Pressure in Conti4000 vs Conti5000

Discuss light weight issues concerning road bikes & parts.
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by Baal

This my first post here and I wonder if more knowledgeable people can advise me. I have two bikes with similar carbon clincher wheels (same outer and inner dimensions). One bike has the new Conti5000 GP tires in 28 mm. With tubes they measure 28.8 mm. The other has Conti4000 GP tires, nominally 25 mm, but they actually measure 28.4 mm, again with tubes. Does this mean I can run them at the same pressure, somewhat lower than for actual 25 mm tires? Or should I still ride the "25s" at a higher pressure? Roads where I live are pretty rough. Hopefully I've provided enough info for people to let me know.

Thanks in advance.

by Weenie

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by TobinHatesYou

Inflate to pressures that make sense for measured volume.

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by Baal

That's what I figured too but thank you for confirmation!

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by Hexsense

Normally height is not something to look for. But just in case it's noticeably different.
Like 23c on 21mm internal width rim became 27.3mm wide but not tall at all, in this case you may need to overinflate a little bit from what the width suggest, to prevent pinch flat.

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by pdlpsher1

How new are the GP5Ks? New tires will stretch a bit so it's best to compare tire width after the new tires have had a chance to stretch. In my experience the GP5K 28 non-TL is about 1mm wider than the GP4K 25. You can drop the pressure on the GP5Ks just a tad to give the same 'spring rate' as your GP4Ks. Also when it comes to tire width measurement it's best to take 5-6 measurements and take the average. Tires are incredibly non-uniform when it comes to widths.

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