How do I avoid pinch flats? - Update
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How do I avoid pinch flats? - Update
Postby hitchhiker » Tue Mar 15, 2011 7:44 pm
I'm new to commuting and have been getting a lot of pinch flats (5 in 3 weeks). I ride 26km each way and the roads can be bumpy, generally the punctures occur just after I've hit a large bump. The punctures are always in the rear.
I'm riding a Repco Superlite with a rack and rack bag. I don't carry much weight (change of clothes) and I weigh 75 kg.
I'm using 700x23 Continental GP4000 tyres which I suspect is my problem. I have some 700x25 Specialised All condition pro tyres although I'm not sure if they would make much difference.
Other then avoid the bumps, would the best remedy be a larger tyre?
If so what size? and can I just fit one to the rear and leave the 23 on the front?
Thanks
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How do I avoid pinch flats?
Postby sogood » Tue Mar 15, 2011 7:50 pm
RK wrote:And that is Wikipedia - I can write my own definition.
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Re: How do I avoid pinch flats?
Postby hitchhiker » Tue Mar 15, 2011 8:03 pm
That's been my strategy so far, check the tyre pressure each morning and stand up over the bumps. Unfortunately I invariably still manage to hit some bumps while seated.
I'm hoping there's a more robust solution for the bumps I fail to avoid
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Re: How do I avoid pinch flats?
Postby lethoso » Tue Mar 15, 2011 10:12 pm
Although the obvious solution of not hitting the big bumps would do wonders for your comfort as well as puncture rate
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Re: How do I avoid pinch flats?
Postby wookie661 » Tue Mar 15, 2011 10:17 pm
saying that ive only dealt with 25 tyres or wider and the max pressure ive ever seen is 85.
but yes avoid the bumps, stand up, or get a bike with suspension.
maybe wider tyres.
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Re: How do I avoid pinch flats?
Postby sogood » Tue Mar 15, 2011 10:20 pm
The accepted reference on this issue is late Sheldon Brown.wookie661 wrote:im not too sure about 110psi, usually on the side wall it will say what the max pressure is.
http://www.sheldonbrown.com/tires.html
http://www.sheldonbrown.com/flats.html
RK wrote:And that is Wikipedia - I can write my own definition.
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Re: How do I avoid pinch flats?
Postby trailgumby » Tue Mar 15, 2011 10:24 pm
Not riding on footpaths at speed will help (my usual culprits - still carrying too much speed coming off the roadway to get away from grumpy traffic)
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Re: How do I avoid pinch flats?
Postby Cruiserman » Tue Mar 15, 2011 10:49 pm
1986 Spokesman Model 11 Racing - Campag Nuvo Record - Stronglight - Shimano 600
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Re: How do I avoid pinch flats?
Postby mikesbytes » Tue Mar 15, 2011 11:20 pm
I'm 75kg and I run 120 rear, 110 front. About 10 psi more than Seldonbrown. Check the link that sogood has posted and set your tyres accordingly.
And don't get hung up on the rating on the sidewall, that has been determined by lawyers, the safe legal limit where my a isn't going to be sued if the tyre comes off the rim
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Re: How do I avoid pinch flats?
Postby hitchhiker » Wed Mar 16, 2011 6:59 pm
I cut my losses today and rode the mountain bike with slicks. No punctures and although it felt slower, the travel times were about the same.
I still prefer to ride the Superlite so I'll follow the tyre pressure advice to see if that solves the problem
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Re: How do I avoid pinch flats?
Postby Mugglechops » Wed Mar 16, 2011 7:27 pm
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How do I avoid pinch flats?
Postby Comedian » Wed Mar 16, 2011 7:57 pm
Gawd! The 28mm vittoria randonneurs I run on my hybrid run at 65 front and 75 rearMugglechops wrote:I run 28mm tyres at 120kgs and don't get pinch flats. No idea what pressure I just pump them up till they are hard.
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Re: How do I avoid pinch flats?
