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I have a Trek FX 7.7 and the rear tire is rubbing the frame with 100psi in the tire. Stops rubbing at 96psi. I have 26mm Continental Grand Prix 4 Season tires. The original tires were Bonetrager 24mm(I think). I would not think 2mm would make a difference??? Any suggestions, am I missing something simple and stupid??

Update to the information I posted, new tires are 28mm (went to my receipt, sidewall hard to read), previous tires 25mm. The rub is on the face of the tire, the picture shows with 96psi and not rubbing. One of the comments I received said that specs for my bike said that 25mm tires would fit, I went to Trek website before I posted this question, and could not find that information. I did not realize that going up in width would effect the diameter as well. Sounds like I need to get some new tires.

For some of the other responses I got, 1. Yes the wheel is very slightly out of true, 2. No bulges or anything in the tire, and 3. I carefully checked to make sure the wheel was mounted correctly and straight.

To everybody that responded - THANK YOU!!!

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    2mm can make a difference (especially since width measurements are not well standardized), but so can the thickness of the tread. However, do make sure that the axle is properly seated in the dropouts.
    – Daniel R Hicks
    Commented Apr 5, 2020 at 14:09
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    That model comes in carbon and Al versions, and the carbon frame specs claim that 25mm tires fit. It's Is the top of the tire that is rubbing or the side? Could it be rubbing the inside of the brake caliper and not actually the frame?
    – bradly
    Commented Apr 5, 2020 at 16:08
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    Stop using that tyre if you don't want to damage the frame. Even if it doesn't rub at 96psi the tyre changes shape dynamically and it will rub at times.
    – Carel
    Commented Apr 5, 2020 at 18:52
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    I suspect a faulty tire. Have you checked the tire for a bulge. A normal tire should not measurably change size over 4PSI.
    – mattnz
    Commented Apr 5, 2020 at 19:27
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    Where precisely is it rubbing??
    – Daniel R Hicks
    Commented Apr 6, 2020 at 17:10

3 Answers 3

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Three steps: is it rubbing the entire rotation? If not true your wheel. Is it rubbing all the way round but just on one side, fix the dish of your wheel. If it is neither of the above, you need a smaller tyre.

All tyres will expand to a point as you increase the pressure. They will expand less and less as the pressure increases up until the point that they either explode or you destroy the rim.

There is also the question about why you are using more pressure?. Pressures much over 100psi are only faster as the road gets much smoother (dependant on weight of rider and tyre width), that's why they still use pressures towards 200psi on the track, but road pressures have been declining for years. It takes less energy for a tyre to deform than it does to push the entire bicycle up as it encounters a bump in the road.

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  • I am using the tire pressure recommended by the shop where I purchased the bike - actually they recommended 110psi rear and 100psi front. I have lowered to 100 rear and 90 front. I am not a racer, I do put 2500-3000 miles on per season.
    – Gary E
    Commented Apr 6, 2020 at 16:53
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    Those pressures are reasonable for larger human beings.
    – MaplePanda
    Commented Mar 13, 2021 at 3:02
  • 6.9bar in 28mm tires seems very excessive to me. As a 67kg person I use 5bar. I used almost 7bar for 23mm tires.
    – Michael
    Commented Mar 13, 2021 at 8:22
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    @Michael Someone in the 80-90kg range would use those higher pressures. 67kg ain’t much.
    – MaplePanda
    Commented Mar 13, 2021 at 9:24
  • I ride 28mm tires, 110 kg weight, 7 bar. Someone might validly question why I use 28mm and not 32mm tires. The reason is I standardized on 28mm tires at the time my weight was much lower. If I was picking a tire width standard right now, I'd pick 32mm given high-performance slick tires are available as 32mm width tires.
    – juhist
    Commented Mar 13, 2021 at 12:33
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Then it's not too much pressure.

That pic does seem to show the tyre over to one side slightly.

Perhaps dishing the wheel to the centre will fix it.

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Update to the information I posted, new tires are 28mm (went to my receipt, sidewall hard to read), previous tires 25mm. [snip] One of the comments I received said that specs for my bike said that 25mm tires would fit

You're the victim of low tire clearance!

Good bicycles have ample tire clearance so you can run tires without fender, tires with fender, narrow tires, wide tires, slick tires, patterned tires, studded tires, etc. And no matter what configuration you use, there's ample clearance between the tire and the fork/frame/fender/brake so you can ride your bike anywhere, including mud.

Unfortunately, it appears your frame is only designed for at most 25mm slick tires, and even then riding on mud can deposit mud on the tire to scrape on the frame, fork and brakes. That's very typical of road bikes: they often have too little tire clearance.

There's no simple way of fixing this apart from changing your frame, your fork and your brakes (the brakes seem to be sidepulls with very low reach, so they won't fit on a frame or fork with ample tire clearance). I'd recommend V brakes or cantilever brakes, or better yet, disc brakes.

Because frame and fork swap is the most difficult replacement job in a bike, the best way to approach this is to sell the obsolete bike if someone really really wants to have a bike that can't take reasonable tires (most probably you won't find a long line of prospective buyers) and buy a new bike. When buying the new bike, avoid bikes that are labeled as "road" bikes and prefer bikes that are labeled as "cyclocross", "gravel" or "touring" bikes.

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