110 in the front.
|Fairly common practice||tirider|
Sep 8, 2003 6:12 PM
|I'm using Veloflex Pave tires at the moment (which I absolutely love and believe have the closest feel to sew ups) and they feel best to me at 120 lbs on the rear. This has nothing to do with my concern for pinch flats. I weigh about 165- 175lbs depending on the season. I've never run 120 lbs on a front tire, but what I meant is that when I have equal pressure, front and rear, regardless of the pressure, it feels a bit more squirrely (not the best word) compared to when I drop the pressure a bit. I find the Veloflex tires to feel the best with around 10 lbs less in the front. With Michelins, I never run more than 110 lbs.... GP3000s 110-115 lbs.|
|Not true: Michelin Pro Race rec. press. 4 my weight: 120psi nm||BergMann|
Sep 8, 2003 6:24 PM
|Surprising coincidence...and about the 40/60?||mk_42|
Sep 8, 2003 4:48 PM
|I just wrote a post about weight distribution (wrote it before I saw your post). You get the award for having the first real number about weight distribution I've ever seen. Do you have any reason for guessing 40/60?
|Real number depends on geometry and set up||Kerry Irons|
Sep 8, 2003 5:13 PM
|but is much closer to 45/55. It's easy to measure for your setup: put your back wheel on a bathroom scale and your front wheel on a 2x4 and read the weight. Switch front and rear and read the weight. While the bathroom scale is not all that accurate, it will give you a pretty good fix on your actual weight distribution.|
|Surprising coincidence...and about the 40/60?||10speedfiend|
Sep 8, 2003 5:15 PM
|Put front tire on one bathroom scale and rear on another and sit on your bike as you ride. Note the weights. Aprox 40/60 or 129lbs rear and 86.5lbs up front for my 26lb bike and 190lb carcass.
|Kieth Bontrager||off roadie|
Sep 8, 2003 6:12 PM
|I forget where I read it, but one of Kith's website rants mentions the 40/60 ratio, afiak. It may be more true for MTB's than road bike, especially in terms of impacts, as you can loft the front wheel and it frequently has suspension.
This definatley supports having less or thinner spokes on the front wheel. I would go for thinner- less spokes means a longer span, and flex increases geometrically with span. In practice, I think rears ideally need a combination of slightly thicker spokes, slightly more of them, and slightly heavier rims. A 15% increase in the strength of each might add up about right.
|I'm no wheel expert, but...||Ray Sachs|
Sep 9, 2003 4:48 AM
|it's not just the added weight on the rear wheel, it's also the weakening effect of dish and the power that's transmitted through the drivetrain to the rear wheel. In addition to carrying less weight on an inherantly stronger wheel (no dish), the front wheel also seems to have a much more passive, reactionary job than the rear.
|Surprising coincidence...and about the 40/60?||tirider|
Sep 8, 2003 6:14 PM
|Nope... just a wild guess.|| |