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Conti GP5000 28mm stay true size?

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Conti GP5000 28mm stay true size?

Old 08-02-19, 06:28 PM
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twocicle
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Conti GP5000 28mm stay true size?

As it is widely known in this forum, the GP4000 28mm tire size bloated up much bigger than 28mm. I have the GP4000 in various sizes for different bikes and found only the 28mm to have the bloating scenario. Bigger = more volume, so in general a nice feature. However...

On our road tandem the rims are just over 19mm interior width (the width that counts the most). On these rims, the GP4000 28mm tires measure closer to 29.8mm on install and after a year or so (very long wearing) more like 34mm. We run them at only 93-95psi due to all the air volume there is - higher psi not needed. I finally had to take off the front tire because it ran out of room under the fork crown - funny you might think that as a tire wears it would have more room but no, this bloated more than it wore down. We have a supply of new GP4000 28mm tires, so I mounted new treads front and rear, long before the old rubber had given up its life. Now there is a good 3mm clearance under the fork crown again, at least for the time being.

So the question... does the new GP5000 28mm tire maintain close to its advertised size, or bloat / grow like the 4000 does?

Last edited by twocicle; 09-16-19 at 12:20 PM.
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Old 08-02-19, 06:47 PM
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And in addition: since the GP5000 is also available in 32 mm, does anyone have experience with the actual size of the 32 mounted on a wider rim?
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Old 08-03-19, 11:21 AM
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From: https://www.bentrideronline.com/mess...d.php?t=143342

So here's some width measurements. I'm using Easton rims that are 24mm wide on the outside and 19.5mm on the inside. I pumped all tires up to 100psi.

The 25c GP4000sll is 1.170in (29.7mm)
The 28c GP4000sll is 1.330in (33.7mm)
The 28c GP5000 is 1.150in (29.2mm)
The author states that the 4KIIs are much older than the 5K tire, so the 5K tire might grow to 30mm.
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Old 08-04-19, 09:31 AM
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Originally Posted by Carbonfiberboy View Post
From: https://www.bentrideronline.com/mess...d.php?t=143342



The author states that the 4KIIs are much older than the 5K tire, so the 5K tire might grow to 30mm.
Perfect. Good find, thanks! I never found the 25mm 4000 to grow much beyond the initial size, so strange he measured 29.7mm with his. Regardless, my experience with the 28mm is about the same... near 34mm actual width after the tire is mounted for some time.

For the next few years guessing we will be using 28mm 5000 on the front (for better fork fit) and 4000 on the rear (stash of new old stock). These 4000 might actually last for the next decade as we are splitting rides between road and mtb tandems.

Last edited by twocicle; 08-04-19 at 09:39 AM.
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Old 08-05-19, 05:15 AM
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Bicycle rolling resistance has an ongoing long-term test. You can see here that they do get a bit wider with time, but the test is not complete yet.

https://www.bicyclerollingresistance...endurance-test
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Old 08-06-19, 08:00 PM
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Why not switch to 25mm if all the 28ís puff up too much? Iím sure another home could be found for your stash of 28ís.
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Old 08-24-19, 11:21 PM
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The GP 5000 28mm went on our rims measuring 28.5mm right at install. After the 1st ride it was up to 29.5mm and has stayed under 30mm for a week now. Seeing really good clearance at the fork arch, so these have solved the excessive size / fitment issue on the front. We will keep using the GP 4000 28mm for the rear until they are all gone... maybe in 5 years

Originally Posted by ThermionicScott View Post
Why not switch to 25mm if all the 28’s puff up too much? I’m sure another home could be found for your stash of 28’s.
Silly rabbit. 25mm tires are for kids. Really though, we used to use 25mm pumped to 118psi, until super quality race tires finally became available in larger sizes like the 28mm which with wider rims only need 93-95psi for our team weight (<275lbs loaded for day rides only). 25mm tires just do not give the better ride quality and longer wear that a larger tire does (we used to burn out the 25mm centers fairly quickly).
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Old 08-25-19, 01:00 AM
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Originally Posted by twocicle View Post
Silly rabbit. 25mm tires are for kids. Really though, we used to use 25mm pumped to 118psi, until super quality race tires finally became available in larger sizes like the 28mm which with wider rims only need 93-95psi for our team weight (<275lbs loaded for day rides only). 25mm tires just do not give the better ride quality and longer wear that a larger tire does (we used to burn out the 25mm centers fairly quickly).
You're talking to a guy who rides 38mm at minimum anymore. Silly rabbit!
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Old 08-28-19, 05:54 PM
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Originally Posted by ThermionicScott View Post
You're talking to a guy who rides 38mm at minimum anymore. Silly rabbit!
I am not familiar with the bikes listed in your bio. Any of them tandems?
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Old 08-28-19, 11:10 PM
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Originally Posted by twocicle View Post
I am not familiar with the bikes listed in your bio. Any of them tandems?
Nope! But I can't think of a reason to use 28s on a tandem even if I had one.
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Old 09-13-19, 07:56 AM
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Mine are true to size.

for example:
Continental’s Sizing on 22mm ID rims
4Season 28mm: 27mm
GP4000 28mm: 31mm
GP5000 32mm: 33mm
4Season 32mm: 35mm.

Rim size does make a difference. I have some GP5000 28mms on 19c rims, and they are right at 28mm as I recall. I can't put the 28mm GP4000 on that bike, but the GP5000 works fine.
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