Postby Mugglechops » Wed Mar 16, 2011 9:25 pm
Comedian wrote:Gawd! The 28mm vittoria randonneurs I run on my hybrid run at 65 front and 75 rearMugglechops wrote:I run 28mm tyres at 120kgs and don't get pinch flats. No idea what pressure I just pump them up till they are hard.
I probably should have written that as"I run 28mm tyres and weigh 120kgs...."
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Re: How do I avoid pinch flats?
Postby waynohh » Thu Mar 17, 2011 12:54 pm
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Re: How do I avoid pinch flats?
Postby Jason22 » Fri Mar 18, 2011 8:26 am
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Re: How do I avoid pinch flats?
Postby hitchhiker » Sat Mar 19, 2011 6:43 pm
After my last flat a couple of days ago, I replaced the tube and rode home. Today was the first chance I've had to look at the bike. I was pumping up the rear tyre, at about 110 psi there was a loud bang.
Upon inspection I found the tyre was ripped and a decent hole in the tube underneath. The rip wasn't there when I replaced the tube after the flat a couple of days ago. This is a new tyre that's done less than 300km.
Tyres shouldn't do this should they?
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Re: How do I avoid pinch flats? - Update
Postby sogood » Sat Mar 19, 2011 6:53 pm
RK wrote:And that is Wikipedia - I can write my own definition.
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Re: How do I avoid pinch flats? - Update
Postby ZepinAtor » Sat Mar 19, 2011 7:21 pm
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Re: How do I avoid pinch flats? - Update
Postby Hamster » Thu Mar 24, 2011 12:31 pm
Since changing the rimtape there has been no flats (touch wood) and none at all due to penetrations or pinching.
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Re: How do I avoid pinch flats? - Update
Postby Xplora » Mon Jun 06, 2011 9:18 am
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Re: How do I avoid pinch flats? - Update
Postby trailgumby » Mon Jun 06, 2011 1:01 pm
The only thing that will help will be avoiding the hitting of square-edged bumps, and / or more tyre pressure. @82kgs riding weight + panniers, I run about 95psi which seems a good balance between comfort and pinchflat avoidance.
That ruptured sidewall has been caused by striking something sharp that's cut the casing.
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Re: How do I avoid pinch flats? - Update
Postby goneriding » Mon Jun 06, 2011 1:42 pm
One piece of advice is to do a deglass and check of the tyres once a week. You'll be unpleasantly surprised as to just how much glass and bits of metal the tyres pickup in a week.
Another is to cut 2 -3 pieces of tyre from an old tyre to use as liner, between the tube and the tyre wall, for tyres that get this kind of cut. It will keep you going until you can get a new tyre.
Do a search here for tyre recommendations for commuting as it has been discussed at some length!
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Re: How do I avoid pinch flats? - Update
Postby find_bruce » Tue Jun 07, 2011 12:23 pm
The limp home trick someone taught me years ago is that any polymer bank note between the tube & tyre will stop the tube squeezing out through the hole in the tyre & its enough for you to get home on.goneriding wrote:cut 2 -3 pieces of tyre from an old tyre to use as liner
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Re: How do I avoid pinch flats? - Update
Postby goneriding » Tue Jun 07, 2011 12:48 pm
That's great, unless you need to stop for coffee. Then what do you do!find_bruce wrote: The limp home trick someone taught me years ago is that any polymer bank note between the tube & tyre will stop the tube squeezing out through the hole in the tyre & its enough for you to get home on.
Whilst a bank note will stop the tube coming out it won't stop anything sharp getting through whereas an old piece of tyre is far more likely to stop the sharp nasties.
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Re: How do I avoid pinch flats? - Update
Postby Kenzo » Tue Jun 07, 2011 12:52 pm
Get change...goneriding wrote:That's great, unless you need to stop for coffee. Then what do you do!
It was a 'limp home trick'.... not a be-all end-all.goneriding wrote:Whilst a bank note will stop the tube coming out it won't stop anything sharp getting through whereas an old piece of tyre is far more likely to stop the sharp nasties.
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