aliasfox

Hi everyone,

Took one of my bikes out for a nice long ride after work yesterday (one of the benefits of working east coast hours on the west coast - have to get up by 5am, but done around 2:30pm), and was having quite an enjoyable ride when I spotted some glass shards right in front of the bike. No time to avoid, so just rode over it. Nothing from the front wheel, but I heard my rear wheel interacting with something as it went through the glass. Fearing the worst, I pulled over a few hundred feet down the road, and slowly rotated each wheel to make sure there wasn't anything sharp still embedded in the tread.

Found my rear tire looking like this.



I'm actually surprised that the cuts didn't puncture the carcass. The tube was still holding air, and there wasn't an obvious bubble around the cuts, so there wasn't really anything I could do. The next part of the ride was supposed to be a -7% descent (for those on the SF Peninsula, was heading down Edgewood Rd from Cañada), so was definitely concerned about tire failure. Was able to complete the remaining ~20mi of my ride and get back to the garage, where I took the above picture. Checked this morning, and the tube was still holding air.

So the question is: Is the tire safe to ride on, or would you preemptively change this out? It's a Continental GP5000 25mm, with just shy of 800mi on it, so without the damage, should be about halfway (or less) into its lifespan.

SoSmellyAir

How does the tire look if you inflate it to the max stated pressure?

urbanknight

Sidewall cuts are much more concerning to me than the tread. If you don't see a bulge when fully inflated (the above suggestion to test it at max pressure is a great one), it's probably fine.

Iride01 

Where do you ride that it'd be unsafe if it flatted? I've had the the sidewall of a tire get a six inch rip in it and all it I had to do was slow down to a stop from the 15 - 20 mph I was probably doing at the time.

If the area around the cuts hold the correct shape as the rest of the tire has when the tire is inflated, then I wouldn't be worried about a flat. But if the rides upcoming soon are important to me, such as a charity ride or other organized ride, I'd change it out. If you ride in a big group with others, you also might want to change it out. You'll catch all kinds of heck if they find out you slowed them up because you flatted with tires that already had a defect.

But for solo riding I'd use it till it flats.

TiHabanero

I have had similar cuts many times. Simply boot it from the inside using a traditional glue patch and it will add reinforcement to the area. Should be able to run the tire to a natural end.

Eyes Roll

I second this ^^^. Sticking a tube patch on the inside of the tire at the location of the cut outside will work.

Or, if you have an old worn-out tire available, you can cut a tire piece to a size 5 to 6 times larger than the outside cuts and slide it between the tube and the tire. Using electrical tape can help keep the small old tire piece in place.

*** Plus, buy or order a new spare tire and keep it readily available as a backup plan, if the above ^^^ solution doesn't work.

aliasfox

So I inflated to 105psi (as indicated by my Serfas pump), and got this. For reference, I usually ride at around 90psi indicated (yeah, carrying around about a dozen kilos more than I should).




the tread lifted up more, but the tire otherwise held its shape. I actually do have a GP5000 28mm as a spare. No traditional patches handy - would a glueless patch work well enough for reinforcing the tire from the inside?

I plan on taking the tire off on Sunday and seeing how the carcass looks from the inside. If it doesn’t look torn from the inside, I’ll probably put it back on (with a glueless patch reinforcement).

As for where I was riding, I was about to go down a ~1.5mi 7% descent. Minimal traffic going downhill, but a fair bit of traffic coming up the hill to get onto I-280, so not as much wiggle room if something happened. The descent is fairly straight, with a few sweepers, and Strava indicates that I usually top out around 45-50mph on those (though I’m fairly sure it’s optimistic). I agree, a rear tire flat at 15mph isn’t much to be concerned about, I don’t know about 3x that speed though.

Eyes Roll

If it were me, I wouldn't ride inflating the tire above 80 psi in the same state, unless I strengthened the area in the manner stated in the above post(s). If you strengthened the area as stated, then I wouldn't worry about the external appearance of the tire, until the next flat occurs.

Then what is all this fuss about? One new GP5000 costs no more than one fill-up of Ford Focus gas tank.

A patch is a patch. It will work. Something is better than nothing. 'Rema Tip Top' tube patches work the best, even for patching tires from the inside.

rsbob 

I would patch the inside and superglue the deflated outside cut together and take it for a few spins.

Eyes Roll

I wouldn't put superglue on the outside, which would cause the tire to become more hardened and break even further, if it hits rocks, stones, small potholes, and uneven substances on the road. Just leave it like that on the outside so the tire can remain flexible. A lower air pressure/PSI is also suggested until the cut area is reinforced on the inside to ensure tire flexibility and prevent it from breaking further.

jpescatore

Asssuming it did not penetrate the inner lining, If that happened to me on a relatively new tire, I'd fill the gap (while inflated) with Shoe Goo and let it dry. I've done that a few times when got big gashes in tires with just a few hundred or fewer miles on them.

