Any thoughts on why my rear tire feels mushy?

[matteblack]

I recently had a flat and replaced the tube, filling it with CO² on the road and then topping it a few times since then with a floor pump. I usually have to top my tires off every few rides (I ride about 95 psi) and did so this morning before my ride. I noticed that when I was descending Hunter Station Road in Reston going along at about 35, my rear tire felt like it had lost pressure and that I was riding on Jell-O. There was a slight wobble back there and I barely maintained control while rounding the corner at the bottom. The rest of the ride was uneventful, even when I exceeded 35 on a slight downhill straightaway on FC Parkway — there was no wobble at all.

I checked my pressure when I got home and it was still above 90. The wheel is true (well, true to the naked eye at least) and the hub seems to be functioning properly (e.g., I can’t move the tire back and forth).

Any suggestions? Nothing jumped out at me after a quick search using the google.

Topic

[dkel]

If it’s a well-worn rear tire, the tread be flatter in the the center because it’s the drive wheel. Maybe when you were cornering, you were moving back and forth across the thicker corner in the tread at the edge of the flattened area, giving you a wobble? That wouldn’t explain a squishy, flat tire feeling, though. CO2 escapes the tube faster than regular air does, but if you’ve topped up a few times since using the CO2, that probably isn’t relevant, especially if your pressure was still over 90 at the end of the ride. Worn sidewall, maybe?

[Judd]

Maybe it’s psychosomatic? I often have moments where a tire that just had a flat felt squishy like it was flatting again.

I’ve also experienced what Dkel describes when a tire is past its prime.

[drevil]

Hope it’s the tire and not what I suggest next: broken frame? I’ve broken several, and on a few of them, something felt not right, so I inspected the frames and found a crack.

[Sunyata]

It also could be that the bead on the tire did not completely seat. There is a line around (most?) all tires that should be equal distance away from the rim around the entire circumference of the wheel. Sometimes when you unseat the bead to change a tube, the tire does not re-seat exactly right. I have had that happen and it does make the tire feel wobbly and a little soft if it is on the rear.

[huskerdont]

Regarding the wobble, I’ve felt this a few times over the years, and it was either what Sunyata said (tire didn’t seat or came unseated) or I’ve worn a tire down to the threads, which seems to cause the tire to ride fishy at higher speeds.

[n18]

What’s the tire width/brand, and rim width or model? I would expect problems with slim tires on wider rims, some tires have specs on what inner rim width that it supports, but not wider.

[Crickey7]

Asphalt that hasn’t been properly compacted sometimes feels squishy under bike tires.

[matteblack]

Thanks for the replies, folks; lots of good info!

To provide more info, the tires are new (well, newish…they were replaced in December and have about 950 miles on them) and have plenty of tread on them. (Tires are Continental Grand Prix 4000s II 25 mm w/ 700×23/25 tubes; rims are Mavic Aksium Elite 700×25.)

I’ll take another look before my next ride to ensure the tire’s seated properly, but a quick look-see indicates it’s seated properly.

I don’t think the asphalt has anything to do with it as I’ve gone down that hill numerous times over the years and haven’t had this issue before. (Of course, I might not have traveled this same line so….)

Thanks again…hopefully ensuring it’s seated properly will do the trick. That’s not a good feeling to have when there’s no place to bail out at the bottom (well, no place soft anyway lol).

[FFX_Hinterlands]

Since no one mentioned it.. are your QRs tight and at the correct spot in the dropouts? Maybe the wheel isn’t centered between the chainstays.

Another thing could be a twisted tube. I got a flat once and was shocked to find a full twist in my tube.

[matteblack]

So…I’m going to go with a tube issue (twisted or pinched or ???) or an unseated tire. I gave it a closer inspection and nothing seemed amiss, but went ahead and deflated the tube. I then reinflated it (with the floor pump) and took it out for a spin this afternoon. It felt fine the entire ride and even when I hit mid-30s on a few descents (although I didn’t hit the same downhill due to time constraints).

Still scratching my head on this one, but since it’s gone away, I’m going to chalk it up to an inflation/tire bead issue.

Thanks for playing!

[bentbike33]

It could have been just a chance oscillation in your bike. Bike wheels are inherently unbalanced due to the valve stem and the rim weld (not to mention accessories like reflectors, or inconsistent thicknesses in tires and tubes). You can see this by cranking up the rear wheel to high speed when the bike is on the repair stand. Maybe on that particular stretch the front and back wheel imbalances synchronized in such a way as to make your bike feel squirrelly. It may or may not ever happen again.

[n18]

After installing a new tube, use a flash light to see if it’s twisted or pinched before installing the final side of the tire. Indoor lights are not enough, you have to use a flash light. I spotted both twisted and pinched tubes that way, otherwise they looked normal to me.

[dkel]

@n18 187470 wrote:

After installing a new tube, use a flash light to see if it’s twisted or pinched before installing the final side of the tire. Indoor lights are not enough, you have to use a flash light. I spotted both twisted and pinched tubes that way, otherwise they looked normal to me.

Supposedly, a partial inflate, up to 40 psi or so, and then a complete deflate will untwist a twisted tube. After that exercise, reinflate to pressure, and ride on. I do that when changing a tire and I’m not in a hurry, but I don’t know whether it’s really a thing or not; I don’t even remember where I got the idea (Sheldon? Zinn?).

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