If the wear indicators were getting to the point where the tire was 80% gone anyway, I replace the tire. Saving 20% of the cost of a tire isn't worth it to me - I save roadside repair for the unavoidable flats.

aliasfox

It’s not really about money, as much as it’s about waste. According to Strava, my GP4000 S2s lasted about 2,500 and 1,800 miles before sidewall tears did them in (this was on the other bike). That was cut and dry - broken threads, tube starting to peak out. Here, if it’s reasonably safe, I’d at least like to see the wear dimples fade away!

To be honest, this bike could use a new set of wheels anyway - rims are concave to the touch, and its second freehub is starting to go. I’ll probably pull the trigger on some Campy Zondas next month (another thread on that incoming). In the meantime, I’ll likely patch the tire tomorrow and keep this bike on some shallower routes. Failure on a gentle 20mph descent is probably less scary than a true bombing run.

In the meantime, gonna prep the other bike for departure today, which means checking that pesky R8000 crank for issues now…

Eyes Roll

With a tube patch inside, you should be able to get a few months of ride with that tire.

njkayaker

eduskator

Two concerns : there are two perpendicular cuts (it could rip) and it could potentially blowout at some point during its life (that may result into serious harm depending on your speed). If you want to take the risk, you may want to fill the puncture with glue, shoe goo or something like that.

aliasfox

I find it interesting - most of the comments suggest that they would ride on the tire, but most of the poll responses say to toss it.

Didn't get a chance to take the tire off this weekend- busy Saturday accentuated by a 38mi, 3200ft ride, and getting this year's Covid booster in the evening. I was hoping I'd be able to putter about and do some maintenance on Sunday, but the vax definitely knocked me on my a... butt. Should have time to take the tire off today, so we'll see if that gives more info.

Given the mixed opinions, it sounds like it might just be best to save this as a trainer tire.

Iride01 

I seldom click on the polls. There are too many things to consider to simply boil it down to one decision that is proper for everyone since many of us don't ride with the same intensity in the same terrain and other environmental or traffic conditions.

And as I said in my original reply, it depends a lot on what the next rides will be.

But I've never found a flat or blowout to make the bike handling unsafe. But I don't ride down mountains with 180° switchbacks and sheer cliffs on one side. That's probably the one situation that would concern me for safety reasons.

aliasfox

So I was finally able to make it to the garage and get the tire off today. A few observations:
- since pumping the tire to 105 PSI over three days ago, the tire is still firm, with no noticeable bulging
- taking the tire off the wheel, I can see that the tread was cut all the way down to the threads (see pic), but
- flipping the tire inside out, there doesn’t appear to be any visible damage to the threads from the inside (see other pic)





Given that the tire seems structurally ok at the moment, I reinforced it from the inside with a Specialized glueless patch and put it back on the wheel.

I figure I’ll keep her to shallower, less technical routes for now to reduce failure risk, and leave the heroic climbing and glorious descending to the Lynskey. As I’ve called out in my other thread, this bike is due to get new wheels soon anyway (Zondas or Ksyrium S? Chime in on the other thread!). Once the new wheels come in, I’ll re-evaluate. If the newer, wider rims can fit the 28mm backup tire, then maybe this one gets retired, or demoted to backup duty.

aliasfox

If you like vertical, then some of the mountains around here are exactly that. Page Mill Rd has a handful of switchbacks at greater than -10%, and Old La Honda has so many tight turns that it’s actually unpleasant to descend in my opinion. That said, I would actually be more scared of some fast sweepers where one would normally enter at over 25-30mph - you know the kind where you might normally have a big grin on.

eduskator

It's still and will remain a weak spot through all its lifespan. Be careful

tFUnK

Patch from the inside and keep riding it, but also keep an eye on it in case it develops a bulge. If it were me I would replace it as soon as a bulge forms.

jadmt

I use Velox rim tape for patches the stuff is tough and stays in place. I carry a little roll of it with my patch kit

Jughed

Not to be overly dramatic...

But tires are cheaper than my heath insurance deductibles. WAAAAY cheaper. Also cheaper than fixing post crash broken parts on the bike

aliasfox

True, but I'm not overly concerned about losing control of the bike if the rear flats, provided I don't take her on my more 'dramatic' routes - ie, this bike's only going on shallow, straight descents for now. If it were a front tire, it would've come off as soon as I got home.

Eyes Roll

It is always a good idea to save and keep in hand an old worn-out tire that you replaced with a new tire in cases such as this. You can cut an appropriate size of old worn-out tire (which would be sufficiently thinner, and also stronger) to slide it in between the tube and the tire, and fasten it with a tape. You basically have a tire inside protecting the tube if a stone or glass penetrates the outer tire from the outside. A patch will work, but a piece of old tire would be stronger than the patch, IMO.

As a bike rider, there are no hard and fast rules. You use common sense and you improvise with your ideas.